Effects Of Silicon In Rice,Oryza Sativa On Defense Against Rice Leaf Folder,Cnaphalocrocis Medinalis

The influence of silicon on volatile emission of rice(TN1),Oryza sativa and oviposition preference of female adults and orientation behavior of larvae of rice leaf folder(RLF),Cnaphalocrocis medinalis(Guenee)was investigated.The results are as follows.The rice plants were grown by water culture with the silicon content of 600 mg/L or 0 mg/L in the nutrient solution.The silicon content in the rice leaf was 6137.10±328.66mg/kg with silicon treatment or 51.45±26,52mg/kg without silicon treatment.Cage assays were used to compare the oviposition behaviors of RLFs among rice plants subjected to different treatments.The results showed that C.medinalis adults did not significantly prefer silicon-treated or untreated rice in cages.Upon plant infestation by larvae of C.medinalis,adults significantly preferred rice with silicon treatment compared with rice with non-silicon treatment.However,adults did not significantly prefer silicon-treated rice or untreated rice via a Y-tube olfactometer.However,the average numbers of eggs laid by C.medinalis on the wall of the Y-tube were significantly higher in the silicon-treated plants than in the untreated plants.There was no significant difference regarding plant health among the different silicon treatments.The orientation behavior of the 3rd-instar larvae of C.medinalis to the volatiles emitted from rice plants was studied using a Y-tube olfactometer.The treatments were as follows:1)group of healthy plants:silicon-treated plant(SP)vs.clean air,non-silicon-treated plant(NSP)vs.clean air,SP vs.NSP;2)group of C.medinalis larvae-damaged plants:SP vs.NSP.The results showed that the larvae significantly preferred the volatiles from all rice plants rather than air.There was no significant change in the orientation selections of larvae to the volatiles from differently treated rice plants.The GC-MS analysis showed that volatile compounds released from the differently treated plants included hydrocarbon alkyls,ketones,aldehydes,alkenes,aromatic hydrocarbon and other compounds.The treatments consisted of a control;a treatment with silicon;plant infestation with C.medinalis larvae;a treatment with silicon + plant infestation with C.medinalis larvae.The volatile constituents varied among the different treatments.Methyl salicylate was just present in volatiles from the silicon-treated plants and infested previously with larvae.In summary,silicon had no significant effects on the oviposition preference of C.medinalis adults or the orientation behavior of the 3rd-instar larvae of C.medinalis in both rice plants with and without infestation by C.medinalis larvae.Regarding the infested plants,silicon had significant effects on the oviposition behavior of C.medinalis and plant volatile release including the compounds and emission.These differences may inhibit the oviposition of female adults.