Analysis of genetic structure in widely distributed common bean landraces with different plant growth habits using SSR and AFLP markers
The genetic variation in common bean (Phaseolus vulgaris L.) landraces with different growth habits, which are grown over a wide and environmentally heterogeneous area in southern Italy, was studied to help define strategies for conservation of genetic resources. Accessions of three landraces, a'Marrozzo and Poverella with indeterminate growth habits, and Verdolino with a determinate growth habit, were scored for 30 simple sequence repeat (SSR) and 393 amplified fragment length polymorphism (AFLP) loci using eight primer combinations. Very low heterozygosity was observed, and all 73 plants analyzed showed different genotypes when comparing their alleles at the SSR or AFLP loci. The analyzed genotypes were clustered first according to plant growth habit and then in distinct groups according to landrace classification. Genetic differentiation among landraces was higher for AFLP (FST = 0.64) than for SSR loci (FST = 0.31), and variation within landraces was higher in a'Marrozzo, which is widely distributed over four river catchment basins. The proportion of alleles common to all three landraces was much larger for AFLP (62.34%) than for SSR (27.13%), while the alleles found in only one landrace were more frequent for SSR (47%) than for AFLP (8.14%). The large number of SSR and AFLP alleles shared between a'Marrozzo and Poverella (both with indeterminate growth habits) indicates their common evolutionary history.