Botrytis allii

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Botrytis allii
Botrytis allii 5365841 SMPT.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Fungi
Division: Ascomycota
Class: Leotiomycetes
Order: Helotiales
Family: Sclerotiniaceae
Genus: Botrytis
Species:
B. allii
Binomial name
Botrytis allii
Munn (1917)
Synonyms [1]
Advanced infection and colonization of onion bulb tissue by the Botrytis fungus, note brown to gray discoloration of onion tissue, and formation of black sclerotial bodies between onion scale Botrytis rot (Botrytis allii) Munn.jpg
Advanced infection and colonization of onion bulb tissue by the Botrytis fungus, note brown to gray discoloration of onion tissue, and formation of black sclerotial bodies between onion scale

Botrytis allii is a plant pathogen, a fungus that causes neck rot in stored onions ( Allium cepa ) and related crops. Its teleomorph is unknown, but other species of Botrytis are anamorphs of Botryotinia species. [2] [3] The species was first described scientifically by Mancel Thornton Munn in 1917. [4]

Contents

Biology

There are seven different species of Botrytis associated with onions in storage, but the rot induced by B. allii and B. aclada causes the greatest commercial loss. The two can be distinguished microscopically; the conidia of B. allii have a maximum length of 15 μm and mean size of 10.2 × 5.7  μm, while the conidia of B. aclada have a maximum length of 12 μm and mean size of 8.6 × 4.6 μm. The infection is present in the field but does not manifest itself until after harvest, however there may be a falling off of vigour while the crop is still growing, particularly in cool, moist weather. In the stored crop, the rot typically starts in the neck of the bulb but can occur in other parts if there is physical injury. [3] The scales inside the bulb become progressively translucent and watery and a mycelium develops between them. A mass of grey conidiophores and conidia develop on the mycelium, and blackish sclerotia form at the site of the initial infection. [3]

In onion crops grown for the production of seed, Botrytis allii can cause spotting and girdling of the stipe (stem) and develop on the sheath that protects the inflorescence and on the flowers themselves. Concentric grey rings may form as the fungus sporulates and the crop may lodge (become flattened). [3]

It has been shown that a major source of the pathogen is infected seed. In 1973, 71% of commercially available seed was found to be contaminated, and the infection was found to persist for over three years in seeds being stored. In the seedling, infection with B. allii does not produce any symptoms, but the fungus spreads between plants as the conidiophores release spores into the air. The leaf tips are invaded first, the infection spreading down the leaves and into the neck of the bulb, where its presence only becoming apparent when the foliage dies down at the end of the season. [5]

Hosts

Botrytis allii grows on Allium species, including onion (A. cepa), aggregating onion (A. cepa var. aggregatum), shallot (A. cepa var. ascalonicum), garlic (A. sativum) and leek (A. porrum). It may also infect wild Allium species and can grow saprophytically on decaying crop residues such as cereal, pea and bean straw. It is capable of colonizing and producing spores on sterilized poppy straw ( Papaver somniferum ). [3]

Commercial importance

Neck rot caused by Botrytis allii occurs in regions all over the world, but, it is most prevalent in temperate regions due to their conducive climates. [6] Botrytis allii used to cause significant losses in the onion bulb industry in the UK. Fortunately, by utilization of better harvesting and curing methods, the disease prevalence has decreased. [7] It is important that the US utilize these methods as well because the onion is a highly produced agronomic crop. In 2005, the US grew 65,000 hectares of onions with a farm gate value of $922 million. Botrytis allii poses a threat to that value because it can potentially cause a 50% reduction in yield if left unchecked. [6] These losses caused by the disease may be even greater than reported. Detection of this disease is difficult due to the morphologically indistinguishable characteristics of Botrytis species cultured on agar. [6] Higher quality detection methods of Botrytis allii are starting to be implemented to better differentiate it from other closely related Botrytis species. Within the last 15 years, scientists have been able to get a more accurate picture of Botrytis allii distribution through the use of PCR-RFLP detection methods.

Management

Botrytis allii’s main agronomic host is the onion (Allium cepa). In order to control this disease, most agriculturalists utilize the fungicide benomyl [8] . Benomyl is applied directly to the seed, as a pretreatment, before planting. However, the pretreatment must be used in addition to correct farming practices to further minimize the spread of Botrytis allii spores. For instance, benomyl works best if you dry the onions in a 30 °C (86 °F) environment after harvest. Lower drying temperatures, such as 18 °C (64 °F), during the post harvest period have been known to increase disease presence. In addition, removal of the onions from the field in the first 48 hours after mechanical removal of the top has also shown to lower post harvest disease. [8] Moreover, it is important to pay attention to your fertilization schedule. High levels of nitrogen fertilizer during the growing season may cause delayed maturity. This is an issue because the onions that have the best chance of avoiding disease are the ones that have reached full maturity by the time they are harvested. [9] Crop rotations can also help control disease outbreak. [9] The rotation should take place over at least two years and crops not related to onions should be planted. Onion fields should be separated from each other because the spores of Botrytis allii are able to travel far distances.

Pathogenesis

Botrytis allii is able to use polysaccharide-degrading enzymes to enter their onion host. [10] These enzymes are able to degrade onion cell wall components such as sodium polypectate, citrus pectin, lupin galactan, araban, xylan and carboxymethyl cellulose. The most active enzyme that Botrytis allii uses is polygalacturonase, which is used to degrade sodium polypectate. When the fungus attempts to penetrate the epidermal cells of the onion, there is an observed accumulation of granular deposits, called reaction material, that are found between the cell wall and plasma membrane. [11] The reaction material correlates with reduced fungal growth between the cell walls where it is found. During infection, the onion will also produce hydroxycinnamic acid amide, which is a common plant defense response. There may also be some cytoskeletal rearrangements within the onion so that it can provide a better route to deliver the phenolic products to the fungal penetration site. [11]

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An onion, also known as the bulb onion or common onion, is a vegetable that is the most widely cultivated species of the genus Allium. The shallot is a botanical variety of the onion which was classified as a separate species until 2011. Its close relatives include garlic, scallion, leek, and chive.

<i>Botrytis cinerea</i> Species of fungus

Botrytis cinerea is a necrotrophic fungus that affects many plant species, although its most notable hosts may be wine grapes. In viticulture, it is commonly known as "botrytis bunch rot"; in horticulture, it is usually called "grey mould" or "gray mold".

<span class="mw-page-title-main">Sclerotium</span> Mycelial mass

A sclerotium, is a compact mass of hardened fungal mycelium containing food reserves. One role of sclerotia is to survive environmental extremes. In some higher fungi such as ergot, sclerotia become detached and remain dormant until favorable growth conditions return. Sclerotia initially were mistaken for individual organisms and described as separate species until Louis René Tulasne proved in 1853 that sclerotia are only a stage in the life cycle of some fungi. Further investigation showed that this stage appears in many fungi belonging to many diverse groups. Sclerotia are important in the understanding of the life cycle and reproduction of fungi, as a food source, as medicine, and in agricultural blight management.

<span class="mw-page-title-main">White onion</span> Onion cultivar

White onion or Allium cepa are a cultivar of dry onion which have a distinct light and mild flavour profile. Much like red onions, they have a high sugar and low sulphur content, and thus have a relatively short shelf life. White onions are used in a variety of dishes, such as those of Mexican and European origin. Their uses in dishes often relate to their mild nature, they are often included in dishes to provide a light, fresh and sour taste to dishes and are often added uncooked to dishes such as salads.

<i>Botryotinia</i> Genus of fungi

Botryotinia is a genus of ascomycete fungi causing several plant diseases. The anamorphs of Botryotinia are mostly included in the "imperfect fungi" genus Botrytis. The genus contains 22 species and one hybrid.

<i>Monilinia fructicola</i> Species of fungus

Monilinia fructicola is a species of fungus in the order Helotiales. A plant pathogen, it is the causal agent of brown rot of stone fruits.

<i>Rhizoctonia solani</i> Species of fungus

Rhizoctonia solani is a species of fungus in the order Cantharellales. Basidiocarps are thin, effused, and web-like, but the fungus is more typically encountered in its anamorphic state, as hyphae and sclerotia. The name Rhizoctonia solani is currently applied to a complex of related species that await further research. In its wide sense, Rhizoctonia solani is a facultative plant pathogen with a wide host range and worldwide distribution. It causes various plant diseases such as root rot, damping off, and wire stem. It can also form mycorrhizal associations with orchids.

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

<i>Leveillula taurica</i> Species of fungus

Leveillula taurica is an obligate fungal pathogen, from the phylum Ascomycota, which causes powdery mildew on onion. This disease prefers warm, dry environments. It is rare in the United States, and is currently restricted to western states. Globally, it is also a minor problem with limited occurrences in the Middle East, Europe, and South America. L. taurica causes powdery mildew of onions, but is also known to infect other allium, solanaceous, and cucurbit species. The disease has appeared in parts of the Middle East, the Mediterranean, and South and North America. Currently, it is not a cause for major concern in the U.S. and throughout the world, as its geographic extent is sparse. In addition, it is relatively easy to control through basic sanitation and reducing water stress.

<i>Ascochyta</i> Genus of fungi

Ascochyta is a genus of ascomycete fungi, containing several species that are pathogenic to plants, particularly cereal crops. The taxonomy of this genus is still incomplete. The genus was first described in 1830 by Marie-Anne Libert, who regarded the spores as minute asci and the cell contents as spherical spores. Numerous revisions to the members of the genus and its description were made for the next several years. Species that are plant pathogenic on cereals include, A. hordei, A. graminea, A. sorghi, A. tritici. Symptoms are usually elliptical spots that are initially chlorotic and later become a necrotic brown. Management includes fungicide applications and sanitation of diseased plant tissue debris.

Mycosphaerella cruenta, also called Pseudocercosopora cruenta in its asexual stage, is a fungal plant pathogen belonging to the group Ascomycota. It can affect several legume plants, including species of Phaseolus, Vigna, Calopogonium, Lablab niger, Mucuna and Stizolobium deeringianum [Mucuna pruriens][2]. It causes cowpea cercospora leaf spot, one of the most widespread and significant plant diseases in Africa and Asia. A city in China reported a 100% Mycosphaerella cruenta infection rate on cowpea in 2014[5]. In Africa, an epidemic can cause a yield loss of up to 40% [3].

<i>Alternaria solani</i> Species of fungus

Alternaria solani is a fungal pathogen that produces a disease in tomato and potato plants called early blight. The pathogen produces distinctive "bullseye" patterned leaf spots and can also cause stem lesions and fruit rot on tomato and tuber blight on potato. Despite the name "early," foliar symptoms usually occur on older leaves. If uncontrolled, early blight can cause significant yield reductions. Primary methods of controlling this disease include preventing long periods of wetness on leaf surfaces and applying fungicides. Early blight can also be caused by Alternaria tomatophila, which is more virulent on stems and leaves of tomato plants than Alternaria solani.

This article summarizes different crops, what common fungal problems they have, and how fungicide should be used in order to mitigate damage and crop loss. This page also covers how specific fungal infections affect crops present in the United States.

<i>Peronospora destructor</i> Species of single-celled organism

Peronospora destructor is a plant pathogen. It causes downy mildew on leaves of cultivated and wild Allium. Allium cepa is most often affected, while Allium schoenoprasum (chives) and Allium porrum (leek) are only occasionally affected.

Stromatinia cepivora is a fungus in the division Ascomycota. It is the teleomorph of Sclerotium cepivorum, the cause of white rot in onions, garlic, and leeks. The infective sclerotia remain viable in the soil for many years and are stimulated to germinate by the presence of a susceptible crop.

<i>Botrytis</i> (fungus) Genus of fungi

Botrytis is a genus of anamorphic fungi in the family Sclerotiniaceae. Botrytis belongs to the group hyphomycetes and has about 30 different species. It is a plant parasite as well as saprophytes on both agricultural and forest trees. It produces stout, dark, branching conidiophores that bear clusters of paler conidia on denticles from apical ampullae. It is a common outdoor fungus and can be detected in spore trap samples. The fungus is often found growing on indoor plants. Although no mycotoxin has been reported from this fungus, it may cause hay fever, asthma and keratomycosis. The most common species is B. cinerea, which is a plant pathogen causing gray mould on a very broad range of hosts including some common ornamental plants, such as geranium, begonia, rose, lily, dogwood, rhododendron, dahlia, magnolia, camellia and fruits and produce. This fungus is mainly of outdoor origin, although it may be from growth on fruits or flowers brought in from outdoors. Some houseplants can be infected by this fungus, such as cyclamen, poinsettia, chrysanthemum, and gerbera. Other species of Botrytis may be present, such as B. peoniae on peonies, B. squamosa on onion, and B. tulipae on tulips. These species of Botrytis share some common characteristics in pathology and ecology.

A species of the genus of Penicillium which causes Blue Mold of Garlic on Allium sativum L. The genus name is derived from the Latin root penicillum, meaning "painter's brush", and refers to the chains of conidia this fungus produces that resemble a broom.

<i>Botrytis squamosa</i> Species of fungus which can damage onion crops

Botrytis squamosa is a fungus that causes leaf blight on onion that is distinctly characterized by the two stages – leaf spotting followed by blighting. The pathogen is an ascomycete that belongs to the family Sclerotiniaceae in the order Helotiales. The lesions start out as whitish streaks and take on a yellow tinge as they mature. They cause yield losses up to 30%. This fungus is endemic to the USA and has also been reported in Europe, Asia, and Australia. Typical management of this disease includes chemical fungicides with significant efforts being made to establish a means of biological control.

<i>Alternaria brassicicola</i> Species of fungus

Alternaria brassicicola is a fungal necrotrophic plant pathogen that causes black spot disease on a wide range of hosts, particularly in the genus of Brassica, including a number of economically important crops such as cabbage, Chinese cabbage, cauliflower, oilseeds, broccoli and canola. Although mainly known as a significant plant pathogen, it also contributes to various respiratory allergic conditions such as asthma and rhinoconjunctivitis. Despite the presence of mating genes, no sexual reproductive stage has been reported for this fungus. In terms of geography, it is most likely to be found in tropical and sub-tropical regions, but also in places with high rain and humidity such as Poland. It has also been found in Taiwan and Israel. Its main mode of propagation is vegetative. The resulting conidia reside in the soil, air and water. These spores are extremely resilient and can overwinter on crop debris and overwintering herbaceous plants.

<i>Botrytis elliptica</i> Species of fungus

Botrytis elliptica is a necrotrophic fungal pathogen which infects species of plants in the Lilium genus, causing the disease commonly known as Lily Gray Mold. The symptoms of Lily Gray Mold include the appearance of water-soaked spots on leaves which appear white and increase in darkness with age, ranging from gray to brown. These spots may cover the entire leaf, complemented with a gray webbing, containing the fungal spores. The leaves will appear wilted and branches may die back. In addition to leaves, petals, stems, and buds may be infected, and this gray webbing will eventually cover the plant, feigning the appearance of gray flowers. Infected buds often rot. Lily Gray Mold disease, if not properly treated, will appear each year with increasing vigor.

References

  1. ↑ Fresenius, G. (1850). Beiträge zur Mykologie (in German). Frankfurt, Germany: Heinrich Ludwig Brömmer Verlag. p. 16.
  2. ↑ "Botrytis allii Munn". Index Fungorum. CAB International . Retrieved 2013-03-30.
  3. 1 2 3 4 5 Chilvers, M. I.; du Toit, L. J. (2006). "Detection and Identification of Botrytis Species Associated with Neck Rot, Scape Blight, and Umbel Blight of Onion" (PDF). Plant Health Progress . 7: 38. doi:10.1094/PHP-2006-1127-01-DG. Archived from the original (PDF) on 2016-03-04. Retrieved 2013-03-31.
  4. ↑ "Botrytis allii Munn: 396, 1917". MycoBank. International Mycological Association . Retrieved 2013-03-31.
  5. ↑ Maude, R. B.; Presly, A. H. (1977). "Neck rot (Botrytis allii) of bulb onions". Annals of Applied Biology . 86 (2): 163–180. doi:10.1111/j.1744-7348.1977.tb01829.x.
  6. 1 2 3 Toit, Lindsey Du. "Botrytis Species Associated with Neck Rot, Scape Blight, and Umbel Blight of Onion." Detection and Identification of Botrytis Species Associated with Neck Rot, Scape Blight, and Umbel Blight of Onion. Plant Health Progress, 27 Aug. 2006. Web. 17 Nov. 2016.
  7. ↑ Koike, Steven T., P. Gladders, and A. O. Paulus. Vegetable Diseases: A Colour Handbook. London: Manson Pub., 2007. Print.
  8. 1 2 Maude, R.B., M.R. Shipway, A.H. Presly, and D. O'Connor. "The Effects of Direct Harvesting and Drying Systems on the Incidence and Control of Neck Rot (Botrytis Allii) in Onions." - MAUDE. N.p., 1984. Web. 27 Oct. 2016.
  9. 1 2 Mcdonald, Mary Ruth, Maria De Los Angeles Jaime, and Marilyn H.y. Hovius. "Management of Diseases of Onions and Garlic." Diseases of Fruits and Vegetables: Volume II (2004): 149-200. Web. 15 Nov. 2016.
  10. ↑ Mankarios, A.T., and J. Friend. "Polysaccharide-degrading Enzymes of Botrytis Allii and Sclerotium Cepivorum. Enzyme Production in Culture and the Effect of the Enzyme on Isolated Onion Cell Walls." Cell Wall Plant Polysaccharide-degrading Enzymes in Autolysis of Botrytis Cinerea. Science Direct, July 1980. Web. 14 Nov. 2016.
  11. 1 2 McLusky, S., M. Bennett, M. Beale, M. Lewis, P. Gaskin, and J. Mansfield. "Cell Wall Alterations and Localized Accumulation of Feruloyl-3′-methoxytyramine in Onion Epidermis at Sites of Attempted Penetration by Botrytis Allii Are Associated with Actin Polarisation, Peroxidase Activity and Suppression of Flavonoid Biosynthesis." Wiley Online Library . The Plant Journal, Mar. 1999. Web. 26 Oct. 2016.
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