GENETIC-RELATIONSHIPS OF AVOCADO (PERSEA-AMERICANA MILL) USING RAPD MARKERS

RAPD (randomly amplified polymorphic DNA) analysis was carried out on 16 accessions representing the three ecological races of avocado (Pers ea americana Mill.), and one accession of P. schiedeana Nees. Twenty t wo preselected primers produced 133 polymorphic DNA fragments in the R APD assay of the avocado accessions. One primer was identified which c ould differentiate each of the avocado accessions. Potentially race-sp ecific markers for each of the Mexican, Guatemalan, and West Indian ra ces, have been detected. A Jaccard's similarity coefficient matrix was generated and a dendrogram constructed using UPGMA (unweighted pair-g roup method of arithmetic averages) cluster analysis. Percentage simil arity between avocado accessions ranged from 46% to 85%. The lowest si milarity (between 22% and 29%) was revealed between P. schiedeana and any P. americana accession. Average similarity within races of avocado was 75% for the Mexican race, 71% for the West Indian race and 73% fo r the Guatemalan race. Average similarity between races ranged from 53 % to 58%. The dendrogram identified three groups, representing the rac es of avocado. These results are in concordance with the present class ification of avocado into three subspecies (varieties) of P. americana , namely drymifolia, americana, and guatemalensis, corresponding to th e Mexican, West Indian and Guatemalan races, respectively, and confirm the separate species status of P. schiedeana. We conclude that RAPD m arkers may be useful for the classification of avocado and for the ass essment of genetic diversity of avocado germplasm.