Genome structure, evolution and diversity in common bean ( Phaseolus vulgaris) and its relatives

The legume family (Fabaceae) is the third largest family of higher plants, including a number of agriculturally important crops. Recent progress in genome sequencing of multiple legume species has provided useful resources to study chromosome biology in combination with fluorescence in situ hybridization (FISH) technology. In this thesis research, we report chromosome studies of two important legume crops: common bean (Phaseolus vulgaris ) and cowpea (Vigna unguiculata). Using a large set of genome sequencing data and bacterial artificial chromosome (BAC) end sequences, centromeric satellite repeats were identified and characterized in common bean. We found several interesting features of centromere structures unique to common bean. Using the centromeric repeats, subtelomeric repeat khipu, rDNAs, and chromosome-specific BAC clones, a FISH-based karyotype map of common bean was established. We applied these karyotyping tools to several common bean accessions and relatives. Comparison of these karyotype maps showed the conservation and diversity of the genome at the chromosomal level. We also investigated chromosomal structure of cowpea, a closely related species of common bean. We analyzed pericentromeric and centromeric regions associated with interesting chromosome structures and identified chromosome-specific BAC clones, which will help further genome analyses of cowpea including on-going genome sequencing project. Overall, the data obtained in this thesis advances our knowledge on genome and chromosome structure and evolution in common bean and its relatives and in cultivated cowpea.