Studies On The Screening Of Fusarium Wilt-resistant Tomato Rootstock And Mechanism Of Grafted-seedlings Disease Resistance

Tomato(Solanum lycopersicum L.)is an annual or perennial herbaceous plant of lycopersicum in Solanaceae,with the extension of the years of protected cultivation,the occurrence of tomato wilt is increasing year by year.As an effective way to alleviate soil borne diseases,grafting is widely used in the production of melon and eggplant fruit vegetables,but the resistance of rootstock is not the same,therefore,it is of great theoretical and practical significance for the cultivation and production of tomato to select varieties with high resistance to Fusarium wilt,get the metabolic indexes related to Fusarium wilt resistance,and research the disease resistance mechanism of grafted tomato.In this experiment,the pathogen was isolated and purified from the wilt plants collected in Dingxing and Feixiang with large cultivation area of tomato.The pathogen was identified by morphological and molecular biological methods.Two strains of Dingxing(D strain)and Feixiang(F strain)were inoculated to 10 tomato rootstocks by root soaking method to evaluate the disease resistance;three resistant rootstocks and three susceptible cultivars were selected as the experimental materials.Strain D and strain F were inoculated with root soaking method to explore the resistance difference of different resistant cultivars after inoculating different strains of Fusarium wilt,and the change rule of active oxygen metabolism and phenylpropane metabolism pathway of leaves,so as to obtain the relevant indexes of tomato Fusarium wilt resistance;The resistant variety TMS150(R)and the susceptible variety FUYOU II(S)were used as the experimental materials,four different grafting combinations were set up,and Fstrain was inoculated by root soaking method,so as to clarify the resistance of the grafted plants,the changes of active oxygen metabolism and phenylpropane metabolism pathway in leaves,and to explore the mechanism of resistance to Fusarium wilt of grafted tomato.The main results are as follows:(1)The isolates were identified by morphological and molecular biological methods.The results showed that the isolates from Dingxing and Feixiang were Fusarium oxysporum,PCR amplification was carried out with physiological races-specific primers of Fusarium oxysporum f.sp.lycopersici,and it was proved that both strains were Fusarium oxysporum f.sp.lycopersici races 3,three varieties of high resistance rootstocks and seven varieties of general resistance rootstocks were screened.(2)After inoculation of 3 disease-resistant rootstock varieties and 3 diseasesusceptible varieties with bacteria D and F,the disease index was calculated to determine the metabolic pathways of reactive oxygen speciesand phenylpropane-related metabolic pathways,and the indexes related to the resistance of tomato fusarium wilt were screened.The results showed that the resistance of rootstock varieties to Fusarium wilt was significantly higher than the cultivated varieties;the activities of superoxide dismutase(SOD)in the leaves of susceptible varieties were decreased after inoculation with D and F,but the changes of different varieties are not significant compared with the control treatment;the enzymatic activities of peroxidase(POD)in susceptible varieties were significantly higher than those of resistant varieties,but the activities of catalase(CAT)in resistant varieties were significantly higher than susceptible varieties;the production rate of superoxide anion and the content of hydrogen peroxide(H2O2)in resistant varieties increased for a short time and then adjusted to the normal level quickly,the rate and content of susceptible varieties are still relatively large in the later period;the PPO activity of susceptible varieties was significantly higher than those resistant varieties,and the lignin content was lower than that of resistant varieties.The results showed that the resistance of tomato rootstock varieties to Fusarium wilt was significantly higher than the cultivated varieties,and the resistance was closely related to the pathway of active oxygen metabolism and phenylpropane metabolism,among which CAT activity,O2·-production rate,H2O2 content,PPO activity and lignin content could be the key indicators of resistance evaluation.(3)The most stable TMS150 with disease resistance(R)and and infected FUYOU I I(S)varieties,set up different grafting combination(S/R,R/S,S/S,R/R),and after inoculation of bacteria,through statistical index,determination of active oxygen metabolism pathway and benzene propane metabolic pathways of the relevant indicators,and unarmed slice observation,the grafting of tomato blight resistance mechanism is obtained.The results showed the disease index of the combinations of disease-resistant varieties as rootstock was lower than that of the combinations of susceptible varieties as rootstock.The activities of SOD in the leaves of the grafted combinations showed no significant change compared with the control treatment;the activity of POD in the selfgrafting combination was higher than that in the normal grafting combination,the CAT activity of S/R grafted stock was significantly higher than that of susceptible stock,normal grafting combination O2·-producing rate and the content of H2O2 with transient rise quickly adjust to normal levels,cultivars of the grafting rate and content in the later still larger;In addition to the lignin content in the phenylpropane metabolic pathway,there was no significant correlation between other indexes and graft disease resistance.The result show,after grafting plant through the activity of CAT,reduce O2·-produce rate and H2O2 content,improve the content of lignin to resist diseases,improve the grafting plant blight resistance.To sum up,the pathogen isolated from Dingxing and Feixiang were Fusarium oxysporum f.sp.lycopersici races 3,and three high resistant rootstocks and seven resistant rootstocks were obtained,the physiological and metabolic changes of tomato varieties with different resistances after inoculation were different,the CAT activity and O2·-produce rate,H2O2 content,PPO activity,lignin content,five indexes exist significant differences in the sense of resistance varieties can be used as tomato blight resistance index.Grafting significantly improved the disease resistance of the affected varieties,with the resistance of R/R>S/R>R/S>S/S,and the S/R combination could improve the disease resistance of the affected varieties through the metabolic pathways of reactive oxygen species and phenylpropanes.