The Asian citrus psyllid (Diaphorina citri Kuwayama) is the insect vector of the bacterium Candidatus Liberibacter asiaticus (CLas), the causal agent for the citrus greening or Huanglongbing disease which threatens citrus industry worldwide. This vector is the primary target of approaches to stop the spread of the pathogen.
Single copy marker analysis using BUSCO of the current genome shows a significant proportion of 3,350 single-copy markers, which are conserved in Hemipterans, to be missing (25%) with only 74% present in full-length copies. The manual genome annotation identified a number of misassemblies and missing genes in the current genome. This is, in-part, due to the complexity introduced when assembling a heterogeneous sample containing DNA from multiple psyllids and potentially exacerbated by the use of short reads. To improve quality of genome assembly, we have generated 36.2Gb of Pacbio long reads from 41 SMRT cells with a coverage of 80X for the 400-450Mb genome. The Canu assembler was used to create an interim assembly (Diaci v1.9) with a contig N50 of 115.8kb and 8300 contigs. We are employing Dovetail chicago libraries and 10X Illumina library generated from a single psyllid in conjunction with Bionano optical maps to achieve long-range scaffolding of the genome. The final assembly will be polished with Pacbio and Illumina paired-end reads followed by scaffolding with Illumina mate-pair reads. This will be the first time all these methods have been applied to resolve an insect genome from a highly heterogeneous sample. The new assembly will be available on https://citrusgreening.org/.