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 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 26th; immediately after inoculation, a cultivation was performed so as to throw soil into the beet crowns. The field was thinned by hand and irrigated as necessary. Beets were harvested the week of September 18. Each root was rated for rot on a scale of 0 to 7 (dead) as previously described. ANOVAs were performed on disease indices (DIs). Although planting was on schedule, a very cold, wet weather retarded plant growth and forced almost a two week dely in inoculation and evaluations. Nevertheless, the hot, dry weather of late July and August provided ideal conditions for the development of an excellent disease nursery. Differences among entries in all tests were highly significant. Mean DIs across all tests for highly resistant Fc705-1, resistant FC703, and the susceptible control were 1.7, 2.1, and 4.3, respectively. The highest and lowest DIs for contributor lines were 6.6 and 0.9 respectively.