Drought Resistance In Common Bean Research Articles

Genome-wide association study dissecting drought resistance-associated loci based on physiological traits in common bean

Genetic improvement of drought resistance is one of the main breeding goals for common bean, so molecular markers must be identified to facilitate drought resistance breeding. In this study, we evaluated the proline, trehalose, raffinose, and stachyose contents of 210 common bean accessions under two watering conditions and found large variations in all four. The coefficients of variation ranged from 21.21% for proline content to 78.69% for stachyose content under well-watered conditions, and from 20.11% for proline content to 50.08% for trehalose content under drought stress. According to our genome-wide association analysis, 32 quantitative trait loci were associated with drought resistance, seven of which overlapped with known loci. Four hotspot regions were identified at Pv01, Pv07 and Pv11. A set of candidate genes was identified, including genes encoding MYB, bZIP, bHLH, ERF, and protein kinases. Among these genes, Phvul.001G189400, Phvul.007G273000 and Phvul.008G270500 were annotated as bZIP, ERF and WRKY, respectively. These genes are reportedly involved in drought stress responses in Arabidopsis thaliana and were induced by drought stress in common bean. Significant SNPs in six candidate gene regions formed different haplotypes, and phenotypic analysis revealed significant differences among the haplotypes. These results provide new insight into the genetic basis of drought resistance in common bean and reveal candidate genes and superior natural variations that will be useful for improving common bean.

Transcriptomic and metabolomic analysis reveals that symbiotic nitrogen fixation enhances drought resistance in common bean.

Common bean (Phaseolus vulgaris L.), one of the most important legume crops, use atmospheric nitrogen through symbiosis with soil rhizobia reducing the nitrogen fertilization needs. However, this legume is particularly sensitive to drought conditions, prevalent in arid regions where this crop is cultured. Therefore, studying the response to drought is important to sustain crop productivity. We have used integrated transcriptomic and metabolomic analysis to understand the molecular responses to water deficit in a marker-class common bean accession cultivated under N2-fixation or fertilized with nitrate (NO3-). RNA-seq revealed more transcriptional changes in the plants fertilized with NO3- than in the N2-fixing plants. However, changes in N2-fixing plants were more associated with drought tolerance than in the NO3- fertilized ones. N2-fixing plants accumulated more ureides in response to drought and GC/MS and LC/MS analysis of primary and secondary metabolites profiles revealed that N2-fixing plants also had higher levels of ABA, proline, raffinose, amino acids, sphingolipids and triacylglycerols than the NO3- fertilized ones. Moreover, plants grown under nitrogen fixation recovered from drought better than plants fertilized with NO3-. Altogether we show that common bean plants grown under symbiotic nitrogen fixation were more protected against drought than the plants fertilized with nitrate.

The aquaporin gene PvXIP1;2 conferring drought resistance identified by GWAS at seedling stage in common bean.

A whole-genome resequencing-derived SNP dataset used for genome-wide association analysis revealed 12 loci significantly associated with drought stress based on survival rate after drought stress at seedling stage. We further confirmed the drought-related function of an aquaporin gene (PvXIP1;2) located at Locus_10. A variety of adverse conditions, including drought stress, severely affect common bean production. Molecular breeding for drought resistance has been proposed as an effective and practical way to improve the drought resistance of common bean. A genome-wide association analysis was conducted to identify drought-related loci based on survival rates at the seedling stage using a natural population consisting of 400 common bean accessions and 3,832,340 SNPs. The coefficient of variation ranged from 40.90 to 56.22% for survival rates in three independent experiments. A total of 12 associated loci containing 89 significant SNPs were identified for survival rates at the seedling stage. Four loci overlapped in the region of the QTLs reported to be associated with drought resistance. According to the expression profiles, gene annotations and references of the functions of homologous genes in Arabidopsis, 39 genes were considered potential candidate genes selected from 199 genes annotated within all associated loci. A stable locus (Locus_10) was identified on chromosome 11, which contained LEA, aquaporin, and proline-rich protein genes. We further confirmed the drought-related function of an aquaporin (PvXIP1;2) located at Locus_10 by expression pattern analysis, phenotypic analysis of PvXIP1;2-overexpressing Arabidopsis and Agrobacterium rhizogenes-mediated hairy root transformation systems, indicating that the association results can facilitate the efficient identification of genes related to drought resistance. These loci and their candidate genes provide a foundation for crop improvement via breeding for drought resistance in common bean.

Root traits and their potential links to plant ideotypes to improve drought resistance in common bean

Drought stress limits growth and yield of crops, particularly under smallholder production systems with minimal use of inputs and edaphic limitations such as nitrogen (N) deficiency. The development of genotypes adapted to these conditions through genetic improvement is an important strategy to address this limitation. The identification of morpho-physiological traits associated with drought resistance contributes to increasing the efficiency of breeding programs. A set of 36 bean genotypes belonging to the Middle American gene pool was evaluated. A greenhouse study using soil cylinders was conducted to determine root vigor traits (total root length and fine root production) under drought stress. Two field trials were conducted to determinate grain yield, symbiotic nitrogen fixation (SNF) ability and other shoot traits under drought stress. Field data on grain yield and other shoot traits measured under drought were related with the greenhouse data on root traits under drought conditions to test the relationships between shoot traits and root traits. Response of root vigor to drought stress appeared to be related with ideotypes of water use (water savers and water spenders). The water spender ideotypes presented deeper root system, while the water saver ideotypes showed a relatively shallower root system. Increase in SNF ability under drought stress was associated with greater values of mean root diameter while greater acquisition of N from soil was associated with finer root system. We identified seven common bean lines (SEA 15, NCB 280, SCR 16, SMC 141, BFS 29, BFS 67 and SER 119) that showed greater root vigor under drought stress in the greenhouse and higher values of grain yield under drought stress in the field. These lines could serve as parents for improving drought resistance in common bean.

Shoot and Root Traits Contribute to Drought Resistance in Recombinant Inbred Lines of MD 23-24 × SEA 5 of Common Bean.

Drought is the major abiotic stress factor limiting yield of common bean (Phaseolus vulgaris L.) in smallholder systems in Latin America and eastern and southern Africa; where it is a main source of protein in the daily diet. Identification of shoot and root traits associated with drought resistance contributes to improving the process of designing bean genotypes adapted to drought. Field and greenhouse studies were conducted at the International Center for Tropical Agriculture (CIAT), Palmira, Colombia to determine the relationship between grain yield and different shoot and root traits using a recombinant inbred lines (RILs) population (MD23–24 × SEA 5) of common bean. The main objectives of this study were to identify: (i) specific shoot and root morpho-physiological traits that contribute to improved resistance to drought and that could be useful as selection criteria in breeding beans for drought resistance; and (ii) superior genotypes with desirable shoot and root traits that could serve as parents in breeding programs that are aimed at improving drought resistance. A set of 121 bean genotypes (111 RILs, 2 parents, 8 checks) belonging to the Mesoamerican gene pool and one cowpea variety were evaluated under field conditions with two levels of water supply (irrigated and rainfed) over three seasons. To complement field studies, a greenhouse study was conducted using plastic cylinders with soil inserted into PVC pipes, to determine the relationship between grain yield obtained under field conditions with different root traits measured under greenhouse conditions. Resistance to drought stress was positively associated with a deeper and vigorous root system, better shoot growth, and superior mobilization of photosynthates to pod and seed production. The drought resistant lines differed in their root characteristics, some of them with a vigorous and deeper root system while others with a moderate to shallow root system. Among the shoot traits measured, pod harvest index, and seed number per area could serve as useful selection criteria for assessing sink strength and for genetic improvement of drought resistance in common bean.

Effective Use of Water and Increased Dry Matter Partitioned to Grain Contribute to Yield of Common Bean Improved for Drought Resistance.

Common bean (Phaseolus vulgaris L.) is the most important food legume in the diet of poor people in the tropics. Drought causes severe yield loss in this crop. Identification of traits associated with drought resistance contributes to improving the process of generating bean genotypes adapted to these conditions. Field studies were conducted at the International Center for Tropical Agriculture (CIAT), Palmira, Colombia, to determine the relationship between grain yield and different parameters such as effective use of water (EUW), canopy biomass, and dry partitioning indices (pod partitioning index, harvest index, and pod harvest index) in elite lines selected for drought resistance over the past decade. Carbon isotope discrimination (CID) was used for estimation of water use efficiency (WUE). The main objectives were: (i) to identify specific morpho-physiological traits that contribute to improved resistance to drought in lines developed over several cycles of breeding and that could be useful as selection criteria in breeding; and (ii) to identify genotypes with desirable traits that could serve as parents in the corresponding breeding programs. A set of 36 bean genotypes belonging to the Middle American gene pool were evaluated under field conditions with two levels of water supply (irrigated and drought) over two seasons. Eight bean lines (NCB 280, NCB 226, SEN 56, SCR 2, SCR 16, SMC 141, RCB 593, and BFS 67) were identified as resistant to drought stress. Resistance to terminal drought stress was positively associated with EUW combined with increased dry matter partitioned to pod and seed production and negatively associated with days to flowering and days to physiological maturity. Differences in genotypic response were observed between grain CID and grain yield under irrigated and drought stress. Based on phenotypic differences in CID, leaf stomatal conductance, canopy biomass, and grain yield under drought stress, the lines tested were classified into two groups, water savers and water spenders. Pod harvest index could be a useful selection criterion in breeding programs to select for drought resistance in common bean.

Physiological traits associated with drought resistance in Andean and Mesoamerican genotypes of common bean (Phaseolus vulgaris L.)

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 and rainout shelter studies were conducted at the International Center for Tropical Agriculture (CIAT), Palmira, Colombia to (i) evaluate phenotypic differences in drought resistance in Andean and Mesoamerican gene pools, (ii) identify genotypes of both Andean and Mesoamerican with superior drought resistance, and (iii) identify phenotypic traits that may be useful for breeding to improve drought resistance in common bean. A total of 24 bean genotypes, twelve genotypes belonging to Mesoamerican gene pool and twelve to Andean gene pool were evaluated under field with two levels of water supply (irrigated and rainfed) and managed drought under rainout shelter conditions. Results showed that five Mesoamerican lines SEA 5, SEA 15, SER 22, SER 16, SER 8 and one Andean line SEQ 1003 have superior resistance to drought. The superior performance of these lines under drought stress was associated with better canopy biomass at mid-pod filling that could be related to deeper root system and effective use of water, combined with efficient remobilization of photosynthates from vegetative structures to pod development (pod partitioning index, PPI) and grain filling (pod harvest index, PHI). Pod harvest index could be a useful selection criteria for drought resistance, to improve the efficiency of breeding programs for selecting superior genotypes of common bean.

Improving adaptation to drought stress in small red common bean: phenotypic differences and predicted genotypic effects on grain yield, yield components and harvest index

Common bean (Phaseolus vulagaris L.) is mainly produced in Latin America, and Eastern and Southern Africa where seasonal rainfall is erratic and soil moisture deficit often limits its production. The objectives of this study were to identify superior advanced small red common bean lines with better grain yield under drought, and to identify plant traits that could serve as selection criteria for evaluating drought resistance. Thirty four advanced inbred lines were developed through triple cross and evaluated with two commercial checks (Nasir and Red Wolayita) under drought and irrigated field conditions in two seasons (2009 and 2010) and at two locations (Melkassa and Doni Kumbi Farm) in Ethiopia. Grain yield, pods/plant, seeds/plant and 100 seed weight were reduced by 47, 19, 15, and 9 %, respectively, under the drought conditions compared to the irrigated conditions. Seven genotypes (L62, L5, L20, L79, L12, L41, and L83) had better yield under drought compared to the standard check. Similarly, these genotypes had better predicted genotypic effects, suggesting that they would also be useful as drought resistant donors in common bean cultivar development program. Genotypic variance expressed as proportions to phenotypic variance was higher compared to genotype × environment interaction effects for all traits under drought conditions, suggesting that these genotypes can be used to further improve drought-resistance regardless of environments. Strong correlation between grain yield, canopy biomass and harvest index across environments suggested that canopy biomass and harvest index are repeatable and reliable plant traits to determine drought resistance in common bean.

Physiological Characteristics of Drought Resistance in Common Bean ( Phaseolus vulgaris L.)

Physiological Characteristics of Drought Resistance in Common Bean ( <i>Phaseolus vulgaris</i> L.)

English

Information on the availability of genetic variability and mode of gene action are critically important for choosing effective breeding methods that result in appreciable improvement in performance under drought stress. The objectives of this study were to estimate the gene action for drought resistance of quantitative traits and also to estimate the components of variance and heritability of drought resistance in common bean. Field experiment was carried out using six generations of two populations made of crosses between pairs of drought resistant and susceptible genotypes (Roba-1 &times; SER-16; Melka-Dima &times; SAB623). The treatments were laid in a split plot design with three replications, where watering regime was assigned to the main plot and generations to the sub-plot. Drought stress was initiated at flowering stage by withholding application of irrigation water. Scaling test and generation mean analysis brought out that individual crosses greatly differed for the gene action and on an overall basis all the types of gene action, additive, dominance and epistasis were important for drought resistance in common bean. Both additive and non-additive types of gene action were important in governing the inheritance of the traits considered. However, additive types of gene actions were important in the inheritance of number of pod per plant in Roba-1 &times; SER-16 and above ground biomass in Melka-Dima &times; SAB-623 under drought stress. Medium to high broad and narrow sense heritability were found for most of the traits under both watering regimes. Evidences have unfolded that chances to find stress tolerant breeding material in segregating populations of the two crosses were promising. The presence of significant amount of all types of gene action for the important traits imply that methods which can utilize all of them such as recurrent selection and multiple cross could be employed in breeding beans for drought environments. &nbsp; Key words:&nbsp;Common bean, drought resistance, gene action, generation mean analysis, heritability, scale test.

Relationship between carbohydrate partitioning and drought resistance in common bean

Drought is a major yield constraint in common bean (Phaseolus vulgaris L.). Pulse-chase (14)C-labelling experiments were performed using Pinto Villa (drought resistant) and Canario 60 (drought sensitive) cultivars, grown under optimal irrigation and water-deficit conditions. Starch and the radioactive label incorporated into starch were measured in leaves and pods at different time points, between the initiation of pod development and the production of mature pods. The water-stress treatment induced a higher starch accumulation in the drought-resistant cultivar pods than in those of the drought-sensitive cultivar. This effect was more noticeable during the early stages of pod development. Consistently, a reduction of starch content occurred in the leaves of the drought-resistant cultivar during the grain-filling stage. Furthermore, a synchronized accumulation of sucrose was observed in immature pods of this cultivar. These data indicate that carbohydrate partitioning is affected by drought in common bean, and that the modulation of this partitioning towards seed filling has been a successful strategy in the development of drought-resistant cultivars. In addition, our results suggest that, in the drought-resistant cultivar, the efficient carbon mobilization towards the seeds in response to water limitation is favoured by a mechanism that implies a more effective sucrose transport.

Breeding for Drought Resistance in Common Bean: In Vitro Assay for Root Osmotic Potential

ABSTRACT Initial and adjusted osmotic potentials of separate leaf- and root-derived calli were assessed in vitro for two teparies (Phaseolus acutifolius A. Czray) and a common bean (P. vulgaris L.) cultivar differing in physiological and morpho-physiological reactions of intact plants to water stress. Unstressed leaf- and root-derived calli of common bean (CB) had higher preexisting osmotic potential (ψs) and relative growth rate (RGR) but lower dry-matter percent (DM) than those of tepary bean (TB) lines when grown on basal Murashige and Skoog medium (–0.30 MPa). Exposure to water stress (−0.58 MPa) imposed by adding polyethylene glycol (10% [w/v], PEG-10,000) did not affect these parameters for leaf-derived callus of CB and both leaf- and root-derived calli of TB. However, root-derived callus of CB showed decreased ψs that was maintained after transferring stressed callus onto medium lacking PEG for recovery from water stress. Nevertheless, its RGR decreased and DM increased. Stressed plants of both CB and TB grown in the greenhouse manifested significant reduction in leaf, stem, and root dry mass and leaf area. However, the magnitude of mass reduction was especially high for CB stem, leaf, and root. While TB root system penetrated deeper in the soil profile, CB root depth did not significantly change in response to drought. In addition, substantial CB root mass was detected in the top 10 to 20 cm of the soil profile. Stomata conductance and transpiration rate were higher for CB than TB under both well-watered and water-stress conditions. Significant relative water content reduction was detected only in CB. In spite of water stress, soil moisture was high around roots of CB compared with TB, suggesting lesser efficiency of CB root system to extract water. Stressed CB grown in the production field did not produce seed yield whereas TB gave 60 to 64% of its potential dry seed yield. In vitro assay for root osmotic potential should be useful in improving drought resistance in common bean.

Selection for Drought Resistance in Common Bean Also Improves Yield in Phosphorus Limited and Favorable Environments

An estimated 60% of common bean (Phaseolus vulgaris L.) production worldwide is at risk of drought. A breeding program was developed at the International Center of Tropical Agriculture (CIAT) to create drought resistant breeding lines with varietal potential in the small red, small black, cream (mulatinho) and cream‐striped (carioca) grain classes. Breeding populations were created from triple or double crosses. Field screening under terminal drought was performed at Palmira, Colombia in the dry season in F2, F3:5, and F6:8 generations over two cycles of recurrent selection in the small red and small black classes, and one cycle in the mulatinho and carioca classes. Drought resistant lines yielded significantly more than commercial check cultivars under drought in all color classes. Some outyielded the respective checks by 15 to 25% (depending on color class and trial) in one or more of three favorable environments, or in the combined analysis across favorable environments, and were also earlier to mature. Drought resistant lines presented up to 36% greater yield d−1 in favorable environments. Some also expressed superior yields in a phosphorus‐limited environment. Thus, selection for drought resistance has improved yield potential and plant efficiency across different environments. It is suggested that selection under drought stress reveals genes that correct inefficiencies inherited from the wild Phaseolus vulgaris, and are key to yield improvement of common bean.

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 F2-derived F4 (F2:4) 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 F5:7 lines from each of the four highest yielding F2:5 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 yieldof 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. Key words: Drought resistance in common bean, early generation yield test, F2-derived family selection, Phaseolus vulgaris, seed yield

Comparison of Sources and Lines Selected for Drought Resistance in Common Bean.

Drought is a major constraint to common bean (Phaseolus vulgaris L.) production worldwide. Our objectives were to (i) identify sources of drought resistant germplasm in common bean cultivars and (ii) compare drought resistant germplasm with lines selected from interracial and intergene pool populations. We included in this study 12 of the most promising drought resistant cultivars from race Durango and 11 from race Jalisco, nine drought resistant lines selected from interracial or intergene pool populations, and two drought resistant and two susceptible checks. The 36 genotypes were evaluated in drought-stressed (DS) and nonstressed (NS) environments in four cropping seasons between 1996 and 1998 at the International Center for Tropical Agriculture (CIAT), Palmira, Colombia. Drought stress reduced seed yield by 53%, 100-seed weight by 13%, and days to maturity by 3%. Race Durango cultivars had higher yield, larger seed weight, and earlier maturity than race Jalisco cultivars in DS and NS environments. Large variations within the two races were found for the three traits. Drought resistant selected lines out-yielded drought resistant checks by 44% in DS and 15% in NS and cultivars from race Durango by 48% in DS and 30% in NS and race Jalisco by 96% in DS and 46% in NS environments. Seed yield in DS was correlated negatively with the percent reduction (PR) because of drought stress and drought susceptibility index (DSI), whereas a positive correlation existed between PR and DSI. Drought resistant selected lines and race Durango cultivars had similar maturity. Mean 100-seed weight of selected lines (23 g) was less than race Durango (34 g) and race Jalisco cultivars (29 g). While new sources of drought resistance could be identified in races Durango and Jalisco, these drought resistant germplasm and selected lines derived from interracial and intergene pool populations should be utilized for improvement of drought resistance in common bean.

Comparison of Sources and Lines Selected for Drought Resistance in Common Bean

Comparison of Sources and Lines Selected for Drought Resistance in Common Bean

Traits related to drought resistance in common bean

Common bean (Phaseolus vulgaris L.) is grown in regions where water deficits during reproductive development significantly reduce yield. The purpose of this study was to evaluate the association of specific phenological and physiological traits with drought resistance in common bean. Five genotypes were grown under and near a rain shelter in 1988, and an additional 16 progeny lines were included in 1990. Drought stress determined by the drought intensity index was severe (0.78) in 1988 and more moderate (0.63) in 1990. Water stress reduced the expression of most traits with the exception of days to flower and leaf moisture retention capacity. Seed yield among genotypes was reduced from 22 to 71% due to drought. Yield under stress was correlated with yield under nonstress in 1990 and negatively correlated with the drought susceptibility index in 1988. Yield components which exhibited the largest differential genotypic responses to stress were pod and seed number, whereas seed size was more stable. Genotypic variation was detected in all the partitioning indexes, chiefly harvest index and relative sink strength, and the heritability estimates for these traits were high. The limited genetic variability observed among water relations traits and their role in water conservation would restrict their potential use in the selection for drought resistance in common bean. The differential correlations between phenological, biomass and partitioning traits and the indexes for yield and drought susceptibility would suggest that the most effective approach in breeding for drought resistance in common bean would be based first on selection for high geometric yield followed by selection among the high-yielding individuals for low to moderate levels of the drought susceptibility index.

Marker‐Assisted Selection to Improve Drought Resistance in Common Bean

Breeding for a quantitative trait like drought resistance would be facilitated by the development of a method of marker‐assisted selection (MAS) that is capable of identifying high performing genotypes in early generations. Two recombinant inbred populations were grown from 1990 to 1994 at eight locations in Michigan and Mexico under stress and nonstress conditions to identify random amplified polymorphic DNA (RAPD) markers associated with drought resistance in common bean (Phaseolus vulgaris L.) Six‐hundred random decamer primers were screened against the parents of the two populations, 50% of which were polymorphic. Seventy of these polymorphic primers were screened against each population. Using one‐way analysis of variance and multiple regression, four RAPD markers were identified in one population and five in another that were consistently and significantly associated with yield under stress, yield under nonstress, and/or geometric mean yield across a broad range of environments. To test the effectiveness of MAS for drought resistance, markers were used to select genotypes from either extreme. Yield data from three locations were examined to evaluate the effectiveness of these markerbased selections. Marker‐assisted selection in the Sierra/AC1028 population was found to be effective in Michigan under severe stress and ineffective in Mexico under moderate stress. The five RAPD markers used for MAS in the Sierra/Lef‐2RB population improved performance 11% under stress and 8% under nonstress, whereas conventional selection based on yield performance failed to increase performance. Response to conventional selection was three times greater in the Sierra/AC1028 population, supporting the conclusion that the effectiveness of MAS is inversely proportional to the heritability of the trait under examination.

Improving Common Bean Performance under Drought Stress

Drought is the second major constraint to common bean (Phaseolus vulgaris L) production after disease. This study examined yield under drought, yield potential, drought susceptibility index, harvest index, and geometric mean as potential indicators of drought resistant genotypes. The performance of two common bean populations, consisting of 78 and 95 recombinant inbred lines, was examined under moisture stress and nonstress regimes. Experiments were conducted at seven locations (1990–1994) in Michigan and Mexico to identify effective selection criteria for drought resistance. Two genotypes from each population yielded in the top 10% under both stress and nonstress conditions. Heritability estimates for yield in the Sierra/AC1028 population, based on 5 yr of data, ranged from 0.55 to 0.59 for stress and nonstress, respectively, and from 0.20 to 0.19 for stress and nonstress, respectively, in the Sierra/Lef‐2RB population. Heritability for plant biomass was 0.52 for stress and 0.55 for nonstress in the Sierra/AC1028 population and 0.15 under stress and 0.05 under nonstress in the Sierra/Lef‐2RB population. One‐hundred seed weight was the most highly heritable trait in both populations with heritability estimates of 0.80 for the Sierra/AC1028 population and 0.65 for the Sierra/Lef‐2RB population. The geometric mean of the two moisture regimes was the single strongest indicator of performance under stress and nonstress, and a breeding strategy that involves selection based first on the geometric mean, followed by selection based on yield under stress, was suggested as the most effective strategy to improve drought resistance in common bean.