Influência dos ambientes e dos genótipos nas taxas de indução de haploidia em milho

Abstract

Corn (Zea mays L.) is one of the most important cultivated cereals in Brazil, with predominance of hybrid cultivars. The double-haploid technique revolutionized the corn breeding programs by significantly reduce the time required to achieve genetic homozygosity in inbred lines for subsequent hybrid production. When haploid cells successfully undergo chromosome duplication, whether induced naturally or intentionally, they generate a double-haploid genotype. Nowadays there are several methods for obtaining double-haploids lines in corn, following four main steps: source genotype induction; haploids seeds identification; haploids chromosomes duplication and attainment of the double-haploid lines. Environmental diversity is a relevant factor that can influence this process. For corn, altitude is a key environmental factor that has a direct effect on temperature which affects plant photosynthesis and respiration. Generally, depending on the genotype adaptability, corn hybrids grown at higher altitudes show an increased yielding. So, the hypothesis of this study was evaluated whether the altitude where double-haploid corn is obtained can significantly affect the haploidy induction rate and the overall process efficiency. In addition to altitude, the growing seasons, the inducers type and the genotypes were also evaluated. Four corn genotypes with different textures and grain types were induced. The experiments were conducted at different altitudes, in Cristalina (GO) and Porto Nacional (TO), during the main season and during the off-season crop. The separation of haploid and diploid seeds was carried out based on morphological markers. The results demonstrated significant variation in the haploid induction rate (HIR) as a function of the evaluated environments, with values ranging from 1.59% to 3.50% and an overall mean of 2.38%. Higher induction efficiency was observed in second-season environments, highlighting the influence of environmental conditions. Analysis of variance confirmed significant effects of location, planting season, inducer origin, and inducer type, with planting season being the most influential factor. Overall, the interaction between environmental and genetic factors determines the efficiency of haploid induction, contributing to the optimization of doubled haploid production and improved efficiency in maize breeding programs.