Ms. Ashageru Tsege

Tomatoes (Solanum lycopersicum L.) are one of the most cultivated vegetable used for fresh consumption around the world, which greatly suffer from yield loss due to pest damage. One tomato pest is the two-spotted spider mite (TSSM; Tetranychus urticae Koch). Recently, we had shown that volatile mono- and sesquiterpenoid compounds are negatively correlated with TSSM in two selected tomato cultivars. However, a validation of these findings has yet to be conducted. We studied the role of tomato monoterpenoids in defense mechanisms against TSSM using odoless-2 (od-2), which develops defective glandular trichomes, and as a result affects volatile molecule profiles. To detect these compounds, we used solid phase microextraction, and found a significant difference of volatiles between od-2 and wildtype. Moreover, four monoterpenoids were significantly different between wildtype infested and uninfested plants. An olfactory choice bioassay indicated that TSSMs were significantly attracted to the od-2 compared to the wildtype, and the TSSM’s predator mite Phytoseiulus persimilis was significantly attracted to the od-2 infested by TSSMs compere to wildtype infested. To study whether the TSSMs themselves have a typical smell, we collected mites from infested bean and tomato plants. We found eleven volatiles that are highly accumulated in TSSMs themselves, among which one is an unidentified volatile that is common to all mites collected from all plants, while the others were detected in both TSSMs and infested plants in a similar manner. This study exposed four monoterpenoids that might play an important role in determining tomato plant resistance to pests which can advise the invention of new tomato cultivars resistant against TSSMs.