Genetic and phenotypic diversity and random association of DNA markers of isolates of the fungal plant pathogen Sclerotinia sclerotiorum from soil on a fine geographic scale

Attanayake, R.N.; Porter, Lyndon D.; Johnson, Dennis A.; Chen, W.

doi:10.1016/j.soilbio.2012.06.002

Cited by 29 publications

(45 citation statements)

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“…Sclerotinia sclerotiorum is homothallic and exhibits clonality (Steadman and Boland, 2005). However, more recently Attanayake et al (2012) reported considerable genetic and phenotypic variability among 40 isolates of S. sclerotiorum collected from a 1 m 2 area of the top 1.27 cm layer of soil in an alfalfa ( Medicago sativa L.) field in southern Washington State and evidence of outcrossing (heterothallism) within interbreeding subpopulations of S. sclerotiorum .…”

Section: The White Mold Diseasementioning

confidence: 99%

Breeding Common Bean for Resistance to White Mold: A Review

2013

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Under favorable weather conditions white mold causes 100% loss of yield and quality of susceptible common bean (Phaseolus vulgaris L.) cultivars. The disease is endemic and widespread in North and South American countries including the United States, Canada, Argentina, and Brazil. Our objective was to review progress achieved in identifying sources of resistance in Phaseolus species, genetics, and breeding for resistance to white mold. We also describe an integrated genetic improvement strategy for resistance to the pathogen with germplasm enhancement and cultivar development using multiple‐parent crosses and gamete selection methods of breeding. Substantial progress has been made in understanding pathogenic variation in the white mold fungus, developing screening methods, identifying sources of resistant germplasm, genetics of resistance, and introgressing resistance from the secondary gene pool, and breeding for resistance to white mold. Also, molecular marker‐assisted selection for partial resistance is practiced. However, development of white mold resistant common bean cultivars in most market classes has been slow and localized. Breeding strategies for simultaneous and integrated genetic improvement of qualitatively and quantitatively inherited resistances to white mold and cultivar development are briefly described.

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Section: The White Mold Diseasementioning

confidence: 99%

Breeding Common Bean for Resistance to White Mold: A Review

2013

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“…Screening the 19 microsatellite loci identified 12 loci that were polymorphic on the subset of the isolates. These 12 polymorphic loci were used to genotype all of the 268 isolates using an ABI3730xl DNA Analyzer (Applied Biosystems) at the USDA-ARS Western Regional Small Grain Genotyping Laboratory (Pullman, WA, USA) as described in Attanayake et al (2012). Briefly, PCR reactions were performed with one of the four fluorophores (Vic, Pet, Ned and 6-Fam) and multiplexed.…”

Section: Isolate Collection and Mcgsmentioning

confidence: 99%

Inferring outcrossing in the homothallic fungus Sclerotinia sclerotiorum using linkage disequilibrium decay

et al. 2014

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The occurrence and frequency of outcrossing in homothallic fungal species in nature is an unresolved question. Here we report detection of frequent outcrossing in the homothallic fungus Sclerotinia sclerotiorum. In using multilocus linkage disequilibrium (LD) to infer recombination among microsatellite alleles, high mutation rates confound the estimates of recombination. To distinguish high mutation rates from recombination to infer outcrossing, 8 population samples comprising 268 S. sclerotiorum isolates from widely distributed agricultural fields were genotyped for 12 microsatellite markers, resulting in multiple polymorphic markers on three chromosomes. Each isolate was homokaryotic for the 12 loci. Pairwise LD was estimated using three methods: Fisher's exact test, index of association (I A ) and Hedrick's D 0 . For most of the populations, pairwise LD decayed with increasing physical distance between loci in two of the three chromosomes. Therefore, the observed recombination of alleles cannot be simply attributed to mutation alone. Different recombination rates in various DNA regions (recombination hot/ cold spots) and different evolutionary histories of the populations could explain the observed differences in rates of LD decay among the chromosomes and among populations. The majority of the isolates exhibited mycelial incompatibility, minimizing the possibility of heterokaryon formation and mitotic recombination. Thus, the observed high intrachromosomal recombination is due to meiotic recombination, suggesting frequent outcrossing in these populations, supporting the view that homothallism favors universal compatibility of gametes instead of traditionally believed haploid selfing in S. sclerotiorum. Frequent outcrossing facilitates emergence and spread of new traits such as fungicide resistance, increasing difficulties in managing Sclerotinia diseases.

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“…aggressiveness of S. sclerotiorum but the number of isolates involved was small (N=8). Intense pigmentation of mycelium has been reported for isolates of S. sclerotiorum in Australia (Garg et al, 2010), USA (Sanogo & Puppala, 2007;Attanayake et al, 2012) and China (Attanayake et al, 2013). Within the group of pigmented isolates, there is variation in color intensity (Garg et al, 2010).…”

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confidence: 99%

Sclerotia morphology traits and mycelial growth rate are not informative variables for population studies of Sclerotinia sclerotiorum

Lehner

Júnior

Silva

et al. 2014

Trop. plant pathol.

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The usefulness of sclerotia morphology traits and mycelial growth rate to infer phenotypic variability in populations of Sclerotinia sclerotiorum associated with common beans in Minas Gerais State (MG) was assessed in two experiments. Isolates (131) were collected in the Northwestern, Alto Paranaíba, Zona da Mata and Southern regions of MG and the mycelial growth rate, the number, weight and dimensions (length, width and thickness) of sclerotia and mycelial pigmentation were assessed. There was a high variability among isolates, even among colonies of the same isolate. The variance of the first experiment for the mycelial growth rate, number, weight, length, width and thickness of sclerotia, were 0. 01, 190.15, 0.01, 0.62, 0.12 and 0.05, whereas in the second, the variances were 0.01, 28.48, 0.002, 0.18, 0.06 and 0.03, respectively. Most correlations between traits were of low magnitude except that between length and width (r = 0.84, 'P < 0.001). Regarding colony pigmentation, non-pigmented, pigmented and highly pigmented isolates were identified, but for most isolates this characteristic varied between experiments. No groups based on phenotypic traits were detected. The morphological traits evaluated in the present study are not suitable for characterization of populations of S. sclerotiorum. Key words: Phaseolus vulgaris, sclerotium, phenotypic variability, white mold.Several biological features make the ascomycete Sclerotinia sclerotiorum (Lib.) de Bary a highly threatening fungal pathogen to important crops in Brazil. Sclerotinia sclerotiorum is a homothallic fungus that does not produce conidia, but abundant sclerotia (Bolton et al., 2006). Sclerotia are asexual resting structures that allow pathogen survival when no host is available (Adams & Ayers, 1979). The pathogen has a host range that encompasses over 400 plant species (Boland & Hall 1994). Furthermore, pathogen propagules (sclerotia) can be easily spread over long-distance by contaminated seeds. Sclerotinia sclerotiorum causes white mold in crops such as cotton, soybean, potato, sunflower etc., and is the main soilborne disease affecting common bean (Phaseolus vulgaris L.) in Minas Gerais State (MG), Brazil.In Brazil common bean is produced in the springsummer, summer-fall, and fall-winter growing seasons (Vieira et al., 2010). Considering the three growing seasons, MG is the second largest producer, but ranks first during the fall-winter, with an average yield of 2600 kg ha -1 (CONAB, 2013). In the fall-winter growing season, moderate temperatures and high humidity provided by irrigation create conducive environmental conditions for white mold epidemics (Paula Júnior et al., 2006). Planting white mold resistant cultivar would be attractive alternative for disease management. Nevertheless, to date there are no resistant varieties available to growers. Sound breeding programs require proper understanding of the pathogen variability. The variability of populations of S. sclerotiorum has been investigated for different crops around the world an...

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Genetic and phenotypic diversity and random association of DNA markers of isolates of the fungal plant pathogen Sclerotinia sclerotiorum from soil on a fine geographic scale

Cited by 29 publications

References 52 publications

Breeding Common Bean for Resistance to White Mold: A Review

Breeding Common Bean for Resistance to White Mold: A Review

Inferring outcrossing in the homothallic fungus Sclerotinia sclerotiorum using linkage disequilibrium decay

Sclerotia morphology traits and mycelial growth rate are not informative variables for population studies of Sclerotinia sclerotiorum

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