Evaluation location: Colorado, United States
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 were performed on disease indices (DIs). 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. The highest and lowest DIs for the PI accessions were 6.78 and 3.13 respectively. Four PIs (518644, 535831, 546522 & 590695) had DIs significantly lower than the susceptible control.
View 2002 (A) Rhizoctonia data as an Excel spread sheet (.xls).