Fusarium ear blight

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Symptom on wheat caused by F. graminearum (right: inoculated, left: non-inoculated) Wheat scab.jpg
Symptom on wheat caused by F. graminearum (right: inoculated, left: non-inoculated)

Fusarium ear blight (FEB) (also called Fusarium head blight, FHB, or scab), is a fungal disease of cereals, including wheat, barley, oats, rye and triticale. [1] FEB is caused by a range of Fusarium fungi, which infects the heads of the crop, reducing grain yield. The disease is often associated with contamination by mycotoxins produced by the fungi already when the crop is growing in the field. The disease can cause severe economic losses as mycotoxin-contaminated grain cannot be sold for food or feed.

Contents

Causal organism

Fusarium ear blight is caused by several species of Fusarium fungi, belonging to the Ascomycota. The most common species causing FEB are: [1]

Fusarium graminearum was considered the most important causal organism. [3]

Macroconidia of F. graminearum F.graminearum.JPG
Macroconidia of F. graminearum

Fusarium species causing FEB can produce several types of spores. The asexual stage of the fungus produces spores called macroconidia. Some Fusarium fungi have a more complex life cycle including a sexual stage, for example F. graminearum. In the sexual stage the fungus produces spores called ascospores. The sexual stage form fruiting bodies called perithecia, in which ascospores are formed in a sac known as an ascus (plural asci). [3] Some species, including F. culmorum, produce resistant chlamydospores which can survive for a long time in the soil.

Disease cycle and epidemiology

Fusarium fungi can overwinter as saprotrophs in the soil or on crop debris that can serve as inoculum for the following crop. The fungus can also spread via infected seed. The presence of Fusarium fungi on crop debris or seed can cause Fusarium seedling blight and foot and root rot. [1] Later, infection of the heads can occur with spores spreading by rain splash from infected crop residues. Another major infection route is airborne inoculum as spores can travel long distances with the wind. [4] The cereal crop is most susceptible at flowering and the probability of infection rises with high moisture and humidity at flowering. [3]

Symptoms

In wheat, Fusarium infects the head (hence the name "Fusarium head blight") and causes the kernels to shrivel up and become chalky white. Additionally, the fungus can produce mycotoxins that further reduce the quality of the kernel.

Infected florets (especially the outer glumes) become slightly darkened and oily in appearance. Macroconidia are produced in sporodochia, which gives the spike a bright pink or orange color. Infected kernels may be permeated with mycelia and the surface of the florets totally covered by white, matted mycelia.

Mycotoxins

Fusarium species associated with FEB produce a range of mycotoxins—fungal secondary metabolites with toxic effects on animals. One mycotoxin can be produced by several Fusarium species, and one species can produce several mycotoxins. Important Fusarium mycotoxins include:

Fusarium toxins have negative effects on the immune, gastrointestinal and reproductive systems of animals. [5] DON is a protein synthesis inhibitor, also called vomitoxin, due to its negative effects on feed intake in pigs. Pigs are the most sensitive to DON, while ruminant animals such as cattle have higher tolerance. [6]

Many countries monitor Fusarium mycotoxins in grain to limit negative health effects. In the U.S. there are advisory levels for DON in human food and livestock feed. [7] The European Union has legislative limits for several Fusarium mycotoxins in grain aimed for human consumption [8] and recommended limits for animal feed. [9]

Control measures

Resistant cultivars

Resistant cultivars could be the most efficient method to control Fusarium ear blight. [10] Resistance breeding involves screening of plant lines subjected to artificial inoculation with Fusarium. Plant lines having reduced fungal growth and low levels of seed mycotoxin contamination are selected for additional breeding trials. In parallel, genetic markers associated with resistance are screened for, so called marker-assisted selection. Fusarium ear blight resistance is a complex trait, involving several genes, and is dependent of interaction with the environment. [11] [12]

Fusarium ear blight resistance has been identified in wheat cultivars from Asia. However, the challenge is to combine resistant material with other desirable traits such as high yield and adaptation to different growing areas. [11]

Agricultural practices

Several agricultural practices affect the risk of FEB. One of the major infection routes are infected crop residues from the previous crop where both the quality and quantity are important. Crop residues from susceptible crops such as cereals increase the risk of FEB in the following crop. Maize has been associated with especially high risk. [13] Reduced soil tillage can also increase the risk of FEB. [3] The amount of crop residues can be reduced by ploughing, where residues are incorporated in the soil where they decompose faster. [14] High nitrogen application has also been associated with increased risk of Fusarium infection. [15] Preventive agricultural practices may be less effective if a lot of airborne inoculum is present in the area. [3]

Chemical control

Fungicides can provide partial control of FEB but the effects may be variable. [3] The type and timing of fungicide application is important as non-optimal applications may even increase Fusarium infection. [16]

Biological control and integrated management

Research has also been put into development on biological control strategies based on bacteria and fungi for example, Bacillus and Cryptococcus species. [17]

For FEB no control measure is completely effective and integrated management involving several control strategies such as preventive measures, disease monitoring and chemical control is necessary. [18] [19] Disease forecasting models have been developed to assess the risk of FEB depending on weather conditions. [20]

Economic importance

From an economic standpoint, it is one of the major cereal diseases, being responsible for significant grain yield reduction world-wide.

In the U.S. and Canada, Fusarium ear blight emerged in the 1990s as a widespread and powerful threat to cereal production. [21] From 1998 to 2000 the Midwestern United States suffered $2.7 billion in losses following a FEB epidemic. [22] If we include primary and secondary economic losses, FHB cost the entire US$7.67 billion from 1993 to 2001. [23] Since 1990, extensive research has been put into the development of control measures of Fusarium ear blight. An example is the US Wheat and Barley Scab Initiative (USWBSI), a collaborative effort of scientists, growers, food processors and consumer groups aiming to develop effective control measures, including the reduction of mycotoxins. [21]

See also

Related Research Articles

A mycotoxin is a toxic secondary metabolite produced by fungi and is capable of causing disease and death in both humans and other animals. The term 'mycotoxin' is usually reserved for the toxic chemical products produced by fungi that readily colonize crops.

<i>Fusarium</i> Genus of fungi

Fusarium is a large genus of filamentous fungi, part of a group often referred to as hyphomycetes, widely distributed in soil and associated with plants. Most species are harmless saprobes, and are relatively abundant members of the soil microbial community. Some species produce mycotoxins in cereal crops that can affect human and animal health if they enter the food chain. The main toxins produced by these Fusarium species are fumonisins and trichothecenes. Despite most species apparently being harmless, some Fusarium species and subspecific groups are among the most important fungal pathogens of plants and animals.

<span class="mw-page-title-main">Khorasan wheat</span> Species of grass

Khorasan wheat or Oriental wheat is a tetraploid wheat species. The grain is twice the size of modern-day wheat, and has a rich, nutty flavor.

<i>Fusarium culmorum</i> Fungal disease, head blight of wheat

Fusarium culmorum is a fungal plant pathogen and the causal agent of seedling blight, foot rot, ear blight, stalk rot, common root rot and other diseases of cereals, grasses, and a wide variety of monocots and dicots. In coastal dunegrass, F. culmorum is a nonpathogenic symbiont conferring both salt and drought tolerance to the plant.

Glomerella graminicola is an economically important crop parasite affecting both wheat and maize where it causes the plant disease Anthracnose Leaf Blight.

Alternaria triticina is a fungal plant pathogen that causes leaf blight on wheat. A. triticina is responsible for the largest leaf blight issue in wheat and also causes disease in other major cereal grain crops. It was first identified in India in 1962 and still causes significant yield loss to wheat crops on the Indian subcontinent. The disease is caused by a fungal pathogen and causes necrotic leaf lesions and in severe cases shriveling of the leaves.

<i>Pyrenophora tritici-repentis</i> Species of fungus

Pyrenophora tritici-repentis (teleomorph) and Drechslera tritici-repentis (anamorph) is a necrotrophic plant pathogen of fungal origin, phylum Ascomycota. The pathogen causes a disease originally named yellow spot but now commonly called tan spot, yellow leaf spot, yellow leaf blotch or helminthosporiosis. At least eight races of the pathogen are known to occur based on their virulence on a wheat differential set.

<i>Gibberella zeae</i> Species of fungus

Gibberella zeae, also known by the name of its anamorph Fusarium graminearum, is a fungal plant pathogen which causes fusarium head blight (FHB), a devastating disease on wheat and barley. The pathogen is responsible for billions of dollars in economic losses worldwide each year. Infection causes shifts in the amino acid composition of wheat, resulting in shriveled kernels and contaminating the remaining grain with mycotoxins, mainly deoxynivalenol (DON), which inhibits protein biosynthesis; and zearalenone, an estrogenic mycotoxin. These toxins cause vomiting, liver damage, and reproductive defects in livestock, and are harmful to humans through contaminated food. Despite great efforts to find resistance genes against F. graminearum, no completely resistant variety is currently available. Research on the biology of F. graminearum is directed towards gaining insight into more details about the infection process and reveal weak spots in the life cycle of this pathogen to develop fungicides that can protect wheat from scab infection.

Crown rot of wheat is caused by the fungal pathogen Fusarium pseudograminearum. F. pseudograminearum is a member of the fungal phylum Ascomycota and is also known as Gibberella coronicola (teleomorph). It is a monoecious fungus, meaning it does not require another host other than wheat to complete its life cycle. Although F. pseudograminearum can produce both anamorphic and teleomorphic states, the teleomorph is usually not present for crown rot of wheat. This Fusarium species has, until recently, been considered to be the same as the species known as Fusarium graminearum due to many similar characteristics. One of the only differences between the two species is that F. pseudograminearum lacks its sexual stage on the wheat host.

Fusarium incarnatum is a fungal pathogen in the genus Fusarium, family Nectriaceae. It is usually associated with over 40 phylogenetic species in the natural environment to form the Fusarium incarnatum-equiseti species complex(FIESC). This complex is widespread across the globe in subtropical and temperate regions, resulting in many reported cases of crop diseases. It produces various mycotoxins including trichothecenes zearalenone, causing both plant and animal diseases.

Fusarium sporotrichioides is a fungal plant pathogen, one of various Fusarium species responsible for damaging crops, in particular causing a condition known as Fusarium head blight in wheat, consequently being of notable agricultural and economic importance. The species is ecologically widespread, being found across tropical and temperate regions, and is a significant producer of mycotoxins, particularly trichothecenes. Although mainly infecting crops, F. sporotrichioides-derived mycotoxins can have repercussions for human health in the case of the ingestion of infected cereals. One such example includes the outbreak of alimentary toxic aleukia (ATA) in Russia, of which F. sporotrichioides-infected crop was suspected to be the cause. Although current studies on F. sporotrichioides are somewhat limited in comparison to other species in the genus, Fusarium sporotrichioides has found several applications as a model system for experimentation in molecular biology.

Fusarium equiseti is a fungal species and plant pathogen on a varied range of crops.

Fusarium tricinctum is a fungal and plant pathogen of various plant diseases worldwide, especially in temperate regions. It is found on many crops in the world including malt barley, and cereals.

Fusarium crookwellense is a species of fungus in the family Nectriaceae. It is known as a plant pathogen that infects agricultural crops.

<span class="mw-page-title-main">Vomitoxin</span> Fungal toxic chemical in grains

Vomitoxin, also known as deoxynivalenol (DON), is a type B trichothecene, an epoxy-sesquiterpenoid. This mycotoxin occurs predominantly in grains such as wheat, barley, oats, rye, and corn, and less often in rice, sorghum, and triticale. The occurrence of deoxynivalenol is associated primarily with Fusarium graminearum and F. culmorum, both of which are important plant pathogens which cause fusarium head blight in wheat and gibberella or fusarium ear blight in corn. The incidence of fusarium head blight is strongly associated with moisture at the time of flowering (anthesis), and the timing of rainfall, rather than the amount, is the most critical factor. However, increased amount of moisture towards harvest time has been associated with lower amount of vomitoxin in wheat grain due to leaching of toxins. Furthermore, deoxynivalenol contents are significantly affected by the susceptibility of cultivars towards Fusarium species, previous crop, tillage practices, and fungicide use. It occurs abundantly in grains in Norway due to heavy rainfall.

Mycoestrogens are xenoestrogens produced by fungi. They are sometimes referred to as mycotoxins. Among important mycoestrogens are zearalenone, zearalenol and zearalanol. Although all of these can be produced by various Fusarium species, zearalenol and zearalanol may also be produced endogenously in ruminants that have ingested zearalenone. Alpha-zearalanol is also produced semisynthetically, for veterinary use; such use is prohibited in the European Union.

<span class="mw-page-title-main">Epoxiconazole</span> Fungicide

Epoxiconazole is a fungicide active ingredient from the class of azoles developed to protect crops. In particular, the substance inhibits the metabolism of fungi cells infesting useful plants, and thereby prevents the growth of the mycelia. Epoxiconazole also limits the production of conidia (mitospores). Epoxiconazole was introduced to the market by BASF SE in 1993 and can be found in many products and product mixtures targeting a large number of pathogens in various crops. Crops are, for example, cereals, soybeans, banana, rice, coffee, turnips, and red as well as sugar beets.

Many species of fungi produce secondary metabolites called mycotoxins. These toxins can be very detrimental to both humans and animals. The side-effects of ingesting these toxic substances are called mycotoxicosis, which can be a variety of medical conditions. The most common fungi that produce mycotoxins include Fusarium, Aspergillus, and Penicillium.

<span class="mw-page-title-main">Fusarin</span>

Fusarins are a class of mycotoxins produced mainly by fungi of the genus Fusarium, which can infect agriculturally important crops such as wheat, barley, oats, rye, and corn. Chemically, they are polyketides that are also derived from amino acids.

<i>Stenocarpella maydis</i> Species of fungus

Stenocarpella maydis (Berk.) Sutton is a plant pathogenic fungus and causal organism of diplodia ear and stalk rot. Corn and canes are the only known hosts to date. No teleomorph of the fungus is known.

References

  1. 1 2 3 Parry, D. W.; Jenkinson, P.; McLeod, L. (1995). "Fusarium ear blight (scab) in small grain cereals—a review". Plant Pathology. 44 (2): 207–238. doi:10.1111/j.1365-3059.1995.tb02773.x. ISSN   1365-3059.
  2. ↑ Wang, Yun; Wang, Ruoyu; Sha, Yuexia (26 July 2022). "Distribution, pathogenicity and disease control of Fusarium tricinctum". Frontiers in Microbiology. 13: 939927. doi: 10.3389/fmicb.2022.939927 . PMC   9360978 . PMID   35958126.
  3. 1 2 3 4 5 6 "Fusarium head blight (FHB) or scab". APSnet Feature Articles. 2003. doi:10.1094/phi-i-2003-0612-01. Archived from the original on 2012-02-03. Retrieved 2011-12-21.
  4. ↑ Keller, Melissa D.; Bergstrom, Gary C.; Shields, Elson J. (2014-06-01). "The aerobiology of Fusarium graminearum". Aerobiologia. 30 (2): 123–136. doi:10.1007/s10453-013-9321-3. ISSN   0393-5965. S2CID   84048532.
  5. ↑ D’Mello, J.P.F.; Placinta, C.M.; Macdonald, A.M.C. (1999). "Fusarium mycotoxins: a review of global implications for animal health, welfare and productivity". Animal Feed Science and Technology. 80 (3–4): 183–205. CiteSeerX   10.1.1.453.2615 . doi:10.1016/s0377-8401(99)00059-0.
  6. ↑ Miller, J. David (2008-02-01). "Mycotoxins in small grains and maize: Old problems, new challenges". Food Additives & Contaminants: Part A. 25 (2): 219–230. doi: 10.1080/02652030701744520 . ISSN   1944-0049. PMID   18286412. S2CID   32428433.
  7. ↑ Nutrition, Center for Food Safety and Applied. "Chemical Contaminants, Metals, Natural Toxins & Pesticides - Guidance for Industry and FDA: Advisory Levels for Deoxynivalenol (DON) in Finished Wheat Products for Human Consumption and Grains and Grain By-Products used for Animal Feed". www.fda.gov. Retrieved 2017-03-13.
  8. ↑ "EUR-Lex - 32006R1881 - EN - EUR-Lex". eur-lex.europa.eu. Retrieved 2017-03-13.
  9. ↑ "EUR-Lex - 32006H0576 - EN - EUR-Lex". eur-lex.europa.eu. 2006-08-23. Retrieved 2017-03-13.
  10. ↑ Steiner, Barbara; Buerstmayr, Maria; Michel, Sebastian; Schweiger, Wolfgang; Lemmens, Marc; Buerstmayr, Hermann (2017-02-21). "Breeding strategies and advances in line selection for Fusarium head blight resistance in wheat". Tropical Plant Pathology. 42 (3): 165–174. doi: 10.1007/s40858-017-0127-7 . ISSN   1983-2052.
  11. 1 2 Bai GH, Shaner GE (2004) Management and resistance in wheat Bai GH, Shaner GE (2004) Management and resistance in wheat 42:135–161
  12. ↑ Buerstmayr, H.; Ban, T.; Anderson, J. A. (2009-02-01). "QTL mapping and marker-assisted selection for Fusarium head blight resistance in wheat: a review". Plant Breeding. 128 (1): 1–26. doi: 10.1111/j.1439-0523.2008.01550.x . ISSN   1439-0523.
  13. ↑ Dill-Macky, R.; Jones, R. K. (2000-01-01). "The Effect of Previous Crop Residues and Tillage on Fusarium Head Blight of Wheat". Plant Disease. 84 (1): 71–76. doi: 10.1094/PDIS.2000.84.1.71 . ISSN   0191-2917. PMID   30841225.
  14. ↑ Leplat, Johann; Friberg, Hanna; Abid, Muhammad; Steinberg, Christian (2013-01-01). "Survival of Fusarium graminearum, the causal agent of Fusarium head blight. A review" (PDF). Agronomy for Sustainable Development. 33 (1): 97–111. doi:10.1007/s13593-012-0098-5. ISSN   1774-0746. S2CID   21709401.
  15. ↑ Bernhoft, A.; Torp, M.; Clasen, P.-E.; Løes, A.-K.; Kristoffersen, A. B. (2012-07-01). "Influence of agronomic and climatic factors on Fusarium infestation and mycotoxin contamination of cereals in Norway". Food Additives & Contaminants: Part A. 29 (7): 1129–1140. doi:10.1080/19440049.2012.672476. ISSN   1944-0049. PMC   3379782 . PMID   22494553.
  16. ↑ Henriksen, B.; Elen, O. (2005-04-01). "Natural Fusarium Grain Infection Level in Wheat, Barley and Oat after Early Application of Fungicides and Herbicides". Journal of Phytopathology. 153 (4): 214–220. doi: 10.1111/j.1439-0434.2005.00955.x . ISSN   1439-0434.
  17. ↑ Gilbert, Jeannie; Haber, Steve (2013-04-01). "Overview of some recent research developments in fusarium head blight of wheat". Canadian Journal of Plant Pathology. 35 (2): 149–174. doi:10.1080/07060661.2013.772921. ISSN   0706-0661. S2CID   83784062.
  18. ↑ "ScabSmart | Management". scabsmart.org. Retrieved 2017-03-14.
  19. ↑ Food Standards Agency (2007). The UK Code of Good Agricultural Practice to Reduce Fusarium Mycotoxins in Cereals (PDF). Archived from the original (PDF) on 2017-03-15. Retrieved 2017-03-14.
  20. ↑ "Risk Map Tool". www.wheatscab.psu.edu. Retrieved 2017-03-14.
  21. 1 2 McMullen, Marcia; Bergstrom, Gary; De Wolf, Erick; Dill-Macky, Ruth; Hershman, Don; Shaner, Greg; Van Sanford, Dave (2012-07-11). "A Unified Effort to Fight an Enemy of Wheat and Barley: Fusarium Head Blight". Plant Disease. 96 (12): 1712–1728. doi: 10.1094/PDIS-03-12-0291-FE . ISSN   0191-2917. PMID   30727259.
  22. ↑ "Diverse Wheat Tapped for Antifungal Genes : USDA ARS". www.ars.usda.gov. Retrieved 2017-03-05.
  23. ↑ Rawat, Nidhi; Pumphrey, Michael O; Liu, Sixin; Zhang, Xiaofei; Tiwari, Vijay K; Ando, Kaori; Trick, Harold N; Bockus, William W; Akhunov, Eduard; Anderson, James A; Gill, Bikram S (2016-10-24). "Wheat Fhb1 encodes a chimeric lectin with agglutinin domains and a pore-forming toxin-like domain conferring resistance to Fusarium head blight". Nature Genetics . 48 (12). Nature Research: 1576–1580. doi:10.1038/ng.3706. ISSN   1061-4036. PMID   27776114. S2CID   4177196.

Return of an old problem: Fusarium head blight of small grains

Fusarium head blight in Canada

United States Wheat and Barley Scab Initiative

Fusarium Head Blight Risk Assessment Tool

Scab Smart

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