Resumo

ROMO CHACON, Alejandro et al. Management of Erwinia amylovora with Oregano (Lippia berlandieri) Essential Oil and Resistance Study to Streptomycin on Apple Trees cv. 'Golden Delicious'. Rev. mex. fitopatol [online]. 2011, vol.29, n.2, pp.119-132. ISSN 2007-8080.

Fire blight, one of the most severe diseases on apples is caused by Erwinia amylovora (Ea), it provokes the death of flower buds and sometimes the whole tree. Antibiotic use is one of the methods employed to manage Ea, however, inappropriate use can lead to bacteria resistance. During 2005 and 2006, oregano (Lippia berlandieri) essential oil (80% carvacrol) was evaluated as an organic alternative to manage Ea. In vitro bactericidal minimum concentration (BMC) was 0.055 to 0.073% (w/v). A concentration of 0.11% was assessed in field and its effect on reducing the damage caused by Ea was determined. Results were compared against Agry-Mycin 100 ^MR, Cuprimicin 100 ^MR and Agry-Gent Plus 800^MR. During both years, treatments were not statistically different with respect to the control. Time of field applications was determined by detection of Ea epiphytic populations grown in semi-selective media, temperature and humidity, with values of 5%, 16.7°C and 78% respectively for 2005, and 96%, 15.2y 70% for 2006. Identification of Ea and its resistance to streptomycin was performed by growing the bacteria in semi-selective media and results were confirmed by PCR. An Ea strain resistant to streptomycin was detected and isolated. This is the first report of an Ea strain resistant to streptomycin and confirmed by molecular techniques in the most important apple area in the state of Chihuahua, Mexico.

Palavras-chave : Fire blight; epiphytic population; antibiotic; resistance; PCR.