Data/hora: 22/06/2024 00:49:46

Biblioteca(s): 	Embrapa Agrobiologia.	
Data corrente: 	28/09/2001	
Data da última atualização: 	28/09/2001	
Autoria: 	MEHNAZ, S.; MIRZA, M. S.; HAURAT, J.; BALLY, R.; NORMAND, P.; BANO, A.; MALIK, K. A.	
Título: 	Isolation and 16s rRNA sequence analipis of the beneficial bacteria from the rhizosphere of rice.	
Ano de publicação: 	2001	
Fonte/Imprenta: 	Canadian Journal of Microbiology, Ottawa, v. 47, p. 110-117, 2001.	
Idioma: 	Inglês	
Conteúdo: 	The present study deals with the isolation of plant growth promoting rhizobacteria (PGPR) from rice (variety NIAB IRRI-9) and the beneficial effects of these inoculants on two Basmati rice varieties. Nitrogen-fixing activity (acetylene-reduction activity) was detected in the roots and submerged shoots of field-grown rice variety NIAB IRRI-9. Estimation of the population size of diazotrophic bacteria by ARA-based MPN (acetylene reduction assay-based most probable number) in roots and shoots indicated about 105-106 counts/g dry weight at panicle initiation and grain filling stages. Four bacterial isolates from rice roots and shoots were obtained in pure culture which produced phytohormone indoleacetic acid (IAA) in the growth medium. Among these, three isolates S1, S4, and R3 reduced acetylene to ethylene in nitrogen-free semi-solid medium. Morphological and physiological characteristics of the isolates indicated that three nitrogen-fixing isolates S1, S4, and R3 belonged to the genus Enterobacter, While the non-fixing isolate R8 belonged to the genus Aeromonas. 16S rRNA sequence of one isolate from root (R8) and one isolate from shoot (S1) was obtained which confirmed identification of the isolates as Aeromonas veronii and Enterobacter cloacae, respectively. The 1517 - nucleotide-long sequence of the isolate R8 showed 99% similarity with Aeromonas veronii (accession No. AF099023) while partial 16S rRNA sequence (two stretches of total 1271 nucleotide lenght) of S1, showed 97% similarity with the sequence of Enterobacter cloacae (accession No. AJ251469). The seedings  of two rice varieties Basmati 385 and Super Basmati were inoculated with the four bacterial isolates from rice and one Azospirillum brasiliense strain Wb3, which was isolated from  wheat. In the rice variety Basmati 385, maximum increase in root area  and plant biomass was obtained in plants inoculated with Enterobacter S1 and Azospirillum Wb3, wheareas in the rice variety Super Basmati, inoculation with Enterobacter R3 resulted in maximum increase of root area and plant biomass. Nitrogen fixation was quantified by using 15N isotopic dilution method. Maximum fixation was observed in Basmati385 with the inoculants Azospirillum Wb3 and Enterobacter S1 where mearly 46% of the nitrogen was derived from atmosphere (%Ndfa), respectively. In general, higher nitrogen fixation was observed in variety Basmati 385 than in Super Basmati, and different bacterial strains were found more effective as inoculants for the rice varieties Basmati 385 and Super Basmati.  	
Palavras-Chave: 	BNF; Diazotrofico; Diazotrophs; FBN; Fixacao biologica de nitrogenio; Inoculation; Nitrogen fixing bacteria.	
Thesagro: 	Arroz; Bactéria; Inoculação; Raiz; Rizosfera.	
Thesaurus Nal: 	rhizosphere; rice; roots.	
Categoria do assunto: 	--	
Registro original: 	Embrapa Agrobiologia (CNPAB)	
Exemplares: 	CNPAB - (24645-1) - ADD - SP - -- -  -  - 22454 - DIS