DsRNAs spray enhanced the virulence of entomopathogenic fungi Beauveria bassiana in aphid control

Aphids are a major group of crop pests, which directly feed on phloem and indirectly transmit plant virus. The entomopathogenic fungi are essential members of green pest control strategies, and insecticidal RNAi is considered as a new generation of biopesticides. However, the effects of combining entomopathogenic fungus and RNAi-based biopesticides for aphid control are unknown. Here, the responsive genes of Acyrthosiphon pisum were screened from the transcriptomes upon spraying of Beauveria bassiana Bb07 strain (hereafter referred to Bb07). Subsequently, six candidate genes, Ap4714, Ap15782, Ap20844, Ap14741, Ap15105 and Ap16968, were targeted by spray-based RNAi, which produced a range of 20.0, 58.0, 44.0, 27.0, 52.0 and 24.0% gene silencing, respectively. Silencing of single-target (Ap4714, Ap15782, and Ap20844) resulted in increased virulence of Bb07 to Ac. pisum. Importantly, the mortality was increased to 82.1, 76.7, and 60.7% within 7 days to Ac. pisum when double-targets (Ap4714 + Ap15782, Ap4714 + Ap20844 and Ap15782 + Ap20844) were silenced in together with application of Bb07, respectively. This high mortality was also observed in Myzus persicae and Aphis citricidus by co-spray of the combination of dsAp4714 + dsAp15782 together with Bb07. In together, this study demonstrates the potential of a combination of RNAi- and entomopathogenic fungus-based technologies to control aphids, thereby reducing application of chemical pesticides.