Chapter 10 - Filamentous Fungi (Botrytis cinerea)

Abstract

This chapter discusses some of the diseases of grapevine such as powdery mildew, downy mildew, and gray mold produced by the filamentous fungi. Powdery mildew, which is known by different names in different regions, affects grapevines all over the world, even in tropical regions. Powdery mildew can infect all the green tissues of the grapevine. The fungus only penetrates epidermal cells, into which it introduces globular structures known as haustoria that are used to absorb nutrients. Diseased plants develop a whitish gray powder caused by the presence of abundant conidiophores. Grapevine downy mildew is caused by the fungus Plasmopara viticola, which is an obligate parasite of several genera of the family Vitaceae. It grows intracellularly in infected grapevine tissue, where it forms tubular hyphae with globular haustoria. The fungus generally overwinters as oospores in fallen, dead leaves, although it can also survive as a mycelium in buds and persistent leaves. Species from the phytopathogenic fungal genus Botrytis constitute a serious threat to a wide variety of crops. B. cinerea is a particularly virulent variant and attacks many types of crops including grapevines, causing characteristic necrotic patches on leaves, stems, and fruits, and forming a grayish powdery mold known as gray mold.