''Alternaria japonica'' is a

fungal A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from th ...

plant pathogen. It is a cause of black spot disease in cruciferous plants. It is not a major source of crop loss, but is considered dangerous for plants during the seedling stage.

Symptoms

''Alternaria japonica'' affects its hosts in all stages of life. Infection causes a black or grey sunken lesion with a characteristic yellow border. On the leaves of some plants, infection can cause dark, water-soaked spots. The lesions can be observed anywhere on the plant. In seedlings, fungal lesions on the stem are a cause of damping-off. Infected seeds appear black or grey.

Identification

The fungus can first be detected by visually observing symptoms on infected plants. When cultured on potato carrot agar, it will form a grey or brownish, cobweb-like mycelium. Upon microscopic inspection, ''A. japonica'' has septate, branched hyphae and appears colorless to greenish grey. Chlamydospores are multicellular with thick, rough walls. Conidia are solitary and beakless. Sequencing of the

ribosomal DNA Ribosomal DNA (rDNA) is a DNA sequence that codes for ribosomal RNA. These sequences regulate transcription initiation and amplification, and contain both transcribed and non-transcribed spacer segments. In the human genome there are 5 chromo ...

is commonly used for positive identification because the symptoms and microscopic appearance can resemble those of related species.

Hosts and distribution

Transmission of ''A. japonica'' occur from infected seeds and plant debris or conidia produced by the fungus in wet conditions. The major hosts of this organism are species in Brassicaceae such as cauliflower, turnip, and cabbage. Whether it can infect species outside of this family is unclear. This fungus is not thought to be a cause of disease in humans, unlike other members of ''

Alternaria ''Alternaria'' is a genus of Deuteromycetes fungi. All species are known as major plant pathogens. They are also common allergens in humans, growing indoors and causing hay fever or hypersensitivity reactions that sometimes lead to asthma. They ...

''. Occurrences of black spot caused by ''A. japonica'' have been reported worldwide.

Management

Once ''A. japonica'' has been established in an area, it can be difficult to eradicate because it can survive in a dormant state in the soil for years. Prevention of the spread of ''A. japonica'' by controlling the transportation of infected plant materials and seeds is crucial. Disinfection of seeds is an effective preventative measure. A variety of chemical fungicides can be used to protect seedlings.

Integrated pest management Integrated pest management (IPM), also known as integrated pest control (IPC) is a broad-based approach that integrates both chemical and non-chemical practices for economic control of pests. IPM aims to suppress pest populations below the econ ...

practices such as crop rotation with non-cruciferous plants can be beneficial for farmers dealing with this fungus.

References

{{Taxonbar, from=Q4736362 japonica Fungal plant pathogens and diseases Fungi described in 1941