USDA-ARS SUGAR BEET GERMPLASM, EVALUATED FOR RHIZOCTONIA RESISTANCE, 2005.

Authors: Panella, Leonard; Hanson, Linda

Submitted to: Biological and Cultural Tests for Control of Plant Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/23/2006
Publication Date: 4/20/2006
Citation: Panella, L.W., Hanson, L.E. 2006. USDA-ARS sugar beet germplasm, evaluated for Rhizoctonia resistance, 2005. Biological and Cultural Tests for Control of Plant Diseases.

Interpretive Summary: Thirty-seven sugar beet germplasms released over the past 30 years for resistance to Rhizoctonia root-rot by the USDA-ARS Sugar Beet Research Unit located in Fort Collins, CO were evaluated for resistance to Rhizoctonia root rot. The released germplasm differed in Disease Index from a low of 1.9 (FC725) to a high of 5.4 (FC717). All germplasm, with the exception of FC717, performed better than the susceptible check, FC725 was the only line that was better than the resistant check."

Technical Abstract: Thirty-seven sugar beet germplasms released over the past 30 years for resistance to Rhizoctonia root-rot by the USDA-ARS Sugar Beet Research Unit located in Fort Collins, CO were evaluated for resistance to Rhizoctonia root rot. The trial was a randomized complete-block design with five replications. Inoculation was with inoculum of Rhizoctonia solani isolate R-9 (AG-2-2). Beets were harvested, and each root was rated for rot on a scale of 0 (no damage) to 7 (dead plants). The average disease severity was determined to create a disease index for each entry. Analyses of variance (PROC ANOVA - SAS) were performed on disease indices (DI), percent healthy roots (classes 0 and 1 combined) and percentage of roots in classes 0 through 3 (those most likely to be accepted by the factory). Percentage of roots in classes 0-1 and 0-3 were transformed using arcsine-square root to normalize the data for analyses (AP 0-1 and AP 0-3, respectively). The average DI across all tests in the 2005 nursery for highly resistant FC705-1, resistant FC703, and highly susceptible FC901/C817 controls were 2.7, 3.1, and 4.9, respectively. Percentages of healthy roots (those in disease classes 0 to 1) were 27.6, 25.4, and 6.4% for these controls, respectively. The percentages of harvestable roots (those in disease classes 0 through 3) were 59.1, 56.7, and 18.3% for these controls, respectively. The highest and lowest DI for all of the lines evaluated in the nursery, including materials not in the PI tests, were 7.0 and 1.5, respectively. The released germplasm differed in DI from a low of 1.9 (FC725) to a high of 5.4 (FC717). Only FC717 had significantly less resistance than the resistant check, and only FC725 showed more resistance than the resistant check. All germplasm, with the exception of FC717, performed better than the susceptible check