GAINESVILLE, Fla. — Forest industry professionals know it’s important to screen pine seeds for the presence of the fungus that causes pitch canker disease – so important that many countries require screening before importing seeds.

But the screening method currently endorsed by the International Seed Testing Association is slow and yields uncertain results, according to a research team that developed an alternative method and reported it in the October 2012 issue of the journal Forest Pathology.

That method, known as the blotter paper test, involves culturing fungus spores present in pine seed, then examining any suspect fungal colonies to determine if they contain the pitch canker pathogen, Fusarium circinatum.

However, users are not required to seek and identify the truly telltale part of the pathogen, branchlike structures called coiled hyphae. Consequently, the results may include both false positives and false negatives if other fungi in the Fusarium genus are present.

The research team, which included forest pathologist Jason Smith, an associate professor with the University of Florida’s Institute of Food and Agricultural Sciences, developed a test that uses real-time polymerase chain reaction, which can detect a specific DNA molecule, eliminating any doubt about the identity of a fungus.

In the study, researchers took samples from commercially available slash pine seed lots, and drew DNA samples from hundreds of individual seeds. Then they screened for F. circinatum by modifying two previously published real-time PCR techniques and upscaling the method to accommodate large numbers of seeds in a single testing session.

The team also analyzed seed from the same lots using the blotter paper test.

The results showed that real-time PCR detected F. circinatum in two of three samples from a seed lot that passed the blotter paper test with flying colors. In addition, real-time PCR took two days of waiting and three hours of work to test one seed lot, compared with the blotter paper test, where researchers must wait for a week or two as fungal colonies grow and then spend nine hours inspecting seeds to test one lot.

Smith reports that the real-time PCR test will probably be tested at a large forestry nursery in Alabama, in a study that involves Auburn University researchers and funding from the U.S. Forest Service.

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Contacts

Writer: Tom Nordlie, 352-273-3567, tnordlie@ufl.edu

Source: Jason Smith, 352-846-0843, jasons@ufl.edu

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