GENETIC-RELATIONSHIPS WITHIN AVOCADO (PERSEA-AMERICANA MILL) CULTIVARS AND BETWEEN PERSEA SPECIES

The origin of avocado (Persea americana Mill) cultivars, as well as th e genetic relationships between Persea species, are not well defined a nd are based mainly on morphological parameters. Minisatellite DNA mar kers were used to analyze 24 P. americana cultivars in an attempt to d efine their racial allocation. DNA mixes representing the three races were evaluated and used for analysis. The allocation of 19 of the abov e cultivars was substantiated by the DNA markers, while new suggestion s were offered regarding the remaining five. Eight cultivars, of unkno wn racial origin, were also examined, and a phylogenetic tree suggesti ng their origin is offered. Selfing progeny of five cultivars were ana lyzed for six morphological traits which differentiate the three races , and were compared to their parents in order to assess their origin. Eleven Persea species were analyzed, using DNA fingerprint patterns an d SSR (simple sequence repeat) alleles, in order to identify the genet ic relationships among the Persea species, and between them and the th ree P. americana races. The phylogenetic tree obtained is presented. T he high value of variation between the avocado cultivars and Persea sp ecies observed in this work, suggests that the validity of race and sp ecies definition within Persea be treated with caution.