Genetic diversity of Colombian landraces of common bean as detected through the use of silver-stained and fluorescently labelled microsatellites

Abstract

Colombia, situated at the northern end of the Andes mountains of South America and in proximity to Central America, is an important centre of diversity for common bean (Phaseolus vulgaris L.) that has a mix of cultivated germplasm from both major gene pools (Andean and Mesoamerican) for the species. Microsatellites are a useful marker system for analyzing genetic diversity of this crop and can be analyzed with manual (silver-stain) or automated (ABI) detection systems and using unlabelled or fluorescently labelled markers, respectively. The objectives of this research were to evaluate the genetic diversity of 92 Colombian landraces and gene pool controls with 36 fluorescent and 30 non-fluorescent microsatellite markers and to determine the extent of introgression between the Andean and Mesoamerican gene pools for this germplasm. A comparison of fluorescent versus non-fluorescent marker systems was performed with 14 loci, which were evaluated with both methods; the fluorescent markers were found to be more precise than the non-fluorescent markers in determining population structure. A combined analysis of 52 microsatellites using the 36 fluorescent markers and 16 non-overlapping, silver-stained markers produced an accurate population structure for the Andean gene pool that separated race Nueva Granada and race Peru genotypes and clearly identified introgression between these races and the gene pools. The results of this research are important for the application of microsatellite markers to diversity analysis in common bean and for the conservation of landraces in Colombia and neighbouring countries of Latin America, where similar germplasm exists and where gene pool or race mixtures also occur.

Genetic Control of Seed Coat Darkening in Common Bean Cultivars from Three Market Classes

“…The mean number of alleles per marker was 3.75. These estimates were lower than those obtained by Díaz et al (2011) and Perseguini et al (2011), who also analyzed the diversity of common bean lines based on microsatellite loci. However, these authors evaluated lines from germplasm banks, for which greater genetic variability was expected compared with analysis of lines collected from a study of a breeding program in which the genetic base is more restricted and selected for market requirements.…”

“…The estimation of genetic similarity among common bean elite lines using molecular markers allow us to make inferences regarding genetic variability among them (Díaz et al, 2011; Perseguini et al, 2011). Molecular markers have made valuable contributions in this respect, especially in detection of genetic relatedness among different genotypes in studies of genetic diversity and gene mapping.…”

Diversity and Population Structure of Common Bean from Brazil

“…Brazil is farther away from the Central American source of these types than it is from the Andean primary center of diversity. However, Brazil is relatively close to the Caribbean and Colombia where black beans are native and introgression between the genepools is common (Díaz et al, 2011; Durán et al, 2005). Mesoamerican beans were certainly present in these regions in pre‐Columbian times but how they were transported across the Amazonian basin from northern South America is an open question.…”

Diversity of Common Bean Landraces, Breeding Lines, and Varieties from Cuba

“…Therefore, the subdivision of the Cuban germplasm into two major genepools based on SSR results agrees with many previous analyses of worldwide and localized accessions and was not unexpected. It was, however, surprising that the Andean beans of Cuba were such a separate group from the Mesoamerican beans, indicating perhaps fewer centuries of sympatric distribution of the two genepools within Cuba compared with other parts of Latin America such as Colombia, where introgression is common (Díaz et al, 2011). When we compare Cuban common beans to previous studies of Caribbean germplasm using RAPD markers (Durán et al, 2005) we find the same pattern of large‐seeded Andean types distinguishable and separating from small to medium‐small Mesoamerican beans, as was found in Jamaica, Dominican Republic, and Puerto Rico.…”

“…Genepool mixing might be expected from growing genetic mixtures within landraces or from adaptation to new environments where both genepools provided adaptive alleles. Blending of Andean and Mesoamerican types is found in some parts of the tropics, especially in highland eastern and central Africa and notably as well in Colombia (Díaz and Blair, 2006; Díaz et al, 2011; Blair et al, 2010). Evidence of intergenepool introgression is lower in regions of common bean domestication, including the Andes Mountains of South America and the Mesoamerica region of Central America and Mexico (Avila et al, 2012; Blair et al, 2011).…”