Study On Screening Of Phosphate-solubilizing Bacteria From Root Zone Soil Of Ginseng Under Forest And Promoting Effect On Ginseng Growth

Ginseng is one of the famous traditional Chinese medicine,mainly distributed in the three provinces of northeastern in China.The ginseng soil was deficiency in available phosphorus,which affects the accumulation of dry matter such as saponin of root.Excessive heavy metals,especially cadmium content in chemical phosphate fertilizer will cause ginseng heavy metal pollution,leading to the decline in ginseng quality.Therefore,screening high efficiency phosphorus solubilizing microorganism（PSM）as biofertilizer is very important for ginseng industry sustainable development.This reseach was conducted to isolate and screen PSM from ginseng root zone,and one strain with high phosphate solubilizing ability was obtained,identification and the mechanism of phosphate solubilizing as well as its growth promotion effect were done,and the results are as follows:Using calcium phosphate as insoluble phosphorus source,Using calcium phosphate as insoluble phosphorus source,the high-efficient phosphate-solubilizing bacteria P1 and P7 were screened from the soil of the root system by Pikovaskaia’s medium（PKO）observation of dissolved phosphorus ring and liquid shake medium.In the liquid medium,P1 soluble phosphorus was 472.85μg ml^-1,P7 soluble phosphorus was 437.33μg·ml^-1.The pot experiment showed that fresh weight and dry weight of ginseng in P1 treatment were significantly higher than those in P7 Bacillus megaterium（BM）and control（CK）treatment（P<0.05）,and the plant height in P1 treatment was significantly higher than CK.The chlorophyll content in P1treatment was significantly higher than P7,BM and CK treatments.The uptake of potassium in ginseng and accumulation of phosphorus in roots increased significantly in P1 treatment.In our study,soil enzyme activity（urease,acid phosphatase and peroxidase）increased in inoculation of bacteria,especially in P1 treatment.Determination of trace elements and saponins in ginseng root showed that Fe,Mn,Cu and Zn contents in P1 treatment were the highest,and increased by 52.74%,127.03%,28.96%and 19.96%respectively relative to those in the CK.The 8 kinds of saponins were significantly higher than those in the P7,BM,CK treatments.P1 strain was identified as Pseudomonas sp based on P1 strain physiological and biochemical and molecular biology characteristics.In liquid medium,the phosphate solubilizing ability of P1 strain was affected by different carbon sources,nitrogen sources and pH.The result suggested that the highest P solubilization capacity exhibited when glucose and ammonium nitrate served as C source and N source respectively,followed by glucose and ammonium sulphate.P1 can dissolve insoluble calcium phosphate in the range of pH 5⁸,and the available phosphorus concentration in the liquid medium of pH 5,pH8 is higher than pH6,pH7.With the increase of culture time,phosphate solubilization capacity of P1 strain was closely correlated to the drop of medium pH.