Summary auto-generated
This 2001 study analyzed phylogenetic relationships among Xylella fastidiosa strains isolated from different host plants using 16S rDNA and 16S–23S intergenic spacer sequencing. Eleven strains from citrus, coffee, grapevine, plum, and pear were examined. The 16S rDNA showed high sequence conservation with 97.1–100% similarity among strains. The 16S–23S spacer region displayed greater variation, ranging from 79.8–100% similarity. Phylogenetic analysis grouped citrus, coffee, plum, and peach strains together and separately from grapevine strains. Notably, the pear strain (PE.PLS) diverged significantly from all other Xylella fastidiosa strains. DNA–DNA hybridization confirmed this distinction, showing the pear strain had less than 20% homology with a citrus strain, compared to 85–140% homology among other strains. The researchers concluded that the pear strain does not belong to the Xylella fastidiosa genomic species, suggesting it may represent a separate species within the Xylella genus.
Key findings
- 16S rDNA sequences showed 97.1–100% similarity among Xylella fastidiosa strains, while the more variable 16S–23S spacer region showed 79.8–100% similarity
- Phylogenetic analysis grouped citrus, coffee, plum, and peach strains together, separate from grapevine strains
- The pear strain (PE.PLS) was phylogenetically distinct from all other Xylella fastidiosa strains in both molecular analyses
- DNA–DNA hybridization revealed the pear strain had less than 20% homology with other Xylella fastidiosa strains, versus 85–140% among strains from other hosts, indicating it does not belong to the Xylella fastidiosa genomic species
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Abstract
A Mehta and YB Rosato
Centro de Biologia Molecular e Engenharia Genetica (CBMEG), Universidade Estadual de Campinas (UNICAMP), Cidade Universitaria, PO Box 6010, 13083-970, Campinas, SP, Brazil
The phylogenetic relationships of Xylella fastidiosa strains isolated from different hosts, including citrus trees, coffee, grapevine, plum and pear, were inferred by sequence analysis of the 16S rDNA and 16S--23S intergenic spacer region. A high level of similarity (97.1--100%) was found in the 16S rDNA of the Xylella fastidiosa strains. The 16S--23S region showed a higher level of variation, with similarity values ranging from 79.8 to 100%. Two tRNAs (tRNA(Ala) and tRNA(Ile)) were encountered within the spacer sequence. The phylogenetic trees, constructed using the neighbour-joining method, showed that the citrus, coffee, peach and plum strains were closely related and separate from grapevine strains. The pear strain remained isolated from all the other Xylella strains in both analyses and produced values of less than 20% in DNA--DNA hybridization experiments with a citrus strain. These results show that this strain does not belong to the Xylella fastidiosa genomic species.