Comparative growth and pathogenicity of geographical isolates of Sclerotinia sclerotiorum on lentil genotypes

Isolates of Sclerotinia sclerotiorum were collected from infected lentil plants from 2 agro-ecological zones of Syria and used to study their comparative growth on culture media and pathogenicity on different lentil genotypes. The growth studies were carried out on Potato Dextrose Agar (PDA) growth media under laboratory conditions. Mycelial radial growth and sclerotial production were the parameters used to compare the isolates. Pathogenicity studies were carried out with selected isolates on 10 lentil genotypes, infected as detached shoots and as whole potted-plants in the plastic house. The isolates showed considerable variation in cultural characteristics through mycelial growth, mycelial pigmentation and sclerotial production in the media plates. There were significant differences in the growth and sclerotial production of most of the isolates, but no apparent correlation between mycelial growth and sclerotial production among the isolates. Genotype by isolate interactions was significant for the isolates tested for pathogenicity. These interactions, however, appeared to be caused by differences in virulence of the isolates and did not suggest the occurrence of distinct pathogenic races of the pathogen isolates.