COMPARISON OF RANDOMLY AMPLIFIED POLYMORPHIC DNA WITH AMPLIFIED FRAGMENT LENGTH POLYMORPHISM TO ASSESS GENETIC DIVERSITY AND GENETIC RELATEDNESS WITHIN GENOSPECIES-III OF PSEUDOMONAS-SYRINGAE

Recently, DNA pairing analyses showed that Pseudomonas syringae pv. to mato and related pathovars, including P. syringae pv. maculicola, form a genomic species (Pseudomonas tomato) (L. Gardan, H. L. Shafik, and P. A. D. Grimont, p. 445-448, in K. Rudolph, T. J. Burr, J. W. Mansfie ld, D. Stead, A. Vivian, and J. von Kietzell, ed., Pseudomonas syringa e Pathovars and Related Pathogens, 1997), The genetic diversity of 23 strains belonging to this genomic species and 4 outgroup strains mas a nalyzed with randomly amplified polymorphic DNA (RAPD) and amplified f ragment length polymorphic (AFLP) techniques. Simple boiling of P. syr ingae cells was suitable for subsequently DNA amplification to obtain reliable patterns in RAPD and AFLP analyses. In general, the grouping of P. syringae strains by both analysis techniques corresponded well w ith the classification obtained from an RFLP analysis of ribosomal DNA operons, DNA pairing studies, and an analysis of pathogenicity data. However, two strains of P. syringae pv. maculicola produced distinct D NA patterns compared to the DNA patterns of other 14 syringae pv. macu licola strains; these patterns led us to assume that horizontal transf er of DNA could occur between bacterial populations, both techniques u sed in this study have high discriminating power because strains of B. syringae pv. tomato and P. syringae pv. maculicola which were indisti nguishable by other techniques, including pathogenicity tests on tomat o, were separated into two groups by both RAPD and AFLP analyses. In a ddition, data analysis showed that the AFLP method was more efficient for assessing intrapathovar diversity than RAPD analysis and allowed c lear delineation between interspecific and interspecific genetic dista nces, suggesting that ie could be an alternative to DNA pairing studie s, However, it was not possible to distinguish the two races of P. syr ingae pv. tomato on the basis of an analysis of the data provided by e ither the AFLP or RAPD technique.