Effects Of Root Exudates From Companion Cropping Plants On Root Knot Nematode And Resistance Of Tomato

Root knot disease,as one of the soil-borne diseases that harm vegetable production,has caused extremely serious consequences for tomato(Solanum lycopersicum)production in facility agricultural production.Due to people's attention to ecologically healthy agriculture and the pursuit of quality of vegetable product quality,ecologically safe agronomic root-knot nematode control technology has become a research hotspot.Intercropping is one of the best agronomic measures to prevent and control soil-borne diseases.Previous studies have found that potato onion can reduce tomato root-knot nematode diseases,but the mechanism is still unclear.Therefore,in this study,19 plants including potato onion(Allium cepa var.Agrogatum Don.),greenrrocery(Brassica campestris L.),mint(Mentha haplocalyx Briq.),fennel(Foeniculum vulgare Mill.)and tomatoes were used as test materials,for screening of associated plants that inhibit root-knot nematodes.To study the effect of companion cropping plant root exudates on the resistance of tomatoes and root knot nematodes by means of exogenously adding root exudates,in order to find out whether the disease of companion cropping plant root exudates was related to resistance of to matoes and root knot nematodes,so as to provide theoretical basis and technical support for the application of agronomic techniques for the prevention and control of root nematodes.The main findings are as follows:1.By using a pot experiment,4 kinds of companion cropping plants that significantly inhibited tomato root-knot nematodes were selected from 19 plants,including potato onion,greenrrocery,mint and fennel.2.The results of using exogenously added companion cropping plant root exudates showed that the patato onion and greengrocery root exudates have the strongest inhibitory effect on egg hatching of root-knot nematodes;mint and fennel root exudates significantly reduce the tendency of root-knot nematodes.Potato onion,greengrocery,mint an d fennel root exudates all have higher toxicity to root-knot nematodes.3.The results of analyzing the effects of adding root exudates of companion cropping plants on tomato resistance showed that the use of potato onion,greengrocery,mint and fennel root exudates significantly increased the root defense enzymes SOD,PPO and PAL,increased the total phenol and lignin content and reduced the MDA content in tomato roots.During the initial period(1d)of root-knot nematode inoculation,the relative expressi on levels of disease resistance-related proteins PR1,PPO genes and LOX genes increased significantly.4.Transcriptome analysis of tomato roots inoculated with nematodes after adding root exudates showed that genes related to phenylpropane synthesis pathw ay,endoplasmic reticulum protein processing pathway,MAPK signaling pathway pathway,plant hormone signal transduction pathway,and plant-pathogen interaction pathway were significantly enriched.Especially on 1 day after inoculation with nematodes,the e xpression of disease resistance protein(enzyme)genes,lignin synthesis-related genes,plant hormone metabolism and transcription factor-related genes were significantly up-regulated,indicating that tomato resistance to root-knot nematodes was enhanced.In summary,the mechanism by which the companion cropping plants potato onion,greengrocery,mint and fennel alleviate tomato root-knot nematode disease is as follows: on the one hand,the root exudates companion cropping plants inhibited the infection and reproduction of root-knot nematodes by inhibiting the hatching,affecting the chemotaxis.On the other hand,the companion cropping plants root exudates can inhibit the occurrence of root knot nematode diseases by inducing the activity of tomato root defe nse enzymes and upregulating the expression of disease-related genes.