Genetics of tolerance to bacterial wilt disease in tomato (Solanum lycopersicum L.)

Tomato production in the Gangetic plains of eastern India is threatened by high incidence of bacterial wilt (BW) disease caused by Ralstonia solanacearum. Understanding the genetic control of tolerance through utilization of tolerant genotype is the prerequisite to frame effective resistant breeding strategy. Genetic control of host tolerance to BW disease was studied employing six generations (P1, P2, F1, F2, BC1, BC2) of two crosses between one tolerant (Utkal Kumari) and two susceptible (CLN-2498D and CLN-2777F) genotype(s) in presence of the predominant virulent strain (Biovar IIIA) of Ralstonia solanacearum through χ2 test and generation mean analysis. It emerged that tolerance to BW disease was conditioned predominantly by single dominant gene in two Tolerant × Susceptible crosses however, significance of scaling tests revealed involvement of duplicate epistasis suggesting somewhat complex inheritance pattern for the tolerance. Area under disease progress-curve (AUDPC) suggested that cumulative disease progress was less in tolerant genotypes of segregating generations. Duplicate epistasis controlling BW disease incidence suggested mild selection intensity in earlier generation, while intense in later generations of the segregating population in tomato. In this situation, modified bulk method of selection is recommended, in which selection is performed after attaining the homozygosity for maximum heterozygous loci. However, development of hybrids involving at least one tolerant parent is the best option for breeding tomato against BW disease.