A Histological Study of the Grass Heteropogon contortus Infected by the Smut Sorosporium caledonicum

Abstract

A study of the spatial and temporal relationships of Heteropogon contortus and the smut Sorosporium caledonicum has been made. It has been shown that hyphae move into the axillary buds on the bases of infected tillers at various stages of bud development. Hyphal distribution in the base of the parent tiller determines whether or not a bud receives mycelium, and the extent to which hyphae grow through the tissues of the buds and young tillers determines whether a tiller bears a sorus or an inflorescence. A sorus forms only if hyphae are close to the apical meristem at the time of floral initiation. Floral initiation occurs abnormally early in smutted tillers which elongate at the beginning of a season. A clear relationship exists between the presence of hyphae in close proximity to the apical meristem, and early floral initiation.