Detection of bacteria associated with European pear buds in Rio Grande do Sul State, Brazil. [Portuguese]Original Title Deteccao de bacterias associadas a gemas de pereiras europeias no Rio Grande do Sul.

摘要

The death of flowers in European pear (Pyrus communis L.) orchards was observed in Vacaria, State of Rio Grande do Sul, Brazil. Two bacterial isolates, obtained from symptomatic flowers, reproduced these symptoms on flowers of detached branches and were identified as Pseudomonas sp. Considering the lack of reports of this disease in Brazil, the record of P. syringae pv. syrigae and Erwinia amylovora associated with similar symptoms in other countries and the possible presence of these bacteria in buds, a method to detect the three bacteria was developed. The method comprised: bud maceration with liquid nitrogen, addition of PBS and 2% PVP, transfer of juice to FTA cards (Whatman), treatment of card circles with 70% ethanol, TE buffer and FTA reagent, elution of DNA followed by PCR with specific primers for each bacterium. The method was further used to monitor these bacteria in buds collected bimonthly during 2008. E. amylovora was not detected. The average frequency of P. syringae pv. syringae and Pseudomonas sp. was 0.7 and 16.3%, respectively, the latter showing a frequency peak of 30% in October. The species of the causal agent was not made clear, but the association with the genus Pseudomonas was demonstrated, which already provides a basis for the development of methods for disease control.