Agronomic performance and genotypic variation among maize hybrids evaluated under two plant densities

In order to increase yield in maize, studies on plant population have been very relevant, since this factor has a high influence on the final grain yield of the crop. Thus, our aim was to assess the agronomic performance and the genotypic variation among maize hybrids under two plant densities. In the 2019/2020 summer season, we evaluated 121 single-cross hybrids developed by the breeding program of the Universidade Federal de Viçosa and seven commercial hybrids as checks under two plant densities (traditional – 60,000 and high 90,000 plants ha-1) at the Experimental Station of the university located in Coimbra, Minas Gerais. The traditional and high plant populations experiments were grown side-by-side on the same field, and each trial was laid out in an alpha-lattice incomplete block design with two replications. Plots were 4 m long, with two rows spaced 80 cm apart, and a plot size of 6.4 m2. We evaluated four traits: days to silking (DTS, days), days to pollen shedding (DPS, days), plant height (PH, cm), ear height (EH, cm) and grain yield (GY, kg ha-1). We found a large genotypic variation among maize hybrids for all traits tested under both plant densities. The coefficient of variation ranged from 1.13% (DPS) to 9.9% (GY) under traditional plant density, and from 1.45% (DPS) to 11.76% (GY) under high plant density. The estimates of broad-sense heritability ranged from 0.62 (DTS) to 0.94 (PH), and from 0.75 (DPS) to 0.90 (PH), under traditional and high plant densities, respectively. The average for GY was similar among the plant density experiments: 9,750 kg ha-1 and 9,545 kg ha-1 under traditional and high plant density, respectively. When we ranked the hybrids based on GY and compared the top 15 hybrids among both experiments, we observed that only three were selected under traditional and high plant density: VML093xVML029, VML032xVML118 and VML103xVML022. We concluded that the selection of maize hybrids for contrasting plant populations must be done under each plant population since the response of maize hybrids to plant density differs among them and the bests under lower plant density are different from the selected hybrids under high plant density.