Fig. 1.

Response of M. mediator naïve female parasitoids in a Y-tube olfactometer to the volatiles of A. thaliana Col-0 plants from different treatments. Treatments were control plants (C), rhizobacteria-treated plants (R), control plants infested with M. brassicae caterpillars (CM), or rhizobacteria-treated plants infested with M. brassicae caterpillars (RM). Nine to ten sets of plants were used per pair-wise comparison, each consisting of four plants per treatment. Bars represent the percentages of parasitoids that choose each of the two odor sources; N number of parasitoids that make the choice, NR number of nonresponsive parasitoids. Asterisks indicate significant differences (binomial test: *P < 0.05; ***P < 0.001; NS not significant)