Identification Of Active Substances From Root Exudates Of Grafted Tomato And Their Effect On Resistance To Bacterial Wilt

Tomato wilt disease(Bacterial wilt)is a common soil-borne disease with strong infectivity and difficult to eradicate.It is the most effective method to control tomato bacterial wilt by grafting with disease-resistant rootstock.The results showed that the root exudates and rhizosphere microorganisms were closely related to the resistance of resistant rootstocks to bacterial wilt.In this study,based on the previous studies of the research group,two kinds of stock with high resistance to bacterial wilt(No.21,No.1)and tomato with high susceptibility to bacterial wilt(Fb)were used as materials.The root exudates of Ralstonia solanacearum inoculated with Ralstonia solanacearum were identified and analyzed by GC-MS.By using single and mixed active substances to fill in the high susceptibility bacterial wilt of tomato plants root treatment after vaccination blight fungus,dilution plate method is used to separate different processing of rhizosphere microorganisms,combined the technology of high flux measurement analysis the diversity of rhizosphere microorganisms,disease-resistant plant root secretion of root stock grafting mainly active substances to improve tomato bacterial wilt resistance mechanism,The results provided a theoretical basis for the use of active substances from root exudates to control bacterial wilt and a reference for the development of new plant agents to control bacterial wilt.The results are as follows:1.The root exudates of concentrated tomato rootstock grafted and self-grafted plants were collected and analyzed by GC-MS.The results showed that the relative contents of dimethyl phthalate(DP)and 2,6-di-tert-butyl p-methylphenol(BHT)in root exudates of resistant rootstock grafted plants were increased after inoculation with solanum solanum.The relative content of these two substances in root exudates of infected scion grafted from root decreased.Combined with the results of plate bacteriostatic experiment of solanacearum solanacearum,seed germination and seedling growth experiment of tomato,it is speculated that these two substances are related to tomato graft resistance to bacterial wilt.2.Single-factor and two-factor experiments with different concentrations of DP and BHT were designed to study the control effects of the two substances on tomato(Fb)bacterial wilt after self-root irrigation treatment.The results of single factor test showed that the incidence and disease index of plants treated with high concentration(1.0 and 2.0mmol/L)were significantly lower than those treated without root irrigation(CK),and 2.0mmol/L DP had the best effect,with the incidence and disease index of 57.7%and 48.9,respectively.The results of the two-factor test showed that the treatment of the two substances mixed in root irrigation had better disease control effect than that of the single active substance.The treatment with the concentration of 1.0mmol/L had the best disease control effect,with the incidence of bacterial wilt 46.7%and disease index 42.5,which were significantly lower than that of the single substance treatment.These results indicated that DP and BHT were two active substances that could resist bacterial wilt in root exudates of tomato grafted from disease-resistant rootstocks.3.Tomato(Fb)was treated by root irrigation with two kinds of active substances,and the rhizosphere matrix before and after inoculation of Solanum blight was sampled.The number of culturable microorganisms in the rhizosphere was determined by dilution plate method,and the effect of root irrigation treatment on the number of microorganisms in the rhizosphere was analyzed.Before inoculation,the numbers of rhizosphere bacteria and fungi treated by the two active substances were significantly lower than those treated by CK,and DP with 1.0mmol/L concentration was the lowest,with bacterial numbers 78.93×10~6cfu/g and fungi numbers 0.51×10~6cfu/g.After inoculation,the number of rhizosphere bacteria and actinomycetes treated by the two active substances was significantly lower than that of CK,and the number of rhizosphere fungi treated by DP was significantly increased compared with that before inoculation.After inoculation,the number of rhizosphere bacteria(53.6×10~6cfu/g)treated with 1.0mmol/L of the two active substances was significantly lower than that of CK.The results showed that the active substances from root exudates of resistant rootstocks could improve the resistance of tomato plants to bacterial wilt by inhibiting rhizosphere bacteria and regulating the number of rhizosphere fungi and actinomycetes.4.High-throughput sequencing results showed that the diversity and abundance of rhizosphere bacteria treated with the mixture of the two active substances at the concentration of 1.0mmol/L were significantly lower than those treated with CK before and after inoculation.The abundance of rhizosphere fungi was significantly higher than CK after inoculation.Microbial community composition and functional analysis showed that the rhizosphere bacterial substance synthesis and energy metabolism were more active in the mixture of two active substances than in other treatments,and the relative abundance of microorganisms antagonizing bacterial blight was higher than that of CK.The results indicated that the root exudates of resistant rootstocks could improve the resistance of grafted tomato to bacterial wilt by improving rhizosphere microenvironment and microbial metabolism.