Evaluation location: Colorado, United States
2005 Rhizoctonia Nursery - Experiment 2R
The trial was a randomized complete-block design with five replications. One-row plots (56 cm row spacing) were 4 m long and were planted at the Crops Research Lab-Fort Collins Research Farm, CO on 25 May. Inoculation with dry, ground, barley-grain inoculum of Rhizoctonia solani isolate R-9 (AG-2-2) was performed on 28 Jul at a rate of 25 g/m row with inoculum applied to the crown of the plant. Immediately after inoculation, plots were cultivated to throw soil into the beet crowns. The plant population was thinned to 20-25 cm spacing by hand and irrigated as necessary. Beets were harvested 19 Sep, and each root was rated for rot on a Disease Index (DI) scale of 0 (no damage) to 7 (dead plants). The average disease severity was determined to create a disease index for each PI. The scores were adjusted to a 1 (healthy) to 9 (dead) scale: [DI*(9/8)]+1. Two PIs (#504238 and #540566) had such poor emergence that too few plants (one plant for #504238 and 3 for #504566) were present to be rated. Rhizoctonia root rot reached moderate severity levels in early Sep. Differences in the DI among entries were highly significant (P < 0.001). 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. 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.
This test is reported in: Panella, L. and L.E. Hanson. USDA-ARS sugar beet germplasm developed in Fort Collins, CO, evaluated for Rhizoctonia resistance, 2005. Biological and Cultural Tests for Control of Plant Diseases. (online). 21:FC012. DOI: 10. 1094/BC21. The American Phytopathological Society, St. Paul, MN. 2006.