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 |
Binomial name | |
Sporisorium sorghi | |
Synonyms | |
Cintractia sorghi-vulgaris(Tul. & C.Tul.) G.P.Clinton (1897) Contents |
Sporisorium sorghi, commonly known as sorghum smut, [1] is a plant pathogen that belongs to the Ustilaginaceae family. This fungus is the causative agent of covered kernel smut disease and infects sorghum plants all around the world such as Sorghum bicolor (S. vulgare) (sorghum), S. sudanense (Sudan grass), S. halepense (Johnson grass) and Sorghumvulgare var. technichum (broomcorn). [2] Ineffective control of S. sorghi can have serious economic and ecological implications.
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 Sphacelothecasorghi. [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]
Susceptible hosts of Sporisorium sorghi infection consist of all groups of sorghum plants. Main hosts include Sorghum bicolor, Sorghum caffrorum, Sorghum dochna, and Sorghum sudanense. [6] Incidences of infection in perennial grasses have also been reported. [7] S. sorghi is the causative agent of sorghum smut or covered kernel smut disease.
Symptoms of infection by S. sorghi are typically expressed as the plant matures and begins to head. At this time, grain kernels are replaced by fungal spore-producing structures known as sori. Smut sori are covered by a peridium, a tough membrane that appears grayish-brown in color. [6] The shape of sori, themselves, are generally oval or conical. Oftentimes sori appear as an elongated sorghum seed. Variations in the size of sori range anywhere from 0.4-1.3 cm long and 0.2-0.4 cm wide. [8] Glumes, or tiny leaves, will sometimes cover very small sori. They appear white, gray, or brown in color. In some instances, sori may have a striped appearance. Dark brown, powder-like masses of sori may be concentrated on a particular region of an infected head, or in some instances, all kernels of a smutted head can be destroyed. [8] Missing or distorted spikelets covered in sori on the sorghum panicles also indicate signs of infection in rare instances. [1]
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]
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]
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]
The fungal spores of S. sorghi enter and grow within the ovary of sorghum plants. Release of teliospores following sori membrane rupturing causes spores to contaminate other plants and nearby soils. Spores are long-lived structures that are difficult to eliminate. Without the use of seed treatments, S. sorghi infection can have serious economic and ecological impacts. [8] Small-scale farms and developing countries tend to have more restricted use of fungicides, and therefore see a greater incidence of S. sorghi infection. More than 100 million people in sub-Saharan Africa depend on sorghum as a staple food source, and over 500 people are dependent on sorghum in Africa and Asia combined. [10] In the early 1900s, S. sorghi infection was responsible for a loss of 3 million dollars across the U.S. [1] Loss of this plant by S. sorghi infection can be drastic in these parts of the world along with others.
Rusts are fungal plant pathogens of the order Pucciniales causing plant fungal diseases.
Corn smut is a plant disease caused by the pathogenic fungus Ustilago maydis. One of several cereal crop pathogens called smut, the fungus forms galls on all above-ground parts of corn species such as maize and teosinte. The infected corn is edible; in Mexico, it is considered a delicacy called huitlacoche, often eaten as a filling in quesadillas and other tortilla-based foods, as well as in soups.
The smuts are multicellular fungi characterized by their large numbers of teliospores. The smuts get their name from a Germanic word for 'dirt' because of their dark, thick-walled, and dust-like teliospores. They are mostly Ustilaginomycetes and comprise seven of the 15 orders of the subphylum. Most described smuts belong to two orders, Ustilaginales and Tilletiales. The smuts are normally grouped with the other basidiomycetes because of their commonalities concerning sexual reproduction.
Karnal bunt is a fungal disease of wheat, durum wheat, and triticale. The smut fungus Tilletia indica, a basidiomycete, invades the kernels and obtains nutrients from the endosperm, leaving behind waste products with a disagreeable odor that makes bunted kernels too unpalatable for use in flour or pasta. While Karnal bunt generally does not lead to devastating crop losses, it has the potential to dramatically decrease yield, and poses additional economic concerns through quarantines which limit the export of suspected infectious wheat products from certain areas, including the U.S. Several chemical control methods exist for Karnal bunt of wheat, but much work remains to be done in identifying resistant host varieties.
Sugarcane smut is a fungal disease of sugarcane caused by the fungus Sporisorium scitamineum. The disease is known as culmicolous, which describes the outgrowth of fungus of the stalk on the cane. It attacks several sugarcane species and has been reported to occur on a few other grass species as well, but not to a critical amount. The most recognizable characteristic of this disease is a black or gray growth that is referred to as a "smut whip". Resistance to sugarcane smut is the best course of action for management, but also the use of disease free seed is important. On smaller scale operations treatments using hot water and removing infected plants can be effective. The main mode of spore dispersal is the wind but the disease also spreads through the use of infected cuttings. Sugarcane smut is a devastating disease in sugarcane growing areas globally.
Common bunt, also known as hill bunt, Indian bunt, European bunt, stinking smut or covered smut, is a disease of both spring and winter wheats. It is caused by two very closely related fungi, Tilletia tritici and T. laevis.
Covered smut of barley is caused by the fungus Ustilago hordei. The disease is found worldwide and it is more extensively distributed than either loose smut or false loose smut.
Loose smut of barley is caused by Ustilago nuda. It is a disease that can destroy a large proportion of a barley crop. Loose smut replaces grain heads with smut, or masses of spores which infect the open flowers of healthy plants and grow into the seed, without showing any symptoms. Seeds appear healthy and only when they reach maturity the following season is it clear that they were infected. Systemic fungicides are the major control method for loose smut.
False loose smut is a fungal disease of barley caused by Ustilago nigra. This fungus is very similar to U. nuda, the cause of loose smut, and was first distinguished from it in 1932.
Tilletia caries is a basidiomycete that causes common bunt of wheat. The common names of this disease are stinking bunt of wheat and stinking smut of wheat. This pathogen infects wheat, rye, and various other grasses. T. caries is economically and agriculturally important because it reduces both the wheat yield and grain quality.
Urocystis agropyri is a fungal plant pathogen that causes flag smut on wheat.
Claviceps sorghi is a fungal plant pathogen belonging to the phylum Ascomycota in the kingdom Fungi- its anamorphic phase is known as sphacelia sorghi. This species was first found in In India in 1915 and officially recorded in 1948 . The Claviceps genus is known for their infection of cereal and millet crops. This particular species of Claviceps infects Sorghum- giving the fungus its name 'sorghi'. These species in Claviceps are known to produce ergot on their host, as a byproduct of their infection. This can cause the disease known as ergotism when the infected crop is consumed.
Ascochyta sorghi is a fungal plant pathogen. It causes Ascochyta leaf spot on barley that can also be caused by the related fungi Ascochyta hordei, Ascochyta graminea and Ascochyta tritici. It is considered a minor disease of barley.
Sporisorium reilianum Langdon & Full., (1978), previously known as Sphacelotheca reiliana, and Sporisorium reilianum, is a species of biotrophic fungus in the family Ustilaginaceae. It is a plant pathogen that infects maize and sorghum.
Peronosclerospora sorghi is a plant pathogen. It is the causal agent of sorghum downy mildew. The pathogen is a fungal-like protist in the oomycota, or water mold, class. Peronosclerospora sorghi infects susceptible plants though sexual oospores, which survive in the soil, and asexual sporangia which are disseminated by wind. Symptoms of sorghum downy mildew include chlorosis, shredding of leaves, and death. Peronosclerospora sorghi infects maize and sorghum around the world, but causes the most severe yield reductions in Africa. The disease is controlled mainly through genetic resistance, chemical control, crop rotation, and strategic timing of planting.
Tilletia horrida, rice kernel smut, caryopsis smut, black smut, or grain smut, is a fungal rice disease believed to only affect the Oryza genus. It presents as a partial bunt.
Salmacisia is a fungal genus in the family Tilletiaceae. It is a monotypic genus, containing the single species Salmacisia buchloëana, first described as Tilletia buchloëana in 1889, and renamed in 2008. Plants infected by the fungus undergo a phenomenon known as "parasitically induced hermaphroditism", whereby ovary development is induced in otherwise male plants. Because of the pistil-inducing effects of the fungus, the authors have named the species pistil smut; it is the only species in the order Tilletiales known to have hermaphroditic effects.
Entorrhizomycetes is the sole class in the phylum Entorrhizomycota, within the Fungi subkingdom Dikarya along with Basidiomycota and Ascomycota. It contains three genera and is a small group of teliosporic root parasites that form galls on plants in the Juncaceae (rush) and Cyperaceae (sedge) families. Prior to 2015 this phylum was placed under the subdivision Ustilaginomycotina. A 2015 study did a "comprehensive five-gene analyses" of Entorrhiza and concluded that the former class Entorrhizomycetes is possibly either a close sister group to the rest of Dikarya or Basidiomycota.
Macalpinomyces is a fungus genus in the Ustilaginaceae family.
The Doassansiaceae are a family of fungi in the division Basidiomycota and order of Doassansiales. The family contains 11 genera and about 58 species. They have a widespread distribution. Doassansiaceae is also known and classified as a smut fungi.