Botrytis cinerea ("botrytis" from Ancient Greek botrys (βότρυς)
meaning "grapes" plus the
New Latin suffix -itis for disease) is a
necrotrophic fungus that affects many plant species, although its most
notable hosts may be wine grapes. In viticulture, it is commonly known
as botrytis bunch rot; in horticulture, it is usually called grey
mould or gray mold.
The fungus gives rise to two different kinds of infections on grapes.
The first, grey rot, is the result of consistently wet or humid
conditions, and typically results in the loss of the affected bunches.
The second, noble rot, occurs when drier conditions follow wetter, and
can result in distinctive sweet dessert wines, such as Sauternes or
the Aszú of Tokaji/Grasă de Cotnari. The species name Botrytis
cinerea is derived from the
Latin for "grapes like ashes"; although
poetic, the "grapes" refers to the bunching of the fungal spores on
their conidiophores, and "ashes" just refers to the greyish colour of
the spores en masse. The fungus is usually referred to by its anamorph
(asexual form) name, because the sexual phase is rarely observed. The
teleomorph (sexual form) is an ascomycete, Botryotinia fuckeliana,
also known as Botryotinia cinerea (see taxonomy box)
1 Hosts and symptoms
6 Human disease
7 Mycoviruses of Botrytis cinerea
9 See also
11 External links
Hosts and symptoms
The disease, gray mold, affects more than 200 dicotyledonous plant
species and a few monocotyledonous plants found in temperate and
subtropical regions. Serious economic losses can be a result of
this disease to both field and greenhouse grown crops. The causal
Botrytis cinerea can infect mature or senescent tissues, plants
prior to harvest, or seedlings. There is a wide variety of hosts
infected by this pathogen including protein crops, fiber crops, oil
crops, and horticultural crops. Horticultural crops include vegetables
(examples are chickpeas, lettuce, broccoli, and beans) and small fruit
crops (examples are grape, strawberry, and raspberry), these are most
severely affected and devastated by gray mold. Plant organs
affected include fruits, flowers, leaves, storage organs, and shoots.
Symptoms and signs:
Symptoms vary across plant organs and tissues.
Botrytis cinerea is a
soft rot that will have a collapsed and water soaked appearance on
soft fruit and leaves. Brown lesions may develop slowly on undeveloped
fruit. Twigs infected with gray mold will die back. Blossoms will
cause fruit drop and injury, such as ridging on developing and mature
fruit. Symptoms are visible at wound sites where the fungus begins
to rot the plant. Gray masses with a velvety appearance are conidia on
the plant tissues are a sign of plant pathogen. These conidia are
asexual spores that will continue to infect the plant and surrounding
hosts throughout the growing season making this a polycyclic disease.
Plants have evolved to produce localized lesions when a pathogen
attacks. An oxidative burst causes hypersensitive cell death called a
hypersensitive response (HR). This soft rot can trigger HR to
assist in colonization. Botrytis cinerea, as a necrotrophic pathogen,
exploits the dead tissue for its pathogenicity or its ability to cause
disease. Susceptible plants cannot use the HR to protect against
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Botrytis cinerea conidiophore
Botrytis cinerea growing on a plate with a ring of visible sclerotia
(dark brown balls)
Botrytis cinerea is characterized by abundant hyaline conida (asexual
spores) borne on grey, branching tree-like conidiophores. The fungus
also produces highly resistant sclerotia as survival structures in
older cultures. It overwinters as sclerotia or intact mycelia, both of
which germinate in spring to produce conidiophores. The conidia,
dispersed by wind and by rain-water, cause new infections.
Botrytis cinerea strains show considerable genetic
Gliocladium roseum is a fungal parasite of Botrytis cinerea.
Gray mold favors moist, humid, and warm environmental conditions
between 18.3-23-9℃ (65-75℉). Temperature, relative humidity,
and wetness duration produce a conducive environment that is favorable
for inoculation of mycelium or conidia. Controlled environments,
such as crop production greenhouses, provide the moisture and high
temperatures that favor the spreading and development of the pathogen
Standing water on plant leaf surfaces provides a place for spores to
germinate. Humid conditions can result from improper irrigation
practice, plants placed too close together, or the structure of the
greenhouse not allowing for efficient ventilation and air flow.
Ventilation at night significantly reduces the incidence of gray
Melanized sclerotium allows
Botrytis cinerea to survive for years in
the soil. Sclerotia and the asexual conidia spores contribute to the
widespread infection of the pathogen.
A low pH is preferred by the gray mold to perform well. Botrytis
cinerea can acidify its environment by secreting organic acids, like
oxalic acid. By acidifying its surroundings, cell wall degrading
enzymes (CWDEs) are enhanced, plant-protection enzymes are inhibited,
stomatal closure is deregulated, and pH signaling is mediated to
facilitate its pathogenesis.
Main article: Noble rot
In the Botrytis infection known as "noble rot" (pourriture noble in
French, or Edelfäule in German), the fungus removes water from the
grapes, leaving behind a higher percent of solids, such as sugars,
fruit acids and minerals. This results in a more intense, concentrated
final product. The wine is often said to have an aroma of honeysuckle
and a bitter finish on the palate.
A distinct fermentation process initially caused by nature, the
combination of geology, climate and specific weather led to the
particular balance of beneficial fungus while leaving enough of the
grape intact for harvesting. The Chateau d'Yquem is the only Premier
Cru Supérieur, largely due to the vineyard's susceptibility to noble
Botrytis complicates winemaking by making fermentation more complex.
Botrytis produces an anti-fungal that kills yeast and often results in
fermentation stopping before the wine has accumulated sufficient
levels of alcohol. Makers of fine German dessert
wines have been known to take fermenting tubs of wine into their homes
to nurture the yeast through the night to assure that the alcohol
level reaches legal minimums for the product to be called
Botrytis cinerea on Riesling grapes.
Botrytis bunch rot is another condition of grapes caused by Botrytis
cinerea that causes great losses for the wine industry. It is always
present on the fruitset, however, it requires a wound to start a bunch
rot infection. Wounds can come from insects, wind, accidental damage,
etc. To control botrytis bunch rot there are a number of fungicides
available on the market. Generally, these should be applied at bloom,
bunch closure and veraison (the most important being the bloom
application). Some winemakers are known to use the German method of
fermentation and prefer having a 5% bunch rot rate in their grapes and
will usually hold the grapes on the vine a week longer than normal.
Botrytis cinerea affects many other plants. It is economically
important on soft fruits such as strawberries and bulb crops.
Unlike wine grapes, the affected strawberries are not edible and are
discarded. To minimize infection in strawberry fields, good
ventilation around the berries is important to prevent moisture being
trapped among leaves and berries. A number of bacteria have been
proven to act as natural antagonists to B. cinerea in controlled
In greenhouse horticulture,
Botrytis cinerea is well known as a cause
of considerable damage in tomatoes.
The infection also affects rhubarb, snowdrops, white meadowfoam,
Douglas-fir  and cannabis. Potassium
bicarbonate-based fungicide has been proven to cure and prevent
powdery mildew, blackspot, downy mildew, blights, molds and other
plant diseases, such as Botrytis cinerea.
Botrytis cinerea mold on grapes may cause "winegrower's lung", a rare
form of hypersensitivity pneumonitis (a respiratory allergic reaction
in predisposed individuals).
Mycoviruses of Botrytis cinerea
Botrytis cinerea not only infects plants, it also hosts several
mycoviruses itself (see Table).
Mycoviruses of Botrytis cinerea.
A range of phenotypic alterations due to the mycoviral infection have
been observed from symptomless to mild impact, or more severe
phenotypic changes including reduction in pathogenicity,
growth/suppression of mycelia, sporulation and sclerotia production,
formation of abnormal colony sectors (Wu et al., 2010) and
Botrytis cinerea can be managed through cultural, chemical, and
There are no resistant species to the gray mold rot. Gray mold can be
culturally controlled by monitoring the amount and timing of
fertilizer applications to reduce the amount of fruit rot. Excessive
application of nitrogen will increase the incidence of disease while
not improving yields.
Planting cultivars that don’t have an upright or dense growth habit
can reduce disease as these limit airflow and are favorable for the
pathogen. Spacing of plants so they are not touching will increase
airflow allowing the area to dry out and reduce the spread of disease.
Pruning or purposeful removal of diseased, dead, or overgrown limbs on
a regular schedule can also help to improve air movement.
Sanitation by removing dead or dying plant tissue in the fall will
decrease inoculum levels as there is no debris for the sclerotium or
mycelia to overwinter. Removing debris in the spring will remove
inoculum from the site. Disposal of berries during harvest that have
signs and symptoms of gray mold will reduce inoculum for the following
Biochar, a form of charcoal, can be applied as a soil amendment to
strawberry plants to reduce the severity of the fungal disease by
stimulating defense pathways within the plant.
Gray mold can be chemically controlled with well-timed fungicide
applications starting during the first bloom. Timing can reduce the
chance of resistance and will save on costs.
Biological controls or microbial antagonists used for disease
suppression, have been successfully used in Europe and Brazil in the
form of fungi-like Trichoderma harzianium Rifai and Gliocladium roseum
Bainier. Trichoderma species especially, have been shown to
control gray mold.
^ βότρυς. Liddell, Henry George; Scott, Robert; A
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Wikimedia Commons has media related to Botrytis cinerea.
Genome information for Botrytis cinerea
Genome analysis of Botrytis cinerea
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Annual growth cycle of grapevines
Grape Genome Program
Diurnal temperature variation
Regional climate levels
Frost damage prevention
Green harvest (Vendange verte)
Integrated pest management
Botrytis bunch rot
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