1 Phaseolus vulgaris (Beans) Phaseolus vulgaris (Beans) dry beans are Brazil, Mexico, China, and the USA. Annual production of green beans is around 4.5 P Gepts million tonnes, with the largest production around Copyright ß 2001 Academic Press the Mediterranean and in the USA. doi: 10.1006/rwgn.2001.1749 Common bean was used to derive important prin- ciples in genetics. Mendel used beans to confirm his Gepts, P results derived in peas. Johannsen used beans to illus- Department of Agronomy and Range Science, University trate the quantitative nature of the inheritance of cer- of California, Davis, CA 95616-8515, USA tain traits such as seed weight. Sax established the basic methodology to identify quantitative trait loci (for seed weight) via co-segregation with Mendelian mar- Beans usually refers to food legumes of the genus kers (seed color and color pattern). The cultivars of Phaseolus, family Leguminosae, subfamily Papilio- common bean stem from at least two different domes- noideae, tribe Phaseoleae, subtribe Phaseolinae. The tications, in the southern Andes and Mesoamerica. In genus Phaseolus contains some 50 wild-growing spe- turn, their respective wild progenitors in these two cies distributed only in the Americas (Asian Phaseolus regions have a common ancestor in Ecuador and have been reclassified as Vigna). These species repre- northern Peru. This knowledge of the evolution of sent a wide range of life histories (annual to perennial), common bean, combined with recent advances in the growth habits (bush to climbing), reproductive sys- study of the phylogeny of the genus, constitute one of tems, and adaptations (from cool to warm and dry the main current attractions of beans as genetic organ- to wet). The genus also contains five domesticated isms. All species of the genus are diploid and most species: in decreasing order of importance, common have 22 chromosomes (2n 2 x 22). A few species bean (Phaseolus vulgaris L.), lima bean (P. lunatus L.), show an aneuploid reduction to 20 chromosomes. The runner bean (Phaseolus coccineus L.), tepary bean genome of common bean is one of the smallest in the (P. acutifolius A. Gray), and year bean (P. polyanthus legume family at 625 Mbp per haploid genome. Nor- Greenman), with distinct adaptations and reproduc- mal mitotic or meiotic chromosomes are very small tive systems: mesic and temperate, predominantly (1±3:m), metacentric or submetacentric. A karyotype self-pollinated; warm and humid, predominantly self- has been developed for P. vulgaris and P. coccineus pollinated; hot and dry, cleistogamous; cool and based on polytene chromosomes of the embryo sus- humid, outcrossing; and cool and humid, outcrossing, pensor cells. There are three or four rRNA loci respectively. Lima bean is phylogenetically more dis- (nucleolar organizing regions). In situ hybridization tant from the other domesticated species, which are with radioactive or fluorescent probes have been per- sibling species and constitute a syngameon. The prin- formed on mitotic or polytene chromosomes for cipal species economically and scientifically is com- rRNA, telomeric, and single-copy sequences. Highly mon bean. It originated in Latin America where its repeated sequences comprise some 20% of the genome. wild progenitor (P. vulgaris var. mexicanus and var. They are distributed primarily in highly heterochro- aborigineus) has a wide distribution ranging from matic regions and in chromosome ends. Satellite DNA northern Mexico to northwestern Argentina. Large is located mostly around centromeres. An as yet germplasm collections of domesticated and wild incomplete set of five trisomic stocks has been iden- forms are located at CIAT, Cali, Colombia and tified. A consensus molecular linkage map, correlating USDA, Pullman, Washington, USA. The reference some 12 maps, has been established based on RFLP, collection of Phaseolinae is located at the National RAPD, isozyme, AFLP, ISSR, microsatellite, and Botanical Garden, Meise, Belgium. phenotypic markers. The average total map length is Common bean is the most important legume 1200 cM, consistent with the average number of chias- worldwide for direct human consumption. The crop is mata per bivalent (1.9). A single estimate of the aver- consumed principally for its dry (mature) beans, shell age relationship of physical vs. physical distance gave beans(seedsatphysiologicalmaturity),andgreenpods. 400 000 bp per cM, close to the genome-wide average When consumed as seed, beans constitute an import- of 500 000 bp per cM. The genome of common bean is ant source of dietary protein (22% of seed weight) colinear with that of Vigna sp. (also belonging to the that complements cereals for over half a billion people subtribe of the Phaseolinae within the tribe Phaseo- mainly in Latin America. Annual production of dry leae), but shows many rearrangements when com- beans is around 15 million tonnes and average yield pared to that of soybean (subtribe of the Glycininae is700 kg ha1, although yields in certain countries within the tribe Phaseoleae). A retrotransposon family reach 2000±3000 kg ha1. The largest producers of of the copia type has been described. Bacterial artifi- cial chromosome libraries have been established for Phaseolus vulgaris (Beans) 2 common bean. Major genes or quantitative trait loci include an Agrobacterium-mediated system in P. acu- for the domestication syndrome (reduced seed disper- tifolius and a biolistics method in P. vulgaris. sal and seed dormancy, compact growth habit, photo- period insensitivity, seed size, color, and color pattern) Further Reading have been located on the linkage map, as have clusters http://agronomy.ucdavis.edu/gepts/geptslab.htm of resistance genes and resistance gene analogs (to http://www.ba.cnr.it/Beanref/ viral, fungal, and bacterial diseases), and genes for http://beangenes.cws.ndsu.nodak.edu:80/ Rhizobium nodulation, canning quality, and drought tolerance. In addition, several unmapped genes, espe- See also: 1122 (Rhizobium), 1664 (Glycine max cially for disease resistance and seed color and color (Soyabeans)), 1638 (Transfer of Genetic pattern, have been tagged with molecular markers. Information from Agrobacterium tumefaciens to Transformation systems have been established. These plants).