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[nafex] FW: Fusarium Wilt May be Controlled by Other Fusarium Strains



This item is one of the news releases and story leads that ARS Information
distributes on weekdays to fax and e-mail subscribers. You can also get the
latest ARS news on the World Wide Web at
www.ars.usda.gov/is/pr/thelatest.htm.
* Feedback and questions to ARS News Service via e-mail: isnv@ars-grin.gov.
* ARS Information Staff, 5601 Sunnyside Ave., Room 1-2251, Beltsville MD
20705-5128, (301) 504- 1617, fax (301) 504-1648.
----------
From: "ARS News Service" <isnv@ars-grin.gov>
To: "ARS News List" <ars-news@ars-grin.gov>
Subject: Fusarium Wilt May be Controlled by Other Fusarium Strains
Date: Fri, Jul 14, 2000, 7:44 AM


STORY LEAD:
Fusarium Wilt May be Controlled by Other Fusarium Strains

___________________________________________

ARS News Service
Agricultural Research Service, USDA
Sharon Durham, (301) 504-1611, sdurham@asrr.arsusda.gov
July 14, 2000
___________________________________________

Agricultural Research Service scientists and cooperators are searching for
environmentally-friendly ways to control plant diseases. In the case of
Fusarium wilt, beneficial stains of Fusarium are being used to control plant
pathogenic strains. In tests so far, some of the beneficial Fusarium are
winning--and that's good news for tomato growers who need an alternative to
the chemical fumigant methyl bromide.

The scientists' enemy is a pathogenic strain of Fusarium oxysporum that
causes Fusarium wilt. Fusarium wilt afflicts many vegetables, melon and
other crops such as basil, causing severe losses. Fusarium wilt, however, is
a particular problem for tomatoes since there is a new race of the pathogen
that attacks tomatoes. For now, methyl bromide is used to keep this pathogen
at bay. But by 2005, methyl bromide will be phased out, because it is
identified as an ozone-depleting chemical. So scientists are studying
alternatives that are environmentally safe while still effective against the
pathogen.

Deborah R. Fravel, a plant pathologist at ARS' Biocontrol of Plant Diseases
Laboratory in Beltsville, Md., and George Lazarovits, research scientist and
team leader with Agriculture and Agri-Food Canada in Ontario, Canada, are
working in a cooperative study to find methyl bromide alternatives. In their
studies, they're pitting harmless Fusarium species and other "good guy"
biocontrol organisms against the wilt-causing F. oxysporum.

The scientists tested several beneficial strains of F. oxysporum against the
wilt-causing strain. They found one strain, CS-20, reduced wilt by 49.6
percent. They also mixed beneficial strains of a fungus (Trichoderma virens
strain G1-3) and a bacterium (Burkholderia vietnamiensis strain Bc-F). The
fungus/bacterium treatment reduced wilt incidence by 41.6%. Also, CS-20 and
the fungus/bacterium combination treatment significantly increased both the
weight and number of tomatoes on the plant.

Now, researchers must figure out how the biocontrol mechanisms work. Some
biocontrol agents work by competing with the pathogenic strains for
nutrients and space. CS-20 seems to pump up the plants' natural defenses
against pathogens, a reaction called "induced systemic resistance,"
according to Fravel.

___________________________________________

Scientific contact: Deborah Fravel, ARS Biocontrol of Plant Diseases
Laboratory, Beltsville, Md.; phone (301) 504-5080, fax (301) 504-5968;
fraveld@ba.ars.usda.gov.
___________________________________________
This item is one of the news releases and story leads that ARS Information
distributes on weekdays to fax and e-mail subscribers. You can also get the
latest ARS news on the World Wide Web at
www.ars.usda.gov/is/pr/thelatest.htm.
* Feedback and questions to ARS News Service via e-mail: isnv@ars-grin.gov.
* ARS Information Staff, 5601 Sunnyside Ave., Room 1-2251, Beltsville MD
20705-5128, (301) 504- 1617, fax (301) 504-1648.





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