Exogenous methyl jasmonate induces volatile emissions in cotton plants

We investigated the effect of exogenous methyl jasmonate (MeJA) on the emis sion of herbivore-induced volatiles; these volatile chemicals can signal na tural enemies of the herbivore to the damaged plant. Exogenous treatment of cotton cv. Deltapine 5415 plants with MeJA induced the emission of the sam e volatile compounds as observed for herbivore-damaged plants. Cotton plant s treated with MeJA emitted elevated levels of the terpenes (E)-beta -ocime ne, linalool, (3E)-4,8-dimethyl-1,3,7-nonatriene, (E,E)-alpha -farnesene, ( E)-beta -farnescne, and (E,E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene com pared to untreated controls. Other induced components included (Z)-3-hexeny l acetate, methyl salicylate, and indole. Methyl jasmonate treatment did no t cause the release of any of the stored terpenes such as alpha -pinene, be ta -pinene. alpha -humulene, and (E)-beta -caryophyllene. In contrast, thes e compounds were emitted in relatively large amounts from cotton due to phy sical disruption of glands by the herbivores. The timing of volatile releas e from plants treated with MeJA or herbivores followed a diurnal pattern, w ith maximal volatile release during the middle of the photoperiod. Similar to herbivore-treated plants, MeJA treatment led to the systemic induction o f (Z)-3-hexenyl acetate, (E)-beta -ocimene, linalool, (3E)-4,8-dimethyl-1,3 ,7-nonatriene, (E,E)-alpha -farnesene, (E)-beta -farnescne, and (E,E)-4,8,1 2-trimethyl-1,3,7,11-tridecatetraene. Our results indicate that treatment o f cotton with MeJA can directly and systemically induce the emission of vol atiles that may serve as odor cues in the host-search behavior of natural e nemies.