Candidatus Liberibacter solanacearum: detection, characterization, new hosts and epidemiology in Spain
- Autores: Gabriela Ribeiro Teresani
- Directores de la Tesis: Mariano Cambra Alvarez (dir. tes.), María Milagros López González (dir. tes.), Edson Bertolini (dir. tes.)
- Lectura: En la Universitat Politècnica de València ( España ) en 2014
- Idioma: inglés
- Tribunal Calificador de la Tesis: Ferrán García Marí (presid.), Antonio de Vicente Moreno (secret.), Collin Jeffries (voc.)
- Materias:
- Enlaces
- Tesis en acceso abierto en: RiuNet
- Resumen
`Candidatus Liberibacter solanacearum¿ is a ¿-Proteo bacterium that is Gram-negative and restricted to the plant phloem and to the hemolymph of psyllids and that acts as vectors. This emerging bacterium has been associated with different diseases in different hosts and associated with carrot (Daucus carota) in Spain. Vegetative disorders of unknown etiology have also been observed in celery (Apium graveolens) since 2008. A real-time PCR protocol that was specific to `Ca. L. solanacearum¿ detection, using a TaqMan probe and direct sample preparation methods was developed. This technology was validated in an intra-laboratory study (sensitivity 1, specificity 1 and accuracy 100%) and is available commercially as a complete kit. `Ca. L. solanacearum¿ is associated with the observed syndrome in celery, and a new bacterium haplotype (E) has been identified. With these results, it is concluded that celery is a new host of `Ca. L. solanacearum¿ (Teresani et al., 2014a). Using the newly developed real-time PCR protocol, `Ca. L. solanacearum¿ has been detected in 42.6% of the tested carrot seeds lots and in individual seeds. The number of cells/seeds has been estimated at 4.8±3.3 to 210±6.7, of which only 5% were viable. After 150 days post-germination, 12% of the seedlings showed symptoms and tested positive for `Ca. L. solanacearum¿. Liberibacter-like cells were observed in the phloem sieve elements of the seed coat and in the phloem of the carrot leaf midrib from the seedlings. These results demonstrate that `Ca. L. solanacearum¿ is transmitted by carrot seeds (Bertolini et al., 2014b). The collected arthropods were classified into families, and the superfamily Psylloidea was identified at the species level, mainly Bactericera trigonica, B. tremblayi and B. nigricornis. The population dynamics of different psyllids species visiting carrot, celery and potato has been determined, concluding that the largest populations are captured during summer. The bacterium has been detected in the different Bactericera species that have been previous cited in addition to Bactericera sp. The psyllid species carrying the bacteria can be considered possible vectors of the bacterium (Teresani et al. 2014b). Electrical Penetration Graphs showed that B. trigonica was able to feed in the phloem of carrot, celery and potato but not in the phloem of tomato plants. Experimental transmission showed that B. trigonica transmitted `Ca. L. solanacearum¿ from carrot to carrot, celery, potato and tomato. More efficient transmission occurred with ten individuals, and the transmission rates were 100% in celery, 80% in carrot and 10% in potato and tomato. The experimental transmission to potatoes threatens this crop (Teresani et al., 2014c). These combined results have built a scientific foundation of the biological and epidemiological aspects of `Ca. L. solanacearum¿ contributing new scientific information that is key in the cultivation of celery and carrot to establish bacterial control strategies. The use of bacteria-free carrot seed lots will definitely mitigate damage and reduce the risks of transmission to solanaceous crops.
