2.1. Plants, Insects and Virus

Tobacco seeds (N. tabacum cv. Xanthii) were placed in a germination container with autoclaved potting soil. Seedlings at the three-leaf stage were individually transferred into pots (7 × 7 × 7 cm³) and stored in a growth chamber at 22 ± 1 °C, with 70 ± 10% relative humidity (RH) and a 16 h light period.

A colony of an MpCh4 strain of M. persicae was maintained on tobacco plants in 60 × 60 × 60 cm³ net cages (Bugdorms, MegaView Science Co., Taichung City, Taiwan) and placed in air-conditioned rooms as described above. Plants were replaced every 3 weeks by four-leaf stage seedlings.

Potato leafroll virus was acquired from infected Physalis floridana Rydb. from DSMZ (Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH, Braunschweig, Germany). It was then transferred on tobacco plants by releasing five M. persicae previously virosed on P. floridana for 4 days. Similarly, PLRV was maintained by transferring insects from virus-infected tobacco to new healthy seedlings every 3–4 weeks.