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Title: Rhizoctonia Crown and Root Rot Resistance of Beta PI's from the USDA-ARS NPGS, 2009.

Author
item Panella, Leonard
item FENWICK, ANN - Beet Sugar Development Foundation
item Hill, Amy
item Vagher, Travis
item Webb, Kimberly

Submitted to: Plant Disease Management Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2010
Publication Date: 4/29/2010
Citation: Panella, L.W., Fenwick, A.L., Hill, A.L., Vagher, T.O., Webb, K.M. 2010. Rhizoctonia Crown and Root Rot Resistance of Beta PI's from the USDA-ARS NPGS, 2009. Plant Disease Management Reports. 4:FC004

Interpretive Summary: Interpretive Summary: In 2009, Beta vulgaris plant introductions (PI) were screened for Rhizoctonia root and crown rot, at the USDA-ARS Fort Collins, CO Research Farm. After artificial inoculation with R. solani (R-9) average disease severity was determined to create a disease index (DI) for each entry and to rank each variety for susceptibility to Rhizoctonia crown and root rot. In 2009, Rhizoctonia crown and root rot pressure was high and disease development on resistant and susceptible checks was as expected. All experiments in the nursery had significant differences among DI with the most resistant line tested having a DI of 1.8, and the most susceptible line a DI of 7.0. Selections will be made from within those populations that had DI of less than 5.0 to be used for making crosses into sugar beet germplasm.

Technical Abstract: Beta vulgaris plant introductions (PI) were screened for Rhizoctonia root and crown rot, at the USDA-ARS Fort Collins, CO Research Farm. Inoculum of R. solani isolate R-9 (AG-2-2), colonized to dry barley and course ground, was applied to the crown of plants at a rate of 4.8 g/m. Beets were lifted and each root rated on a scale of 0 (no damage) to 7 (dead plant with root completely rotted). Average disease severity was determined to create a disease index (DI) for each entry. Analyses of variance (PROC ANOVA/GLM) were performed on plot disease indices, % healthy roots (classes 0 and 1 combined) and % - roots in classes 0 through 3 (harvestable roots). Data in DI 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). 2009 was an unusual year for rainfall with 10 cm of rain occurring between 1 Jan and planting providing a full profile at planting. Above average rainfall occurred through June and into July providing an additional 17.6 cm precipitation. Daytime temperatures remained at sufficient levels for disease development (25-35oC). Rhizoctonia crown and root rot pressure was high and disease development on resistant and susceptible checks was as expected. All experiments in the nursery had significant differences among DI with the most resistant line tested having a DI of 1.8, and the most susceptible line a DI of 7.0. For 2009, a DI of less than 5.0 is considered to indicate some resistance to Rhizoctonia crown and root rot with several PI’s meeting this cutoff. Next year selections from within those populations will be made and the resistant plants crossed to sugar beet germplasm.