Restriction fragment length polymorphisms and RAPD markers in DNA of Plasmopara halstedii, the downy mildew fungus of sunflower.
Twenty-two P. halstedii isolates representing races 1, 3, 4, 5 and 6 from Hungary, Yugoslavia, Bulgaria, USA, France and Canada underwent molecular analysis. Southern hybridization of 44 clones with total DNA from each race identified 2 clones which distinguished the races when hybridized with BamHI digested total DNA. Hybridization with DNA from different isolates revealed identical patterns within races. Hybridization of clone 1-13B to EcoRI digested total DNA from each race produced fragments that differed by 0.75 kb, indicating the presence of a family of direct tandem repeats. RAPD analysis of isolates revealed extensive polymorphism and 2 random primers differentiated all isolates from each other. Two other primers identified RAPD markers for some race 3 isolates. RAPD patterns differed between a Bulgarian race 3 isolate and those from the USA, whereas they were similar for race 6 isolates from France and Canada. RAPD markers gave consistent patterns between different generations of one isolate.