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Analysis of a Prophage Gene Frequency Revealed Population Variation of ‘Candidatus Liberibacter asiaticus’ from Two Citrus-Growing Provinces in China

April 2011 , Volume 95 , Number  4
Pages  431 - 435

Rui Liu, Pei Zhang, Xuelian Pu, and Xiaoqian Xing, Laboratory of Huanglongbing Research, Department of Plant Pathology, South China Agricultural University, Guangzhou, Guangdong, P.R. China; Jianchi Chen, Crop Diseases, Pests and Genetics Research, San Joaquin Valley Agricultural Sciences Center, United States Department of Agriculture, Parlier, CA; and Xiaoling Deng, Laboratory of Huanglongbing Research, Department of Plant Pathology, South China Agricultural University

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Accepted for publication 22 November 2010.

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 prophage terminase gene of ‘Candidatus Liberibacter asiaticus’, a bacterium associated with citrus Huanglongbing (HLB), was selected as a molecular marker to assess the genetic variation in two ‘Ca. L. asiaticus’ populations from geographically distinct provinces (Guangdong and Yunnan) in China. The frequency of the prophage terminase gene was 15.8% (19/120) in Guangdong (altitude <500 m) and 97.4% (38/39) in Yunnan (altitude >2,000 m). The difference was highly significant (P < 0.0001) based on χ2 analysis. However, the partial prophage terminase gene sequences obtained from 10 Guangdong strains and 6 Yunnan strains were identical or highly similar, suggesting that at least some bacterial strains in the two locations shared a common recent origin. This is the first report on population variation of ‘Ca. L. asiaticus’ in China, where HLB was first described. The population variation of ‘Ca. L. asiaticus’ in the two geographical regions and the related HLB epidemiology were discussed.

This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 2011.