An adaptation breeding strategy for water deficit in bean developed with the application of the DSSAT3 drybean model

Bean (Phaseolus vulgaris L.) productivity is much constrained by water deficits in many production areas in eastern and southern Africa. The DSSAT 3 Drybean model was used to analyze the effects of water deficits on bean using genetic coefficients of four cultivars including an early, determinate type and early, intermediate and late maturity indeterminate bush types. More than 2300 simulations were run using meteorological data from 19 locations. The late maturing ideotype gave highest yield in less stressful environments but its yield was the least stable. In more stressful environments, early maturing ideotypes had highest mean yield and their yield was most stable in all environments. Stress was most severe and frequent in the later stages of growth; stress affected yield most during pod formation and fill, less during the early reproductive stage and least during the vegetative stage. Elements of a possible strategy for improving adaptation to water deficits are discussed, and specific information for the application of such a strategy is given for three locations which appear suitable as primary screening sites.La productivit\ue9 du haricot (Phaseolus vulgaris L.)est bien contrainte par les d\ue9ficits hydriques dans beaucoup d'aires de production en Afrique de l'est et du sud. Le DSSAT3 drybean model a \ue9t\ue9 utilis\ue9 pour analyser les effets de d\ue9ficits hydriques sur le haricot en utilisant les coefficients g\ue9n\ue9tiques de quatre cultivars comprenant les types pr\ue9coces d\ue9termin\ue9s et les types nains indetermin\ue9s \ue0 maturit\ue9 interm\ue9diaire et tardive. Plus de 2300 simulations \ue9taient perform\ue9es en utilisant les donn\ue9es m\ue9t\ue9orologiques de 13 stations \ue9cologiques. L'idiotype \ue0 maturit\ue9 tardive a donn\ue9 le plus haut rendement dans les environnements moins stressants mais son rendement a \ue9t\ue9 le moins stable. Dans les environnements plus stressants, les idiotypes \ue0 maturit\ue9 pr\ue9coce ont eu le plus haut rendement et leur rendement a \ue9t\ue9 le plus stable dans tous les environnements. Le stress \ue9tait plus s\ue9v\ue8re et fr\ue9quent dans les derniers stades de croissance et a affect\ue9 plus le rendement pendant la p\ue9riode de formation et de remplissage des gousses; il \ue9tait moins durant le stade pr\ue9coce de reproduction et moins plus durant le stade v\ue9g\ue9tatif. Les \ue9l\ue9ments d'une strat\ue9gie possible pour am\ue9liorer l'adaptation aux d\ue9ficits hydriques sont analys\ue9s et l'information sp\ue9cifique pour l'application d'une telle strat\ue9gie est donn\ue9e pour trois stations \ue9cologiques qui apparaissent convenables comme sites primaires pour le criblage