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  • Author or Editor: Steve Beebe x
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Nuñas are a type of common bean (Phaseolus vulgaris) that possess the unusual characteristic of popping or expanding their cotyledonary tissue when heated. Numerous landraces of nuña beans were domesticated in the Andean region of South America (Peru, Bolivia, and Ecuador) and have been grown and consumed in this region since antiquity. The practical consideration in the domestication of nuñas in the high Andes was likely due to the greater energy efficiency in cooking toasted vs. boiled seeds.The Phaseolus germplasm bank at CIAT (Centro Internacional de Agricultura Tropical) has developed a core collection of Andean beans that includes numerous nuña landraces. Based on the wide range of phaseolin types observed among nuña landraces, it has been hypothesized that nuñas may represent a greater source of genetic diversity compared to other landraces and cultivars of common bean. Eighty nuña accessions and 120 nonpopping common bean accessions were randomly sampled from the CIAT Andean germplasm core collection. The 200 accessions were characterized for 140 mapped RAPD markers. The objectives of our research were to 1) understand the genetic structure of nuña bean accessions relative to other Andean common beans, and 2) to measure the genetic distance and genetic diversity between nuña and other Andean bean populations.

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More than 400 cultivars and breeding lines of Phaseolus vulgaris have been analyzed for 100 RAPD markers. The data set includes cultivars from all market classes of dry and snap beans, including entries from North America, Central America, and Europe. Genetic dissimilarities were calculated as the fraction of polymorphisms scored for each genotype pair. The distribution of genotypes revealed using principle components analysis and multi-dimensional scaling on the matrix of genetic dissimilarities agrees in general with phenotypic classification. We are currently studying the relationship of marker data to pedigree information. We are also examining individual marker and marker linkage distributions as they relate to the overall patterns of diversity.

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