Scaphoideus titanus Ball (Hemiptera: Cicadellidae) is the main vector of grapevine’s “Flavescence dorée” (FDP) phytoplasmas (16SrV, subgroups C and D). According to the state-of-art, nymphs acquire phytoplasmas from infected plants within a few days (acquisition access period, AAP), and undergo a latency period (LP) lasting 3-5 weeks. Afterwards the insects, meanwhile having mutate to adults, are able of infecting new plants following and inoculation access period (IAP) of a few days. However, some aspects of FDP epidemics suggest that adults may also acquire directly phytoplasmas and become infective within their lifespan. Therefore, transmission experiments have been carried out under lab conditions, using broad bean plants (Vicia faba L.) artificially infected with 16SrV-C phytoplasmas as a source of inoculum. Uninfected S. titanus adults were allowed to feed for 7 days (AAP) on infected plants. Afterwards, three inoculations on healthy broad beans were performed at 7 days intervals each (IAPs). At the end of each IAP, insects were moved on a new plant. Therefore, IAP 1, IAP 2 and IAP 3 lasted 7, 14 and 21 days from the end of AAP, respectively. Phytoplasma were identified in plants and insects by DNA extraction and PCR. Some insects were also dissected and fluorescent in situ hybridization was made to detect the presence of phytoplasmas in midguts and salivary glands. Infection in insects and plants ranged 46-68% and 16-23%, respectively. Neither showed significant differences among IAPs, whereas phytoplasma load was significantly higher in IAP3 for both plants and insects. Phytoplasmas were identified in both midgut and salivary glands. The whole transmission process has been therefore successful within just 14 days (AAP=7 + IAP=7). These new insights are consistent with severe FDP outbreaks at the end of the summer in grapevine growing areas, and may call for new pest management strategies against S. titanus.
Acquisition and inoculation of FD phytoplasmas by adults of Scaphoideus titanus Ball: less time is required / Alma, Alberto; Lessio, Federico; Gonella, Elena; Picciau, Luca; Mandrioli, Mauro; Tota, Federico. - (2018). (Intervento presentato al convegno XI EUROPEAN CONGRESS OF ENTOMOLOGY tenutosi a Napoli nel 2-6 luglio 2018).
Acquisition and inoculation of FD phytoplasmas by adults of Scaphoideus titanus Ball: less time is required
Mauro Mandrioli;
2018
Abstract
Scaphoideus titanus Ball (Hemiptera: Cicadellidae) is the main vector of grapevine’s “Flavescence dorée” (FDP) phytoplasmas (16SrV, subgroups C and D). According to the state-of-art, nymphs acquire phytoplasmas from infected plants within a few days (acquisition access period, AAP), and undergo a latency period (LP) lasting 3-5 weeks. Afterwards the insects, meanwhile having mutate to adults, are able of infecting new plants following and inoculation access period (IAP) of a few days. However, some aspects of FDP epidemics suggest that adults may also acquire directly phytoplasmas and become infective within their lifespan. Therefore, transmission experiments have been carried out under lab conditions, using broad bean plants (Vicia faba L.) artificially infected with 16SrV-C phytoplasmas as a source of inoculum. Uninfected S. titanus adults were allowed to feed for 7 days (AAP) on infected plants. Afterwards, three inoculations on healthy broad beans were performed at 7 days intervals each (IAPs). At the end of each IAP, insects were moved on a new plant. Therefore, IAP 1, IAP 2 and IAP 3 lasted 7, 14 and 21 days from the end of AAP, respectively. Phytoplasma were identified in plants and insects by DNA extraction and PCR. Some insects were also dissected and fluorescent in situ hybridization was made to detect the presence of phytoplasmas in midguts and salivary glands. Infection in insects and plants ranged 46-68% and 16-23%, respectively. Neither showed significant differences among IAPs, whereas phytoplasma load was significantly higher in IAP3 for both plants and insects. Phytoplasmas were identified in both midgut and salivary glands. The whole transmission process has been therefore successful within just 14 days (AAP=7 + IAP=7). These new insights are consistent with severe FDP outbreaks at the end of the summer in grapevine growing areas, and may call for new pest management strategies against S. titanus.
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