Celery Root Exudates Induced Anti-Insect Defense Responses In Tomato And Cucumber And Preliminary Screening Of Inducing Factors

Bemisia tabaci has been recognized as the world’s second largest pest by FAO.It currently hosts up to 600 species and spreads more than 300 viral diseases,causing huge losses to horticultural and field crops and even failing to harvest in serious cases.B.tabaci occurs all year round on facility vegetables.At present,the application of chemical pesticides is the main means to control B.tabaci,which leads to the increasing resistance of B.tabaci,causing serious environmental pollution and food safety problems.There is an urgent need to find a green,effective and safe approach to prevention and treatment.Root exudates are compounds released from plant roots into the environment and are also one of the few sources of elicitors that can induce defensive responses in other plants.Researches on root exudates mainly focus on inducing disease resistance and weeding,while there are few reports on inducing insect resistance.Celery plays an important role in green control.In this paper,the anti-insect defense response induced by celery root exudates in tomato and cucumber against B.tabaci was investigated,and the bioactive components in celery root exudates were initially identified and screened out,providing a new idea for green control of B.tabaci.The main research results are as follows:1.Celery root exudates significantly improved the resistance of tomato and cucumber to B.tabaciCompared with CK,the number of insect larvae,the number of eggs and the survival rate of B.tabaci on tomato and cucumber leaves that treated with celery root exudatesd ecreased by 63.14%and 63.60%,47.81%and 49.33%13.68%and 14.46%.The developmental period of B.tabaci was extended by 5 and 6 days.The odor selection rate of the two plants in the treatment group also decreased by 49.20%and 42.00%,the above indexes were significantly different from CK.Therefore,celery root exudates can induce tomato and cucumber to produce anti-insect defense response against B.tabaci.2.Celery root exudates can significantly increase the contents of antibiotes,volatiles and endogenous hormones in cucumber and tomatoCompared with CK,the contents of soluble sugar and protein in tomato and cucumber treated with celery root exudates increased by 91.08%and 59.62%,41.73%and 56.65%,but the contents of amino acid decreased by 83.69%and 95.05%.Phenolic and flavonoids were increased by 52.81%and 57.14%,62.15%and 75.24%.The activity of POD,SOD and PPO enzymes increased by 76.63%and 77.14%,31.54%and 37.90%,34.82%and 222.46%.The above indexes were significantly different from CK.It is speculated that celery root exudates can enhance the resistance of cucumber and tomato to B.tabaci.Compared with the control,the content of α-pinene,which had repellent effects on B.tabaci,increased by 177.27%and 80.45%,respectively.The content of volatiles 3-hexene-1-ol with attractant effect on B.tabaci decreased by 207.69%compared with the control.JA in treatment group increased by 165.76%,113.04%,76.47%and 123.52%compared with CK in control group.The above indexes were significantly different from CK.It is likely that by stimulating JA and ABA related immune pathways in plants,it promotes the production of nutrients and increases the content of resistant substances,so as to increase the content of insect resistant volatiles and achieve the effect of insect resistance.3.Identification of bioactive substances in celery root exudates and verification of their candidate factors for inducing insect resistanceThe active substances in celery root exudates were extracted by ethyl acetate,and then identified by GC-MS.Based on the analysis of color mass spectrometry and the literature,five candidate bioactive substances were preliminarily screened out,which were methyl benzoate,2,4-di-tert-butylphenol,methyl palmitate,dibutyl phthalate and methyl stearate.The relative quantitative and absolute quantitative analyses of the above-mentioned substances were carried out.Tomato seedlings were treated with different concentrations of the above 5 substances,and it was found that the insect population and egg production in 7mg/L methyl benzoate and 5mg/L methyl stearate treatment groups were reduced by 38.93%and 130.07%,116.87%and 149.80%compared with CK.