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 Diseas

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

Commercial 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 the growing region. Cultivars varied significantly in their symptoms of Verticillium wilt but no differences were recorded for any yield parameter. Root shape and root hair proliferation indicated 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 yield parameters. 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 = 0.9443, 0.7497, and 0.9548, respectively). Good resistance to V. dahliae exists in some commercial cultivars based on the reduction in foliar symptoms

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

Transgenic (resistant to glyphosate) 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 except for herbicide applications. Transgenic cultivars were sprayed with broadcast applications of glyphosate at 32 fl oz/A on 30 May and 22 fl oz/A on 27 Jun. The study area was also hand weeded to keep all plots free of weeds. 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 field were below normal for this growing region. Verticillium dahliae symptoms and yield parameters varied significantly between cultivars. Root shape and root hair proliferation indicated that Beet necrotic yellow vein virus (BNYVV) also was 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 in this field. Based on Spearman's rank correlation coefficient, the mean values for leaf symptoms were inversely related with those for root yield (r = -0.3667, P = 0.0504) but not sugar content or estimated recoverable sugar (P = 0.1277 and 0.2182, respectively). Good resistance to V. dahliae exists in some transgenic cultivars based on the reduction in foliar symptoms. Numerous transgenic cultivars with resistance to both V. dahliae and BNYVV had better yield parameters than the commercial check cultivars indicating growers should be able to switch to some of the resistant transgenic cultivars without experiencing yield loss

Evaluation of commercial sugarbeet hybrids for resistance to beet curly top in Canyon County, ID, 2004

The experiment was conducted in a commercial sprinkler-irrigated sugarbeet field near Nampa, ID in an area where Beet curly top virus had been a problem in previous years. The field trial relied on natural infection and was planted on 19 Mar. The plots were planted to a density of 190,000 seeds/A, and thinned to 35,640 plants/A. Plots were four rows wide (22 in-row spacing) and 36 ft long. The experimental design was a randomized complete block with eight replications. The crop was managed by the grower according to standard cultural practices. The weather during the growing season was cooler than normal. Disease data were recorded on 14 Sept by three raters using a disease index of 0 to 9 (no symptoms to dead). The three ratings per plot were averaged prior to analysis. The center two rows were harvested on 20 Oct using a small plot harvester. The sugar content of the beets was determined by the Amalgamated Sugar Co. laboratory, and the recoverable sugar (lb/A) was estimated. Data were analyzed using the general linear models procedure (Proc GLM-SAS), and Fisher's Protected LSD was used for mean comparisons. Yields were above average and disease pressure was uniform and moderately severe. The commercial hybrids response to Beet curly top virus ranged from acceptable (slight leaf curl to most leaves with moderate curling) to severely affected (most larger leaves becoming prostrate). Analysis of variance indicated there were significant differences among hybrids for diseases index, root yield, sugar content, and estimated recoverable sugar. Our disease ratings positively correlated (r s = 0.913, P < 0.0001) with those from the 04 Curly Top Nursery in Kimberly, ID. Based on Spearman's Coefficient of Rank Correlation (rs = -0.737, P < 0.0001), there was an inverse relationship between estimated recoverable sugar and disease index

Evaluation of experimental sugarbeet hybrids for resistance to beet curly top in Canyon County, ID, 2004

Experimental sugarbeet hybrids were evaluated for resistance to Beet curly top virus in a commercial sprinkler irrigated sugarbeet field near Nampa, ID where beet curly top had been a problem in previous years. The field trial relied on natural infection and was planted on 19 Mar. The plots were planted to a density of 190,000 seeds/A, and thinned to 35,640 plants/A. Plots were four rows wide (22 in -row spacing) and 36 ft long. The experimental design was a randomized complete block design with seven replications. The crop was managed by the grower according to standard cultural practices. The weather during the growing season was cooler than normal and disease pressure was uniform and moderately severe. Disease data were recorded on 14 Sept by three raters using a disease index of 0 to 9 (no symptoms to dead). The three ratings per plot were averaged prior to analysis. The center two rows were harvested on 20 Oct using a small plot harvester. The sugar content of the beets was determined by the Amalgamated Sugar Co. laboratory, and recoverable sugar (lb/A) was estimated. Data were analyzed using the general linear models procedure (Proc GLM-SAS), and Fisher's Protected LSD was used for mean comparisons. Yields were above average and disease pressure was moderately severe. The experimental hybrids response to Beet curly top virus ranged from acceptable (slight leaf curl to most leaves with moderate curling) to moderately affected (severe leaf curling). Analysis of variance indicated there were significant differences among hybrids in disease index, root yield, sugar content, and estimated recoverable sugar. Disease index for hybrids in this test were positively correlated (r s = 0.632, P < 0.0001) with ratings from the 04 Curly Top Nursery in Kimberly, ID. Based on Spearman's Coefficient of Rank Correlation (rs = -0.15, P = 0.4651), there was no correlation between estimated recoverable sugar and disease index. This lack of correlation between estimated recoverable sugar and disease index was likely not related to variation associated with the disease rating but rather due to other factors such as field and genetic variation that influenced yield. B&

Seed Transmission of the \u3ci\u3eHigh Plains virus\u3c/i\u3e in Sweet Corn

The High Plains virus (HPV), which infects corn and other cereals, was first found in 1993 in the United States. Research was initiated in 1995 to investigate the potential for seed transmission of HPV. Sweet corn seeds of various cultivars harvested in 1994 to 1996 from 13 fields and research plots in southwestern Idaho, Colorado, and Nebraska were seeded in potting mix in the greenhouse. Leaf samples collected at the three- to six-leaf stage from both symptomatic and asymptomatic plants were tested by enzyme-linked immunosorbent assay (ELISA). Of the 46,600 seeds planted, 38,473 seedlings emerged, and three tested positive by ELISA, exhibited mosaic symptoms, and had the presence of HPV confirmed by an additional test. One of the positive plants was used for successful acquisition and transmission of HPV by the wheat curl mite to Westford barley. The other two plants were used to successfully transfer HPV to other corn plants by vascular puncture inoculation of seed. These results indicate that HPV can be seed transmitted at a very low frequency in sweet corn

Managing curly top

Curly top of sugarbeets caused by Beet curly top virus (BCTV) was widespread from southeastern Oregon to southcentral Idaho in 2004. Curly top first became a serious threat to sugarbeet production in southern Idaho in 1919. By the time the first resistant variety was released in 1935, BCTV had almost eliminated the sugarbeet industry (2). Today this disease is largely managed through the use of resistant varieties. Early planting and the use of systemic insecticides (phorate, aldicarb, and imidicloprid) will also help limit curly top (1,2,4)

Influence of beet necrotic yellow vein virus on sugar beet storability

Rhizomania caused by Beet necrotic yellow vein virus (BNYVV) and storage losses are serious sugar beet production problems. To investigate the influence of BNYVV on storability, six sugar beet cultivars varying for resistance to BNYVV were grown in 2005 and 2006 in southern Idaho fields with and without BNYVV-infested soil. At harvest, samples from each cultivar were placed in an outdoor ventilated pile in Twin Falls, ID and were removed at 40-day intervals starting at the end of October. After 144 and 142 days in storage, sugar reduction across cultivars averaged 20 and 13% without and 68 and 21% with BNYVV for the 2005 and 2006 roots, respectively. In the December samplings, frozen root area was 1 and 2% without and 25 and 41% with BNYVV for the 2005 and 2006 roots, respectively. Root rot was always worse with stored roots from BYNVV-infested soil in December, January, and February samplings. Root weight loss was variable in 2005; however, in 2006, an increase in weight reduction always was associated with BNYVV-infested roots. In order to prevent losses in rhizomania-infested areas, cultivars should be selected for storability as well as rhizomania resistance

Relationship of beet curly top foliage ratings to sugar beet yield

Sugar beet (Beta vulgaris) varieties were evaluated for disease resistance to curly top to establish if disease ratings made in inoculated nurseries correlated with disease ratings and yield in sugar beet crops exposed to natural disease outbreaks. Cultivars were planted both in inoculated curly top nurseries in Kimberly, ID, and in commercial cultivar trials in irrigated fields near Ontario, OR and Nampa, ID. Plants were evaluated for curly top using a rating scale of 0 (no symptoms) to 9 (dead). Moderate disease pressure in the Ontario (mean rating = 3.8) and Nampa (mean rating = 4.1) fields resulted in significant differences for disease rating, root yield, sugar content, and estimated recoverable sugar among cultivars. Disease ratings from both commercial fields were positively correlated (r = 0.91 and 0.82, P < 0.0001) with ratings from the inoculated nurseries. In commercial fields, root yield was negatively related to disease rating (r2 = 0.47 and 0.39, P ? 0.0004). For each unit increase in disease rating (increasing susceptibility), root yield decreased 5.76 to 6.93 t/ha. Thus, curly top nurseries reliably predict curly top resistant cultivars for commercial cultivatio