Phosphate-solubilizing characteristics of Bacillus amyloliquefaciens PHODB35 and its growth-promoting effect on tomato

Abstract:

[Objective] Phosphorus-soluble bacteria were screened from the soil around the roots of tomato plants to provide phosphorus-soluble bacteria resources for the development of biofertilizers for increasing production and saving fertilizer, and their growth-promoting mechanism was preliminarily explored. [Methods] Inorganic phosphorus medium was used to isolate and screen the growth-promoting strains from soil by serial dilution plating method. The excellent growth-promoting strains were identified by morphological characteristics, 16S rRNA gene sequence and gyrB gene sequence analysis, and the effects of environmental factors and nutrient factors on phosphorus solubility were studied by orthogonal and single factor test. Organic acids produced by excellent growth-promoting strains were identified by HPLC-MS, according to the standard substances of corresponding organic acids, and the growth-promoting effect of strains on tomato was determined by pot experiment. [Results] A good growth-promoting strain named PHODB35 was isolated. It was identified as Bacillus amyloliquefaciens. The orthogonal test of environmental factors shows that the optimum conditions for dissolving phosphorus of strain PHODB35 were pH 7.0, temperature at 30℃ and 5% inoculation. The results of single-factor experiments on nutrient factors show that strain PHODB35 had the best phosphorus dissolution effect with glucose as carbon source, ammonium sulfate as nitrogen source, calcium phosphate as phosphorous source, initial pH 7.0 and temperature at 30℃. The effective phosphorus concentration was 88.77 mg/L. Gluconic acid was produced by strain PHODB35. Pot experiment showed that the application of strain PHODB35 had obvious growth-promoting effect on tomato seedlings. Compared with the control, the plant height, above-ground fresh weight, under-ground fresh weight, substrate and plant available phosphorus content were increased by 28.21%, 22.59%, 113.06%, 45.08% and 16.24%, respectively, after inoculating strain PHODB35, indicating that strain PHODB35 had certain fertilizer effect and could be used for the development of growth-promoting agents. [Conclusion] Phosphorus solubilizing bacteria were screened to provide resources for further development of tomato specific growth-promoting agent or special microbial organic fertilizer, and to provide theoretical and experimental basis for the application of strain PHODB35 in agricultural production.