Electrical penetration graphs from Cicadulina mbila on maize, the fine structure of its stylet pathways and consequences for virus transmission efficiency

Abstract

Five distinct electrical penetration graph waveforms characterising the feeding behaviour of the leafhopper Cicadulina mbila Naudé (Homoptera: Cicadellidae) on maize (Zea mays L.) were obtained using a DC based system. The waveforms were distinguished by spectral features and by statistical analysis of their median voltages, durations and time to first waveform recording. By changing the polarity of the system voltage and the level of the input resistor it was shown that the waveforms are mainly determined by the electromotive force (emf) component. Based on the correlation between waveforms and the fine structure of the stylet pathways observed by transmission electron microscopy, insect's activities have been associated with five waveforms: stylet pathway formation (waveform 1), active ingestion (waveform 2), putative stylet work (waveform 3), salivation (waveform 4) and passive ingestion (waveform 5). Like waveform E1 and E2 of aphids, waveforms 4 and 5 of C. mbila correspond to feeding activities in sieve tubes. However, unlike aphids which probe briefly in non‐vascular cells, waveform 2 corresponds to active ingestion in cells, where the cell content is partially ingested and hence the organelles' integrity severely affected. These observations suggest that this specific feeding feature, typical of leafhoppers, determines their ability to acquire geminivirus virions located in the plant cell nucleus.

Characterization and Correlation of New Electrical Penetration Graph Waveforms for the Corn Leafhopper (Hemiptera: Cicadellidae)

“…Common characteristics include a short duration of the waveform event (Ϸ1 min), a sudden increase in voltage at the beginning of the waveform, an irregular waveform shape, and high amplitude. Although the term "salivation" was used for this waveform in previous literature (Kawabe 1985, Wayadande andNault 1996), we agree with present consensus that "stylet pathway" describes more precisely the activities related to this waveform that include not only secretion of saliva to facilitate stylet movement through plant tissues but also rupture of cells during probing, and probably also some sampling of cell contents (Helden and Tjallingii 2000, Lett et al 2001, Backus et al 2005.…”

“…This waveform is similar to waveforms related to either "nonsieve element ingestion" in D. maidis (Wayadande and Nault 1996), "xylem ingestion" in N. cincticeps (Kawabe andMcLean 1980, Kawabe 1985) and N. virescens (Rapusas and Heinrichs 1990), and "active ingestion" either from xylem or mesophyll cells by C. mbila (Lett et al 2001). Waveform 2 is similar to those above mentioned waveforms in its waveform sequence after stylet pathway, its regular shape, and its low amplitude.…”

“…WDI, waveform duration per insect (total time an average insect spent in each activity, in minutes); NWEI, number of waveform events per insect (number of times that each waveform was recorded for an average insect (only insects that performed the indicated waveform were included in the analysis); WDEI, waveform duration per event per insect (average duration of each waveform event, in minutes (only insects that performed the indicated waveform were included in the analysis). Nault 1996), Perkinsiella saccharicida Kirkaldy (Chang 1978), Nephotettix cincticeps Uhler (Kawabe and McLean 1980), and Nephotettix virescens (Distant) (Rapusas and Heinrichs 1990), and is also similar to waveform 1 of Cicadulina mbila Naude (Lett et al 2001) and pathway phase waveforms of Homalodisca vitripennis (Germar) (formerly H. coagulata, Backus et al 2005). Common characteristics include a short duration of the waveform event (Ϸ1 min), a sudden increase in voltage at the beginning of the waveform, an irregular waveform shape, and high amplitude.…”

Characterization of EPG waveforms for the tea green leafhopper, Empoasca vitis Göthe (Hemiptera: Cicadellidae), on tea plants and their correlation with stylet activities

“…Waveforms E2 and E3 are similar to waveforms representing active ingestion (especially from xylem) defined for other species, e.g., G waveform in the EPG recording of aphids (Tjallingii, 1988), as well as waveform B produced by Cicadulina mbila on maize (Lett et al, 2001) and waveform C of sharpshooter (Dugravot et al, 2008). The waveforms recorded in our artificial diet experiment were nearly identical in appearance to the above waveforms.…”

“…The waveforms recorded in our artificial diet experiment were nearly identical in appearance to the above waveforms. In active ingestion, the waveforms, whether correlated with stylet tips in xylem or mesophyll, are all characterized by a highly stereotypical pattern at a constant repetition rate of about 4-6 Hz (Lett et al, 2001;Dugravot et al, 2008;Miranda and Fereres, 2009;Stafford and Walker, 2009;Seo et al, 2009;Bonani et al, 2010;Civolani et al, 2011).…”