Inoculation of Nicotiana tabacum with recombinant potato virus X induces RNA interference in the solenopsis mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae)

The chitin synthase 1 (CHS1) gene in Phenacoccus solenopsis (PsCHS1) was evaluated as a potential target of RNA interference (RNAi) by using Potato virus X (PVX) as a vector (recombinant PVX) for expressing RNAi triggering elements in Nicotiana tabacum L. RT-PCR analysis confirmed the expression of PsCHS1 in N. tabacum inoculated with recombinant-PVX-PsCHS1 (treated). RT- and multiplex-PCR further showed a reduction in mRNA levels of the target gene in mealybugs feeding on treated plants. Mortality in parent adults and emerging nymphs (21 and 29 %) exposed to the treated plants was significantly higher (P < 0.05) than those exposed to uninoculated (-ve control) or inoculated with non-recombinant PVX (PVX-control). The number of surviving adults and the combined number of adults and nymphs (47 and 60 %) was significantly (P < 0.05) lower on the treated plants than the -ve (76 %) or PVX (74 %) control. The visual observations verified the physical deformities in mealybugs exposed to the treated plants. chitin synthase 1 is a potential RNAi target in P. solenopsis and the recombinant PVX can be used as a tool to evaluate candidate RNAi triggering elements in plants.