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Genotypic variation and population structure of S clerotinia trifoliorum infecting chickpea in C alifornia
Author(s) -
Njambere E. N.,
Peever T. L.,
Vandemark G.,
Chen W.
Publication year - 2014
Publication title -
plant pathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.928
H-Index - 85
eISSN - 1365-3059
pISSN - 0032-0862
DOI - 10.1111/ppa.12176
Subject(s) - biology , analysis of molecular variance , genetic diversity , microsatellite , population , genetic variation , genetics , genotype , evolutionary biology , allele , gene , demography , sociology
S clerotinia trifoliorum , an important pathogen of cool season legumes, displays both homothallism and heterothallism in its life cycle, unique among members of the genus S clerotinia . Very little is known about its genetic diversity and population structure. A sample of 129 isolates of S. trifoliorum from diseased chickpea in California was investigated for genetic diversity, population differentiation and reproductive mode. Genetic diversity was estimated using mycelial compatibility (MCG) phenotypes, rDNA intron variation, and allelic diversity at seven microsatellite loci. Genetic analysis revealed high levels of genotypic diversity demonstrated by high genotypic richness (0·88). Similarly, high levels of gene diversity (mean expected heterozygosity H E = 0·68) were observed at the microsatellite loci. Geographic populations of S. trifoliorum were highly admixed as evident from low F ST values (0–0·11), suggesting high contemporary or historical gene flow. Hierarchical analysis of molecular variance showed that more than 92% of the genetic variation occurred among isolates within populations. Bayesian clustering analysis identified four cryptic genetic populations that were not correlated to geographic location, and index of multilocus association was non‐significant in each of the four genetic populations. However, the presence of identical haplotypes within and among populations indicates clonal reproduction. The high levels of haplotype diversity and population heterogeneity, a lack of correspondence between MCG and microsatellite haplotype, and low levels of population differentiation suggest that populations of S. trifoliorum in chickpea have been undergoing extensive outcrossing and migration events probably shaped by human‐mediated dissemination, the underlying diverse cropping systems, and chickpea disease management practices.