The Effects Of DSE Inoculation On The Disease-resistance And Heavy Metal-tolerance Of Tomato

Dark septate endophytes (DSEs) prevalently colonize in the roots of various plants, and presumably play similar ecological functions as mycorrhizal fungi, for example, promoting host plant’s nutrient absorption, stress tolerance, disease control and etc. In the current study, tomato was inoculated with DSE or not under the biotic or abiotic stresses caused by the inoculation of Fusarium oxysporum or different concentrations of Cd/Zn supplements for 50 days. The shoot height, biomass, and the heavy metal accumulation in the ground and underground parts of tomatoes were determined, and the activities of antioxidant enzymes and the content of antioxidants were also analyzed to explore the effects of inoculation with DSE on the resistance and heavy metal tolerance of tomatoes. Results are as follow:1. The two DSE strains selected in the experiment successfully colonized in the roots of tomatoes. Typical dark and septate hyphae can be seen under microscope, and the rate of DSE colonization in tomatoes increased with the elevated concentrations of heavy metals and inoculation of the pathogen. The colonization rate of the Z48 ranged frome 8.75% to 21.5%,10.5%～20.75% for K36.2. The growth and the biomass of tomatoes were significantly promoted by inoculation with DSE after 50 days. The shoot length of tomato inoculated with K36 strain increased 1.37-fold in comparison of the non-inoculated control, and 1.41-fold for Z48 strain. The tomato shoot biomass (dry weight) were 1.53 and 1.68 times as the CK group, and the root biomasses were 1.46 and 2.46 times when inoculated with K36 and Z48, respectively. The growth of the tomatoes was also enhanced by colonization of DSE under the heavey metal stress.3. To a certain level, tomatoes could absorb and accumulate heavy metals under low metal stress and the majorityaccumulated in the roots. With the increase of the concentrations of the heavy metals (zinc, Zn and cadium, Cd) in the substrate, the content of heavy metals in the plants also increased. The uptake of heavy metals by tomato could be reduced after inoculation with DSE. Under the exogenous Cd supplements with 10 mg/kg, the concentrations of Cd in the shoots and roots of tomato were decreased by 42.6% and 33.1% in the K36 inoculation group. and 47.1% and 48.3% in the Z48 group. respectively. Other treatment groups also showed the similar trends.4. Comparing to the non-stress treatments, the contents of malondialdehyde (MDA), and the activity of leaf superoxide dismutase (SOD), peroxidase (POD) and polyphenol oxidase (PPO) of tomatoes were increased under the stress of pathogen or heavy metal. While, the contents of MDA were reduced, and the activities of PPO, POD, SOD of tomatoes inoculated with DSE were increased, suggesting that DSE alleviated stress of pathogen and heavey metal through enhancing the antioxidant system of the plants.Our results indicated that the inoculation of DSE could promote plant growth, reduce the damage caused by pathogens and heavy metal stress and decrease the uptake of heavy metals. In these processes, the antioxidant system of tomato plays an important role.