Abstract
The knowledge and understanding of the genetic variability of common bean (Phaseolus vulgaris L.) germplasm is important for the implementation of measures addressed to their utilizations and conservation. The objective of this study was to characterize common bean in Uganda using polymorphic molecular markers for use in hybridization and variety development. Genomic DNA was extracted from plants at the first trifoliate leaf stage growing in pots using the modified cetyl-trimethylammonium bromide (CTAB) method. The gene pool membership (Andean vs. Mesoamerican) for each accession was established with the phaseolin marker. Simple sequence repeat (SSR) alleles were separated by capillary electrophoresis that provided further information on the organization of genetic diversity. The Andean and Mesoamerican genotypes were present in similar frequencies (51 vs. 49%, respectively). All SSR markers tested were polymorphic with mean polymorphism information content (PIC) of 0.8. The model-based cluster analysis of SSR diversity in the STRUCTURE software found three sub populations (K3.1, K3.2 and K3.3) genetically differentiated with moderate Wrights fixation indices (FST) values 0.14, 0.12 and 0.09, respectively and many cases of admixture. The STRUCTURE result was confirmed by Principal Coordinate analysis (PCoA) which also clustered beans in three groups. Most Andean genotypes were included in K3.1 and Mesoamerican genotypes belonged to the K3.2 and K3.3 subgroups. This study sets the stage for further analyses for agronomic traits such as yield, resistance to biotic and abiotic stresses and the need for germplasm conservation. Key words: Phaseolin, Simple sequence repeat (SSR), hybridization, wrights fixation index (FST), structure.
Highlights
Consists of two major gene pools, one originating among wild beans ranging from northern Mexico to Colombia (Mesoamerican gene pool) and the other descending from wild beans distributed from southern Peru to northwestern Argentina (Andean gene pool) Freyre et al, 1996)
Gene introgressions between the two gene pools have occurred in Uganda with some accessions existing as hybrid genotypes of Andean and Mesoamerican gene pools
The 22 SSR markers used in this study showed high polymorphism among common bean samples in Uganda
Summary
Consists of two major gene pools, one originating among wild beans ranging from northern Mexico to Colombia (Mesoamerican gene pool) and the other descending from wild beans distributed from southern Peru to northwestern Argentina (Andean gene pool) Freyre et al., 1996). The common bean has a widespread distribution on many continents such as Mesoamerica, South. It reached Uganda presumably in the 18th century via the East African coast (Gepts and Bliss, 1988). The gene pool of the domesticated species is organized into four
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