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 (147.71 μm). 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.
Key words: Alternaria solani, early blight, survey, tomato