Effect Of Trichoderma On The Growth And Drought Resistance Of Isatis Indigotica

Trichoderma spp.is an important soil habitant fungus,which is widely found in different habitats in nature.Trichoderma is a safe,environmentally friendly and low-cost plant growth-promoting fungus,which plays an important role in the sustainable development of agriculture.As an important traditional medicinal plant,the dried leaves and roots of Isatis indigotica Fort.are widely used in the medical field.It is considered a natural antiviral drug.In this study,Trichoderma and I.indigotica were selected as the research objects.Seven Trichoderma strains(Trichoderma afroharzianum,Trichoderma atroviride,Trichoderma lixii,Trichoderma longibrachiatum,Trichoderma brevicompactum,Trichoderma virilente,and Trichoderma inhamatum)were isolated from the root zone soil of medicinal plants in Anguo,Hebei province,China.The tolerance of Trichoderma species to drought stress was studied by PEG-6000 simulation.In addition,pot experiments were conducted to investigate the effects of Trichoderma strains inoculated in sterilized and non-sterilized soil on the growth and drought resistance of I.indigotica.By measuring the growth and physiological indexes of I.indigotica,soil physical and chemical characteristics and soil microbial community structure,this study revealed the mechanism promoting effect of Trichoderma spp.on I.indigotica under drought stress and explored the function and application potential of Trichoderma spp.It provides a basis for the further development of Trichoderma agent.The main test results are as follows:1.In this study,we used PEG-6000 to simulate drought stress and clarified the growth and physiological characteristics of seven species of Trichoderma spp.in arid environment.Different Trichoderma species have different tolerance to drought stress.Principal component analysis showed that malondialdehyde and superoxide dismutase were the main indexes reflecting the response of Trichoderma to drought response.Trichoderma species can respond to the adverse effects of drought stress by regulating their own antioxidant protection system.In this study,four Trichoderma strains with strong drought tolerance were selected,which were T.afroharzianum,T.atroviride,T.lixii and T.longibrachiatum.2.In the pot experiment of sterilized soil,all the I.indigotica inoculated with Trichoderma spp.could grow healthily.Under drought stress,the aboveground biomass of I.indigotica seedlings inoculated with T.longibrachiatum and T.atroviride increased 30.75%and 44.55%,respectively,which was significantly higher than that of the control group.After inoculation with T.longibrachiatum,T.afroharzianum and T.atroviride,the underground biomass of I.indigotica seedlings increased significantly,which was 60.28%,41.73% and45.4% higher than that of the control group,respectively.3.Under drought stress,inoculation with Trichoderma spp.could increase SOD activity,proline,soluble protein,auxin and chlorophyll content,promote root growth,increase aboveground and underground biomass and epigoitrin content of I.indigotica seedlings,which alleviated the adverse effects of drought stress on I.indigotica plants.Variation partitioning analysis showed that Trichoderma species and water treatment explained 16.4%of the variation in the growth of I.indigotica seedlings.Soil nutrients explained 28.6% of the variation in the growth of I.indigotica seedlings.As a bridge between plant and soil,Trichoderma spp.can activate soil nutrients to make more effective use of I.indigotica.Furthermore,it promoted the growth of I.indigotica.In this study,three Trichoderma species with significant growth-promoting effects on I.indigotica were screened out,which were T.afroharzianum,T.atroviride and T.longibrachiatum.4.In the pot experiment of non-sterilized soil,all the I.indigotica inoculated with Trichoderma spp.could grow healthily.T.afroharzianum,T.atroviride and T.longibrachiatum could alleviate the adverse effects of drought stress on I.indigotica plants in different degrees under drought stress.Inoculation with T.afroharzianum and T.atroviride significantly increased the biomass of I.indigotica plants under drought stress.After inoculated with T.longibrachiatum,the biomass of I.indigotica plant was higher than that of the non-inoculated control group,but there was no significant difference.The inoculation of three Trichoderma species significantly increased soil organic carbon,available nitrogen and available phosphorus content.While the inoculation of three Trichoderma species significantly decreased the soil p H value.After inoculated with T.afroharzianum and T.longibrachiatum,the number of AM fungi and actinomycetes increased significantly.Trichoderma fungi not only increased soil nutrient content,but also improved soil microbial community structure.5.T.atroviride had a significant effect on the biomass,growth and physiological indicators of I.indigotica plants,and the epigoitrin content under drought stress conditions.Compared with the control group,the aboveground biomass,underground biomass and epigoitrin contents of I.indigotica increased 41.33%,43.63% and 74.69%,respectively.In addition,proline,auxin,GSH content and SOD activity were all significantly affected by the interaction between Trichoderma species and water treatments,and the inoculation with Trichoderma has the greatest impact on it.The results showed that inoculation with T.atroviride can alleviate the adverse effects on I.indigotica plants and help its growth and survival under drought stress.The strain could be used as the most effective fungus for the cultivation of I.indigotica and could promote the growth of I.indigotica under drought stress.6.Through studying the drought-resistant ability of Trichoderma spp.and the effect of Trichoderma spp.on I.indigotica,an excellent strain with drought resistance and growth promotion was found.It provides the basis for further development of Trichoderma agent,which is of great significance to the sustainable development of the traditional Chinese medicine industry.