The effect of temperature and soil water on Fusarium seedling blight of winter wheat and its effective control by fungicide seed treatments

Haigh, Ian Mitchell (2004). The effect of temperature and soil water on Fusarium seedling blight of winter wheat and its effective control by fungicide seed treatments. PhD thesis The Open University.



Seed-borne Microdochium nivale adversely affected seed imbibition and germination to a greater extent at low temperatures (5°C) and low soil water potentials (<-1 MPa) than at high temperatures (≥10°C) and high soil water potentials (>-1 MPa). Post-emergent seedling blight severity was related to rate of seedling emergence. and adversely affected first leaf lengths.

In vitro base temperatures for growth of M. nivale var. majus isolates were lower than for M. nivale var. nivale isolates, however var. majus isolates had a faster growth rate, Microdochium nivale DNA from seed-borne infection, in seeds and seedlings, was not substantially increased at growth stage (GS) 01 or GS 10 at low temperatures or reduced soil water contents.

Timing, duration and harshness of freezing significantly affected seedling blight severity from seed-borne M. nivale infection. Pre-emergent exposure to -5°C more severely reduced final emergence than exposure to 0 °C. Post-emergent freezing had less severe effects on seedling blight severity. Carboxin + thiram seed treatment increased final emergence and reduced seedling blight severity under conditions involving exposure to freezing temperatures.

Seed-borne M. nivale caused foot rot disease, even in the absence of seedling blight symptoms. Seedling blight severity adversely affected subsequent plant growth and was related to the extent of stem colonisation. Carboxin + thiram seed treatment reduced foot rot disease incidence and stem colonisation from seed-borne M. nivale in pot trials and increased plant productivity.

Soil water content and soil temperature between drilling and 30 days post-drilling, had significant effects on plant emergence from M. nivale diseased and pathogen-free seeds in field trials. Poor emergence occurred from seedlots with high seed-borne. M. nivale infection in all three years of field trials and also in one year for a seedlot with low seed-borne M. nivale infection and low seed vigour.

Fungicide seed treatments provided robust control of M. nivale seedling blight under a range of seedbed conditions. Soil water content and soil temperature at drilling and up to 30 days after drilling were important determinants of emergence from treated seeds. Carboxin + thiram was the most effective seed treatment under all seed bed conditions.

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