Genetic diversity of Xanthomonas campestris pv. campestris in Brazil / Diversidade genética de Xanthomonas campestris pv. campestris no Brasil

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

Brazilian and foreign isolates of Xanthomonas campestris pv. campestris (Xcc), as well as a foreign strain of X. campestris pv. armoraciae were studied regarding their phenotipic and genotipic variability by metabolic analysis (BiologTM), fatty acids methyl ester (FAME), pulsed field gel electrophoresis (PFGE) and inoculation in differential series. Results showed that identification of a same strain may vary depending on which system is used as 58% of all strains tested were identified differently by comparing Biolog and FAME results. Xanthomonas campestris pv. armoraciae is not present in Biolog database and the isolates were identified as X. campestris pv. campestris (70%), X. campestris pv. raphani (19%), X. axonopodis pv. malvacearum (5,5%) and X. axonopodis pv. phaseoli (5,5%). FAME identified the isolates as X. campestris pv. raphani (46%), X. campestris pv. campestris (30%), X. campestris pv. armoraciae (11%), X. campestris pv. zinniae (11%) and Stenotrophomonas maltophilia (2%). Both techniques delivered preciser results when identification of a less specificity level was recquired (from gender to patovar). One or both tecquinies can be used as auxiliary systems to identify plant pathogenic bacteria, but should be combined with host range tests, specially if the identification is being made to patovar level. In order to reduce erros, the systems databases could be divided, e.g. according to host. As patovars campestris, raphani and armoraciae are able to infect brassica plants, a broad study of brassica plants and corresponding X. campestris patovars should be made in order to stablish a more consistent classification. All strains used 14 carbon sources in Biolog. Asparagine was not used by any strain while sacarose was not used by some. Strain made six different groups by FAME. Genetic variability of brazilian strains was observed in PFGE with 11 different band patterns formed when restriction enzyme XbaI was used and 12 band patterns when SpeI was used. Foreign strains formed seven band patterns no matter which enzyme was used. A comparative association was made between some of FAME and PFGE groups. Insuficient space on the banchs due to an exceedingly number of plants, which may have cause cross contamination, was probably one of the causes of inconsistent results from greenhouse experiments. Despite that, it was observed virulence variation among the strains when inoculated in plants from the differential series and atypical symptoms were observed, e.g. blight, which could be an evidence of a different X. campestris patovar. A differential series made only with Brassica oleracea species would be interesting. It was also observed a reaction similar to Vascular Hypersensitive Response, which might be an interesting subject to epidemiolgy of black rot and breeding for resistance to Xcc.

ASSUNTO(S)

fitopatologia brassicas brassicas black rot podridão negra fitobactérias phytopathogenic bacteria

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