Resistance of the wild tomato Solanum habrochaites to Phytophthora infestans is governed by a major gene and polygenes.

This work aimed to study the inheritance of resistance to Phytophthora infestans in tomato plants, using the maximum likelihood estimation function. The susceptible cultivar Santa Clara (Solanum lycopersicum) was used as the female genitor and the P. infestans resistant S. habrochaites f. glabratum accession (BGH 6902) as the male genitor. F1 plants from the crossing were self-pollinated to produce F2 progenies, and also backcrossed with PR and PS to produce BC1:R and BC1:S generations, respectively. The tomato plants were inoculated 50 days after transplanting. Disease severity was evaluated via a diagrammatic scale. Comparison of the genetic models created using the maximum likelihood function revealed that the inheritance of resistance to P. infestans in S. habrochaites is conferred by a major gene with additive and dominance effects, polygenes with additive effects, plus the environmental effect. Vertical resistance can be explored using genes with major effects. Programs of recurrent and maker-assisted selection are considered efficient strategies with which to select genotypes that hold P. infestans resistance conferred by polygenes.