Genetic and Pathogenicity Diversity of Aphanomyces euteiches Populations From Pea-Growing Regions in France

Abstract

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.

Testing of life history traits of a soilborne pathogen in vitro: Do characteristics of oospores change according the strains of Aphanomyces euteiches and the host plant infected by the pathogen?

“…This result is quite surprising as more viable oospores were expected on pea. Indeed, all the A. euteiches ‐inoculated strains were more aggressive on pea than on the two other legume species (Quillévéré‐Hamard et al, ). Concerning the impact of strain origin, difference between strains was observed for all the legume species.…”

“…Initially considered to only be a pathogen of pea (Scott, ), A. euteiches was later reported to also infect other legume species including common bean, broad bean, faba bean, clover and alfalfa (Burnett, Coventry, Hirth, & Greenhalgh, ; Greenhalgh & Merriman, ; Lamari & Bernier, ; Moussart, Even, & Tivoli, ; Pfender & Hagedorn, ; Tivoli, Baranger, Sivasithamparam, & Barbetti, ). It is a phenotypically and genotypically heterogeneous species (Grünwald & Hoheisel, ; Malvick & Percich, ; Le May et al, ; Quillévéré‐Hamard et al, ). Aphanomyces euteiches is a diploid and homothallic pathogen producing both oospores (sexual reproduction) and zoospores (asexual reproduction; Grünwald & Hoheisel, ).…”

“…In order to support breeding for resistance against A. euteiches populations present in French pea‐growing regions and better understand the potential adaptation of pathogen populations to genetic resistance, more knowledge is required about the ecology and genetic diversity of A. euteiches populations and factors influencing its potential evolution. The observation of only one pathotype in France (Le May et al, ; Quillévéré‐Hamard et al, ) may facilitate breeding for resistance, but vigilance is required regarding the presence of other pathotypes. Indeed, a similar recommendation was already provided by Malvick and Grau () to alfalfa breeders, because of the two races identified within alfalfa isolates.…”

The quasi-universality of nestedness in the structure of quantitative plant-parasite interactions

“…In the present study, LSmeans values of root DS scores were analysed. More details are provided in Quillévéré-Hamard et al (2018).…”

Beheersing van bodempathogenen via bodemgezondheidsmaatregelen : Een overzicht van de beschikbare kennis voor een selectie van akkerbouwgewassen met hun bijbehorende bodemziekten

“…Veroorzaakt wortelrot en kiemplantuitval in vooral erwt maar ook andere peulvruchten, waaronder luzerne, tuinboon en wikke (Quillévéré et al, 2018). Er zijn ziektewerende gronden gevonden waarvan de werking biologisch is (Persson et al, 1999).…”