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Accueil du site → Doctorat → Chine → 2019 → Agronomic and Physiological Mechanisms of Water Deficit Tolerance in Cowpea in Condition of Symbiotic Relation with Rhizobia

China Academy of Agricultural Sciences Resource and Agricultural Quhua Academe (2019)

Agronomic and Physiological Mechanisms of Water Deficit Tolerance in Cowpea in Condition of Symbiotic Relation with Rhizobia

Tankari Moussa

Titre : Agronomic and Physiological Mechanisms of Water Deficit Tolerance in Cowpea in Condition of Symbiotic Relation with Rhizobia

Auteur : Tankari Moussa;

Grade : Doctoral Dissertation 2019

Université : China Academy of Agricultural Sciences Resource and Agricultural Quhua Academe

Résumé
The increase in global climatic change coupled with drought stress incidence and events expose plants to multiple abiotic stresses at different stages of their growth which can result in higher risk of yield damage.In legumes such as cowpea,drought stress affects not only their growth but also the efficacy of their symbiosis with rhizobia.The impact of soil water regimes on physiological responses and water use efficiency(WUE)for cowpea inoculated with rhizobia still remains implicit.The legacy of drought priming stress against the later drought stress has been well reported in many crops species.However,this was not confirmed yet in cowpea,and the impact of drought priming on subsequent different soil water status remains unclear.Therefore,understanding the mechanisms of drought tolerance in cowpea is a great of importance to maintain or sustain grain yield and productivity.The objectives of this study were :(i)to investigate the effect of water stress and rhizobia inoculation on leaf gas exchange,plant water relation,water use efficiency as well as carbon and oxygen isotope compositions(δ13C,δ18O),(ii)to determine the effect of drought priming during the early growth stage of cowpea on physiological responses,drought signaling and WUE in response to subsequent drought stress during the later growth stage.Pot experiments were carried out in 2017 and 2018 in a temperature-controlled glasshouse at Chinese Academy of Agricultural Sciences(CAAS),Beijing,China.In order to investigate the effect of water stress and rhizobia inoculation on leaf gas exchange,plant water relation,water use efficiency as well as carbon and oxygen isotope compositions(δ13C,δ18O),cowpea was inoculated with rhizobia under three different soil water levels.The treatments included soil water regimes at three levels(90%,70%,and 50%of soil water holding capacity(SWHC))and two inoculation forms(inoculated and non-inoculated with rhizobia).The results showed that across the inoculation treatments,reduced soil water regimes depressed both stomatal conductance(gs)and photosynthesis(An)of the leaves,nonetheless,the decrease of gs was more pronounced compared with the reduction in An.Consequently,the intrinsic water use efficiency(WUEi)was improved in the treatments under decreased soil water conditions.Plant WUE was also improved when soil water contents decreased as exemplified by the increased leafδ13C andδ18O,indicating the enhanced plant WUE was mainly attributed to the decrease of gs.Significant interactions between soil water regimes and rhizobia treatments for root water potential(RWP),leaf water potential(LWP),and gs were found due to the different responses of rhizobia to varied soil water regimes.Inoculation could improve plant water status and gs under 70%and 90%SWHC compared to 50%SWHC with negative effect from rhizobia.A moderate soil water regime is suggested for cowpea production in terms of high WUE with a minor biomass reduction.Further,before the application of rhizobium strains in the field,investigations should be made to examine the inoculation efficiency of rhizobium strains and their relations with soil environments for specific crops.To examine the effect of drought priming during the early growth stage of cowpea on physiological responses and WUE in response to subsequent drought stress during the later growth stage,two cowpeas varieties with contrasting responses to drought stress(sensitive and tolerant)were used.Plants were submitted to drought priming by withholding water for 12 days followed by water recovery and then subjected to subsequent drought stress(80%,60%and 40%SWHC).

Mots clés : Plant hormone; δ13C; δ18O; rhizobium inoculation; photosynthesis; stomata; water potential; drought priming;

Présentation (CNKI)

Page publiée le 14 octobre 2020, mise à jour le 25 novembre 2021