There is little information available on the biology of the transmission of Xylella fastidiosa by Philaenus spumarius and the most widespread European sharpshooter, Cicadella viridis. Although the role of the meadow spittlebug, P. spumarius, in the transmission of X. fastidiosa subsp. pauca ST53 to olive, periwinkle, oleander and Polygala myrtifolia has been proven, the description of vectors' acquisition, persistence and transmission characteristics has not been described so far. A deep knowledge of transmission parameters is of key importance to shed light on the epidemiology of this invasive bacterium and emerging associate diseases in the Old World. For this reason, two sets of experiments have been performed, in order to describ (i) the kinetics of the bacterial multiplication and persistence in the spittlebug P. spumarius and in the sharpshooter C. viridis; (ii) the influence of environmental factors (temperature, season) and insect age on simulated epidemics progression on olive plants under controlled and natural climatic conditions (indoor-outdoor). Both experiments have repeated in 2017 and 2018, twice a year (June-July and September-October). Insects used for acquisition were collected in Xf-free areas, whereas naturally infected olives and needle- inoculated periwinkle were used as source of inoculum. For the kinetics experiments, after an acquisition access period (AAP) of 72h, insects were transferred in groups of five, at different times post-acquisition on olive or periwinkle test plants for an inoculation access period of 72h. In the second sets of experiments, after the AAP groups of insects were isolated in cages with 16 olive seedlings for 3, 7, 14 and 21 days' inoculation periods. Acquisition and transmission rates were assessed by testing individual insects recovered after the IAP and by testing all recipient plants 6 and 10 months after the inoculations. Although the results from 2018 have to be collected yet, preliminary results from 2017 indicate for P. spumarius: a) an higher acquisition efficiency in September as compared to July; b) a lower acquisition efficiency when periwinkle was used as source plant compared to olives, conversely transmission was higher on periwinkle plants compared to olives. Very low acquisition efficiency and no transmission ability were recovered for C. viridis. Experiments are still ongoing, and preliminary results need to be confirmed by 2018 assays. Because of the negative results obtained so far with C. viridis, in the last set of experiments (conducted on September-October 2018) we applied an in vitro acquisition system for X. fastidiosa ST53 for the sharpshooter. The results will be available soon.
Preliminary results on the transmission characteristics of Xylella fastidiosa subsp. pauca (ST53) by Philaenus spumarius and Cicadella viridis
Bodino N;Cavalieri V;Altamura G;Zicca S;Saponari M;Bosco D
2018
Abstract
There is little information available on the biology of the transmission of Xylella fastidiosa by Philaenus spumarius and the most widespread European sharpshooter, Cicadella viridis. Although the role of the meadow spittlebug, P. spumarius, in the transmission of X. fastidiosa subsp. pauca ST53 to olive, periwinkle, oleander and Polygala myrtifolia has been proven, the description of vectors' acquisition, persistence and transmission characteristics has not been described so far. A deep knowledge of transmission parameters is of key importance to shed light on the epidemiology of this invasive bacterium and emerging associate diseases in the Old World. For this reason, two sets of experiments have been performed, in order to describ (i) the kinetics of the bacterial multiplication and persistence in the spittlebug P. spumarius and in the sharpshooter C. viridis; (ii) the influence of environmental factors (temperature, season) and insect age on simulated epidemics progression on olive plants under controlled and natural climatic conditions (indoor-outdoor). Both experiments have repeated in 2017 and 2018, twice a year (June-July and September-October). Insects used for acquisition were collected in Xf-free areas, whereas naturally infected olives and needle- inoculated periwinkle were used as source of inoculum. For the kinetics experiments, after an acquisition access period (AAP) of 72h, insects were transferred in groups of five, at different times post-acquisition on olive or periwinkle test plants for an inoculation access period of 72h. In the second sets of experiments, after the AAP groups of insects were isolated in cages with 16 olive seedlings for 3, 7, 14 and 21 days' inoculation periods. Acquisition and transmission rates were assessed by testing individual insects recovered after the IAP and by testing all recipient plants 6 and 10 months after the inoculations. Although the results from 2018 have to be collected yet, preliminary results from 2017 indicate for P. spumarius: a) an higher acquisition efficiency in September as compared to July; b) a lower acquisition efficiency when periwinkle was used as source plant compared to olives, conversely transmission was higher on periwinkle plants compared to olives. Very low acquisition efficiency and no transmission ability were recovered for C. viridis. Experiments are still ongoing, and preliminary results need to be confirmed by 2018 assays. Because of the negative results obtained so far with C. viridis, in the last set of experiments (conducted on September-October 2018) we applied an in vitro acquisition system for X. fastidiosa ST53 for the sharpshooter. The results will be available soon.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
