The Population of Sclerotinia sclerotiorum in Brazil Is Structured by Mycelial Compatibility Groups

Abstract

The genetic structure of the population of Sclerotinia sclerotiorum was analyzed using 238 individuals collected from different hosts. Individuals were characterized for microsatellite genotypes and mycelial compatibility groups (MCGs). A total of 22 MCGs and 64 multilocus lineages (MLLs) were identified. There was a close relationship between the MCGs and MLLs, but there was no association between MLLs and hosts or regions. At least 39 MCGs are present in Brazil and 68.5% of the isolates were assigned to either MCG 1 or 2. Eight new MCGs were found. Seven genetic groups were identified and associated with MCGs. Most genetic variation (70.0%) was due to differences among MCGs. High values of estimates of linkage disequilibrium among loci were more frequent in the total population (all MCGs). In contrast, there was evidence of random mating in subpopulations defined by MCGs 1 and 2. Additionally, there was evidence of outcrossing in the population of S. sclerotiorum in Brazil. The population was structured by MCGs, lineages originated from asexual reproduction or selfing prevail and are widely distributed in space, are persistent in time and affect many hosts, but there is evidence of some degree of outcrossing which may lead to a more genetically variable population in the future.

Characterization of fungal pathogens and germplasm screening for disease resistance in the main production area of the common bean in Argentina

“…However, in a subsequent study using linkage disequilibrium measures, Lehner et al (2015) reported that despite the relatively high genotypic diversity observed among isolates, the SSR loci were in linkage disequilibrium, and thus, the S. sclerotiorum population had a clonal genetic structure. These results were later supported in larger studies, where the pathogen population of Brazil not only remained clonal but also structured according to MCGs (Lehner et al, 2019;Silva et al, 2021). Silva et al (2021) analyzed 238 isolates, and only 22 MCGs and 64 SSR haplotypes were found, with no association between SSR haplotypes and MCGs.…”

“…These results were later supported in larger studies, where the pathogen population of Brazil not only remained clonal but also structured according to MCGs (Lehner et al, 2019;Silva et al, 2021). Silva et al (2021) analyzed 238 isolates, and only 22 MCGs and 64 SSR haplotypes were found, with no association between SSR haplotypes and MCGs. Although their clonal lineages were widely distributed in space and persistent over time, evidence of some degree of outcrossing was detected (Silva et al, 2021).…”

“… Silva et al (2021) analyzed 238 isolates, and only 22 MCGs and 64 SSR haplotypes were found, with no association between SSR haplotypes and MCGs. Although their clonal lineages were widely distributed in space and persistent over time, evidence of some degree of outcrossing was detected ( Silva et al, 2021 ). In the case of common bean fields in the United States, Kamvar et al (2017) reported that S. sclerotiorum populations had a clonal population structure with low genetic diversity using MCGs and SSRs.…”

“…According to recent research, mycelial compatibility groups (MCGs) are useful as a rough measure of standing genotypic diversity but are not adequate to infer population genetic processes ( Kamvar and Everhart, 2019 ; Figure 1 ). However, other studies have suggested taking into account the structure imposed by the MCGs in addition to a set of molecular markers in population analyses ( Lehner and Mizubuti, 2017 ; Lehner et al, 2019 ; Silva et al, 2021 ). Over the past few years, the population structure of S. sclerotiorum has been extensively documented from different host crops and from different regions in the world ( Atallah et al, 2004 ; Sexton et al, 2006 ; Hemmati et al, 2009 ; Ekins et al, 2011 ; Attanayake et al, 2013 ; Clarkson et al, 2013 , 2017 ; Aldrich-Wolfe et al, 2015 ; Dunn et al, 2017 ; Panullo et al, 2018 ; Faraghati et al, 2022 ).…”

“…Despite the fact that the bean crop is cultivated in many countries, the genetic diversity and population structure of S. sclerotiorum in common bean crops have only been analyzed in Brazil ( Lehner et al, 2015 , 2017 , 2019 ; Silva et al, 2021 ), the United States ( Kamvar et al, 2017 ) and Argentina ( Abán et al, 2018 , 2021 ). In Brazil, the first study using microsatellite markers analyzed 79 isolates and reported high genotypic variability among S. sclerotiorum isolates ( Gomes et al, 2011 ).…”