Study On The Physiological Mechanism Of Resistance To Grafted Seedlings Affected By The Interaction Between Disease-resistant Rootstock And Sensitive Scions Of Eggplant Bacterial Wilt

Eggplant bacterial wilt is a soil-borne disease caused by Ralstonia solanacearum E.F.Smith.Grafting with disease-resistant rootstocks is an effective method for controlling bacterial wilt.In order to to explore the physiological mechanism of resistance to bacterial wilt in eggplant grafted seedlings,this study used high resistance to bacterial wilt rootstock S21 and high-sensibility bacterial wilt scion Rf as experimental materials.Constructing the grafting combination of rootstock and spike(Rf/S21),rootstock grafting combination(S21/S21)and scionling grafting combination(Rf/Rf),we infected the factors(Exopolysaccharides and cell wall degrading enzymes)from the plant under the stress conditions of Ralstonia solanacearum Exopolysaccharides and cell wall degrading enzymes,and disease-resistant defensive factors(reactive oxygen scavenging systems)were used to study the physiological mechanism of the effects of rootstock-spike interactions on the disease resistance of grafted seedlings.The main findings are as follows:1.Seedling root-immersion root inoculation method was used to identify the resistance of different combinations of grafted seedlings to bacterial wilt,and S21/S21 showed high resistance(HR)and Rf/S21 showed resistance to disease(R),and Rf/Rf showed high sensation(HS),The incidence and disease index of grafted grafts of Rf/S21 were higher than that of S21/S21.The results showed that disease-resistant rootstocks significantly increased the disease resistance of grafted seedlings,but the susceptible scions affected the disease resistance of grafted seedlings through the interaction between the rootstock and ear-sprouts,resulting in a resistance-reducing effect on the rootstocks.2.After inoculation with R.solanacearum,the growth rate in the dry fresh weight of the Rf/S21 stems,and roots of the grafting seedlings was significantly lower than that of S21/S21;the root length,root surface area,The crude stem growth rate of the rootstock was significantly lower than that of S21/S21,which indicated that the the susceptible scion has an inhibitory effect on stem growth and root growth of rootstock.3.After inoculation with R.solanacearum,The contents of extracellular polysaccharides in leaves,scion stems,rootstock stems and roots of Rf/S21 were higher than those of S21/S21.In the early stage of infestation,the growth rates of PMG,PGTE,PMTE,PG activity of Rf/S21 were higher than that of S21/S21.In the late stage of infection,The growth rate of Cx activity in Rf/S21 was significantly higher than that of S21/S21.This shows that Rf/S21 have higher accumulation of extracellular polysaccharides than S21/S21,and the activity of cell wall degrading enzymes is enhanced.PMG,PGTE,PMTE,and PG act at the early stage of the disease,and Cx acts at the later stage of the disease.4.After inoculation with R.solanacearum,The content of hydrogen peroxide in leaves,scion stems,rootstock stems and roots of grafted seedlings was higher than that of rootstocks grafted from rootstocks.At 7 d and 28 d after inoculation,the production rate of superoxide anion(O2-)in leaves,scion stems,rootstock stems,and roots of grafted shoots was higher than that of grafted rootstocks.It indicated that the amount of active oxygen accumulation in grafted plants was higher than that of rootstock grafted grafts,and the tolerance to R.solanacearum grafting was weaker than that of grafted rootstocks.5.After inoculation with R.solanacearum,The growth rate of SOD and POD activities in grafted seedlings of rootstocks was significantly lower than.that of grafted rootstocks.After 21 days of inoculation,the growth rate of PPO activity in the stem and roots of rootstocks was lower than that of rootstocks grafted from rootstocks,while CAT,APX,and GR has a relatively high growth rate of enzyme activity.It showed that the susceptible scions inhibited the effective removal of reactive oxygen species from the active oxygen scavenging system of grafted plants,resulting in a reduction in plant disease resistance.Based on the above results,susceptible scions can cause excessive exosome secretion of exopolysaccharides from the grafted plants,enhanced activity of cell wall degrading enzymes,inhibition of stem and root growth of grafted rootstocks,and accelerated accumulation of reactive oxygen species in grafted rootstocks.Suppresses the effective removal of reactive oxygen species from grafted plants and results in tissue necrosis,resulting in a reduction in plant disease resistance.