AFLP analysis of Xanthomonas axonopodis and X. arboricola strains used in xanthan production studies reveal high levels of polymorphism

Abstract

Amplified fragment length polymorphism (AFLP) was used to analyze the genetic diversity of 14 strains of Xanthomonas arboricola pv. pruni and seven strains of X. axonopodis pv. phaseoli, which are used in xanthan production studies. Relationships identified by the AFLP profiles were assessed for xanthan production capacity, geographical location and host plant. Strains were isolated from 10 different geographic regions in South and Southeast States in Brazil. Data were analyzed for genetic similarity using the Dice coefficient and subjected to UPGMA cluster analysis. A total of 128 AFLP fragments were generated from four primer combinations: £coRI+C/MseI+0, £coRI+AMseI+0, £coRI+G/MseI+T and £coRI+G/MseI+A. Of these, 96.1% were polymorphic. X. axonopodis pv. phaseoli (SD = 0.27) was shown to be more polymorphic than X. arboricola pv. pruni (SD = 0.58). All 14 pathovar pruni strains were included in a single main group (SD = 0.58), while the pathovar phaseoli strains were divided into three separate groups, with one group containing five strains (SD = 0.38) and two isolated groups (SD = 0.31 and 0.27) composed of only one strain each. Species were distinguished by three and eight specific AFLP markers present in the pathovar phaseoli and the pathovar pruni, respectively. For the unique strain without xanthan production capacity (X. axonopodis pv. phaseoli str. 48), nine specific AFLP bands were found. There was no evidence that geographic area or host plant influenced genetic heterogeneity. Correlations between AFLP patterns and xanthan production capacity were found in some strains, but were not consistent enough to establish a relationship.