Study of variability and sporulation by isolates of alternaria solani of lycopersicon esculentum (mill.)

Alternaria solani was studied on various parameters of cultural characters such as radial growth, pigmentation, pH, temperatures sporulation and differential host response. Among five isolates maximum radial growth was found in Sh isolates (75.2 mm) while minimum in Va isolates (56.5 mm). The maximum thickness of conidiogenous hyphae was recorded in Va isolate (9.56) and minimum (1.7) in Mi, Ba and Sh. Alternaria solani grew well on Czapek dox agar medium and Jenson medium. The maximum average radial growth was recorded 54.7 mm on PDA. The optimum temperature was recorded 25 oC with pH 7.5 for the pathogen. Pigmentation varied from brown to black color on these media, light yellow to black color at different temperatures and gray to brown color on different pH ranges. The sporulation was not found at any tested media, pH and temperatures except host decoction media. A method of inducing sporulation on host decoction media has been developed. Now it is possible to produce mature conidia in culture under aseptic condition in 20-25 days at 28 o C and pH 6.5. Septation of conidia were found to be greater in number from infected tomato leaves and fruits.