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You are here: Home / Archives for Verticillium

Clavicipitales: Verticillium Nees

Jackson Kung'u

Colonies moderately rapidly growing. Conidiophores fairly well differentiated from the usually hyaline vegetative hyphae, erect or prostrate, hyaline or pigmented, verticillately branched over most of their length, with successive whorls of conidiogenous cells. Conidiogenous cells slender, gradually tapering, producing conidia successively from single apical conidiogenous loci. Conidia small, hyaline, usually aseptate, in most species aggregating into spherical slimy heads but formed in chains in a few taxa.

Verticillium is clearly an unnatural form-genus, with links both to the Clavicipitales and to the Hypocreales. Many of the species of interest to the industrial mycologist have links with the Clavicipitales, so the form-genus is treated here. However, the type species V. tenerum Nees has links with the Hypocreales, and a few other species of Nectria have since been reported with Verticillium anamorphs, but the anamorph has such a simple structure that it is likely that convergent evolution has taken place.

The latest taxonomic work on Verticillium is the study by Jun et al. (1991), which compared isolates of V. lecanii from insect and fungal hosts. Further information may be found in Domsch et al. (1980), Ellis (1971), Evans & Samson (1986), Gams (1971, 1988) , and Gams & van Zaayen (1982). Verticillium species are widespread in soil, and are pathogens of other fungi, insects and plants. Recently, they have become important in biological control programmes.

Verticillium albo-atrum Reinke & Berthold

Colonies white at first, then turning black in patches. Conidiophores usually only with one order of branching, hyaline though sometimes with a darkened base. Conidiogenous cells in whorls of 2-4, narrow, gradually tapering. Conidia 3.5-10.5 x 2-5µm, ellipsoidal to cylindrical, hyaline, occasionally septate. This species is a serious parasite, causing wilt diseases of many plants. Verticillium dahliae Kleb. is also a serious pathogen, which has dark multicellular resting structures sometimes referred to as microsclerotia, hyaline conidiophores, and slightly smaller conidia.

Verticillium fungicola (Preuss) Hassebrauk

Colonies white to cream, powdery to velvety. Conidiophores erect, with a single order of branching. Conidiogenous cells in whorls of 3-9, narrow, gradually tapering. Conidia 3-8.5 x 1-2.5µm, ellipsoidal to cylindrical, sometimes curved in older colonies, aseptate. Resting spores not produced.

This species, also referred to in some circles as Verticillium malthousei Ware, causes the diseases of commercial mushroom beds known as “dry bubble” and “brown spot”. It can cause serious losses.

Verticillium psalliotae Treschow is similar to V. fungicola, but has less-branched conidiophores which are usually prostrate, purple pigments at the edge of the colonies, Conidiogenous cells usually in groups of 2-3, and conidia which are crescent-shaped in young cultures and cylindrical to ellipsoidal in older colonies. V. lamellicola (F.E.V. Sm.) W. Gams is similar to V. psalliotae, but has conidia which are not curved. It also causes diseases of mushroom beds.

Verticillium lecanii (Zimmermann) Viegas

Col0nies white to pale yellow, cottony. Conidiophores not well-developed, erect or prostrate, with a single order of branching. Conidiogenous cells in whorls of 3-5, narrow, gradually tapering. Conidia variable in size (dependent on the host), ranging between 2.3-10µm in length and 1-2.6µm in width, cylindrical to ellipsoidal.

Interest in Verticillium lecanii as an agent of biological control is considerable. The fungus is pathogenic on a number of economically important insects, and strains are also parasitic on rust and other fungi. Jun et al. identified a number of taxonomic groups within the species aggregate largely based on host preference. The fungus also produces antiviral agents (Bucknall et al., 1973).

Verticillium tenerum Nees

Colonies growing rapidly, velvety, brick-red to orange-brown. Conidiophores erect, stiff, strongly pigmented, often branched several times. Conidogenous cells 12-23 x 2-4µm, flask-shaped. Conidia 3.5-5 x 2-2.5µm, pale reddish brown in mass. Resting structures not produced. This fungus is better-known under the name Verticillium lateritium (Ehrenb.) Rabenh, and the synonym Acrostalagmus cinnabarinus Corda may also be familiar to some. It has been reported to be the anamorph of Nectria inventa Pethybridge, but that fungus is poorly-known, and is certainly not a typical Nectria. The evidence of connexion is based solely on a single early report (Pethybridge, 1919), and the teleomorph has not recently been found. V. tenerum is a common and cosmopolitan soil fungus. It has also been found on paper, cloth, cotton fibres in conveyor belts, and rotting vegetables, and been isolated from milk, cheese, giner, wheat and salami (Domsch et al., 1980; Pitt & Hocking, 1985a).

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Filed Under: Fungi Tagged With: clavicipitales, Hypocreales, Nectria, Verticillium

Seed Pathogen Testing

Jackson Kung'u

Question: Hello, I represent a very important agro-industrial group in Mexico. We have several roles such as wheat mills, fruit, and vegetable processing.

Right now we have a situation in one of our facilities that we want to resolve. We have a hydroponic greenhouse where we produce lettuce, mainly 3 different varieties (Boston, Lollobionda, Lollorosa). We have had several problems in the production of lettuce. We did some analysis and we have found that the root cause of the problem is in the seed.

This seed comes from Holland, and the seed is encapsulated by some material that is supposed to protect the naked seed and improve the shelf life. In our studies we have found that the encapsulation material is contaminated with some fungal pathogens and bacteria, so this is why we are requesting your support.

In a research institute in Mexico they found in the encapsulation material the following fungal pathogens and bacteria:

– Fusarium
– Verticillium
– Acremonium
– Phythium
– Aspergillus
– Stenotrophomonas
– Acinetobacter
– Bacillus cereus

So we want to confirm with your labs if these microorganisms are present in the seed or in the encapsulation material. So we need to know if your labs are able to do this analysis, the cost of the analysis and how much time you think this will take. If by some reason MBL are not able to do this kind of analysis, could you recommend some laboratory that could help us with this request.

I’ll wait for your comments, thanks and best regards.
Answer: We can you determine the fungal and bacterial pathogens present in the seeds and the encapsulation material. However, since this material is coming from outside of Canada, an import permit from the Canadian Food Inspection Agency (CFIA) would be required. We would suggest you use a lab in Mexico for this kind of testing.

Filed Under: Fungi Tagged With: Acinetobacter, Acremonium, Aspergillus, Bacillus, Fusarium, Phythium, pthogen, seed, seeds, Stenotrophomonas, Verticillium

Which Moulds Grow in Buildings And Why Do They Grow?

Jackson Kung'u

The level of moisture (usually referred to as water activity) in building material determines not only whether mould will grow or not but also the types that colonize the material. Damp materials with a water activity value equal to or greater than 0.90 are usually colonized by strains of Aspergillus fumigatus, Trichoderma spp., Exophiala spp., Stachybotrys spp., Phialophora spp., Fusarium spp., Ulocladium spp., and yeasts such as Rhodotorula spp. Materials with a water activity value ranging from 0.90 – 0.85 are colonized by Aspergillus versicolor while those with water activity values of 0.85 or slightly less are colonized by Aspergillus versicolor, Eurotium spp., Wallemia spp., and Penicillium spp., such as Penicillium chrysogenum and Penicillium aurantiogriseum.

Water leakage through roofs, defective plumbing installations and condensation are the main sources for water damage with subsequent mould growth. The building materials most susceptible to mould attacks are water damaged, aged organic cellulose containing materials such as wood, jute, wallpaper, and cardboard. Moulds that are most frequently encountered in buildings are Penicillium (68%), Aspergillus (56%), Chaetomium (22%), Ulocladium (21%), Stachybotrys (19%), Cladosporium (15%), Acremonium (14%), Mucor (14%), Paecilomyces (10%), Alternaria (8%), Verticillium (8%), and Trichoderma (7%). These moulds are all known to cause different types of inhalation allergy.

Do you have a question concerning indoor moulds? Send it to us at My Question.

Filed Under: Fungi Tagged With: Acremonium, Alternaria, Aspergillus, chaetomium, cladosporium, Mucor, Paecilomyces, penicillium, stachybotrys, Trichoderma, Ulocladium, Verticillium, water activity, water damage

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