Molecular diagnosis of mildew (Plasmopara halstedii) infection in sunflower seeds

Sunflower downy mildew, caused by the fungus Plasmopara halstedii, is a pot entially devastating disease with important economical implications. Becaus e of the risk of propagation of the disease by infected seeds and of the re gular observation of metalaxyl-resistant isolates of the fungus, there is a greater need for efficient method to detect the fungus in seed or plant ti ssue. Therefore, we developed a molecular test to show the presence of sunf lower downy mildew in seed samples. Several extraction methods were compare d to improve quality and yield of the scanty DNA of the fungus. Both whale and hulled seeds of contaminated samples were analysed by PCR, using Plasmo para halstedii specific primers. We demonstrated that DNA of the pathogen i s always detected, notably in the shell fraction. These data are important for the development of a diagnostic kit.