Genetic and Molecular Characterisation of Plasmopara Halstedii Isolates from Hungary

Plasmopara halstedii (Farl.) Berl. et de Toni, the downy mildew pathogen of sunflower (Helianthus annuus L.) causes devastating disease of this crop worldwide. Mildewed sunflower plants do not usually produce viable seed and, once they are systemically infected, they cannot recover from the disease. The pathogen colonises the underground tissues of young seedlings resulting in a typical systemic infection of the whole plant. Under favourable conditions, the fungus sporulates on affected leaves from which sporangia may spread wind-blown causing secondary local infections on adjacent plants. Recently, an increasing number of such local infections give rise to secondary systemic infections whereby the fungus may enter the newly developing seed in a latent form permitting seed transmission unnoticed.