Mass sporulation of Alternaria solani causing early blight of tomato

The studies were carried out to assess the effect of moisture, light, darkness and UV light on conidial production of Alternaria solani , causing early blight on tomato ( Solanum lycopersicum L.). The sporulation of Alternaria solani is often reduced when test pathogen is cultivated in vitro on grain-based media. The study was done on five grain based media (wheat, sorghum, barley, maize and pearlmillet) to assess the effect of moisture, light quality, darkness quality and UV light on conidial production. Excellent colonization with sporulation (4.50 x 10 3 ) was found with sorghum grains at 25±2°C after 30 DAI (days after incubation). The varying moisture content of substrates gave diversified colonization and sporulation of test pathogen on sorghum grain-based media. Ten g grains: 8 ml water gave best sporulation (1.00 x 10 4 ). This technique is cost-effective, rapid and reliable since it does not require use of agar and chemicals. Of the five most virulent isolates used for spore production on sorghum grains, Asv-2 gave maximum sporulation (1.0 x 10 4 ) 30 days after incubation. The pathogen produced maximum spores (5800 spores/ml on PDA and 5600 spores/ml on PDB) under UV light exposure for 20 second. Maximum spore concentration of 5.9 x 10 3 /ml was observed in 24 hr light coupled with 24 hr dark along with 30 minutes exposure to sun on PDA.