Investigation On The Symbiotic Effect Of The Fungi In Parametarhizium Gen. Nov.

Parametarhizium gen.nov.is a novel genus isolated and established from forest litter in Northeast China in 2021,including P.hingganense and P.changbaiense The fungi in Parametarhizium has insecticidal activity and anti-plant pathogen activity.However,it is unclear whether the fungi in Parametarhizium has the ability to promote plant growth and enhance stress resistance.In this study,GFP-labeled P.hingganense and P.changbaiense were constructed to observe whether the fungi of Parametarhizium formed symbiotic relationship with plants.Combined with phenotypic,physiological and biochemical results,the effects of P.hingganense and P.changbaiense treatment on plant growth,disease resistance and saline-alkaline stress tolerance were studied.It provides a theoretical basis for the development and utilization of P.hingganense and P.changbaiense as plant growth promoters and biocontrol agents,and provides strainer resources for microbial agents that can be applied to sustainable agriculture.The main research contents and results are as follows:(1)After co-cultured with GFP-labeled fungal spores,the results of fluorescence microscopy showed that ectomycorrhizal symbiosis between the fungi and the roots of mung bean and rice was established.(2)Phenotypic analysis of mycorrhizal mung bean plants showed that the height,leaf area, root area,fresh weight and inorganic phosphorus(Pi)content were significantly increased.In addition,plant hormone levels changed,and the contents of jasmonic acid(JA)and salicylic acid(SA)increased significantly.Compared with P.changbaiense,P. hingganense presents stronger growth-promoting effect.(3)Phenotypic analysis of mycorrhizal rice showed that only P.hingganense promoted a significant increase in plant height.However,the chlorophyll content,fresh weight and root development of mycorrhizal plants were significantly increased.The number and length of lateral roots and the number and density of root hairs increased significantly.Compared with P.hingganense,P.changbaiense promoted root growth more significantly.Paraffin sections showed that the diameter of primary and crown root of mycorrhizal plants,number of xylem and phloem cells,the ratio of stele diameter to root diameter,number of thick-walled cells and lignin content increased significantly, in addition,the degree of lignification deepened.(4)The pathogen infection experiment showed that the phenylalanine ammonia lyase activity,total phenolic and total flavonoid content of mycorrhizal plants were significantly increased,and the malondialdehyde content was decreased.The control effects of P.hingganense and P.changbaiense on mung bean damping-off disease were 41.18% and 70.59%.The control effects of rice sheath blight were 6.06% and 42.09%.(5)Saline-alkali stress experiment showed that symbiosis with P.hingganense and P. changbaiense could significantly increase chlorophyll content and plant fresh weight,and promote root growth and development.The proline content in mycorrhizal plants increased and the malondialdehyde content decreased.Symbiosis with P.hingganense elevated salt tolerance,and symbiosis with P.changbaiense was more tolerant to alkaline stress.