Seedborne head smut

Hosts and Symptoms. 
Sporisorium reilianum causes the diseases maize head smut and sorghum head smut. This soil borne smut fungus has two formae speciales. S. reilianum f. sp. reilianum is specific to sorghum and S. reilianum f. sp. zeae is specific to maize. It is unknown why the two formae speciales cannot form spores on their respective non-favored hosts.
Symptoms of the fungus are expressed on both the tassels of corn and sorghum as well as on the actual ear in the form of large smut galls. When the sorghum tassel is infected, the fragile gall membrane will have a range from just a few black spores to a large mass of black spores covering the tassel. The spores are a sign of the disease and are used for dispersal of the disease to other corn and sorghum plants. When the ear of the corn is infected, it looks very small and tear-drop shaped and seems as though it does not have a cob inside at all. The cob is replaced by white sori which are the structures that make and hold the spores of the fungus. If there is an infected tassel, it is likely that the ears will also have head smut.
Life cycle.
Sporisorium reilianum is noted to have a sexual stage in its disease cycle similar to that of Ustilago maydis. Initial infections occur on roots of young seedlings. The pathogen develops systemically and is found on ear and tassel tissues as the host plant matures. At maturity teliospores can be found in the white sori of the infected heads of corn. These will be easily dispersed by the wind. Favorable nutritive soil and weather conditions around 23-30 C allows for germination of the teliospores in the soil. Generation of a four-celled basidium occurs, leading to haploid basidiospores that create sporidia. These sporidia fuse due to a compatibility or likeness that induces the formation of dikaryotic mycelium, which is infectious and parasitic. This intracellular mycelium can be found invaded in parts of the flowering development of the corn, and S. reilianum can completely decrease floral tissue due to an ability to detect floral induction.
S. reilianum is biotrophic in that it depends on the maize or sorghum for growth and survival. The inflorescence of the male or female parts of the plants, female being the ear and the male being the tassel can be affected by the timing of infection by this species. Necrosis and disease development is most prevalent on the head of the infected host.