Genetic Diversity and Structure of Pepper (Capsicum Annuum L.) from Northwestern Mexico Analyzed by Microsatellite Markers

The analysis of the variability and genetic structure of wild and landrace populations of pepper ( Capsicum annuum L.) is important for the management and conservation of valuable genetic resources and to understand the consequences of domestication on the patterns of neutral genetic variation. For this purpose, 12 populations of wild peppers, 3 landrace populations and 7 hybrid populations from northwestern Mexico were studied using microsatellites. On average, 3.62 alleles per locus were detected in the wild relatives, 3.37 in the landraces, and 3.08 in the hybrids. According to the average values of expected heterozygosity ( H e), slightly greater genetic diversity was found among the wild relatives ( H e = 0.466) than in the hybrids ( H e = 0.440) or the landraces ( H e = 0.422). In terms of the average number of alleles per locus and the average expected heterozygosity, reductions of 8.18 and 10.25% were found in the genetic diversity of the landraces and hybrids, respectively, with respect to the wild populations. The genetic differentiation among the populations was the highest among hybrids (G ST = 0.324), followed by landraces (0.309) and wild relatives (the lowest, at 0.208). Cluster analysis clearly demarcated the wild relatives and domesticated populations into different groups. The high levels of genetic diversity found among C. annuum in northwestern Mexico suggest that the wild and landrace populations are a valuable resource that should be conserved.