Bacterial contamination of fresh tomato fruits is of great concern. From naturally infected tomato fruits showing dark brown irregularly shaped spots, 36 bacterial isolates were recovered and identified on phenotypic characteristics and sequences of the gene encoding the 16S rRNA. Five isolates showing spots on tomato fruits in the pathogenicity test with healthy tomato fruits belong to the genus Serratia on the basis of phenotypic characteristics. One representative isolate of these has been further identified as a Serratia rubidaea by sequencing of the 16S rRNA gene. This is the first evidence showing that a S. rubidaea strain can cause spots on tomato fruits. Virulence of the S. rubidaea was also confirmed by the production and secretion of a large variety of enzymes capable of degrading the complex polysaccharides of the plant cell wall and membrane constituents. Nineteen bacterial isolates of the 36 did not induce any spot symptoms in a pathogenicity test on artificially infected tomato fruits although these are known as phytopathogenic bacteria. Five of these 19 bacterial isolates were identified as Ralstonia species on the basis of biochemical tests. Sequencing of the 16S ribosomal gene of one representative isolate revealed that the isolate is closely related to Ralstonia solanacearum. Six isolates of the 19 were related to Xanthomonas vesicatoria on the basis of biochemical tests and eight were related to the Enterobacteriaceae. One representative isolate of the Enterobacteriaceae could be identified by the 16S rRNA gene as Enterobacter cloacae subsp. dissolvens. The 12 other strains were related to Proteus mirabilis based on the 16S RNA gene sequence of one representative isolate. The isolates related to P. mirabilis did not produce any symptoms on artificially infected tomato fruits. The nucleotide sequences of S. rubidaea strain E9, E. cloacae strain E23, P. mirabilis strain E11, and R. solanacearum strain E15 have been deposited in the GenBank nucleotide sequence database under accession numbers HM585373 to HM585376.

Bacterial contamination of fresh tomato fruits is of great concern. From naturally infected tomato fruits showing dark brown irregularly shaped spots, 36 bacterial isolates were recovered and identified on phenotypic characteristics and sequences of the gene encoding the 16S rRNA. Five isolates showing spots on tomato fruits in the pathogenicity test with healthy tomato fruits belong to the genus Serratia on the basis of phenotypic characteristics. One representative isolate of these has been further identified as a Serratia rubidaea by sequencing of the 16S rRNA gene. This is the first evidence showing that a S. rubidaea strain can cause spots on tomato fruits. Virulence of the S. rubidaea was also confirmed by the production and secretion of a large variety of enzymes capable of degrading the complex polysaccharides of the plant cell wall and membrane constituents. Nineteen bacterial isolates of the 36 did not induce any spot symptoms in a pathogenicity test on artificially infected tomato fruits although these are known as phytopathogenic bacteria. Five of these 19 bacterial isolates were identified as Ralstonia species on the basis of biochemical tests. Sequencing of the 16S ribosomal gene of one representative isolate revealed that the isolate is closely related to Ralstonia solanacearum. Six isolates of the 19 were related to Xanthomonas vesicatoria on the basis of biochemical tests and eight were related to the Enterobacteriaceae. One representative isolate of the Enterobacteriaceae could be identified by the 16S rRNA gene as Enterobacter cloacae subsp. dissolvens. The 12 other strains were related to Proteus mirabilis based on the 16S RNA gene sequence of one representative isolate. The isolates related to P. mirabilis did not produce any symptoms on artificially infected tomato fruits. The nucleotide sequences of S. rubidaea strain E9, E. cloacae strain E23, P. mirabilis strain E11, and R. solanacearum strain E15 have been deposited in the GenBank nucleotide sequence database under accession numbers HM585373 to HM585376.

The goal of this study was to investigate the response of activation of Rhizobium tibeticum with mixture of hesperetin and apigenin to improve growth, nodulation, and nitrogen fixation of fenugreek grown under cobalt (Co) stress. The current study showed that high concentrations of Co-induced noxious effects on rhizobial growth, nod gene expression, nodulation, phenylalanine ammonia-lyase (PAL) and glutamine synthetase (GS) activities, total flavonoid content, and nitrogen fixation. Addition of a mixture of hesperetin and apigenin to growth medium supplemented with different concentrations of Co signifi- cantly increased bacterial growth. PAL activity of roots grown hydroponically at 100 mg kg-1 Co and inoculated with induced R. tibeticum was significantly increased compared with plants receiving uninduced R. tibeticum. Total flavonoid content of root exudates of plants inoculated with activated R. tibeticum was significantly increased compared with inoculated plants with unactivated R. tibeticum or uninoculated plants at variant Co dosages. Application of 50 mg kg-1 Co significantly increased nodulation, GS, nitrogenase activity, and biomass of plants inoculated with either or uninduced R. tibeticum. The total number and fresh mass of nodules, nitrogenase activity, and biomass of plants inoculated with induced cells grown in soil treated with 100 and 200 mg kg-1 Co were significantly increased compared with plants inoculated with uninduced cells. Induced R.tibeticum with flavonoids significantly alleviates the adverse effect of Co on nod gene expression and therefore enhances nitrogen fixation. Induction of R. tibeticum with compatible flavonoids could be of practical importance in augmenting growth and nitrogen fixation of fenugreek grown in a Co-contaminated agroecosystem.

The goal of this study was to investigate the response of activation of Rhizobium tibeticum with mixture of hesperetin and apigenin to improve growth, nodulation, and nitrogen fixation of fenugreek grown under cobalt (Co) stress. The current study showed that high concentrations of Co-induced noxious effects on rhizobial growth, nod gene expression, nodulation, phenylalanine ammonia-lyase (PAL) and glutamine synthetase (GS) activities, total flavonoid content, and nitrogen fixation. Addition of a mixture of hesperetin and apigenin to growth medium supplemented with different concentrations of Co signifi- cantly increased bacterial growth. PAL activity of roots grown hydroponically at 100 mg kg-1 Co and inoculated with induced R. tibeticum was significantly increased compared with plants receiving uninduced R. tibeticum. Total flavonoid content of root exudates of plants inoculated with activated R. tibeticum was significantly increased compared with inoculated plants with unactivated R. tibeticum or uninoculated plants at variant Co dosages. Application of 50 mg kg-1 Co significantly increased nodulation, GS, nitrogenase activity, and biomass of plants inoculated with either or uninduced R. tibeticum. The total number and fresh mass of nodules, nitrogenase activity, and biomass of plants inoculated with induced cells grown in soil treated with 100 and 200 mg kg-1 Co were significantly increased compared with plants inoculated with uninduced cells. Induced R.tibeticum with flavonoids significantly alleviates the adverse effect of Co on nod gene expression and therefore enhances nitrogen fixation. Induction of R. tibeticum with compatible flavonoids could be of practical importance in augmenting growth and nitrogen fixation of fenugreek grown in a Co-contaminated agroecosystem.

The goal of this study was to investigate the response of activation of Rhizobium tibeticum with mixture of hesperetin and apigenin to improve growth, nodulation, and nitrogen fixation of fenugreek grown under cobalt (Co) stress. The current study showed that high concentrations of Co-induced noxious effects on rhizobial growth, nod gene expression, nodulation, phenylalanine ammonia-lyase (PAL) and glutamine synthetase (GS) activities, total flavonoid content, and nitrogen fixation. Addition of a mixture of hesperetin and apigenin to growth medium supplemented with different concentrations of Co signifi- cantly increased bacterial growth. PAL activity of roots grown hydroponically at 100 mg kg-1 Co and inoculated with induced R. tibeticum was significantly increased compared with plants receiving uninduced R. tibeticum. Total flavonoid content of root exudates of plants inoculated with activated R. tibeticum was significantly increased compared with inoculated plants with unactivated R. tibeticum or uninoculated plants at variant Co dosages. Application of 50 mg kg-1 Co significantly increased nodulation, GS, nitrogenase activity, and biomass of plants inoculated with either or uninduced R. tibeticum. The total number and fresh mass of nodules, nitrogenase activity, and biomass of plants inoculated with induced cells grown in soil treated with 100 and 200 mg kg-1 Co were significantly increased compared with plants inoculated with uninduced cells. Induced R.tibeticum with flavonoids significantly alleviates the adverse effect of Co on nod gene expression and therefore enhances nitrogen fixation. Induction of R. tibeticum with compatible flavonoids could be of practical importance in augmenting growth and nitrogen fixation of fenugreek grown in a Co-contaminated agroecosystem.

The goal of this study was to investigate the response of activation of Rhizobium tibeticum with mixture of hesperetin and apigenin to improve growth, nodulation, and nitrogen fixation of fenugreek grown under cobalt (Co) stress. The current study showed that high concentrations of Co-induced noxious effects on rhizobial growth, nod gene expression, nodulation, phenylalanine ammonia-lyase (PAL) and glutamine synthetase (GS) activities, total flavonoid content, and nitrogen fixation. Addition of a mixture of hesperetin and apigenin to growth medium supplemented with different concentrations of Co signifi- cantly increased bacterial growth. PAL activity of roots grown hydroponically at 100 mg kg-1 Co and inoculated with induced R. tibeticum was significantly increased compared with plants receiving uninduced R. tibeticum. Total flavonoid content of root exudates of plants inoculated with activated R. tibeticum was significantly increased compared with inoculated plants with unactivated R. tibeticum or uninoculated plants at variant Co dosages. Application of 50 mg kg-1 Co significantly increased nodulation, GS, nitrogenase activity, and biomass of plants inoculated with either or uninduced R. tibeticum. The total number and fresh mass of nodules, nitrogenase activity, and biomass of plants inoculated with induced cells grown in soil treated with 100 and 200 mg kg-1 Co were significantly increased compared with plants inoculated with uninduced cells. Induced R.tibeticum with flavonoids significantly alleviates the adverse effect of Co on nod gene expression and therefore enhances nitrogen fixation. Induction of R. tibeticum with compatible flavonoids could be of practical importance in augmenting growth and nitrogen fixation of fenugreek grown in a Co-contaminated agroecosystem.