Morphological and molecular characterization of Brazilian populations of Diatraea saccharalis (Lepidoptera: Crambidae) and the evolutionary relationship among Diatraea spp.

Authors: FRANCISCHINI, FABRICIO - Universidade De Campinas (UNICAMP); DE CAMPOS, JAQUELINE - Universidade De Campinas (UNICAMP); PEREIRA, ALLESSANDRO - Universidade De Campinas (UNICAMP); VIANA, JOAO PAULO - Universidade De Campinas (UNICAMP); GRINTER, CHRISTOPHER - University Of Illinois; Clough, Steven; ZUCCHI, MARIA - Agencia Paulista De Tecnologia Dos Agronegocios/saa-Sp

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/29/2017
Publication Date: 11/16/2017
Citation: Francischini, F.J., De Campos, J.B., Pereira, A.A., Viana, J.G., Grinter, C.C., Clough, S.J., Zucchi, M.I. 2017. Morphological and molecular characterization of Brazilian populations of Diatraea saccharalis (Lepidoptera: Crambidae) and the evolutionary relationship among Diatraea spp. PLoS One. 12(11):e0186266.

Interpretive Summary: The corn borer/sugarcane borer (in the genus Diatraea) is an important pest of corn and sugarcane. Feeding by these insects creates long tunnels through plant stalks, weakening the stalks and providing gateways and passages for opportunistic pathogens that can further damage the crops. The lack of information about Diatraea populations is a huge problem for adopting broadly effective control measures. For example, little is known about which Diatraea species infest corn and sugarcane fields in Brazil, their population structures, or the evolutionary relationships among Diatraea populations and species. In this study, we collected specimens of Diatraea in the main corn and sugarcane production regions in Brazil and we classified the insects based on classical morphological characteristics and modern molecular techniques. We discovered that there are two species (and only two) of Diatraea that infest corn and sugarcane in Brazil. We also found that the Diatraea species showed feeding preferences that could be related to the fragmentation of crop production regions in Brazil. The findings show the need to take into account local population structures in the adoption of control measures. Farmers, seed producers and researchers will benefit from these findings.

Technical Abstract: The sugarcane borer (or corn stalk borer), is a Diatraea ssp., polyphagous insect pest of important crops such corn, sorghum and sugarcane. Losses arising from attack of Diatraea species can be signigficant, with reductions of up to 0.25% in sugar, 0.20% in alcohol, and 0.77% of plant biomass for every 1% infestation. Losses in corn production can be up to 21%. In Brazil, the most common species are Diatraea saccharalis (Fabricius, 1794) and Diatraea flavipennella (Box, 1931). However, multiple other species of Diatraea have been identified in Brazil according to the literature. Currently, little information exists on the presence of other species causing injury to sugarcane and corn, and assume that it is only Diatraea saccharalis infesting sugarcane. The objectives of this study were to improve the accuracy of species assignment, establish a representative population genetic structure, and resolve many of the outstanding questions of systematics and evolution of Diatraea ssp. To solve these main questions, classical taxonomic methods were used, focused on morphological characterization of the reproductive organs, especially the male genitalia. Furthermore, genetic studies were performed using molecular markers for the mitochondrial cytochrome oxidase I gene (COI) and simple sequence repeats (SSR). The analysis of the COI sequence is a powerful tool for insect phylogenetics, while the determination of DNA SSRs can help clarify and expedite delimitation of species groups within a defined region. Using these techniques on caterpillars feeding in different regions, and on different host plants, permitted analysis of the structure of genetic diversity among populations. The data and findings from this research project will refine the understanding of evolutionary aspects of insect pests in order to develop more effective and sustainable population management practices. In addition, we suggest the adoption of a nomenclatural change, using Diatraea impersonatella instead of Diatraea flavipennella.