EVALUATION OF TOMATO GENOTYPES FOR LATE BLIGHT RESISTANCE USING LOW TUNNEL ASSAY

Abstract

Late blight (LB) caused by Phytophthora infestans is one of the major bottlenecks of low productivity of tomato worldwide including Pakistan. Transfer of resistance into elite lines is the principal way to combat this problem. However, lack of reliable methods to screen and evaluate plant resistance prior to breeding has been a limiting factor in the development of tomato varieties resistant to LB. In the present study, we screened 285 tomato genotypes of diverse genetic pool using a low tunnel assay for the first time to the best of our knowledge and confirmed that it is not an established method in use for the same purpose. Results over the multiyear (2013-2015) elucidated one resistant genotype LO6122 (Solanum arcanum) and 31 moderately resistant genotypes (one of S. arcanum and 30 of S. lycopersicum) to LB. Rest of the genotypes including mutants and differential plants having major LB resistant genes (Ph1, Ph2, Ph3 and Ph2 + Ph3) were ranged from susceptible to highly susceptible. Strong resistance conferred by LO6122 points out the presence of an alternate source of genes resistant to LB. Therefore, this line can possibly be used as a donor parent of resistance against virulent strains of P. infestans. This study also showed that low tunnel assay is practicable, efficient, simple, and cost effective in terms of space and pathogen inoculum required. It gives high output results to distinguish resistant and susceptible genotypes even when screening of large number of genotypes and breeding populations against LB is exercised.