The population genetic composition of invasive sorghum aphids

During 2013, grain sorghum crops experienced intense pest pressure from a new invasive aphid pest. Although these aphids were initially thought to be the sugarcane aphids, my research group later identified them as sorghum aphids. Sorghum and sugarcane aphids belong to a cryptic species complex that feed on several grass species, and sorghum aphids are genetically differentiated from sugarcane aphids (SCA). Our team has identified three genetically differentiated populations of sorghum aphids in Texas sorghum using AFLPs (amplified fragment length polymorphisms). We hypothesized that uising high-density molecular markers (i.e., SNPs) may reveal a larger number of genetically differentiated populations of sorghum aphids across its geographic distribution. To accomplish this we collected aphids on grain sorghum and Johnson grass in different counties of Texas. To increase the genomic material, individual parthenogenetic female sorghum aphids were used to develop clone colonies. Ten aphids from each clone line were extracted for genomic material using a Qiagen PureGene Kit and sequenced using Illumia NovaSeq. Raw sample reads were processed using the STACKS pipeline and analyzed for population genetic composition using STRUCTURE. We found population genetic structure among aphids in Texas and those collected from other states. Because genetically differentiated populations may vary in traits relevant to pest control, it is important to genetically characterize pest species. We will discuss how the population genetic structure of this aphid in Texas impacts potential management practices.