Effects of active substances secreted from roots of two grafted tomato plants on tomato bacterial wilt and rhizosphere microorganisms

【Objective】The purpose of this study was to identify and analyze the root exudates of grafted tomato，and to study the effect of its active components on tomato resistance to bacterial wilt，bacterial wilt bacteria in tomato and the number of rhizosphere microorganisms，so as to provide new ideas for the control of tomato bacterial wilt.【Method】Tomato varieties with high susceptibility to bacterial wilt disease，Fanbei（Fb），tomato rootstocks with high resistance to bacterial wilt，Fanzhen No.1（No.1）and Qiezhen No.21（No.21）were used as experimental materials. There were five grafting combinations，which wereself-root grafting seedling（Fb/Fb），rootstock grafting（Fb/No.1，Fb/No.21）and rootstock self-grafting（No.1/No.1，No.21/No.21）. Gas chromatography-mass spectrometry（GC-MS）was used to identify and analyze the root exudates before and after inoculation of Ralstonia solanacearum in grafted tomatoes. Hypersusceptible tomatoes roots were treated with selected active substances then were inoculated by R. solanacearum. The dilution plate method was used to isolate and determine the amount of R. solanacearum and rhizosphere microorganisms in tomato and rhizosphere.【Result】Two active substances，dimethyl phthalate（DP）and 2,6-di-tert-butyl-p-cresol（BHT），were identified and screened from the root exudates of grafted tomato，among which 1.0 mmol/L DP and 1.0 mmol/L BHT mixed root irrigation treatment had the best disease resistance effect，which significantly reduced the incidence and disease index of bacterial wilt in highly susceptible tomato to 46.7% and 42.5（P<0.05，the same below）. The two active substances in the root irrigation treatment significantly decreased the number of rhizosphere microorganisms and bacteria， both could reduce the number of rhizosphere fungi，in which BHT inhibition was more effective. They could both significantly inhibited number of fungiin the early stage of disease，and DP had better effects than BHT.【Conclusion】Two active substances，DP and BHT，are screened out，which can improve the resistance of tomato to bacterial wilt by improving the rhizosphere microenvironment and reducing the number of bacterial wilt bacteria in the plant and in the rhizosphere.