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United States Department of Agriculture

Agricultural Research Service

Title: USDA-ARS Sugar Beet Germplasm Developed in Fort Collins, Co, Evaluated for Rhizoctonia Resistance, 2002.

Authors
item Panella, Leonard
item Hanson, Linda

Submitted to: Biological and Cultural Tests for Control of Plant Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 20, 2003
Publication Date: June 30, 2003
Citation: PANELLA, L.W., HANSON, L.E. USDA-ARS SUGAR BEET GERMPLASM DEVELOPED IN FORT COLLINS, CO, EVALUATED FOR RHIZOCTONIA RESISTANCE, 2002. BIOLOGICAL AND CULTURAL TESTS FOR CONTROL OF PLANT DISEASES. 2003.

Interpretive Summary: Interpretive Summary Forty sugar beet germplasm lines released over the past 30 years, or under development by the USDA-ARS Sugar Beet Research Unit located in Fort Collins, CO were evaluated for resistance to Rhizoctonia root rot. We had high temperatures in the summer of 2002 and the Rhizoctonia root rot epidemic progressed quickly, becoming severe by the beginning of September. There was a significant difference between all the resistant germplasm and the susceptible control with two exceptions. A 1993 seed increase of FC704 was significantly more susceptible than the susceptible control and FC702, and early release (1968), was not significantly different from the susceptible control . Even though all the other germplasm performed significantly better than the susceptible control there were significant differences among resistant germplasm. FC701, the first Rhizoctonia-resistant germplasm, released in 1968, performed the worst of these.

Technical Abstract: Technical Abstract Forty sugar beet germplasm lines released over the past 30 years, or under development 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. One-row plots, replicated five times were planted at the Crops Research Lab-Fort Collins Research Farm, CO, on 23 May. Plots were 4.5 m long with 56 cm between rows and 20 to 25 cm within-row spacing. Inoculation with dry, ground, barley-grain inoculum of Rhizoctonia solani isolate R-9 (AG 2-2) was performed on 17 Jul; immediately after inoculation, a cultivation was performed to throw soil into the beet crowns. The field was thinned by hand and irrigated as necessary. Beets were harvested 3 through 6 Sept. Each root was rated for rot on a scale of 0 (no damage) to 7 (dead). Analyses of variance (PROC GLM - SAS) were performed on disease indices (DIs), 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 arcsin-square root to normalize the data for analyses. We had high temperatures in the summer of 2002 and a moderate inoculum load. The Rhizoctonia epidemic progressed quickly, becoming severe by the beginning of September. Differences in DIs among entries were highly significant (P < 0.001). Mean DIs across all tests in the 2002 nursery for highly resistant FC705-1, resistant FC703, and highly susceptible FC901/C817 controls were 1.89, 2.24, and 4.40 respectively. Percentages of healthy roots were 39.3, 35.9, and 10.0% for these controls. Percentages of roots in disease classes 0 thru 3 were 91.2, 86.3, and 37.1%, respectively. The highest and lowest DIs for the evaluated lines were 6.5 and 1.3, respectively. There was a significant difference between all the resistant germplasm and the susceptible control with two exceptions. A 1993 seed increase of FC704 was significantly more susceptible than the susceptible control and a FC702, and early release (1968) was not significantly different from the susceptible control . Even though all the other germplasm performed significantly better than the susceptible control there were significant differences among resistant germplasm. FC701, the first Rhizoctonia-resistant germplasm, released in 1968, performed the worst of these.

Last Modified: 10/1/2014
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