Variability among Alternaria solani isolates causing early blight of tomato.

摘要

Variability among isolates of Alternaria solani, the causal agent of early blight of tomato, from Northern and Southern parts of India, was determined based on conidial morphology, pathogenicity tests and random amplified polymorphic DNA (RAPD) technique. The isolates varied with respect to size of conidia and number of septa. The test isolates differed in the virulence pattern on ten tomato genotypes under screenhouse conditions. Isolates RAS (Rohtak) and HAS-I (Hisar) were more virulent than all other isolates. The analysis of RAPD profiles showed that there was a high level of genetic variability among the isolates of A. solani. The cluster analysis based on similarity coefficients separated the ten A. solani isolates into two major clusters. There was no evidence for geographical clustering of isolates with high levels of genetic similarity, suggesting that isolates are widely spread across India.