Screening，identification，and growth-promoting characteristics of phosphate-solubilizing and potassium-solubilizing endophytic fungi from Camellia oleifera Abel

【Objective】 To screen phosphate-solubilizing and potassium-solubilizing endophytic fungi of Camellia oleifera Abel and investigate their growth-promoting capacity， which could provide theoretical basis for developing special microbial fertilizers and realizing sustainable and high-efficiency cultivation of Camellia oleifera Abel.【Method】 Endophytic fungi were isolated from the roots of Camellia oleifera Abel via the tissue isolation method. Strains with both phosphate-solubilizing and potassium-solubilizing capacities were preliminarily screened using inorganic phosphate （PKO） medium and Aleksandrov silicate medium， followed by morphological observation and molecular biological identification. The available phosphorus content was determined in liquid PKO medium. The strain with outstanding phosphate-solubilizing and potassium-solubilizing capacities was prepared into microbial fertilizer， and its growth-promoting effects on one-year-old Camellia oleifera Abel seedlings were analyzed. 【Result】 A total of 20 endophytic fungal strains were isolated from Camellia oleifera Abel roots. Two strains （designated LP8 and YP2） with obvious phosphate-solubilizing and potassium-solubilizing halos and superior comprehensive performance were obtained through primary screening. Morphological and molecular identification confirmed that strain LP8 was Penicillium ochrochloron， and strain YP2 was Penicillium cremeogriseum. The available phosphorus contents of LP8 and YP2 strains both peaked on the 5^th d of incubation， reaching 447.12 and 472.13 μg/mL respectively. The high-efficiency phosphate-solubilizing strain YP2 was made into microbial fertilizer and applied to Camellia oleifera Abel seedlings. Compared with CK， seedling height， ground diameter， fresh weight， and dry weight of seedlings treated with YP2 microbial fertilizer increased significantly by 37.39%， 17.67%， 19.31%， and 11.58% （P<0.05， the same below）； seedling growth status and root activity were remarkably improved. Chlorophyll a， chlorophyll b， and total chlorophyll contents rose significantly by 20.51%， 23.70%， and 21.70% compared to CK. The total potassium content of Camellia oleifera Abel seedlings treated by YP2 microbial fertilizer increased by 59.81%， while the soil total nitrogen and total phosphorus contents significantly increased by 14.57% and 27.70% respectively. In roots and leaves of YP2 microbial fertilizer treated seedlings， soluble sugar， soluble protein contents， as well as superoxide dismutase （SOD） and catalase （CAT） activities were all significantly higher than those of CK. 【Conclusion】 Two endophytic fungal strains LP8 and YP2 with dual phosphate-solubilizing and potassium-solubilizing capacities are isolated and screened from Camellia oleifera Abel roots， identified as Penicillium ochrochloron and Penicillium cremeogriseum respectively. YP2 microbial fertilizer can significantly boost the growth and development of Camellia oleifera Abel seedlings and enhance their stress resistance. It is suitable for Camellia oleifera Abel cultivation in phosphorus-deficient acidic red soil areas of Guizhou， and can be developed as a special microbial fertilizer for Camellia oleifera Abel.