Grain sorghum hybrids under drought stress and full-irrigation conditions in the Brazilian Semiarid

In Brazil, grain sorghum has been mainly grown in Cerrado biome during the off-season, as a succession crop, after the soybean harvest. At this period, rainfall is erratic and insufficient, causing drought stress in pre- or post-flowering of grain sorghum crops. In this scenario, the identification of both drought-tolerant and irrigation responsive hybrids has been one of the main targets of sorghum breeding programmes. The hypothesis of this research was that grain sorghum genotypes respond differently to different moments of water deficit. This study aimed to evaluate the agronomic performance of sorghum hybrids under full irrigation and drought stress at pre- and post-flowering, in order to identify hybrids tolerant to drought stress and responsive to the water supply. Field trials were carried out in Nova Porteirinha during the 2017/2018 and 2018/2019 crop seasons. Twelve grain sorghum single-hybrids were evaluated for days to flowering and grain yield in three water availability conditions: drought stress at pre-flowering, drought stress at post-flowering and full-irrigation (control). Tolerant hybrids were identified under both pre- and post-flowering drought stress, as well as hybrids responsive to irrigation. The hybrids 1G282 and 116,748 stood out in the 2017/18 season for high yield and earliness under both drought-stress conditions, while the hybrid 1G282, AG1090, AS4625 and DKB590 stood out for the 2018/19 season in both stress condition. The hybrid A9904 and 1G282 stood out for its responsiveness to water supply, being recommended to high-tech farming systems that employ irrigation or for in-season cultivation.