The fine structure of the sporangium in Pseudoperonospora humuli (Chromista, Oomycota, Peronosporales)

The ultrastructure of the sporangium, particularly the dehiscence apparatus in Pseudoperonospora humuli is similar to the one described in P. cubensis. This similarity is considered an indication of the homogeneity of the genus Pseudoperonospora. The dehiscence apparatus in P. humuli is also similar to those occurring in other closely related, and even more distant genera of Oomycota. The importance of the poroid condition in distinguishing Pseudoperonospora from Peronospora is emphasised. The dehiscence apparatus is considered as the most appropriate term for the structures present in genera of Oomycota having poroid dissemination organs. (C) 2000 Adac / Editions scientifiques et medicales Elsevier SAS.