Six consecutive field evaluations to screen 25 tomato genotypes for resistance to tomato leaf curl virus on the basis of symptomatology under three environmental conditions: early autumn (planting in last week of August), autumn-winter (planting in second week of October) and spring-summer (planting in first week of February) revealed that percent disease incidence and coefficient of infection (CI) in the genotypes was highest in early autumn followed by autumn-winter and spring-summer seasons suggesting significant influence of environment on symptom expression. The three moderately resistant lines, H-24, Agata and EC-321425 (CI 2–6) were crossed with five highly susceptible testers (CI above 21) namely, Punjab Chhuhara, Pusa Ruby, Ratan, Hisar Arun and Patharkutchi in line x tester mating design. The hybrids recorded a range of intermediate disease reaction and mean squares for four disease parameters varied widely in two seasons suggesting polygenic nature of disease resistance. Magnitude of both gca and sca variances for all the disease parameters were prone to change with the environment. In the early autumn season, being the most favourable season for disease development and severity, overwhelming presence of additive genetic component was recorded for TLCV resistance where as in autumn-winter season, both additive and dominance gene effects was equally important seemingly revealing complicated inheritance of resistance. Higher total phenol content in the leaves particularly at 30 days growth stage appeared to have determined the resistance actively in the host. Pedigree selection from the promising cross like H-24 x Ratan is suggested but quite high non-additive variance in the control of disease resistance may lead to bias in favour of heterozygotes in early segregating populations. So, the main aim must be to get homozygosity first, while reserving selection pressure for the later generations. Exploitable level of disease resistance could be achieved in few hybrids involving moderately resistant/resistant x susceptible cross.
