Sporisorium sorghi
Sporisorium sorghi | |
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Scientific classification ![]() | |
Domain: | Eukaryota |
Kingdom: | Fungi |
Division: | Basidiomycota |
Class: | Ustilaginomycetes |
Order: | Ustilaginales |
Family: | Ustilaginaceae |
Genus: | Sporisorium |
Species: | S. sorghi
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Binomial name | |
Sporisorium sorghi | |
Synonyms | |
Cintractia sorghi-vulgaris (Tul. & C.Tul.) G.P.Clinton (1897) |
Sporisorium sorghi, commonly known as sorghum smut,
Taxonomy
A collection of S. sorghi on sorghum grass allowed Ehrenberg to establish the genus Sporisorium in 1825. This genus was replaced by Sphacelotheca, a genus established by de Bary. Soon after, G. P. Clinton transferred Sporisorium to this genus instead, giving it the name Sphacelotheca sorghi.[3] Ontogeny studies provide evidence that Sporisorium is restricted to parasitic smut fungi. This support allowed for the reinstatement of the Sporisorium genus by Langdon & Fullerton and for the reclassification of S. sorghi into this genus.[3] Other members of Sphacelotheca were also renamed to Sporisorium after proving they were harmful to grasses.[4] Ustilago and Sporisorium genera are closely related, but descriptions made by Link and Langdon & Fullerton allow for a taxonomic boundary of these genera based on variation in columellae, sterile cells, and spore balls.[5] Vánky transferred species within Ustilago to Sporisorium following this differentiation.[4]
Hosts and symptoms
Susceptible hosts of Sporisorium sorghi infection consist of all groups of
or covered kernel smut disease.Symptoms of infection by S. sorghi are typically expressed as the plant matures and begins to
Life cycle
Planting of a sorghum kernel infected with S. sorghi leads to the development of fungal structures that occur alongside the growth of the plant. These seedborne structures are known as teliospores, and they germinate as the sorghum plant matures by colonizing plant tissues and the apical meristem.[7] No signs of fungal growth arise until plant maturation, or heading. At harvest time, the membranes surrounding the sori of infected kernels rupture. This releases the teliospores inside, allowing them to adhere to the surface of healthy seeds on other plants.[8] Teliospores that do this will overwinter, where they remain in a dormant state and resume their pathogenicity when conditions resume being favorable. Some teliospores, when released will go on to contaminate soils. Because spores must be seed-borne in order to cause infection, soilborne teliospores are insignificant in terms of seedling infections.[8]
Conditions suited for delayed germination of sorghum seedlings provide optimum conditions for S. sorghi infection. Because spore formation occurs as seedlings mature, S. sorghi attempts to avoid environments that allow the plants to grow rapidly and escape infection.[9] Temperatures ranging from 20-30 degrees Celsius allow maximum spore production.[6] Warm, wet soils outside of this temperature range (15.5-33.2 degrees C) have been shown to decrease the incidence of seedling infection. A variety of other factors such as host variability and depth of seedling sowing also affect the prevalence at which infection occurs.[6]
Distribution
Sorghum grains are found in all regions of the world as they act as a major food crop for both humans and livestock in areas with little precipitation and high temperatures.[10] Covered kernel smut disease has been reported in all continents, and is found to be the most common smut disease in areas where untreated seeds are planted. Asia and Africa combined account for more than 80% of sorghum production in the world, making these two continents especially susceptible to S. sorghi infection.[10] In sorghum-growing states of India, S. sorghi infection has become one of the most serious diseases.[6]
Prevention and control
To effectively manage the spread of disease caused by S. sorghi, the presence of S. sorghi infection must be detected early on in sorghum development. Symptoms of infection don’t present themselves until heading occurs, but research has demonstrated that microscopy and PCR techniques are useful in differentiating healthy from infected sorghum seedlings early on in their life cycle.[7] Knowing this information will be beneficial for the early detection of S. sorghi and the implementation of more effective control measures.
Currently, covered kernel smut and S. sorghi are controlled by using protectant fungicides to treat infected seeds. This method is very effective, reliable, and simple as it prevents the fungi from being introduced into an uninfected field of sorghum. However, in some less developed countries, this method is not sustainable as this practice is expensive and oftentimes not available.[9] In these instances, cultural methods may be used where seeds are soaked in water for four hours and then dried in the sun. Such methods keep intact seed viability while destroying spores.[11] S. sorghi spores can live in the soil for long periods of time so rotation of crops every four years is another method of control.[10] The burning of sorghum plants before the release of teliospores may be effective, although this does reduce crop yield. Planting the sorghum kernels in 15.5-32 degree Celsius soil further serves as a preventative measure that limits S. sorghi germination.[10]
Importance
The fungal spores of S. sorghi enter and grow within the
References
- ^ ISSN 2958-4329.
- ^ Zundel, The Ustilaginales of the World, p. 110, 1953; Fischer, Manual of the North American smut fungi, p. 149.
- ^ PMID 23606765.
- ^ ISSN 0006-8071.
- PMC 3589789.
- ^ ISSN 0253-1496.
- ^ ISSN 1876-7184.
- ^ a b c d e "Sorghum Smut | Texas Plant Disease Diagnostic Lab". plantclinic.tamu.edu. Retrieved 2023-05-04.
- ^ ISSN 0967-0874.
- ^ a b c d e Wagari, Michael (November 30, 2019). "Importance and Management of Sorghum Smuts". gjournals.org. Retrieved 2023-05-04.
- ISSN 1916-9760.