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.