| Global crop production is lost by 20-40% annually due to insect pest attack.At present,the agricultural pest control mainly relies on chemical pesticides,while their overapplication has caused 64% of the worldwide agricultural land(approximately 24.5 million square kilometers)with pesticide pollution,resulting in significant threats to the environments,biodiversity,and human health.With the development of nanotechnology,various types of engineering nanomaterials(ENMs)have been used to pest control.Among these ENMs,nanosilicon,due to its low ecological risk,is expected to become a green and safe tool for controlling crop pests compared to other metal based ENMs.Currently,increasing studies have shown that nanosilicon could increase plant resistance against biotic and abiotic stresses,while the underlying mechanism of nanosilicon-mediated plant resistance to insect herbivores remains unknown.Therefore,in order to promote the application of nanosilicon in the field of pest control,this work firstly conducting a meta-analysis across 51 global published studies on nanosilicon mediating plants to resist biotic and abiotic stresses,and identified the key influencing factors of nanosilicon regulating plant resistance against stresses.Secondly,a typical nanosilicon-silicon quantum dots(SQ),as well as the typical chewing pest white grubs(Holotrichia oblita,belowground pests)and amyworms(Mythimna separate,aboveground pests)were used to elucidate the control effect and mechanism of SQ on crop pests.The main findings are as follows:(1)Meta-analysis indicated that under biotic and abiotic stress conditions,nanosilicon could significantly improve the antioxidant enzyme activity by 16.3%,the content of antioxidant metabolites by 15.2%,and upregulated the expression of defense related genes by178.2%,thus reducing oxidative stress by 24.0%,and ultimately increasing the plant biomass and yield by 26.6% and 29.8%,respectively.Random forest analysis showed that the effect of nanosilicon on alleviating plant oxidative stress depended on its application dose and duration.Particularly,application with 10-100 ppm nanosilicon for 30-60 days significantly reduced plant oxidative stress.In addition,soil-applied nanosilicon significantly more upregulated the expression of defense related genes than leaf exposure.(2)In the “soil-applied SQ-mediated cherry radish resist H.oblita” experiment,soilapplied 50 mg/kg SQ was the optimal dose for increasing taproot biomass and leaf chlorophyll content in cherry radish under H.oblita stress.Compared with commercial pesticides(imidacloprid)and traditional Si fertilizers(sodium silicate),soil-applied 50 mg/kg SQ has the most robust control effect on H.oblita,significantly inhibiting the growth of H.oblita larvae by 38.0%.Mechanistically,soil-applied 50 mg/kg SQ not only enhanced the mechanical strength of taproot tissue via promoting radish taproot Si deposition and lignin accumulation,but also induced radish chemical defense H.oblita via activating phytohormone contents(jasmonic acid and salicylic acid)to increase the contents of specific chemical insect-resistance substance(aucubin,gluconasturtiin and pipecolic acid).Additionally,SQ increased taproot antioxidant enzyme(SOD and POD)activities and antioxidant metabolites(flavonoids and glutathione)contents under white grub attack,thereby alleviating the oxidative stress caused by H.oblita feeding.Moreover,microbial 16 S r RNA sequencing analysis showed that soilapplied SQ shaped a healthy rhizosphere microenvironment for the growth and defense of cherry radish via enriching plant growth promoting,stress resistance and nitrogen cycling microbes(e.g.,Acidobactera,Nitrospirae,Verrucomicrobia,Armatimonadetes,Ramlibacter and Nitrospira).(3)In the “soil-applied SQ-mediated maize resist M.separate” experiment,the effect of soil-applied SQ-mediated maize resistance against M.separate was in a dose-dependent manner,and particularly 50 mg/kg SQ resulted in the strongest resistance to M.separate than traditional Si fertilizer,significantly inhibiting the growth of M.separate by 21.0%.On the one hand,SQ significantly increased maize leaf Si deposition and lignin accumulation by upregulating the expression of Si channel protein genes(Lsi1,Lsi2,and Lsi6)and lignin biosynthesis pathway gene,thus enhanced the mechanical strength of maize leaves and reduced the feeding of M.separate.On the other hand,soil-applied 50 mg/kg SQ promote the accumulation of BXs and their degradation products via upregulating the expression involved in downstream BXs biosynthesis pathway(Bx6,Bx7,Bx10/11,Bx12,Bx13,Bx14 and Glu1),enhancing the resistance of maize leaves to M.separate.In addition,soil application of 50 mg/kg SQ could upregulate the expression of antioxidant enzyme genes(SOD,POD,and CAT)and the accumulation of flavonoid antioxidant metabolites in maize leaves,thereby eliminated ROS such as hydrogen peroxide free radicals and superoxide anion free radicals.Therefore,compared to traditional Si fertilizer,SQ more effectively reduced oxidative stress caused by armyworm feeding.Field experiments showed that soil addition of 50 mg/kg SQ increased the maize cob weight,grain weight per cob,number of per cob,and 100-grain weight by 28.7%,40.8%,18.6%,and 26.5%,respectively.Taken together,SQ are more effective than traditional Si fertilizers in improving maize yield and resistance against herbivores.This study not only clarified the alleviating effect and key influencing factors of siliconbased ENMs on plant oxidative stress based on meta-analysis,but also manipulative experiments indicated that soil-applied SQ improved the crops resistance against aboveground and belowground chewing herbivores by simultaneously activating the physical and chemical defenses.In addition,field experiments further showed that compared to traditional Si fertilizer and commercial pesticides,soil-applied SQ had better control effects on crop pests.In summary,these results contribute to the use of silicon-based ENMs with high environmental safety as alternatives to traditional agrochemicals for crop pest control and achieving agricultural soil sustainability. |
