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Verticillium is a genus of fungi in the division Ascomycota, and are an anamorphic form of the family. The genus used to include diverse groups comprising saprobes and parasites of higher plants, insects, nematodes, mollusc eggs and other fungi thus it can be seen that the genus used to have a wide ranging group of taxa characterised by simple but ill-defined characters. The genus, currently thought to contain 51 species,^1] may be broadly divided into three ecologically based groups 1) mycopathogens 2) entomopathogens (Zare and Gams, 2001) and 3) plant pathogens and related saprotrophs (Barbara and Clewes, 2003). However, recently the genus has undergone some revision into which most entomopathogenic and mycopathogenic isolates fall into a new group called Lecanicillium. The genus now includes the plant pathogenic species V. dahliae, V. albo-atrum, V. nubilium, and V. tricorpus.

The better known species of Verticillium are, V. dahliae and V. albo-atrum cause a wilt disease called Verticillium wilt in more than 400 eudicot plant species.

Selected species

Verticillium dahliae infecting sunflower

• Verticillium dahliae Kleb.

Verticillium conidiophores

• Verticillium albo-atrum Reinke & Berthold - Causes Verticillium Wilt or Maple Wilt. First identified from potatoes in Germany in 1870, this species attacks over 300 different cultivated plants and can persist as a saprotrophic soil organism for more than 15 years. When infecting ornamental trees like maples, elms, aspen, ash, beech, catalpa, oak and others, the first symptoms are midsummer wilting on one side of a tree or branch. The sapwood has greenish or brownish streaks, and the infection can take a few years to progress to the rest of the tree or move rapidly. The fungi universally move up the xylem vessels. In fruit trees the infection is known as 'Black Heart' and is common in apricots and sometimes affects almond, peach, plum and avocado trees. This fungus also affects herbaceous ornamentals and vegetables like Chrysanthemum, mints, Lychnis, tomatoes, eggplants, okra, and rhubarb, causing wilting and death. Identification can be made by looking for one-celled conidia, hyaline round to ellipsoid which are formed at the tips of whorled branches. They are easily separated from the tips.

• Nematode pathogens, previously in Verticillium, have now been placed in the new genus Pochonia.

• All insect pathogens have been placed in the new genus Lecanicillium^[2]. An approved name of Verticillium lecanii (Zimmerman) Viegas is now Lecanicillium lecanii although this now also includes: L. attenuatum, L. longisporum, L. muscarium and L. nodulosum.

Verticillium dahliae infecting sunflower

• Verticillium dahliae Kleb.

Verticillium conidiophores

• Verticillium albo-atrum Reinke & Berthold - Causes Verticillium Wilt or Maple Wilt. First identified from potatoes in Germany in 1870, this species attacks over 300 different cultivated plants and can persist as a saprotrophic soil organism for more than 15 years. When infecting ornamental trees like maples, elms, aspen, ash, beech, catalpa, oak and others, the first symptoms are midsummer wilting on one side of a tree or branch. The sapwood has greenish or brownish streaks, and the infection can take a few years to progress to the rest of the tree or move rapidly. The fungi universally move up the xylem vessels. In fruit trees the infection is known as 'Black Heart' and is common in apricots and sometimes affects almond, peach, plum and avocado trees. This fungus also affects herbaceous ornamentals and vegetables like Chrysanthemum, mints, Lychnis, tomatoes, eggplants, okra, and rhubarb, causing wilting and death. Identification can be made by looking for one-celled conidia, hyaline round to ellipsoid which are formed at the tips of whorled branches. They are easily separated from the tips.

• Nematode pathogens, previously in Verticillium, have now been placed in the new genus Pochonia.

• All insect pathogens have been placed in the new genus Lecanicillium^[2]. An approved name of Verticillium lecanii (Zimmerman) Viegas is now Lecanicillium lecanii although this now also includes: L. attenuatum, L. longisporum, L. muscarium and L. nodulosum.

References

• Barbara, D.J. & Clewes, E. (2003). "Plant pathogenic Verticillium species: how many of them are there?" Molecular Plant Pathology 4(4).297-305. Blackwell Publishing.
• Phillips, D. H. & Burdekin, D. A. (1992). Diseases of Forest and Ornamental Trees. Macmillan. ISBN 0-333-49493-8.
• Zare,R. and Gams, W. (2001). A revision of Verticillium sect. Prostrata. III. Generic classification. Nova Hedwigia. 72. 329-337.

External links

• Fact sheet from Ohio State University Extension on verticillium and fusarium