Studies on Factors Affecting the Pathogenesis of Alternaria Solani (Ell. And Mart.) Jones and Grout On Tomato (Solanum Lycopersicum Mill.)

Abstract

Development of disease is essential to study the various aspects of pathogen for the management of disease. Hence, the present study was conducted to ascertain the effect of inoculum load, age of pathogen culture, subculturing and host age on the development of early blight of tomato. Five conidial concentrations viz., 5x10³, 1x10⁴, 5x10⁴, 1x10⁵ and 5x10⁵ conidia/ml were evaluated. Alternaria solani inoculum load of 5x105 spores/ml gave maximum disease severity (34.60%) with shortest incubation period of 3.0 days followed by 1x10⁵ (31.53%) with 4.2 days of incubation period. The findings of the present study suggested that 14 days old culture of A. solani as compared to 7, 21, 28 and 35 days old was most virulent with highest mean disease severity (27.47%) and shortest incubation period (3.6 days). The shortest incubation period (3.0 days) was observed with first sub-culture as compared to 2^nd, 3^rd, 4^th and 5^th subcultures, which resulted in highest mean disease severity (31.13%). The results for the second sub-culture were also found to be at par. This indicated that the pathogen was most virulent up to second sub-culturing and that successive sub-cultures reduced the inoculum potential. The disease was observed more on the mature plants as compared to younger plant. It was also found that tomato plants of 50-60 days after sowing are most susceptible to early blight infection with maximum disease severity of 37.80 per cent and host plant most likely exhibited only seedling resistance against the necrotrophic pathogen A. solani