Verticillium wilt in experimental sugar beet cultivars in Cassia County, ID, 2006

Experimental sugar beet cultivars were evaluated in a commercial sprinkler-irrigated sugar beet field near Heyburn, ID where winter wheat was grown in 2005. The field trial relied on natural infection of Verticillium dahliae. The plots were planted on 28 Apr to a density of 142,560 seeds/A, and thinned to 47,520 plants/A on 15-20 Jun. Plots were four rows wide (22-in. row spacing) and 34.5 ft long. The experimental design was a randomized complete block design with eight replications per cultivar. The field was cultivated on 8 and 20 Jun. The crop was managed by the grower according to standard cultural practices. The percentage of plants with leaves that had dead vein delimited sectors was recorded for the center two rows on 6 Sep. The center two rows were harvested on 25-26 Sep with the aid of a mechanical topper and small plot harvester. The sugar content of the beets was determined by the Amalgamated Sugar Co. laboratory, and recoverable sugar was estimated. Data were analyzed using the general linear models procedure (Proc GLM-SAS), and Fisher's protected least significant difference was used for mean comparisons. Yields from this trial were below normal for this growing region. Cultivars varied significantly for Verticillium dahliae symptoms and sugar content but no significant differences were recorded for root yield and estimated recoverable sugar. Root shape and root hair proliferation indicated that Beet necrotic yellow vein virus (BNYVV) was also present in the field although the foliar symptoms of this disease were not particularly evident. An interaction between BNYVV and V. dahliae may have been present and interfered with establishing differences in root yield and recoverable sugar. Based on Spearman's rank correlation coefficient, the means values for leaf symptoms did not correlate with those for root yield, sugar, or estimated recoverable sugar (P = 0.3547, 0.6212, and 0.5765, respectively). Good resistance to V. dahliae exists in some experimental cultivars based on the reduction in foliar symptoms. Plant Disease