Detection of streptomycin resistance in Erwinia amylovora strains isolated from apple orchards in Chihuahua, Mexico
Fire blight, one of the most severe diseases of apple and pear, is caused by the bacterium Erwinia amylovora. One control method is the use of antibiotics like streptomycin; however, streptomycin is the only antibiotic registered to control fire blight. A total of 107 E. amylovora strains were isolated from apple orchards located in Cuauhtémoc and Guerrero, Chihuahua, two major apple-producing areas in Mexico, showing 40 and 24 % streptomycin-resistant strains, respectively. The identification of E. amylovora strains was performed by polymerase chain reaction (PCR) amplification of a 900-bp region located within the non-transferable pEA29 plasmid and by amplification of a specific 1,269-bp region located on the E. amylovora chromosome. The 107 isolates tested carried the pEA29 plasmid, and 36 % of the isolates from both locations showed high resistance to streptomycin at levels that ranged from 200 to ≥1,000 μg ml−1 streptomycin. The strA-strB and aadA genes, which encode enzymes that inactivate streptomycin, and a mutation in codon 43 of the rpsL gene that confers high resistance to the antibiotic were examined to determine the mechanism of streptomycin resistance. In total, 95 % of the resistant strains showed a single base pair mutation in codon 43 of the rpsL gene, causing an amino acid substitution in ribosomal protein S12. The presence of strA-strB and aadA genes or the rpsL mutation was not identified in the other 5 % of resistant strains, suggesting the existence of a new streptomycin resistance mechanism in E. amylovora.
KeywordsErwinia amylovora Apple Fire blight Streptomycin resistance
- Coyier, D. L., & Covey, R. P. (1975). Tolerance of Erwinia amylovora to streptomycin sulfate in Oregon and Washington. Plant Disease Reporter, 59(10), 849–852.Google Scholar
- Gorris, M. T., Cambra, M., Llop, P., López, M. M., Lecomte, P., Chartier, R., et al. (1996). A sensitive and specific detection of Ewinia amylovora based on the ELISA-DASI enrichment method with monoclonal antibodies. Acta Hoticulturae, 411, 41–45.Google Scholar
- McGhee, G. C., Guasco, J., Bellomo, L. M., Blumer-Schuette, S. E., Shane, W. W., Irish-Brown, A., et al. (2011). Genetic analysis of streptomycin-resistant (SmR) srains of Erwinia amylovora suggests that dissemination of two genotypes is responsible for the current distribution of SmR E. amylovora in Michigan. Phytopathology, 101(2), 182–191.PubMedCrossRefGoogle Scholar
- Ramírez-Legarreta, M. R., Jacobo-Cuéllar, J. L., Ávila-Marioni, M. R., Gutiérrez–González, R., Parra-Quezada, R. A. (2003). Making decisions based on recommended practices for management of fire blight in apple in the mountains of Chihuahua. Technical Bulletin No. 6. Resource document in Spanish. National Institute for Forestry, Agriculture and Livestock (Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias). http://biblioteca.inifap.gob.mx:8080/jspui/handle/123456789/2561. PDF. Accessed 12 Dec 2012.
- Romo-Chacón, A., Berlanga-Reyes, D. I., Guerrero-Prieto, V. M., Martínez-Campos, R., Romero-Gómez, S., & Ramírez-Legarreta, M. R. (2011). Management of Erwinia amylovora with Oregano (Lippia berlandieri) essential oil and resistance study to streptomycin on apple trees cv. ‘golden delicious’. Mexican Journal of Phytopathology, 29(2), 119–132.Google Scholar
- Shaffer, W. H., & Goodman, R. N. (1985). Appearance of streptomycin-resistant Erwinia amylovora in Missouri apple orchards. Phytopathology, 75(11), 1281.Google Scholar
- Thomson, S. V., Gouk, S. C., Vanneste, J. L., Hale, C. N., & Clark, R. G. (1993). The presence of streptomycin resistant isolates of Erwinia amylovora in New Zealand. Acta Horticulturae., 338, 223–230.Google Scholar
- Van der Zwet, T., & Keil, H. L. (1979). Fire Blight. A bacterial disease of rosaceous plants: Handbook 510. Washington, DC: United States Department of Agriculture.Google Scholar