Genome Sequence Resources of Two 'Candidatus Liberibacter asiaticus' Strains from Pakistan

Abstract

'Candidatus Liberibacter asiaticus' (CLas) is an unculturable, phloem-restricted alpha-Proteobacteria, associated with citrus Huanglongbing (HLB), which is one of the most destructive diseases in citrus production worldwide. Here, we present the genome sequences of CLas strains PA19 and PA20 from HLB-affected kinnow trees in Multan, Punjab Province, Pakistan. The CLas genomes of PA19 and PA20 comprise 1,224,156 bp and 1,226,225 bp, respectively, with an average GC content of 36.4%. Both harbored the Type 2 prophage. In this study, we report two CLas genomes from Pakistan, which extends the sequence database of CLas and will contribute to CLas biology and HLB management. 'Candidatus Liberibacter asiaticus' (CLas), associated with citrus Huanglongbing (HLB), is an uncultured, phloem-restricted, gram-negative, alpha-Proteobacteria and can infect almost all citrus varieties (Bove 2006; Jagoueix et al. 1994). The suspect HLB, initially called citrus dieback, was reported to be present on the Indian subcontinent including India and Pakistan during the early 1900s (Hussain and Nath 1927). The presence of HLB in citrus orchards of Pakistan was confirmed based on polymerase chain reaction (PCR) in 2007 (Chohan et al. 2007). Currently, HLB has severely limited citrus production in Punjab Province, where it is the most important citrus producing area in Pakistan. Recent research showed that CLas strains from India were genetically distinct based on microsatellite analysis of CLas strains from eight countries (Islam et al. 2012). Genomic information of CLas strains from the Indian subcontinent are needed to better understand CLas biology and its epidemiology in Asia. So far, 16 whole genome sequences of CLas strains from the U.S.A., China, Japan, and Thailand have been released. In this study, CLas genomes of PA19 and PA20 strains from Pakistan were reported. In December 2018, leaves of Kinnow mandarin (Citrus nobilis Lour. x C. deliciosa Tenora) trees, showing typical blotchy mottling symptoms, were collected from Multan, Pakistan. Total DNA of strains PA19 and PA20 were extracted from the midrib of leaves using Biospin Omni Plant Genomic DNA Extraction Kit (BioFlux, China). CLas presence was confirmed by real-time PCR (Li et al. 2006). Bacterial DNA was enriched and enlarged as described (Zheng et al. 2018), and then sequenced by HiSeq PE150 Illumina platform (Illumina Inc., San Diego, CA).