Genetic resources and breeding priorities in Phaseolus beans: Vulnerability, resilience, and future challenges

Authors: PARKER, TRAVIS - University Of California, Davis; ACOSTA GALLEGOS, JORGE - Instituto Nacional De Investigaciones Forestales Y Agropecuarias (INIFAP); BEAVER, JAMES - University Of Puerto Rico; BRICK, MARK - Colorado State University; BROWN, JUDITH - University Of Arizona; Cichy, Karen; DEBOUCK, DANIEL - International Center For Tropical Agriculture (CIAT); DELGADO-SALINAS, ALFONSO - Universidad Autonoma De Ciudad Juarez; DOHLE, SARAH - Delaware Valley College; ERNEST, EMMALEA - University Of Delaware; ESTEVEZ DE JENSEN, CONSUELO - University Of Puerto Rico; GOMEZ, FRANCISCO - Michigan State University; Hellier (ctr), Barbara; KARASEV, ALEXANDER - University Of Idaho; KELLY, JAMES - Michigan State University; MCCLEAN, PHILIP - North Dakota State University; Miklas, Phillip - Phil; MYERS, JAMES - Oregon State University; OSORNO, JUAN - North Dakota State University; PASCHE, JULIE - North Dakota State University; Pastor Corrales, Marcial - Talo; Porch, Timothy - Tim; STEADMAN, JAMES - University Of Nebraska; URREA, CARLOS - University Of Nebraska; Wallace, Lyle; DIEPENBROCK, CHRISTINE - University Of California, Davis; GEPTS, PAUL - University Of California, Davis

Submitted to: Plant Breeding Reviews
Publication Type: Book / Chapter
Publication Acceptance Date: 11/18/2022
Publication Date: 11/18/2022
Citation: Parker, T.A., Gallegos, J.A., Beaver, J., Brick, M., Brown, J.K., Cichy, K.A., Debouck, D., Delgado-Salinas, A., Dohle, S., Ernest, E., Estevez de Jensen, C., Gomez, F., Hellier, B.C., Karasev, A.V., Kelly, J.D., McClean, P., Miklas, P.N., Myers, J.R., Osorno, J., Pasche, J.S., Pastor-Corrales, M.A., Porch, T.G., Steadman, J.R., Urrea, C., Wallace, L.T., Diepenbrock, C.H., Gepts, P. 2022. Genetic resources and breeding priorities in Phaseolus beans: Vulnerability, resilience, and future challenges. Plant Breeding Reviews. Volume 46. Somerset, New Jersey: John Wiley & Sons, Inc. p. 289-420. https://doi.org/10.1002/9781119874157.ch6.
DOI: https://doi.org/10.1002/9781119874157.ch6

Interpretive Summary: Among grain legumes, beans of the genus Phaseolus are important crops for direct human consumption after cooking, most commonly as dry seeds. Phaseolus bean crops are vulnerable to pathogens such as fungi, bacteria, viruses, pests such as insects, and increasing pressure from abiotic stressors in the face of climate change, including heat, drought, and flooding. These factors are predicted to drastically reduce the suitable production area for Phaseolus beans in coming decades. This review describes the major Phaseolus crop vulnerabilities and available and needed resources to address the vulnerabilities. Crop vulnerability is central to plant breeding and food security. Crop vulnerability refers to the potential for biotic or abiotic factors to reduce crop productivity and/or quality, and is intrinsically linked to the level of genetic diversity found in agricultural populations. Crops with low diversity present a genetically uniform background, making them similarly susceptible to yield-reducing factors. These agents include pathogens, pests, or adverse abiotic factors including those related to climate change. Potential remedies to these vulnerabilities include increasing crop biodiversity through plant exploration, conservation, pre-breeding, and genetic and genomic study of the rich Phaseolus germplasm resources. Identification and deployment of these resources will be crucial for maximizing production and quality of a genus that is globally important for food and nutritional security.

Technical Abstract: Phaseolus beans provide an abundant and sustainable source of protein and micronutrients for populations around the world. The genus includes seven independently domesticated gene pools, multiple uses (e.g., snap, shelling, popping,and dry beans), and numerous market classes and locally preferred categories. These groups can often be hybridized with one another and with wild relatives to move useful alleles into improved cultivars belonging to different market classes. Despite this, production faces several major hurdles. These include the evolution and changing patterns of pathogens such as fungi, bacteria, viruses, pests such as insects, and increasing pressure from abiotic stressors in the face of climate change, including heat, drought, and flooding. These factors are predicted to drastically reduce the suitable production area for Phaseolus beans in coming decades. Use of non-commercial germplasm (e.g., wild and domesticated relatives and landrace or heirloom varieties) will be key to countering these pressures. In recent years, widespread genetic erosion has occurred in wild populations in their native environments due to human encroachment. Similar patterns have occurred among landraces, as socio-economic factors have led to the increasing production of monocultures in areas such as Latin America and Africa. Simultaneously, new germplasm introductions by gene banks such as those of CIAT and USDA-NPGS have ground to a near standstill, with novel wild entries added from 2010-2020 numbering less than 10% of those collected two decades before. To explore the potential of Phaseolus gene banks to combat threats to genetic diversity and production, the Phaseolus Crop Germplasm Committee was charged by the USDA-NPGS to address the issue of genetic vulnerabilities of Phaseolus beans, with a special emphasis on those relevant for production in the United States. Genetic vulnerability is defined here as the threats to existing genetic diversity in the genus that would diminish or prevent genetic improvement of the crop. Potential remedies to these vulnerabilities include increased exploration, conservation, pre-breeding, and genetic and genomic study of the rich germplasm resources in the genus. Identification and deployment of these resources will be crucial for maximizing production and quality of a genus that is globally important for food and nutritional security.