Yield and morphophysiological indices of irrigated rice genotypes in contrasting ecosystems1

ABSTRACT Rice phenology and development are events controlled by environmental and genetic factors, and the yield potential of the crop is defined by their interaction. This study aimed at analyzing the performance of irrigated rice genotypes in contrasting ecosystems and their effects on morphophysiological characteristics. Two ecosystems (tropical and subtropical) were analyzed, as well as cultivars recommended for tropical (BRS Catiana and BRS Jaçanã) and subtropical (BRS Pampa, BRS 7 Taim and IRGA 424) regions. The experiments were arranged in a complete randomized block design, with four replicates, being the factors the genotypes, sowing times and sites. The phenological development, biomass dynamics, radiation use efficiency and grain yield were evaluated. The accumulated degree-days demand for flowering decreased faster in the tropical ecosystem than in the subtropical ecosystem for late sowing. The radiation use efficiency values were similar in the subtropical ecosystem and yield was high for all sowing dates. On the other hand, the tropical ecosystem showed a high variation for radiation use efficiency values and yield. The higher accumulation of degree-days and solar radiation during the reproductive and grain-filling phases contributed to increase yield in both ecosystems.