3. History and introduction:
Penicillium digitatum is a species within
the Ascomycota division of Fungi.
The genus name Penicillium comes from the word
"penicillus" which means brush, referring to the
branching appearance of the asexual reproductive
structures found within this genus
P. digitatum was first noted as Aspergillus
digitatus by Christiaan Hendrik Persoon in 1794
5. symptoms:
P. digitatum causes a destructive fruit rot of citrus.
Soft water-soaked area on the peel, followed by the
development of a circular colony of white mould, up to
4 cm diam. after 24-36 hours at 24°C.
Green asexual spores (conidia) form at the centre of
the colony, surrounded by a broad band of white
mycelium.
The lesion spreads more rapidly than those caused by
P. italicum.
The fruit rapidly spoils and collapses (Brown and
Eckert, 1988; Snowdon, 1990).
6.
7. Epidemiology:
Penicillium digitatum is a mesophilic fungus,
growing from 6–7 °C to a maximum of 37 °C , with an
optimal growth temperature at 24 °C .
With respect to water activity P. digitatum has a
relatively low tolerance for osmotic stress.
Germination does not occur at a water activity of 0.87.
In terms of chemicals that influence fungal growth,
the minimum growth inhibitory concentration
of sorbic acid is 0.02–0.025% at a pH of 4.7 and 0.06–
0.08% at a pH of 5.5.
8. Thiamine on the other hand, has been observed to
accelerate fungal growth with the effect being co-
metabolically enhanced in the presence
of tyrosine, casein or zinc metal.
In terms of carbon nutrition, maltose, oxalic acid
and tartaric acid support little, if any, growth.
However, glucose, fructose, sucrose, galactose citric
acid and malic acid all maintain fungal growth
12. Ecology:
Penicillium digitatum is found in the soil of areas
cultivating citrus fruit.
In nature, it is often found alongside the fruits it infects,
making species within the genus Citrus its main ecosystem.
It is only within these species that P. digitatum can
complete its life cycle as a necrotroph. However, P.
digitatum has also been isolated from other food sources.
These include hazelnuts, pistachio nuts, kola nuts,
black olives, rice, maize and meats.
Low levels have also been noted in Southeast
Asian peanuts, soybeans and sorghum.
14. Blue mould of citrus:
Etiology
Class: Eurotiomycetes
Order: Eurotiales
Family: Trichocomaceae
Genus: Penicillium
Species: P. italicum
Binomial name: Penicillium
italicum
15. History and introduction:
Penicillium italicum, the cause of citrus blue mold was
described by Wehmer in 1894
Penicillium italicum is a species within
the Ascomycota division of Fungi
Penicillium italicum is the first phytopathogenic
penicillium species whose complete genome has been
entirely sequence .
16. Symptoms:
P. italicum causes a destructive fruit rot of citrus.
Soft water-soaked area on the peel, followed by
development of a circular colony of white mould.
Bluish asexual spores (conidia) form at the centre of the
colony, surrounded by a broad band of white mycelium.
The lesions spread more slowly than those caused by P.
digitatum.
A halo of watersoaked, faded tissue surrounds the lesion.
The fruit rapidly spoils and collapses (Brown and Eckert,
1988, Brown, 1994).
17.
18. Host plants of blue mould:
Allium cepa (onion)
Allium sativum (garlic)
Citrus
Citrus aurantium (sour orange)
Citrus bergamia (bergamot)
Citrus limon (lemon)
Citrus maxima (pummelo)
Citrus nobilis (tangor)
Citrus sinensis (navel orange)
Citrus x paradisi (grapefruit)
Cucumis sativus (cucumber)
Dioscorea (yam)
19. Management:
green and blue mould initially relies on the proper
handling of fruit before, during and after harvesting.
Spores can be reduced by removing fallen fruit.
Risk of injury can be decreased in a variety of ways
including, storing fruit in high humidity/ low
temperature conditions, and harvesting before
irrigation or rainfall in order to minimize fruit
susceptibility to peel damage.
Degreening practices can also be conducted at
humidities above 92% in order to heal injuries
20. Control:
Chemical control :
in the form of fungicides is also commonly used. such as
imazalil
thaibendazole
biphenyl
All of which suppress the reproductive cycle.
Post-harvest chemical treatment usually consists of
washes conducted at 40–50 °C (104–122 °F),
containing detergents, weak alkalines and fungicides.
Californian packinghouses typically use a fungicide
cocktail containing sodium o-phenylphenate , imazalil and
thiabendazole.
21. In Australia, guazatine is commonly used although
this treatment is restricted to the domestic market.
In terms of the export market, Generally recognized as
safe (GRAS) substances are currently being explored as
alternatives.
GRAS substances such as sodium bicarbonate, sodium
carbonate and ethanol, have displayed an ability to
control P. digitatum and P. italicum decreasing
germination rate
22. Biological control:
veral yeasts and bacteria have been demonstrated to have
antagonistic abilities against P. digitatum and P. italicum.
The yeast antagonists are assumed to operate by inducing
phytoalexins (Rodov et al., 1994) or by competition for nutrients
(Droby et al., 1989); no antibiotics are known (Cheah et al.,
1995).
The mechanism of biocontrol for Bacillus spp. is assumed to be
antibiotic production (Rodov et al., 1994).
Some strains of Pseudomonas cepacea, while being antagonistic
towards P. digitatum and P. italicum, also retard wound
healing in orange fruits (Huang et al., 1991).
23. A biocontrol product based on a formulation of
Pseudomonas syringae strain ESC-10 is now commercially
available under the trademarked name BIO-SAVE 1000
Various natural products have been tested for their
effectiveness at controlling P. digitatum.
An 'essential oil' from Thymus capitatus had similar
effectiveness in vitro to thiabendazole (Arras et al., 1994);
gel from Aloa barbadensis slowed and reduced infection of
inoculated gSerapefruit (Saks and Barkai-Golan, 1995).
Similar results have been obtained with extracts from a
variety of herbs
24. Cultural control:
Minimizing fruit injury and the efficient removal of
infected fruit are the most effective ways to control this
disease.
Disinfectants can be used to clean equipment in
packing and storage facilities (Brown and Eckert,
1988).
Ripening or degreening of fruit at 30°C and 95% RH
promotes healing of wounds before fungal
colonization can occur (Snowdon, 1990).
25. Cont…
The disease develops most rapidly at temperatures near 24°C
and fruit is thus usually refrigerated during storage (Brown
and Eckert, 1988).
Postharvest washing at 40-50°C in detergent or weak alkali
solutions, usually including some fungicides , reduces decay.
Individual wrapping of fruit in wax paper, or packaging in
trays, prevents spread from infected to uninfected fruit
during transport or storage.
Storage at 5°C in a high carbon dioxide atmosphere reduces
rot (Amarjit-Singh et al., 1992).
Inclusion of a pouch of KOH in polyethylene wrapped fruit
reduces rot (Piga et al., 1997).
26. Ultraviolet light and higher temperatures induce
formation of the phytoalexin scoparone, which
promotes healing of wounded tissues (Pitt and
Hocking, 1997.
Gamma irradiation of grapefruits with 0.3 kGy reduced
decay, but higher levels may cause peel damage (Miller
and McDonald, 1996).
27. References:
Pitt, John I.; Hocking, Alisa D. (1985). Fungi and food spoilage (3rd ed).
Dordrecht: Springer. ISBN 9780387922072.
Onions, A.H.S. "Penicillium digitatum. C.M.I. Descriptions of Fungi and
Bacteria No. 96". Descriptions of Fungi and Bacteria. CAB International
Wallingford UK.
Smith, I.M. (1988). European handbook of plant diseases ([Online-Ausg.] ed.).
Oxford [Oxfordshire]: Blackwell Scientific Publications. ISBN 978-0632012220.
Wilson, Charles L.; Wisniewski, Michael E.; Biles, Charles L.; McLaughlin,
Randy; Chalutz, Edo; Droby, Samir (1991-06-01). "Biological control of post-
harvest diseases of fruits and vegetables: alternatives to synthetic
fungicides". Crop Protection. 10 (3): 172–177. doi:10.1016/0261-2194(91)90039-T.
Marcet-Houben, Marina; Ballester, Ana-Rosa; de la Fuente, Beatriz; Harries,
Eleonora; Marcos, Jose F.; González-Candelas, Luis; Gabaldón, Toni (2012-01-
01). "Genome sequence of the necrotrophic fungus Penicillium digitatum, the
main post-harvest pathogen of citrus". BMC Genomics. 13: 646. doi:10.1186/1471-
2164-13-646. ISSN 1471-2164. PMC 3532085. PMID 23171342.
28. Brown, G. Eldon. "Citrus Diseases-
PostHarvest" (PDF). University of Florida: IFAS Indian River
Research and Education Center. University of Florida.
Fergus, Charles L. (1952-03-01). "The Nutrition of
Penicillium digitatum Sacc". Mycologia. 44 (2): 183–
199. doi:10.1080/00275514.1952.12024184. JSTOR 4547585.
Issues in General Food Research: 2013 Edition.
ScholarlyEditions. 2013-05-01. ISBN 9781490106892.
Barron, George. "Penicillium italicum and Penicillium
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