Características morfofisiológicas de linhagens de milho para tolerância à seca cultivadas em dois regimes hídricos

Abstract

Plants are exposed to various environmental stresses during their growth and development under natural and agricultural conditions. Among them, water stress is one of the most severe. Considering the hypothesis that maize has great variability for secondary traits in response to drought stress and that those traits have high heritability, which can help breeders in the selection of drought stress tolerant genotypes. Two experiments were carried out with six inbred lines with different genetic background to drought tolerance, belonging to Embrapa Maize and Sorghum Breeding’s Program in greenhouse and field conditions. The goal of those trials was to evaluate the effects of drought stress on morphofisiological traits and their effect on yield production. The response variables evaluated were chlorophyll fluorescence, gas exchange (only the foliar greenhouse experiment), leaf anatomy and yield (only in the field experiment), in two different water regimes (field capacity and 50% of the soil capacity). In greenhouse condition, the drought tolerant inbred lines showed higher PSII efficiency, low photosynthesis, and transpiration values, leading those genotypes having a higher WUE. The leaf anatomy of the drought tolerant inbred lines showed significant and positive alterations, with no effect on photosynthesis capacity in drought stress conditions. Leaf anatomy and photosynthesis data indicate that drought stress tolerant inbred lines used stomata to regulate gas exchange, avoiding water loss, with consequently increase on WUE. The anatomical traits are directly correlated with yield gains observed on drought tolerant inbred lines. G176-11.2.1 and 521233 genotypes showed higher yields on the drought stressed condition. The yield data showed strong correlation to leaf anatomy and 1000 kernel weight. According to the results findings in these studies, it is plausible to say that morphophysiological traits, are useful tools to assist breeding programs in the selection of cultivars drought stress tolerant.