Evaluation of tomato genotypes for early blight disease resistance caused by Alternaria solani in Pakistan

Four hundred one tomato genotypes representing 11 species were screened against early blight (EB) disease caused by Alternaria solani in a net-house during 2013 to 2017. Considerable variation in resistance/susceptibility levels to EB was observed in the tested germplasm. Only one genotype ‘21396’ of Solanum lycopersicum was resistant and 56 were moderately resistant while the remaining were susceptible to highly susceptible. The pace of disease development was much slower in resistant genotype as symptoms were confined only to lower older leaves. The resistant genotype ‘21396’, most of the moderately resistant ones and a few susceptible and highly susceptible genotypes were rated resistant to stem and fruit infection. Resistant and moderately resistant S. lycopersicum genotypes and mutants with desirable characteristics could be grown in regions with high disease incidence, and can be used for the development of resistant/tolerant cultivars. The moderately resistant germplasm with very poor horticultural traits can nevertheless be used in resistance breeding programmes for developing superior cultivars and hybrids having new resistance genes to EB with a wider genetic base.