Abstract: To clarify the roles of exogenous methyl jasmonate (MeJA) in controlling Bemisia tabaci adults on tomatoes, we measured nutrient content, secondary metabolite content and protein defense enzyme activity in tomato leaves under MeJA treatments in a pot experiment. The results showed that exogenous MeJA treatment reduced nutrient content in tomato leaves. The soluble sugar and protein contents were the lowest and the induction effect was the strongest under the treatment of 0.0225 mmol·L^-1 MeJA after five days. The exogenous MeJA treatment increased the secondary metabolites in tomato leaves, with the strongest induction effect and the highest concentrations of tannin and flavonoid being observed in tomato leaves under the MeJA treatment with application rate of 0.0225 mmol·L^-1 after five days. The exogenous MeJA enhanced the activity of defense enzymes (POD and PPO) in tomato leaves. With the extension of MeJA treatment time (0-14 days), the activity of defense enzymes showed a trend of increasing decreasingincreasing. The POD and PPO activities in tomato leaves were the highest and the induction effect was the strongest at the treatment of 0.0225 mmol·L^-1 MeJA after five days. Different concentrations of the exogenous MeJA application had different control effects on B. tabaci. After five days treatment with 0.0225 mmol·L^-1 MeJA, the best control effect on B. tabaci was observed, reaching 86.96%. In conclusion, the application of exogenous MeJA can increase the resistance of tomato to B. tabaci through reducing nutrient content, increasing secondary metabolite content and protein defense enzyme activity. Our results provide scientific basis for the prevention of B. tabaciin tomato planting and management.

Key words: methyl jasmonate, tomato, Bemisia tabac, induced insect resistance.