Carlos A. Urrea

Drought significantly constrains common bean (Phaseolus vulgaris L.) production worldwide, and as climate change intensifies, projections indicate a subsequent reduction in yield. This study aimed to identify drought-resilient genotypes among twenty common bean lines in Chile under two water regimes: regular irrigation and terminal drought stress. The research was conducted over two seasons in south-central Chile. Drought significantly reduced grain yield (22.7%), aboveground biomass (37%), harvest index (19.5%), the number of grains per pod (61.3%), and hundred-grain weight (10.1%). Genotypes 452, 473, and 483 exhibited minimal yield reductions (<11%) and maintained stable physiological performance, including higher quantum yield of photosystem II and efficient photoprotective mechanisms (increased ΦNPQ) under stress. In contrast, sensitive genotypes like Blanco Español showed marked yield loss (54%) and lower photosynthetic efficiency. Chlorophyll retention emerged as a key trait for identifying high-yielding, drought-tolerant genotypes. Drought also accelerated crop maturation in susceptible genotypes, compromising yield potential. These findings highlight the importance of integrating agronomic, phenological, and physiological traits in breeding programs to develop drought-adapted varieties. The tolerant genotypes offer valuable genetic traits to improve drought resilience and contribute to food security in the face of climate change.

Abiotic constraints, such as drought and heat driven by climate change, negatively impact the production of the common bean (Phaseolus vulgaris L.), an essential grain legume worldwide. The ability to tolerate drought and heat stress in common bean can be improved by introducing genetic variation from related species, such as tepary bean (Phaseolus acutifolius A. Gray), which has recently gained attention because of its adaptation to drought and heat stresses and potential use as a genetic resource and alternative crop. To better understand the phenotypic response of tepary bean to drought and heat stress in multiple environments and trials and to select highly adapted tepary beans, we conducted two field experiments. In Experiment 1, we compared the adaptation to drought stress of tepary bean (n = 10), common bean (n = 10), and Lima bean (Phaseolus lunatus L.; n = 9) by assessing the reduction in grain yield under terminal drought compared to well‐irrigated conditions in two California locations with arid summer conditions. Of the three species, tepary bean showed the statistically strongest adaptation to terminal drought, followed by Lima bean and common bean. In Experiment 2, we evaluated a set of 22 tepary beans from contrasting origins for drought and heat stresses across multi‐environment trials (METs) in California, Nebraska, and Colombia, with common bean as a control. We found a considerable variation in the tepary bean phenotypic response to these MET conditions, as a result of a strong genotype × environment interaction. Also, we identified tepary bean accessions adapted to drought, heat, and well‐irrigated conditions across multiple climate zones. Understanding the performance of tepary bean across multiple environments and identifying tepary beans with broad and target‐specific adaptation will maximize the potential use of the species.

‘Kikatiti’ pinto bean (Phaseolus vulgaris L.) (Reg. no. CV‐361, PI 705149) was developed by the dry bean breeding program at the University of Nebraska, Agricultural Research Division, and submitted for release in 2021 by the Sokoine University of Agriculture in Morogoro as an upright indeterminate pinto bean with high yield potential and multiple disease resistance across bean production environments in Tanzania. Kikatiti was officially released in 2024 by the National Seed Committee. Kikatiti is an F_7:8 derived line developed using the pedigree breeding method in Nebraska. The exceptional performance of Kikatiti in Tanzania was first identified by evaluation of the Durango Diversity Panel (DDP), which consisted of 200 accessions in on‐station trials conducted in Arusha and Mbeya. Kikatiti was identified as accession DDP‐094 (advanced breeding line NE2‐09‐3). Kikatiti yielded 1584 kg ha⁻¹ across 5 years of trials in Tanzania and matured in 89 days. Kikatiti is resistant to bean rust conferred by the Ur‐3 and Ur‐11 genes, resistant to all strains of Bean common mosaic virus and Bean common mosaic necrosis virus conferred by the I and bc‐3 genes, moderately resistant to common bacterial blight conferred by the SAP6 quantitative trait locus, avoids white mold disease due to its upright architecture, and is moderately susceptible to angular leaf spot disease. Kikatiti has large seed size (35.9 g 100 seeds⁻¹), and in on‐farm trials, farmers ranked Kikatiti above local pinto cultivars for its performance and market potential. Kikatiti has the potential to expand pinto bean production across East Africa.

This study identified proteomic changes in the seeds of two tolerant (SB-DT3 and SB-DT2) and two sensitive (Merlot and Stampede) common bean genotypes in response to terminal drought stress. Differentially expressed proteins (DEPs) were abundant in the susceptible genotype compared to the tolerant line. DEPs associated with starch biosynthesis, protein–chromophore linkage, and photosynthesis were identified in both genotypes, while a few DEPs and enriched biological pathways exhibited genotype-specific differences. The tolerant genotypes uniquely showed DEPs related to sugar metabolism and plant signaling, while the sensitive genotypes displayed more DEPs involved in plant–pathogen interaction, proteasome function, and carbohydrate metabolism. DEPs linked with chaperone and signal transduction were significantly altered between both genotypes. In summary, our proteomic analysis revealed both conserved and genotype-specific DEPs that could be used as targets in selective breeding and developing drought-tolerant common bean genotypes.

We conducted a genome-wide transcriptomic analysis of three drought tolerant and sensitive genotypes of common bean to examine their transcriptional responses to terminal drought stress. We then conducted pairwise comparisons between the root and leaf transcriptomes from the resulting tissue based on combined transcriptomic data from the tolerant and sensitive genotypes. Our transcriptomic data revealed that 491 (6.4%) DEGs (differentially expressed genes) were upregulated in tolerant genotypes, whereas they were downregulated in sensitive genotypes; likewise, 396 (5.1%) DEGs upregulated in sensitive genotypes were downregulated in tolerant genotypes. Several transcription factors, heat shock proteins, and chaperones were identified in the study. Several DEGs in drought DB (data Base) overlapped between genotypes. The GO (gene ontology) terms for biological processes showed upregulation of DEGs in tolerant genotypes for sulfate and drug transmembrane transport when compared to sensitive genotypes. A GO term for cellular components enriched with upregulated DEGs for the apoplast in tolerant genotypes. These results substantiated the temporal pattern of root growth (elongation and initiation of root growth), and ABA-mediated drought response in tolerant genotypes. KEGG (kyoto encyclopedia of genes and genomes) analysis revealed an upregulation of MAPK (mitogen activated protein kinase) signaling pathways and plant hormone signaling pathways in tolerant genotypes. As a result of this study, it will be possible to uncover the molecular mechanisms of drought tolerance in response to terminal drought stress in the field. Further, genome-wide transcriptomic analysis of both tolerant and sensitive genotypes will assist us in identifying potential genes that may contribute to improving drought tolerance in the common bean.

Many environmental stresses can affect the accumulation of metabolites in plants, including drought. In the present study, we found a great deal of variability in the seed metabolic profiles of the tolerant (Matterhorn, SB-DT2 and SB-DT3) common bean genotypes in comparison to the sensitive genotypes (Sawtooth, Merlot and Stampede) using ultrahigh performance liquid chromatography−tandem mass spectrometry (UPLC-MS). The genotypes were grown in the field and subjected to drought stress after flowering (terminal drought stress). We aimed to investigate the accumulation of genotype-specific metabolites and related pathways under terminal drought stress by comparing tolerant and sensitive genotypes within a race. A total of 26 potential metabolites were identified across genotype comparisons. Significant metabolic pathways, including monobactam biosynthesis, flavone and flavonol biosynthesis, pentose phosphate pathway, C5-branched dibasic acid metabolism, cysteine and methionine metabolism, vitamin B6 metabolism and flavonoid biosynthesis, were derived from the enriched metabolites. Many of these metabolic pathways were specific and varied with genotype comparisons. SB-DT2 vs. stampede revealed more significant metabolites and metabolic pathways compared to Matterhorn vs. Sawtooth and SB-DT3 vs. Merlot under terminal drought stress. Our study provides useful information regarding the metabolite profiles of seeds and their related pathways in comparisons of tolerant and sensitive common bean genotypes under terminal drought conditions. Further research, including transcriptomic and proteomic analyses, may contribute to a better understanding of molecular mechanisms and nutritional differences among seeds of common bean genotypes grown under terminal drought conditions.

Slow‐darkening pinto common bean (Phaseolus vulgaris L.) cultivar ‘Wildcat’ (Reg. no. CV‐345, PI 698190) was released by the University of Nebraska dry bean breeding program in 2018. It was bred for adaptation to western Nebraska growing conditions and enhanced resistance to bean rust, common bacterial blight (CBB), and Bean common mosaic virus (BCMV). The yield of Wildcat was comparable to conventional and slow‐darkening pinto bean cultivars grown in Nebraska from 2015 to 2020. During the 2017 Western Regional Bean Trial, 2017 Midwest Regional Performance Nursery, and 2018 Cooperative Dry Bean Nursery, Wildcat had a higher seed yield than ‘Twin Falls’, ‘Nez Perce’, ‘Black Foot’, ‘Montrose’, ‘Buster’, ‘ND‐Palomino’, and ‘La Paz’ at some locations. Wildcat has the Ur‐11 gene that confers resistance to all but one known bean rust race and carries the Indel NDSU_IND_11_48.459.896 marker tagging the Ur‐11 locus. Wildcat also has the SAP6 sequence characterized amplified region (SCAR) marker linked to a major CBB resistance quantitative trait locus, with an intermediate CBB rating (5.0) under field conditions at western Nebraska in 2020. Wildcat also carries the single dominant I gene that confers resistance to all non‐necrotic strains of BCMV and the SW13 SCAR marker linked to the I gene for resistance to BCMV. Wildcat has white flowers, blooms 46 d after planting, and is a full‐season bean, maturing 93 d after planting. The seed size of Wildcat, 43.3 g 100 seeds^–1 on average, was significantly larger than current conventional and slow‐darkening pinto beans.

Drought stress is an increasingly prevalent constraint to common bean (Phaseolus vulgaris L.) production in the United States and internationally. SB‐DT2 (Reg. no. GP‐310, PI 698187) is a pinto bean germplasm and SB‐DT3 (Reg. no. GP‐311, PI 698188) is a small red bean germplasm developed through shuttle breeding between Nebraska and Puerto Rico with broad temperate and tropical adaptation. These germplasm lines were developed through combining drought tolerance from the common bean Mesoamerican and Durango races and within the Mesoamerican race. SB‐DT2 had the highest geometric mean (GM) compared with the drought checks SB‐DT1, TARS‐MST1, and ‘Matterhorn’ from 2012 to 2018, meaning that it performed well under both stress and non‐stress environments. SB‐DT3 had the third highest GM, which was greater than the small red check ‘Merlot’. In addition to drought stress tolerance, SB‐DT2 and SB‐DT3 showed resistance to endemic strains of the rust pathogen at Fort Collins, CO (caused by Uromyces appendiculatus). SB‐DT2 carries the single dominant hypersensitive I gene that provides strain nonspecific resistance to the Bean common mosaic virus. Under drought stress, SB‐DT2 and SB‐DT3 flowered at 44 and 46 d, respectively; matured 86 and 88 d after planting, respectively; and are adapted to both temperate and tropical production environments. These germplasm lines were developed cooperatively by the University of Nebraska and the USDA‐ARS.

Common bean ( Phaseolus vulgaris L.) is consumed worldwide, with strong regional preferences for seed appearance characteristics. Colors of the seed coat, hilum ring, and corona are all important, along with susceptibility to postharvest darkening, which decreases seed value. This study aimed to characterize a collection of 295 yellow bean genotypes for seed appearance and postharvest darkening, evaluate genotype × environment (G × E) effects and map those traits via genome‐wide association analysis. Yellow bean germplasm were grown for 2 yr in Michigan and Nebraska and seed were evaluated for L*a*b* color values, postharvest darkening, and hilum ring and corona colors. A model to exclude the hilum ring and corona of the seeds, black background, and light reflection was developed by using machine learning, allowing for targeted and efficient L*a*b* value extraction from the seed coat. The G × E effects were significant for the color values, and Michigan‐grown seeds were darker than Nebraska‐grown seeds. Single‐nucleotide polymorphisms (SNPs) were associated with L* and hilum ring color on Pv10 near the J gene involved in mature seed coat color and hilum ring color. A SNP on Pv07 associated with L*, a*, postharvest darkening, and hilum ring and corona colors was near the P gene, the ground factor gene for seed coat color expression. The machine‐learning‐aided model used to extract color values from the seed coat, the wide variability in seed morphology traits, and the associated SNPs provide tools for future breeding and research efforts to meet consumers’ expectations for bean seed appearance.

Tepary bean (Phaseolus acutifolius A. Gray) is a drought and high ambient temperature tolerant crop native to the Sonoran Desert, the hottest and driest region in the United States and Mexico. Although tepary bean is an orphan crop with little current commercial production, there was a brief period of larger scale production in the early 1900s in California. Tepary bean has great potential as a novel crop in a warmer world climate and can be introduced as an alternative pulse crop in hot and/or dry regions worldwide. TARS‐Tep 23 (Reg. no. GP‐309, PI 698457) is an improved tepary bean germplasm with wide‐ranging adaptation to tropical and temperate regions experiencing high temperature and drought stress conditions, with broad resistance to bean rust and with resistance to common bacterial blight. It has a flat, mottled black seed type with good seed size, a Type III plant habit, and a short crop cycle of 55–61 d in the environments tested. This germplasm was developed cooperatively by the USDA‐ARS, Zamorano University, the University of California–Davis, and the University of Nebraska. The use of this improved germplasm by farmers in production zones affected by abiotic and biotic stresses, or by breeding programs, can potentially increase seed yields of this climate‐resilient crop.