Effects Of Continuous Treatment With Methyl Jasmonate On Spodoptera Litura On Its Detoxification Ability And Growth And Development For Multiple Generations

In order to clarify the effects of methyl jasmonate（MeJA）on the growth and development and anti-defense ability of insects after multiple generations of continuous treatment,we took Spodoptera litura（Fabricius）as the research object to explore the effects of MeJA continuous treatment on the growth,development and detoxification ability of Spodoptera litura larvae for 6 generations,and analyze the changes of differential gene expression in the midgut and fatbody of F₀ and F₅ generation larvae by transcriptome sequencing.The results of growth and development showed that the mass gain of F₀ larvae treated by MeJA for 48 h,was significantly higher than that of the control by 21.82%.The mass gain of F₁,F₂,F₃ and F₅larvae treated with MeJA,was reduced by 22.83%,17.88%,29.71%and 17.97%respectively,compared with control;After MeJA treatment,Spodoptera litura pupa weights in F₀,F₂,F₃ and F₄generations were significantly higher than the control by 3.60%,8.09%,9.34%and7.74%respectively.Compared with the control group,the stage of 5th instars and pupal of the Spodoptera litura in the MeJA-treated group from the F₀ generation were significantly shortened,and the 6th instar stage was significantly prolonged.There was no significant change in the stages of pre-pupa and adult.The F₅ generation of Spodoptera litura had no significant difference in growth index compared with the control.The results of the detoxification ability study showed that MeJA had a certain promoted effect which Spodoptera litura larvae could reduced the poison of diet of xanthotoxin（0.05%）to itself,the mass gain of F₀ larvae was not significantly different from that of control,and the developmental period was prolonged.When F₅ generation larvae fed diet of xanthotoxin（0.1%）,the mass gain of MeJA-treated larvae was significantly lower than that of control by 20.77%.The developmental period was longer than the F₀ generation under the same treatment.F₀ generation of MeJA-treated the midgut of activity of glutathione-S-transferase,carboxylesterase and cytochrom P450 enzyme activities did not change significantly;The content of cytochrome P450enzyme,glutathione-S-transferase and carboxylesterase activity in the midgut and fatbody of the F₅ generation of MeJA-treated of Spodoptera litura showed an upward trend.Different generations of MeJA treatments did not significantly induce the expression of four P450 genes,CYP6B50,CYP6B47,CYP9A39 and CYP321B1,in the midgut and fatbody of Spodoptera litura.The results of transcriptome analysis showed that the F₀ generation involved 710 up-regulated and 952 down-regulated genes in the midgut,and 529 up-regulated and 438 down-regulated genes in the fatbody,respectively.In F₅ generation,the response genes were reduced,the up-regulated and down-regulated genes in the midgut were 245 and 291,respectively,and the up-regulated and down-regulated genes in the fatbody were 214 and 336,respectively.This study provides a theoretical basis for the rational use of plant defense signal substances to effectively control field pests,and is also conducive to in-depth understanding of plant-insect interactions mediated by plant defense signal substances.