Suchergebnisse

The long latency period of X. fastidiosa for the majority of perennial hosts, such as citrus and olive, makes difficult the advance of plant-pathogen studies. Therefore the use of susceptible model plants is required. In this work we show the results of infection and symptoms of the tobacco varieties Havana and RP1, inoculated with three Sequence Types (ST) of X. fastidiosa subsp. pauca (ST13, ST16, and ST53). Eighty days after inoculation the percentage of infected plants was 100% in Havana and RP1 inoculated with ST13 (9a5c citrus-strain). With the ST16 (MF01- olive strain from Brazil), the percentage was 83% in Havana and 100 % in RP1. The lowest percentage of infection was observed with ST53 (CoDiRO strain) with 55 and 78% for Havana and RP1, respectively. Symptoms of small dark lesions surrounded by yellowing at margins were observed only for the ST13 colonizing either Havana or RP1. Significant reduction in plant size and development were observed for all strains infecting both varieties, but more significantly for RP1. In addition, leaf-yellow blotches between secondary veins were mainly observed on RP1 but with gradual intensity (more to less) when the plants were infected with the ST13, ST16 and ST53, respectively. These results demonstrated that tobacco is a good model plant for X. fastidiosa subsp. pauca, although different varieties could show different level of infection and symptoms. In this work we verified that both varieties were good hosts for ST13, but RP1was better for ST16 and ST53. ; Acknowledgment This work has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement N. 727987 "Xylella fastidiosa Active Containment Through a multidisciplinary-Oriented Research Strategy XF-ACTORS" and FAPESP-Sao Paulo State Research Foundation (Proj. # 2013/10957-0)

So far no effective field applicable therapeutic strategy exists to combat the severe diseases associated to X. fastidiosa. Therefore, various experimental applications to seek for a sustainable approach for the mitigation of the impact of the infections on olive trees were explored. In 2015-2016, four field trials were set in the infected area in southern Italy: (i) trial 1 consisted of an olive grove with medium to high incidence of disease symptoms; (ii) trials 2 and 3 consisted of olive groves with very low incidence of infected and symptomatic trees and (iii) trial 4 was a new plantation with 3-years old Xylella-free olive plants. Applications included (i) different elicitors of plant resistance (fosetyl aluminium, acibenzolar-S-methyl, COS-OGA, σ–β Hairpin proteins, cerevisanae) and (ii) Nacetylcysteine (NAC), a mucolytic agent previously showed to have a beneficial impact in reducing symptoms associated to X. fastidiosa in citrus (1). Periodic surveys included (i) sampling for laboratory tests to determine the incidence of the infections; (ii) symptom scoring using 0-5 empirical scale of severity. The overall results showed that only the treatments with NAC, through endotherapy and/or complexed to organic substances added to the soil, determined a noticeable amelioration of the symptoms. None of the elicitors produced any measurable positive impact on the diseased trees. These preliminary encouraging results, prompted for further targeted experiments currently ongoing. ; Acknowledgment This work has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement N. 635646 "Pest Organisms Threatening Europe POnTE" and from the Project T.A.P.A.S.S. (Tecnologie Abilitanti per Produzioni Agroalimentari Sicure e Sostenibili), Regione Puglia, Cluster Tecnologici Regionali.