''Alternaria dianthi'', sometimes known as carnation blight, is a fungal pathogen of the genus ''
Dianthus
''Dianthus'' () is a genus of about 340 species of flowering plants in the family Caryophyllaceae, native mainly to Europe and Asia, with a few species in north Africa and in southern Africa, and one species (''D. repens'') in arctic North Ameri ...
''.Bickerton, J. M., 1943: Alternaria blight of Carnations caused by ''Alternaria dianthi Stevens and Hall''. ''Nature''. ''Alternaria dianthi'' infections begin as small circular or ovular spots on leaves and stems, which can be red, purple, brown, yellow or gray.Seung-Hun Yu, Hi-Wan Kang, Hyang-Burm Lee, and Hong-Gi Kim. 1989. Occurrence of Alternaria dianthi on Carnation in Korea. ''Korean Journal of Mycology''. Chungnam National University, Taejon, Korea. Volume 17, Number 4, pp229-232.
This pathogen has been found in
carnation
''Dianthus caryophyllus'' (), commonly known as the carnation or clove pink, is a species of ''Dianthus''. It is likely native to the Mediterranean region but its exact range is unknown due to extensive cultivation for the last 2,000 years.Med ...
and other ''Dianthus'' cultures worldwide, including in India,Sharma, B. P. 1994. Diseases on carnation: their management. ''Indian Horticulture'', 38(4). the United States, New Zealand,Robinson, J. A. (1957). Control of Carnation diseases in New Zealand. ''New Zealand Plants and Gardens'', 2(5), 212-218. the
Canary Islands
The Canary Islands (; es, Canarias, ), also known informally as the Canaries, are a Spanish autonomous community and archipelago in the Atlantic Ocean, in Macaronesia. At their closest point to the African mainland, they are west of Morocc ...
,Rodríguez Rodríguez, Juan M. 1980. Ataques de ''Alternaria Dianthi Stevens y Hall'', en cultivos de clavel standard ttacks of ''Alternaria Dianthi Stevens and Hall'', in standard carnation cultivations ''Xoba: Revista de Agricultura'', Canary Islands, Spain. Volume 3, Number 4, pp190-194. and Egypt.Hilal, A. A., Kamel, B. K. M. 1990. Alternaria blight and rust diseases of carnation and their control. ''Agricultural Research Review'' Vol. 68 No. 3 pp. 543-554 Fourteen gene sequences of ''Alternaria dianthi'' have been published as of April 11, 2014Alternaria dianthi. Nucleotide database search. National Center for Biotechnology Information. Accessed 11 April 2014.
Symptoms
''Alternaria dianthi'' can infect healthy plants, and favors humid, warm environments. The multicolored circular spots can grow to infect entire plants, resulting in wilting or death. These spots tend to be smaller than one centimeter, but can be larger, especially around stems. The
cankers
A plant canker is a small area of dead tissue, which grows slowly, often over years. Some cankers are of only minor consequence, but others are ultimately lethal and therefore can have major economic implications for agriculture and horticultur ...
formed by ''A. dianthi'' spread through the
stomata
In botany, a stoma (from Greek ''στόμα'', "mouth", plural "stomata"), also called a stomate (plural "stomates"), is a pore found in the epidermis of leaves, stems, and other organs, that controls the rate of gas exchange. The pore is bor ...
of leaf cells, and generally lead to yellowing,
wilting
Wilting is the loss of rigidity of non-woody parts of plants. This occurs when the turgor pressure in non-lignified plant cells falls towards zero, as a result of diminished water in the cells. Wilting also serves to reduce water loss, as it m ...
, and death of the leaves of infected plants.Nelson, P. E. 1960. A recent review of carnation diseases. ''Florist's Review.''
Life cycle
''Alternaria dianthi'' reproduces asexually, forming row-like spores off of
hyphae
A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium.
Structure
A hypha consists of one or ...
.
Spores
In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, f ...
are formed on blisters on the host as well as within the
mycelium
Mycelium (plural mycelia) is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Fungal colonies composed of mycelium are found in and on soil and many other substrate (biology), substrates. A typical single ...
. The thin, globular spores are spread through water. Spore production and infection decreases over winter, and has been observed to be highest in rainy summer months.Chang, N. 1982. The Alternaria leaf-spot of Dianthus caryophyllus L. ''Journal of Plant Protection.''
The spores of ''A. dianthi'' germinate optimally around 24 °C (75 °F), and cannot
germinate
Germination is the process by which an organism grows from a seed or spore. The term is applied to the sprouting of a seedling from a seed of an angiosperm or gymnosperm, the growth of a sporeling from a spore, such as the spores of fungi, fer ...
below 4 °C (40 °F) or above 32 °C (90 °F). The fungus has been cultured on simple media such as
, and does not need ''Dianthus'' tissue to germinate. Spores come into contact with healthy leaf and stem tissue of ''Dianthus'' plants through wind, rain, and contact with infected tissue. The host plant must be wet or moist for spores to germinate. Moderate to high humidity is also a requirement, and one study found that spores would not germinate under 55% humidity. The life cycle takes about four days from germination to the production of new
conidia
A conidium ( ; ), sometimes termed an asexual chlamydospore or chlamydoconidium (), is an asexual, non-motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word for dust, ('). They are also called mitospores due to the ...
.
Spores produced by ''Alternaria'' species are black, and can persist on dead tissue, in soil, and on hard surfaces such as those found in greenhouses.Albajes, R. 1999. Integrated pest and disease management in greenhouse crops. Volume 14, pp 34-47.
No observations of pathogens of ''Alternaria dianthi'' have been published.
Impact
''Alternaria dianthi'' was first recorded in the scientific literature by F.L. Stevens and J.G. Hall in 1909, from florists in the United States.F. L. Stevens and J. G. Hall. 1909. Carnation alternariose. ''Botanical Gazette'', Vol. 47, No. 5, pp. 409-413. The fungus, along with other members of the genus ''
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 ...
'', is effectively controlled by the commercial fungicide
mancozeb
Mancozeb is a dithiocarbamate non-systemic agricultural fungicide with multi-site, protective action on contact. It is a combination of two other dithiocarbamates: maneb and zineb. The mixture controls many fungal diseases in a wide range of field ...
, as well as
dithiocarbamate
In organic chemistry, a dithiocarbamate is a functional group with the general formula and structure . It is the analog of a carbamate in which both oxygen atoms are replaced by sulfur atoms (when only 1 oxygen is replaced the result is thioca ...
s,
chlorothalonil
Chlorothalonil (2,4,5,6-tetrachloroisophthalonitrile) is an organic compound mainly used as a broad spectrum, nonsystemic fungicide, with other uses as a wood protectant, pesticide, acaricide, and to control mold, mildew, bacteria, algae. Chlor ...
, and
iprodione
Iprodione is a hydantoin fungicide and nematicide.
Application
Iprodione is used on crops affected by Botrytis bunch rot, Monilinia fructicola, Brown rot, Sclerotinia and other fungal diseases in plants. It is currently applied in a variety of cr ...
. Although ''A. dianthi'' has been found in wild and commercial varieties of ''Dianthus'' plants worldwide, no studies of the economic impacts or losses due to the disease have been published.