Inheritance of blossom end rot resistance induced by drought stress and of associated stomatal densities in tomatoes

Abstract

The tomato crop is heavily dependent on irrigation, and water deficits may reduce yields and affect ion transport: calcium (Ca) transport may be affected, resulting in increased incidence of fruit blossom end rot (BER), a physiological disorder that renders fruit useless. Tomato lines were obtained with high levels of tolerance to BER induced by water stress. This paper reports on the inheritance of resistance to water-stress induced BER, and its association with reduced stomatal densities. A BER-resistant tomato line BPX-441D-88 (= P2) was used in crosses with the standard BER-susceptible line TOM-760 (= P1), and seeds of F1(P1 × P2), F2(P1 × P2), F1BC1(1) (= F1 × P1) and F1BC1(2) (= F1 × P2) were obtained. These populations were used in trials under water deficit, and genetic analysis of data was performed. Results indicated that that BER incidence was under control of a single major gene locus with partial dominance of the allele that controls lower incidence—a locus whose expression is influenced by modifier polygenes also with predominantly dominant gene action. BER incidence was found to be highly associated with a lower stomatal density in the adaxial leaf surface—a trait found to be under control of a single gene locus, with predominantly additive gene effects, and with no evidence of modifier polygenes. The high correlation found between BER incidence and lower adaxial stomatal densities suggest that the same major gene locus may affect both traits, and indicates that selection for lower adaxial stomatal densities may be effective in increasing resistance to drought-stress induced BER.