Recurrent selection to obtain drought-tolerant common bean progenies
ABSTRACT. Common bean yield is directly related to climate conditions, and water deficit is one of the main limiting factors. One way of getting around this problem is increasing the frequency of alleles favorable to drought tolerance by the recurrent selection method. We estimated the morphophysiological and agronomic gains achieved in two recurrent selection cycles for drought tolerance and evaluated the genetic potential of the progenies obtained in each cycle. The first recurrent selection cycle was obtained by intercrossing 10 genotypes. This cycle was followed by physiological, morphophysiological, and agronomic evaluations, resulting in selection of 17 progenies. The second cycle was obtained by intercrossing the 17 selected progenies, followed by the same evaluations, resulting in 20 selected progenies. A randomized block experimental design was used for both selection cycles, with split plots and three replications. The plots consisted of two water treatments (irrigated and water deficit), and the subplots consisted of the progenies under evaluation. To select the progenies and estimate the genetic parameters, only the treatment under water deficit was considered, in randomized blocks with three replications. Irrigation was suspended at the R5 stage. Under these conditions, the following traits were evaluated: stomatal conductance, leaf temperature, relative chlorophyll index, leaf area, leaf dry matter, and shoot dry matter. After that, irrigation was reestablished and the following determinations were made: plant height, number of pods per plant, number of seeds per plant, number of seeds per pod, 100-seed weight, and grain yield. Recurrent selection was effective for selection of drought-tolerant plants, with gain from selection for grain yield of 231.94 kg ha-1 in the first cycle and 387.71 kg ha-1 in the second. Three progenies in the first selection cycle and 19 in the second selection cycle were identified as having better performance under water deficit conditions, which allowed drought-tolerant progenies to be chosen for use in breeding programs.