Evolution of avocados as revealed by DNA restriction fragment variation

Individuals representing the genus ıt Persea, subgenus ıt Persea were assayed for restriction fragment length polymorphisms in their chloroplast genome, nuclear ribosomal DNA, and the genes coding for the enzyme cellulase. The subgenus ıt Persea appears to consist of ıt P. schiedeana and a separate taxon containing the remaining species. ıt P. americana does not appear to be a monophyletic group. If ıt P. americana is to be maintained as a species containing var. ıt americana, var. ıt drymifolia, and var. ıt guatemalensis, then our data suggest that it should also contain varieties corresponding to ıt P. floccosa, ıt P. nubigena, and ıt P. steyermarkii. ıt P. americana var. ıt guatemalensis appears to have originated as a hybrid between ıt P. steyermarkii and ıt P. nubigena. The root-rot-resistant cultivar G755A is a hybrid progeny of ıt P. schiedeana and ıt P. americana var. guatemalensis. The three varieties of ıt P. americana were all distinguished by mutations.