Verticillium | |
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Verticillium theobromae culture | |
Scientific classification ![]() | |
Domain: | Eukaryota |
Kingdom: | Fungi |
Division: | Ascomycota |
Class: | Sordariomycetes |
Order: | Glomerellales |
Family: | Plectosphaerellaceae |
Genus: | Verticillium Nees (1816) |
Type species | |
Verticillium dahliae Kleb. (1913) [1] | |
Species | |
See text |
Verticillium is a genus of fungi in the division Ascomycota, and are an anamorphic form of the family Plectosphaerellaceae. The genus used to include diverse groups comprising saprobes and parasites of higher plants, insects, nematodes, mollusc eggs, and other fungi, thus the genus used to have a wide-ranging group of taxa characterised by simple but ill-defined characters. The genus, currently thought to contain 51 species, [2] may be broadly divided into three ecologically based groups - mycopathogens, entomopathogens, [3] and plant pathogens and related saprotrophs. [4] However, the genus has undergone recent revision into which most entomopathogenic and mycopathogenic isolates fall into a new group called Lecanicillium .
At least five species are known to cause a wilt disease in plants called verticillium wilt: V. dahliae, V. longisporum, V. albo-atrum, V. nubilum, and V. tricorpus. [4] A sixth species, V. theobromae, causes fruit or crown rot, a non-wiliting disease.
Verticillium wilt is a disease that can affect over 400 different eudicot plants, many of which are economically important worldwide. Several characteristics of Verticillium make it difficult to manage: prolonged survival in soils without the presence of a host, inaccessibility during infection, a wide host range, and limited resistance in host germplasm. However, all monocots, gymnosperms and ferns are immune.
The fungus survives in the soil principally in the form of microsclerotia, invades the plant through the root system, colonizes the vasculature, and eventually leads to plant death. The main mechanisms of its pathogenesis are xylem vessel blockage and toxin production. [5] [6] When the fungus propagates within a host plant, the mycelium blocks the xylem vessels, impairing the transport of water and nutrients in the host. The forces of transpiration and respiration in leaves combined with blocked xylem transport cause water imbalances in leaves that result in leaf yellowing and wilting, contributing to plant death. In addition, Verticillium produces mycotoxins within the plant that can cause necrosis in leaves and impair metabolism in the plant body. In some systems, toxin production has been shown to be the main cause of plant wilting. [6]
First identified from potatoes in Germany in 1870, this disease affects a variety of cultivated plants and can persist as a saprotrophic soil organism for more than 15 years. Identification can be made by looking for one-celled conidia, hyaline round to ellipsoid which are formed at the tips of whorled branches. They are easily separated from the tips. When infecting ornamental trees such as maples, elms, aspen, ash, beech, catalpa, oak, and others, the first symptoms are midsummer wilting on one side of a tree or branch. The sapwood has greenish or brownish streaks, and the infection can take a few years to progress to the rest of the tree or move rapidly. The fungi universally move up the xylem vessels. In fruit trees, the infection is known as black heart, and is common in apricots and sometimes affects almond, peach, plum, and avocado trees. This fungus affects herbaceous ornamentals such as chrysanthemums, mints, Lychnis spp. It infects many agriculturally important crops like vegetables such as tomatoes, eggplants, okra, broccoli, cauliflower and rhubarb; food related crops like rapeseed and hops; and fiber crops like cotton.
Plant pathology is the scientific study of diseases in plants caused by pathogens and environmental conditions. Organisms that cause infectious disease include fungi, oomycetes, bacteria, viruses, viroids, virus-like organisms, phytoplasmas, protozoa, nematodes and parasitic plants. Not included are ectoparasites like insects, mites, vertebrate, or other pests that affect plant health by eating plant tissues and causing injury that may admit plant pathogens. Plant pathology also involves the study of pathogen identification, disease etiology, disease cycles, economic impact, plant disease epidemiology, plant disease resistance, how plant diseases affect humans and animals, pathosystem genetics, and management of plant diseases.
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.
A leaf spot is a limited, discoloured, diseased area of a leaf that is caused by fungal, bacterial or viral plant diseases, or by injuries from nematodes, insects, environmental factors, toxicity or herbicides. These discoloured spots or lesions often have a centre of necrosis. Symptoms can overlap across causal agents, however differing signs and symptoms of certain pathogens can lead to the diagnosis of the type of leaf spot disease. Prolonged wet and humid conditions promote leaf spot disease and most pathogens are spread by wind, splashing rain or irrigation that carry the disease to other leaves.
Dickeya dadantii is a gram-negative bacillus that belongs to the family Pectobacteriaceae. It was formerly known as Erwinia chrysanthemi but was reassigned as Dickeya dadantii in 2005. Members of this family are facultative anaerobes, able to ferment sugars to lactic acid, have nitrate reductase, but lack oxidases. Even though many clinical pathogens are part of the order Enterobacterales, most members of this family are plant pathogens. D. dadantii is a motile, nonsporing, straight rod-shaped cell with rounded ends, much like the other members of the genus, Dickeya. Cells range in size from 0.8 to 3.2 μm by 0.5 to 0.8 μm and are surrounded by numerous flagella (peritrichous).
Verticillium wilt is a wilt disease affecting over 350 species of eudicot plants. It is caused by six species of Verticillium fungi: V. dahliae, V. albo-atrum, V. longisporum, V. nubilum, V. theobromae and V. tricorpus. Many economically important plants are susceptible including cotton, tomatoes, potatoes, oilseed rape, eggplants, peppers and ornamentals, as well as others in natural vegetation communities. Many eudicot species and cultivars are resistant to the disease and all monocots, gymnosperms and ferns are immune.
Brenneria salicis is a Gram-negative bacterium that is pathogenic on plants.
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.
Nectria cinnabarina, also known as coral spot, is a plant pathogen that causes cankers on broadleaf trees. This disease is polycyclic and infects trees in the cool temperate regions of the Northern Hemisphere. N. cinnabarina is typically saprophytic, but will act as a weak parasite if presented with an opportunity via wounds in the tree or other stressors that weaken the tree's defense to the disease. A study published in 2011 showed that this complex consists of at least 4 distinct species. There are only a few ways to manage this disease with techniques such as sanitation and pruning away branches that have the cankers. N. cinnabarina is not as significant a problem as other Nectria spp., some of which are the most important pathogens to infect hardwood trees.
Lasiodiplodia theobromae is a plant pathogen with a very wide host range. It causes rotting and dieback in most species it infects. It is a common post harvest fungus disease of citrus known as stem-end rot. It is a cause of bot canker of grapevine. It also infects Biancaea sappan, a species of flowering tree also known as Sappanwood.
Verticillium albo-atrum is a plant pathogen with many hosts.
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.
Verticillium longisporum, also known as Verticillium Wilt, is a fungal plant pathogen that commonly infects canola. V. longisporum can attack other brassica plants as well as woody ornamentals. A main symptom of the infected plant is wilting. In America, V. longsiporum primarily effects eudicot plants. This pathogen can be very devastating and hard to eradicate, responding only to expensive fumigation or fungal resistant plants.
A wilt disease is any number of diseases that affect the vascular system of plants. Attacks by fungi, bacteria, and nematodes can cause rapid killing of plants, large tree branches or even entire trees.
Lecanicillium lecanii is now an approved name of an entomopathogenic fungus species, that was previously widely known as Verticillium lecanii (Zimmerman) Viegas), but is now understood to be an anamorphic form in the Cordyceps group of genera in the Clavicipitaceae. Isolates formerly classified as V. lecanii could be L. attenuatum, L. lecanii, L. longisporum, L. muscarium or L. nodulosum. For example, several recent papers, such as Kouvelis et al. who carried out mitochondrial DNA studies, refer to the name L. muscarium.
Lecanicillium is a genus of fungi in the order Hypocreales and is described as anamorphic Cordycipitaceae; 21 species are currently described. Some of these entomopathogenic fungus species were previously widely known as Verticillium lecanii (Zimmerman) Viegas. This genus was first named and introduced by Rasoul Zare (IRIPP) and Walter Gams (CBS).
Verticillium dry bubble, recently named Lecanicillium fungicola, is a mycoparasite that attacks white button mushrooms, among other hosts, during its generative period. L. fungicola infects the casing layer on the cap structure of several edible mushrooms. This fungal pathogen does not typically infect wild mushrooms, but more commonly cultivated mushrooms are infected such as A. bisporus, which are typically grown in large quantities. Severity of disease depends on several factors, including timing of infection and environmental conditions. Dry bubble follows the typical verticillium life cycle, although insect vectors play a large role in the spread of this disease. Control for L. fungicola is limited, and strict measures must be taken to prevent the spread of infection. L. fungicola is a devastating pathogen in the mushroom industry and causes significant losses in the commercial production of its main host A. bisporus. Annual costs for mushroom growers are estimated at 2–4% of total revenue.
Verticillium nonalfalfae is a soilborne fungus in the order Hypocreales. It causes verticillium wilt in some plant species, particularly Ailanthus altissima. The fungus produces a resting mycelium characterized by brown-pigmented hyphae. It is most closely related to V. dahliae and V. alfalfae.
Verticillium alfalfae is a fungus. It causes verticillium wilt in some plant species, particularly alfalfa. It produces yellow-pigmented hyphae and microsclerotia, while producing resting mycelium. It is most closely related to V. albo-atrum and V. nonalfalfae.
Verticillium klebahnii is a fungus often pathogenically inhabiting lettuce. It causes verticillium wilt in some plant species. It produces yellow-pigmented hyphae and microsclerotia, while producing abundant chlamydospores and resting mycelium. It is most closely related to V. tricorpus and V. isaacii.
Verticillium isaacii is a fungus inhabiting artichoke, spinach and lettuce, without necessarily being pathogenic. It causes verticillium wilt in some plant species. It produces yellow-pigmented hyphae and microsclerotia, while producing abundant chlamydospores and resting mycelium. It is most closely related to V. tricorpus and V. klebahnii.