Evaluation location: Colorado, United States
There were five replications in each test, which were arranged in randomized complete block designs. Rhizoctonia-resistant line FC703 and a highly susceptible check (FC901/C817) were included as internal controls, along with highly resistant FC705-1. One-row plots, planted May 20th, were 14 feet long with 22 inches between rows and 8-10 inches within-row spacing. Inoculation with dry, ground, barley-grain inoculum of Rhizoctonia solani isolate R-9 was performed on July 13th; immediately after inoculation, a cultivation was performed so as to throw soil into the beet crowns. The field was sprayed twice with Betamix Progress, Upbeet, and Stinger (June 2 and 12) to control weeds. The field was thinned by hand and irrigated as necessary. Beets were harvested August 23 through 27. Each root was rated for rot on a scale of 0 to 7 (dead) as previously described which have been converted to a 1 to 9 scale. ANOVAs were performed on disease indices (DIs).We had unusually heavy spring rainfall before planting and were able to plant to moisture. We also had just a little rain in the week after planting with warming temperatures (see accompanying summary of weather data). Therefore, stands were excellent and the 1999 Rhizoctonia epidemic started strong and progressed quickly, becoming severe by mid August. Differences in DIs among entries in all tests were highly significant (P < 0.001). Mean DIs across all tests for highly resistant FC705-1, resistant FC703, and the highly susceptible check were 3.3, 3.9, and 6.2, respectively. The highest and lowest DIs for evaluated lines were 6.8 and 2.0, respectively.