| Grasses are the most important plants in the world because of their economic and ecological function. However, the plants need more nitrogen and phosphorus in their life. To provide more nitrogen and phosphorus for plant growth, chemical fertilizers play an important role. Unfortunately, chemical fertilizers produce more pollution and other disadvantage as well. Therefore, exploiting other source to supply part or all nitrogen and phosphorus for plant is more important.The present study tries to isolate and characterize PGPR strains that can be used as biofertilizer for oat and wheat by using advanced equipment and facilities like GC & HPLC as well as reliable method such as NPM, FA, RAPD and I5N-isotope dilution. The results obtained are as follows:1. There are PGPR strains colonized on root rhizosphere and in histoplant of oat and wheat. Total lOstrains isolated from oat, and they locate to Azotobacter (4strains), Pseudomonas (4 strains) and Azosprillus (2 strains). Total 15 PGPR strains obtained from wheat as well, and all of them belong to Azotobacter (5 strains), Pseudomonas (4 strains), Azosprillus (4 strains), Alcaligems (1 strain) and Tjjoglea (1 strain).2. Strains distribution vary with fractions (NRS, RS, RP and HP), and the amount tendency is as RP>RS>NRS > HP. Most of them (48%) attached on therhizosphere (RS & RP); Some of them (20%) only exist in soil (NRS, 8%) or on the root surface (RP, 12%); Few of them (8%) colonize in histoplan (HP); And still some of them (24%) lie hi soil (MRS) as well as rhizosphere (RS & RP).3. Most of strains (92%) obtained fast grow on LB, NFM and CCM media, especially on LB medium. All the strains (except ChW4) can growth well on different LB medium which peptone was replaced with any one of other carbon source, that is mannitol, molasses, glucose, sucrose, and l/2mannitol +l/2sucrose. While some strains are poor growth on LB medium which peptone was replaced with xylose or galactose or maltose.4. Out of 25 strains, there are 13 alkaline producer strains (77% from wheat), 6 acid producer strains (67% from oat), and 6 neutral strains.5. In natural condition (without inoculate), there are diazotrophs exist in root -soil system, but the amount is significant difference and rather low (02~106 bacteria /g dry soil or root) with fractions. Tendency of diazotrophs quantity and nitrogen fixer percent is as RP>RS>NRS>HP and HP >RP>RS>NRS respectively.6. Generally, ChWl (Pseudomonas sp.) is widely distribution strains compared with ChW6 (Zoogloea sp.). ChWl was easily isolated from different fractions of oat and wheat (except HP), but ChW6 only be isolated from the fractions (RS and RP) of wheat. It means that ChW6 has certain special combined with wheat.7. In natural condition, although there are diazotrophs exist hi root-soil system, the amount is rather low (lOMO6bacteria /g dry soil or root). Therefore, it is necessary to inoculate proper inoculum to increase diazotrophs quantity so as to improve competition of diazotrophs as well as quantity of fixing nitrogen.8. Most (80%) of strains show positive nitrogenaes activity though only a few of diem show high value by using GO Nitrogenase activity is 112.5-1147.9 nmol C2H4/h/ml and 124.6~651.6 nmol C2H4 / h / ml of wheat strains and oat strainsrespectively. There are 6 and 5 strains, which nitrogenase activity are higher than 300 nmol C2H4/h/mls, hi oat and wheat respectively. Strains ChO3, ChO5, Ch09, ChO7 and ChW6, ChWll, ChW5, ChWl show more potential used as producing biofertilizer for oat and wheat respectively according to their nitrogenase activity.9. A few (5 strains) of phosphorus-solubilizing strains were obtained. Seedling growth was promoting by inoculate the phosphate solubilizing strains.10. Most of strains have ability to produce phytohormone (IAA) although a few of strains show high IAA concentration by HPLC. IAA concentration is 2.16~17.31ug /ml andl.40~15.13ug/ml of oat and wheat strains respectively. There are 4 strains from oat and 4 strains...
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