Non-volatile intact indole glucosinolates are host recognition cues for ovipositing Plutella xylostella

The diamondback moth (Plutella xylostella), a crucifer-specialist pest, has been documented to employ glucosinolates as host recognition cues for oviposition. Through the use of mutant Arabidopsis thaliana plants, we investigated the role of specific classes of glucosinolates in the signaling of oviposition by P. xylostella in vivo. Indole glucosinolate production in A. thaliana was found to be crucial in attracting oviposition. Additionally, indole glucosinolates functioned as oviposition cues only when in their intact form. 4-Methoxy-indol-3-ylmethylglucosinolate was implicated as an especially strong oviposition attractant in vitro, suggesting that indole glucosinolate secondary structure may play a role in P. xylostella host recognition as well. Aliphatic glucosinolate-derived breakdown products were found to attract P. xylostella, but only after damage or in the absence of indole glucosinolates. Furthermore, mutant plants lacking both intact indole glucosinolates and aliphatic glucosinolate breakdown products exhibited decreased oviposition attractiveness beyond that of the progenitor mutants lacking either component of the glucosinolate-myrosinase system. Therefore, we conclude that nonvolatile indole glucosinolates and volatile aliphatic glucosinolate breakdown products both appear to play important roles as host recognition cues for P. xylostella oviposition.