Experimental sugar beet cultivars evaluated for resistance to bacterial root rot in Idaho, 2008.

摘要

Thirty-six experimental sugar beet cultivars were grown in a commercial sprinkler-irrigated sugar beet field near American Falls, ID where potatoes were grown in 2007. The plots were planted on 21 Apr 08 and managed according to standard cultural practices. Plants were free of foliar and root disease symptoms. Four roots representative of each cultivar were hand topped and harvested on 1 Oct. The roots were then placed in a cold room at 3deg C and 90% relative humidity until they were assayed on 7 Jan 09. The roots were washed, dipped in 0.6% sodium hypochlorite solution for 1 min, rinsed in sterile reverse osmosis water, and then air dried in a laminar hood. A cross section of the root 8-10 mm thick and 45-70 mm in diameter was cut just below the widest portion of root and placed in a Petri dish on sterile filter paper moistened with sterile tap water. A 2-mm diameter and 3-mm deep hole was created with a sterile tooth pick in the center of the root slice. A sterile tooth pick was then dipped in a48-hr old culture of Leuconostoc mesenteroides subsp. dextranicum B322 grown on MRS media at 30deg C and placed in the hole along with a drop of sterile tap water. Four additional root slices served as the non-inoculated check (no bacteria inoculated).The root slice/Petri dish combination was placed in a plastic bag and incubated at 30deg C. The experiment was a randomized complete block design with four replications (1 root slice = 1 replication for each cultivar). The diameter of rotted root area was recorded after 72, 96, and 120 hr. Bacteria from the lesions in each replication were re-isolated by streaking onto MRS to prove only L. mesenteroides was present. Data were analyzed using the general linear models procedure (Proc GLM-SAS), and Fisher’s protected least significant difference was used for mean comparisons.