| Since the commercialization of Bt cotton in 1997,damages of Helicoverpa armigera to cotton plants have been repressed,in which had been the main herbivory pest in cotton field.Subsequently,the loss of cotton caused by other secondary herbivores,such as mirids,cotton aphids has been more serious.Developping innovative strategies with broad spectrums against cotton pests can provide new proposals for breeding of cotton,in which harboring resistance to herbivores.Plants attacked by herbivore can synthesize many secondary metabolites to improve their resistance toward pests,in which includes some volatile secondary metabolites HIPVs?Herbivore-induced plant volatiles,HIPVs?.These HIPVs were demonstrated functioning as important roles in plant direct and indirect defense,such as terpenes,volatile indoles,fatty acid derivatives,green leaf volatiles,and nitrogen-containing compounds.?E?-?-caryophyllene is a volatile sesquiterpene and can protect rice and corn from herbivores by indirect defense,but its specific functions and application values in cotton defense requires more testimonies based on studies.To investigate the specific functions of?E?-?-caryophyllene synthase gene GhTPS1 in cotton defense and enrich the present strateges of cotton against pests,this study introduced GhTPS1 into cotton plants and performed a seriese of researches upon the behavioral impacts of GhTPS1transgenic cotton toward cotton pests and their natural parasitoids,based on previous works.The following progresses have been obtained:?1?Four transgenic lines were confirmed by genetically transform and PCR identification,including L18,L46,L48 and L88.The GhTPS1 expressions in transgenic L18 and L46 lines were 3-5-fold higher than in R15 plants.?2?Compared with the amount of?E?-?-caryophyllene producted by R15 plants(52–100 ng·plant-1·6 h-1),the transgenic L18 and L46 lines emitted significantly more?E?-?-caryophyllene(358–363 ng·plant-1·6 h-1)in laboratory.In field,the amount of?E?-?-caryophyllene emitted by L18 and L46 plants are still higher than R15 plants.?3?In laboratory,L18 and L46 plants reduced the spawn of Helicoverpa armigera and repelled Apolygus lucorum and Aphis gossypii.Correspondingly,the open-field trials show that L18 and L46 plants also reduced the spawn of Helicoverpa armigera and repelled Apolygus lucorum.In addition,Adelphocoris suturalis was also repelled by L18 and L46 plants in field investigation.?4?Behavioral trials in laboratory,also show that indirect defense of L18 and L46 plants were strengthen by attracting the parasitoids Peristenus spretus and Aphidius gifuensis,both of them are the natural enemies of Apolygus lucorum and Aphis gossypii respectively.However,the natural parasitoid of Helicoverpa armigera,Microplitis mediator failed to response toward the odors source,neither transgenic plants nor R15.Taken together,improving the emissions of?E?-?-caryophyllene by transforming GhTPS1 gene into cotton variety R15,affects the behavior of the above cotton pests and their natural parasitoids,except Microplitis mediator.As a result,the resistance of L18 and L46 plants to pests increased.This study extends the trophic interaction net among cotton-pest-parasitoid mediated by plant volatiles.Moreover,this research also provides evidence for integrated pest management?IPM?using plant volatiles in cotton.The transgenic lines L18 and L46 are innovative transgenic cotton variety,in which can be used for the subsequential breeding of cotton against herbivory pests. |
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