Recent from talks
Black sigatoka
Knowledge base stats:
Talk channels stats:
Members stats:
Black sigatoka
Black sigatoka is a leaf-spot disease of banana plants caused by the ascomycete fungus Mycosphaerella fijiensis (Morelet), also known as black leaf streak. It was discovered in 1963 and named for its similarities with yellow Sigatoka, which is caused by Mycosphaerella musicola (Mulder), which was itself named after the Sigatoka Valley in Fiji. In the same valley an outbreak of this disease reached epidemic proportions from 1912 to 1923.
According to new terminology, the Sigatoka disease complex is a cluster of three closely related fungi: Black Sigatoka and its congeners Yellow Sigatoka (Ps. musae) and eumusae leaf spot (Ps. eumusae).
Plants with leaves damaged by the disease may have up to 50% lower yield of fruit, and control can take up to 50 sprays a year.
M. fijiensis reproduces both sexually and asexually, and both conidia and ascospores are important in its dispersal. The conidia are mainly waterborne for short distances, while ascospores are carried by wind to more remote places (the distances being limited by their susceptibility to ultraviolet light). Over 60 distinct strains with different pathogenic potentials have been isolated. To better understand the mechanisms of its variability, projects to understand the genetic diversity of M. fijiensis have been initiated.
When spores of M. fijiensis are deposited on a susceptible banana leaf, they germinate within three hours if the humidity is high or a film of water is present. The optimal temperature for germination of the conidia is 27 °C (81 °F). The germ tube grows epiphytically over the epidermis for two to three days before penetrating the leaf through a stoma. Once inside the leaf, the invasive hypha forms a vesicle and fine hyphae grow through the mesophyll layers into an air chamber. More hyphae then grow into the palisade tissue and continue on into other air chambers, eventually emerging through stomata in the streak that has developed. Further epiphytic growth occurs before the re-entry of the hypha into the leaf through another stoma repeats the process. The optimal conditions for M. fijiensis as compared with M. musicola are a higher temperatures and higher relative humidity, and the whole disease cycle is much faster in M. fijiensis.
Black Sigatoka is also known as black leaf streak, causing streaks that run parallel to the secondary veins of banana leaves. It affects banana trees specifically in tropical climates; including Asia, East and West Africa, Trinidad, Grenada, many Pacific islands, Central America and South America. Tropical weather is the preferred climate for banana cultivation, but it is also the environment where the pathogen thrives: hot and humid, with plenty of rainfall to aid in dispersal. The optimal environment of the pathogen is similar to that of the banana tree. The fungus infects mature banana leaves and will continue to cause infection without proper control.
In the early stages of the infection of the plant, the lesions have a rusty brown appearance and appear to be faint, paint-like specks on the leaves. They become more visible on the undersides of the banana leaf as the lesions and leaves grow. The spots on the undersides of leaf are the fungus itself. The sign of the pathogen consists of the ascocarp which holds the ascospores used for dissemination to infect healthy new plants when the environment is conducive. The pathogen then survives on dead plant tissue as mycelium. The dimensions of the lesions are characteristically 20 by 2 millimetres (3⁄4 in × 1⁄8 in) with a well defined wall surrounding it. After further development, they become darker, sink into the leaf, and turn into depressions. The depressions themselves and the chlorosis surrounding them are the visible symptoms of the plant pathogen. They eventually will merge, causing the rapid decline of plant morphological and physiological function. Leaves with large infectious lesions will start to degrade and collapse because the leaf spots interrupt the plant's ability to perform photosynthesis, leading to the ultimate death of the plant.
The yellow leaf streak pathogen is in the same genus as that of black leaf streak. Yellow leaf streak shows smaller, yellow-green lesions that appear on top of the leaves.
Hub AI
Black sigatoka AI simulator
(@Black sigatoka_simulator)
Black sigatoka
Black sigatoka is a leaf-spot disease of banana plants caused by the ascomycete fungus Mycosphaerella fijiensis (Morelet), also known as black leaf streak. It was discovered in 1963 and named for its similarities with yellow Sigatoka, which is caused by Mycosphaerella musicola (Mulder), which was itself named after the Sigatoka Valley in Fiji. In the same valley an outbreak of this disease reached epidemic proportions from 1912 to 1923.
According to new terminology, the Sigatoka disease complex is a cluster of three closely related fungi: Black Sigatoka and its congeners Yellow Sigatoka (Ps. musae) and eumusae leaf spot (Ps. eumusae).
Plants with leaves damaged by the disease may have up to 50% lower yield of fruit, and control can take up to 50 sprays a year.
M. fijiensis reproduces both sexually and asexually, and both conidia and ascospores are important in its dispersal. The conidia are mainly waterborne for short distances, while ascospores are carried by wind to more remote places (the distances being limited by their susceptibility to ultraviolet light). Over 60 distinct strains with different pathogenic potentials have been isolated. To better understand the mechanisms of its variability, projects to understand the genetic diversity of M. fijiensis have been initiated.
When spores of M. fijiensis are deposited on a susceptible banana leaf, they germinate within three hours if the humidity is high or a film of water is present. The optimal temperature for germination of the conidia is 27 °C (81 °F). The germ tube grows epiphytically over the epidermis for two to three days before penetrating the leaf through a stoma. Once inside the leaf, the invasive hypha forms a vesicle and fine hyphae grow through the mesophyll layers into an air chamber. More hyphae then grow into the palisade tissue and continue on into other air chambers, eventually emerging through stomata in the streak that has developed. Further epiphytic growth occurs before the re-entry of the hypha into the leaf through another stoma repeats the process. The optimal conditions for M. fijiensis as compared with M. musicola are a higher temperatures and higher relative humidity, and the whole disease cycle is much faster in M. fijiensis.
Black Sigatoka is also known as black leaf streak, causing streaks that run parallel to the secondary veins of banana leaves. It affects banana trees specifically in tropical climates; including Asia, East and West Africa, Trinidad, Grenada, many Pacific islands, Central America and South America. Tropical weather is the preferred climate for banana cultivation, but it is also the environment where the pathogen thrives: hot and humid, with plenty of rainfall to aid in dispersal. The optimal environment of the pathogen is similar to that of the banana tree. The fungus infects mature banana leaves and will continue to cause infection without proper control.
In the early stages of the infection of the plant, the lesions have a rusty brown appearance and appear to be faint, paint-like specks on the leaves. They become more visible on the undersides of the banana leaf as the lesions and leaves grow. The spots on the undersides of leaf are the fungus itself. The sign of the pathogen consists of the ascocarp which holds the ascospores used for dissemination to infect healthy new plants when the environment is conducive. The pathogen then survives on dead plant tissue as mycelium. The dimensions of the lesions are characteristically 20 by 2 millimetres (3⁄4 in × 1⁄8 in) with a well defined wall surrounding it. After further development, they become darker, sink into the leaf, and turn into depressions. The depressions themselves and the chlorosis surrounding them are the visible symptoms of the plant pathogen. They eventually will merge, causing the rapid decline of plant morphological and physiological function. Leaves with large infectious lesions will start to degrade and collapse because the leaf spots interrupt the plant's ability to perform photosynthesis, leading to the ultimate death of the plant.
The yellow leaf streak pathogen is in the same genus as that of black leaf streak. Yellow leaf streak shows smaller, yellow-green lesions that appear on top of the leaves.
Recent media