Probing behavior of the leafhopper analyzed through DC electropenetrography and microscopy

Yamatotettix flavovittatus Matsumara is a new leafhopper species vector of sugarcane white leaf (SCWL) phytoplasma that causes sugarcane chlorosis symptoms. The effects of probing behavior of Y. flavovittatus on sugarcane and its implication for SCWL phytoplasma transmission are yet to be studied. In this research, we used DC electropenetrography (EPG) to define waveforms produced by adult and fifth-instar nymphal Y. flavovittatus on sugarcane and correlated them with salivary sheath termini (likely stylet tip locations) via light and scanning electron microscopy. The following six waveforms and associated activities are described: (NP) non-probing, (Yf1) stylet probing into epidermal cells, (Yf2) stylet probing through mesophyll/parenchyma, (Yf3) stylet contact with phloem and likely watery salivation, (Yf4) active ingestion of sap from phloem, probably sieve elements, and (Yf5) unknown stylet activity in multiple cell types. Study findings reveal that the Y. flavovittatus vector ingests sieve tube element more frequently and for longer durations than any other cell type, supporting that Y. flavovittatus is primarily a phloem feeder. Adult Y. flavovittatus show a longer total probing duration and produces a high density of puncture holes on sugarcane leaves. Moreover, probing behaviors revealed that adults typically ingest phloem sap more frequently and for longer durations than fifth-instar nymphs, enhancing sap ingestion. Furthermore, we propose that adults are more likely to acquire (during Yf4) and inoculate (during Yf3) higher amounts of phytoplasma than fifth-instar nymphs. This information on the penetration behavior of leafhopper Y. flavovittatus serves as a basis for advanced studies on the transmission mechanism of SCWL phytoplasma.