The 2012 ASHS Annual Conference

Avocado (Persea americana Mill.) is a major tropical fruit crop native to Mesoamerica and domesticated around 8000 to 7000 BC.  It is a member of the Laureace family and currently classified into three subspecies or races: Guatemalan (G), Mexican (M) and West Indian (WI) according to their ecological adaptation, botanical descriptors and physiological traits.  The goals of this research were to: a) to characterize race, interracial admixture, population structure, and genetic diversity of avocado accessions using a set of SSR markers and b) to evaluate the mislabeling errors present in these accessions.  A total of 354 individuals from SHRS, Fairchild Farm, and P. schideana from Mexico were genotyped using SSR markers.  Preliminary results indicated that mislabeling was estimated at 9.59%. SSR marker SHRSPa109 was the most informative locus followed by SHRSPa258 with 37 and 34 alleles, respectively, and average polymorphism information content (PIC) value of 0.76.  The least informative loci were SHRSPa167 and SHRSPa177 with 4 alleles each.  The observed heterozygosity (H_obs) was 0.59.  Bayesian cluster analysis assigned groups into the Guatemalan, Mexican, West Indian races of P. americana, admixed interracial hybrids (GxWI, GxM, MxG, MxWI, WIxG, and WIxM), Complex Hybrids and P. schideana.  Assignments were made based on coefficients of membership and degree of admixture or allelic contributions within a group.  In addition, Principal Component Analysis (PCA) and genetic distance analysis were calculated among all possible individual combinations within the SSR diversity data the results of which agreed with the Bayesian evaluation.  The advent of DNA genotyping technologies has provided new avenues of research in plant genetics where population genetic approaches can be used to better understand genetic and phenotypic variation.