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Keywords:

  • aggressiveness;
  • alternative host;
  • host plant;
  • Mycosphaerella pinodes ;
  • Pisum sativum ;
  • specialization

Ascochyta blight, caused by the polyphagous fungus Didymella pinodes, is one of the most economically damaging diseases of pea. Susceptibility/resistance of several legume species to several D. pinodes isolates from pea was assessed under controlled environmental conditions to test the hypothesis that D. pinodes was host-specific. Forty-three cultivars of five legume species (pea, common vetch, clover, alfalfa and faba bean) typically grown in temperate climates were screened with four pea-infecting isolates from France, and one pea-infecting isolate from Australia. Seven days after inoculation, disease incidence and necrosis were measured on foliar organs to estimate aggressiveness of the isolates. Cultivars of each legume species displayed differential resistance/susceptibility to each isolate as indicated by significant cultivar × isolate interactions in anova. Faba bean, common vetch, alfalfa and clover cultivars were consistently less susceptible than pea cultivars regardless of the inoculated isolate. The behaviour of D. pinodes isolates also indicated various patterns of disease development according to the legume species and the cultivars. Genetic distance between the five legume species was not correlated with overall differences in susceptibility, indicating that D. pinodes is not specialized to pea and shows a wide host range among legume species. Disease risk assessment in the pea crop should therefore consider the vicinity of cultivated and wild legume species that may serve as alternative hosts for D. pinodes.