Colletotrichum gloeosporioides is a complex of phytopathogenic filamentous Ascomycota fungi species of the Glomerellaceae family. They are responsible for the disease of the fruit known as anthracnose. This disease can affect any part of the plant and, in crops, is responsible for large economic losses worldwide.
Name Colletotrichum gloeosporioides designates the anamorphic (asexual reproduction) phase of the fungus, while the sexual or teleomorphic phase is called Glomerella cingulata. The anamorphic phase reproduces by means of conidiospores, whereas Glomerella cingulata it does so by means of haploid ascospores.
Anthracnose attacks numerous plants, both wild and cultivated, causing spots or cankers on the stem and branches, spots on leaves and flowers, as well as fruit rot. Control of anthracnose can be done through crop management or through the addition of agrochemicals.
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Colletotrichum gloeosporioides it is characterized by having reproductive structures or spores called conidia, which have a straight, cylindrical shape, with obtuse apices and no septa; These conidia range in size from 9 to 24 µm long by 3-6 µm wide, and are formed in cylindrical phialides with a hyaline appearance..
The conidia are arranged in setosus acérvules that present a variable shape that goes from rounded to elongated or irregular, with a diameter that does not exceed 500 µm. The mushrooms, on the other hand, are brown, with a length that rarely exceeds 200 µm.
Colletotrichum gloeosporioides It has septate hyphae and produces appressoria with a claviform, triangular or irregular appearance, sometimes lobulated, with dark brown pigments and whose dimensions range from 4 to 12 μm in length..
An important characteristic of the fungus is that it has the capacity for quiescence, that is, it can remain inactive in the tissues of infected plants, plant debris and also in seeds, which allows it to survive for a long time until the optimal conditions are presented for its growth.
Colletotrichum gloeosporioides, Like other species of the genus, it has a complex life cycle with different phases or patterns of life style that are regulated by genetic factors and biochemical interactions between the fungus and its host. These lifestyles are necrotrophic, hemibiotrophic, quiescent, and endophytic..
In the necrotrophic lifestyle the fungus secretes lytic enzymes to degrade plant components or toxins to kill its tissues. The pathogen completes its life cycle on this dead tissue.
Some species of fungi only present this lifestyle, but in other species, such as C. gloeosporioides, constitutes a phase of their life cycle.
Fungi of the genus Colletotrichum they lack a biotrophic lifestyle. The biotrophs remain inside the plant tissues, absorbing their nutrients but without killing the host. The lifestyle of this genus is hemibiotrophic, in which they act as biotrophs in their early life stages, but then become necrotrophic..
These species initially colonize the epidermal cells of the plant, without actually killing them. Subsequently, the hyphae invade and kill adjacent cells in the necrotrophic phase..
Quiescence, also known as latency, is a phase or period in the life cycle of fungi, in which the organism is dormant on the interior or surface of the host before entering the active phase.
In the case of fungi of the genus Colletotrichum, these remain quiescent within the host's tissues before disease symptoms develop. In the case of fruits, these symptoms can occur during harvest, storage, transport, or even after sale..
Endophytic fungi are those that inhabit the interior of the plant as symbionts without causing apparent damage. Even most of these fungi establish mutualistic relationships with their hosts, in which the fungus gains protection from desiccation and access to plant nutrients..
The host obtains in counterpart resistance to attack by pathogens and herbivores, as well as greater tolerance to abiotic stress. Most species of Colletotrichum that have been reported as endophytic belong to a complex of species of C. gloeosporioides.
Colletotrichum gloeosporioides it is an opportunistic pathogen that attacks injured plant tissues and is also an invader of dead material; in apparently healthy tissues of many plants it can be found both on the surface and in the interior of the plant. It can also be found in a quiescent state..
The penetration and colonization of the host by Colletotrichum gloeosporioides it can happen in two ways. In the first, the conidia germinate and form oppressors that facilitate entry through the cuticle and host cells; in the second case, penetration occurs through the stomata through vesicles and hyphae of infection.
After infection, the fungus may initiate a subcuticular intramural hemibiotrophic or necrotrophic phase. The first is asymptomatic and in it the penetrating structures invade the cells of the epidermis of the host and the primary hyphae produce infection vesicles inside the cells of the epidermis and the mesophyll..
This phase is followed by the necrotrophic phase, in which secondary hyphae will invade the interior of infected cells and neighboring cells, secreting enzymes that kill them..
In the intramural subcuticular necrotrophic phase, on the other hand, the fungus will grow under the cuticle within the periclinal and anti-canal walls of the epidermal cells, without penetrating the protoplasm. Subsequently, the hyphae initiate the destruction of the colonized tissues.
Reproduction can occur in the infected plant or in plant remains and can be asexual or sexual, but it is fundamentally associated with infection, especially in the asexual (anamorphic) form. The formation of the acervuli is associated with the appearance of the symptoms of the disease.
Sexual reproduction is little known in this species, but in culture it has shown that perithecia (sexual fruiting bodies) form rapidly. These contain the asci that will produce the haploid ascospores.
When environmental conditions are favorable for the formation of perithecia, the release of ascospores is induced, which infect the neighboring tissues of the plant..
Ascospores germinate and infect plant tissues. The hyphae in these areas will develop acervules, which will produce masses of conidia in the conidiophores..
Conidia are spread by rain splashes or by the breeze to healthy leaves, young fruits or buds. Environmental conditions, as well as the senescence of the host, can induce a new development of the sexual stage to restart the life cycle..
Chemical control of Colletotrichum gloeosporioides It is carried out by means of fungicides that can be applied in spray, both in the pre and post-harvest period. The use of this type of control, applied in orchards at intervals of 2 to 4 weeks, has been shown to be effective in controlling the pathogen..
Postharvest control can also use immersion in fungicide, in addition to spray. This method is the most used for postharvest control of anthracnose in fruits and crops that are shipped by sea..
Among the fungicides used to control Colletotrichum gloeosporioides they include copper hydroxide and copper sulfate, as well as prochloraz and azoxystrobin. The latter can inhibit or suppress the mycelial growth of the fungus. The alternate use of funchloraz and amistar has also been effective..
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