Phytopathology (PHYTOPATHOLOGY)

Publisher: American Phytopathological Society, American Phytopathological Society

Journal description

Phytopathology is the premier international journal of fundamental research regarding plant diseases, the agents that cause them, their spread, the losses they cause, and measures to control them. Subject areas include analytical and theoretical plant pathology, bacteriology, biochemistry and cell biology, biological control, disease control and pest management, ecology and population biology, epidemiology, etiology, genetics and resistance, mycology, nematology, plant stress and abiotic disorders, postharvest pathology and mycotoxins, techniques, and virology.

Current impact factor: 3.12

Impact Factor Rankings

2016 Impact Factor Available summer 2017
2014 / 2015 Impact Factor 3.119
2013 Impact Factor 2.746
2012 Impact Factor 2.968
2011 Impact Factor 2.799
2010 Impact Factor 2.428
2009 Impact Factor 2.223
2008 Impact Factor 2.192
2007 Impact Factor 2.377
2006 Impact Factor 2.195
2005 Impact Factor 2.049
2004 Impact Factor 2.222
2003 Impact Factor 2.45
2002 Impact Factor 2.22
2001 Impact Factor 2.126
2000 Impact Factor 2.145
1999 Impact Factor 2.632
1998 Impact Factor 2.39
1997 Impact Factor 2.365
1996 Impact Factor 2.339
1995 Impact Factor 2.378
1994 Impact Factor 2.222
1993 Impact Factor 2.273
1992 Impact Factor 2.008

Impact factor over time

Impact factor
Year

Additional details

5-year impact 3.33
Cited half-life >10.0
Immediacy index 0.53
Eigenfactor 0.01
Article influence 0.95
Website Phytopathology website
Other titles Phytopathology
ISSN 0031-949X
OCLC 1762372
Material type Periodical
Document type Journal / Magazine / Newspaper

Publisher details

American Phytopathological Society

  • Pre-print
    • Author can archive a pre-print version
  • Post-print
    • Author cannot archive a post-print version
  • Conditions
    • On pre-print servers, arXiv, biorxiv, PeerJ and public databases
    • Must inform publisher of pre-print deposit
    • Published source must be acknowledged
    • Must link to publisher version upon acceptance
  • Classification
    yellow

Publications in this journal

  • [Show abstract] [Hide abstract]
    ABSTRACT: The involvement of overexpression of the CYP51A1 gene in Venturia inaequalis was investigated for isolates exhibiting differential sensitivity to the triazole DMI fungicides myclobutanil and difenoconazole. Relative expression (R.E.) of the CYP51A1 gene was significantly greater (P < 0.0001) for isolates with resistance to both fungicides (MRDR phenotype) or with resistance to difenoconazole only (MSDR phenotype) compared to isolates that were resistant only to myclobutanil (MRDs phenotype) or sensitive to both fungicides (MSDS phenotype). An average of nine-fold and 13-fold increases in CYP51A1 R.E. was observed in isolates resistant to difenoconazole compared to isolates with MRDs and MsDs phenotypes, respectively. Linear regression analysis between isolate relative growth on myclobutanil-amended medium and log10 R.E. revealed that little to no variability in sensitivity to myclobutanil could be explained by CYP51A1 overexpression (R2 = 0.078). To investigate CYP51A1 upstream anomalies associated with CYP51A1 overexpression and/or resistance to difenoconazole, Illumina sequencing was conducted for three isolates with resistance to difenoconazole and one baseline isolate. A repeated element, "EL 3,1,2", with the properties of a transcriptional enhancer was identified two to four times upstream of CYP51A1 in difenoconazole resistant isolates, but was not found in isolates with the MRDs phenotype. These results suggest that different mechanisms may govern resistance to different DMI fungicides in the triazole group.
    No preview · Article · Feb 2016 · Phytopathology
  • [Show abstract] [Hide abstract]
    ABSTRACT: Globodera spp. are under strict quarantine in many countries. Suppressiveness to cyst nematodes can evolve under monoculture of susceptible hosts. Females developing in potato monoculture soil infested with G. pallida populations Chavornay or Delmsen, were examined for inherent microbial communities. In the greenhouse, non-heated and heat-treated (134 °C for 10 min.) portions of this soil were placed in root observation chambers, planted to Solanum tuberosum 'Selma', and inoculated with G. pallida Pa3 Chavornay. At harvest in Delmsen soil, cysts had fewer eggs in non-heated than heat-treated soil. In denaturing gradient gel electrophoresis (DGGE) analysis, bacterial and fungal fingerprints were characterized by a high variability between replicates; non-heated soils displayed more dominant bands than heated soils indicating more bacterial and fungal populations. In amplicon pyrosequencing, females from non-heated portions frequently contained ITS sequences of the fungus Malassezia. Specific for the Chavornay and Delmsen population, ribosomal sequences of the bacteria Burkolderia and Ralstonia were abundant on eggs. In this first report of microbial communities in G. pallida raised in potato monoculture, candidate microorganisms perhaps associated with the health status of the eggs of G. pallida were identified. If pathologies on cyst nematodes can be ascertained, these organisms could improve the sustainability of production systems.
    No preview · Article · Feb 2016 · Phytopathology
  • [Show abstract] [Hide abstract]
    ABSTRACT: Synchytrium endobioticum is the fungal agent causing potato wart disease. Because of its severity and persistence, quarantine measures are enforced worldwide to avoid the spread of this disease. Molecular markers exist for species-specific detection of this pathogen, yet markers to study the intra-specific genetic diversity of S. endobioticum were not available. Whole genome sequence data from Dutch pathotype 1 isolate MB42 of S. endobioticum was mined for perfect microsatellite motifs. Twenty-one of the 62 selected microsatellites could be amplified successfully and displayed moderate levels of polymorphism in 22 S. endobioticum isolates from different countries. Nineteen multilocus genotypes were observed, with only three isolates from Canada displaying identical profiles. The majority of isolates from Canada clustered genetically. In contrast, most isolates collected in Europe show no genetic clustering associated to their geographic origin. S. endobioticum isolates with the same pathotype displayed highly variable genotypes and none of the microsatellite markers correlated with a specific pathotype. The markers developed in this study can be used to assess intra-specific genetic diversity of S. endobioticum and allow track and trace of genotypes that will generate a better understanding of the migration and spread of this important fungal pathogen and support management of this disease.
    No preview · Article · Feb 2016 · Phytopathology
  • [Show abstract] [Hide abstract]
    ABSTRACT: RNA silencing functions as an anti-virus defense strategy in plants, one that plant viruses counter by producing viral suppressors of RNA silencing (VSRs). VSRs have been identified in three members of the genus Crinivirus but they do not all share identical suppression mechanisms. Here, we used Agrobacterium co-infiltration assays to investigate the suppressor activity of proteins encoded by Lettuce chlorosis virus (LCV). Of 7 LCV proteins (1b, P23, HSP70 homolog, P60, CP, CPm and P27) tested for the suppression of silencing of green fluorescent protein (GFP) expression in wild type Nicotiana benthamiana plants, only P23 suppressed the onset of local silencing. Small-interfering (si)RNA accumulation was reduced in leaves co-infiltrated with P23, suggesting that P23 inhibited the accumulation or enhanced the degradation of siRNA. P23 also inhibited the cell-to-cell and systemic movement of RNA silencing in GFP-expressing transgenic N. benthamiana plants. Expression of P23 via agroinfiltration of N. benthamiana leaves induced local necrosis that increased in severity at elevated temperatures, a novelty given that a direct temperature effect on necrosis severity has not been reported for the other crinivirus VSRs. These results further affirm the sophistication of crinivirus VSRs in mediating the evasion of host's antiviral defenses and in symptom modulation.
    No preview · Article · Feb 2016 · Phytopathology
  • [Show abstract] [Hide abstract]
    ABSTRACT: Hybridization in fungi has recently been recognized as a major force in the generation of new fungal plant pathogens. These include the grass pathogen Zymoseptoria pseudotritici and the powdery mildew pathogen Blumeria graminis triticale of triticale. Hybridization also plays an important role in the transfer of genetic material between species. This process is termed introgressive hybridization and involves extensive backcrossing between hybrid and the parental species. Introgressive hybridization has contributed substantially to the successful spread of plant pathogens such as Ophiostoma ulmi and O. novo-ulmi, the causal agents of Dutch elm disease, and other tree pathogens such as the rust pathogen Melampsora. Hybridization occurs more readily between species that have previously not coexisted, so-called allopatric species. Reproductive barriers between allopatric species are likely to be more permissive allowing interspecific mating to occur. The bringing together of allopatric species of plant pathogens by global agricultural trade consequently increases the potential for hybridization between pathogen species. In light of global environmental changes, agricultural development, and the facilitated long-distance spread of fungal plant pathogens, hybridization should be considered an important mechanism whereby new pathogens may emerge. Recent studies have gained insight into the genetics and biology of fungal hybrids. Here I summarize current knowledge about hybrid speciation and introgressive hybridization. I propose that future studies will benefit greatly from the availability of large genome data sets and that genome data provide a powerful resource in combination with experimental approaches for analyses of hybrid species.
    No preview · Article · Jan 2016 · Phytopathology
  • [Show abstract] [Hide abstract]
    ABSTRACT: Huanglongbing (HLB) is a chronic, progressive decline disease in citrus associated with a systemic infection by the bacterium 'Candidatus Liberibacter asiaticus'. Transmission of the bacterium in the field is by the Asian citrus psyllid, Diaphorina citri, Kuwayama. Experimental propagation of 'Ca. L. asiaticus' is done primarily by grafting pieces of bud wood from an infected plant. To produce a small scale model system for investigation of pathogen biology, we investigated grafting single leaves from infected citrus plants as sources of inoculum for propagation of the bacterium. In total, 162 plants ranging in age from 3 to18 months were grafted. Grafting with intact asymptomatic and HLB-symptomatic leaves resulted in 61/78 (78%) and 35/41 (85%) of the plants infected with HLB, respectively. Inoculum consisting of the leaf petiole only or only an inoculum tissue remnant under the bark of the receptor tree resulted in 6/12 (50%) and 7/31 (23%) infected trees, respectively. Real-time PCR (qPCR) assays verified the infection in plants, a majority of which developed the foliar blotchy-mottle symptom considered diagnostic for HLB, while some plants also displayed the stunted, chlorotic shoots for which the disease is named. The qPCR data together with the symptoms displayed demonstrated that individual leaves from infected trees can serve as effective inoculum sources for transmission and propagation of 'Ca. L. asiaticus' via grafting.
    No preview · Article · Jan 2016 · Phytopathology
  • [Show abstract] [Hide abstract]
    ABSTRACT: Vector-borne virus diseases of wheat are recurrent in nature and pose significant threats to crop production worldwide. In the spring of 2011 and 2012, a state-wide sampling survey of multiple commercial field sites and university-managed Kansas Agricultural Experiment Station variety performance trial locations spanning all nine crop-reporting regions of the state was conducted to determine the occurrence of Barley yellow dwarf virus-PAV (BYDV-PAV), Cereal yellow dwarf virus-RPV, Wheat streak mosaic virus (WSMV), High plains virus, Soilborne wheat mosaic virus, and Wheat spindle streak mosaic virus using enzyme-linked immunosorbent assays (ELISA). As a means of directly coupling tiller infection status with tiller grain yield, multiple pairs of symptomatic and nonsymptomatic plants were selected and individual tillers were tagged for virus species and grain yield determination at the variety performance trial locations. BYDV-PAV and WSMV were the two most prevalent species across the state, often co-occurring within location. Of those BYDV-PAV- or WSMV-positive tillers, 22% and 19%, respectively, were nonsymptomatic, a finding that underscores the importance of sampling criteria to more accurately assess virus occurrence in winter wheat fields. Symptomatic tillers that tested positive for BYDV-PAV produced significantly lower grain yields compared with ELISA-negative tillers in both seasons, as did WSMV-positive tillers in 2012. Nonsymptomatic tillers that tested positive for either of the two viruses in 2011 produced significantly lower grain yields than tillers from nonsymptomatic, ELISA-negative plants, an indication that these tillers were physiologically compromised in the absence of virus-associated symptoms. Overall, the virus survey and tagged paired-tiller sampling strategy revealed effects of virus infection on grain yield of individual tillers of plants grown under field conditions and may provide a complementary approach toward future estimates of the impact of virus incidence on crop health in Kansas.
    No preview · Article · Jan 2016 · Phytopathology
  • [Show abstract] [Hide abstract]
    ABSTRACT: Common scab, a globally important potato disease, is caused by infection of tubers with pathogenic Streptomyces spp. Previously, disease resistant potato somaclones were obtained through cell selections against the pathogen's toxin known to be essential for disease. Further testing revealed these clones had broad spectrum resistance to diverse tuber-invading pathogens, and that resistance was restricted to tuber tissues. The mechanism of enhanced disease resistance was not known. Tuber periderm tissues from disease-resistant clones and their susceptible parent were examined histologically following challenge with the pathogen and its Common scab, a globally important potato disease, is caused by infection of tubers with pathogenic Streptomyces spp. Previously, disease resistant potato somaclones were obtained through cell selections against the pathogen's toxin known to be essential for disease. Further testing revealed these clones had broad spectrum resistance to diverse tuber-invading pathogens, and that resistance was restricted to tuber tissues. The mechanism of enhanced disease resistance was not known. Tuber periderm tissues from disease-resistant clones and their susceptible parent were examined histologically following challenge with the pathogen and its purified toxin. Relative expression of genes associated with tuber suberin biosynthesis and innate defense pathways within these tissues were also examined. The disease-resistant somaclones reacted to both pathogen and toxin by producing more phellem cell layers in the tuber periderm, and accumulating greater suberin polyphenols in these tissues. Furthermore, they had greater expression of genes associated with suberin biosynthesis. In contrast, signaling genes associated with innate defense responses were not differentially expressed between resistant and susceptible clones. The resistance phenotype is due to induction of increased periderm cell layers and suberization of the tuber periderm preventing infection. The somaclones provide a valuable resource for further examination of suberization responses and its genetic control.
    No preview · Article · Jan 2016 · Phytopathology
  • [Show abstract] [Hide abstract]
    ABSTRACT: Rhizoctonia root rot and bare patch, caused by R. solani AG-8 and R. oryzae, are chronic and important yield-limiting diseases of wheat and barley in the Inland Pacific Northwest (PNW) of the USA. Major gaps remain in our understanding of the epidemiology of these diseases, in part because multiple Rhizoctonia anastomosis groups (AGs) and species can be isolated from the same cereal roots from the field, contributing to the challenge of identifying the causal agents correctly. In this study, a collection totaling 498 isolates of Rhizoctonia was assembled from surveys conducted from 2000-2009, 2010 and 2011 over a wide range of cereal production fields throughout Washington State in the PNW. To determine the identity of the isolates, PCR with anastomosis group- or species-specific primers and/or DNA sequence analysis of the internal transcribed spacers was performed. R. solani AG-2-1, AG-8, AG-10, AG-3, AG-4, and AG-11, comprised 157 (32%), 70 (14%), 21 (4%), 20 (4%), 1 (0.2%), and 1 (0.2%), respectively, of the total isolates. AG-I-like binucleate Rhizoctonia sp. comprised 44 (9%) of the total; and 53 (11%), 80 (16%) and 51 (10%) were identified as R. oryzae genotypes I, II and III, respectively. Isolates of AG-2-1, the dominant Rhizoctonia, occurred in all six agronomic zones defined by annual precipitation and temperature within the region sampled. Isolates of AG-8 also were cosmopolitan in their distribution but the frequency of isolation varied among years, and they were most abundant in zones of low and moderate precipitation. R. oryzae was cosmopolitan, and collectively the three genotypes comprised 37% of the isolates. Only isolates of R. solani AG-8 and R. oryzae genotypes II and III (but not genotype I) caused symptoms typically associated with Rhizoctonia root rot and bare patch of wheat. Isolates of AG-2-1 caused only mild root rot and AG-I-like binucleate isolates and members of anastomosis groups AG-3, AG-4, and AG-11 showed only slight or no discoloration of the roots. However, all isolates of AG-2-1 caused severe damping-off of canola, resulting in 100% mortality. Isolates of Rhizoctonia AG-8, AG-2-1, and AG-10, AG-I-like binucleate Rhizoctonia, and R. oryzae genotypes I, II, III could be distinguished by colony morphology on potato dextrose agar, by PCR reactions with specific primers, or by the type and severity of disease on wheat and canola seedlings, and results of these approaches correlated perfectly. Based on cultured isolates, we also identified the geographic distribution of all of these Rhizoctonia isolates in cereal-based production systems throughout Washington State.
    No preview · Article · Jan 2016 · Phytopathology
  • [Show abstract] [Hide abstract]
    ABSTRACT: Recent studies have shown the superiority of high throughput sequencing (HTS) technology over many standard protocols for pathogen detection. HTS was initiated on fruit tree accessions from disparate sources to improve and advance virus testing procedures. A virus with genomic features resembling most closely that of recently described Nectarine stem pitting-associated virus (NSPaV), putative member of genus Luteovirus, was found in three nectarine trees (Prunus persica cv. nectarina), each exhibiting stem pitting symptoms on the woody cylinder above the graft union. HTS also revealed in these samples the presence of a co-infecting virus with genome characteristics typical of members of the genus Marafivirus. The same marafivirus- and luteovirus-like viruses were detected in non-symptomatic nectarine and peach selections indicating only a loose relationship between these two viruses with nectarine stem pitting disease symptoms. Two selections infected with each of these viruses had previously tested free of known virus or virus-like agents using the current biological, serological and molecular tests employed at the Clean Plant Center Northwest. Overall, this study presents the characterization by HTS of novel marafivirus- and luteovirus-like viruses of nectarine, and sheds further insights on the etiology of nectarine stem pitting disease. The discovery of these new viruses emphasizes the ability of HTS to reveal viruses that are not detected by existing protocols.
    No preview · Article · Jan 2016 · Phytopathology
  • [Show abstract] [Hide abstract]
    ABSTRACT: The plant pathogenic fungi Uromyces appendiculatus and Phakopsora pachyrhizi cause debilitating rust diseases on common bean and soybean. These rust fungi secrete effector proteins that allow them to infect plants, but their effector repertoires are not understood. The discovery of rust fungus effectors may eventually help guide decisions and actions that mitigate crop production loss. Therefore, we used mass spectrometry to identify thousands of proteins in infected beans and soybeans and in germinated fungal spores. The comparative analysis between the two helped differentiate a set of 24 U. appendiculatus proteins targeted for secretion that were specifically found in infected beans and a set of 34 U. appendiculatus proteins targeted for secretion that were found in germinated spores and infected beans. The proteins specific to infected beans included family 26 and family 76 glycoside hydrolases that may contribute to degrading plant cell walls. There were also several types of proteins with structural motifs that may aid in stabilizing the specialized fungal haustorium cell that interfaces the plant cell membrane during infection. There were 16 P. pachyrhizi proteins targeted for secretion that were found in infected soybeans, and many of these proteins resembled the U. appendiculatus proteins found in infected beans, which implies that these proteins are important to rust fungal pathology in general. This dataset provides insight to the biochemical mechanisms that rust fungi use to overcome plant immune systems and to parasitize cells.
    No preview · Article · Jan 2016 · Phytopathology
  • [Show abstract] [Hide abstract]
    ABSTRACT: Grapevine leafroll-associated virus 3 (GLRaV-3) has a worldwide distribution and is the most economically important virus that causes grapevine leafroll disease. Reliable, sensitive and specific methods are required for the detection of the pathogen in order to assure the production of healthy plant material and control of the disease. Although different serological and nucleic-acid-based methods have been developed for the detection of GLRaV-3, diagnostic parameters have not been established, and there is no gold standard method. Therefore, the main aim of this work was to determine the sensitivity, specificity and likelihood ratios of three commonly used methods, including one serological test (DAS-ELISA) and two nucleic-acid-based techniques (spot and conventional real-time RT-PCR). Latent class models using a Bayesian approach have been applied to determine diagnostic test parameters and to facilitate decision-making regarding diagnostic test selection. Statistical analysis has been based on the results of a total of 281 samples, which were collected during the dormant period from three different populations. The best-fit model out of the 49 implemented models revealed that DAS-ELISA was the most specific method (value=0.99) and provided the highest degree of confidence in positive results. Conversely, conventional real-time RT-PCR was the most sensitive method (value=0.98) and produced the highest degree of confidence in negative results. Furthermore, the estimation of likelihood ratios showed that in populations with low GLRaV-3 prevalence the most appropriate method could be DAS-ELISA while conventional real-time RT-PCR could be the most appropriate method in medium or high prevalence populations. Combining both techniques significantly increases detection accuracy. The flexibility and power of Bayesian latent class models open new possibilities for the evaluation of diagnostic tests for plant viruses.
    No preview · Article · Jan 2016 · Phytopathology
  • [Show abstract] [Hide abstract]
    ABSTRACT: The soil-borne fungal pathogen Verticillium dahliae infects a broad range of plant species to cause severe diseases. The availability of Verticillium genome sequences has allowed opportunities for large-scale investigations of individual gene function in Verticillium strains using Agrobacterium tumefaciens-mediated transformation (ATMT)-based gene disruption strategies. Traditional ATMT vectors require multiple cloning steps and elaborate characterization procedures to achieve successful gene replacement; thus, these vectors are not suitable for high-throughput ATMT-based gene deletion. Several advancements have been made that either involve simplification of the steps required for gene-deletion vector construction or increases in the efficiency of the technique for rapid recombinant characterization. However, an ATMT binary vector that is both simple and efficient is still lacking. Here, we generated a USER-ATMT-dual selection (DS) binary vector, which combines both the advantages of the USER single-step cloning technique and the efficiency of the herpes simplex virus thymidine kinase (HSVtk) negative selection marker. Highly efficient deletion of three different genes in V. dahliae using the USER-ATMT-DS vector enabled verification that this newly-generated vector not only facilitates the cloning process but also simplifies the subsequent identification of fungal homologous recombinants. The results suggest that the USER-ATMT-DS vector is applicable for efficient gene deletion and suitable for large-scale gene deletion in V. dahliae.
    No preview · Article · Jan 2016 · Phytopathology
  • [Show abstract] [Hide abstract]
    ABSTRACT: Sclerotinia sclerotiorum (Lib.) de Bary is a widely dispersed plant pathogenic fungus causing many diseases such as white mold, Sclerotinia stem rot, stalk rot, and Sclerotinia head rot on many varieties of broadleaf crops worldwide. Previous studies have shown that the Forkhead-box transcription factors (the FOX TFs) play key regulatory roles in the sexual reproduction of some fungi. Ss-FoxE2 is one of four Forkhead-box transcription factor family member genes in S. sclerotiorum. Based on ortholog function in other fungi it is hypothesized to function in S. sclerotiorum sexual reproduction. In this study, the role of Ss-FoxE2 in S. sclerotiorum was identified with a gene knock-out strategy. Following transformation and screening, strains having undergone homologous recombination in which the hygromycin resistance gene replaced the gene Ss-FoxE2 from the genomic DNA were identified. No difference in hyphae growth, number and weight of sclerotia and no obvious change in virulence was observed among the wild type, Ss-FoxE2 knock-out mutant and genetically complemented mutant, however, following induction of sclerotia for sexual development, apothecia were not formed in Ss-FoxE2 knock-out mutant. The Ss-FoxE2 gene expressed significantly higher in the apothecial stages than other developmental stages. These results indicate that Ss-FoxE2 appears to be necessary for the regulation of sexual reproduction, but may not affect the pathogenicity and vegetative development of S. sclerotiorum significantly.
    No preview · Article · Jan 2016 · Phytopathology
  • [Show abstract] [Hide abstract]
    ABSTRACT: Acidovorax citrulli, the causal agent of bacterial fruit blotch of cucurbits (BFB) has been observed to survive for more than 34 years in stored melon and watermelon seeds. To better understand this remarkable longevity, we investigated the bacterium's tolerance to desiccation and the effect of bacterial localization in different watermelon seed tissues. We compared the ability of A. citrulli to tolerate desiccation on filter paper discs and on host- (watermelon) and non-host (cabbage, corn and tomato) seeds to two seedborne (Xanthomonas campestris pv. campestris and Pantoea stewartii subsp. stewartii) and one soil borne (Ralstonia solanacearum) phytopathogenic bacteria. A. citrulli survival on dry filter paper (>12 weeks) was similar to that of X. campestris pv. campestris but longer than P. stewartii subsp. stewartii. Ralstonia solanacearum survived longer than all other bacteria tested. On all seeds tested, A. citrulli and X. campestris pv. campestris populations declined by 5 orders of magnitude after 12 weeks of incubation at 4°C and 50% relative humidity, while R. solanacearum populations declined by 3 orders. P. stewartii subsp. stewartii CFUs were not recovered after 12 weeks of incubation. To determine the effect of tissue localization on bacterial survival, watermelon seeds infested with A. citrulli by flower stigma inoculation (resulting in bacterial localization in the embryo/endosperm) or by ovary pericarp inoculation (resulting in bacterial localization under the testa) were treated with peroxyacetic acid or chlorine (Cl2) gas. Following these treatments, a significantly higher reduction in BFB seed-to-seedling transmission was observed for seeds generated by ovary pericarp inoculation (≥89.5%) than for those generated by stigma inoculation (≤76.5%) (P<0.05). Additionally, higher populations of A. citrulli survived when localized to the embryo/endosperm versus the seed coat, suggesting that tissue localization is important for bacterial survival in seed. This observation was confirmed when P. stewartii subsp. stewartii survived significantly longer in stigma-inoculated (embryo/endosperm-localized) watermelon seeds than in vacuum-infiltrated (testa-localized) seeds. Based on these results we conclude that A. citrulli cells are not intrinsically tolerant to desiccation and localization of the bacterium to testa tissues does not enhance A. citrulli survival. In contrast, it is likely that embryo/endosperm localization enhances the survival of A. citrulli and other bacteria in seeds.
    No preview · Article · Jan 2016 · Phytopathology