| China is hometown of kiwifruit and has the largest cultivation area of kiwifruit in the world.As of 2016,the planting area of Chinese kiwifruit reached about 1.5million mu,accounting for more than 70%of the total area of the world,and its output accounted for more than 60%of the world’s total output.With the increase of the growing period of kiwifruit,the occurrence of kiwifruit root rot is more common,and it is one of the major diseases,which affects the yield and quality of kiwifruit.At present,chemical pesticides are commonly used in the treatment of root rot disease.After the long-term application of chemical pesticides,some pests/pathogens have produced very strong resistance,causing some pests/pathogens to be very rampant.Many kinds of chemical pesticides seriously pollute water,air and soil,and enter the human body through food chain,thus endangering people’s health.Nowdays,biological control has been widely used in the world to control pests and diseases.Now,China urgently needs to use biological control methods to promote the development of green-sustainable agriculture.In this study,pathogenic fungi was isolated from roots of root rot kiwifruit and purified.Then,the pathogenic fungi were identified by re-inoculation test and molecular identification.A bio-control strain which could inhibit its growth was screened out and identified as Bacillus subtilis C3,and its biological characteristics were studied preliminarily.The mechanism of C3inhibiting the growth of pathogenic bacteria was explored at the laboratory level.Pot and field experiments were conducted to further verify the treatment effect of C3 on the root rot of Xu Xiang Kiwifruit.The main findings are as follows:1.Eight fungi were isolated from roots of root rot.According to the re-inoculation test,the pathogens of kiwifruit root rot were Fusarium species.Through the amplification of the root rot pathogenic fungal gene,the length of the amplified sequence was 568 bp.By compared with GenBank,the endophytic fungus was Fusarium solani.2.Strain C3 was isolated from the rhizosphere soil of normal kiwifruit fruit trees and identified as Bacillus subtilis by testing 16s rRNA,and the optimal culture conditions are as follows:the optimum temperature is 30℃,the optimal pH is 5,the brown sugar is the suitable carbon source;yeast extract is the optimal nitrogen source.C3 strains can produce chitinase,cellulase,amylase,protease,phosphatase and phytase.3.The main mechanism of C3 on controlling root rot of kiwifruit was:secreting antibacterial protein（deposition proteins by 60%（NH4）2SO4 have obvious inhibitory effects,and the main component is chitinase）,promoting the growth of kiwifruit seedlings（it promotes the growth of kiwifruit seedling roots by secreting auxin and gibberellin）,and inducing the resistance enzyme activity of seedlings（PAL,PPO,APX and SOD）.4.C3 agents could improve the growth of kiwifruit seedlings,which were planted on root diseased soil,whose biomass（fresh weight）was 1.140g/plant that had no significant difference with the normal group（seedlings were planted on soil that had been planted by wheat and its fresh biomass was1.11g/plant）.And,without adding C3,the biomass（fresh weight）of seedlings planted on root diseased soil was only Only 0.780g/plant.5.C3 could repair rhizosphere soil of kiwifruit root rot.C3 inoculum could enhance microbial activity and diversity in rhizospheric soil of diseased fruit trees,increase soil enzyme activity and fertility,induce resistance enzyme activity in kiwifruit fruit tree leaves,and ultimately improve kiwifruit fruit quality. |
