Transfer of Cry1F from Bt maize to eggs of resistant Spodoptera frugiperda

Abstract

The intergenerational transfer of plant defense compounds by aposematic insects is well documented, and since 2006, has been shown for Cry toxins. Cry toxins are proteins naturally produced by the soil bacterium Bacillus thuringiensis (Bt) and its genes have been expressed in plants to confer insect pest resistance. In this work we tested if non-aposematic larvae of a major maize pest, Spodoptera frugiperda, with resistance to Cry1F, could transfer Cry1F from a genetically engineered maize variety to their offspring. Resistant 10-day-old larvae that fed on Cry1F Bt maize until pupation were sexed and pair-mated to produce eggs. Using ELISA we found that Cry1F was transferred to offspring (1.47-4.42 ng Cry1F/10 eggs), a toxin concentration about 28-83 times less than that detected in Cry1F Bt maize leaves. This occurred when only one or both sexes were exposed, and more was transferred when both parents were exposed, with transitory detection in the first five egg masses. This work is an unprecedented demonstration that a non-aposematic, but resistant, species can transfer Cry1F to their offspring when exposed to Bt host plant leaves as immatures.

Fig 1. Cry1F concentration (ng/10 eggs ± 95% CI) detected in Spodoptera frugiperda eggs when parents were exposed or not to Cry1F as larvae from ten days after eclosion until pupation (n = 10 couples/treatment).

Treatment x day of oviposition effect: F_12,144 = 5.17, P = 3.57 x 10⁻⁷. Means for the treatment x day of oviposition interaction followed by the same letter did not differ according to the Tukey’s HSD test.