DNA fingerprinting and integron sequence analysis of Xanthomonas translucens infecting cereals (Poster)

Four Xanthomonas translucens pathovars have been characterised as causing bacterial leaf streak (BLS) on cereals. Until recently, X. t. pv. undulosa (Xtu) and X. t. pv. translucens (Xtt) were regulated pests for Triticum and Hordeum seed imports into New Zealand. However, Xtt was recorded on Hordeum and consequently this pathovar was removed from the Import Health Standards for both crops. Overlapping host ranges and the inability of existing diagnostic tools to easily differentiate the four pathovars causing BLS have complicated the accurate identification of pathogenic xanthomonads on seed imports. As a result, there remains the possibility of introduction of exotic X. translucens strains pathogenic to Triticum. In our research we investigated whether an international collection of 18 X. translucens isolates infecting barley, wheat and other small grains can be differentiated by DNA sequence analysis of the ubiquitous Xanthomonas integron region and by using DNA fingerprinting. We found that integron sequences were identical for almost all strains isolated from Triticum. Furthermore, strains isolated from Hordeum possessed distinct integron sequences, all of which were different from the integron sequences of strains from Triticum. PCR also showed genetic variation between isolates from Triticum, Hordeum and other hosts. We discuss the hostspecific diversity of X. translucens strains and the implications for their detection on seed imports into New Zealand.