Comparative analysis of water-use behavior and drought resilience in selected tropical sorghum (Sorghum bicolor L.) cultivars

Highlights

• Water use of sorghum cultivars studied with high-throughput physiological phenotyping platform.
• Drought tolerances among cultivars are related to differences in critical soil water content (Ɵcrit).
• Water-conserving cultivars (i.e., cv. Numbu and cv. Samurai2) had better resilience to drought.
• Knowledge of Ɵcrit could support the breeding of drought resilience cultivars.

Abstract

Sorghum is an important crop for climate change adaptation, especially in drought-prone areas of the tropics. Our study aimed to identify how physiological and agronomic traits of different sorghum cultivars respond to drought stress. We utilized a high-throughput functional phenotyping platform to monitor growth and physiological characteristics of three tropical sorghum cultivars subjected to extended drought. Notable variations in cultivar response to water stress regarding morphological, agronomic and physiological traits were observed. In cv. Kuali, we observed a 21 % and 55 % reduction in plant height and total tiller number, respectively, under drought. In contrast, cv. Numbu showed only marginal reductions of 5 % and 28 % and cv. Samurai2, 8 % and 39 %, of plant height and total tiller number, respectively. The drought induced reductions in cv. Samurai were lower than in cv. Kuali but higher than in cv. Numbu. The reduction of the cumulated daily transpiration in response to drought was 52 %, 24 % and 5 % for cv. Kuali, cv. Numbu, and cv. Samurai2, respectively. Under high soil water content, cv. Kuali showed high transpiration which quickly declined after the point of physiological drought stress (Ɵcrit) was reached, representing typical non-conserving water use behavior. In contrast, cv. Numbu with much lower transpiration under high soil water content only reduced transpiration gradually beyond Ɵcrit making it a typical water conserver. Cv. Samurai was an intermediate between the two. Upon re-irrigation, all cultivars re-increased transpiration rates, especially cv. Kuali due to its heighest total number of tillers. Yield analyses indicated that cv. Numbu had the highest grain yield and water-use efficiency under drought, followed by cv. Samurai2, while cv. Kuali had the lowest for both traits, an indication of drought vulnerability. The study emphasized the importance of selecting sorghum cultivars according to examined drought response traits and provides valuable insights for climate change adaptation.