Indicadores fisiológicos agronômicos para seleção de genótipos de sorgo granífero tolerantes à restrição hídrica

Abstract

Water stress is a major constraint in food production, especially in arid and semi-arid regions. In this way, there is a growing demand to select crops that can survive under extreme environmental conditions. The objective was to evaluate physiological and morphological characteristics as indicators for selection of sorghum genotypes tolerant to water restriction. The experiments were conducted in 2014, 2015 and 2016. Two trials were installed each year, one of which was submitted to full irrigation and the other to water restriction. In the first one the irrigation was performed periodically, with irrigation shift every two days to maintain soil moisture near the field capacity, while in the second irrigation was cut in the pre-flowering period, and this stress was maintained for 30 days. Four sorghum genotypes were used for drought tolerance: 9503062 and 9618158 - susceptible to drought (S); 9910032 and P898012 - tolerant to drought (T), which consisted of the treatments. The experimental design was in complete randomized blocks, with four replications, totaling 16 plots. At the end of the water restriction period, stomatal conductance, relative chlorophyll content, chlorophyll fluorescence (fv/fm) and photosynthetically active leaf area were evaluated. At the time of harvest, plant height, panicle weight, grain weight per panicle and yield were evaluated. A joint analysis of the experiments submitted to full irrigation and to the water restriction of the three years was performed. Under water restriction, it was not possible to distinguish the sensitive materials from the tolerant ones through the evaluations. The characteristics evaluated in this experiment did not allow a conclusive distinction between the tolerant and the sensitive genotypes.