RESUMO
Bacterial canker, caused by Pseudomonas syringae pv. actinidiae, is one of the most severe diseases of kiwifruit. It has become an international pandemic and threatens the sustainable development of kiwifruit production in all main kiwi-growing regions worldwide. Streptomycin has been the major bactericide for the control of kiwifruit canker, especially in Anhui Province, one of the main kiwifruit production regions in China. However, until now, no studies on the baseline sensitivity to streptomycin of field isolates of P. syringae pv. actinidiae from China have been available. During 2012-2013, a total of 102 single-colony P. syringae pv. actinidiae strains were isolated: 36, 12, 13, 26, and 15 strains from Yuexi, Jinzhai, Huoshan, Qianshan, and Taihu counties, respectively. All strains were confirmed by production of a 280-bp fragment using the specific primers PsaF1/R2 upon polymerase chain reaction amplification, followed by an assay for confirmation of pathogenicity to fulfill Koch's postulates. In this study, the streptomycin sensitivity of the 102 isolated strains was determined. The half-maximal effective concentration values for inhibition of growth by streptomycin were 0.03-0.42 µg/mL (average 0.12 ± 0.06 µg/mL). The baseline sensitivity curve was unimodal, representing range-of-variation factors of 14.0. No resistant subpopulation was identified among the strains used in the study. Thus, these sensitivity data could be used as a baseline for monitoring the shift in sensitivity of P. syringae pv. actinidiae populations to streptomycin in Anhui Province. Continuous resistance monitoring should be carried out, as streptomycin is an at-risk bactericide agent.
Assuntos
Actinidia/microbiologia , Doenças das Plantas/microbiologia , Pseudomonas syringae/fisiologia , Estreptomicina/farmacologia , Sequência de Bases , Bioensaio , China , Dados de Sequência Molecular , Pseudomonas syringae/efeitos dos fármacos , Pseudomonas syringae/isolamento & purificação , Pseudomonas syringae/patogenicidadeRESUMO
The aim of this study was to develop a method to detect a point mutation in the ribosomal S12 protein (rpsL) gene in streptomycin-resistant strains of Xanthomonas oryzae pv. oryzicola and X. oryzae pv. oryzae. The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method was developed to detect a point mutation in codon 43 of the rpsL gene in X. oryzae pv. oryzicola and X. oryzae pv. oryzae. The 304-bp PCR product from the rpsL gene was digested by MboII to form two fragments (201 and 103 bp) if there was a mutation at codon 43, or three fragments (146, 103, and 55 bp) if there was no mutation. Compared with the results from nucleotide sequencing, the PCR-RFLP method was accurate in detecting the point mutation at codon 43 of the rpsL gene in streptomycin-resistant strains of X. oryzae pv. oryzicola and X. oryzae pv. oryzae. These results indicate that the PCR-RFLP is a simple, rapid and reliable method for detecting the point mutation at codon 43 of the rpsL gene.