Genome-wide association and population genetics of Diaphorina citri: Examining genetics underlying vector capacity of the Huanglongbing insect vector

Genome-Wide Association Studies (GWAS) have revolutionized scientific insight and the potential to examine the genetic architecture of complex phenotypes in insect populations. Analysis of single nucleotide polymorphisms (SNPs), across an entire insect genome, identifies novel loci linked to a wide range of traits such as vector competence and insecticide resistance. In this study, we performed a multi-population GWAS on 498 adult Diaphorina citri, the insect vector of Candidatus Liberibacter asiaticus (CLas), to investigate the genetic components of diverse CLas acquisition phenotypes. D. citri adults were collected from four citrus groves in southeast Florida, USA, and the CLas acquisition phenotype for each insect was estimated using the absolute titer of CLas, as measured by qPCR. A high-quality reference genome, assembled with PacBio long reads, allowed for accurate SNP calling and loci association. Furthermore, mitochondrial haplotyping of nearly 700 D. citri mitochondrial genomes, using a novel split kmer approach, uncovered globally distributed haplotypes as well as haplotypes within local Florida populations. This study provides novel insight into the genetics underlaying vector-biology, promotes further research to identify therapeutics which prevent insect-vector disease acquisition and transmission, and facilitates unbiased evolutionary analysis of internationally dispersed psyllid lineages using complete mitochondrial genomes.