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Title: REDUCTION OF FUSARIUM WILT OF HYDROPONICALLY-GROWN BASIL BY FUSARIUM OXYSPORUM STRAIN CS-20

Author
item Fravel, Deborah
item Larkin, Robert - Bob

Submitted to: Crop Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/16/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: Fusarium wilt causes severe economic losses on many crops. This study was conducted to determine if beneficial Fusarium (strain CS-20)could control F. wilt on basil. We also wanted to find out if changing the way basil was seeded could slow the spread. Experiments were conducted at a commercial hydroponic facility; 2% of the seed was naturally infected with the pathogen. There were significantly fewer dead and wilted plants following treatment with CS-20 compared to those treated with water only. Because the pathogen is carried on seed and infections in the seedling stage cause much greater loss than later infections, we compared 2 different ways to seed basil to see if spread of the pathogen could be slowed. For this hydroponic system, basil plants are usually seeded into cubes which are physically attached to each other. We compared these cubes to wedges where each unit is physically separated by plastic. Pathogen spread was significantly greater in the cubes than the wedges. The data demonstrate the potential of strain CS-20 to control F. wilt of basil and the potential of physical separation of seedlings prior to placement in the hydroponic system to reduce spread of the pathogen in seedling stage. This information will be used by scientists developing controls for F. wilt.

Technical Abstract: Basil seedlings were drenched with water or F. oxysporum strain CS-20. The following week, plants were placed in hydroponic troughs with a circulating nutrient solution. Since 2% of the seed was naturally infested with Fusarium oxysporum f. sp. basilici, pathogen inoculum was not applied. After 7 weeks, there were significantly fewer dead stems and fewer wilted plants in plants treated with strain CS-20 than in the control treatment. Laboratory experiments were conducted to determine a different type of seeding medium could retard dispersal of the pathogen. Oasis cubes and wedges were seeded with basil. The cube or wedge nearest to the center was inoculated with 10-5 propagules of the pathogen or water. After one and two weeks, treatments were destructively sampled. For treatments inoculated with the pathogen, the number of colony forming units (cfu) recovered decreased significantly as the distance from the inoculation site increased. Significantly more cfu were recovered from cubes than from wedges inoculated with the pathogen, indicating that the cubes were more conducive to pathogen dispersal than the wedges. In the cubes, the pathogen was recovered from 13 cm away from the inoculation site at populations significantly higher than background levels (up to 10-6 propagules/cube).