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Bacterial brown spot (BBS) caused by Pseudomonas syringae pv. syringae (Pss), common bacterial blight (CBB) caused by Xanthomonas axonopodis pv. phaseoli (Xap) and Xanthomonas fuscans subsp. fuscans (Xff), and halo bacterial blight (HBB), caused by Pseudomonas syringae pv. phaseolicola (Psph), are major bacterial diseases that severely affect common bean yields and global food security. Andean-origin dry beans, representing large-seeded market classes, are particularly susceptible. Using 140,325 SNPs, a multi-locus GWAS was conducted on subsets of the Andean diversity panel (ADP) phenotyped for BBS in South Africa, CBB in Puerto Rico, South Africa, and Zambia, and HBB in South Africa, through natural infection, artificial inoculation, or both. Twenty-four QTL associated with resistance were identified: nine for BBS, eight for CBB, and seven for HBB. Four QTL intervals on Pv01, Pv03, Pv05, and Pv08 overlapped with BBS and HBB resistance. A genomic interval on Pv01, near the fin gene, which determines growth habit, was linked to resistance to all three pathogens. Different QTLs were detected for BBS and CBB resistance when phenotyped under natural infection versus artificial inoculation. These results underscore the importance of combining phenotyping methods in multi-GWAS to capture the full genetic spectrum. Previously recognized CBB resistance QTL SAP6 and SU91 and HBB resistance QTL HB4.2, and HB5.1, were observed. Other common (MAF >0.25) and rare (MAF <0.05) resistance QTL were also detected. Overall, these findings enhance the understanding and utilization of bacterial resistance present in ADP for the development of common beans with improved resistance. [ABSTRACT FROM AUTHOR]

'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 F7:8 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. Core Ideas: Kikatiti pinto bean has superior productivity in Tanzania.Kikatiti pinto possesses an effective combination of resistance genes to combat bean rust disease in East Africa.Kikatiti pinto possesses an effective combination of resistance genes to combat Bean common mosaic necrosis virus.Farmers ranked Kikatiti above local pinto cultivars for performance and market potential in on‐farm trials. [ABSTRACT FROM AUTHOR]

Common bean (Phaseolus vulgaris L.) is the most important grain legume for human consumption and has a role in sustainable agriculture owing to its ability to fix atmospheric nitrogen. We assembled 473 Mb of the 587-Mb genome and genetically anchored 98% of this sequence in 11 chromosome-scale pseudomolecules. We compared the genome for the common bean against the soybean genome to find changes in soybean resulting from polyploidy. Using resequencing of 60 wild individuals and 100 landraces from the genetically differentiated Mesoamerican and Andean gene pools, we confirmed 2 independent domestications from genetic pools that diverged before human colonization. Less than 10% of the 74 Mb of sequence putatively involved in domestication was shared by the two domestication events. We identified a set of genes linked with increased leaf and seed size and combined these results with quantitative trait locus data from Mesoamerican cultivars. Genes affected by domestication may be useful for genomics-enabled crop improvement.

The pinto bean (Phaseolus vulgaris L.), 'USDA Rattler' (Reg. no. CV‐350, PI 693789), was released by the USDA‐ARS in 2021 as a high‐yielding, upright, full‐season cultivar with abiotic stress tolerance. It was bred for broad adaptation to the different bean production regions across the United States by selection for high yield performance under nonstress and multiple stress trials in Washington state. The multiple stress trials included a "purgatory" plot with low fertility, intermittent drought, and soil compaction, and a separate trial which simulated terminal drought. Conversely, the nonstress trials were well watered and fertilized to optimize yield potential. Yield stability is evidenced by the mean seed yield for the breeding line PT11‐13, from which USDA Rattler was selected, numerically exceeding the trial means for 33 of 38 location‐years. Broad adaptation for USDA Rattler is further evidenced by an average seed yield of 4547 kg ha−1 across 10 location‐years in the Cooperative Dry Bean Nursery. Genetic markers as well as pathogen testing indicate USDA Rattler has I and bc‐3 gene combination for durable resistance to all known strains of Bean common mosaic virus and Bean common mosaic necrosis virus. Greenhouse testing with four races of the rust pathogen indicated USDA Rattler is fixed for the Ur‐3 resistance gene but is heterogenous for presence of the Ur‐11 resistance gene. The seed size, appearance, and canning quality characteristics of USDA Rattler meets the industry standards for packaging and processing. Core Ideas: USDA Rattler was bred for high yield potential under both favorable and stressful environments.USDA Rattler performed well in our "purgatory plot" used to select for drought and low soil fertility tolerance.USDA Rattler is resistant to all known strains of Bean common mosaic virus and Bean common mosaic necrosis virus.USDA Rattler is widely adapted to production regions across the United States. [ABSTRACT FROM AUTHOR]

Halo blight [caused by Pseudomonas syringae pv. phaseolicola (Burkh.) Young et al. (Psp)] is a serious seed-borne bacterial disease of common bean (Phaseolus vulgaris L.). A few resistance (R) genes and quantitative trait loci provide control to one or more races of the pathogen. To better understand monogenic resistance and improve breeding efficiency, we sought to tag and map a gene (Pse-1) in host differential cultivar UI-3 (previously named 'Red Mexican UI-3') that provides resistance to races 1, 5, 7, and 9 of Psp. Cosegregation for resistance to races 1, 5, 7, and 9, in a recombinant inbred population, 'Canadian Wonder'/UI-3 (CU) confirmed the effect of Pse-1 against multiple races of the pathogen. Bulked-segregant analysis in the CU population identified six random amplified polymorphic DNA (RAPD) markers tightly linked (0-3.3 cM) to Pse-1. Three of the RAPDs completely linked with Pse-1 in the CU population were converted to sequence characterized amplified region (SCAR) markers SH11.800, SR13.1150, and ST8.1350. The linked markers were used to integrate Pse-1 to linkage group B10 of the core map. Allelism tests ([F.sub.2]) confirmed relationships Of Pse-1 and Pse-4 derived from UI-3 with R genes in the other host differential cultivars. A survey of advanced lines and cultivars revealed that the SCAR markers generated in this study will have utility for marker-assisted selection of Pse-1 in germplasm from the Andean gene pool (e.g., kidney, calima) and from race Mesoamerican within the Middle American gene pool (black, carioca).

A periodic comparison of cultivars is essential to assess selection gains, determine deficiencies, define objectives, and set breeding priorities. Our objective was to assess the progress, or lack thereof, achieved in improving yield, plant type, maturity, and resistance to major bacterial, fungal, and viral diseases of dry bean of the western USA from 1918 to 1998. Twenty-five great northern, pink, pinto, and red cultivars were evaluated for seed yield at three locations in Idaho and for anthracnose, Bean common mosaic virus, Bean common mosaic necrosis virus, common and halo bacterial blights, Fusarium and Rhizoctonia root rots, Fusarium wilt, and white mold in Colorado, Idaho, and Washington between 1999 and 2006. Yield ranged between 2904 kg [ha.sup.-1] for pinto 'Ul 111' to 3921 kg [ha.sup.-1] for 'Bill Z', which represents a 35% gain in 54 yr. Yield gain in great northern was 587 kg [ha.sup.-1], pink 136 kg [ha.sup.-1], and red 687 kg [ha.sup.-1]. Stability indices ranged from 0.57 for 'Kodiak' to 1.86 for 'UI 3'. Maturity ranged from 90 d for 'UI 320' to 97 d for 'Frontier'. Seed weight ranged from 28 g for 'Viva' to 41 g for UI 320. An acceptable degree of resistance to Rhizoctonia root rot was achieved in most cultivars. All cultivars were susceptible to anthracnose, common bacterial blight, and white mold, and all except 'Chase' to halo blight. Only 'Matterhorn', 'Weihing', and Kodiak combined an upright Type II growth habit with resistance to BCMV and rust. An integrated breeding strategy should be explored for simultaneous improvement of multiple traits in future cultivars.

White mold caused by Sclerotinia sclerotiorum (Lib.) de Bary is a major disease limiting dry bean (Phaseolus vulgaris L.) production. Genetic resistance provides some control but is difficult to breed for because of low heritability. We sought to determine if marker-assisted selection for quantitative trait loci (QTL) conferring partial resistance could facilitate breeding for resistance to white mold in dry bean. The Phs marker linked with a QTL derived from landrace G122 on linkage group B7 was back-crossed into 'Winchester' pinto, forming two B[C.sub.3][F.sub.4:6] inbred line populations. The AW9.1200 and SS18.1650 markers linked with a QTL from snap bean breeding line NY6020-4 on B8 were backcrossed into 'Maverick' pinto and 'Matterhorn' great northern, forming B[C.sub.2][F.sub.4:6] inbred line populations. The B7 QTL in the B[C.sub.3][F.sub.4:6] populations on average explained 52% of the phenotypic variation for disease reaction in the greenhouse test and 10% across four field tests. The B8 QTL explained 30% in the greenhouse and 10% in the field. Averaged across tests and populations the B7 and B8 QTL conditioned 15 and 17% reduction in disease severity score, respectively. Linkage drag from selection of the B7 QTL was observed for yield. MAS for the B7 and B8 QTL was an effective breeding tool for introgressing partial resistance to white mold into susceptible pinto and great northern dry bean market classes, but further selection for agronomic performance may be required to obtain lines worthy of commercial production.

Breeding for genetic resistance to white mold [Sclerotinia sclcrotiorum (Lib.) de Bary] in dry bean (Phaseolus rulgaris L.) is difficult because of low heritability. To facilitate breeding, researchers have sought to identify QTL underpinning genetic resistance to white mold. We identified two QTL conditioning ICA Bunsi-derived resistance to white mold in a pinto x navy bean (Aztec/ND88-106-04) recombinant inbred line (85 RILs) population. ND88-106-04 is a navy breeding line with resistance to white mold derived from ICA Bunsi navy. Aztec pinto is susceptible. The QTL were located to linkage groups B2 and B3 of the core map. The B2 QTL expressed in three of four field environments explaining 24.7, 9.0, and 8.7% of the phenotypic variation for disease severity score. The B3 QTL expressed in two of four environments, explaining 15.7 and 5.3% of the phenotypic variation. The B2 QTL was identified previously in ICA Bunsi x navy and ICA Bunsi x black bean RIL populations. The resistance conferred by the B2 QTL has a physiological basis due to association with stay green stem trait and lack of association with disease avoidance traits. The B3 QTL, undetected in previous studies, was associated with disease avoidance traits (canopy porosity, plant height), stay green stem trait, and maturity. The B2 QTL with stable expression in multiple environments and across genetic backgrounds will be most amenable to manipulation by breeders.

Genetic resistance is an important component of integrated strategies used to control problematic diseases in common bean (Phaseolus vulgaris L.). Molecular linkage maps have been used to identify, tag, and map disease resistance genes and QTL in common bean, leading to improved breeding strategies and implementation of marker-assisted selection. Most widely used marker types, random amplified polymorphic DNA (RAPD) and amplified fragment length polymorphisms (AFLP), for linkage mapping in bean are located randomly throughout the genome and associate with particular traits by chance. We sought to determine the potential application of a new marker system, TRAP, which uses expressed sequence information and a bioinformatics approach to generate polymorphic markers around targeted candidate gene sequences. TRAP markers were amplified by fixed primers designed against sequenced expressed sequence tag (EST) associated with disease resistance in the Compositae Genomics database or against sequenced resistance gene analog (RGA) from common bean. Seventeen of 85 TRAP markers located in the BAT 93/Jalo EEP558 core mapping population mapped in the vicinity of R genes. Six of 21 TRAP markers generated in the Dorado/XAN 176 mapping population were linked with newly identified QTL, two conditioning resistance to ashy stem blight (14% and 16% of the phenotypic variation explained, [R.sup.2]), and one each conferring resistance to Bean golden yellow mosaic virus (BGYMV) (15%) and common bacterial blight (30%). The TRAP marker system has potential for mapping regions of the common bean genome linked with disease resistance., A GOAL of many crop-breeding programs is to incorporate marker-assisted selection (MAS) for disease resistance with traditional approaches to expedite germplasm enhancement and cultivar development (Miklas et al., 2006). For [...]