Características agronômicas e expressão de enzimas relacionadas à tolerância ao déficit hídrico em linhagens de milho

Abstract

Stress due to low water availability is one of the factors that most limit the development of the maize crop. In this way, the selection of genotypes with tolerance to water deficit is sought through genetic improvement programs. The use of indirect characters related to tolerance to water deficit can help in breeding programs for cultivars selection. Also, the evaluation of enzyme expressions associated with drought tolerance can be a tool aiming the development of cultivars with greater tolerance to water deficit. The objective of this research was to evaluate the agronomic traits and the expression of enzymes related to tolerance to water deficit in maize lines. Four contrasting lines were used, with two lines classified as tolerant (T), L91-T and L63-T, and two non-tolerant (NT), L57-NT and L24-NT, to water deficit. The experiment was carried out using two plant populations, 60 and 120 thousand plants. ha-1. Under these conditions, the following indirect traits related to drought tolerance were evaluated: female and male flowers, interval between male and female flowers, prolificacy, plant height, first ear insertion height, tassel height, number of grain rows in the ear, grain yield and weight of 100 grains. The enzymatic activity of the enzymes catalase (CAT), superoxide dismutase (SOD) and ascorbate peroxidase (APX) in leaves, adventitious roots and tip of the spike were also evaluated. Higher plant heights, first ear and tassel insertion, and higher yields were observed when the population of 120,000 plants ha-1 plants was used. Greater grain yield was observed for line 24, in which a larger number of grains rows were also observed. Larger ranges of male and female flowering were observed in plants of lines 57 and 24 when the highest population density was used. Higher activity of the enzyme ascorbate peroxidase was observed in leaves and tip of the spike when the plant population was increased. For SOD and CAT enzymes, higher activity was observed in all tissues when the population density of 60,000 plants ha-1 was used. It can be concluded that there is an increase in the height of plants, height of insertion of the first spike and height of the tassel when the population density of corn plants is increased. And in higher population densities, used to simulate water deficiency, there is an increase between the male and female flowering intervals in non-drought tolerant strains. In relation to the enzymatic activity it can be concluded that there is a greater activity of the enzyme ascorbate peroxidase in the leaves and tip of the spike when the highest population density of plants was used in order to simulate water deficiency. In relation to the enzymatic activity it can be concluded that the APX and SOD enzymes vary between tissue and population density, whereas the activity of the CAT enzyme varies between tissue, population density and genotype.