Screening of phosphate-solubilizing fungi from phosphate -rich soils in Dianchi and its effect on growth promoting in Brassica napus

Forty-eight isolates of phosphate solubilizing fungi (PSF) were isolated from 89 soil samples and their tricalcium phosphate (TCP) solubilization efficiencies were evaluated by Mo-blue method. The results showed that the concentration of soluble phosphates in liquid cultures ranged from 14.45 to 64.87 mg/L. SPF46, SPF47, and Mo-Po were the most efficient isolates releasing 55.44, 59.78 and 64.87 mg/L soluble phosphate in liquid cultures, respectively. By morphological features and ITS rDNA sequences homology analysis, the three isolates were identified as Penicillium citreonigrum, P. oxalicum and Aspergillus niger, respectively. They showed the highest phosphorus solubilization efficiency in the presence of TCP compared to the other tested FePO4.4H2O and AlPO4. Pot experiment showed that the inoculation of the three PSF isolates significantly increased the nape growth. Individual inoculation of the three isolates resulted in 10.16%-294.7% increase in root length, 32.19%-134.5% increase in plant height, 35.53%-170.5% increase in leaf diameter, 30.71%-189.5% in fresh weight and 56%-224% increase in dry weight, respectively. Meanwhile, a consortium of the three isolates showed 129.4% increase in root length, 60.41% increase in plant height, 170.5% increase in leaf diameter, 246.1% increase in fresh weight and 272.2% increase dry weight, respectively.