Abstract
A novel, plant growth-promoting bacteriumDelftia tsuruhatensis, strain HR4, was isolated from the rhizoplane of
rice (Oryza sativaL., cv. Yueguang) in North China. In vitro antagonistic assay showed this strain could suppress the
growth of various plant pathogens effectively, especially the three main rice pathogens (Xanthomonas oryzaepv.
oryzae, Rhizoctonia solaniandPyricularia oryzaeCavara). Treated with strain HR4 culture, rice blast, rice bacterial
blight and rice sheath blight for cv. Yuefu and cv. Nonghu 6 were evidently controlled in the greenhouse. Strain HR4
also showed a high nitrogen-fixing activity in N-free Do¨bereiner culture medium. The acetylene reduction activity and
15
N2-fixing activity (N2FA) were 13.06 C2H4nmol ml
1
h
1
and 2.052
15
Na.e.%, respectively. Thenifgene was located
in the chromosome of this strain. Based on phenotypic, physiological, biochemical and phylogenetic studies, strain
HR4 could be classified as a member ofD. tsuruhatensis. However, comparisons of characteristics with other known
species of the genusDelftiasuggested that strain HR4 was a novel dizotrophic PGPB strain.
r2004 Elsevier GmbH. All rights reserved.
AbstractA novel, plant growth-promoting bacteriumDelftia tsuruhatensis, strain HR4, was isolated from the rhizoplane ofrice (Oryza sativaL., cv. Yueguang) in North China. In vitro antagonistic assay showed this strain could suppress thegrowth of various plant pathogens effectively, especially the three main rice pathogens (Xanthomonas oryzaepv.oryzae, Rhizoctonia solaniandPyricularia oryzaeCavara). Treated with strain HR4 culture, rice blast, rice bacterialblight and rice sheath blight for cv. Yuefu and cv. Nonghu 6 were evidently controlled in the greenhouse. Strain HR4also showed a high nitrogen-fixing activity in N-free Do¨bereiner culture medium. The acetylene reduction activity and15N2-fixing activity (N2FA) were 13.06 C2H4nmol ml1h1and 2.05215Na.e.%, respectively. Thenifgene was locatedin the chromosome of this strain. Based on phenotypic, physiological, biochemical and phylogenetic studies, strainHR4 could be classified as a member ofD. tsuruhatensis. However, comparisons of characteristics with other knownspecies of the genusDelftiasuggested that strain HR4 was a novel dizotrophic PGPB strain.r2004 Elsevier GmbH. All rights reserved.
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