Submitted to: American Phytopathological Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 6/12/2007
Publication Date: 7/1/2007
Citation: Mello, A.F., Yokomi, R.K., Melcher, U., Chen, J., Fletcher, J. 2007. Genetic Diversity of Spiroplasma citri Isolates from Different Geographical Regions, Plant Hosts, and Dates of Isolations. Phytopathology. 97:S75. Interpretive Summary:
Technical Abstract: Spiroplasma citri, a phloem colonizing pathogen transmitted by leafhoppers, causes citrus stubborn disease. Concern over production losses attributed to stubborn in California orchards has grown over the past decade. To determine if this may be attributed to an introduction or development of a new pathogen strain, a genetic diversity study was conducted using RAPD-PCR of DNA from 69 triply cloned S. citri isolates: 36 from North America and the Mediterranean Region originally cultured from 1980 to 2006; and 31 from isolations from citrus and 2 from carrot and daikon collected in 2005-6 in California. Twenty random primers yielded 159 differentiating amplicons and different DNA patterns. However, no geographically associated pattern was distinguishable. Several DNA fragments appeared to be unique from the carrot and daikon strains suggesting some host plant influence. Genetic diversity was also observed among isolates obtained from individual trees. Sequencing of some differential RAPD bands showed that diversity-related gene sequences include fragments of viruses, membrane lipoproteins, DNA modification enzymes, and mobilization elements. A lack of correlation between PCR patterns and isolation date suggests that recent infections are not due to novel pathogen strains.