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Diversity and growth promotion of endophytic bacteria isolated from Oryza officinalis in Guangxi.

YANG Jie, QIN Ying-xi, WANG Xiao-tian, YIN Kun, JIANG Yuan, YUAN Tao, TAN Zhi-yuan**   

  1. (College of Agriculture, South China Agricultural University, Guangzhou, 510642, China)
  • Online:2015-11-10 Published:2015-11-10

Abstract: The endophytic bacteria isolated from Oryza officinalis growing in Guangxi were screened by two nitrogenfree media and grouped by IS-PCR DNA fingerprinting. The representative strains of each group were further studied by physiological and biochemical tests, and 16S rRNA gene analysis. The possible plant growth promotion of the endophytic diazotrophs was tested in the rice. The results showed that a total of 69 endophytic bacteria including 26 endophytic diazotrophs were obtained from O. officinalis. The nitrogenase activity of the endophytic diazotrophs ranged from 0.60 to 46.71 μmol C2H4·mL-1·h-1. The 69 endophytic bacteria were assigned to 11 groups and 1 ungrouped strain by analysis of IS-PCR DNA fingerprinting. 16S rRNA gene sequencing analysis of representative strains of each group showed that the endophytic diazotrophs were closely related to Ideonella spp., Enterobacter asburiae, Azospirillum largimobile, and the other endophytic bacteria were closely related to Bacillus pumilus, B. cereus, Rhizobium daejeonense, B. safensis, Lysinibacillus fusiformis, Microbacterium paraoxydans, Paenibacillus barcinonensis, and Serratia marcescens, which indicated the high diversity of endophytic bacteria colonized in the host plants of O. officinalis. All of the representative strains of the endophytic bacteria have the ability to release phosphate and potassium. Among these endophytic bacteria, strain yy34 has a great ability of phosphate releasing and strains yy19, yy26 and yy29 have a great ability of potassium releasing. Seven strains (yy05, yy16, yy19, yy25, yy29, yy34 and yy49) can secrete indole3-acetic acid. The representative strains of the endophytic diazotrophs inoculated with rice significantly promoted the rice growth. The leaf length of inoculated rice increased by 23.0%-45.2%, the root length increased by 19.8%-36.2%, the tiller number increased by 59.9%-119.8%, the fresh weight of rice increased by 101.4%-257.0%, the dry weight of rice increased by 68.4%-101.7%, and the root weight increased by 122.2%-188.9% compared with noninoculated rice.

Key words: yield, root-borne disease, grafting, rhizosphere soil environment, pepper