Aphanomyces euteiches is an oomycete pathogen with a broad host-range on legumes that causes devastating root rot disease in many pea-growing countries and especially in France. Genetic resistance is a promising way to manage the disease since consistent QTL controlling partial resistance have been identified in near isogenic lines of pea. However, there are still no resistant pea varieties cultivated in France. This study aimed to evaluate the phenotypic and genetic diversity of A. euteiches populations from the major pea-growing regions in France. A collection of 205 isolates, from soil samples collected in infested pea fields located in five French regions, was established and genotyped using 20 SSR markers. Thirteen multilocus genotypes were found among the 205 isolates which displayed a low genotypic richness (ranged from 0 to 0.333). Two main clusters of isolates were identified using PCoA and STRUCTURE, including a predominant group comprising 88% of isolates and another group representing 12% of isolates mainly from the Bourgogne region. A subset of 34 isolates, representative of the fields sampled, was phenotyped for aggressiveness on a set of resistant and susceptible varieties of four legume hosts (pea, faba bean, vetch, alfalfa). Significant differences in disease severity were found among isolates and three groups of aggressiveness comprising 16, 17, and 2 isolates, respectively, were identified using HCA analysis. A higher diversity in pathogen aggressiveness was observed among isolates from Bourgogne, which included different legumes in its crop history. Little relationship was observed between genetic clusters and pathogenicity in the subset of 34 isolates, as expected using neutral markers. This study provides useful knowledge on the current state of low to moderate diversity among A. euteiches populations before resistant pea varieties are grown in France. New insights and hypotheses about the major factors shaping the diversity and evolution of A. euteiches are also discussed.
Aphanomyces root rot is a major disease in many pea-growing regions worldwide. The development of resistant varieties is necessary to manage the disease. Near isogenic lines (NILs) carrying resistance alleles at main validated quantitative trait loci (QTL) were developed by marker-assisted backcrossing (MAB). This study aimed to evaluate the aggressiveness of diverse French isolates of Aphanomyces euteiches on NILs carrying different resistance QTL. Fourty-three A. euteiches isolates from different French pea-growing regions were tested for aggressiveness on eight NILs carrying single or combinations of resistance QTL and two susceptible or resistant control lines, in controlled conditions. Three clusters of isolates, unrelated to geographical origin, were identified, including 37%, 56% and 7% of isolates with high, moderate and low average level of aggressiveness, respectively. Three groups of pea lines were also identified, including the pea resistant control line as moderately to highly resistant to all the isolates, five NILs carrying a major-effect resistance allele at QTL Ae-Ps7.6 with medium to broad range of effects on the isolates and three NILs carrying minor-effect resistance alleles with a narrow range of effects on the isolates. Results suggest that highly aggressive isolates naturally occur, that may be selected by partially resistant pea lines carrying QTL and increase the risk of erosion of QTL effect. QTL pyramiding strategies for a higher level and a broader range of effect of quantitative resistance on A. euteiches populations will be required for breeding for durable pea resistant varieties.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.