Pre-and post-flowering drought resistance and recovery strategies of sorghum

Abstract

With ongoing climate change, characterized by increasing frequency and intensity of droughts, developing drought-adaptable crops has become a critical focus in recent decades. Sorghum, a key crop for addressing food and nutritional insecurity, is particularly vulnerable to both pre- and post-flowering drought under rain-fed farming systems. Effective screening and phenotyping techniques are essential for breeding drought-resilient sorghum varieties. This study aimed to generate knowledge for the selection of drought-adaptable sorghum genotypes for targeted use in drought resilience breeding. Specifically, it sought to (i) determine the response of sorghum genotypes to pre- and post-flowering drought stress and (ii) determine the response of selected genotypes to rewatering after drought. In the screen house, eighty sorghum genotypes from the national sorghum breeding program were assessed under different moisture regimes. The moisture regimes included: well-watered, pre-flowering drought and post-flowering drought, arranged as a split-plot design with watering regimes as whole plots, while sorghum genotypes as subplots, with three replications. Subsequently, a field trial arranged as a 10 x 8 alpha-lattice with three replications was established at Nabuin-ZaRDI-Karamoja to assess the effect of natural drought on the entire sorghum trial population. A subsequent screenhouse experiment assessed the drought recovery potential of sixteen selected genotypes and two checks, subjecting them to drought stress followed by rewatering. Results showed that pre-flowering drought was more detrimental, reducing yield by 98%, compared to a 76% yield reduction due to post-flowering drought. Key traits for pre-flowering drought resistance included higher chlorophyll content, larger green leaf area, reduced biomass yield and a higher survival ability. In contrast, plant height, low relative growth, reduced leaf inclination angle, flag leaf dimensions and genotype’s good agronomic robustness (plant vigour and agronomic score) were associated with post-flowering drought resistance. Leveraging drought selection indices and survival probabilities, genotypes were ranked by resistance. Genotypes ASARECA 13-1 x Framida -1-1-3-1/2022B, ICSX 162719-1-4-1-1-1, ICSX152666-B-2-7-3-1-1-1, SSGA/RAP/349 and IESV16 143-1-3-1 exhibited superior resistance to both pre- and post-flowering drought. Strong recovery abilities along with high breeding values were observed in genotypes ASARECA 13-1 x Framida -1-1-3-1/2022B, NAROSORGH1 x NAROSORGH3-1-1-5-1/2022B, ASARECA 13-1 x NAROSORGH3-1-1-1-1/2022B, GE16/2/20B x IESV92041SH (SSEA 18B#6) and NAROSORGH1 x NAROSORGH3 -1-1-1-1/2022B, whereas IESV 214006DL and ICSX152005-SB-5-3-2-1 were highly susceptible and showed the poorest recovery. Notably, genotypes ASARECA 13-1 x Framida -1-1-3-1/2022B, ASARECA 13-1 x NAROSORGH3-1-1-1-1/22B and ICSX152666-B-2-7-3-1-1-1 combined both strong resistance and robust recovery, making them promising parental lines for breeding drought-adaptable sorghum, while the most susceptible genotypes may serve as local negative checks.