Figure 2.

Cotton plants locally emit different amount of volatiles in response to elicitation by different caterpillar regurgitants. Plants were subjected to the following treatments: undamaged (Control), mechanically damaged (MD), mechanically damaged and application of regurgitant of cotton-fed Spodoptera exigua (MD + CR), and mechanically damaged and application of regurgitant of maize-fed S. exigua (MD + MR; n = 4–5). (A) Typical GC-MS chromatograms of HIPV from cotton plants 48 h after elicitation. The identities of the compounds are 1: 4-hexen-1-ol, acetate; 2: α-pinene; 3: β-myrcene; 4: β-ocimene; 5: DMNT; 6: Indole; and IS1 and IS2: internal standards (20 ng/μl), n-octane and nonyl acetate, respectively. (B) Average (±SE) of the most representative compounds emitted by cotton plants 48 h after elicitation. Different letters indicate significant differences between treatments (p < 0.05). (C) Average (±SE) of total amount of volatiles emitted by treated cotton plants 2, 24, and 48 h after elicitation. Different letters indicate significant differences between treatments within each time point. p values are given for treatments [generalized linear model (GLM; family, Gaussian)] followed by pairwise comparisons of Least Squares Means (LSMeans). ^**p < 0.01, ^***p < 0.001.