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Title: Haplotypes of 'Candidatus Liberibacter solanacearum' suggest long-standing separation

item NELSON, WARRICK - Plant And Food Research
item FISHER, TONJA - Washington State University
item Munyaneza, Joseph - Joe

Submitted to: European Journal of Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/10/2010
Publication Date: 5/24/2011
Citation: Nelson, W.R., Fisher, T.W., Munyaneza, J.E. 2011. Haplotypes of 'Candidatus Liberibacter solanacearum' suggest long-standing separation. European Journal of Plant Pathology. 130:5-12.

Interpretive Summary: Zebra chip, a newly emerging and economically important potato disease in the United States, Mexico, Central America, and New Zealand, is caused by a previously undescribed species of the bacterium liberibacter vectored by the potato psyllid. Researchers at USDA-ARS Wapato, in collaboration with scientists at Plant and Food Research Institute in New Zealand, conducted studies to identify and determine the geographic distribution of the different genetic variants of this bacterium species. Depending on geographic ranges, three distinct genetic variants of the bacterium were discovered, suggesting existence of separate bacterial populations. Information from this research will help affected potato producers reduce damage caused by this important pathogen by effectively managing the appropriate bacterium variant and its insect vector.

Technical Abstract: Three haplotypes of the recently discovered bacterium species “Candidatus Liberibacter solanacearum” are described and related to geographic ranges. The first two are associated with Zebra Chip/Psyllid Yellows of potatoes and other solanaceous plants, vectored by the tomato/potato psyllid Bactericera cockerelli in North and Central America and New Zealand. The third is associated with diseased carrots in Finland and vectored by the carrot psyllid Trioza apicalis. The haplotypes are described by SNPs on the 16s, 16s/23s ISR and 50s rplJ and rplL rRNA genes. These SNPs are inherited as a package across the three genes. Haplotype “a” has been found primarily from Honduras and Guatemala through western Mexico to Arizona and California, and in New Zealand. Haplotype “b” is currently known from eastern Mexico and northwards through Texas to south central Washington. These haplotypes show some range overlap in Texas, Kansas and Nebraska. The haplotypes are not yet known to elicit biological differences in the plant or insect hosts, although some amino acids are indicated in the 50s genes. These apparently stable haplotypes suggest separate bacterial populations of long standing.