Evaluation of xylem vascular occlusions in olive cultivars infected with Xylella fastidiosa
| Main Authors: | Montilon Vito, Boscia Donato, Savino Vito Nicola, Saldarelli Pasquale, Saponari Maria, De Stradis Angelo |
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| Format: | Proceeding poster Journal |
| Bahasa: | eng |
| Terbitan: |
, 2021
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| Subjects: | |
| Online Access: |
https://zenodo.org/record/4674328 |
Daftar Isi:
- Olive Quick Decline Syndrome (OQDS), caused by the vector transmitted bacterium Xylella fastidiosa (Xf), is the most devastating olive disease in south Apulia. Studies in the Pierce’s Disease grapevine pathosystem indicate that the biofilm-embedded bacteria engulf the xylem conduits thus eliciting the formation of tylose-like structures and gums aiming to isolate the pathogen. We attempted to evaluate the presence of vascular occlusions in diverse Xf-infected olive cultivars and to assess their nature by fluorescence and transmission electron microscopy (TEM). The observations were performed on healthy and Xf-infected twigs of the Cellina di Nardò, Leccino and FS17 cultivars. The percentages of completely occluded vessels were visually determined by fluorescence microscopy on hand made cross-sections of one-year-old olive twigs from artificially pin-pricked infected and mock-inoculated plants grown under controlled conditions. Occlusions were negligible in healthy plants, while significantly higher in Xf-infected plants reaching the highest value (9.65%) in the susceptible cultivar Cellina di Nardò, while these were 6.81% and 1.33% in the Leccino and FS17, respectively. In addition, the distribution of occluded vessels was not uniform among individual twigs of the same cultivars, ranging from 1% to 34% in Cellina di Nardò, 0.044% to 14% in Leccino and 1.09% to 1.53% in FS17. Tissue portions in which occluded vessels were found by fluorescence microscopy, were embedded in resin to be observed by TEM. Thin sections observations showed that the olive response to the Xf infection does not include the production of tylose-like structures. Conversely, the obstructions we seen by fluorescence microscopy are due to bacterial cell aggregates embedded in a hard matrix. Indeed, as observed by the IAWA (International Association of Wood Anatomists) bulletins for taxonomic identification of hardwood species, olive, differently from grapevine, has very small, half-bordered vessel ray and vessel-parenchyma pits which make unlikely the tyloses development.
- IT; PPT; vitomontilon@virgilio.it