Eucalyptus occidentalis plantlets are naturally infected by pathogenic Agrobacterium tumefaciens

Springer Science and Business Media LLC - Tập 116 - Trang 237-246 - 2006
Zoulikha Krimi1, Aïda Raio2, Annik Petit3, Xavier Nesme4, Yves Dessaux3
1Laboratoire de Phytobactériologie, Faculté des Sciences Agronomiques et Vétérinaires, Université de Blida, Blida, Algérie
2Instituto per la Protezione delle Piante – CNR, Portici, Napoli, Italy
3Institut des Sciences du Végétal, UPR 2355 CNRS, Gif-sur-Yvette Cedex, France
4UMR CNRS 5557 Ecologie Microbienne and USC INRA 1193, IFR41 Bio-Environnement et Santé, Villeurbanne Cedex, France

Tóm tắt

In the Sidi M’djahed nursery (Algeria), over 60,000 eucalyptus (Eucalyptus occidentalis) plantlets exhibited tumour-like growths localized at the crown of the plants that resembled crown galls caused by Agrobacterium tumefaciens. Bacteria colonizing the galls were isolated and purified. Most (22 out of 24) of the isolates had cultural and biochemical characteristics similar to those of strains of the biovar 1 of A. tumefaciens. Twenty out of 22 Agrobacterium isolates induced tumour formation on various test plants. In PCR experiments, DNA extracted from these virulent strains yielded an amplification signal corresponding to a 247-bp fragment located within the virulence region of nopaline type Ti plasmid. Consistent with this, the opine nopaline was detected in the tumours induced on test plants – but not on eucalyptus plants. Nopaline was degraded by the 20 pathogenic isolates that were also sensitive to agrocin 84, indicating the presence of a nopaline-type pTi in these strains. The chromosomal region encoding the 16S rRNA was analyzed in a sub-population of the pathogenic agrobacterial isolates. The analyzed strains were found to belong to the ribogroup of the reference strain B6. Interestingly, Eucalyptus camaldulensis and Eucalyptus cladocalyx grown in the same nursery and in the same soil substrate developed no galls.

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