Análise dialélica e estratégias para a seleção de genótipos de milho submetidos ao estresse hídrico nas fases de germinação e emergência de plântulas

Abstract

Early characterization of maize genotypes, as well as the study of genetic traits associated with water stress tolerance, can provide parameters that will assist in the selection of adapted cultivars with higher yield. This research aims the study of genetic control and evaluate strategies for maize genotypes selection, through physiological quality of seeds submitted to water stress. A field was installed to obtain hybrid seeds, including reciprocal hybrid, using partial diallel design, further eight progenitors inbred line (L91, L63, L37, L32 – group 1 (tolerant); L75, L31, L57 e L24 – group 2 (non-tolerant)), previous characterized in relation to water stress. All seed genotypes were germinated in trays with sand, in two environments. The first, called “without stress environment”, had its field capacity adjusted to 70%, and the second, called stress environment, with field capacity of 10%. It was assessed the seedling emergence, emergence speed index (IVE), shoot length (CPA), root length (CR), number of seminal roots (NR), shoot dry weight (PSF) and roots dry weight (PSR). The heterosis effect, the general combining ability (GCA), the specific combining ability (SCA) and the reciprocal effects were estimated. The genotype performance in relation to water stress was assessed by principal components analyzes, selection index regarding to water stress tolerance (IS), Z index, and classification graphic as tolerance and responsiveness. Heterosis is observed for water stress tolerance, manly for root traits. In the genetic control of water stress tolerance, non-additive genes are more important for most of the evaluated characteristics. Higher estimates of GCA are observed in L91, L75 and L63 lines, and higher estimates of SCA in H91 x75, H91x24, H91x31 and H63x31 hybrids. There are reciprocal effects for physiological quality of seeds. The selection index (IS) is efficient to separate maize genotypes regarding water stress tolerance by NR characteristic. Classification graphic regarding tolerance and responsiveness methods, Z index and principal components analyzes allows superior genotypes selection regarding water stress tolerance. L91, L75, H91x75, R75x91, R57x91, R31x63, R31x91 e R24x91 genotypes shown to be the most promising for water stress tolerance on germination.