Appressoria of Gloeosporium musarum Cke. and Massee on Banana Fruits

Abstract

Gloeosporium musarum is one of the most important fungi causing rotting of banana fruits during transport and storage^1,2. Although the fungus is of greatest commercial concern when acting as a post-harvest wound parasite, it also infects unwounded immature fruit in the field^2–4. These early infections do not become manifest until the fruit starts to ripen after harvest; such infections are known as ‘latent infections’. The basis of latency in G. musarum was elucidated by Simmonds³ and Chakravarty⁵. In a water film on the fruit surface, conidia of G. musarum germinate within 4 h. After elongating for a variable distance, the germ tube swells at the tip to form an appressorium. After 24–72 h, a fine infection hypha grows from the appressorium and pierces the cuticle by mechanical means. No further penetration occurs until the fruit starts to ripen. Simmonds³ concluded that this subcuticular hypha is the form in which the fungus survives its period of latency, which may exceed 5 months in Australia. When the fruit is mature, the subcuticular hypha resumes activity and penetrates the cellulose wall of the epidermis cell; the fungus then spreads through the tissues to cause a typical anthracnose lesion.