SSRs MARKERS REVEAL HIGH GENETIC DIVERSITY AND LIMITED DIFFERENTIATION AMONG POPULATIONS OF NATIVE GUATEMALAN AVOCADO

Abstract

Even though Guatemala is considered one of the three domestication centres of the avocado (Persea americana Mill), little is known about the genetic diversity of its native populations. This is the first study to explore avocado genetic diversity and population structure in native dispersal areas using microsatellite markers. We sampled 189 avocado trees grown from seeds in eight geographical populations, and 12 microsatellite loci were tested for diversity. There were a total of 289 alleles found throughout the 12 loci, with an average of 23.83 alleles per locus. The average observed and expected heterozygosity were 0.53 and 0.83, respectively. The analysis of molecular variance revealed that the eight populations comprised around 2% of the variation. Five of the 28 G'_ST(Nei) pairwise comparisons indicated no genetic difference. We discovered a mixture of avocado trees from various populations using unweighted pair group method with arithmetic mean (UPGMA) hierarchical cluster analysis. The sampled individuals were classified into three main genetic clusters by the model-based STRUCTURE and discriminant analysis of principal components (DAPC). The weak genetic structure exhibited by mixing avocado trees from different populations could be mainly attributed to high human-mediated gene flow (Nm = 12.25) due to avocado's importance in food, culture, and Guatemala's religion. The high genetic diversity found in the avocado germplasm suggests that it might be a valuable source of variable alleles that could be used in breeding programs for this crop in Guatemala.