Isolation and physicochemical test studies of Ascochyta pisi

R. Terbeche, Department of Biology, University of Oran, Algeria


Anthracnose caused by pea Ascocgyta pisi is one of the most serious diseases affecting crops of peas (Pisum sativum L.) worldwide. In Algeria, more precisely in the north-west, quantitative data on the incidence of the disease is not available; it proved essential as a first step to isolate the pathogen and study in vitro the physicochemical factors affecting its growth. 10 strains were selected from 32 isolates from infected plants. The results indicate that the degree of the temperature of incubation affects the mycelia growth, at 4°C, mycelia growth was slowed and 37 °C inhibits the mycelia growth. We recorder that the optimum growth is between 22 and 25°C. Relative humidity affects the mycelia growth of the strains, the rate ≤ 50%, it is low at 74%, it is average, and other rate ≥ 80%, and it is optimal.. The usual media used (PDA, Malt, Mathur) give a good mycelia growth of the strains, but some have very low growth in the middle of pea; Overall, the usual empirical media used do not affect the mycelia growth of the strains. All strains assimilate the different carbon sources, however, is optimal mycelia growth on the (lactose, maltose and starch), the average (glucose, fructose), and weak on the cellulose. Mycelia growth is optimal on low nitrogen sources NaNO3, KNO3 and asparagine, on Valine, Leucine and L-arginine media, and slowed on the environment (NH4)2SO4 the nature of the nitrogen source influences on the growth of the strains.