Exploring genetic diversity of lowland avocado (Persea americana Mill.) as a genetic reservoir for breeding

The avocado (Persea americana Mill.) is highly valued worldwide for its desirable nutritional properties and broader applications in the oil and pharmaceutical industry. Despite northwestern Mexico is not considered as a region of the avocado origin, it possesses a high morphological diversity of avocado fruits and trees. In an effort to provide more information about the diversity present in this region and at the same time, to support a more efficient production of lowland avocado in a tropical semi desert climate, this study characterized the genetic diversity of avocado trees growing at northwestern Mexico. Genetic diversity was estimated by using eight microsatellite loci. 45 seed-derived trees, with contrasting fruit morphology were identified. Results showed a high level of genetic diversity with 11.5 alleles per locus, a polymorphic index content of 0.75, and observed and expected heterozygosity values of 0.58 and 0.79, respectively, these values were similar to those observed in germplasm banks and genotypes from centers of origin. Clustering analysis assigned local genotypes to six clusters but did not provide a clear separation among avocado races, suggesting that local genotypes are a result of racial hybridization. Interestingly, avocados from the Mexican race and the commercial variety Hass clustered into two different groups. Despite not being considered a center of origin, results confirm an extensive diversity in northwestern Mexico, encouraging further exploration and preservation of genotypes with desirable traits to future breeding programs for the selection of local genotypes adapted to a lowland tropical climate.