Abstract: 【Objective】The objective of this study is to determine the taxonomic status of an actinomycete strain JXJ-0136, investigate its ability of dissolving insoluble phosphorus, the colonization in the rhizospheric soil of crops, and its influences on the seed germination, seedling growth and yield of vegetables, and to evaluate the application value of strain JXJ-0136 in developing microbial fertilizer.【Method】Taxonomic status of strain JXJ-0136 was determined on the basis of the cultural and morphological characteristics, and the phylogenetic analysis of 16S rRNA gene sequence. Influences of strain JXJ-0136 on the seed germination and seedling growth were studied using agar plate. The field cultivation tests were carried out to investigate the influences of strain JXJ-0136 on the growth and yield of vegetables. The total contents of phosphorus in the soil before and after the field trial were measured to investigate the influence of strain JXJ-0136 on the utilization of phosphorus in the soil by crops. The colonization of strain JXJ-0136 in the rhizospheric soil of the plants was investigated by isolation of the microorganisms in rhizosphere soil. The efficiencies of strain JXJ-0136 to dissolve insoluble inorganic and organic phosphorus were investigated using liquid pure culture. The model vegetables of the study were Brassica chinensis and Vigna unguiculata. 【Result】 Growth of actinomycete strain JXJ-0136 was observed at 6-45℃, pH 4.0-13.0 and 0-4% (w/v) NaCl, with optimal growth at 28℃, pH 8.0 and 1% (w/v) NaCl. Strain JXJ-0136 developed well-branched aerial mycelia on ISP 2 medium. The aerial mycelia was off-white in color. Its spore chains were fascicular with elliptical spores. The 16S rRNA gene sequence was closest to Streptomyces violascens, S. somaliensis, S. hydrogenans, S. albidoflavus and S. daghestanicus with the similarities of 97.98%, 97.71%, 97.30%, 97.23% and 97.03%, respectively. However, strain JXJ-0136 formed different clades on phylogenetic tree. The culture broth of strain JXJ-0136 enhanced the seed germination and the seedling growth significantly. After addition of 0.2%-0.8% broth culture of strain JXJ-0136, the seed germination rate, plant height and root length of B. chinensis were 3.55%-12.61%, 13.91%-53.03% and 7.37%-51.92% higher than those of the controls, respectively. The seed germination rate, plant height and root length of V. unguiculata were 4.71%-21.18%, 3.60%-22.33% and 2.37%-20.08% higher than these of the controls, respectively. The field cultivation tests indicated that strain JXJ-0136 could colonize in the rhizospheric soil of the plants, and promoted crops to utilize phosphorus in the soil, and enhanced the yields of the crops. After inoculating with 5 mL broth culture of strain JXJ-0136 to each plant, the soil total phosphorus contents of B. chinensis and V. unguiculata decreased by (23.56±2.65)% and (37.10±1.98)%, respectively, at the end of the tests, which were (1.77±0.29) and (2.70±0.15) times of the controls (P＜0.01). The yields of B. chinensis and V. unguiculata increased by (27.59±6.15)% and (70.29±5.15)% (P＜0.01) than the controls, respectively. After inoculating strain JXJ-0136 and culturing for 5 days under liquid pure culture condition, the pH values of inorganic and organic phosphorus cultures decreased to 5.0 and 6.0 initially from pH 7.0, respectively, and available phosphorus in the cultures of inorganic and organic phosphorus increased by (73.94±0.94) and (7.12±0.28) mg (P＜0.01), respectively. 【Conclusion】Actinomycete JXJ-0136 is a member of the genus Streptomyces. With good properties including increasing the seed germination, plant height and root length of seedling, colonizing in rhizospheric soil, increasing the content of the available phosphorus in the soil, enhancing the crops to utilize the phosphorus in the soil and promoting the growth and yields of crops, strain JXJ-0136 has a potential application value in developing microbial fertilizer.

Key words: microbial fertilizer, actinomycete JXJ-0136, Streptomyces, Brassica chinensis, Vigna unguiculata, phosphoric solubilization