The extent of damage to crop plants from pest insects depends on the foraging behaviour of the insect's feeding stage. Little is known, however, about the genetic and molecular bases of foraging behaviour in phytophagous pest insects. The foraging gene (for), a candidate gene encoding a PKG-I, has an evolutionarily conserved function in feeding strategies. Until now, for had never been studied in Lepidoptera, which includes major pest species. The cereal stem borer Sesamia nonagrioides is therefore a relevant species within this order with which to study conservation of and polymorphism in the for gene, and its role in foraging -a behavioural trait that is directly associated with plant injuries. Full sequencing of for cDNA in S. nonagrioides revealed a high degree of conservation with other insect taxa. Activation of PKG by a cGMP analogue increased larval foraging activity, measured by how frequently larvae moved between food patches in an actimeter. We found one non-synonymous allelic variation in a natural population that defined two allelic variants. These variants presented significantly different levels of foraging activity, and the behaviour was positively correlated to gene expression levels. Our results show that for gene function is conserved in this species of Lepidoptera, and describe an original case of a single nucleotide polymorphism associated with foraging behaviour variation in a pest insect. By illustrating how variation in this single gene can predict phenotype, this work opens new perspectives into the evolutionary context of insect adaptation to plants, as well as pest management.
The olive fruit fly, Bactrocera oleae (Tephritidae), is a direct pest of olives that has invaded the Mediterranean Region and California. Psyttalia lounsburyi (Braconidae), a larval parasitoid from Africa, has been approved for release in the USA as a classical biological agent. However, it has been difficult to rear the parasitoid in the laboratory because it is multivoltine, and the host develops only in fresh olives, which are not available for most of the year. A method to rear the parasitoid on the factitious host, Mediterranean fruit fly (Ceratitis capitata) was developed, but it was not very efficient for producing large numbers of parasitoids needed for release. We developed a number of ways to improve the efficiency of rearing, including the frequency and duration of exposure for oviposition, optimizing the density of adult parasitoids, host age, as well as methods to quickly standardize the number of larvae exposed and to count emerging adult parasitoids. We significantly improved the number of progeny produced per female and the sex ratio of progeny. Thanks to these improvements, we produced in 2017 over 119,000 adults and shipped over 53,900 for release in California.
This is an open access article under the terms of the Creat ive Commo ns Attri bution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.