Randomly amplified polymorphic DNA marker-based germplasm and genetic mapping studies in common bean

The first objective of this research was the development of a molecular marker based system for doing genetic and comparative genetic studies in common bean (Phaseolus vulgaris L.). In Chapter 1, RAPD marker based linkage maps were developed in the Eagle x Puebla 152 and BAT 93 x Jalo EEP558 recombinant inbred line populations of common bean based on segregation of 547 RAPD markers, including 56 codominant markers. The results indicated perfect colinearity of maps and thus the utility of RAPDs for comparative mapping within the species. Furthermore, RAPD markers were found to be clustered on the bean genetic map and non-randomly distributed with respect to the gene pool origin of the parental allele. In Chapter 2 the integrated map was extended to include two additional populations and a total of 831 unique RAPD markers. This integrated map was used to develop a comparative map of the locations of QTL for resistance to common bacterial blight (CBB) (Xanthomonas campestris pv. phaseoli). Among previously identified CBB resistance QTL the results indicated population unique QTL. Thus, the results allowed the identification of genetically unique sources of resistance and suggest opportunities for the improvement of resistant varieties through pyramiding of these unique resistance genes.; In Chapter 3 core and reserve Mexican common bean germplasm collections were compared based on 227 polymorphic RAPD markers and characterization information. The results indicated no significant differences in the genetic structure and diversity of core and reserve samples. Thus, the results indicated that the core will be representative of the reserve collection but necessarily more diverse. Finally, in Chapter 4 this germplasm research was extended to a large sample of bean germplasm including 652 wild and cultivated genotypes. The analysis of RAPD data indicated greatest marker diversity in wild Mesoamerican germplasm followed by Mesoamerican landrace germplasm. RAPD marker diversity in these groups was significantly greater than in groups of Andean wild and landrace genotypes, which were equivalent. Mesoamerican wild genotypes appear to be relative unrelated to cultivated genotypes from either gene pool while Andean wild beans were found to be very closely related to Andean cultivated beans.