Effect Of Indole And Indole Produced Bacteria On The Infection Process Of Meloidogyne Incognita

Plant parasitic nematodes have now become the second largest disease after fungi,with highly sensitive chemoreceptors.Root-knot nematodes sense and recognize chemical signals released by plant roots or rhizosphere microorganisms,and locate the host to complete the infestation process.Therefore,allelochemicals can be used to interfere with the process of host seeking to control root-knot nematodes.In the previous study,it was found that Meloidogyne incognita had a chemotaxis activity to indole,and the signaling pathway of M.incognita sensing indole was found.In order to study the effect of indole in the infection process of M.incognita,the indolesensing genes of M.incognita were interfered and the effects of bacteria and their product indole on tomato root infection were studied in pot experiment.Through the screening of the nematocidal activity and the indole production of the strain fermentation broth,a total of five strains were screened for twin-pot assay.The five strains are mainly divided into three types:with nematocidal activity and indoleproducing strains(BX and B13,J-1),with nematocidal activity and non-indoleproducing strain(1-50),and non-nematocidal activity and indole-producing strain(OP50).At the same time,based on the previous study,Mi-odr-1 and Mi-str-193 genes were selected for RNA interference.After RNAi of the gene Mi-odr-1,chemotaxis to indole of nematodes were significant decreased.Finally,gene Mi-odr-1 was selected for RNA interference and used as the infection nematodes in pot experiment.Results of using of the disturbed M.incognita and five experimental strains in twin-pot assay were found that:Inoculation of wild-type nematodes,the number of the galls on the side of the OP50 fermentation broth increased significantly compared with the side of blank control,and the number of galls increased by 20.10%.While inoculating with wild-type nematodes,the number of galls on the side of addition OP50 have no significant difference compared with the one on the side of blank control.The results indicated that indole played an attractive role in the process of M.incognita infesting tomatoes and increase the rate of infection.The addition of four strains,whether the nematodes were RNA interference or not,the number of galls decreased significantly at 45 days compared with the LB control group.And in the group of indole-producing strains BX and B13,the number of galls on the side of the added fermentation broth was less than that of the side without fermentation broth,indicating that although indole can attract nematodes,the nematocidal activity of the strain leads to a decrease in infection.Inoculation with wildtype nematodes,the number of galls was reduced by 10.68%and 23.38%after adding fermentation broth of BX and B13 strains,respectively.Inoculated with RNAi nematodes,the number of galls was reduced by 19.85%and 40.94%after adding fermentation broth of BX and B13 strains,respectively.However,there was no significant difference in the number of galls on both sides of the double channel between less indole-producing strain J-1 and non-indole-producing strain 1-50.At the same time,literatures reported that many indole derivatives play an important role in plant growth and defense against pests and diseases.Therefore,attraction activity of four indole derivatives(indoleacetic acid,indolebutyric acid,3methylindole and 3-indole formaldehyde)on M.incognita was further studied in this paper.Chemotaxis of M.incognita has a concentration dependence on these four compounds.Six genes of nematode in indole pathway have different degrees of upregulation while attracted by these copounds.After the RNA interference,chemotaxis of M.incognita to indoleacetic acid,indolebutyric acid and 3-methylindole have varied decreasingThe results showed that indoleacetic acid,indolebutyric acid,and 3methylindole may have similar perceptual pathways with indole.The above results show interaction among tomato,rhizosphere bacteria and M.incognita:the attracting compound indole produced by the rhizosphere strain can attract M.incognita to gather,and the efficient of its toxic killing effect could be promoted,and a decrease in the number of galls that are eventually formed.The control efficiency of indole-producing strain was higher than that of non-indole-producing nematocidal strain,they had the potential to improve the efficiency to control root-knot nematode disease.This paper focused on the role of indole and indole-producing bacteria in the process of M.incognita infestation of tomato roots,provides data for the chemotactic behavior of root-knot nematodes in the pre-parasitic stage of plants,and provides new clues and control strategies for the biological control of root-knot nematodes.