Morphological and reproductive consequences of an anther smut fungus on Oxalis

Roets F., Curran H. & Dreyer L. L. (2012) Morphological and reproductive consequences of an anther smut fungus on Oxalis.

Sydowia 64 (2): 267–280

Thecaphora capensis, an anther smut fungus from the Greater Cape Floristic Region (GCFR) of South Africa infects a number of Oxalis, the largest geophytic genus in this area. Diseased individuals produce fungal spores instead of pollen in their anthers, which allows for pollinator-mediated transmission of spores. We build on existing meagre knowledge of this plant-pathogen system by elucidating the known host range of T. capensis and by assessing its effect on host morphology and reproduction. Three new hosts were identified, bringing the total number of known host species to twelve. Infection of O. incarnata, O. lanata and O. nidulans generally has negative effects on all morphological traits assessed. However, the magnitude of effect on various characters varied between populations and hosts. Fungal spore presence on stigmatic surfaces of healthy O. incarnata and O. lanata did not compromise seed set. However, diseased individuals were usually sterile, indicating that T. capensis has major population-level impacts. Determining the full host range and consequences of infection are essential, as it will allow for comparisons with similar systems to formulate and test general hypotheses of vector-borne disease dynamics.

Keywords: spore-transmission, Microbotryum violaceum s. l., Greater Cape Floristic Region, Thecaphora capensis.