Glomerella graminicola | |
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Species: | G. graminicola |
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Glomerella graminicola D.J. Politis (1975) | |
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Colletotrichopsis graminicola(Ces.) Munt.-Cvetk. (1953) Contents |
Glomerella graminicola is an economically important crop parasite affecting both wheat and maize where it causes the plant disease Anthracnose Leaf Blight.
G. graminicola is an anamorphic fungus which is identified as Colletotrichum graminicola in the teleomorphic phase. It is the anamorphic phase that causes anthracnose in many cereal species. While the main host of this disease is maize, it can also affect other cereals and grasses, [1] such as sorghum, ryegrass, bluegrass, barley, wheat, and some cultivars of fescue where the production of fruiting bodies cause symptoms to appear in the host plant. [2] Corn anthracnose leaf blight is the most common stalk disease in maize and occurs most frequently in reduced-till or no-till fields. [3]
Symptoms can vary depending on which part of the growing season the corn is in. [4]
Early in the growing season, the main symptom is foliar leaf blight. This often appears as 1 inch (25 mm) long and 1⁄2 inch (13 mm) wide oval or spindle-shaped water-soaked lesions on the lower leaves of the plant. This tissue can become necrotic and has the potential to spread throughout the entire leaf, causing it to yellow and die. [5] They are light brown in color, with margins that appear dark brown or purple. If this persists, black fruiting bodies will appear in the center of the lesion. [6]
The mid-season symptoms appear several weeks after corn produces tassels, when there will be a top die-back if the infection has spread throughout many parts of the plant. [4] In this dieback, the entire plant will become necrotic and die, beginning at the tassel and working its way down the entire stalk to the lowest leaves.
Late in the growing season, another major symptom of this disease appears: stalk rot. [4] It can first be seen as a reflective black stripe on the internodes of the stalk, [7] and can make the stalk soft, causing the plants to easily lodge in heavy precipitation or a wind event.
Growth on potato dextrose agar is:
In the spring, fruiting structures (acervuli) form from corn residue and produce banana-shaped [8] spores (conidia) that are dispersed by wind blown raindrops and splashing. [9] Conidial spores infect young plants through the epidermis or stomata. [10] Anthracnose develops rapidly in cloudy, overcast conditions with high temperatures and humidity. In optimal environmental conditions, conidia can germinate in as little as 6–8 hours in 100% humidity. [9] Initial necrotic spots or lesions can be seen within 72 hours after infection by conidia. [11] Lower leaves that develop lesions provide conidial spores and cause secondary infections on the upper leaves and stalk. Vascular infections primarily occur from wounds caused by stalk-boring insects, such as the larvae of the European corn borer, allowing for conidia to infect and colonize the xylem. [12] From this, anthracnose top die back (vascular wilt) or stalk rot can occur. In the fall, C. graminicola survives as a saprophyte on corn leaf residue. The pathogen can also overwinter on corn stalks as conidia in an extracellular secretion. The secretion prevents conidia from desiccating and protects them from unfavorable environmental conditions. [9] Overwintering on corn residue serves as a vital source of primary inoculum for the leaf blight phase in the spring. The cycle will start all over again when susceptible corn seedlings emerge from the ground in the spring.
There are several conditions that favor the infection and persistence of anthracnose leaf blight. When high temperatures and long periods of wet weather or high humidity occur, these are the most ideal conditions for its spread and survival. [13] A specific temperature range is required in order for the pathogen to successfully infect the host plant, between 25 and 30 °C (77 and 86 °F). Two other things, those being prolonged periods of low sunlight due to overcast conditions, or an already weakened host due to the infection of other diseases or pests will also favor infection of the host plant. [14] In addition to this, there are two cultural practices that will also favor the disease. Continuous plantings of the same host without introducing crop rotation and no-till fields will favor persistence of the pathogen between growing seasons. [15]
Since C. graminicola is found to survive on corn residue, specifically on the soil surface, one of the most effective methods of control is a one-year minimum of crop rotation to reduce anthracnose leaf blight. [7] A study in 2009 showed more severe symptoms of leaf blight due to C. graminicola when grown on fields previously used for corn in comparison to fields previously used for soybean. [16] There are cultural practices that can be taken to disrupt the primary inoculum phase and conidial spore infection of the host plant, and these include using hybrid cultivars resistant to the pathogen [15] and keeping the host plants healthy and controlling other pests to keep them resilient to infection. While there are hybrids resistant to the leaf blight, these same hybrids are often not resistant to the stalk rot that occurs later in the growing season. [17] There is also a cultural practice that disrupts the saprophytic stage of the pathogen, and this involves plowing the leftover corn residue deep into the soil and then using a one-year crop rotation away from the same host plant that was just used in that field. [15] These methods move the saprophytic stage into the soil, where it is out-competed by other organisms, and does not survive. [16] Biological control may also be possible, though the large-scale implementation of this method has not been studied. This is done by applying yeasts to the leaf surfaces that are showing symptoms of the leaf blight. [9]
Corn anthracnose caused by C. graminicola is a disease present worldwide. This disease can affect all parts of the plant and can develop at any time during the growing season. This disease is typically seen in leaf blight or stalk rot form. Before the 1970s, Anthracnose was not an issue in North America. In the early 1970s, north-central and eastern U.S was hit with severe epidemics. Within 2 years of C. graminicola's appearance in Western-Indiana, sweet corn production for canning companies were nearly wiped out and production no longer exists there today. [9]
Anthracnose stalk rot was seen in many U.S corn fields in the 1980s and 1990s. A survey conducted in Illinois in 1982 and 1983 found that 34 to 46% of rotted corn stalks contained C. graminicola. [18] Estimates on yield grain losses from anthracnose leaf blight and stalk rot range from zero to over 40%. This is dependent on hybrid, environment, timing of infection, and other stresses.
Once conidia germinate on corn leaves, a germ tube differentiates and develops into an appresoria and allows C. graminicola to penetrate epidermal cells. [19] Germination and appressorium formation occur best in the temperature range 15–30 °C (59–86 °F)) [9] Penetration occurs in a much narrower temperature range 25–30 °C (77–86 °F). In order to penetrate the cell wall, the fungus first pumps melanin into the walls of the appressorium to create turgor pressure in the appressorium. The melanin allows water into the appressorium cell but nothing out. This builds up an incredible amount of turgor pressure which the fungus then uses to push a hyphae through the corn cell wall. This is called the penetration peg. The penetration peg then grows, extends through the cell extracting nutrients and the host cell wall dies. [10] Hyphae migrate from epidermal cells to mesophyll cells. As a defense response, the cells produce papillae to prevent cell entry but is typically not seen successful. It is believed C. graminicola has a biotrophic phase because the plasma membrane of the epidermal cells is not immediately penetrated after invasion into the epidermal cell wall. Between 48–72 hours after infection, C. graminicola shifted from biotrophic growth to nectrotrophy (lesions appear). This is when secondary hyphae invade cell walls and intercellular spaces. [11]
Colletotrichum acutatum is a plant pathogen and endophyte. It is the organism that causes the most destructive fungal disease, anthracnose, of lupin species worldwide. It also causes the disease postbloom fruit drop on many varieties of citrus, especially Valencia and navel oranges in Florida.
Colletotrichum kahawae is a fungal plant pathogen that causes coffee berry disease (CBD) on Coffea arabica crops. The pathogen is an ascomycete that reproduces asexually. The asexual spores (conidia) are stored within acervuli. This disease is considered to be one of the major factors hampering C.arabica production in the African continent, which represents the current geographic range of the fungus. Coffee berry disease causes dark necrosis in spots and causes the green berries of the coffee to drop prematurely. High humidity, relatively warm temperatures, and high altitude are ideal for disease formation. Given the severity of the disease and the lack of effective control measures, there is great concern that the fungus may spread to other coffee producing continents, such as South America, which could have catastrophic consequences.
Alternaria dauci is a plant pathogen. The English name of the disease it incites is "carrot leaf blight".
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.
Phomopsis obscurans is a common fungus found in strawberry plants, which causes the disease of leaf blight. Common symptoms caused by the pathogen begin as small circular reddish-purple spots and enlarge to form V-shaped lesions that follow the vasculature of the plant's leaves. Although the fungus infects leaves early in the growing season when the plants are beginning to develop, leaf blight symptoms are most apparent on older plants towards the end of the growing season. The disease can weaken strawberry plants through the destruction of foliage, which results in reduced yields. In years highly favorable for disease development, leaf blight can ultimately lead to the death of the strawberry plants. A favorable environment for the growth and development of the Phomopsis obscurans pathogen is that of high temperature, high inoculum density, a long period of exposure to moisture, and immature host tissue. In the case of disease management, a conjunction of cultural practices is the most effective way of reducing the infection.
Didymella bryoniae, syn. Mycosphaerella melonis, is an ascomycete fungal plant pathogen that causes gummy stem blight on the family Cucurbitaceae, which includes cantaloupe, cucumber, muskmelon and watermelon plants. The anamorph/asexual stage for this fungus is called Phoma cucurbitacearum. When this pathogen infects the fruit of cucurbits it is called black rot.
Colletotrichum capsici is a species of fungus and plant pathogen which causes leaf blight on Chlorophytum borivilianum, basil, chickpea and pepper as well as dieback in pigeonpea and anthracnose in poinsettia.
Colletotrichum coccodes is a plant pathogen, which causes anthracnose on tomato and black dot disease of potato. Fungi survive on crop debris and disease emergence is favored by warm temperatures and wet weather.
Colletotrichum lindemuthianum is a fungus which causes anthracnose, or black spot disease, of the common bean plant. It is considered a hemibiotrophic pathogen because it spends part of its infection cycle as a biotroph, living off of the host but not harming it, and the other part as a necrotroph, killing and obtaining nutrients from the host tissues.
Glomerella cingulata is a fungal plant pathogen, being the name of the sexual stage (teleomorph) while the more commonly referred to asexual stage (anamorph) is called Colletotrichum gloeosporioides. For most of this article the pathogen will be referred to as C. gloeosporioides. This pathogen is a significant problem worldwide, causing anthracnose and fruit rotting diseases on hundreds of economically important hosts.
Colletotrichum cereale is a plant disease (fungus) that has been found to cause crown rot anthracnose of turf grass most commonly occurring on golf courses. Anthracnose can occur as both a foliar blight and basal rot. This disease attacks the crowns of plants, which is different than other anthracnose diseases. Anthracnose of turfgrass can be a foliar disease or in this case a basal rot of the lower portion of the plant. It attacks different species of turfgrass throughout the world most commonly annual bluegrass and creeping bentgrass.
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.
Grey leaf spot (GLS) is a foliar fungal disease that affects maize, also known as corn. GLS is considered one of the most significant yield-limiting diseases of corn worldwide. There are two fungal pathogens that cause GLS: Cercospora zeae-maydis and Cercospora zeina. Symptoms seen on corn include leaf lesions, discoloration (chlorosis), and foliar blight. Distinct symptoms of GLS are rectangular, brown to gray necrotic lesions that run parallel to the leaf, spanning the spaces between the secondary leaf veins. The fungus survives in the debris of topsoil and infects healthy crops via asexual spores called conidia. Environmental conditions that best suit infection and growth include moist, humid, and warm climates. Poor airflow, low sunlight, overcrowding, improper soil nutrient and irrigation management, and poor soil drainage can all contribute to the propagation of the disease. Management techniques include crop resistance, crop rotation, residue management, use of fungicides, and weed control. The purpose of disease management is to prevent the amount of secondary disease cycles as well as to protect leaf area from damage prior to grain formation. Corn grey leaf spot is an important disease of corn production in the United States, economically significant throughout the Midwest and Mid-Atlantic regions. However, it is also prevalent in Africa, Central America, China, Europe, India, Mexico, the Philippines, northern South America, and Southeast Asia. The teleomorph of Cercospora zeae-maydis is assumed to be Mycosphaerella sp.
Southern corn leaf blight (SCLB) is a fungal disease of maize caused by the plant pathogen Bipolaris maydis.
Gummy stem blight is a cucurbit-rot disease caused by the fungal plant pathogen Didymella bryoniae. Gummy stem blight can affect a host at any stage of growth in its development and affects all parts of the host including leaves, stems and fruits. Symptoms generally consist of circular dark tan lesions that blight the leaf, water soaked leaves, stem cankers, and gummy brown ooze that exudes from cankers, giving it the name gummy stem blight. Gummy stem blight reduces yields of edible cucurbits by devastating the vines and leaves and rotting the fruits. There are various methods to control gummy stem blight, including use of treated seed, crop rotation, using preventative fungicides, eradication of diseased material, and deep plowing previous debris.
Northern corn leaf blight (NCLB) or Turcicum leaf blight (TLB) is a foliar disease of corn (maize) caused by Exserohilum turcicum, the anamorph of the ascomycete Setosphaeria turcica. With its characteristic cigar-shaped lesions, this disease can cause significant yield loss in susceptible corn hybrids.
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.
Alternaria leaf spot or Alternaria leaf blight are a group of fungal diseases in plants, that have a variety of hosts. The diseases infects common garden plants, such as cabbage, and are caused by several closely related species of fungi. Some of these fungal species target specific plants, while others have been known to target plant families. One commercially relevant plant genus that can be affected by Alternaria Leaf Spot is Brassica, as the cosmetic issues caused by symptomatic lesions can lead to rejection of crops by distributors and buyers. When certain crops such as cauliflower and broccoli are infected, the heads deteriorate and there is a complete loss of marketability. Secondary soft-rotting organisms can infect stored cabbage that has been affected by Alternaria Leaf Spot by entering through symptomatic lesions. Alternaria Leaf Spot diseases that affect Brassica species are caused by the pathogens Alternaria brassicae and Alternaria brassicicola.
Colletotrichum fioriniae is a fungal plant pathogen and endophyte of fruits and foliage of many broadleaved plants worldwide. It causes diseases on agriculturally important crops, including anthracnose of strawberry, ripe rot of grapes, bitter rot of apple, anthracnose of peach, and anthracnose of blueberry. Its ecological role in the natural environment is less well understood, other than it is a common leaf endophyte of many temperate trees and shrubs and in some cases may function as an entomopathogen.
Bitter rot of apple is a fungal disease of apple fruit that is caused by several species in the Colletotrichum acutatum and Colletotrichum gloeosporioides species complexes. It is identified by sunken circular lesions with conical intrusions into the apple flesh that appear V-shaped when the apple is cut in half through the center of the lesion. It is one of the most devastating diseases of apple fruit in regions with warm wet weather.