Submitted to: International Research Conference on Huanglongbing
Publication Type: Abstract only
Publication Acceptance Date: 2/9/2013
Publication Date: 2/10/2013
Citation: Deng, X., Liu, R., Zhang, P., Chen, J. 2013. Further evidence that U.S. and China populations of “Candidatus Liberibacter asiaticus” are different. In: International Research Conference on Huanglongbing. p.38. Interpretive Summary:
Technical Abstract: Citrus Huanglongbing (HLB) is associated with “Candidatus Liberibacter asiaticus”. Many efforts to detect genetic variation of “Ca. L. asiaticus” in conserved genomic loci such as 16s rDNA have not been successful. A genomic locus with short tandem repeats distinguished “Ca. L. asiaticus” populations from Guangdong, China and Florida, U.S. (Phytopathology 100:567-572). Prophage genes are also good candidates. Prophages are important genetic elements of bacterial genomes and are involved in lateral gene transfer, pathogenicity, environmental adaptations and interstrain genetic variability. In this study, the sequence of a phage terminase gene was identified. Based on the terminase gene sequence, a set of primers was designed and used for PCR detection of prophage in HLB citrus samples collected from two provinces, Guangdong with an average elevation of <500 m, and Yunnan with an average elevation of >2,000 m. The frequency of prophage detection was 15.8% in Guangdong and 97.4% in Yunnan. However, prophage gene sequences obtained from 10 Guangdong strains and 8 Yunnan strains shared 100% identity. It remains unclear what contributed to variation in prophage incidence among the two regions. Further study showed that the prophage gene could be detected in 99% of Florida strains of “Ca. L. asiaticus”, yet differed from the China strains at 9 nucleotide positions.