Submitted to: Western Society of Crop Science Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: June 21, 2003
Publication Date: June 22, 2003
Citation: PANELLA, L.W. FORTY YEARS OF BREEDING SUGAR BEET FOR RESISTANCE TO RHIZOCTONIA SOLANI - WHERE ARE WE?. WESTERN SOCIETY OF CROP SCIENCE PROCEEDINGS. 2003. Technical Abstract: Technical Abstract Rhizoctonia root- or crown-rot, caused by Rhizoctonia solani Kühn anastomosis Group 2-2 (AG-2-2), is endemic in sugar beet growing areas. John Gaskill began a breeding program for Rhizoctonia resistance at the USDA-ARS station in Fort Collins, Colorado in the early 1960s. The first two resistant cultivars from this program, FC 701 and FC 702, were released in 1966. Early breeding efforts relied on mass selection or recurrent field selection to improve populations for resistance to root rot because a natural field epiphytotic does not produce the consistent, uniform disease pressure necessary for successful selection for Rhizoctonia resistance. Therefore, it was necessary to define the parameters for producing a successful, artificially-induced epiphytotic. The USDA-ARS Sugarbeet Research Unit at Fort Collins has used field selection in an artificial epiphytotic to develop and register 39 Rhizoctonia resistant germplasm since 1966. Forty one germplasm including many of those lines have been tested over a three-year period to compare the resistance among different germplasm. A disease index (DI) was determined and data were analyzed by Dunnett's one-tailed t test, testing if any entry was significantly (p = 0.05) less than the control (more resistant) and testing if any entry was significantly greater than the best performing entry (more susceptible) - FC709. Two of the early Rhizoctonia-resistant germplasm were not significantly different from a susceptible check, but all of the rest were. Nineteen were as resistant as the most resistant line, FC709, and sixteen were moderately resistant.