Influence of the maize Sugary1 locus on genetics of economically important traits

Knowledge of genetic control of mutant viability is of great importance in maize breeding, particularly for mutants with deleterious effects. Little is known about the genetics of the viability of mutants and no previous report has been published concerning the genetic effects of the mutant sugary1 on agronomic traits. Our objective was to study the effects of the sweetcorn mutant sugary1 (su1) on the genetic effects of agronomic traits in two wild type corn backgrounds. Estimated genetic effects of agronomic traits in Su1 versus su1 plants were monitored through four successive selfpollination cycles in two separated mean generation designs. The first involved two Corn Belt inbred lines A619 and A632, while unrelated inbred lines EP42 and A631 were used for the second design. Parents, F₁s, F₂s, and backcrosses were crossed to the su1 inbred P39 as the donor of su1 and the 12 crosses were successively selfpollinated for 4 years. For each cross, Su1 and su1 seeds were separated and evaluated in 10 × 10 triple lattice designs. The Su1 plants showed higher performance than the su1 plants in almost all traits. The estimates of genetic effects of Su1 versus su1 plants were strongly affected by the su1 × wild type corn interactions. The introgression of su1 in wild type corn strongly affects the genetic effects of flowering time and, to a lesser stent, that of other plant or ear traits. Mutant viability is regulated by additive, dominance and digenic epistatic effects and the importance of those genetic effects depends on the genetic background and environmental conditions.