Volatile chemical signals underlying the host plant preferences of Tuta absoluta.
The South American leaf miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), is a serious pest of tomato causing substantial annual economic losses at a global scale. Our study comprised choice and no-choice bioassays, aimed at understanding the preference of this oligophagous pest for a few selected solanaceous hosts (tomato, potato, eggplant, ashwagandha, black nightshade, wild tomato, tobacco, and datura), and the identification of the volatile cues that influence its host selection process. In choice assays, T. absoluta females preferred tomato for oviposition over all the other plants, whereas ashwagandha, tobacco, and datura were the least preferred; on datura zero eggs were laid. A similar trend was observed in the subsequent number of larval mines formed. The moth's preference for host plants of the genus Solanum was quite evident in both the choice and no-choice assays. Tomato plant volatiles were found to be more attractive to the female moths in single- and dual-choice olfactometer assays. In electroantennographic bioassays, the mean depolarization was significant for tomato, potato, ashwagandha, and eggplant compared to empty air and honey. In total 76 volatile compounds were identified in the GC-MS analysis across the eight previously selected host-plant headspace samples. Principal component analysis revealed that 1-fluorododecane and p-quinone mainly contributed to the observed variation among the host plant volatiles. Of all the host plants, tomato, wild tomato, and tobacco were found to share similarities with respect to volatile cues, whereas ashwagandha, eggplant, and datura were found to be closely related. The other two hosts, potato and black nightshade, had fewer volatiles in common. Volatile cues, namely p-quinone, 2-carene, δ-curcumene, and 1,2-diethylbenzene, in tomato could serve as oviposition stimulants to T. absoluta, whereas the presence of 1-fluorododecane in host plants such as datura, eggplant, ashwagandha, and black nightshade, might have deterred T. absoluta from ovipositing. 1-Fluorododecane was found to be completely absent in tomato.