Penicillium hirsutum explained

A species of the genus of Penicillium which causes Blue Mold of Garlic on Allium sativum L.^{[1] [2] [3]} The genus name is derived from the Latin root penicillum, meaning "painter's brush", and refers to the chains of conidia this fungus produces that resemble a broom.^[4]

Blue mold of garlic occurs during harvest and storage, and is particularly prevalent on fresh garlic.^[5] This pathogen affects a wide range of hosts in addition to garlic throughout the world including apple, citrus fruits, corn, grape, melon, and pear.

Disease Symptoms

Initial symptoms of blue mold of garlic caused by Penicillium hirsutum include water-soaked or pale-yellow areas on the outer surface of scales.^{[6] [7]} As disease progresses, a green to blue-green, powdery mold may develop on the surface of the lesions. Infected areas of fleshy scales are tan or gray when cut. In advanced stages of disease, infected bulbs may disintegrate into a watery rot, often because of secondary infection by bacteria or yeasts.

Disease Cycle and Epidemiology

Penicillium spp. commonly grow on plant and animal debris on soil, and in senescing plant tissues. In garlic, it is thought that the pathogen survives in infected cloves rather than the soil. Initial infection usually occurs through wounded plant tissue caused by bruising, sun-scald, freezing injury or mechanical damage to the plant. It is possible, however, for non-wounded bulbs to be infected. Dispersal and secondary infection occurs when infectious spores are carried in the wind, or by infected cloves.

Disease Management

To reduce the risk of blue mold of garlic, care should be taken to manage other diseases and during cultivation to minimize wounding of the plant, as wounds provide avenues of infection. Handle harvested bulbs with care to prevent bruising and wounding, and store them at a maximum temperature of 41 °F and low humidity. In some countries, treating garlic with fungicides prior to storage may be recommended. Cure the bulbs shortly after harvest.

Importance of the Disease: Economic Losses

The diseases caused by Penicillium spp., including blue mold of garlic, have been attributed to significant annual crop losses in Argentina; the world’s second largest exporter of garlic.

Mycotoxins

Penicillium hirsutum produces cyclopiazonic acid^[8] androquefortine C.^[9]

Further reading

• 10.1016/0925-5214(95)00025-9. Low-temperature biology and pathogenicity of Penicillium hirsutum on garlic in storage. Postharvest Biology and Technology. 7. 83. 1996. Bertolini . P.. Tian . S. P. .
• 10.1007/s10658-005-1750-6. Resistance to Penicillium hirsutum Dierckx in garlic accessions. European Journal of Plant Pathology. 112. 2. 195. 2005. Cavagnaro . P. F. . Camargo . A. . Piccolo . R. J. . Lampasona . S. G. A. . Burba . J. L. . Masuelli . R. W. .
• 10.1016/S0953-7562(96)80013-X. Changes in conidial morphology and germinability of Botrytis allii and Penicillium hirsutum in response to low-temperature incubation. Mycological Research. 100. 5. 591. 1996. Tian . S. P. . Bertolini . P. .

Notes and References

1. https://www.uniprot.org/taxonomy/36648 UniProt
2. 10.1007/s10658-005-1750-6. Resistance to Penicillium hirsutum Dierckx in garlic accessions. European Journal of Plant Pathology. 112. 2. 195. 2005. Cavagnaro . P. F. . Camargo . A. . Piccolo . R. J. . Lampasona . S. G. A. . Burba . J. L. . Masuelli . R. W. .
3. Book: Steven T. Koike . Peter Gladders . Albert O. Paulus . Vegetable Diseases: A Color Handbook . Gulf Professional Publishing . 2007 . 0123736757.
4. Abba . Jibril Fuad . 2019 . Preliminary Studies on Fungus Associated with Storage Disease of Garlic (Allium Sativum L.) in Nigeria . Dutse Journal of Pure and Applied Sciences (DUJOPAS) . 5 . 161–168.
5. Book: Schwartz, Howard F. . Compendium of Onion and Garlic Diseases and Pests, Second Edition . Mohan . S. Krishna . 2016-10-28 . The American Phytopathological Society . 978-0-89054-500-3 . Diseases and Pests Compendium Series . 10.1094/9780890545003.
6. Web site: February 2019 . Blue Mold . University of California Agriculture and Natural Resources.
7. Smith . A. M. . February 1976 . The effects of age on the immune response to type III pneumococcal polysaccharide (SIII) and bacterial lipopolysaccharide (LPS) in BALB/c, SJL/J, and C3H mice . Journal of Immunology . 116 . 2 . 469–474 . 0022-1767 . 2635.
8. "Low-temperature biology and pathogenicity of Penicillium hirsutum on garlic in storage", P. Bertolini et al., 1996,https://doi.org/10.1016/S0723-2020(87)80008-5 p. 44
9. Book: John I. Pitt . Ailsa D. Hocking . Fungi and Food Spoilage . Springer Science & Business Media . 2012 . 0387922075.