A Comparison of Leaf Terpenes in Persea Subgenus Persea

Abstract

Leaf essential-oil components of 10 avocado cultivars and two closely related species were analyzed by gas chromatography. Three-dimensional computer analyses gave highly reproducible results which, however, provided dubious additional elucidation of taxonomic relationships. But the 13 preponderant terpenes together suggested relationships that were internally consistent, that agree well with known morphological differences, and that point to a clarification of Persea subgenus Persea taxonomy. Cultivars of the so-called West Indian and Mexican horticultural races had a similar distribution pattern of major terpenes. The Guatemalan horticultural race had a different distribution pattern, much like that of both P. nubigena and P. schiedeana. On the basis of these and other observations, it is proposed that the West Indian, Mexican, and Guatemalan horticultural races be classified as botanical varieties, with the designations P. americana var. americana, P. americana var. drymifolia, and P. americana var. guatemalensis (var. nov.), respectively. Persea nubigena should probably be relegated to varietal status: P. americana var. nubigena. This seems reasonable also for P. floccosa, which would then be P. americana var. floccosa. Persea schiedeana is of uncertain status. Possible phylogenetic relationships are outlined.