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.La s\ue8cheresse est le stress abiotique le plus drastique qui limite la production agricole en Afrique Sub-saharienne. Le sorgho ( Sorghum bicolor (L.) Moench) est parmi les c\ue9r\ue9ales les plus r\ue9silientes au climat pour le futur d\ufb \ue0 sa tol\ue9rance \ue0 la s\ue9cheresse et \ue0 la chaleur. Donc, l\u2019identification des g\ue9notypes tol\ue9rants et les caract\ue9ristiques des plants qui contribuent \ue0 l\u2019adaptation \ue0 la s\ue9cheresse est opportune. L\u2019objectif de cette \ue9tude \ue9tait d\u2019\ue9valuer la r\ue9ponse de 12 g\ue9notypes, comportant sept lign\ue9es de sorgho conf\ue9rant l\u2019introgression des QTL des attributs verts (Stg), leurs deux donneurs\ua0; et les trois parents r\ue9currents, au stress de la s\ue9cheresse post floraison induite. Les parents r\ue9currents ont \ue9t\ue9 les vari\ue9t\ue9s lib\ue9r\ue9es sensibles \ue0 la s\ue9cheresse dans les plaines du pays, et les donneurs ont \ue9t\ue9 les lign\ue9es connues pour leurs propri\ue9t\ue9s relatives aux attributs verts. L\u2019\ue9tude a \ue9t\ue9 conduite \ue0 Werer, dans la grande vall\ue9e du Rift d\u2019Ethiopie, pendant la contre saison de 2014 dans des conditions d\u2019irrigation abondante et d\u2019irrigation limit\ue9e. De diff\ue9rences significatives (P<0.05) ont \ue9t\ue9 observ\ue9es entre les g\ue9notypes sous des r\ue9gimes de d\ue9ficit hydriques, pour tous les traits physiologiques, biochimiques (teneur en proline), le rendement et les composantes de rendement. Trois lign\ue9es d\u2019introgression de Stg QTL ont montr\ue9 de meilleure tol\ue9rance \ue0 la s\ue9cheresse que leurs parents r\ue9currents, comme refl\ue9t\ue9 par le rendement et la maintenance de la surface verte de la feuille. Trois lign\ue9es d\u2019introgression de Stg QTL, Teshale/E36-1, Gambella/B35-5 et Meko/B35-12, ont donn\ue9 le plus haut rendement sous le stress de s\ue9cheresse de post floraison, et B35 et Teshale/B35 ont donn\ue9 le plus faible rendement dans des conditions similaires. En cons\ue9quence, ces lign\ue9es am\ue9lior\ue9es d\ue9tiennent tout le potentiel pour leur usage comme alternatives dans des programmes d\u2019am\ue9lioration g\ue9n\ue9tiques et pour une lib\ue9ration possible dans les r\ue9gions du pays o\uf9 le stress de la s\ue9cheresse post floraison est fr\ue9quent. La teneur en proline, le poids de 100 graines (HSW) et l\u2019assimilation du CO2 sont des outils effectifs de criblage pour la propri\ue9t\ue9 de Stg due \ue0 leur forte corr\ue9lation avec les autres param\ue8tres