Gene Pool Classification of Common Bean Landraces from Chile Based on RAPD and Morphological Data

Abstract

Landraces of common bean (Phaseolus vulgaris L.) from Chile are a phenotypically diverse group whose relationship to the two major gene pools (Andean and Mesoamerican) is unclear. The genetic composition of 69 Chilean landraces, 15 commercial cuitivars grown in Chile, and 11 previously characterized check accessions was examined using RAPDs (random amplified polymorphic DNA). The 25 primers used generated 106 polymorphic bands. A genetic distance (GD) matrix based on simple matching of RAPD phenotypes was converted to a two dimensional plot using multidimensional scaling (MDS). Two major clusters, encompassing most of the accessions, were apparent on the resulting plot and were identified with the Andean and the Mesoamerican gene pools. No obvious signs of introgression or hybridization between gene pools were observed. Clustering analysis using bootstrap samples of the RAPD bands showed that as few as 20 randomly chosen bands could classify the accessions into the correct gene pools nearly as well as all 106 bands. In general, the Andean landraces were collected at more northerly latitudes and higher altitudes than the Mesoamerican landraces. Morphological data were collected for 63 landraces for seven numerical traits and 13 categorical traits. The morphological data used were to create a distance matrix and analyzed as with the RAPD data, but no clear separation of the groups was seen. Accessions from the two groups identified by RAPDs differed significantly for 11 of the 20 traits examined. It was concluded that by RAPDs, the Chilean landraces could be readily classified into the Andean and Mesoamerican gene pools. Morphological traits were less effective at classification.