Diversidade genetica em linhagens de Xylella fastidiosa isoladas de citros

AUTOR(ES)
DATA DE PUBLICAÇÃO

2000

RESUMO

Xylella fastidiosa is a Gram-negative bacterium associated to diseases in many economically important crops such as grapevine, citrus, coffee and plum. In this study, the genetic relationships among X. fastidiosa strains isolated from citrus in different geographic regions of Brazil was investigated. Strains isolated from coffee, grapevine, plum and pear were also included for comparison. The genetic diversity was investigated using molecular techniques including amplification of DNA using the primers ERIC, REP and BOX (rep-PCR), RFLP of the 16S rDNA and 16S-235 intergenic spacer, RAPD and SDS-PAGE of proteins. RFLP of the 16S rDNA and 165-235 intergenic spacer revealed a low levei of polymorphism. The RAPD and rep PCR techniques showed a higher level of polymorphism, demonstrating the relationships of strains with the hosts and the variation among the citrus strains. Citrus strains isolated from the Southern States including Rio Grande do Sul, Santa Catarina and Paraná, formed one group, whereas strains isolated from the States of São Paulo and Sergipe formed another group. The analysis of the protein profiles obtained by SDS-P AGE also showed a relationship between strains and their hosts. The pear strain was distantly related to the other strains of X. fastidiosa in all the techniques used. DNA:DNA hybridization revealed a homology above 80% for the strains solated from grapevine, plum, citrus and coffee, showing that these strains belong to the same genomic species. The pear strain presented a homology leveI below 20%, indicating that this strain does not belong to the genomic species X. fastidiosa. The phylogenetic relationships among strains from different hosts was assessed by sequence analysis of the 165 rDNA and 16S-23S intergenic spacer. The phylogenetic trees obtained revealed two major c1usters: the citrus, coffee and plum strains formed one cluster, distinct from that formed by the grapevine strains

ASSUNTO(S)

filogenia bacterias fitopatogenicas

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