Agronomic performance of common bean genotypes under water stress

The common bean (Phaseolus vulgaris L.) is a major global staple crop essential for food security and the agricultural economy. However, its productivity has been compromised by climate change, particularly due to the intensification of drought events in agroecosystems, making drought stress one of the main factors limiting crop production. In this context, identifying drought-tolerant genotypes is crucial for developing resilient cultivars in breeding programs. This study aimed to agronomically characterize common bean genotypes under drought stress conditions and identify promising genotypes with superior performance under drought stress. A total of 38 genotypes — including F_2:6 recombinant inbred lines (RILs) derived from the cross between the carioca cultivars IAPAR 81 (drought tolerant) and LP97-28 (susceptible to drought) — were evaluated in two trials, in the randomized complete block design with three replicates under two water regimes: non-stressed (NS) and drought-stressed (DS). Until flowering, plants were maintained near field capacity. From the R5 phenological stage onwards, irrigation was suspended for ten days under DS condition, while plants under the NS condition remained irrigated throughout the entire crop cycle. Plant height (PH), number of days to flowering (NDF), number of days to maturity (NDM), number of pods per plant (NP), and grain yield (GY) were evaluated. Data were subjected to exploratory principal component analysis (PCA) and paired Student's t-tests to compare traits across water regimes.  The first two principal components explained 81.7% of the total variation and revealed clear discrimination among genotypes under contrasting water conditions, highlighting RILs 27, 29, and 344 as promising materials. In general, these specific genotypes maintained greater stability across agronomic traits despite water stress. Comparing all genotypes across the two water regimes revealed that drought stress significantly affected all traits (p-value < 0.01), delaying flowering by 0.42 days while reducing days to maturity by 2.96 days, pods per plant by 3.82, plant height by 4.79 cm, and grain yield by 127 kg ha^-1. In conclusion, these results demonstrate that drought stress negatively affects the agronomic performance of common bean. While the evaluated RILs exhibited contrasting responses to water limitation, RILs 27, 29, and 344 emerged as promising candidates for drought tolerance breeding programs.