Combining Ability and Heterosis of Maize Genotypes under Water Stress during Seed Germination and Seedling Emergence

Abstract

Early characterization of maize (Zea mays L.) genotypes, as well as the study of the genetic control of traits associated with water deficit tolerance, can provide information to guide breeders in the selection of cultivars adapted to drought environments. The aim of this study was to estimate heterosis and combining ability of maize genotypes under water stress during seed germination and seedling emergence. Four inbred lines previously characterized as water stress tolerant were crossed with four nontolerant lines in partial diallel scheme to obtain 16 hybrids and 16 reciprocals. Seeds were germinated in trays with sand in two environments, with and without water stress, with field capacity adjusted to 10 and 70% of humidity. The traits evaluated were seedling emergence, emergence speed index, shoot length, root length, number of seminal roots, and shoot and root dry weights. The heterosis effect, general combining ability, specific combining ability, and reciprocal effects were estimated for each trait using a partial diallel mixed model. The nonadditive effects were more important, and heterosis was observed in all cases, more expressively for root traits. The reciprocal effects were significant, highlighting the importance of the correct choice of the female parent to obtain maize hybrids tolerant to water stress.