TITLE:
Analysis of Sesquiterpene Distributions in the Leaves, Branches, and Trunks of Avocado (Persea americana Mill.)
AUTHORS:
Jerome Niogret, Nancy D. Epsky, Elena Q. Schnell, Raymond J. Schnell, Robert R. Heath, Alan W. Meerow, Paul E. Kendra
KEYWORDS:
Avocado; Persea americana; Sesquiterpenes; α-Copaene; Redbay Ambrosia Beetle; Xyleborus glabratus
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.4 No.4,
April
25,
2013
ABSTRACT: Avocado is a
commercially valuable fruit crop cultivated in tropical and subtropical
climates throughout the world. Taxonomists recognize three horticultural races
of avocado, consisting of Mexican (Persea
americana var. drymifolia), Guatemalan
(P. americana var. guatemalensis), and West Indian (P. americana var. americana) varieties. Published research that attempted to
differentiate among the horticultural races by using leaf chemistry found that
sesquiterpene content was only useful for discrimination of pure Mexican from
Guatemalan and West Indian, but not to distinguish between Guatemalan and West
Indian races. This study presents a sampling method for analysis of
sesquiterpenes from avocado leaf, branch and trunk samples. Our results indicate
that sesquiterpene content from leaves and small diameter branches (2.5 cm) was highly variable; however,
sesquiterpenes were much less variable within wood from larger diameter
branches and trunk samples, providing information representative of avocado
varietal differences. In addition to chemotaxonomic applications, information
on sesquiterpene content of avocado wood is needed for identification of
host-based attractants for a new avocado pest, the redbay ambrosia beetle (Xyleborus glabratus). This insect
vectors a fungal pathogen that causes laurel wilt, a lethal vascular disease
that currently threatens avocado production in south Florida, USA. Females of X. glabratus identify appropriate host
trees based on emissions of terpenoids, particularly α-copaene. Our results are discussed in terms of how proximo-distal
distributions of sesquiterpenes may function as host-location cues by this
invasive wood-boring pest.