Hyperparasitism on Plasmopara viticola by Simplicillium lanosoniveum

A previously unknown association between Plasmopara viticola, the causal pathogen of grape downy mildew, and the mycoparasite strain F2 was described in this paper. F2 could be consistently isolated from the mildew of diseased spots on grape leaves of Kyoho (Vitis labrusca × V. vinifera cv. Kyoho) infected with P. viticola, but neither from the surfaces of healthy grape leaves nor within lesions of other diseases. It could be observed that strain F2 was capable of coiling around sporangiophores and sporangia of P. viticola under microscope, causing hyphae deformation, decreasing the pathogen growth, and reducing the number of sporangia. This fungal strain was identified as Simplicillium lanosoniveum on the basis of morphological characterizations and 28S rDNA sequencing. To our knowledge, this is the first report of S. lanosoniveum with hyperparasitic characteristics on P. viticola, and the hyperparasite has potential application in the control of grape downy mildew.