Article

Resistance to rice sheath blight (Rhizoctonia solani Kühn) [(teleomorph: Thanatephorus cucumeris (A.B. Frank) Donk.] disease: Current status and perspectives

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Abstract

Sheath blight (ShB) disease, caused by Rhizoctonia solani, is an economically important rice disease worldwide, especially in intensive production systems. Several studies have been conducted to identify sources for ShB resistance in different species of rice, including local accessions and landraces. To date, none of the genotypes screened are immune to ShB, although variation in levels of resistance have been reported. Several quantitative trait loci (QTL) for ShB resistance have been identified using mapping populations derived from indica or japonica rice. A total of 33 QTL associated with ShB resistance located on all 12 rice chromosomes have been reported, with ten of these co-localizing with QTL for morphological attributes, especially plant height, or for heading date. Sixteen QTL, from the same or differing genetic backgrounds, have been mapped at least twice. Of these, nine QTL were independent of morphological traits and heading date. We hypothesize that two main, distinct, mechanisms contribute to ShB resistance: physiological resistance and disease escape. Strategies to improve our understanding of the genetics of resistance to ShB are discussed. KeywordsRice (Oryza spp.)–QTL– Rhizoctonia solani –Screening–Sheath blight

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... To achieve the goal with SAM, it is important to understand the resistance mechanisms to ShR, to have a detailed map of the selected genes and the cloning of them. There are two common problems with SAM technic using resistant QTL to ShR, (i) the identified DNA markers may grandes colecciones de marcadores SSR ubicados tanto en la porción no codificada como expresada del genoma del arroz (Mohler y Singrun, 2004;Srinivasachary et al., 2011). ...
... In this same sense, the absence of the rice complete resistance to R. solani has been determined (Pan et al., 1999, Mew et al., 2004, Jia et al., 2012, considering that the rice resistance to the fungus is multigenic, therefore, it is difficult to evaluate the individual effect of this genes (Che et al., 2003). In addition, Srinivasachary et al. (2011) proposed that there are two different mechanisms improving resistance to ShR; the first mechanism is the physiological resistance, which is independent of the morphological characteristics, and the second mechanism is attributed to morphological characteristics of the plant, which allow it to avoid the disease, such as the height or date of the emission of the panicle. In the present work the physiological resistance was determined by artificial inoculations of the plants in the same growth stage (R4). ...
... En este mismo sentido, se ha determinado la ausencia de resistencia completa en arroz a R. solani (Pan et al., 1999;Mew et al., 2004;Jia et al., 2012), considerándose que la resistencia en arroz al hongo es multigénica, siendo difícil evaluar el efecto individual de los genes que confieren esta resistencia (Che et al., 2003). Además, Srinivasachary et al. (2011) señalaron como hipótesis que existen dos mecanismos principales y distintos que contribuyen a la resistencia a la PDV, una es la resistencia fisiológica, que es independiente de los rasgos morfológicos y la segunda es el escape de la enfermedad atribuida a caracteres morfológicos, especialmente la altura de la planta, o la fecha de emisión de panícula. En el presente trabajo se establece la resistencia fisiológica por haberse hecho inoculaciones artificiales a las plantas en la misma etapa de crecimiento (R4). ...
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In order to investigate the association of resistance to Rhizoctonia solani, that cause sheath rot of rice (ShR), with microsatellite markers SSR. (Simple Sequence Repeats), two crosses were made between commercial rice cultivars (Palmar x Fonaiap 1 and Jefferson x Fonaiap 2000). The plants were inoculated at the beginning of em ergence of the panicle and then placed in a humid chamber for a week. Then, the percentage of the area affected by the disease was determined (0 = no lesion, up to 9 = 100% affected area) and the plants were grouped according to the evaluation scale. SSR markers were evaluated once the extraction DNA from leaves and amplifying their fragments using the polymerase chain reaction (PCR) and visualized the PCR products by electrophoresis in 3% agarose gels. The method of composite interval mapping was used to detect QTL conferring resistance to ShB, decreeing the presence of QTL with threshold LOD> 2.4. In the progeny from crosses Palmar x Fonaiap 1 were detected 3 QTLs located on chromosomes 1, 4 and 12 flanked by the markers RM 572 and RM 449, RM 273 and RM 3471, RM 3472 and RM 309 respectively. No QTLs were detected in the progeny crosses between Jefferson x F 2000. The QTLs found in the present work, are a valuable contribution to the study of resistance in rice to R. solani. Key words: Oryza sativa, sheath rot, QTL, varietal resistance.
... Complete resistance has not been identified yet in any wild or cultivated rice accession (Srinivasachary et al. 2010;Zeng et al. 2015). This is probably because rice cultivars have an extensive variation of susceptibility levels to ShB, which appears to be controlled by many minor genes (Pinson et al. 2005;Srinivasachary et al. 2010;Zou et al. 2000). ...
... Complete resistance has not been identified yet in any wild or cultivated rice accession (Srinivasachary et al. 2010;Zeng et al. 2015). This is probably because rice cultivars have an extensive variation of susceptibility levels to ShB, which appears to be controlled by many minor genes (Pinson et al. 2005;Srinivasachary et al. 2010;Zou et al. 2000). Although the molecular mechanism underlying the host-pathogen interaction remains unclear (Jia et al. 2012;Li et al. 1995;Pinson et al. 2005;Sharma and Teng 1990;Srinivasachary et al. 2010;Zeng et al. 2015;Zou et al. 2000), some of the pathways associated with resistance to necrotrophic fungi appear to involve the suppression of abscisic acid signaling and the regulation of reactive oxygen species (ROS) (Asselbergh et al. 2007). ...
... This is probably because rice cultivars have an extensive variation of susceptibility levels to ShB, which appears to be controlled by many minor genes (Pinson et al. 2005;Srinivasachary et al. 2010;Zou et al. 2000). Although the molecular mechanism underlying the host-pathogen interaction remains unclear (Jia et al. 2012;Li et al. 1995;Pinson et al. 2005;Sharma and Teng 1990;Srinivasachary et al. 2010;Zeng et al. 2015;Zou et al. 2000), some of the pathways associated with resistance to necrotrophic fungi appear to involve the suppression of abscisic acid signaling and the regulation of reactive oxygen species (ROS) (Asselbergh et al. 2007). ROS, in particular, seems to have a dual function because it triggers plant basal defense responses with biotrophic and hemibiotrophic pathogens while enhancing virulence with necrotrophs. ...
Article
Rice sheath blight, caused by the necrotrophic fungus Rhizoctonia solani Kühn, continues to be an important and challenging rice disease worldwide. Here, we used genome-wide association studies over a high-density rice array to facilitate the identification of potential novel genes and quantitative trait loci related to sheath blight resistance. We identified multiple regions that significantly associated with independent disease components in chromosomes 1, 4, and 11 under controlled condition. In particular, we investigated qLN11 28 , a quantitative trait locus enriched with defense-related genes that reduce disease lesions in a near-isogenic line. RNA profiling of the line carrying qLN11 28 showed a number of differentially expressed genes related to the reactive oxygen species (ROS)-redox pathway. Histochemical staining revealed less ROS accumulation on the resistant line, suggesting efficient ROS deregulation that delays pathogen colonization. The detection of genomic regions controlling multiple mechanisms of resistance to sheath blight will provide tools to design effective breeding interventions in rice.
... Also, the finding for resistance sources of rice genotypes is low. Partial resistance may provide a road to reduce epidemics to given the low level of it's especially of the sheath blight fungus (Srinivasachary et al., 2011). Before and during infection, the sheath blight pathogen R. solani was examined differently in tolerant and susceptible rice genotypes (Basu et al., 2016). ...
... The likelihood of finding such a resistance source of rice genotypes is also low. Given the low prevalence of the sheath blight fungus, partial resistance may provide a path to reducing epidemics (Srinivasachary et al., 2011). In a greenhouse, the artificially inoculated rice plants (SK101 and E. Yasmine) with 17 R. solani isolates exhibited typical lesions of sheath blight. ...
... Those genotypes identified as having moderate to high levels of resistance should be used as resistance donors in breeding efforts. Tetep, Jasmine 85, and Teqing from O. sativa germplasm have sources of resistance for sheath blight (Srinivasachary et al., 2011). ...
... Producers apply foliar fungicides to control ShB disease, but tolerant fungal isolates have been discovered (Galam et al. 2021). Only partial resistance or tolerance, henceforth referred to as "resistance", has been found to date in cultivated rice or wild Oryza species gene pools Molla et al. 2020;Srinivasachary et al. 2011). ...
... R solani does not produce spores but rather overwintering sclerotia contact the leaf sheath when rice is flooded and spread up the stem and between tillers and plants using runner hyphae (Uppala and Zhou 2018). The infection then spreads to new plants when these hyphae contact uninfected stems and leaves, resulting in localized areas of infection in the field that are often circular in shape due to the infection spreading radially from an initial point of infection (Srinivasachary et al. 2011). R. solani is a necrotrophic fungus, which produces host specific phytotoxins that may act as pathogenicity or virulence factors (Brooks 2007;Vidhyasekaran et al. 1997). ...
... Six QTL regions were revealed, but at five of them ShB resistance was associated with undesirable increases in plant height and days to heading, limiting their breeding utility. More than 70 ShB QTL have since been reported across all twelve rice chromosomes using various mapping populations (reviewed by Chen et al. 2019;Jia et al. 2009;Molla et al. 2020;Srinivasachary et al. 2011). Several of these studies also report QTL for plant height and days to heading being co-located with the identified ShB QTL, reinforcing the concern that association with tall plant height and late maturity confounds efforts to incorporate improved ShB tolerance into modern rice cultivars. ...
Article
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Background Sheath blight (ShB) disease caused by Rhizoctonia solani Kühn, is one of the most economically damaging rice (Oryza sativa L.) diseases worldwide. There are no known major resistance genes, leaving only partial resistance from small-effect QTL to deploy for cultivar improvement. Many ShB-QTL are associated with plant architectural traits detrimental to yield, including tall plants, late maturity, or open canopy from few or procumbent tillers, which confound detection of physiological resistance. Results To identify QTL for ShB resistance, 417 accessions from the Rice Diversity Panel 1 (RDP1), developed for association mapping studies, were evaluated for ShB resistance, plant height and days to heading in inoculated field plots in Arkansas, USA (AR) and Nanning, China (NC). Inoculated greenhouse-grown plants were used to evaluate ShB using a seedling-stage method to eliminate effects from height or maturity, and tiller (TN) and panicle number (PN) per plant. Potted plants were used to evaluate the RDP1 for TN and PN. Genome-wide association (GWA) mapping with over 3.4 million SNPs identified 21 targeted SNP markers associated with ShB which tagged 18 ShB-QTL not associated with undesirable plant architecture traits. Ten SNPs were associated with ShB among accessions of the Indica subspecies, ten among Japonica subspecies accessions, and one among all RDP1 accessions. Across the 18 ShB QTL, only qShB4-1 was not previously reported in biparental mapping studies and qShB9 was not reported in the GWA ShB studies. All 14 PN QTL overlapped with TN QTL, with 15 total TN QTL identified. Allele effects at the five TN QTL co-located with ShB QTL indicated that increased TN does not inevitably increase disease development; in fact, for four ShB QTL that overlapped TN QTL, the alleles increasing resistance were associated with increased TN and PN, suggesting a desirable coupling of alleles at linked genes. Conclusions Nineteen accessions identified as containing the most SNP alleles associated with ShB resistance for each subpopulation were resistant in both AR and NC field trials. Rice breeders can utilize these accessions and SNPs to develop cultivars with enhanced ShB resistance along with increased TN and PN for improved yield potential.
... Growing sheath blight resistant cultivar is the most economical and environment-friendly option to manage this disease. However, commercial rice cultivars or wild related species with complete resistance to sheath blight have not yet been found (Bonmann et al., 1992;Han et al., 2003;Srinivasachary et al., 2011) [3,13,38] . R. solani can infect seed to fully mature plant, causing moderate to significant yield loss depending on the plant part affected. ...
... Growing sheath blight resistant cultivar is the most economical and environment-friendly option to manage this disease. However, commercial rice cultivars or wild related species with complete resistance to sheath blight have not yet been found (Bonmann et al., 1992;Han et al., 2003;Srinivasachary et al., 2011) [3,13,38] . R. solani can infect seed to fully mature plant, causing moderate to significant yield loss depending on the plant part affected. ...
Article
Rice Sheath Blight is caused by Rhizoctonia solani which becomes a major problem. The use of natural products such as seaweed provides a rich source of structurally diverse and biologically active secondary metabolites, and is the ultimate way of combating these diseases. In this context, seaweed algae such as Dictyota dichotoma, Chondrococcus hornemannii, Jania rubens and Caulerpa scalpelliformis were used to control rice sheath blight. Enzymatic studies were carried out on peroxidase, polyphenol oxidase, phenylalanine ammonia lyase and β-1,3-glucanase. The rice plants were treated with Dictyota dichotoma along with soil application of Bacillus subtilis, the four enzymes raised the glucose concentration to 60.34 µg, 3.73 µg, 5.21 µg and 232 µg respectively, and then the plants were treated with the chemical called Hexaconazole and the four enzymes raised 59.20 µg, 3.57 µg, 5.17 µg and 229.3 µg respectively. While comparing these enzymes, β-1,3-glucanase release glucose content in large amount both in seaweed treated plant and also in chemical treated plant. This present study was undertaken to evaluate the various extracts of seaweeds algae such as brown, red and green seaweed along with the enzyme studied, would increase the resistance of grapes to sheath blight of rice.
... Growing sheath blight resistant cultivar is the most economical and environment-friendly option to manage this disease. However, commercial rice cultivars or wild related species with complete resistance to sheath blight have not yet been found (Bonmann et al., 1992;Han et al., 2003;Srinivasachary et al., 2011) [3,13,38] . R. solani can infect seed to fully mature plant, causing moderate to significant yield loss depending on the plant part affected. ...
... Growing sheath blight resistant cultivar is the most economical and environment-friendly option to manage this disease. However, commercial rice cultivars or wild related species with complete resistance to sheath blight have not yet been found (Bonmann et al., 1992;Han et al., 2003;Srinivasachary et al., 2011) [3,13,38] . R. solani can infect seed to fully mature plant, causing moderate to significant yield loss depending on the plant part affected. ...
Article
Full-text available
Rice Sheath Blight is caused by Rhizoctonia solani which becomes a major problem. The use of natural products such as seaweed provides a rich source of structurally diverse and biologically active secondary metabolites, and is the ultimate way of combating these diseases. In this context, seaweed algae such as Dictyota dichotoma, Chondrococcus hornemannii, Jania rubens and Caulerpa scalpelliformis were used to control rice sheath blight. Enzymatic studies were carried out on peroxidase, polyphenol oxidase, phenylalanine ammonia lyase and β-1,3-glucanase. The rice plants were treated with Dictyota dichotoma along with soil application of Bacillus subtilis, the four enzymes raised the glucose concentration to 60.34 µg, 3.73 µg, 5.21 µg and 232 µg respectively, and then the plants were treated with the chemical called Hexaconazole and the four enzymes raised 59.20 µg, 3.57 µg, 5.17 µg and 229.3 µg respectively. While comparing these enzymes, β-1,3-glucanase release glucose content in large amount both in seaweed treated plant and also in chemical treated plant. This present study was undertaken to evaluate the various extracts of seaweeds algae such as brown, red and green seaweed along with the enzyme studied, would increase the resistance of grapes to sheath blight of rice.
... During the past 3 decades, considerable efforts have been made to screen rice germplasm for ShB resistance (Srinivasachary and Savary 2011;Yadav et al. 2015). ...
... Only one co-localization of CL-SAL and RLH-SAL L5 at approximately 16.2 Mb on chromosome 3 was detected in the Xian panel (Additional file 5: Table S5). These results suggested that most of the RLH-SALs identified in this study were more likely to control the molecular mechanisms underlying physiological resistance mentioned by Srinivasachary et al. (Srinivasachary and Savary 2011) rather than the disease escape strongly determined by plant architecture. These findings may be useful for enhancing ShB resistance in rice cultivars. ...
Article
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Background: Sheath blight (ShB), caused by Rhizoctonia solani Kühn, is one of the most destructive rice diseases. Developing ShB-resistant rice cultivars represents the most economical and environmentally sound strategy for managing ShB. Results: To characterize the genetic basis for ShB resistance in rice, we conducted association studies for traits related to ShB resistance, namely culm length (CL), lesion height (LH), and relative lesion height (RLH). Combined a single locus genome-wide scan and a multi-locus method using 2,977,750 single-nucleotide polymorphisms to analyse 563 rice accessions, we detected 134, 562, and 75 suggestive associations with CL, LH, and RLH, respectively. The adjacent signals associated with RLH were merged into 27 suggestively associated loci (SALs) based on the estimated linkage disequilibrium blocks. More than 44% of detected RLH-SALs harboured multiple QTLs/genes associated with ShB resistance, while the other RLH-SALs were putative novel ShB resistance loci. A total of 261 ShB resistance putative functional genes were screened from 23 RLH-SALs according to bioinformatics and haplotype analyses. Some of the annotated genes were previously reported to encode defence-related and pathogenesis-related proteins, suggesting that quantitative resistance to ShB in rice is mediated by SA- and JA-dependent signalling pathways. Conclusions: Our findings may improve the application of germplasm resources as well as knowledge-based ShB management and the breeding of ShB-resistant rice cultivars.
... B. Frank) Donk.] Anamorph: Rhizoctonia solani) in rice is considered the second most important disease next to blast in many Asian countries [124,141,14]. Sheath blight was first reported in rice from Japan [86]. It was later reported from other rice growing regions around the world. ...
... In spite this, no effective source of resistance to the sheath blight pathogen has been identified. Further, the screening of various germplasms for sheath blight resistance were exhaustively done by various researchers and no complete donor level resistance has been found [78,141,159,35]. ...
... Sheath blight, caused by Rhizoctonia solani Kühn AG1 1A (teleomorph Thanatephorus cucumeris (A. B. Frank) Donk), is one of the most important diseases in rice worldwide [3,4]. Rice sheath blight affects both the quality and yield of rice. ...
... The prevalence if rice sheath blight is increasing in China, reflecting changes in rice farming that include increased planting density and lack of high resistance varieties. In high-temperature and humid environments, rice sheath blight has reduced rice yields by up to 50% [2][3][4][5]. Rice sheath blight hosts are widespread and the fungus core can survive for a long time in the soil, with a high rate of genetic variation. ...
Article
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Plant diseases reduce crop yield and quality, hampering the development of agriculture. Fungicides, which restrict chemical synthesis in fungi, are the strongest controls for plant diseases. However, the harmful effects on the environment due to continued and uncontrolled utilization of fungicides have become a major challenge in recent years. Plant-sourced fungicides are a class of plant antibacterial substances or compounds that induce plant defenses. They can kill or inhibit the growth of target pathogens efficiently with no or low toxicity, they degrade readily, and do not prompt development of resistance, which has led to their widespread use. In this study, the growth inhibition effect of 24 plant-sourced ethanol extracts on rice sprigs was studied. Ethanol extract of gallnuts and cloves inhibited the growth of bacteria by up to 100%. Indoor toxicity measurement results showed that the gallnut and glove constituents inhibition reached 39.23 μg/mL and 18.82 μg/mL, respectively. Extract treated rice sprigs were dry and wrinkled. Gallnut caused intracellular swelling and breakage of mitochondria, disintegration of nuclei, aggregation of protoplasts, and complete degradation of organelles in hyphae and aggregation of cellular contents. Protection of Rhizoctonia solani viability reached 46.8% for gallnut and 37.88% for clove in water emulsions of 1000 μg/mL gallnut and clove in the presence of 0.1% Tween 80. The protection by gallnut was significantly stronger than that of clove. The data could inform the choice of plant-sourced fungicides for the comprehensive treatment of rice sprig disease. The studied extract effectively protected rice sprigs and could be a suitable alternative to commercially available chemical fungicides. Further optimized field trials are needed to effectively sterilize rice paddies.
... LORE Et aL. against this disease worldwide Pinson et al., 2005;Srinivasachary et al., 2011). However, morphological features such as plant height, number of tillers, number of leaves, size of stem and leaves correlated with sheath blight severity and their effect on the disease progression have been reported in rice germplasm (Willocquet et al., 2012). ...
... In the absence of true genetic resistance against sheath blight in rice (Lore et al., 2013;Srinivasachary et al., 2011), this study provides evidence in the support of selecting more tolerant rice genotypes/varieties based on disease severity and relative yield loss. Infection at the booting stage caused overall the highest yield losses followed by tillering in the tested cultivars due to sheath blight in north-western parts of India. Therefore, the management strategies should be targeted to avoid the disease initiation at these two critical crop growth stages. ...
Article
Full-text available
Quantification of grain yield losses in mega rice varieties of south Asia due to infection by the sheath blight pathogen (Rhizoctonia solani) at different growth stages was carried out in 2 years in Northern India. Pathogen inoculation was done at the tillering, booting and grain‐filling stages of the crop under field conditions. The disease variables viz. disease severity, disease incidence, flag leaf infection and relative yield loss were determined on the mega varieties viz Swarna, Swarna Sub‐1 and PR 122. The effect of crop growth stage at inoculation and varieties was more important for disease variables than for relative yield loss. Booting and tillering stages were the most critical for higher sheath blight development with the highest relative yield loss. Among the mega rice varieties Swarna and Swarna‐Sub1, no significant difference was observed in all the disease variables and grain yield loss while the local variety PR 122 outperformed both mega varieties in disease variables and grain yield loss. PR 122 had the lowest yield losses due to low disease severity (14.22%–19.23%) during both years. All disease variables were positively correlated with relative yield losses. Regarding disease management strategies the focus should be on managing the disease initiation, particularly at the tillering and booting stages of the crop.
... Therefore, the identi cation of potential donors displaying ShB resistance from diverse sources is urgently required for breeding ShB resistant/tolerant cultivars. To date, researchers have achieved some partial resistance in the cultivated germplasm and few landraces (Srinivasachary et al. 2011; Molla et al. 2020 Zuo et al. 2013Zuo et al. , 2014Yadav et al. 2015). Most of them are reported as minor QTLs except for two major QTLs qShB9-2 and qSBR11-1 (Channamallikarjuna et al. 2010;Liu et al. 2009). ...
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Background Sheath blight (ShB) is the most serious disease of rice (Oryza sativa L.), caused by a soil-borne fungus Rhizoctonia solani Kühn (R. solani). It limits global rice productivity by causing ~50% yield loss every year. Broad host range, rapid resurgence of new pathogen races, and the lack of highly resistant germplasm are the major caveat to managing this disease. Therefore, continuous scouting of new germplasm resources resistance to R. solani is urgently required. Results In this report, we identified a very promising resistance source O. nivara accession IRGC81941A which displays partial resistance across the five years of screening against R. solani. Quantitative trait loci (QTL) mapping was performed in F2 populations that identified a total of 29 QTLs with the total phenotypic variance explained (PVE) ranged from 4.70 to 48.05%. A cluster of four QTL qRLH1.1, qRLH1.2, qRLH1.5, and qRLH1.8 stably detected which showed consistent resistant response against R. solani. The size of these QTL ranging from 0.096-420.1 Kb, based on the rice reference genome harboring several important disease resistant genes such as Ser/Thr protein kinase, auxin-responsive protein, Protease inhibitor/seed storage/LTP family protein, MLO domain-containing protein, disease responsive protein, Thaumatin-like protein, Avr9/Cf9 eliciting protein, and many transcription factors. A simple sequence repeat (SSR) marker RM212 co-segregates with this QTL cluster. Conclusion Our finding suggests that a highly stable QTL cluster confers resistance to sheath blight disease. Effective transferring of this cluster as a single unit through backcross breeding marked the identification of three agronomically superior resistant lines. These promising germplasms could be an important pre-breeding material for varietal development. PCR-based SSR marker linked to these QTLs could facilitate efficient transfer of the QTLs into rice cultivars through marker-assisted selection programs.
... Till date, researchers have not achieved much success in deploying effective and heritable resistance against this pathogen in improved breeding lines of rice. Only some partially resistant lines were identified from the landraces and other germplasm (Srinivasachary and Savary 2011;Molla et al. 2020). ...
Article
Sheath blight disease of rice causes substantial crop losses and resistance sources are rare. A moderately resistant genotype CR 1014 was identified and hybridized with highly susceptible genotype Swarna-Sub1. In the F 2 and F 2:3 generations, three QTLs (qShB-1.1, qShB-1.2 and qShB-1.3) were mapped in chromosome-1. In F 5 generation of the same cross and F 4 generation of an alternative mapping population (Tapaswini/CR 1014), only the major QTL qShB-1.1 was recorded consistently with high LOD score ([ 5.0). This stable QTL was co-localized with qShB1 reported earlier from Oryza nivara. A typical leucine rich repeat (LRR) motif containing gene (LOC_Os01g65650) and a chitin-inducible gibberellin-responsive protein coding non-LRR gene (LOC_Os01g65900) located within qShB-1.1 with high expression levels in leaf and shoot were predicted as putative candidate genes among others. Nearly 27.8% reduction in relative lesion height was recorded among several near isogenic lines of Swarna-Sub1 carrying the QTL region from CR 1014.
... RSB caused by R. solani AG1-IA is one of the most destructive diseases in rice (Srinivasachary and Savary, 2011). Mining gene resource that is resistant to RSB, and applying elite resistance genes to improve the resistance of rice is the most practical and effective way to manage the disease. ...
Article
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Rice sheath blight (RSB) is an economically significant disease affecting rice yield worldwide. Genetic resistance to RSB is associated with multiple minor genes, with each providing a minor phenotypic effect, but the underlying dominant resistance genes remain unknown. A genome wide association study (GWAS) of 259 diverse rice varieties, with genotypes based on a single nucleotide polymorphism (SNP) and haplotype, was conducted to assess their sheath blight reactions at three developmental stages (seedlings, tillering, and booting). A total of 653 genes were correlated with sheath blight resistance, of which the disease resistance protein RPM1 (OsRSR1) and protein kinase domain containing protein (OsRLCK5) were validated by overexpression and knockdown assays. We further found that the coiled-coil (CC) domain of OsRSR1 (OsRSR1-CC) and full-length OsRLCK5 interacted with serine hydroxymethyltransferase 1 (OsSHM1) and glutaredoxin (OsGRX20), respectively. It was found that OsSHM1, which has a role in the reactive oxygen species (ROS) burst, and OsGRX20 enhanced the anti-oxidation ability of plants. A regulation model of the new RSB resistance though the glutathione (GSH)-ascorbic acid (AaA) antioxidant system was therefore revealed. These results enhance our understanding of RSB resistance mechanisms and provide better gene resources for the breeding of disease resistance in rice.
... Sheath blight (SB), caused by Rhizoctonia solani Kühn, is a destructive disease that can cause 40% rice yield loss (Park et al. 2008;Ghosh et al. 2016;Singh et al. 2019). The resistance to SB is controlled by quantitative genes, and no complete resistance or immune rice germplasm has been found (Srinivasachary and Savary 2011). Chemicals are still used as a major method to control SB disease, increased production costs and caused hazardous effect to the environment (Park et al. 2008;Zuo et al. 2014). ...
Article
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Sheath blight is a serious rice disease that causes great yield losses worldwide. Sheath blight resistance is controlled by genes with minor effect. It is an urgent need to identify the resistance genes in rice germplasm and utilize them in breeding. The purpose of this study is to identify the sheath blight-resistant alleles in different rice germplasm by association mapping and explore the potential of the resistance alleles in utilization. A total of 273 rice genotypes were inoculated and evaluated for sheath blight resistance in the field for 5 years, and 158 genotypes with relatively stable disease resistance phenotype were chosen for association mapping. A wide range of phenotypic variation for sheath blight resistance was observed in the 158-genotype population. Structure analyses divided the 158 genotypes into 4 subgroups, which was consistent with principal component analysis and cluster analysis. Association mapping performed using mixed linear model with 213 markers identified 14 resistance loci, locating on all chromosomes except chromosome 6, 10 and 12. Three novel resistance loci (D704, D855, and D905) which were different from the previously reported were detected. Thirty-eight alleles were detected at the 14 loci, among which favorable alleles at 11 loci showed consistent resistance across 5 years. It was found that the favorable resistance alleles can be pyramided to improve sheath blight resistance. These results enhance the understanding of how different resistance alleles at multiple loci in regulating sheath blight resistance, and provide markers for sheath blight resistance breeding in rice.
... Apart from reducing plant growth and yield, they are also responsible for causing grain discoloration at maturity, thus reducing market value. At present, there are very limited strategies for the control of brown spot and cultivars with an adequate level of resistance are not available [3] . Fungicide treatment is one of the low cost control measures available for brown spot management but host plant resistance is most economical. ...
... The best method of controlling the disease is the use of resistant varieties. Although highly sheath blight resistant rice varieties are not available, but few genotypes like Jasmine 85, Tetep, Teqing, Minghui 63, LSBR5, LSBR33 and Pecos, showed promising resistance against the disease (Srinivasachary et al. 2011). Plants protect themselves by defense responses during the infection by pathogens. ...
Article
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Rhizoctonia solani Kuhn causes sheath blight of rice which is a common and destructive disease. The present studies focus on screening of rice genotypes against R. solani to find out promising sheath blight resistant genotypes and the role of the defense-related biochemical enzymes in six different moderately resistance, moderately susceptible and susceptible germplasm lines. A total of 196 rice germplasm lines were used to conduct a field trial to screen sheath blight resistant germplasm during 2014–2015 and 2015–2016 crop seasons. The study identified 33.1% moderately resistant, 55.6% moderately susceptible and 11.2% susceptible genotypes to sheath blight in rice. Moderately resistant cultivar IC281785 recorded higher peroxidase activity (2.990) than moderately susceptible cultivar IC282450 (1.232). Higher PPO enzyme activity was observed in Tetep (1.729) followed by IC281785 (1.423) after 24 h of inoculation. Similarly, PAL activity was highest in moderately resistant cultivars than moderately susceptible and susceptible cultivars. The highest catalase activity was observed in moderately resistant cultivar Tetep (0.963) than susceptible cultivar PB1 (0.513) after 72 h of pathogen inoculation.
... Till date, researchers have not achieved much success in deploying effective and heritable resistance against this pathogen in improved breeding lines of rice. Only some partially resistant lines were identified from the landraces and other germplasm (Srinivasachary and Savary 2011;Molla et al. 2020). ...
Article
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Sheath blight disease of rice causes substantial crop losses and resistance sources are rare. A moderately resistant genotype CR 1014 was identified and hybridized with highly susceptible genotype Swarna-Sub1. In the F2 and F2:3 generations, three QTLs (qShB-1.1, qShB-1.2 and qShB-1.3) were mapped in chromosome-1. In F5 generation of the same cross and F4 generation of an alternative mapping population (Tapaswini/CR 1014), only the major QTL qShB-1.1 was recorded consistently with high LOD score (> 5.0). This stable QTL was co-localized with qShB1 reported earlier from Oryza nivara. A typical leucine rich repeat (LRR) motif containing gene (LOC_Os01g65650) and a chitin-inducible gibberellin-responsive protein coding non-LRR gene (LOC_Os01g65900) located within qShB-1.1 with high expression levels in leaf and shoot were predicted as putative candidate genes among others. Nearly 27.8% reduction in relative lesion height was recorded among several near isogenic lines of Swarna-Sub1 carrying the QTL region from CR 1014.
... Since 1995, many QTLs for ShB resistance trait have been detected on all over the 12 chromosomes of rice genome using different mapping populations and different types of molecular markers. Although identified ShB QTLs were summarized in two previous studies Srinivasachary et al., 2011), up-to-date detailed tabular presentation of the identified QTLs, respective molecular markers, LOD value, the population used is given in Table 1. For a particular study, only identified new QTLs were kept in the table, while the re-established QTLs were excluded. ...
Article
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Rice Sheath blight disease, caused by the basidiomycetous necrotrophy Rhizoctonia solani, became one of the major threats to the rice cultivation worldwide, especially after the adoption of high yielding varieties. The pathogen is challenging to manage because of its extensively broad host range and high genetic variability and also due to the inability to find any satisfactory level of natural resistance among the available rice germplasm. It is high time to find remedies to combat the pathogen for reducing rice yield losses and subsequently to minimize the threat to global food security. The development of genetic resistance is the only alternative means to avoid the use of hazardous chemical fungicides. This review mainly focuses on the effort of better understanding the host-pathogen relationship, finding the gene loci/markers imparting resistance response, and modifying the host genome through transgenic development. The latest development and trend in the R. solani- rice patho-system research with gap analysis is provided.
... the above problem may be compounded by the fact that epidemics are so strongly dependent on crop growth (they actually can be termed 'canopy-borne', even if the inoculum is not). This leads to the complex task of partitioning the effects of QTLs that affect plant habit, of QTLs that may influence partial resistance, or both (Srinivasachary et al., 2011). ...
... The disease especially occurs in environment where water supply is scarce combined with nutritional imbalance particularly lack of nitrogen (Baranwaletal., 2013). At present, there are very limited strategies for the control of brown spot and culnvars with an adequate level of resistance are not available (Srinivasachary et al., 2011). Application of fungicides for the control of brown spot is the most effective management option, but under high disease pressure effective control is not achieved (Lore etal, 2007). ...
Article
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The results of the pot trail showed that the brown spot disease incidence was effectively reduced due to the combined application of P. fluorescens and ICF 310 (T5), which recorded the least disease incidence (9.98%). These were followed by T4 and T3. The maximum disease incidence was recorded in control (T7) (50.12%). Among the treatments, the combined application of antagonists and ICF10(T5) recorded maximum germination percentage (93.89%), plant height (80.12cm), No. of productive tillers per clump (19.34), grain yield (44.57 g/pot) and straw yield (88.14 g/pot). The untreated control recorded the minimum plant growth biometric values of rice.
... Rice sheath blight caused by Rhizoctonia solani J.G. Kühn [Thanatephorus cucumeris (A.B. Frank) Donk], anastomosis group 1 IA (AG-1 IA) is prevalent and an economically important fungal disease in most temperate, subtropical and tropical rice-production areas (Srinivasachary et al. 2011). It has a wide host range, and the causal fungus can survive between crop seasons as sclerotia formed on or near the lesions that lie dormant in soil for a few years under a temperate climate. ...
Article
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Silicon (Si) application is considered one means of cultural management having beneficial effects on the control of rice diseases. Carbonized rice husk (CRH)—a cost-effective biochar derived from a by-product of rice production—has been proposed as Si fertilizer as well as for promoting carbon sequestration in soil. This experiment was conducted in an irrigated paddy field in Tsukuba, Japan, to evaluate the potential effects of CRH application on sheath blight among four treatments (two levels of CRH application at 1.5 and 3.0 t ha-1, a spray of fungicide with flutolanil, and the control without any application). The results demonstrated that CRH at 3.0 t ha-1 increased rice Si content by 9% and regulated sheath blight development in the plant community to some extent after inoculation, whereas CRH at 1.5 t ha-1 showed no clear impacts on rice plants and fungal pathogen development. The fungicide application with flutolanil had the lowest rate of sheath blight development, but did not affect rice Si content. The results suggest that CRH application at 3.0 t ha-1 or more could be an option for integrated management of sheath blight without negative effects on rice yield.
... Spray application of 0.03% neem formulations (300 ppm azadirachtin) at 4.5 ml/l has been reported very effective in suppressing the disease (Biswas 2007). Several commercial botanical pesticides like Tricure (Muralidharan et al. 2003), Spictaf and Neemazal (Biswas and Roychoudhury 2003), Achook (Kandhari 2007) and Spictaf and Tricure (Singh et al. 2010) have also been found promising in reducing the disease severity and in traditional rice cultivars like Tetep, Jasmine 85, Tequing, Bhasamanik, Lalsatkara, ARC 15762, ARC 18119, ARC 18275, ARC 18545, D 256, MTU 1010, YSBR 1 (Wang et al. 2009, Srinivasachary et al. 2011, Lore et al. 2015, HKR 99-103, HKRH 1059 and IR 64683-87-2-2-3-3 (Singh et al. 2010) and N-22 (Acc. 4819), N-22 (Acc. ...
Article
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The present investigation was carried out at CCSHAU Rice Research Station, Haryana, to manage sheath blight of rice (Oryza sativa L.) caused by Rhizoctonia solani Kuhn through host resistance, botanical extracts, and to develop a spray schedule of best two botanical extracts, i.e. garlic cloves and turmeric powder in combination with the best two fungicides, viz. azoxystrobin 18.2% + difenoconazole 11.4% SC and thifluzamide 23.9% SC. Out of 307 rice genotypes screened during kharif 2016 and 2017, none was found highly resistant against sheath blight. However, only one genotype (RMS-BL-6) showed consistent resistance reaction during both the years while five entries (MR 8333, KNM 1730, PAU 7111-1-1-0, RP 5141-432-10-3-2 and VL 32197) showed a moderately resistant reaction. The rice genotype RMS-BL-6 also showed moderate resistance to bacterial blight, and was moderately susceptible to stem rot. Extracts of garlic cloves and turmeric powder were found effective and reduced the vertical disease spread (relative lesion height) by 36.62% and 35.38% along with 11.59% and 10.85% enhanced grain yield of paddy respectively. Among combination treatments, application of azoxystrobin 18.2% + difenoconazole 11.4% SC at 1 day after inoculation (DAI) followed by extract of garlic cloves at 11 days after inoculation was highly effective and statistically at par with two applications of azoxystrobin 18.2% + difenoconazole 11.4% SC (at 1 and 11 DAI) and thifluzamide 23.9% SC (at 1 and 11 DAI); application of thifluzamide 23.9% SC (1 DAI) followed by azoxystrobin 18.2% + difenoconazole 11.4% SC (11 DAI) and vice-versa.
... As a result, they are not attractive for utilization in breeding programs. In addition, many rice endogenous genes were reported to confer resistance to sheath blight disease (Srinivasachary and Savary, 2011;Molla et al., 2013;Wang et al., 2015;Karmakar et al., 2016;Xue et al., 2016). However, the mechanism of resistance against sheath blight is yet to be understood clearly. ...
Article
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Rice sheath blight (ShB) disease, caused by the fungal pathogen Rhizoctonia solani AG1-IA, is one of the devastating diseases and causes severe yield losses all over the world. No completely resistant germplasm is known till now, and as a result, the progress in resistance breeding is unsatisfactory. Basic studies to identify candidate genes, QTLs, and to better understand the host–pathogen interaction are also scanty. In this study, we report the identification of a new ShB-tolerant rice germplasm, CR 1014. Further, we investigated the basis of tolerance by exploring the disease responsive differentially expressed transcriptome and comparing them with that of a susceptible variety, Swarna-Sub1. A total of 815 and 551 genes were found to be differentially regulated in CR 1014 and Swarna-Sub1, respectively, at two different time points. The result shows that the ability to upregulate genes for glycosyl hydrolase, secondary metabolite biosynthesis, cytoskeleton and membrane integrity, the glycolytic pathway, and maintaining photosynthesis make CR 1014 a superior performer in resisting the ShB pathogen. We discuss several putative candidate genes for ShB resistance. The present study, for the first time, revealed the basis of ShB tolerance in the germplasm CR1014 and should prove to be particularly valuable in understanding molecular response to ShB infection. The knowledge could be utilized to devise strategies to manage the disease better.
... Breeding for sheath blight resistance is very difficult in absence of lack of reliable stable resistance sources in rice germplasm. No complete resistance has been identified in rice varieties or wild-related species (Srinivasachary et al., 2011). To date, limited resources of genetic resistance are available worldwide and hence searching for resistant germplasm has become an international effort (Prasad and Eizenga, 2008). ...
Article
Sheath blight disease caused by the necrotrophic, soilborne pathogen Rhizoctonia solani Kuhn, is the global threat to rice production. Lack of reliable stable resistance sources in rice germplasm pool for sheath blight has made resistance breeding a very difficult task. In the current study, 101 rice landraces were screened against R. solani under artificial epiphytotics and identified six moderately resistant landraces, Jigguvaratiga, Honasu, Jeer Sali, Jeeraga-2, BiliKagga, and Medini Sannabatta with relative lesion height (RLH) range of 21-30%. Landrace Jigguvaratiga with consistent and better level of resistance (21% RLH) than resistant check Tetep (RLH 28%) was used to develop mapping population. DNA markers associated with ShB resistance were identified in F<sub>2</sub> mapping population developed from Jigguvaratiga × BPT5204 (susceptible variety) using bulk segregant analysis. Among 56 parental polymorphic markers, RM5556, RM6208, and RM7 were polymorphic between the bulks. Single marker analysis indicated the significant association of ShB with RM5556 and RM6208 with phenotypic variance (R<sup>2</sup>) of 28.29 and 20.06%, respectively. Co-segregation analysis confirmed the strong association of RM5556 and RM6208 located on chromosome 8 for ShB trait. This is the first report on association of RM6208 marker for ShB resistance. In silico analysis revealed that RM6208 loci resides the stearoyl ACP desaturases protein, which is involved in defense mechanism against plant pathogens. RM5556 loci resides a protein, with unknown function. The putative candidate genes or quantitative trait locus harbouring at the marker interval of RM5556 and RM6208 can be further used to develop ShB resistant varieties using molecular breeding approaches.
... Thanatephorus cucumeris) (Frank) Donk is a major disease of rice (Oryza sativa L.) globally and it causes serious yield losses, under input-intensive crop management and favourable environmental conditions (Savary et al., 2000). The pathogen has a wide host range and R gene (s) that give complete resistance in rice against this disease have not been identified (Pinson et al., 2005;Srinivasachary et al., 2011). However partial resistance to rice sheath blight has been identified in the cultivars of O. sativa (Lore et al., 2013) and other Oryza species (Brar & Khush, 2003). ...
Article
Sheath blight caused by Rhizoctonia solani is one of the most important rice diseases worldwide, especially under irrigated agro‐ecosystem. To detect quantitative differences in disease development, three inoculum types, viz. mycelial bit, single sclerotium and mycelial ball, were evaluated against five rice genotypes using detached tiller technique. Different disease variables such as number of lesions, disease severity, vertical sheath colonization (VSC), relative vertical sheath colonization (RVSC) and mean lesion length were measured for quantification of sheath blight resistance. All the disease variables were positively correlated with each other. Among the inoculum types, mycelial ball produced significantly higher level of disease variables in all the genotypes and resolved level of resistance better than the other two methods. Significantly lower values of disease severity, VSC and RVSC were observed on rice genotype Tetep, PR 108 and D 256 as compared with susceptible check D 6766 when inoculated with different inoculum types. These results can provide a basis to design methods to evaluate quantitative sheath blight resistance with high precision in rice genotypes.
... High level of genetic resistance has not been noticed against these diseases among cultivated rice varieties (Srinivasachary et al., 2010). In the absence of suitable resistant donors, fungicides are the major source to reduce the pathogen in field as seed treatment and foliar applications. ...
... In other gramineaceous plant diseases caused by Rhizoctonia, Sheath Blight of rice, Sharp Eyespot of wheat, root rot of maize and leaf spot of tall fescue, resistant lines have been identified (2,7,23). ...
Conference Paper
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For rhizoctonia root rot, takeall and CRR diseases of wheat, the search for resistance in Australia has been fragmented, involved very small germplasm diversity and had no commercialisation path. Previous resistance screening work was often done without precise phenotyping systems, without an understanding of the variability in resistance expression, and without modern genotyping tools. The search for resistance to fusarium head blight and crown rot disease of wheat suffered from similar problems, but recently good resistance have been found for those diseases with more systematic and thorough germplasm screening and better phenotyping. With a comprehensive pre-breeding program, effective levels of resistance to rhizoctonia root rot, takeall and common root can also be identified and delivered to Australian wheat breeding programs, saving farmers up to $162m per annum.
... oryzae Bacterial (Liu et al., 2014;Mew et al., 1993;Ou, 1985) Bacterial leaf streak Xanthomonas oryzae pv. oryzicola Bacterial (Liu et al., 2014) Bacterial panicle blight Burkholderia glumae Bacterial (Ham et al., 2011;Liu et al., 2014) Rice blast Magnaporthe oryzae Bacterial (Liu et al., 2014) Rice sheath blight Rhizoctonia solani Bacterial (Liu et al., 2014;Ou, 1985;Srinivasachary, 2011) False smut Ustilaginoidea virens Fungal (Guo et al., 2012;Liu et al., 2014;Reddy et al., 2011;Tanaka et al., 2008) Sheath rot Sarocladium oryzae Fungal (Liu et al., 2014;Ou, 1985) Brown spot Cochliobolus miyabeanus Fungal (Barnwal et al., 2013;Liu et al., 2014;Ou, 1985) Bakanae Fusarium fujikuroi Fungal (Liu et al., 2014;Ou, 1985) Maize Bacterial stalk rot Erwinia carotovora Bacterial (Sinha and Prasad, 1977;Subedi, 2015) Bacterial leaf stripe Xanthomonas rubrilineans Bacterial (Subedi, 2015) Stewart wilt Erwinia stewartii Bacterial (Kang and Zuber, 1988;Subedi, 2015) Gray leaf spot Cercospora zeae-maydis Fungal (Ward et al., 1999) Northern leaf blight Helminthosporium turcicum Fungal (Ullstrup, 1972) Southern leaf blight Helminthosporium maydis Fungal (Ullstrup, 1972) diseases, which can significantly contribute to reducing yield losses (Pérez-Bueno et al., 2016); (ii) the red-greenblue (RGB) technique, despite the lack of a precise definition, is based on color and texture, and is widely used in agricultural research with certain advantages (economical, easy to operate), and modern models can acquire images with high spatial resolutions (Chaudhary et al., 2012); (iii) the infrared process uses the visible infrared wavelengths of the electromagnetic spectrum to detect plant stress, and this method is also useful for plant disease detection (Sankaran et al., 2013); (iv) the thermal method transforms the different types of radiations detected from objects to distinct types of images for feature extraction, analysis, and classification. It was initially developed for military purposes, but its applicability in agriculture and plant disease detection has been proven by researchers (Awad et al., (Osunlaja, 1983) Anthracnose leaf blight Colletotrichum graminicola Fungal (Gorman et al., 2020;Schall et al., 1980) Head smut Sphacelotheca reiliana Fungal (Bernardo et al., 1992) Common smut Ustilago maydis Fungal (Boland et al., 2004) Fusarium kernel rot (Gray ear rot) ...
... oryzae Bacterial (Liu et al., 2014;Mew et al., 1993;Ou, 1985) Bacterial leaf streak Xanthomonas oryzae pv. oryzicola Bacterial (Liu et al., 2014) Bacterial panicle blight Burkholderia glumae Bacterial (Ham et al., 2011;Liu et al., 2014) Rice blast Magnaporthe oryzae Bacterial (Liu et al., 2014) Rice sheath blight Rhizoctonia solani Bacterial (Liu et al., 2014;Ou, 1985;Srinivasachary, 2011) False smut Ustilaginoidea virens Fungal (Guo et al., 2012;Liu et al., 2014;Reddy et al., 2011;Tanaka et al., 2008) Sheath rot Sarocladium oryzae Fungal (Liu et al., 2014;Ou, 1985) Brown spot Cochliobolus miyabeanus Fungal (Barnwal et al., 2013;Liu et al., 2014;Ou, 1985) Bakanae Fusarium fujikuroi Fungal (Liu et al., 2014;Ou, 1985) Maize Bacterial stalk rot Erwinia carotovora Bacterial (Sinha and Prasad, 1977;Subedi, 2015) Bacterial leaf stripe Xanthomonas rubrilineans Bacterial (Subedi, 2015) Stewart wilt Erwinia stewartii Bacterial (Kang and Zuber, 1988;Subedi, 2015) Gray leaf spot Cercospora zeae-maydis Fungal (Ward et al., 1999) Northern leaf blight Helminthosporium turcicum Fungal (Ullstrup, 1972) Southern leaf blight Helminthosporium maydis Fungal (Ullstrup, 1972) diseases, which can significantly contribute to reducing yield losses (Pérez-Bueno et al., 2016); (ii) the red-greenblue (RGB) technique, despite the lack of a precise definition, is based on color and texture, and is widely used in agricultural research with certain advantages (economical, easy to operate), and modern models can acquire images with high spatial resolutions (Chaudhary et al., 2012); (iii) the infrared process uses the visible infrared wavelengths of the electromagnetic spectrum to detect plant stress, and this method is also useful for plant disease detection (Sankaran et al., 2013); (iv) the thermal method transforms the different types of radiations detected from objects to distinct types of images for feature extraction, analysis, and classification. It was initially developed for military purposes, but its applicability in agriculture and plant disease detection has been proven by researchers (Awad et al., (Osunlaja, 1983) Anthracnose leaf blight Colletotrichum graminicola Fungal (Gorman et al., 2020;Schall et al., 1980) Head smut Sphacelotheca reiliana Fungal (Bernardo et al., 1992) Common smut Ustilago maydis Fungal (Boland et al., 2004) Fusarium kernel rot (Gray ear rot) ...
Article
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Crops such as wheat (Triticum aestivum L.), rice (Oryza sativa L.), maize (Zea mays L.), and soybean (Glycine max L.) are the most important sources of food and ensure food security worldwide. Yield losses because of plant-bacteria and fungi are a major global concern. Therefore, various management technologies like diagnostic techniques for bacterial and fungal diseases are among the most important criteria for yield loss management from biotic diseases. In particular, the early detection, prediction, and classification of plant diseases are essential for improved monitoring of plant diseases and resources. Over the last few decades, the utilization of digital imaging systems for plant disease identification has received considerable attention. Moreover, digital imaging methods have facilitated the early detection of several plant diseases using both 2-dimensional image assessment and the current more accurate 3-dimensional image analysis techniques via knowledge-based approaches using MRI and CT. Simultaneously, state-of-the-art, machine and deep learning approaches with different algorithms have progressed to increase precision in disease detection. In this study, we review and discuss important bacterial and fungal diseases that occur in major food crops, the importance of their early detection, and different imaging systems used in plant disease detection, their applications, challenges, and prospects. A literature survey indicated that with the emergence of new tools, the accuracy of the digital imaging system for plant disease detection is bound to increase and has a wide scope in the agriculture sector for helping the farming community as well as increasing sustainability and food security.
... Wisser et al. (2011) noted negative correlation between disease phenotypes and flowering time for some diseases in maize. Srinivasachary et al. (2011) reported that sheath blight resistance was independent of days to heading. Negeri et al. (2011) identified the most significant effect of flowering time on southern leaf blight resistance. ...
Article
Banded leaf and sheath blight (BLSB) is one of the most important fungal diseases of maize causing substantial yield reduction. For disease management, resistance breeding is one of the best possible ways and wild relatives are a valuable source of resistance. Teosinte, the progenitor of maize, is known to carry BLSB resistance. Therefore, attempts were made to cross teosinte with maize to have resistance introgression. In total, one hundred sixty-nine teosinte derived maize BC 1 F 5 lines were evaluated under an artificially inoculated environment in a Randomized Complete Block Design with two replications in two different dates of sowing i.e. 9 July, 2018 (DE1) and 23 July, 2018 (DE2). The same sets of genotypes were also planted in two replications on 9 July 2018 under an un-inoculated situation to record 14 yield and other plant traits and identify their association with the disease. Nine lines (MT-25, MT-90, MT-99, MT-128, MT-136, MT-144, MT-145, MT-148, and MT-152), exhibiting disease score ranging between 3.1 and 5.0 and PDI values between 33.34 and 55.55%, were categorized moderately resistant to BLSB. Plant height (r = − 0.178*), ear length (r = − 0.711***), ear diameter (r = − 0.743***), kernel rows per ear (r = − 0.746***), kernels per row (r =-0.680***), test weight (r =-0.718***), yield per plant (r = − 0.657***) were negatively correlated whereas flag leaf angle (r = + 0.7061***) was positively correlated with PDI. Among nine moderately resistant lines MT-145 was ranked first with maximum score of 41 followed by MT-36, MT-152, MT25 = MT99, MT-144, MT-128, MT-148, MT-90 in decreasing order. By comparing disease severity on two different dates of sowing, the third week of July is recommended for sowing of maize for reducing BLSB severity.
... This fungal disease was first documented by Miyake (1910) in rice plants in Japan. This disease is prevalent in all counties where intensive rice cultivation occurs (Srinivasachary, 2011). Sclerotia are the typical inoculum of R. solani, which can remain viable in soil and water for up to 3 years. ...
Article
Rice blast caused by Magnaporthe oryzae and sheath blight caused by Rhizoctonia solani, are the two major diseases of rice that cause enormous losses in rice production worldwide. Identification and utilization of broad-spectrum resistance resources have been considered sustainable and effective strategies. However, the majority of the resistance genes and QTLs identified have often been found to be race-specific, and their resistance is frequently broken down due to continuous exposure to the pathogen. Therefore, integrated approaches to improve plant resistance against such devastating pathogen have great importance. Silicon (Si), a beneficial element for plant growth, has shown to provide a prophylactic effect against many pathogens. The application of Si helps the plants to combat the disease-causing pathogens, either through its deposition in different parts of the plant or through modulation/induction of specific defense genes by yet an unknown mechanism. Some reports have shown that Si imparts resistance to rice blast and sheath blight. The present review summarizes the mechanism of Si transport and deposition and its effect on rice growth and development. A special emphasis has been given to explore the existing evidence showing Si mediated blast and sheath blight resistance and the mechanism involved in resistance. This review will help to understand the prophylactic effects of Si against sheath blight and blast disease at the mechanical, physiological, and genetic levels. The information provided here will help develop a strategy to explore Si derived benefits for sustainable rice production.
... Sheath blight of rice caused by a basidiomycetous necrotrophic fungus Rhizoctonia solani (Kuhn) [teleomorph-Thanatephorus cucumeris Frank (Donk)] is the second most prevalent disease next to blast of rice in the world (Molla et al., 2020). Rhizoctonia solani (Kuhn) infects a wide range of host plants belonging to 188 genera from 33 different families (Srinivasachary et al., 2010;Sattari et al., 2014). Rhizoctonia solani has high genetic variability making it capable of infecting wide host range, comprises 14 anastomosis groups via. ...
Article
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Rice crop endures several biotic stresses among which sheath blight is one of the devastating diseases. This disease is caused by necrotrophic fungus Rhizoctonia solani AG1 IA that reduces 20 to 40% yield. Forty two diverse rice genotypes were evaluated against sheath blight under artificial epiphytotic condition in the field of National Wheat Research Program Bhairahawa, Nepal during the year 2019. Four disease variables viz. PDLI (Percent diseased leaf incidence), PDTI (Percent diseased tiller incidence), PRCHI (Percent relative collar height infection), and AUDPC (Area under disease progress curve) were considered for evaluation of genotypes. Out of forty two genotypes Sabitri, GSR 310 and Hardinath-3 were found moderately resistant with mean AUDPC values 217.99, 252.78 and 214.67 per day re- spectively. Furthermore IR 15D 110, Pant-1, NR 2152-23-1-2-1-1-1-1 and IR 82635-B-B-114-3 were found moderately susceptible with mean AUDPC values 438.48, 445.55, 421.81 and 437.59 respectively. Moderately resistant genotypes viz. Sabitri, GSR 310 and Hardinath-3 had PDLI range 30.98- 31.67, PDTI range 10.56-15 and PRCHI range 9.01-28.64 whereas moderately susceptible genotypes IR 15D 110, Pant-1, NR 2152-23-1-2-1-1-1-1 and IR 82635-B-B-114-3 had PDLI range 31.25-51.29, PDTI range 25.82-38.75 and PRCHI range 22.18-45.8. Disease variables PDLI, PDTI and PRCHI were positively and significantly correlated with AUDPC with correlation coefficient value 0.75, 0.65 and 0.62, respectively. Moderately resistant rice genotypes found in this study could be evaluated for yield potential and its stability across different geographical region of Nepal and could be a good alternative against sheath blight diseases for Nepalese farmers.
... With the availability of only partial resistance against sheath blight (Pinson et al. 2005;Srinivasachary et al. 2011), the present study was undertaken to explore the resistance/ susceptibility level of these new flood-tolerant varieties with their parents, and two popular varieties of North India (PR 114 and PR 121) under field conditions. The objectives of this study was i) To assess the temporal and spatial progression of the sheath blight in mega rice varieties under field conditions, ii) To evaluate the relationship between plant architecture and disease severity, and iii) develop models to predict temporal and spatial spread of the disease. ...
Article
The temporal and spatial progress of sheath blight was assessed on a set of mega rice varieties of South Asia and local varieties of North India in field experiments for two consecutive years. With artificially created disease focus disease severity was recorded on five un-inoculated plants from the focus in four directions after two, four and six weeks of inoculation. The mega varieties differed in their level of susceptibility to sheath blight. The temporal progression of the disease was significantly increased in Swarna and Swarna Sub-1 followed by PR 114 and PR 121 varieties. Area under disease progress curve (AUDPC) ranged 184.92 – 683.67 in tested varieties. The disease severity decreased as the distance from the disease focus increased in all varieties, the significance of the spatial spread depended on the susceptibility level of the variety. Swarna and Swarna Sub-1 showed higher level of susceptibility. The exponential regression model explained the increased severity with time which get decreased with increase in distance from the disease focus. Relationship of week after inoculation with disease severity indicated that model explained 96.0% variability of the response data in Swarna. The morphological traits like plant height, number of tillers per hill and tiller angle of the varieties had a significant correlation with the disease severity and incidence. In the absence of genetic resistance, this study provides evidence of requirement of a six-week period for differentiating the susceptible or resistant response of rice varieties to sheath blight under field conditions. Plant morphological traits are the key factor which can be consider in disease resistant breeding programme.
... Rice sheath blight, a soil-borne fungal disease [1,2], is caused by Rhizoctonia solani (R. solani) infection, and is one of the three major diseases of rice; specifically, the second most common disease next to rice blast. The asexual state of the pathogen is R. solani, and the sexual state is Thanatephorus cucumeris [3]. It occurs globally in rice plantations in the form of hyphae or sclerotium, which reduces the yield of rice by 10-30%, and could reach up to 50% in severe disease areas [4]. ...
Article
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Rice sheath blight, caused by Rhizoctonia solani, is one of the major rice diseases. In order to better understand the inhibitory mechanism of lauric acid on the disease, RNA sequencing (RNA-Seq) was used to analyze the transcriptome changes in Rhizoctonia solani treated with lauric acid for 3 h, 6 h, 18 h, and 24 h, including 2306 genes; 1994 genes; 2778 genes; and 2872 genes. Based on gene ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses, we found that protein processing in endoplasmic reticulum (KO04141), carbon metabolism (KO01200), and starch and sucrose metabolism were significantly enriched. Most oxidoreductase, dehydrogenase, reductase, and transferase genes are downregulated in this process. Lauric acid can affect ergosterol content, mitochondrial membrane potential collapse, hydrogen peroxide content, electrolyte leakage, reactive oxygen species balance, and can induce endoplasmic reticulum (ER) stress. Lauric acid also increased the expression levels of ER chaperone glucose regulatory protein Grp78 (BIP), protein disulfide isomerase (PDI), and Calpain (CNX), and decreased the expression levels of HSP40, HSP70, and HSP90 genes. Lauric acid affected the ergosterol content in the cell membrane of R. solani, which induces ER stress and increases the BiP level to induce the apoptosis of Rhizoctonia solani. These results indicated that lauric acid could be used to control rice sheath blight.
... The reduced pathogens multiplication and lesions on leaves and stems suggest that CAGC molecules could protect the rice plants as equivalent to genetically enhanced plants introgressed with Xa alleles or gene-edited plants (Oliva et al., 2019). R. solani is a catastrophic fungal pathogen because of its complex lifestyle and coenocytic nature, and developing resistance against this pathogen is a challenging task (Srinivasachary and Savary, 2011). The CAGCs tested against R. solani could effectively prevent the sclerotia growth and kill the pathogen as evidenced by the MTT assay. ...
Article
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Xanthomonas Oryzae pv. oryzae (Xoo) causes bacterial blight and Rhizoctonia solani (R. solani) causes sheath blight in rice accounting for >75% of crop losses. Therefore, there is an urgent need to develop strategies for the mitigation of these pathogen infections. In this study, we report the antimicrobial efficacy of Cholic Acid-Glycine Conjugates (CAGCs) against Xoo and R. solani. We show that CAGC C6 is a broad-spectrum antimicrobial and is also able to degrade biofilms. The application of C6 did not hamper plant growth and showed minimal effect on the plant cell membranes. Exogenous application of C6 on pre-infection or post-infection of Xoo on rice susceptible genotype Taichung native (TN1) can mitigate the bacterial load and improve resistance through upregulation of plant defense genes. We further demonstrate that C6 can induce plant defense responses when seeds were primed with C6 CAGC. Therefore, this study demonstrates the potential of CAGCs as effective antimicrobials for crop protection that can be further explored for field applications.
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Oryza nivara is considered one of the wild progenitors of cultivated Asian rice (O. sativa). An O. nivara (IRGC104443) accession, previously identified as being moderately resistant to rice sheath blight disease, was used as the donor parent to develop an advanced backcross population with the U.S. rice (O. sativa) cultivar, LaGrue, as the recurrent parent. The population was genotyped with 210 DNA markers and a linkage map constructed that spanned 1488.9 cM. Sheath blight (ShB) disease was evaluated in both greenhouse and field conditions. Days to heading (DTHD), plant height (PTHT) and culm (angle) habit (CULMHAB) were recorded because they can confound sheath blight disease ratings under field conditions. Multiple interval mapping identified qShB9 as the ShB-QTL being the source of resistance and the resistance was attributed to the O. nivara allele. The single CULMHAB QTL, qCULMHAB9, was also located in this region but had a different peak suggesting the more open tillering was most likely due to the TILLER ANGLE CONTROL-1 gene which was fine-mapped near the chromosome 9 ShB resistance in other O. sativa populations. The ShB QTL, qShB3-2-mc, identified in the greenhouse study was not verified in the field studies. None of the three DTHD QTL were colocalized with ShB QTL, while the single PTHT QTL was mapped to the region of the semi-dwarf-1 gene for short stature on chromosome 1. Further studies will be undertaken to fine map the qShB9 region and identify linked markers for use in cultivar development.
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Rice sheath blight (SB) disease is a global issue that causes great yield losses each year. To explore whether SB field resistance can be predicted, 273 rice genotypes were inoculated and evaluated for SB field resistance across nine environments (2012-2019) to identify loci associated with SB resistance by association mapping. A total of 80 significant marker-trait associations were detected in nine environments, among which six loci (D130B, D230A, D304B, D309, D427A, and RM409) were repeatedly detected in at least two environments. A linear regression model for predicting SB lesion length was developed using genotypic data of these 6 loci and SB field resistance data of the 273 rice genotypes: y = 34.44 - 0.56 x, where y is the predicted value of lesion length, and x is the total genotypic value of the six loci. A recombinant inbred line (RIL) population consisting of 219 lines that was grown in six environments (from 2013 to 2018) for evaluation of SB field resistance was used to check the prediction accuracy of the prediction model. The average absolute error between the predicted lesion length and real lesion length for the RIL population was 6.67 cm. The absolute errors between predicted and real lesion lengths were below 6 cm for 51.22% of the lines, and were below 9 cm for 71.22% of the lines. An SB visual rating prediction model was also developed, the average absolute error between the predicted visual rating and real visual rating for the RIL population was 0.94. These results indicated that the rice SB lesion length can be predicted by the development of a linear regression model using both genotypic and phenotypic data.
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Sheath blight disease (ShB) is considered to be the second most important disease affecting rice, and the genetic mechanism of ShB resistance in rice is great complicated. Uncovering genetic mechanism of ShB resistance and strong resistant varieties in rice are the premise for ShB resistance improvement. A rice ShB genome-wide association study (GWAS) was performed using approximately five million SNPs within Ting’s core collection. “Early pradifice”, one typical japonica, was determined to be the most resistant variety in both 2016 and 2017. A total of 34 and four significant (p ≤ 1.93 × 10−8) SNPs were observed in 2016 and 2017, respectively. Moreover, 23 of 34 and two of four gene-based SNPs not reported in previous studies in 2016 and 2017, respectively, were identified as significantly associated with rice ShB resistance. Furthermore, we performed GO (gene ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) analyses for the genes located at a region within 10 kb of the significant SNPs. Both in 2016 and 2017, we observed that genes were uniquely enriched in the regulation of transcription and RNA processing in the category of “biological process”, plasma membrane, nucleus, integral component of membrane and cell wall in the category of “cellular component”, and ATP binding in the category of “molecular function”. The results of the present study may establish a foundation for further research investigating these elite genes and utilizing the resistant varieties in Ting’s core collection to improve rice ShB resistance.
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Banded leaf and sheath blight is considered as the most important disease of maize, and development of resistant varieties is the most viable option. Total one seventy-one [169 BC1F5 teosinte-derived maize lines along with teosinte (resistant) and DI-103 (susceptible) as a check] were planted in randomized complete block design in two different dates of sowing (DE1 and DE2) under artificially inoculated environments. Molecular profiling of population was carried out with identified 76 polymorphic microsatellite markers. Association of the markers with the quantitative trait loci (QTL) was performed by single marker analysis (SMA) using linear regression and maximum likelihood analysis. The single marker analysis of variance (ANOVA) revealed one major QTL on chromosome 5 and four minor QTLs on chromosomes 1, 3, 4, and 8, respectively, for BLSB resistance under first sowing (DE1). In second sowing (DE2), four minor QTLs were detected on four chromosomes 1, 3, 5 and 8. Out of these, nine QTLs two were identified across the environments, which were linked with markers umc1500 and phi10918, considered as stable QTLs. Among seven detected QTLs for BLSB resistance, a major QTL linked with phi10918 was co-localized with three minor QTLs for ear length, kernel rows per ear and kernels per row. These results suggest that the morphological traits and QTLs which have been found to associate with banded leaf and sheath blight resistance are a good choice to enhance BLSB resistance. Utilization of QTLs governing morphological traits like days to anthesis, days to silking, flag leaf architecture, plant height, etc., could be a good choice along with QTLs governing BLSB resistance to enhance BLSB resistance through QTL pyramiding.
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Rice is an important food crop for three billion people worldwide. The crop is vulnerable to several diseases. Sheath blight caused by fungal pathogen Rhizoctonia solani is a significant threat to rice cultivation accounting for up to 50% yield losses. The pathogen penetrates leaf blades and sheaths, leading to plant necrosis; and major disease resistance gene against the pathogen is not available. This study describes development of sheath blight resistant transgenic indica and japonica rice cultivars through introduction of antifungal β-1,3-glucanase transgene cloned from Trichoderma. The transgene integration and expression in transformed T0 rice plants was examined by PCR, RT-PCR, qRT-PCR demonstrating up to 5-fold higher expression as compared to non-transgenic plants. The bioassay of T0, T1 and homozygous T2 progeny plants with virulent R. solani isolate revealed that plants carrying high level of β-1,3-glucanase expression displayed moderately resistant reaction to the pathogen. The optical micrographs of leaf sheath cells from moderately resistant plant after pathogen inoculation displayed presence of a few hyphae with sparse branching; on the contrary, pathogen hyphae in susceptible non-transgenic plant cells were present in abundance with profuse hyphal branching and forming prominent infection cushions. The disease severity in T2 progeny plants was significantly less as compared to non-transgenic plants confirming role of β-1,3-glucanase in imparting resistance.
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The rice (Oryza sativa L.) productivity is often adversely disturbed by several abiotic and biotic stresses such as drought, submergence, fungal, bacterial, and nematode oriented biotic diseases and pest like brown plant hopper (BPH) and stem borer (SB). The major biotic stresses such as bacterial leaf blight (BLB), sheath blight (ShB), blast, brown spot (BS), false smut (FS), brown plant hopper (BPH), yellow stem borer (YSB), and gall midge (GM) play crucial roles in decreasing the productivity and quality of rice grains. Among the several breeding procedures and various control measures available for mitigating the biotic stresses/factors, the host plant resistance is most effective, economic and eco-friendly which is basically developed by traditional breeding approaches. The related species of rice and wild sources are important for identification of many resistance genes/QTLs, which are successfully introgressed or deployed or pyramided in numerous breeding lines through resistance breeding program and various molecular approaches. In this chapter, an inclusive valuation of the conventional and molecular approaches for mitigating the biotic stresses in rice by imparting major resistance sources has been presented.
Article
Although rice is one of the most cultivated, consumed, and essential crops worldwide, it is highly susceptible to a wide range of bacterial and fungal pathogens that significantly reduce the production and quality of rice. Recently, our research group reported that the plant growth‐promoting rhizobacterium Lysobacter gummosus OH17 was able to enhance the ethylene levels in Oryza sativa ‘Nipponbare’ plants at the late interaction stages. In this work, L. gummosus OH17 was found to be capable of inducing the overexpression of relevant genes of the jasmonic acid and ethylene transduction pathways in Nipponbare plants, such as OsACC, OsACO, OsERF3, and OsLOX, which resulted in the up‐regulation of a number of pathogenesis‐related proteins. The observed metabolic effects enhanced the disease resistance of rice against the three most devastating rice pathogens: Magnaporthe oryzae causing rice blast, Rhizoctonia solani causing rice sheath blight, and Xanthomonas oryzae pv. oryzae causing bacterial leaf blight. Furthermore, it was shown that L. gummosus OH17 also enhanced ethylene production levels in other O. sativa varieties from both the japonica and indica subspecies. Here, we report for the first time the metabolic alterations produced by plant growth‐promoting rhizobacterium L. gummosus OH17 at the late interaction stages and how these alterations induce systemic resistance. Plant growth‐promoting rhizobacterium Lysobacter gummosus OH17 induces systemic resistance in rice via up‐regulation of the ethylene signalling pathway at the late interaction stage.
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The rice (Oryza sativa L.) productivity is often adversely disturbed by several abiotic and biotic stresses such as drought, submergence, fungal, bacterial, and nematode oriented biotic diseases and pest like brown plant hopper (BPH) and stem borer (SB). The major biotic stresses such as bacterial leaf blight (BLB), sheath blight (ShB), blast, brown spot (BS), false smut (FS), brown plant hopper (BPH), yellow stem borer (YSB), and gall midge (GM) play crucial roles in decreasing the productivity and quality of rice grains. Among the several breeding procedures and various control measures available for mitigating the biotic stresses/factors, the host plant resistance is most effective, economic and eco-friendly which is basically developed by traditional breeding approaches. The related species of rice and wild sources are important for identification of many resistance genes/QTLs, which are successfully introgressed or deployed or pyramided in numerous breeding lines through resistance breeding program and various molecular approaches. In this chapter, an inclusive valuation of the conventional and molecular approaches for mitigating the biotic stresses in rice by imparting major resistance sources has been presented.
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Helminthosporium oryzae, the causal organism of bacterial leaf spot (BLS) has brought a tremendous loss of rice crop in the field. Rice seedlings of four commercial varieties (Nayab basmati, Kiran 434, Super basmati, and Pak 386) were screened against BLS in the field by using a randomized complete block design (RCBD). The present experiment was encompassed the evaluation of fermented farmyard manure, leaf manure, Boron, and NPK solution against BLS. The effect of different fungicides (Score, Flumax, Melodyduo, and Polyram) was also checked on the mycelial growth of Helminthosporium oryzae in-vitro and in-vivo. The results showed that Pak 386 was highly resistant with 17.22% disease severity and Super Basmati was found moderately resistant with 22.31% disease severity; variety Kisan 434 was found moderately susceptible (24.15%) and Nayab Basmati (24.82%) was susceptible. Among all NPK solutions showed the best results in growth enhancement, plant vigor as well as reduction in disease severity followed by FFYM, boron and leaf manure. Under in-vitro conditions, all the fungicides performed best at 150 ppm in terms of colony growth reduction. The maximum growth inhibition was recorded in Score followed by Flumax, Melodyduo, and Polyram. Score gave a significant reduction in BLS disease severity and maximized the agronomic attributes. The fungicides performed best at 150 ppm in terms of colony growth reduction. The maximum growth inhibition was recorded in Score followed by Flumax, Melodyduo, and Polyram. Score gave a significant reduction in BLS disease severity and maximized the agronomic attributes. Keywords: HBV, HCV, ICT, PCR, Risk factors, Mansehra
Chapter
Rice is major staple food of India, and it needs to be tailored to face the future challenges arising from continuously evolving pests and stresses created by those organisms. The most economically viable and environment friendly management strategy of combating these stresses is exploitation of host plant resistance. The development and availability of an array of robust molecular markers and dense molecular genetic maps in crop plants has made application of marker assisted selection possible for traits governed by major genes and QTL. Deployment of these genes/ QTL through resulted in the development of many biotic stress tolerant varieties in rice in India and around the world especially for stresses like bacterial blight, blast, sheath blight, brown plant hopper, gall midge etc. Many multi-gene pyramided lines were developed through MAS which was otherwise impossible through conventional breeding approach. Recent advancements in genome editing technologies have opened up avenues to expand the dimension of molecular breeding.
The present study investigates the chemical composition of Cyamopsis tetragonoloba (L.) Taub. leaves and fruits extracts and their molecular docking studies as antifungal agents against rice phytopathogenic fungi. The extracts were prepared by using Soxhlet apparatus taking ethyl acetate, ethanol and methanol as solvents. These extracts were characterized by GC-MS analysis and were evaluated for their antifungal potential against Rhizoctonia solani and Drechslera oryzae. Maximum antifungal activity was shown by ethyl acetate fruits extract with minimum EC50 values. All the major compounds in guar extracts were subjected to molecular docking studies against the fungal target protein, i.e. lanosterol 14α- demethylase to find their potential binding mode and binding affinity. Among the six compounds, stigmasterol and γ-sitosterol bound most strongly with the receptor through the involvement of single-residue interactions. Hence, both these sterols present in ethyl acetate fruits extract can be effectively used to control these phytopathogenic fungi.
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Generally, the mycelial growth of B. oryzea was found reduced with an increase in the concentration of ICF 310 (Mancozeb 68% + Hexaconazole 4%) fungicide. Among all the concentrations tested the test fergicide completely inhibites the growth of B.oryzae of 1000 and 1200 ppm cone. Which were on par with each other. Among the various treatments, combined application of ICF 310 as seed treatment and as Foliar spray recorded the minimum brown leaf spot incidence (11.23%). This was followed by combined application of ICF 310 as seed treatment and as foliar spray recorded the minimum brown leaf spot incidence (11.23%). This was followed by combined application of ICF 310 as seed treatment and as foliar spray which recorded the brown spot incidence of 13.43% and the maximum brown spot incidence was observed in untreated control.
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Mosaddeque H.Q.M., Talukder M.I., Islam M.M., Khusrul Amin A.K.M. and Alam M.A. 2008. Screening of Some Restorer and Maintainer Hybrid Rice Lines against Sheath Blight (Rhizoctonia solani). J .Soil .Nature. 2(1): 23-29 An experiment was conducted at the field laboratory of Genetics and Plant Breeding Department, BAU, Mymensingh during July to December, 2000. Forty-four test entries of parental lines of rice with one susceptible (BR 11) and one resistant check (BRRI dhan 29) were screened against sheath blight (Rhizoctonia solani) at maximum tillering and flowering stage in the field. The pathogenicity test was studied in the laboratory. Ten lines were resistant, 31 were moderately resistant and 3 showed moderately susceptible reaction at maximum tillering stage. At flowering stage only 2 lines were resistant, 24 were moderately resistant and 18 lines were moderately susceptible.
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A 1.1-kb DNA fragment containing the coding region of a thaumatin-like protein (TLP-D34), a member of the PR-5 group, was cloned into the rice transformation vector pGL2, under the control of the CaMV 35S promoter. The Indica rice cultivars, ‘Chinsurah Boro II’, ‘IR72’, and ‘IR51500’ were transformed with the tlp gene construct by PEG-mediated direct gene transfer to protoplasts and by biolistic transformation using immature embryos. The presence of the chimeric gene in T0, T1, and T2 transgenic plants was detected by Southern blot analysis. The presence of the expected 23-kDa TLP in transgenic plants was confirmed by Western blot analysis and by staining with Coomassie Brilliant Blue. Bioassays of transgenic plants challenged with the sheath blight pathogen, Rhizoctonia solani, indicated that over-expression of TLP resulted in enhanced resistance compared to control plants.
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As population structure can result in spurious associations, it has constrained the use of association studies in human and plant genetics. Association mapping, however, holds great promise if true signals of functional association can be separated from the vast number of false signals generated by population structure 1,2. We have developed a unified mixed-model approach to account for multiple levels of relatedness simultaneously as detected by random genetic markers. We applied this new approach to two samples: a family-based sample of 14 human families, for quantitative gene expression dissection, and a sample of 277 diverse maize inbred lines with complex familial relationships and population structure, for quantitative trait dissection. Our method demonstrates improved control of both type I and type II error rates over other methods. As this new method crosses the boundary between family-based and structured association samples, it provides a powerful complement to currently available methods for association mapping.
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Individual plants from the first through third backcrosses of the rice sheath blight-resistant cultivar Tetep to the susceptible cultivar Lemont were selected for low infection cushion counts and for resistant-type lesions in the greenhouse. Replicated progeny field tests of selfed plants from each generation were conducted. Correlations between individual backcross plants, rated for number of infection cushions and lesion type, and disease ratings of their field-tested progeny were relatively low but resistance levels were maintained (.)
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One method for confirming the existence of quantitative trait loci (QTLs) is to identify loci of similar location and effect in multiple populations and/or environments. The literature contains two prior publications reporting the location of QTLs affecting resistance to sheath blight (SB) disease in rice (Oryza sativa L.), but lack of agreement between QTLs in the studies left all 12 unconfirmed, limiting the potential of marker-assisted selection of this trait with worldwide importance. The earlier linkage analyses were imprecise due to heterozygosity, segregation, and limited plot size and replication. We evaluated a replicated set of pure-breeding recombinant inbred lines (RILs) to increase reliability of the quantitative disease data and in turn improve accuracy of the QTL mapping. The RILs were F(2:10) descendants from an early-generation 'Lemont' x 'Teqing' population wherein SB resistance QTLs (SB-QTLs) were first identified. The present study confirmed the location and effect of six SB-QTLs, confirmed the existence but not the specific location of another, and identified eight new loci. Three of the confirmed QTLs were also found to be independent from undesirable plant height and maturity effects. This research demonstrated the importance of using replicated phenotypic data for reliably establishing the identity and effect of putative QTLs for complex traits such as SB resistance. Further marker development to facilitate marker-assisted selection of these three SB-QTLs is warranted.
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Recent advances in understanding molecular and physiological mechanisms of abiotic stress responses, along with breakthroughs in molecular marker technologies, have enabled the dissection of the complex traits underlying stress tolerance in crop plants. Quantitative trait loci (QTLs) controlling different abiotic stress traits form the basis for a precise marker-assisted backcrossing (MABC) strategy to rapidly transfer tolerance loci into high-yielding, but stress-sensitive varieties. Case studies are presented to demonstrate the progress and potential for MABC programs to develop rice varieties with increased tolerance to flooding, salinity, phosphorus deficiency and drought, amongst others. Future opportunities exist for employing association genetics for more efficient allele mining for abiotic stress tolerance from germplasm collections, as well as leveraging the power of bioinformatics and genomics data for more efficient trait dissection and use in breeding. Plant breeders now have a wealth of information and tools available to tackle these serious constraints posed by abiotic stresses, with the promise of delivering stable, high yielding varieties, able to thrive in the increasingly degrading soils and the ominously changing environment. Keywordsabiotic stresses–association mapping– Oryza sativa L.–QTLs–rice
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Sheath blight, caused by Rhizoctonia solani, is one of the most important diseases of rice. Despite extensive searches of the rice germ plasm, the major gene(s) which give complete resistance to the fungus have not been identified. However, there is much variation in quantitatively inherited resistance to R. solani, and this type of resistance can offer adequate protection against the pathogen under field conditions. Using 255 F4 bulked populations from a cross between the susceptible variety 'Lemont' and the resistant variety 'Teqing', 2 years of field disease evaluation and 113 well-distributed RFLP markers, we identified six quantitative trait loci (QTLs) contributing to resistance to R. solani. These QTLs are located on 6 of the 12 rice chromosomes and collectively explain approximately 60% of the genotypic variation or 47% of the phenotypic variation in the 'Lemont'x'Teqing' cross. One of these resistance QTLs (QSbr4a), which accounted for 6% of the genotypic variation in resistance to R. solani, appeared to be independent of associated morphological traits. The remaining five putative resistance loci (QSbr2a, QSbr3a, QSbr8a, QSbr9a and QSbr12a) all mapped to chromosomal regions also associated with increased plant height, three of which were also associated with QTLs causing later heading. This was consistent with the observation that heading date and plant height accounted for 47% of the genotypic variation in resistance to R. solani in this population. There were also weak associations between resistance to R. solani and leaf width, which were likely due to linkage with a QTL for this trait rather than to a physiological relationship.
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Transgenic rice was developed from both calli and immature embryos of popular cultivar ‘Swarna’ with a rice chitinase gene (chi11) by particle gun bombardment. Homozygous dihaploid transgenics were produced in less than a year through the anther culture of primary transgenics. Stable integration and expression of the chi11 transgene were confirmed by Southern and western analyses, respectively of primary as well as anther culture-derived dihaploid transgenics. The homozygous transgenics with functional transgene and varied levels of chitinase activity showed enhanced resistance to sheath blight fungus. The bioassay data were correlated with the molecular and biochemical results.
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A series of experiments was conducted where a range of injuries due to rice pests (pathogens, insects, and weeds) was manipulated simultaneously with a range of production factors (fertilizer input, water supply, crop establishment method, variety) in different seasons and years. These factors were chosen to represent lowland rice production situations characterized in surveys conducted in tropical Asia and their corresponding range of attainable yield. Experiments complemented one another in exploring the response surface of rich yields to yield-limiting and yield-reducing factors. The resulting experimental data base consisted of 445 individual plots and involved 11 manipulated injuries in a multiple regression model involving factors generated by principal component analysis on injuries that adequately described the variation in actual yield. One major finding was that some (attainable yield x injury factors) interactions significantly contributed to the description of variation in actual yield, indicating that some injuries (or their combinations) had a stronger or weaker yield-reducing effect, depending on the level of attainable yield. For instance, yield losses due to sheath blight, weed infestation, and rice tungro disease tend to increase, remain stable, and decrease, respectively, with increasing attainable yields. Back-computations using the principal component regression model estimated yield losses caused by individual injuries, using the mean injury levels in a population of farmers' fields surveyed across tropical Asia. The results indicate that sheath blight, brown spot, and leaf blast are diseases that cause important losses (between 1 10%) regionally. Among the insect injuries, only white heads caused by stem borers appear of relevance (2.3%) yield losses)... (D'après résumé d'auteur)
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A 1.1 kb rice genomic DNA fragment, containing a chitinase gene under the control of the CaMV 35S promoter, was cloned into the rice transformation vector pGL2. After transformation of Indica rice protoplasts in the presence of polyethyleneglycol, plants were regenerated. The presence of the chimeric chitinase gene in T0 and T1 transgenic rice plants was detected by Southern blot analysis. Western blot analysis of transgenic plants and their progeny revealed the presence of two proteins with apparent molecular weights of 30 and 35 kDa that reacted with the chitinase antibody. Progeny from the chitinase-positive plants were tested for their resistance to the sheath blight pathogen, Rhizoctonia solani. The degree of resistance displayed by the transgenic plants to this pathogen correlated with the level of chitinase expression.
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Rice production is subject to increasing environmental and social constraints. Agricultural labor and water, which are key resources for rice production, illustrate this point. Nearly all rice-producing countries face reduced availability of agricultural water and shortage of farm labor. Plant pathologists should be concerned with such large-scale evolutions because these global drivers have an impact on not only the rice production system but also on the individual field and single-rice-plant levels. These concerns are closely associated with the long-term sustainability and environmental consequences of the intensification of agricultural systems brought about by problems of feeding a rapidly growing human population. Furthermore, genetic diversity in rice production has been reduced, thus inducing frequent disease epidemics and pest outbreaks. Looking ahead, we need to realize the need to maintain the diversity and yet retain the high productivity of the system. Natural resources, including genetic resources, are not infinitely abundant. We have to be efficient in utilizing genetic resources to develop durable resistance to rice diseases. Developing resistance is an important first step in tackling the disease problem, but it is not the only step available to achieve durability. Deployment of resistance must be considered in conjunction with development of host plant resistance. To attain durability, we need a better understanding of the coevolution process between the pathogen and the host resistance gene. Our target is an integrated gene management approach for better disease control and more effective utilization of genetic resources. Plant pathology, as an applied science, derives its strengths from various disciplines. To do the job right, we need a better understanding of the pathosystems, the epidemiology, and the coevolution process between the pathogen and the host resistance gene. The challenge, as pointed out by pioneers in our profession, is to prove the usefulness and the relevance of our research. Thus, we need to strike a balance between mission-oriented and fundamental research and make sure that our profession is (still) useful in the information technology and genomic era. We believe that a gene-based and a resource-based disease management approach should allow us to incorporate these new scientific developments. However, we do need to incorporate the new science for fundamental research to solve practical problems of rice production.
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Agrobacterium-mediated transformation of rice was done using the binary vector pNSP3, harbouring the rice chitinase (chi11) gene under maize ubiquitin promoter and the tobacco β-1,3-glucanase gene under CaMV 35S promoter in the same T-DNA. Four of the six T0 plants had single copies of complete T-DNAs, while the other two had complex integration patterns. Three of the four single-copy lines showed a 3:1 segregation ratio in the T1 generation. Northern and western blot analyses of T1 plants revealed constitutive expression of chitinase and β-1,3-glucanase genes. Homozygous T2 plants of the single-copy lines CG20, CG27 and CG53 showed 62-, 9.6- and 11-fold higher chitinase activity over the control plants. β-1,3-Glucanase activity was 1.1- to 2.5-fold higher in the transgenic plants. Bioassay of homozygous T2 plants of the three single-copy transgenic lines against Rhizoctonia solani revealed a 60% reduction in sheath blight Disease Index in the first week. The Disease Index increased from 61.8 in the first week to 90.6 in the third week in control plants, while it remained low (26.8–34.2) in the transgenic T3 plants in the corresponding period, reflecting the persistence of sheath blight resistance for a longer period.
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The goal of this project is to identify critical genes for the control of sheath blight disease. To this end, an in vitro method to examine interactions of rice with the rice sheath blight pathogen Rhizocotnia solani was developed. The initial analysis of R. solani isolates from Arkansas rice fields revealed three classes of most virulent, mod- erately virulent, and weakly virulent isolates. Differential responses of rice cultivar leaves toward these pathogen isolates were detected using a novel detached-leaf method. Characterized R. solani isolates are being used to identify differentially ex- pressed genes.
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Sheath blight, Rhizoctonia solani (Kuhn), is the most economically important disease in the Midsouth rice (Oryza sativa L.)-producing area of the USA. The use of excessive N fertilizer has been observed to increase sheath blight damage to rice, but the effect of specific N application rates and timing on sheath blight damage and the resulting rice grain yield are unknown. The primary objective of this study was to examine the effect of N application rate and time on rice grain yield and development of sheath blight. A 3-yr study contained 20 treatments with all possible combinations of two N fertilization methods (single preflood and two-way split), five N fertilizer rates (0-250 kg N ha(-1)), and two rates of azoxystrobin {methyl (E)-2-[2-[6-(2-cyanophenoxy)pyrimidin-4-yloxy]phenyl]-3-methoxyacrylate} fungicide (0 and 0.22 kg ha(-1)). Application of azoxystrobin, averaged across all other treatment factors, produced a mean rice grain yield of 8740 kg ha(-1), which was 16% greater than treatments not receiving azoxystrobin fungicide. Relative lesion height (RLH), averaged across N fertilizer treatments, increased with time when no fungicide was applied. Early-season application of fungicide prevented disease development from 4 to 6 wk. Fungicide application suppressed RLH but did not alter the N rates required to produce maximum grain yields. Application of high preflood N fertilizer rates, regardless of method, increased the initial RLH during early reproductive growth but had little effect on the RLH after heading. The effect of RLH on grain yield showed similar patterns as that found for total N rate on grain yield. The N rates required to produce maximum yields also tend to enhance early-season sheath blight.
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Bialaphos resistant rice plants expressing a bar gene under the control of the maize ubiquitin promoter which were inoculated with mycelia of the sheath blight disease pathogen, Rhizoctonia solani, and subsequently treated with the herbicide were completely protected from symptomatic infection. Substantial suppression of sheath blight symptoms was also recorded when bialaphos was applied to transgenic plants which had been infected with R. solani two days before herbicide treatment. It may therefore be possible to design new agronomic strategies for the simultaneous control of weeds and fungal pathogens in fields of transgenic plants expressing a bar gene.
Chapter
Chitinases (EC 3.2.1.14) are ubiquitous enzymes of bacteria, fungi, animals, and plants. They hydrolyze the β-1,4-linkage between N-acetylglucosamine residues of chitin, a structural polysaccharide of the cell wall of many fungi and of the exoskeleton of invertebrates. The development of research in plant defense mechanisms has led to a rapid and steady interest in chitinases, since they were the first pathogeninduced proteins whose function was identified. Their substrate is present in the cell wall of many fungi, as well as in insects and nematodes, which are major pathogens and pests of crop plants.
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Rice (Oryza sativa L.) productivity is affected by several biotic and abiotic stresses. The genetic variability for some of these stresses is limited in the cultivated rice germplasm. Moreover, changes in insect biotypes and disease races are a continuing threat to increased rice production. There is thus an urgent need to broaden the rice gene pool by introgressing genes for such traits from diverse sources. The wild species of Oryza representing AA, BB, CC, BBCC, CCDD, EE, FF, GG and HHJJ genomes are an important reservoir of useful genes. However, low crossability and limited recombination between chromosomes of cultivated and wild species limit the transfer of such genes. AT IRRI, a series of hybrids and monosomic alien addition lines have been produced through embryo rescue following hybridization between rice and several distantly related species. Cytoplasmic male sterility and genes for resistance to grassy stunt virus and bacterial blight have been transferred from A genome wild species into rice. Similarly, genes for resistance to brown planthopper, bacterial blight and blast have also been introgressed across crossability barriers from distanly related species into rice. Some of the introgressed genes have been mapped via linkage to molecular markers. One of the genes Xa-21 introgressed from O. longistaminata has been cloned and physically mapped on chromosome 11 of rice using BAC library and flourescence in-situ hybridization. RFLP analysis revealed introgression from 11 of the 12 chromosomes of C genome species into rice. Introgression has also been obtained from other distant genomes (EE, FF, GG) into rice and in majority of the cases one or two RFLP markers were introgressed. Reciprocal replacement of RFLP alleles of wild species with the alleles of O. sativa indicates alien gene transfer through crossing over. The rapid recovery of recurrent phenotypes in BC2 and BC3 generations from wide crosses is an indication of limited recombination. Further cytogenetic and molecular investigations are required to determine precisely the mechanism of introgression of small chromosome segments from distant genomes in the face of limited homoeologous chromosome pairing. Future research should focus on enhancing recombination between homoeologous chromosomes. Introgression of QTL from wild species should be attempted to increase the yield potential of rice.
Article
This chapter reviews the progress made in developing rice that is resistant to diseases and insects. Among cereal crops, rice is the host of the largest number of diseases and insect pests. These cause serious yield loss annually. The magnitude of loss caused by diseases and insects, increases as the level of rice production per unit area increases. The chapter discusses the nature of the disease or insect, its distribution, genetic variability of the pathogen, host resistance, genetics of resistance, and breeding for resistance. Fungal diseases attack the plant foliage, stems, roots, leaf sheath, or inflorescence, and grains. Four fungal diseases: blast, sheath blight, brown spot, and narrow brown leaf spot; two bacterial diseases: bacterial blight and bacterial streak; and five virus diseases: tungro, grassy stunt, stripe, dwarf, and hoja blanca have been discussed in the chapter. To minimize yield loss from disease and insect attacks, varieties with multiple resistances to most major diseases and insects are required. Also, a systematic international survey of races or biotypes of major diseases and insects should be carried out with the use of differential varieties.
Chapter
Rice (Oryza sativa L.) productivity is affected by several biotic and abiotic stresses. The genetic variability for some of these stresses is limited in the cultivated rice germplasm. Moreover, changes in insect biotypes and disease races are a continuing threat to increased rice production. There is thus an urgent need to broaden the rice gene pool by introgressing genes for such traits from diverse sources. The wild species of Oryza representing AA, BB, CC, BBCC, CCDD, EE, FF, GG and HHJJ genomes are an important reservoir of useful genes. However, low crossability and limited recombination between chromosomes of cultivated and wild species limit the transfer of such genes. At IRRI, a series of hybrids and monosomic alien addition lines have been produced through embryo rescue following hybridization between rice and several distantly related species. Cytoplasmic male sterility and genes for resistance to grassy stunt virus and bacterial blight have been transferred from A genome wild species into rice. Similarly, genes for resistance to brown planthopper, bacterial blight and blast have also been introgressed across crossability barriers from distanly related species into rice. Some of the introgressed genes have been mapped via linkage to molecular markers. One of the genes Xa-21 introgressed from O. longistaminata has been cloned and physically mapped on chromosome 11 of rice using BAC library and flourescence in-situ hybridization. RFLP analysis revealed introgression from 11 of the 12 chromosomes of C genome species into rice. Introgression has also been obtained from other distant genomes (EE, FF, GG) into rice and in majority of the cases one or two RFLP markers were introgressed. Reciprocal replacement of RFLP alleles of wild species with the alleles of O. sativa indicates alien gene transfer through crossing over. The rapid recovery of recurrent phenotypes in BC2 and BC3 generations from wide crosses is an indication of limited recombination. Further cytogenetic and molecular investigations are required to determine precisely the mechanism of introgression of small chromosome segments from distant genomes in the face of limited homoeologous chromosome pairing. Future research should focus on enhancing recombination between homoeologous chromosomes. Introgression of QTL from wild species should be attempted to increase the yield potential of rice.
Chapter
The host range of Rhizoctonia solani is so wide, and the damage caused to specific crops is so variable, that a case study may provide an appropriate approach to the general issue of measuring crop losses at the field level. Rice sheath blight provides a good example because the symptoms of the disease are fairly representative of symptoms caused by R. solani to a wide range of both monocots and dicots.
Article
Only partial resistance is available for sheath blight, the second most important disease of rice (Oryza sativa L.) worldwide. This partial resistance has been considered to be polygenic. The partial resistance of the cultivars Jasmine 85 (J-85) and Teqing (TQNG) was studied by evaluating the resistance of F1, F2, F3, F4, and backcross F1 generations of crosses between the resistant parents and the susceptible cultivars Maybelle (MBLE) and Cypress (CPRS). F1 plants from the crosses were resistant. Segregating F2 populations from both crosses showed ratios of 3:1 resistant/susceptible plants. Segregating backcross F1 populations showed a ratio of 1:1 resistant/susceptible plants when the F1 was crossed to a susceptible parent and no segregation occurred when the F1 was crossed to a resistant parent. These results were consistent with the partial resistance from the two resistant cultivars being controlled by single dominant genes. When the resistant cultivars were crossed, the segregating F2 population showed a 15:1 resistant/susceptible ratio. The results suggested that the two resistant parents each possessed a nonallelic dominant major resistance gene that segregated independently. Some of the F4 lines from this cross appeared to have both resistance genes and a higher level of resistance than either resistant parent. This suggests that major genes conferring high levels of partial resistance to sheath blight may be incorporated together into lines to give near complete resistance. This makes the identification of major genes for partial resistance to sheath blight critically important to rice breeding programs.
Article
Sheath blight (Rhizoctonia solani) of rice (Oryza sativa) is associated with intensive and high-input production systems. The effect of sheath blight on yield, the effect of high nitrogen (N) rate on sheath blight incidence, and the stages of crop that are most susceptible to the disease and vulnerable to yield losses were investigated. Grain yield data from a long-term experiment showed a quadratic polynomial curve in response to N input. An initial increase in N supply corresponded to an increase in yield, but at the highest N level, a reduction in yield was observed. Sheath blight incidence also increased with increasing N level. The estimated yield reduction from sheath blight in plots receiving the highest N rate ranged from 20 to 42% in artificially inoculated plots. The highest sclerotial population recorded was only 2.02 sclerotia per 500 g of oven-dried soil or about 1.23 sclerotia per liter of puddled paddy soil. This low sclerotial density in our studies suggested that sclerotia may not be the primary source of inoculum in a tropical lowland rice system. Crop residues colonized by the pathogen may play an important role in sheath blight epidemics in this intensive rice production system. Screenhouse and field experiments indicated significant yield losses when sheath blight infection started at panicle initiation, booting, or flowering. The effect of sheath blight on yield resulted primarily from a reduction in mean seed weight and a lower percentage of filled spikelets. No yield loss or decrease in yield components was observed when infection started at tillering or grain filling.
Article
Forward genetics begins with a mutant phenotype and asks the question “What is the genotype?” that is, what is the sequence of the mutant gene causing the altered phenotype? Reverse genetics begins with a mutant gene sequence and asks the question “What is the resulting change in phenotype
Article
Increasing world population, shrinking cultivable rice (Oryza sativa L.) land area, water scarcity and excess, evolution of new biotypes of pests and diseases, and climate change pose serious challenges to rice breeders to increase production and productivity with multiple resistances to biotic and abiotic stresses. Recent advances in rice genomics research and completion of the rice genome sequence have made it possible to identify and map precisely a number of genes through linkage to DNA markers. Noteworthy examples of some of the genes tightly linked to markers are resistance to or tolerance of blast, bacterial blight, virus diseases, brown planthopper (Nilaparvata lugens), drought, submergence, salinity, and low temperature and improved agronomic and grain quality traits. Marker-assisted selection (MAS) can be used for monitoring the presence or absence of these genes in breeding populations and can be combined with conventional breeding approaches. Marker-assisted backcross breeding has been used to effectively integrate major genes or quantitative trait loci with large effect into widely grown varieties. Pyramiding different resistance genes using MAS provides opportunities to breeders to develop broad-spectrum resistance for diseases and insects. The use of cost-effective DNA markers derived from the fine mapped position of the genes for important agronomic traits and MAS strategies will provide opportunities for breeders to develop high-yielding, stress-resistant, and better-quality rice cultivars.