Submitted to: Biological and Cultural Tests for Control of Plant Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 23, 2006
Publication Date: April 20, 2006
Citation: Hanson, L.E., Panella, L.W. 2006. Rhizoctonia root rot resistance of Beta pis from the USDA-ARS NPGS, 2005. Biological and Cultural Tests for Control of Plant Diseases. Interpretive Summary: Rhizoctonia root and crown rot is the most serious fungal root disease of sugar beet in the United States. Rhizoctonia root rot is difficult to control, and development of sugar beet cultivars with resistance to the disease is important for disease management. In 2005, 30 Plant Introductions from the USDA-ARS National Plant Germplasm System were tested for resistance to Rhizoctonia root rot. Plants were rated for disease in early September. Three of the Plant Introductions had disease levels percentages of harvestable roots that were not significantly different from the resistant control.
Technical Abstract: Thirty Plant Introductions (PI) from the USDA-ARS National Plant Germplasm System were evaluated for resistance to Rhizoctonia root rot. Materials were planted at the Crops Research Lab-Fort Collins Research Farm in CO and inoculated with dry, ground, barley-grain inoculum of Rhizoctonia solani isolate R-9. Immediately after inoculation, a cultivation was performed to throw soil into the beet crowns. At harvest, each root was rated for rot on a scale of 0 (no damage) to 7 (completely rotted). Analyses of variance were performed on disease indices (DI), percent healthy roots (undamaged classes 0 and 1 combined), and percentage of roots in classes 0 thru 3 (those most likely to be harvested and taken to the factory). Percentages were transformed using arcsine-square root to normalize the data for analyses. Good disease developed by mid-September. Differences in DI among entries were highly significant (P < 0.001). Mean DI across all tests in the 2004 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 were 27.6, 25.4, and 6.4%