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ARS Home » Midwest Area » East Lansing, Michigan » Sugarbeet and Bean Research » Research » Publications at this Location » Publication #97286
Title: PROGRESS IN DEVELOPMENT OF A SUGARBEET SEEDLING ASSAY FOR RESISTANCE TO APHANOMYCES COCHLIOIDES

Author
item JOHNSON, DAVID - MICHIGAN STATE UNIVERSITY
item Halloin, John

Submitted to: American Society of Sugarbeet Technologists
Publication Type: Abstract Only
Publication Acceptance Date: 2/12/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: The pathogen Aphanomyces cochlioides Dresch. causes extensive damping-off of seedlings and root rot on surviving sugarbeets (Beta vulgaris L.) in warm, wet soils. Within the United States, development of germplasm resistant to this pathogen relies on a naturally infested field nursery in Minnesota, a situation that provides time limitations on researchers, and inherent variability of the disease environment. Past efforts to minimize these problems through use of greenhouse assays have provided inconsistent results. This inconsistency of results was likely due to a lack of understanding of natural infection in the field, coupled with a lack of understanding of the modes of resistance to A. cochlioides already present in some sugarbeet varieties. We are developing a soil-less assay for resistance to Aphanomyces seedling disease using rolled germination paper in growth chambers and zoospore inoculum. In this system, resistance to damping-off is strongly temperature dependent: high at 15 deg C, intermediate at 20 and 25 deg C, and low at 30 deg C. Under conditions of intermediate resistance (25 deg C), attempts to find significant differences in disease severity between susceptible (eg. Edda) and resistant (eg. USH20, ACH 555, and 68-22) varieties have yielded inconsistent results, apparently due to variability of factors in the system. Work is underway to refine the system: further reducing variability in the host, the environment, and the inoculum.