ABSTRACT
Early blight of tomato incited by Alternaria solani is an economically significant disease especially in commercial tomato cultivation under greenhouse and field conditions. Since, A. solani is a shy sporulator, the present investigation was taken to assess the optimum in vitro conditons for growth and sporulation of early blight pathogen. Ten A. solani isolates obtained from diseased leaf samples collected different crop growing areas of India were used in the present study. The effect of different incubation periods, fluorescent light, cold-water treatment and media were evaluated. Our results revealed maximum sporulation of A. solani on tomato fruit extract agar medium (TFEA) under continuous light for 7 days at 250C, followed by cold-water treatment and further incubated in darkness at 200C for 48 h. The sporulation of test pathogen was however sparse on V-8 juice agar. Further, the A. solani isolates on V-8 juice agar did not respond to the treatments imposed. Among the isolates, JAS (Jhajjar) isolate, that is more versatile in its ability to produce spores recorded irregular margin with abundant aerial mycelium.