Diversity Assessment Among Alternaria solani Isolates Causing Early Blight of Tomato in India

Early blight (EB), caused by the fungus, Alternaria solani, is one of the most destructive diseases of tomatoes and other solanaceous crops; particularly in warm and humid climate. This study was targeted to explore the genetic and pathogenic diversity of A. solani from major tomato producing states of India. Thirty-three isolates were chosen for this study. These isolates exhibited considerable intra as well as inter-state variation. The phylogenetic tree generated with the ISSR sequences confirmed this result. Aggressiveness of the isolates towards susceptible tomato genotype was assessed in vitro, using detached leaf method. Considerable amount of variability in virulence was observed among the isolates. Specific activity of polygalacturonase and pectin methyl esterase was also estimated, to observe the relation among these, with the virulence of isolates. The information generated in the present study provides initial data on the population variability of the EB pathogen. It could be a valuable aid for tomato breeding strategies, aimed at obtaining cultivars with resilient resistance. This will provide a basis for planning disease protection strategies for sustainable agriculture which is required for producing crop plants which harmonize with the environment. © 2018, The National Academy of Sciences, India.