Submitted to: Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/16/2008
Publication Date: 8/1/2009
Citation: Postnikova, E.N., Agarkova, I., Altundag, S., Eskandari, F., Sechler, A.J., Karahan, A., Vidaver, A.K., Schneider, W.L., Ozakman, M., Schaad, N.W. 2009. Rathayibacter iranicus isolated from asymptomatic wheat seeds in Turkey. Plant Pathology. 58:796.
Interpretive Summary: Rathayibacter iranicus (Ri), originally reported in Iran in 1961 (Sharif, 1961), has not been reported outside Iran and only one strain is known to exist. Like R. tritici (Rt), Ri causes a gumming disease of wheat in association with the nematode Anguina tritici. Asymptomatic wheat seeds from 799 farmers in six central provinces in Turkey were assayed for the presence of the Rathayibacter species by an agar plating assay. Of the 25 isolated strains presumptively identified as Rathayibacter species based on phenotypic and biochemical properties, three strains, TRS2, TRS10, and, TRS25 were used to determine the identification of the strains at the species level. The new strains were found by additional biochemical characterization to be most similar to R. tritici and R. iranicus. Analysis of cell wall composition, DNA fingerprinting, and sequencing identified and confirmed the new strains to be R. iranicus. This is the first report of R. iranicus outside of Iran. These strains have been deposited in the International Collection of Phytopathogenic Bacteria at Fort Detrick, MD for additional studies.
Technical Abstract: Asymptomatic wheat seeds collected from 799 farmers in six central provinces of Turkey were checked for the presence of Rathayibacter species by plating 100 µl of the diluted and undiluted seed wash suspension onto modified 523 agar. Of the 25 isolated strains presumptively identified as Rathayibacter based on a Gram positive reaction and an oxidase negative reaction, three strains, TRS2 from Konya, TRS10 from Hisarkikaya, and TRS25 from Ankara were used for further identification and speciation. The type strains of R. tritici (International Collection of Phytopathogenic Bacteria (ICPB) 70004 T, FH-5 T; CT 102 T) and R. iranicus, (ICPB 70005T, FH-6 T; CI 148 T), were included as controls for biochemical and genetic characterizations. All three strains were biochemically identified as R. iranicus and R. tritici by producing acid from D-mannose, inulin, galactose, and mannitol. Typical of R. iranicus but unlike R. tritici, the strains failed to utilize acetate, to hydrolyze casein, to grow on NBY containing more than 1% sodium chloride, or to grow on CNS agar. Lipid membrane analysis found the new strains contained the fatty acids iso-14:0 and 16:0; anteiso 15:0 and 15:1, and 17:0, and 16:0, also typical of R. iranicus. AFLP analysis of the strains showed all three shared a pattern nearly similar to R. iranicus (90% similarity) but very different from R. tritici (46% similarity). The identification of the three strains as R. iranicus was confirmed by the 16S rDNA sequence similarities to R. iranicus and R. tritici (100% and 99.3%, respecitively). This is the first report of R. iranicus outside of Iran. Cultures have been deposited in the ICPB at Ft. Detrick, MD as ICPB 70146 (FH-154; TRS2), 70154 (FH-162; TRS10), and 70169 (FH-177; TRS25).