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Studies of the powdery-mildew fungus, Leveillula taurica, on green pepper. 11. Light and electron microscopic observation of the infection process1KUNOH. H., M. KOHNO. S. TASHIRO. ilnd H. ISHIZAKI. 1979. Studies of the powdery-mildew fi~ngus, Lel.eillrrla toririco. on green pepper. 11. Light and electron microscopic observation of the infection process. Can. J. Bot. 57: 2501-2508. Almost all ultrastructural studies of powdery-mildew fungi have been focused on the epiparasitic fungi. In this paper, one of the endoparasitic powdery-mildew fungi, Leveilllrla tnirricn (Lev.) Am., on green pepper (Ccrpsicirtn ntrtrir~rt?~ L. var. eitrgirlosrrt?r Mill.) leaves was investigated by light and electron microscopy. Most germinated conidia formed a lobed adhesion body (similar to the appressorium in morphology but different in function) before stomatal invasion. The track of the adhesion body on the leaf epidermis was depressed, and no cuticular perforations were observed in it. After stomatal invasion, infection hyphae grew extensively into the intercellular spaces of the leaves and formed haustoria in the spongy-and palisade-parenchyma cells. The haustorium was flask shaped with a neck arising from the intercellular hypha. The overall profiles of the haustorium resembled those of epiphytic powdery-mildew fungi of other authors; the haustorium was composed of a nucleate central body and many anucleate lobes, and the entire structure was bounded by an extrahaustorial membrane. Papillae consisting of three distinct f e~i o n s formed against the outer cell walls at the site of penetration. The most obvious alteration In rnfected host cells was a marked increase in the number of large lipid bodies. Lipid bodies increased in number with time after haustorial formation. They appeared first in the host cytoplasm near the extrahaustorial membrane, then in the extrahaustor~al matrix and haustorial body. KUNOH, H., M. KOHNO, S . TASHIRO et H. ISHIZAKI. 1979. Studies of the powdery-mildew fungus, Leveill~rln tnrrricn, on green pepper. 11. Light and electron microscopic observation of the infection process. Can. J . Bot. 57: 2501-2508. Presque toutes les etudes ultrastructurales d e champignons causant le mildiou ont ete effectuees sur des champignons epiparasites. L e present travail est une etude en microscopie photonique et electronique de I'up des champignons endoparasites, Le~eillirltr talrriccr (Lev.) Am., provoquant le mildiou sur les feuilles du piment vert (Cnpsiclrm nntruutrr L . var. crtrgrrlo.sutn Mill.). La plupart des conidies qui germent forment, avant I'invasion des stomates, un corps d'adhesion lobe (de morphologie semblable a celle d e I'appressorium, mais d e fonction differente). La trace du corps d'adhesion sur I'epidermefoliaire est deprimee et on n'y observe aucune perforation de la cuticule. Apres I'invasion des stomates, les hyphes d'infections subissent une croissance considerable dans les espaces intercellulaires des feuilles et forment des haustoriums dans les cellules du parenchyme lacuneux et du parenchym...

The effects of polyoxin on sensitive and resistant isolates of Alternaria In the resistant isolate, similar mycelial changes were observed but frequency of these changes was much less than in the sensitive one.

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