Screening of Tomato Genotypes against Early Blight (Alternaria solani) by Detached Leaf Method

Early blight (EB) caused by fungus Alternaria solani, is a destructive fungal disease of tomato (Lycopersicon esculentum Mill.) in India and elsewhere. 52 genotypes of tomato were screened for early blight disease resistance under artificial inoculation by detached leaf method including resistant and susceptible checks. The test genotypes under artificial conditions were grouped into six distinct categories based on Percentage Disease Index (PDI) at 7 days after inoculation and disease was recorded using 0-4 scale. Four genotypes EC 251709, EC 251717, EC 164295 and LE 15 showed highly resistant reaction with PDI ranged from 0-10%; whereas LE 44 was resistant (PDI 10.1-25%); EC 165690, EC 163681, EC 136711, EC 163683, LE 16, LE 35, LE 54, LE 85, LE-172 and LE-189 were moderately resistant (PDI 25.1-40%). The disease reaction (PDI) in other 23 ranged between 40-50% and categorized as susceptible. 11 genotypes were found highly susceptible with PDI more than 50%. The resistant genotypes identified were very poor in their horticultural traits and yield, thus, these resistance sources can not be exploited directly but it can be used in resistance breeding programme for developing superior cultivars and hybrids having resistance to early blight.