Skip to main content
ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Research Unit » Research » Publications at this Location » Publication #101324
Title: BIOLOGICAL SUPPRESSION OF THE SPREAD OF SEEDBORNE FUSARIUM SPP. DURING COLD STRATIFICATION OF DOUGLAS-FIR SEEDS.

Author
item HOEFNAGALS, M - FORMERLY OSU
item Linderman, Robert

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Container and bareroot conifer nurseries frequently experience serious losses due to the soil- and seed-borne diseases caused by fungal pathogens of Fusarium species. The seedborne fusaria could cause seedling damping off and root rot once seed is planted into the nursery. This study addressed the isolation and identification of the species of Fusarium and their pathogenicity on Douglas-fir seedlings, their spread during cold stratification, and their elimination or suppression by pre-stratification treatments, including application of an antagonistic bacterium as a biocontrol agent. Most of the fusaria appear to be non-pathogenic in the seedlots tested, but pathogens could be present in some seed. Pre- stratification treatment with either hydrogen peroxide or the antagonistic bacterium alone suppressed Fusarium spread during stratification, but the combination of the two was the most effective. Thus this paper reports a new method of biologically controlling damping-off caused by a seedborne pathogen as well as any subsequent root infection that may occur in the nursery. Delivery of the bacterial agent during cold stratification is novel and provides the basis for searching for efficaceous bacteria with improved biocontrol potential.

Technical Abstract: Fusarium spp. are soil and seedborne pathogens of Douglas-fir (Pseudotsuga menziesii) in conifer seedling nurseries. In previous studies, Fusarium spp. were isolated from Douglas-fir seeds, and some were pathogenic on seedlings. We investigated the spread of Fusarium spp. during cold stratification of three Douglas-fir seedlots. A total of nine species (F. avenaceum, F culmorum, F. lateritium, F. moniliforme, F. poae, F. proliferatum, F. sambucinum, F. solani, and F. tricinctum) were isolated; from seeds plated on Komada¿s medium (pH 6.8) at various stages of imbibition and cold stratification progressively increased from 10-22% to 65-100%. Since seedborne Fusarium spp. may add inoculum to nursery soil, another study was conducted to determine whether biological control agents applied during imbibition could reduce the proliferation of Fusarium spp. during stratification. Unstratified Douglas-fir seeds were imbibed for 24 h in a suspension of Pseudomonas chlororaphis isolate Rd31-3A, previously demonstrated to have biocontrol activity agaist F. oxysporum. RD31-3A colonized the seeds and reduced the proliferation of Fusarium spp. during cold stratification without reducing seed germination. The greatest reduction in Fusarium spp. was achieved by treatment with hydrogen peroxide followed by seed imbibition in live bacteria. Application during seed imbibition appears to be an effective means to deliver biological control agents to Douglas-fir seeds.