Evaluation of bio-physiological and yield responses of stay green QTL introgression sorghum lines to post-flowering drought stress
Drought is the most drastic abiotic stress that limits crop production in sub-Sahara Africa. Sorghum (Sorghum bicolor (L.) Moench) is among the most climate resilient cereals of the future due to its tolerance to drought and heat. Thus, identification of tolerant genotypes and plant characteristics that contribute to drought adaptation is timely. The objective of this study was to evaluate the response of 12 genotypes, including seven Stay-green (Stg) QTL introgression sorghum lines and their two donor; and three recurrent parents, to induced post-flowering drought stress. The recurrent parents were varieties released for drought prone lowlands of the country, and the donor parents were lines known to have stay-green properties. The study was conducted at Werer, in the Great Rift-valley of Ethiopia, during the off-season of 2014 under well-watered and water limited conditions. Significant differences (P<0.05) were observed among genotypes under water deficit regimes, for all measured physiological, biochemical (proline content), yield and yield related traits. Three Stg QTL introgression lines showed better tolerance to drought than their recurrent parents, as reflected by yield and maintenance of green leaf area. Three Stg QTL introgression lines, Teshale/E36-1, Gambella/B35-5 and Meko/B35-12, gave the highest grain yield under post-flowering drought stress, and B35 and Teshale/B35 gave the poorest yield under similar conditions. Therefore, these improved lines bear potential for use as alternatives in breeding programmes and for possible release in parts of the country where post-flowering drought stress is frequent. Proline content, weight of hundred seeds (HSW) and CO2 assimilation are effective screening tools for Stg property due to their high correlation with other parameters.
Key words: Post-flowering, proline, Sorghum bicolor