Híbridos de milho submetidos à restrição hídrica no semiárido mineiro

Abstract

This study aimed to evaluate the agronomic and physiological performance of four contrasting commercial corn hybrids for drought tolerance in environments with and without water restriction. The work was conducted at the Experimental Farm of Embrapa Milho e Sorgo, located in Nova Porteirinha city, North of Minas Gerais. Each plot consisted of four lines of 5 m in length and spacing of 0.8 m, the plot useful area was repsented by the two central rows. The treatments were arranged in a 2x4 factorial scheme, involving two cultivation environments (without water restriction and with water restriction) and four commercial hybrids contrasting as for drought tolerance, being these tolerant (DKB 390, BRS 1055) and sensitive ones (BRS1010 and 2B710) to that condition. The experimental design was a randomized block design, with four replications. The environment without water restriction was irrigated throughout the crop cycle, while in the environment with water restriction, irrigation was stopped for 35 days from pre-flowering (phenological stage V16), returning to irrigation after that. The evaluated productive variables were: length and diameter of corncobs, number of rows per corncobs, number of grains per row, corncobs weight and productivity; as well as biometric and physiological parameters: dry mass accumulation, insertion height of corncob, stomatal conductance, chlorophyll fluorescence, leaf area and relative content of chlorophyll determined by the SPAD index. It was verified that the water deficit affected the morphoagronomic performance of the plants, reducing dry matter production, leaf area, number of grains per row, corncob length and g and grains yield. It was observed that the tolerant hybrids, DKB 390 and BRS 1055, were superior to sensitive hybrids, BRS 1010 and 2B710, in dry mass accumulation, corncob quality and productivity. It is concluded that the hybrids DKB 390 and BRS 1055 are indicated for cultivation in the North of Minas Gerais, considering heir tolerance to drought and consequently greater adaptation to the edaphoclimatic conditions of the region.