Tolerância ao déficit hídrico em linhagens de milho

Abstract

Abiotic stresses such as water deficit can affect plant development and grain productivity. The identification and development of genotypes tolerant to water deficit are priorities in maize breeding programs. In addition to the evaluation of agronomic traits, it is important to study the expression of genes related to tolerance to water deficit in order to understand the mechanisms involved in this trait, aiming at the development of tools that can be used in breeding programs. Thus, the objective was to evaluate the agronomic characteristics related to tolerance to water deficit in maize lines grown at different plant densities. The expression of genes associated with tolerance to water stress was also evaluated, using the qRT-PCR technique, in different plant tissues of maize lines. For the evaluation of the agronomic characteristics, lines were used, which were evaluated in previous experiments, contrasting in terms of tolerance to water deficit. Experiments were installed using two plant densities, 60 and 120 thousand plants in the second crops of the years 2019 and 2020. Under these conditions, the following characteristics were evaluated: Female Flowering (FF), Male Flowering. (FM), Male and Female Flowering Interval (IFMF), Plant Height (APl), First Ear Insertion Height (AIE), Stem Diameter (DC) Prolificity (PROL), Grain Weight of each subplot (KG /P), Ear Weight (EP), Ear Length (EC), Number of grains per ear (NGE), Stay Green (S.Green). In the two harvests, higher IFMF was observed in lines classified as non-tolerant to water deficit, 24 and 57. For the APL and AIE characteristics, in the two harvests, higher values were observed in plants developed in the largest plant population, and greater APL was observed in plants from lines classified as non-tolerant to water deficit, lines 57 and 24. Higher ear weight was observed in line 91, classified as tolerant to water deficit, and lower weight of ear and smaller number of grains per ear were observed in line 24, classified as non-tolerant. As for the S. Green variable, the plants of the tolerant lines, 91 and 32, remained green for a longer time. In the two seasons evaluated, higher grain production was observed in tolerant lines, 91, 63 and 32, and lower in line 24. Thus, considering the agronomic characteristics, line 91 was more tolerant to water deficit. Regarding gene expression, there was difference between different genotypes, tissues, and population densities. Higher expression of the ZmDREB2A/2.1S gene was observed in tissues of plants from the tolerant lineage, L91-T, and for the ZmPP2C gene, higher expression was observed in tissues of the non-tolerant lineage, L24-NT. For these genes, in general, higher expression was observed in leaves developed at a largest density of plants . In general, for genes related to antioxidant enzymes, SOD and CAT 3, higher expression was observed in leaves and stems of plants of the non-tolerant strain, L24-NT. Thus, the genes ZmDREB2A/2.1S and ZmPP2C are suggested as potential molecular markers to assist breeding programs aimed at developing cultivars for tolerance to water deficit.