Selection for drought resistance in early generations of common bean populations

Availability and use of high-yielding drought-resistant common bean (Phaseolus vulgaris L.) cultivars would reduce dependence on irrigation water and production costs, stabilize yield in drought-prone environments, and potentially increase profit margins for growers. Among various selection criteria, seed yield has been found to be the most effective to improve drought resistance in common bean. Our objective was to determine the effectiveness of selection for seed yield in drought-stressed (DS) and non-stressed (NS) environments in early generations of common bean populations under field conditions. One hundred thirty-four F-2-derived F-4 (F-2:4) families from each of three double-cross populations (SX 12008, SX 12009, and SX 12010), four parents, and six checks were evaluated in replicated field trials in DS and NS environments at the Centro Internacional de Agricultura Tropical, Palmira, Colombia during the January to March growing season (1997A). The 30 highest yielding F2:5 families from each population and each environment, four parents, and two checks were again evaluated in replicated trials in their respective DS and NS environments during the June to August growing season (1997B). Three F-5:7 lines from each of the four highest yielding F,,, families from each population and each environment (a total of 72 lines), and nine parents involved in the three populations were evaluated in replicated trials in both DS and NS environments in 1998B and 1999B. Mean yield of lines selected in the NS environment was significantly higher than the mean of parents in populations SX 12008 and SX 12010 when tested in the NS environment. In population SX 12009, lines selected in the DS environment had higher mean yield than their parents when tested in NS environment. The mean yields of lines selected in the DS and NS environments did not differ significantly when tested in the DS environment in any population. NS environment seed yields were positively correlated with DS yields, geometric mean yield (GM), percent reduction (PR) due to drought stress, and drought susceptibility index (DSI). In contrast, DS and GM yields were negatively correlated with PR and DSI, whereas the association between the latter two was positive. The 100-seed weight was slightly reduced and mean maturity was accelerated by 2 to 4 d in DS versus NS environments. Considering the extra costs involved to test early generation selections for seed yield in DS environments, it does not appear to be advisable in common bean.