Studies On The Effects Of Six Highly Antagonistic Phosphate-solubilizing Fungi On The Growth Promotion And Stress Resistance Of Karst Plant Orychophragmus Violaceus

Phosphate-solubilizing fungi(PSF)are a kind of important functional fungi widely existing in the soil environment.Because of their unique phosphatesolubilizing ability and genetic stability,PSF have important application value in green agricultural production practice and ecological environment restoration,and have become an important microbial resource at present.In the karst rocky desertification area in Southwest China represented by Guizhou area,the soil erosion is serious,the rocks are exposed,the plant coverage is low,and the phosphate in soil is difficult to dissolve due to its close combination with other minerals,as a result,phosphorus becomes one of the nutrient elements limiting plant growth in the process of restoration of rocky desertification.The studies show that PSF can significantly increase the content of available phosphate in poor phosphorus soil and provide a good living environment for plant growth and development.Moreover,PSF also play an important role in improving plant response to drought,saline alkali and other stresses,but at present,the resources of multifunctional PSF which can meet the production practice of green agriculture and ecological environment restoration are still very limited.The objectives of this study: By collecting the soil samples from plant rhizosphere to isolate PSF,to build a set of screening technology and methods for PSF resources,to screen a number of multifunctional PSF with growth promotion,antagonism and stress resistance,from the perspective of microbiology,and thus these provide important resource base for ecological restoration and green agricultural production practice of karst rocky desertification in Guizhou.In this paper,a batch of fungi with phosphate-solubilizing ability were isolated by dilution plate method by collecting plant rhizosphere soil samples;The potential biocontrol ability of PSF against Colletotrichum camellia,Botrytis cinerea,Sclerotinia sclerotiorum and Fusarium oxysporum,which are important pathogens of crop diseases,and was evaluated by plate confrontation culture and strain fermentation broth method;Through the test tube culture of cucumber seedlings and the pot experiment of O.violaceus,the growth promoting ability of PSF on plants was quickly screened and evaluated;15% PEG-6000 and 300 mmo L/L saline alkali solution were used to simulate drought and saline alkali stress,and the effects of the strains on improving the drought and saline alkali resistance of O.violaceus were evaluated;The molecular phylogenetic tree was constructed based on the morphological characteristics of six highly effective PSF combined with internal transcribed spacer(ITS)and the RNA polymerase II(rpb2)genes to identify the taxonomic status of the strains.In this study,29 soil samples collected from sites in Guizhou,Guangdong,Guangxi and Anhui provinces,a total of 88 fungal strains with phosphate-solubilizing ability were isolated,of which 17 PSF not only had a strong antagonistic effects on the above four pathogens,but also showed a strong plant growth promoting effects.Among them,six PSF,such as AHBB-HS134,GYAHH-CCT186,GYAHH-CCT188,AHBB-CT195,AHBB-CT196 and GDDG-JC710,have significant growth promoting effects on the karst plant O.violaceus,and AHBB-CT195 and AHBB-CT196 had the best growth promoting effects with increasing 166.72% and 207.32% of total dry weight respectively,and significantly improved the tolerance of O.violaceus to the environmental stresses by saline alkali and drought.By constructing the molecular phylogenetic trees,the taxonomic statuses of six representative strains of PSF were identified respectively.AHBB-HS134 belongs to Thalaromyces genus,GYAHH-CCT186,GYAHH-CCT188,AHBB-CT195 and GDDG-JC710 belong to Penicillium genus,and AHBB-CT196 belongs to Aspergillus genus.GDDG-JC710 is a new species of Penicillium,of which was named Penicillium dongguanensis G.Tao,Y.Meng ? D.Q.Huang,and the species was described.In this study,we isolated a number of fungal resources with strong phosphate solubilizing ability.Among them,17 PSF strains with ecological roles of plant growth promotion and biocontrol etc.were selected.In the practice of green agriculture and ecological environment restoration of karst rocky desertification,their applications will provide important fungal resources for the further research and development of high-efficiency PSF agents and novel microbial fertilizers.