Coffee wilt disease (tracheomycosis) is a common wilt that results in complete death of coffee trees it infects. This vascular disease is induced by the fungal pathogen known by its teleomorph Gibberella xylarioides (Fusarium xylarioides). [1] In 1927, coffee wilt disease (CWD) was first observed in the Central African Republic where it developed slowly and went on to cause two epidemics between the 1930s and the 1960s. [2] Coffee wilt disease was first seen in Coffea excelsa . [3]
Hosts of coffee wilt disease include Coffea arabica (Arabica coffee), Coffea canephora (Robusta coffee), Coffea liberica (Liberian coffee), and Coffea excelsa (Excelsa coffee) [4] Currently, the disease is limited to Eastern and Central Africa, however, studies have shown that most Coffea species are likely to be susceptible to the disease, which can potentially lead to more worldwide problems in the coffee industry. [4]
Due to the nature of coffee wilt disease, coffee plants often exhibit symptoms of disruption to vascular systems. [3] Internal symptoms are disturbances to conduction of water in the plant. External symptoms include loss of moisture on leaves, discoloration, leaf loss, dieback of the infected region, swelling of trunks, cracks in mature trees and lastly plant death. [2] Signs of coffee wilt disease include small blackish-brown perithecia caused by the sexual stage of the fungus, and cracks in the bark which cause an observable bluish-black stain on the wood. [2]
The fungal pathogen responsible for coffee wilt disease can exist on coffee trees as Gibberella xylarioides, the sexual or perfect stage, or as Fusarium xylarioides, the asexual or imperfect stage. [1] Coffee wilt disease is spread by wind-born ascospores during its sexual stage or splash-borne conidia, [1] where they land and can persist as a viable source of inoculum in the soil. [3] Infection occurs via penetration of wounds at the base of stems, mainly by the imperfect stage Fusarium xylarioides. Once the plant is infected, the fungus blocks the xylem system, which induces host responses that inevitably result in plant death. [2]
Coffee is a major cash crop, with over 2.5 million people directly depending on its production and trade as a livelihood. For some countries, coffee accounts for 50% of primary foreign exchange, valued around 300–400 million dollars annually. [6] Reduced coffee production causes decline of revenue for some African countries, [2] which can also increase food insecurity and overall regression at grassroot level. [6] In 1945 coffee wilt disease destroyed most of Central Africa Republic's Excelsa plantations, resulting in the complete collapse of the crop. [3] This disease causes a threat for coffee growers around the globe as the disease reduces the quantity and quality of the coffee. Not only does this disease put an economic strain on countries that use coffee as a cash crop, but it also can lead to the rise of coffee prices for consumers everywhere.
Once a coffee plant is infected by coffee wilt disease, death is inevitable, making prevention the most beneficial for coffee growers. [2] Diagnosis of coffee wilt disease can be made by observing a blue-black staining after bark scraping. [2] Additionally, regular root inspections are an effective measure to catch the disease in the early stages. Once disease is found, destruction of the coffee plant by cutting it at the ground level and burning it stops the spread of the infection to other plants. [5] Restriction of movement for coffee plant, coffee husks mulch and planting materials are also useful. [7] Relocation of coffee production or replanting of resistant C. canephora germplasm, assist with combating future spread. [3] Preventive measures for coffee wilt disease infection are to avoid wounding of trees for example when removing control weeds, fertilizing soil or by grazing of any animals. Additionally, maintaining plants’ health by using inorganic fertilizer, manure or mulch to conserve moisture are some ways to decrease the risk of coffee wilt disease. [7]
Fusarium wilt is a common vascular wilt fungal disease, exhibiting symptoms similar to Verticillium wilt. This disease has been investigated extensively since the early years of this century. The pathogen that causes Fusarium wilt is Fusarium oxysporum. The species is further divided into formae speciales based on host plant.
Panama disease is a plant disease that infects banana plants. It is a wilting disease caused by the fungus Fusarium oxysporum f. sp. cubense (Foc). The pathogen is resistant to fungicides and its control is limited to phytosanitary measures.
Phytophthora cinnamomi is a soil-borne water mould that produces an infection which causes a condition in plants variously called "root rot", "dieback", or, "ink disease". The plant pathogen is one of the world's most invasive species and is present in over 70 countries around the world.
Coffea canephora is a species of coffee that has its origins in central and western sub-Saharan Africa. It is a species of flowering plant in the family Rubiaceae. Though widely known as Coffea robusta, the plant is scientifically identified as Coffea canephora, which has two main varieties, robusta and nganda.
Ceratocystis fimbriata is a fungus and a plant pathogen, attacking such diverse plants as the sweet potato and the tapping panels of the Para rubber tree. It is a diverse species that attacks a wide variety of annual and perennial plants. There are several host-specialized strains, some of which, such as Ceratocystis platani that attacks plane trees, are now described as distinct species.
Mycosphaerella coffeicola is a sexually reproducing fungal plant pathogen. It is most commonly referred to as the asexual organism Cercospora coffeicola.
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.
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.
Gibberella xylarioides is a species of fungus in the family Nectriaceae. It is the causative agent of coffee wilt disease (CWD). The disease caused a severe problem in several countries in West and East Africa during the 1940s and 1950s. CWD was first seen in Coffea liberica.
Verticillium dahliae is a fungal plant pathogen. It causes verticillium wilt in many plant species, causing leaves to curl and discolor. It may cause death in some plants. Over 400 plant species are affected by Verticillium complex.
Ceratocystis paradoxa or Black Rot of Pineapple is a plant pathogen that is a fungus part of the phylum Ascomycota. It is characterized as the teleomorph or sexual reproduction stage of infection. This stage contains ascocarps, or sacs/fruiting bodies, which contain the sexually produced inoculating ascospores. These are the structures which are used primarily to survive long periods of time or overwinter to prepare for the next growing season of its host. Unfortunately, the sexual stage is not often seen in the natural field but instead the anamorph, or asexual stage is more commonly seen. This asexual stage name is Thielaviopsis paradoxa and is the common cause of Black rot or stem-end rot of its hosts.
Fusarium oxysporum f.sp. betae is a destructive fungal plant pathogen. It causes Fusarium yellows or fusarium wilt, characterized by yellowing and dwarfing.
Fusarium oxysporum f.sp. ciceris is a fungal plant pathogen that causes fusarium wilt of chickpea.
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.
Gibberella fujikuroi is a fungal plant pathogen. It causes bakanae disease in rice seedlings.
Phialophora gregata is a Deuteromycete fungus that is a plant pathogen which causes the disease commonly known as brown stem rot of soybean. P. gregata does not produce survival structures, but has the ability to overwinter as mycelium in decaying soybean residue.
Fusarium circinatum is a fungal plant pathogen that causes the serious disease pitch canker on pine trees and Douglas firs. The most common hosts of the pathogen include slash pine, loblolly pine, Monterey pine, Mexican weeping pine, and Douglas fir. Like other Fusarium species in the phylum Ascomycota, it is the asexual reproductive state of the fungus and has a teleomorph, Gibberella circinata.
Banana Xanthomonas Wilt (BXW), or banana bacterial wilt (BBW) or enset wilt is a bacterial disease caused by Xanthomonas campestris pv. musacearum. After being originally identified on a close relative of banana, Ensete ventricosum, in Ethiopia in the 1960s, BXW emanated in Uganda in 2001 affecting all types of banana cultivars. Since then BXW has been diagnosed in Central and East Africa including banana growing regions of: Rwanda, Democratic Republic of the Congo, Tanzania, Kenya, Burundi, and Uganda.
Colletotrichum coffeanum is a species of fungal plant pathogen affecting mainly the species Coffea arabica and occasionally other species of the genus Coffea. Upon infection, the pathogen can cause coffee berry disease (CBD) which is also known as Brown Blight when it occurs on younger fruits still green in color. The fungus was first reported in Kenya in 1922, and is found throughout most of Africa. C. coffeanum is only found in Africa, but other species of Colletotrichum can be found throughout the rest of the world.
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