Influence of Leaf Surface Features on Spore Deposition and the Epiphytic Growth of Phytopathogenic Fungi

Leaf surfaces provide an important substrate for the growth of a wide variety of fungal organisms. Saprophytic fungi obtain water and nutrients from these surfaces and the leaf surface provides a physical environment suitable for growth and reproduction. For phytopathogenic fungi, the leaf surface represents a temporary, supportive environment, but a surface that must be breached before a successful pathogenic interaction can become established. Thus, the physical and chemical characteristics of the leaf surface play an important role in governing the success or failure of fungal growth on, and subsequently in, the leaf. Numerous reviews have been written about the growth of fungi in association with plant surfaces (e.g., Preece, 1976; Aist, 1981; Wynn, 1981; Staples and Macko, 1984; Hoch and Staples, 1987, 1991). This chapter focuses on features of the leaf surface as they influence the establishment and growth of various fungi. Attention will be given to the time and place of initial spore deposition on the leaf, to growth over the surface, and in the case of pathogenic fungi, to their penetration into the leaf. Since the authors’ research experience lies in the growth and development of rust fungi, considerable emphasis will be placed on examples involving these organisms.