Survey of Phytophthora infestans populations in Serbia: Mating type, metalaxyl resistance and virulence properties

A total of 37 single-lesion isolates of Phytophthora infestans were collected during 2000 from different potato growing regions in the central part of Serbia. They were paired in A1 and A2 matings to determine their mating types. Of these 37 isolates, 28 were found to belong to the A2 mating type, eight to the A1 type and one was found to be self-fertile (A1/A2). Using the in vitro mycelial radial growth method no metalaxyl resistant P. infestans isolate could be found. The rate of occurrence of intermediate isolates was not high, on the average 2.70%. All other isolates were sensitive to metalaxyl. There was no correlation between mating type and the intermediate metalaxyl resistance found

Occurrence of new populations and mating types of Phytophthora infestans (Mont) de Bary in Serbia

Late blight disease caused by Phytophthora infestans is an important disease of potato and tomato in Serbia. The prevalence of late blight has increased in recent years similar to the situation in the rest of the world. During the 2001 and 2002 growing season late blight infected potato leaf samples were collected from the region of Guca, Serbia. P. infestans was isolated as pure cultures from diseased plant material by using several growing methods. Purified cultures were grown on rye A agar for further characterisation studies and storage in order to determine the structure of the Serbian P. infestans populations and to compare them with other European isolates. Mating types were determined from 48 isolates collected at 13 different potato fields in 2001. Four isolates were used as a control obtained from potato fields in 2002. Each isolate was paired on rye A agar with the known A1 (US-1) and A2 (US-8) test cultures. A PCR-RFLP method applying the two primer pairs PIMTP2R / PIMTP2F (P2) and PIMTP4R / PIMTP4F (P4) was used to identify mitochondrial DNA (mtDNA) haplotypes. Enzymatic digestion was performed using the restriction enzyme MspI for the P2 amplification product and EcoRI for the P4 product. From the restricted fragments the haplotypes can be differentiated. Our results showed that among the surveyed P. infestans isolates both mating types are present in Serbia. However, A1 mating type isolates were distributed at 11 locations whereas the A2 mating type was limited to two locations. All the isolates tested belong to the la haplotype, whereas haplotypes Ib, IIa and IIb, being rare in Europe, could not be detected in our survey. The data obtained in this study support the hypothesis that "new populations" of P. infestans do already exist in some Serbian areas

Evaluation of phenotypic and molecular typing techniques for determining diversity in Erwinia carotovora subsp. atroseptica

A number of phenotypic and molecular fingerprinting techniques, including physiological profiling (Biolog), restriction fragment length polymorphism (RFLP), enterobacterial repetitive intergenic consensus (ERIC) and a phage typing system, were evaluated for their ability to differentiate between 60 strains of Erwinia carotovora ssp. atroseptica (Eca) from eight west European countries. These techniques were compared with other fingerprinting techniques, random amplified polymorphic DNA (RAPD) and Ouchterlony double diffusion (ODD), previously used to type this pathogen. Where possible, data were represented as dendrograms and groups/subgroups of strains identified. Simpson's index of diversity (Simpson's D) was used to compare groupings obtained with the different techniques which, with the exception of Biolog, gave values of 0.46 (RFLP), 0.39 (ERIC), 0.83 (phage typng), 0.82 (RAPD) and 0.26 (ODD). Of the techniques tested, phage typing showed the highest level of diversity within Eca, and this technique will now form the basis of studies into the epidemiology of blackleg disease