Genetic diversity and population structure of Dalbulus maidis (Hemiptera: Cicadellidae) in South America

The corn leafhopper, Dalbulus maidis (Hemiptera: Cicadellidae) and its associated corn stunt disease 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 expanded its occurrence range into 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 mitochondrial DNA cytochrome oxidase I partial gene (mtCOI) to characterize specimens of D. maidis collected in eight Brazilian sites and one Paraguayan site, and then combined our mtCOI data with previous sequences available from Argentina and Mexico to investigate genetic diversity and population structure in this important agricultural pest species. Our results revealed low genetic variability in D. maidis populations, with one potential ancestral haplotype predominating in Mexico and tropical South America (Dmai-COI-01), and a second, possible more recent one (Dmai-COI-02) standing out in temperate areas of the continent. This led to a moderate degree of population structuring, partially separating northern and southern Brazilian populations and strongly differentiating the Argentinian population from the others. The geographical range and frequency of haplotype Dmai-COI-02 suggest that its introduction might be one of the factors driving the recent expansion of D. maidis in southern Brazil, while the partial population structure detected indicates limited gene flow among macro-regions of Brazil and neighboring countries. Based on these findings, pest management programs should focus on suppressing winter survival and mid-range migration of D. maidis within a regional scale, thus reducing population pressure in maize crops.