Abstract: 29 strains of endophyte associated diazotrophs isolated from rice ( Oryza sutiva L. ) "Yuefu" plant were selected by in vitro acetylene reduced activity and 15 N2-flxing activity determination. They were identificated into 14 species of 9 genera: Agrobacterium tumefaciens (Smith et Townsend) Conn, A. radiobacter (Beijerinck et van Delden) Conn; Alcaligenes piechaudii Kiredjian et al., Al. denitrificans (Leifson et Hagh) Ruger et Tan; Bacillus sphaericus Meyer et Neide, B. licheniforrnis Weigmann Chester, B. cereus Frankland et Frankland; Chryseomonas luteola (Kodama, Kinnura et Komagata) Holmes et al.; Enterobacter cloacae ( Jordan ) Honnaeche et Edwards, E. sakazakii Famer et al.; E. agglomeraus (Beijerinck) Ewing et Fife; Pseudomonas pseudoalcaligenes Stanier, P. alcaligeaes Monias, P. putida Biotype A Evans and Aeromonas Kluyver et van Niel, Serratia Bizio, Staphyloccocus Rosenbach, Xanthomonas Dowson. Among them C. luteola, E. sakazakii, E. agglomeraus, P. pseudoalcaligenes have not been previously reported as diazotrophs. Studying on the distribution of endophytic dizoatrophs in rice seeds and rice plants has demonstrated that the diversity of endophytic associated diazotrophs in roots was more than that in other organs of rice plant. Endophytic associative diazotroph E. cloacae not only occurred on the surface but also occurred intercellularly in R48 rice roots as observed with scanning electron microscopy and transmission microscopy.

Key words: Rice, Endophytic associative diazotroph, Selection, Identification, Distribution