Phytopathology (2008) 98, 960-968

A.F.S. Mello, R.K. Yokomi, U. Melcher, J.C. Chen, A.C. Wayadande and J. Fletcher (2008)
Genetic diversity of Spiroplasma citri strains from different regions, hosts, and isolation dates
Phytopathology 98 (9), 960-968
Abstract: Spiroplasma citri, a phloem-limited pathogen, causes citrus stubborn disease (CSD). Losses due to CSD in California orchards have grown over the past decade. To investigate the possibility of introduction or emergence of a new strain, a study of genetic diversity among S. citri strains from various locations was conducted using random amplified polymorphism DNA-polymerase chain reaction (RAPD-PCR) of 35 strains cultured from 1980 to 1993, and of 35 strains cultured from 2005 to 2006. Analysis using 20 primer pairs revealed considerable diversity among strains. However, no unique genetic signatures were associated with recently collected strains compared with those collected 15 to 28 years ago, and no geographically associated pattern was distinguishable. S. citri strains from carrot and daikon radish contain some unique DNA fragments, suggesting some host plant influence. Multiple strains from single trees also showed genetic diversity. Sequencing of five RAPD bands that differed among strains showed that diversity-related gene sequences include virus fragments, and fragments potentially encoding a membrane lipoprotein, a DNA modification enzyme, and a mobilization element. No differences in colony morphology were observed among the strains. The lack of correlation between PCR patterns and isolation date or collection site is inconsistent with the hypothesis that recent infections are due to the introduction or emergence of novel pathogen strains.
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Database assignments for author(s): Raymond K. Yokomi, Ulrich Melcher

Research topic(s) for pests/diseases/weeds:
molecular biology - genes
population dynamics/ epidemiology

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Spiroplasma citri	Citrus (genus)	U.S.A. (SW)