A novel Bacillus thuringiensis Cry9Ea-like protein with high insecticidal activity towards Cydia pomonella larvae

The host specificity of known Bacillus thuringiensis Cry and Vip pesticidal proteins still needs extensive investigation and the proteins currently used in crop protection are not effective against many pest species. Cydia pomonella (L.) is a widespread and economically important pest of apples, very difficult to control, since the larvae spend most of their life inside a fruit. Currently, large amounts of broad-spectrum, detrimental synthetic agents are used to combat this herbivore and therefore biopesticides with high activity against C. pomonella are very much needed.

The toxicity of B. thuringiensis Cry9Ea along with five distinct pesticidal proteins (Cry1Aa, Cry1Ca, Cry1Ia, Cry2Ab and Vip3Aa) has been determined towards the first-instar larvae of C. pomonella. Cry9Ea has much higher activity than the remaining tested proteins (30-1200-fold lower LC₅₀ ) and possibly is the most potent B. thuringiensis pesticidal protein bioassayed against C. pomonella so far. In contrast, Cry9Ea is not toxic towards Spodoptera exigua (Hübn.), indicating a potentially narrow spectrum of activity. Both insect species show high variability in susceptibility to the remaining Cry/Vip proteins.

The obtained results extend the existing knowledge regarding B. thuringiensis pesticidal protein host range and indicate Cry9Ea as a promising candidate for successful biological control of C. pomonella. © 2020 Society of Chemical Industry.