Role of appressoria in latent infection of banana fruits by Colletotrichum musae

Abstract

In green banana fruits, subcuticular hyphae grew from hyaline appressoria for a period, causing hypersensitive reactions in adjacent cells, and then ceased growth. Stomatal penetration occurred rarely but hyphae from a few hyaline appressoria penetrated guard cells in green bananas. The growth of these hyphae was also restricted within hypersensitive flecks. Dark appressoria remained dormant on unripe fruits. During ripening, subcuticular hyphae remained inactive but dark appressoria germinated to produce penetration hyphae from which the underlying tissues were colonized, leading to formation of typical anthracnose lesions. Mercuric chloride killed hyaline appressoria on glass but failed to kill dark appressoria on glass and fruit surfaces. The probability that ungerminated dark appressoria represent the latent phase is discussed in relation to earlier assumptions that subcuticular hyphae were latent structures.