Characters Related to Leaf Photosynthesis in Wild Populations and Landraces of Common Bean

Wild populations of common bean (Phaseolus vulgaris L.) vary in characters related to leaf photosynthesis. To investigate if such variation exists in leaf photosynthetic characteristics of landraces, and if wild accessions are similar to landraces within a region of origin, 47 wild populations and 47 landraces were evaluated in two field experiments in Colombia. Young unshaded fully expanded leaves of each accession were used to measure stomatal density, CO 2 exchange rates (CER), stomatal conductance, chlorophyll, soluble protein, and N content. As a group Andean accessions (both wild and landraces) had lower specific leaf weight, less chlorophyll, lower CER, lower stomatal conductance, less stomatal density, and higher N content as compared with Mesoamerican accessions. The Andean landraces had the lowest CER as opposed to Mesoamerican landraces which had the highest CER value. For most of the variables measured, univariate analysis of variance within a country of origin suggested that landraces were similar to wild populations. However, cluster analysis that included nine variables formed groups that suggested contrast both between centers of domestication and between wild and cultivated types. Cluster analysis performed for Mexico and Peru identified two major groups that corresponded to wild and landraces within those countries. We conclude that wild populations and landraces differ in characteristics related to leaf photosynthesis, at least in Peru and Mexico. Wild Peruvian populations had higher CER than landraces. Wild Andean and Mesoamerican populations were not different in CER; this is a very interesting observation that suggests that during domestication a decrease in CER occurred in Andean landraces.