Genetics of resistance to early blight disease in crosses of wild derivatives of tomato

The objective of this study was to determine the heterosis, inbreeding depression and genetics for yield, quality and resistance to early blight in tomato. Consequently, twenty inter-specific crosses of tomato were developed by crossing five susceptible cultivars and four wild resistant accessions and tested in field and glasshouse conditions for early blight (EB) resistance. Biochemical responses were also critically studied both in parents and hybrids. All the crosses showed moderately susceptible reaction except five crosses of EC-520061 (Solanum habrochaites). Biochemically the wild parents exhibited better results over susceptible parents but their hybrids showed moderate reaction for early blight resistance. High level of phenol was found both in resistant parents and hybrids. Among the 20 crosses, those made by EC-520061 and H-88-78-1 manifested resistance capacity, low heterosis and high inbreeding depression for EB disease. For yield associated traits most of the crosses expressed high heterosis and low inbreeding depression which indicated better yield capacity. The crosses made by EC-520061 (S. habrochaites) segregated in 3:1 (resistant:susceptible) Mendelian ratio and indicated monogenic dominant and additive gene effects. Remaining crosses showed 1:2:1 (resistant:intermediate:susceptible) genetic ratio and indicated heterozygous nature of crosses mediated by multiple genes or QTLs. This fact can be utilized in future tomato breeding program for developing resistant varieties against EB disease.