EFFECT OF WATER DEFICIT ON THE DEVELOPMENT AND GRAIN YIELD OF FOUR UPLAND RICE CULTIVARS

Abstract

Rainfed upland rice is subject to multiple abiotic stresses. Among them, water deficit is the most common one, due to periods without precipitation or with less precipitation than the water plant requirements. This stress is responsible for grain yield variation among years. This study intends to analyze the effects of water deficit on the development and yield components of four cultivars, two early cycle (Guarani and Soberana), and two medium cycle (Curinga and Primavera). Two independent experiments, one with and another without water stress, were carried out at the Agenciarural Experiment Station, in Porangatu, Goiás State, Brazil. It was concluded that the water deficit reduced grain yield, by reducing the number of panicles and grains per panicle, and increasing spikelet sterility. The difference in grain yield, among rice cultivars under water stress, was conditioned to the proximity of the period of maximum stress intensity, in relation to the flowering date. The lowest grain yield of early cultivars under water deficiency was due to the coincidence of their flowering date with the period of maximum stress intensity. Rice cultivars did not differ in grain yield, in irrigated conditions. However, under water deficit, the medium cycle cultivar Curinga presented the highest productivity.

KEY-WORDS: Oryza sativa L.; flowering date; cycle duration.