Broad bean mottle virus in Morocco; variability, interaction with food legume species, and seed transmission in faba bean, pea, and chickpea

Abstract

Biological indexing of faba-bean samples collected during an earlier virus survey in Morocco revealed variation in symptom severity among isolates of broad bean mottle virus (BBMV). When seven selected isolates from Morocco and three from Algeria, Sudan, and Tunisia were further compared, they could be divided into mild, severe, and intermediate isolates, according to their pathogenicity on a number of food-legume genotypes tested. The Moroccan isolate SN1 and the Sudanese SuV256 were very mild, and deviant also in their effect onGomphrena globosa, whereas the Tunisian TV75-85 and the Moroccan VN5 were virulent. Representative isolates were indistinguishable, however, in coat-protein molecular weights, and they reacted similarly to the antisera to a Moroccan and a Syrian isolate in electro-blot immunoassay.

Promising ICARDA breeding lines and accessions—ten each of pea and lentil, nine of chickpea, and twelve of faba bean-were all found vulnerable (susceptible and sensitive) to all isolates. Within each food-legume species, vulnerability varied from high to moderate, and no immunity was detected. Virus concentrations in faba-bean lines suggest that isolates differ in virulence rather than in aggressiveness, and that the differences in vulnerability among the lines are due to differences in sensitivity rather than in susceptibility.

When pooled seed samples were germinated and seedlings were tested for BBMV in DASELISA, the virus was found seed-transmitted in faba bean, chickpea, and pea at transmission rates of ca 1.2, 0.9, and 0.1%, respectively. This is the first report on seed transmission of BBMV in faba bean, when occurring on its own, and the first record of such seed transmission in chickpea and pea.