Microsatellite Markers Reveal Genetic Variation within Sclerotinia sclerotiorum Populations in Irrigated Dry Bean Crops in Brazil

Abstract

Eriston riston Vieira ieira Gomes omes 1 , Lucas ucas Breseguello reseguello do do Nascimento ascimento 1 , Marcos arcos Augusto ugusto de de Freitas reitas 2 , Luiz uiz Carlos arlos Bhering hering Nasser asser 2 and Silvana ilvana Petrofeza etrofeza 1 AbstractMicrosatellites are powerful markers to infer population genetic parameters. We used 10 microsatellite loci to characterize the genetic diversity and structure of 79 samples of Sclerotinia sclerotiorum isolated from four Brazilian dry bean populations and observed that eight of them were polymorphic within populations. We identified 102 different haplotypes ranging from 6 to 18 per locus. Analyses based on genetic diversity and fixation indices indicated variability among and within populations of 28.79% (F ST = 28793) and 71.21%, respectively. To examine genetic relatedness among S. sclerotiorum isolates, we used internal spacer (ITS1-5.8S-ITS2) restriction fragment length polymorphism (PCR-RFLP) and sequencing analysis. PCR-RFLP analysis of these regions failed to show any genetic differences among isolates. However, we detected variability within the sequence, which does not support the hypothesis of clonal populations within each population. High variability within and among populations may indicate the introduction of new genotypes in the areas analysed, in addition to the occurrence of clonal and sexual reproduction in the populations of S. sclerotiorum in the Brazilian Cerrado.

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

“…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 and most studies have focused on polymorphisms of neutral molecular markers (Cubeta et al, 1997;Sexton et al, 2004;Sexton et al, 2006;Malvárez et al, 2007;Ekins et al, 2011;Gomes et al, 2011;Clarkson et al, 2013).Phenotypic variability has been observed among isolates of S. sclerotiorum collected from different hosts in Canada (Morral et al, 1972), rape in Turkey (Merk-Turk et al, 2007) and Australia (Garg et al, 2010) and canola in China and USA (Attanayake et al, 2013). On the other hand, phenotypic uniformity was observed among isolates from potato in USA (Atallah et al, 2004).…”

“…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 and most studies have focused on polymorphisms of neutral molecular markers (Cubeta et al, 1997;Sexton et al, 2004;Sexton et al, 2006;Malvárez et al, 2007;Ekins et al, 2011;Gomes et al, 2011;Clarkson et al, 2013).…”

Case Study: Sclerotinia sclerotiorum: Genetic Diversity and Disease Control

“…If the population is recombining or presents genetic exchange, markers, MCG, and fingerprint will not be associated. This has been observed in subtropical populations of S. sclerotiorum (Cubeta et al, 1997;Carbone and Kohn, 2001b;Meinhardt et al, 2002;Atallah et al, 2004;Sexton et al, 2006;Gomes et al, 2011;Litholdo Júnior et al, 2011). In a highly recombinant population, the expectation is that each isolate sampled, or most of them, is either incompatible with all other isolates or is part of an intransitive MCG, and each isolate either has a unique fingerprint or a fingerprint associated with more than one MCG.…”

“…Isolates taken from beans and two other crops from another region of Brazil showed the same two MCGs and had identical banding patterns for the telomere and microsatellite primers (Meinhardt et al, 2002). In a subsequent work, Gomes et al (2011) analyzed 79 isolates of S. sclerotiorum collected from four common bean center-pivot-irrigated fields and using microsatellite markers observed high genetic diversity within and among populations. The authors suggested that the occurrence of exclusive alleles in the populations analyzed may indicate the introduction of new genotypes in these areas at different moments through contaminated seeds or agricultural implements, in addition to the occurrence of sexual outcrossing and clonal reproduction.…”

“…Prior researches on S. sclerotiorum population structure, in areas where canola, sunflower, cabbage, and other crops are grown, have shown that this pathogen populations are mainly clonal (Kohli et al, 1992(Kohli et al, , 1995Anderson and Kohn, 1995;Cubeta et al, 1997;Kohli and Kohn, 1998;Carpenter et al, 1999;Hambleton et al, 2002), even though some recombination has been detected (Cubeta et al, 1997;Carbone and Kohn, 2001a), being more evident in subtropical populations than in temperate ones (Carbone et al 1999;Carbone and Kohn, 2001b;Atallah et al, 2004;Sexton and Howlett, 2004;Sexton et al, 2006;Mert-Türk et al, 2007;Gomes et al, 2011).…”