Prevalence of tomato early blight disease in Tamilnadu and morpho-cultural characterization of Alternaria solani isolates

The present study was conducted with an objective to assess the prevalence and incidence of tomato early blight disease at different locations in five districts of Tamilnadu, India during 2016. The growth characters and pathogenic variability among the isolates of Alternaria solani were recorded. The survey revealed that the per cent disease index ranged from 12.52 to 34.72 per cent among five tomato growing districts. Amongst the collected isolates AS₅ showed maximum radial growth (88.56mm), conidial size (265.63µm x 23.28µm) and beak length (147.71µm). The same isolate was also found as most aggressive with maximum per cent disease incidence (69.46%) on artificial inoculation. The pigmentation, sporulation, growth margin and zonation were also found to vary amongst different isolates. AS₅ was found most aggressive with maximum per cent disease index (69.46%) followed by AS₂, AS₉ and AS₆ with a PDI of 65.42, 56.74 and 52.41 per cent, respectively. The least PDI (24.38%) was recorded with isolate AS₈.