Variation in Herbivore and Methyl Jasmonate-Induced Volatiles Among Genetic Lines of Datura wrightii

Many plant species produce volatile organic compounds after being damaged by herbivores. The production of volatiles also may be induced by exposing plants to the plant hormone, jasmonic acid, or its volatile ester, methyl jasmonate. This study addresses the induction of the production volatile organic compounds among genetic lines of Datura wrightii. Within populations, some plants produce glandular trichomes, whereas others produce nonglandular trichomes, and trichome phenotype is controlled by a single dominant gene. Glandular trichomes not only confer resistance to some herbivorous insects, but they also inhibit many natural enemies of those herbivores. Because of the potential benefit of natural enemies that use volatile cues to find individuals of the non-glandular phenotype, it is reasonable to ask if plants of D. wrightii that differ in trichome morphology might produce different blends of volatile compounds. Volatile compounds were collected from eight genetic lines of plants that had been backcrossed for three generations. Volatiles were collected from pairs of sibling plants before and after insect damage or treatment with methyl jasmonate. Within each pair, one sib expressed glandular trichomes and the other expressed nonglandular trichomes. Overall, plants produced an array of at least 17 compounds, most of which were sesquiterpenes. Total production of volatiles increased from 3.9- to 16.2-fold among genetic lines after insect damage and from 3.6- to 32-fold in plants treated with methyl jasmonate. The most abundant compound was (E)-β-caryophyllene. This single compound comprised from 17 to 59% of the volatiles from insect-damaged plants and from 24 to 88% of the volatiles from plants treated with methyl jasmonate, depending upon genetic line. The production of (E)-β-caryophyllene by the original male parents of the eight genetic lines was significantly related to the mean production of their third-generation backcross progeny indicating that the variation in the production of (E)-β-caryophyllene was inherited. Blends did not differ qualitatively or quantitatively between sibs expressing glandular or nonglandular trichomes.