Physiological Studies on Stemphylium vesicarium Causing Stemphylium Blight of Onion

Stemphylium vesicarium the causal agent of Stemphylium blight of onion had incubation period of 5 and 3 days whereas, 7 and 5 days of latent period on potted plants and detached leaves, respectively. The inoculum level i.e., 3x10⁴ conidia/ml, required minimum incubation period for disease expression and development whereas at lower level i.e., 1x10⁴ conidia/ml, the incubation period increased resulting in less disease severity. The effect of different culture media and temperatures on mycelial growth and sporulation of S. vesicarium of onion was investigated. Maximum colony growth of S. vesicarium was recorded on Potato dextrose agar (PDA) and Oatmeal agar while the highest sporulation was observed on Oatmeal agar and V8 agar media. Similarly, maximum colony growth of S. vesicarium was recorded between 20℃ and 25℃ temperature. Whereas, high sporulation was recorded at 15℃ while at 20oC and 25℃ a good amount of spore production was observed.