Genetic Diversity and Population Structure of Dalbulus maidis (Hemiptera: Cicadellidae) in South America.

Abstract

The corn leafhopper, Dalbulus maidis (Hemiptera: Cicadellidae) and its associated corn diseases are considered the main production drawback currently faced by maize growers across South America, especially in Brazil. Native to Mexico and historically restricted to tropical America, the species has recently increased its occurrence in temperate areas of the continent, raising the need for a deeper understanding of the genetic basis driving its population dynamics. In this study, we used the partial mitochondrial DNA cytochrome c oxidase I (mtCOI) gene to characterize D. maidis collected in eight Brazilian sites and one Paraguayan site, as well as publicly available mtCOI data from Argentina and Mexico, to investigate genetic diversity and population structure of this important maize pest. Our results revealed low genetic diversity (π = 0.00162, Hd = 0.433) in the mtCOI partial gene region of the surveyed D. maidis populations. Six haplotypes were identified, with one potential ancestral (haplotype A) predominating in Mexico and tropical South America, and a second, possibly more recent one (haplotype B) standing out in temperate areas of the continent. The population structure detected indicates that outbreaks of D. maidis in different regions are associated primarily with local populations, with minor contribution from long-distance dispersal of insects, and limited gene flow across different countries and macro-regions. Based on these findings, pest management strategies should focus on suppressing winter survival and migration of D. maidis within a regional scale, thus reducing population pressure in maize crops.