[show abstract][hide abstract] ABSTRACT: Finger millet blast caused by Magnaporthe grisea (anamorph: Pyricularia grisea) is a great threat to finger millet production worldwide. Genetic diversity and population structure of 72 M. grisea isolates collected from finger millet (56), foxtail millet (6), pearl millet (7) and rice (3) from major crop growing areas in India was studied using 24 SSR markers. None of the SSRs detected polymorphism in the M. grisea isolates from pearl millet. Seventeen SSR markers were polymorphic in the 65 non pearl millet isolates and detected 105 alleles, of which one was rare, 83 common, 9 frequent and 12 most frequent. A model-based population structure analysis of the genomic data identified two distinct populations with varying levels of ancestral admixtures among the 65 M. grisea isolates. Analysis of molecular variance (AMOVA) indicated that 52% of the total variation among the isolates used in this study was due to differences between the pathogen populations adapted to different hosts, 42% was due to differences in the isolates from the same host, and the remaining 6% due to heterozygosity within isolates. High genetic variability present in M. grisea isolates calls for the continuous monitoring of M. grisea populations anticipating blast resistance breakdown in finger millet cultivars grown in India.
[show abstract][hide abstract] ABSTRACT: Blast caused by Pyricularia grisea [teleomorph: Magnaporthe grisea] is an economically important and widespread disease of finger millet in the world. Host resistance is the most economical and effective means of combating this disease as finger millet is predominantly grown by resource-poor and marginal farmers. At the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), we evaluated a finger millet mini-core collection of 80 germplasm accessions (about 1 % of the total germplasm collection representing major trait variability) for blast resistance both in the field and greenhouse. Field evaluation was done using a refined screening technique that included new improved rating scales for leaf, neck and finger infection. Sixty six of the 80 accessions showed combined resistance to leaf, neck and finger blast in two seasons (2009 and 2010) of field screening. A highly significant and positive correlation was found between neck and finger blast ratings (r = 0.92), whereas small but significant correlations were found between leaf blast and neck blast (r = 0.25) and between leaf blast and finger blast (r = 0.30). These accessions were also screened for leaf blast resistance in the greenhouse by artificial inoculation of seedlings to confirm field observations. Fifty-eight of the 80 accessions were resistant to leaf blast in the greenhouse screen as well. These resistant accessions represented one wild (africana) and four cultivated races (vulgaris, plana, elongate and compacta) of finger millet that originated from 13 countries in Asia and Africa and exhibited considerable diversity for agronomic traits, such as maturity period, plant height and panicle type. These blast resistant accessions from the mini-core collection would be useful in finger millet disease resistance breeding programs.
European Journal of Plant Pathology 01/2013; 135:299-331. · 1.61 Impact Factor
[show abstract][hide abstract] ABSTRACT: Effective management of blast disease in finger millet can best be achieved through host-plant resistance. In this study, field screening technique was developed and core collection evaluated to identify sources of resistance to blast. The field screening technique involved: use of systematic susceptible checks after every four test rows, artificial spray inoculation at pre-flowering stage with an aqueous conidial suspension (1×105 spores ml-1) of Magnaporthe grisea fm strain multiplied on oatmeal agar medium at 27±1ºC for 10 days, and maintaining high humidity and leaf wetness through sprinkler irrigation twice a day for 4 weeks following inoculation. Neck blast was recorded on a 1–5 scale and finger blast as severity percentage on all the tillers of selected 10 plants in a row at physiological maturity. The finger millet core collection consisting of 622 accessions was evaluated for neck and finger blast resistance. Among the core collection, 402 accessions were found resistant to neck blast, 436 to finger blast and 372 had combined resistance to both the diseases. Blast resistant accessions belonged to one wild and four cultivated races of finger millet that originated from 19 countries indicating the wide geographical diversity among resistant accessions. Most of the accessions from Asian origin were susceptible to neck and finger blasts while, those from African origin were resistant. A significant strong positive correlation (r = 0.85, P<0.0001) was found between neck blast and finger blast ratings. Core collection accessions with stable resistance to blast would be useful for finger millet breeding programs.
Indian Journal of Plant Protection. 07/2012; 40(1):45-51.
[show abstract][hide abstract] ABSTRACT: Fusarium species are dominant within the sorghum grain mold complex. Some species of Fusarium involved in grain mold complex produce mycotoxins, such as fumonisins. An attempt was made to identify Fusarium spp. associated with grain mold complex in major sorghum-growing areas in India through AFLP-based grouping of the isolates and to further confirm the species by sequencing part of α-Elongation factor gene and comparing the sequences with that available in the NCBI database. The dendrogram generated from the AFLP data clustered the isolates into 5 groups. Five species of Fusarium--F. proliferatum, F. thapsinum, F. equiseti, F. andiyazi and F. sacchari were identified based on sequence similarity of α-Elongation factor gene of the test isolates with those in the NCBI database. Fusarium thapsinum was identified as predominant species in Fusarium--grain mold complex in India and F. proliferatum as highly toxigenic for fumonisins production. Analysis of molecular variance (AMOVA) revealed 54% of the variation in the AFLP patterns of 63 isolates was due to the differences between Fusarium species, and 46% was due to differences between the strains within a species.
[show abstract][hide abstract] ABSTRACT: Metalaxyl (Apron 35WS) as a seed treatment has been used extensively to control downy mildew (caused by Sclerospora graminicola) in pearl millet in India. However, the extent of disease control has varied across cultivars, years and locations. We investigated
the effects of fungicide dosage, storage time and storage temperature of metalaxyl-treated seed on disease incidence in four
pearl millet lines having varying levels of resistance. A linear relationship was found between fungicide dosage (0.5, 1.5
and 2g a.i. kg−1 seed) and reduction in disease incidence up to 40days after emergence in all the lines. The normal fungicide dose (2g a.i.
kg−1 seed) protected the crop for up to 20, 40 and 50days after emergence in highly susceptible (7042S), moderately susceptible
(4042R), and moderately resistant (ICMP 451) lines, respectively. However, the quarter and half the normal dosage of fungicide
provided protection only up to 20days after emergence in 7042R and 40days after emergence in ICMP 451. Storage duration
of metalaxyl-treated seed (2g a.i. kg−1) up to 9months at 25 ± 2°C did not affect fungicide efficacy. Storage temperatures (5, 25 and 40°C) and duration (30, 60
and 90days) of metalaxyl-treated seed (2g a.i. kg−1) showed differential effects in two pearl millet lines 7042S and 843B with downy mildew incidence being significantly lower
in 7042S than in 843B. Metalaxyl-treated seed of 7042S and 843B stored at 40°C for different durations showed phytotoxic effects
and it was more pronounced in 843B stored for 60 and 90days where seed germination was inhibited in pot soil.
European Journal of Plant Pathology 01/2011; 129(2):353-359. · 1.61 Impact Factor
[show abstract][hide abstract] ABSTRACT: In this study a total of 167 isolates collected from different food materials (68.8% from sorghum and the remaining from various
other food materials) were assayed by PCR for amplification of the tri 5 gene present in trichothecene-producing Fusaria. Amplification of the tri 5 fragment was observed in 45 isolates (39 isolates from sorghum and 6 isolates from vegetables). Isolates found positive for
presence of the tri 5 gene were classified into different morphological groups based on their cultural and conidial characters; 11 of the tri 5 positive isolates from moldy grains of sorghum, one from each morphology group were selected for further analyses. Five deoxynivalenol
producers and three deoxynivalenol and Fusarenon-X producers were detected by analysing culture filtrates of the 11 isolates
using GC-MS. One isolate each were identified as producers of NIV alone, or NIV along with DON or DAS toxins. Identification
of these isolates to the species level was carried out using spore morphology and sequence comparison of the translation elongation
factor 1-alpha (EF-1α) gene against the database as well as using phylogenetic analyses. The isolates were identified as Fusarium
proliferatum (6), F. nelsonii (2), F. equiseti (1), F. thapsinum (1) and F. sacchari (1). Amplified Fragment Length Polymorphism (AFLP) based grouping clustered the isolates of same species together. This is
the first detailed study of trichothecene production by Fusarium spp. associated with sorghum grain mold in India and the identification of F. nelsonii and F. thapsinum as producers of trichothecenes.
World Journal of Microbiology and Biotechnology 01/2011; 27(4):981-989. · 1.26 Impact Factor
[show abstract][hide abstract] ABSTRACT: Breeding for resistance to grain mold, an economically important disease of sorghum, has been only partially successful. Hybrid technology is well developed in sorghum due to availability of the cytoplasm male sterility (CMS) system and at present almost all commercial hybrids are based on the A1 CMS system. To compare the available alternate CMS systems for grain mold resistance, 72 hybrids were produced by crossing 36 A-lines (six CMS systems; A1, A2, A3, A4(M), A4(G), A4(VZM) each in six nuclear backgrounds) with two common restorers, and were evaluated during the 2006 and 2007 rainy seasons in grain mold nursery at ICRISAT. Data analyses indicated influence of cytoplasm on the responses of hybrids to grain mold infection as measured by panicle grain mold resistance (PGMR) score. The A1 cytoplasm seemed to contribute to grain mold resistance followed by A4(VZM) and A2 cytoplasms. The A4(M) cytoplasm had superior general combining ability (GCA) effects while the A1 and A4(VZM) cytoplasm based hybrids had superior specific combining ability (SCA) effects on the PGMR score. Almost all hybrids had significant mid-parent heterosis. The A1 cytoplasm is the best suited for the development of sorghum hybrids for the rainy season adaptation with grain mold resistance. However, use of alternate cytoplasms (A2 and A4(VZM)) for hybrid development will not increase susceptibility to grain mold in commercial grain production.Highlights► Effect of six CMS systems on grain mold resistance is studied in iso-nuclear hybrids. ► The A1 cytoplasm is best suited for the development of sorghum hybrids with grain mold resistance. ► The A2 and A4(VZM) cytoplasms can be exploited without increasing the risk of grain mold. ► The A4(M) cytoplasm contributed to superior GCA effects while the A1 and A4(VZM) contributed to superior SCA effects. ► Significant heterosis is reported on all CMS systems based hybrids.
[show abstract][hide abstract] ABSTRACT: On-farm surveys were conducted in the Uttar Pradesh (India) during the two rainy seasons 2007 and 2008 to monitor pearl millet (Pennisetum glaucum) downy mildew incidence. Twenty-one isolates of Sclerospora graminicola, the pearl millet downy mildew pathogen, were collected from different hybrid cultivars. These isolates were established on seedlings of the highly susceptible line 7042S grown in the greenhouse and were characterized for their virulence diversity using a set of seven host differential lines. Quantitative differences in virulence among pathogen isolates were determined by calculating virulence index (percent disease incidence × latent period-1). Results were submitted to cluster analysis using the Average Linkage method to determine similarity among pathogen isolates. The two highly virulent isolates, Sg 492 from Aligarh and Sg 510 from Badaun, representing geographically diverse locations were selected for use in greenhouse screening of pearl millet breeding lines.
JOURNAL OF PLANT PATHOLOGY 01/2011; 93(1):71-78. · 0.69 Impact Factor
[show abstract][hide abstract] ABSTRACT: Genotypic diversity among 46 isolates of Sclerospora graminicola collected from seven states in India during 1992–2005 was determined through pathotyping and AFLP analysis. A high level of variation was observed among the isolates for downy mildew incidence, latent period and virulence index. Based on the reaction on a set of nine pearl millet lines, 46 isolates were classified in 21 pathotypes. Quantitative differences in virulence levels of the test isolates were assessed by calculating the virulence index (disease incidence × latent period). A dendrogram generated by the average linkage cluster analysis of virulence index clustered the 46 isolates into eight groups. Region-specific grouping of five isolates from Gujarat and six from Rajasthan was observed within two distinct groups. Temporal variation was also observed among the isolates collected from the same location and same host over the years. A total of 297 bands were scored following selective amplification with three primer combinations E-TT/M-CAG, E-AT/M-CAG and E-TG/M-CAT and all of them were polymorphic. Cluster analysis of AFLP data clustered the test isolates into seven groups. Analysis of molecular variance indicated that variation in the S. graminicola populations was largely due to differences among the isolates within the states.
Archives of Phytopathology and Plant Protection 01/2010; 43(6):538-551.
[show abstract][hide abstract] ABSTRACT: Once considered a minor disease of pearl millet,incidence of blast disease caused by Pyricularia grisea,has increased at an alarming rate in the recent past,particularly on commercial hybrids in several states ofIndia. The disease can be best managed through hostplant resistance. In this study, attempts were made todevelop the field and greenhouse screening techniquesand screen some elite hybrid parental lines to identifyresistance to this disease. The field screening techniqueinvolved the use of a highly susceptible line as an infectorrow grown after every four test rows, artificial sprayinoculation of 30-day-old plants using P. grisea sporesuspension (1 × 105 spores ml-1) and maintaining highhumidity (>90% RH) through perfo-irrigation for 2weeks following inoculation. The greenhouse screeningtechnique involved spray inoculation of 15-day-oldpotted seedlings with P. grisea spore suspension andmaintaining moderate temperature (25±1°C) and highhumidity through a misting system for 10 days afterinoculation. In all, 211 elite hybrid parental lines,including 126 designated B-lines, 20 designated R-linesand 65 potential R-lines were evaluated for blastresistance in the disease nursery. Forty-five linesidentified as blast resistant (score ≤3.0 on 1–9 scale)were further screened through greenhouse screeningtechnique. Twenty-five (8 designated B-lines, 3designated R-lines and 14 potential R-lines) of the 45lines were found resistant to blast under greenhouse. Allof these 25 foliar blast resistant lines were also resistantto downy mildew under field conditions. These resistantlines would be useful in breeding blast resistant pearlmillet hybrids.
[show abstract][hide abstract] ABSTRACT: Rust caused by Puccinia substriata var indica is one ofthe major diseases affecting both forage and grainproduction in pearl millet, particularly in the postrainycool season (rabi) crop. The disease can be best managedthrough host plant resistance. In all, 214 advancedbreeding lines, including 126 designated B-lines, 23designated R-lines and 65 potential R-lines wereevaluated for rust resistance in the disease nursery duringthe postrainy season 2008–09 under natural epiphytoticconditions. Eight lines (1 B-line, 7 R-lines) that showedresistance (≤10% rust severity) in the field screen wereevaluated in the greenhouse by artificial inoculation ofpotted seedlings to confirm their resistance. One B-line(ICMB 96222) and three R-lines (ICMR 0699, ICMP451-P8 and ICMP 451-P6) were resistant while the otherfour R-lines were susceptible. The four confirmedresistant lines could be useful resistance sources forbreeding rust resistant hybrid parental lines and theirhybrids.