Click on any
image for a more
detailed view

Pathogen Biology

Sexual reproduction

Sclerotia, or ergots, are the overwintering, or survival, stage of the fungus Claviceps purpurea (Figure 1). After exposure to cold temperatures, moisture stimulates the formation of one or more tiny, stalked stromata (Figure 4). Sexual mating, which involves karyogamy to form diploid nuclei and meiosis to return to the haploid state, stimulates the production of the sexual fruiting bodies, the perithecia, and the sexual spores, the ascospores. In the spherical head of each stroma, numerous perithecia form (Figure 5). These flask-shaped fruiting bodies are filled with asci, each of which contains 8 filiform (long and thin) ascospores. Ascospores are usually forcibly discharged into the air.

Figure 1

Figure 4

Figure 5

Asexual reproduction

As the mycelium colonizes the infected ovary of the host plant flower, conidiophores and conidia are produced on the surface of the ovary. Conidia (asexual spores), which are haploid, one-celled, and elliptical (Figure 6), are exuded in droplets of honeydew (Figure 7). Splashing raindrops and insects aid in the dispersal of the conidia.

Figure 6

Figure 7

RETURN TO TOP