GFP Labeling Of Phosphate Solubilizng Bacteria WY4 And Its Colonization In Root System Of Chinese Cabbage(Brassica Chinensis)

Phosphorus(P)is macro-element in the natural system and agricultural system.According to statistics the results of soil survey,it is estimated that 2/3 of the soil is still lack phosphorus,but P is one of the important element influences on crop production.How to improve the yields of crop become a global problem for the whole world and humankind under the conditions of protecting the environment.Phosphate-solubilizing bacteria(PSB)were used widely,which belong to a kind of plant growth-promoting bacteria(PGPB)and were found earlier.PSB can promote the dissloving and utilizing of insoluble P,and improve the quality of soil which was minimal harm to the environment.At the same time,PSB have a good ability of promoting the growth of plant.In this experiment,WY4 can not only dissolve the organic phosphorus but also dissolve inorganic,which was identified as Bacillus megaterium by 16 s r RNA in our lab.WY4 was labeled with green fluorescent protein(GFP)in order to explore the effect on its colonization of Chinese cabbage.At the same time,WY4 was used to explore the effect on the growth and physiological nutrition quality of Chinese cabbage,physical and chemical properties of soil under field conditions.The main results are as follows:1.WY4 was labeled by GFP to obtain the marked bacterium named WY4-GFP which has a genetic stability.There were no significant differences between in the growth dynamics,the activity of dissloving phosphate and organic acid secretion by the marked strain of WY4-GFP compared with the wild-type strain WY4.The results indicated that GFP marker could not affect the physiological activity of the strain WY4.WY4-GFP could replace the wild-type strain for further study.2.WY4-GFP could be colonized in the rhizosphere soil and root tissues of Chinese cabbage.(1)After 30 d incubation in Chinese cabbage rhizosphere soils,the number of WY4-GFP were basically stabled at 5.80×104CFU/g.The results showed that WY4-GFP have a stable and persistent colonization in the rhizosphere soil of Chinese cabbage.(2)WY4-GFP was greatly colonization in the root cap and meristematic zone of Chinese cabbage,but the number of WY4-GFP was less in root hairs and the elongation zone of lateral root.The results further indicated that WY4-GFP flourishing colonizes in root system of Chinese cabbage.Meanwhile,there were no significant differences between WY4-GFP and WY4 in the growth of promoting Chinese cabbage.All of the results can provide important references for the further study of the relationship between phosphate-solubilizing bacteria and plants3.After application of WY4 under field conditions,WY4 still have a good ability of dissloving phosphate.The soluble P,soluble K,organic matter,nitrate nitrogen and ammonium nitrogen of soil were the highest after applying WY4.While,the soil p H reduced.The root length,plant height,leaf number and biomass of Chinese cabbage were significantly increased compared with the control(CK0).The content of soluble sugar,Vc and cellulose of leaf also markedly increased,but the content of nitrate nitrogen was decreased,so the quality of Chinese cabbage's leaf was improved.The field experiment showed that the applicaiton of WY4 increased the phosphorus fertilizer use efficiency and improved the soil quality,and promoted the growth of Chinese cabbage finaly.