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ARS Home » Pacific West Area » Pullman, Washington » Grain Legume Genetics Physiology Research » Research » Publications at this Location » Publication #351515
Title: Sclerotinia sclerotiorum populations: Clonal or recombining?

Author
item ATTANAYAKE, RENUKA - University Of Kelaniya
item XU, LIANGSHENG - Northwest Agricultural & Forestry University
item Chen, Weidong

Submitted to: Tropical Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/7/2018
Publication Date: 9/4/2018
Citation: Attanayake, R.N., Xu, L., Chen, W. 2018. Sclerotinia sclerotiorum populations: Clonal or recombining? Tropical Plant Pathology. 44:23-31. https://doi.org/10.1007/s40858-018-0248-7.
DOI: https://doi.org/10.1007/s40858-018-0248-7

Interpretive Summary: The fungal plant pathogen Sclerotinia sclerotiorum causes white mold diseases on more than 400 plant species. Management of Sclerotinia diseases is difficult because resistant cultivars are not available in most of the susceptible crops. Increasing our understanding of pathogen population biology will allow us to develop appropriate management strategies. Population genetics concerns genetic variation in populations over time and space. Through mathematical modeling, population genetics allows inference about the behavior of populations and predict its evolutionary potential. This paper focuses on recent developments in population genetics studies in Sclerotinia. Sclerotinia sclerotiorum undergoes sexual reproduction by self-fertilization which is equivalent to clonal reproduction. It also produces long-lasting survival structures that enhance clonal persistence and spread. However, its population behavior in nature is not well understood. Early studies showed that S. sclerotiorum has a clonal population structure, consistent with its life history traits. However, recent studies using molecular markers showed frequent genetic recombination, suggesting outcrossing. Recent findings provide new insights and directions in future research to unravel the mechanisms underlying genetic changes in Sclerotinia sclerotiorum. This will advance our understanding how S. sclerotiorum populations behave in nature, ultimately improving our management of Sclerotinia diseases.

Technical Abstract: Sclerotinia sclerotiorum, a homothallic plant pathogen, undergoes sexual reproduction via haploid selfing (equivalent to clonal reproduction), and produces long-lasting survival structures that enhance clonal persistence and spread. Thus it is not surprising to detect clones of the species. However, whether outcrossing can occur in the homothallic S. sclerotiorum remains unanswered. Early studies showed that S. sclerotiorum has a clonal population structure, consistent with its life history traits. However, recent studies using polymorphic and co-dominant molecular markers showed frequent genetic recombination, suggesting outcrossing. This review focuses on recent developments in population genetics studies related to detecting recombination, random association of alleles and dynamic mating type (MAT) alleles in Sclerotinia. Despite frequent reports of random association of alleles, the mechanisms for outcrossing in a homothallic species remain elusive. Recent intriguing findings are: the MAT genes in Sclerotinia are subject to inversion or deletion in every meiotic generation, the MAT gene deletion is related to ascospore dimorphism and mating type switching in S. trifoliorum, and ascospore dimorphism was also observed in S. sclerotiorum. Determining the nature of the dimorphic ascospores and their prevalence in relation to environmental cues could significantly advance our understanding how S. sclerotiorum populations behave in nature.