Discovering the sexy side of valued fungi.

Soil fungi of the genus Trichoderma have numerous commercial applications.

Clothing manufacturers use the cellulose-degrading enzymes produced by the fungi to give jeans a "stone-washed" look. Some household laundry detergents contain such enzymes to help remove fabric nubs. Farmers employ Trichoderma to attack fungi that harm crops.

Like most commercially valuable fungi, the available strains of this workhorse reproduce only asexually, which makes selective breeding impossible. But researchers now report finding sexual variants.

Scientists recently collected from Puerto Rico and Uganda samples of fungi identified as the rare Hypocrea poronioidea, last collected and studied at the turn of the century. This fungus reproduces sexually and can be grown in the laboratory.

Although the two fungi don't look alike, DNA and enzyme analyses suggest that H. poronioidea is actually the sexual version of a Trichoderma species-but which species remains unclear, report Gary J. Samuels of the U.S. Department of Agriculture's Agricultural Research Service (ARS) in Beltsville, Md., and D.J. Lodge of the USDA's Forest Service in Palmer, Puerto Rico, in an upcoming Mycologia.

Fungi commonly have sexual and asexual variants, which can go by different names. Samuels and Lodge observe that H. poronioidea generates both sexual and asexual spores. The asexual spores develop into Trichoderma.

Other genetic studies suggest that a well-known fungus called Hypocrea jecorina may be the sexual version of another Trichoderma species, T. reesei, contend Samuels, Adrian Leuchtmann of the Swiss Federal Institute of Technology in Zurich, and Orlando Petrini of Pharmaton in Bioggio, Switzerland. Their work is scheduled to appear in Mycologia later this year.

Manufacturers use a strain of T. reesei collected from a cotton tent on a South Pacific Island during World War II, says Amy Y. Rossman of ARS. The new studies will allow researchers to improve commercial strains through selective breeding, speculates Samuels.

Having these sexual fungi should help scientists classify Trichoderma, which has proved difficult, says Gary E. Harman of Cornell University's New York State Agricultural Experiment Station in Geneva. Correctly identifying fungi is important for securing patents on their uses. However, selective breeding will be possible only between sexually compatible strains, he notes.