CAN TEPARY BEAN BE A MODEL FOR IMPROVEMENT OF DROUGHT RESISTANCE IN COMMON BEAN?

Common bean ( Phaseolus vulgaris L.) is the most important grain legume for human consumption and drought stress affects over 60% of dry bean production worldwide. Field studies were conducted over two seasons at Centro Internacional de Agricultura Tropical (CIAT), Palmira, Colombia to (i) evaluate phenotypic differences in drought resistance; and (ii) identify adaptive traits that can be used in on-going breeding programmes of common bean for developing drought resistant genotypes. A total of 36 genotypes, including elite inbred and interspecific lines and landraces of common bean and tepary bean were evaluated under field conditions with two levels of water supply (irrigated and rainfed). Results showed that two accessions of tepary bean, P. acutifolius (G 40159 and G 40068) and two elite lines (RAB 650, SEA 23) of common bean were outstanding in their adaptation to terminal drought stress. The superior performance of these genotypes under drought stress was associated with their ability to mobilise photosynthates from leaves and stems to developing grain. Tepary bean was superior to common bean in combinig several desirable traits that contribute to greater level of adaptation to terminal drought stress. Canopy biomass, pod partitioning index, stem biomass reduction and pod harvest index could serve as useful traits to improve the efficiency of breeding programmes to select superior genotypes of common bean under terminal drought stress.Le haricot common ( Phaseolus vulgaris L.) est une l\ue9gumineuse la plus importante pour la consummation humaine don\u2019t la s\ue9cheresse affecte plus de 60% de bean production mondiale. Des \ue9tudes en champs \ue9taient conduits en deux saisons au Centro Internacional de Agricultura Tropical (CIAT), Palmira, Colombia afin de (i) \ue9valuer les diff\ue9rences ph\ue9notypiques pour la r\ue9sistance \ue0 la s\ue9cheresse; et (ii) identifier les traits adaptifs pouvant \ueatre utilis\ue9s dans les programmes en cours d\u2019am\ue9lioration du haricot commun pour le d\ue9veloppement des g\ue9notypes resistant \ue0 la s\ue9cheresse. Trente six g\ue9notypes incluant des hybroides \ue9lites et interseptiques ainsi que des haricot de races locales et haricot tepary \ue9taient \ue9valu\ue9s au champs avec deux niveaux d\u2019approvisionnement en eau (irrigation et pluvial). Les r\ue9sultats ont montr\ue9 que deux accessions du haricot tepary, P. acutifolius (G 40159 et G 40068) et deux lign\ue9es \ue9lites (RAB 650, SEA 23) de haricot commun s\u2019\ue9taient distingu\ue9es de par leur adaptation au stress hydrique. La performance sup\ue9rieur de ces g\ue9notypes sous stress hydrique \ue9tait associ\ue9e avec leur capacit\ue9 de mobiliser les photosyntates des feuilles et tiges pour le d\ue9veloppement de grains. Le haricot tepary \ue9tait sup\ue9rieur au haricot commun en terme de combinainson de plusieurs taits d\ue9sirables qui contribuent au niveau plus \ue9lev\ue9 d\u2019adaptation au stress hydrique. La biomasse de canop\ue9e, l\u2019indice de la repartition des gousses, la r\ue9duction de la biomasse des tiges et l\u2019indice de r\ue9colte de gousses pourrainet servir comme des traits utiles pour am\ue9liorer l\u2019efficacit\ue9 des programmes d\u2019am\ue9lioration pour pour s\ue9lectionner les g\ue9notypes sup\ue9rieurs de haricot commun sous stress hydrique