Microsatellite marker diversity in common bean (Phaseolus vulgaris L.) Microsatellite marker diversity in common bean (Phaseolus vulgaris L.)

Honduras, Nicaragua, and Costa Rica, a convention that is accepted within this region. "Middle America" refers More than 60% of common bean production worldwide is derived to the combined regions of Central America and from cultivars of Middle American origin. Understanding the diversity of these will facilitate their use in genetic improvement. The objective Mexico.of this study was to analyze a collection of 269 landraces of common Singh et al. (1991a) proposed that within each gene bean (Phaseolus vulgaris L.) by correspondence analysis of random pool three races could be distinguished on the basis of amplified polymorphic DNA (RAPD) data to determine the genetic differences in plant and seed morphology and adaptastructure of the Middle American gene pool of cultivated bean. One tion regimes. Growth habit is an important distinguishhundred eighty landraces originating in Mexico, the remainder in ing criterion, and is classed as Type 1 (determinate Central America and secondary centers of diversity within the Ameribush), Type 2 (indeterminate upright bush), Type 3 cas, and two checks were studied. DNA was extracted, RAPD reac-(indeterminate semi-viney prostrate), and Type 4 (indetions carried out, and polymorphic bands were scored as present or terminate climbing) (CIAT, 1987). Within the Middle absent on the basis of 39 primers. Groups were formed which in American gene pool race Mesoamerica (M) is common part corresponded to races defined previously by morphological and agroecological criteria. However, tropical small-seeded Race M was to both Mexico and Central America, and is charactercomposed of two groups: one largely Mexican that included most ized by relatively small seed and warm lowland adaptasmall-seeded black beans of upright plant habit; and one Central tion. Most Race M landraces have habits of Type 2 or American with landraces of various seed colors. Most non-black small-3, although some have Type 4 habit. Commercial classes seeded germplasm of Race M phenotype from secondary centers within Race M include small black, small Central Amerigrouped with the Central American landraces, except for creamcan red and navy beans. Race Durango (D) is composed seeded and purple-seeded accessions from Brazil. Races D and J principally of growth habit Type 3 genotypes with small could be distinguished and within races D and J further divisions leaves, medium size seed, and adaptation to dry highcould be recognized which were related to geographic origin. The land areas of Mexico. Commercial Race D classes inmore commercial Race D landraces formed a genetic group that was clude pinto, great northern, and small red Mexican predominant in the western part of the Mexican highland plateau. Another Race D group was concentrated at the eastern extreme of beans. Race Jalisco (J) is found in the more humid the neovolcanic axis and was differentiated morphologically as well.

Landraces of common bean (Phaseolus vulgaris L.) pertaining to the Andean gene pool are remarkably diverse in plant and grain morphology and agroecological adaptation. The objectives of this study were to determine the genetic structure of a large sample of Andean landraces, and to establish a correspondence between Andean landraces and wild bean populations that might have served as the source of domesticated bean. A total of 182 landraces representing the three recognized races of Andean bean and including many popping bean types were analyzed using amplified fragment length polymorphism (AFLP) technology with multiple correspondence analysis (MCA) and unweighted pair group method with arithmetic mean (UPGMA). Twenty‐nine wild bean accessions representing the diversity of wild bean in South America and Middle America were also included. Two sets of primers were used to generate 189 polymorphic AFLP. The graph of the results of MCA indicated that most landrace accessions formed a single undifferentiated group, and analysis by UPGMA combined with bootstrapping confirmed this. A small number of outliers presented bands that suggested introgression from Mesoamerican beans. Among wild bean populations from South America, those from Bolivia graphed in closest proximity to the cultivated bean, suggesting that Bolivia might have been an important primary domestication site. The narrow genetic base of Andean beans emphasizes the need to broaden the genetic base of the Andean gene pool.

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Phaseolus beans are distributed worldwide and are cultivated in the tropics, subtropics, and temperate zones. The common bean is the most important grain legume for direct human consumption in the world. The objectives of this study were to isolate microsatellite repeats and to establish their discriminatory power (DL) to be used in bean diversity characterization and mapping. We isolated, cloned, and sequenced genomic DNA fragments that contained microsatellite loci from three genomic libraries of Phaseolus vulgaris L. The polymorphism of the microsatellites was evaluated in a panel of 21 P. vulgaris genotypes made up of cultivated and wild beans from the Mesoamerican and Andean pools, and nine genotypes from four Phaseolus species. The number of alleles per microsatellite locus ranged from 1 to 14, with an average of 6 alleles per primer pair. Almost all the microsatellite loci showed high levels of discriminatory power, with the highest value being 0.94. These results indicate that microsatellites can be valuable genetic markers for assessing genetic diversity in the P. vulgaris. The high levels of polymorphism of these new bean microsatellites and their wide cross‐species transportability make these new markers useful for mapping and molecular characterization of Phaseolus species.