Growth and morphology of grain sorghum hybrids cultivated in semi-arid region under pre- and post-flowering drought stress

Abstract

Drought stress is a major factor limiting sorghum yield, especially in regions with irregular rainfall. This study investigated the morphophysiological and growth responses of grain sorghum hybrids to drought stress, comparing the effects at pre- and post-flowering stages. Twenty hybrids were evaluated under well-watered conditions and under drought imposed at the pre- and post-flowering stages, using a randomized complete block design, with three replications. The evaluated traits were plant height, leaf area index, shoot dry weight, and chlorophyll index. Growth parameters, including absolute growth rate, relative growth rate, leaf area ratio, leaf weight ratio, specific leaf area, and net assimilation rate, were also determined. The pre-flowering drought caused the greatest reductions in plant height, leaf area index, and dry weight accumulation, whereas the post-flowering drought had the greatest effect on leaf area ratio, chlorophyll index, and net assimilation rate. The grain yield under pre-flowering water stress was approximately 4,000 kg ha-1, significantly higher than the 2,500 kg ha-1 observed under post-flowering stress, suggesting a greater capacity for recovery and grain production when water availability is restored before the reproductive stage.

KEYWORDS: Sorghum bicolor L., abiotic stress, sorghum breeding.