Ultrastructural and histochemical studies on interactions between Vitis vinifera L. and Uncinula necator (Schw.) Burr.

Abstract

SUMMARYHost-parasite interactions between the grapevine Vitis vinifera L. and the powdery mildew Uncinula necator (Schw.) Burr, were studied by light microscopy and histochemistry, scanning and transmission EM. The lobed appressoria (10/^m diam) of the fungus adhered to the host cuticle because of their shape and the production of a soluble adhesive substance. Each formed a penetration peg (0-3 //m diam) which, after penetration into the epidermal cell, developed into a globular haustorium consisting of a nucleated central body with fingerlike lobes, embedded in a matrix. The surrounding extrahaustorial membrane was derived from the transformed plasmalemma of the host cell. As a defence mechanism the walls of the host cell and neighbouring cells were encrusted with silica and phenolic substances associated with cell wall bound peroxidase activity. Penetration may have been blocked by the formation of a papilla composed of different layers containing carbohydrates, silica and phenolic substances. Cells forming a thick papilla were not infected. In cells with old infections, callose deposits could be observed in walls and/or around the haustorial neck and papilla, and sometimes around the whole haustorium.

Structural Characterisation of the Interaction between Triticum aestivum and the Dothideomycete Pathogen Stagonospora nodorum

“…It is also interesting to note that M. grisea is able to use hyphopodia to infect rice roots rather than the appressorium mediated method of penetration used on leaves (Sesma and Osbourn, 2004). Structures very similar to those identified in this study have also been reported for the foliar pathogens Erysiphe pisi and Ucinula necator (Falloon et al, 1989;Heintz and Blaich, 1990). In highlighting the inconsistency with naming these structures, the authors of both papers reported the presence of appressoria.…”

Identification of resistance gene analogs linked to a powdery mildew resistance locus in grapevine

“…These symptoms are due to the presence of hyphae producing conidiophores and conidia on the surface of the host tissue. The hyphae form lobed appressoria which produce a penetration peg that subsequently penetrates into the host epidermal cell and forms a haustorium via which the fungus absorbs nutrients from the host (Heintz and Blaich 1990).…”

Powdery Mildew Induces Defense-Oriented Reprogramming of the Transcriptome in a Susceptible But Not in a Resistant Grapevine

“…Subsequently, an infection structure, termed a haustorium, is formed within the epidermal cell through which a dynamic exchange of signals and metabolites occurs between the pathogen and the host cell (Heintz and Blaich, 1990;Rumbolz et al, 2000). The process of penetration and haustorium formation in V. vinifera may be as short as 14 h under optimal conditions (Rumbolz et al, 2000).…”