The purpose of this yearly variety trial is to test the performance of rhizomania resistant varieties under severe disease conditions. The trial was conducted at the Rupert rhizomania research farm on a field that was fallow the previous year, cropped to barley two years previous and had been cropped to sugarbeets for four years prior to the barley. The field was sprinkler irrigated with hand lines. To ensure uniform irrigation, lines are offset from the previous irrigation and end plugs are pulled following each set to allow lines to drain away from the experiment. Three years previously, in order to uniformly distribute disease inoculum and improve the sensitivity of the tests, a 6-inch soil slice had been removed from the field, mixed, redistributed onto the field and laser leveled.

Entries included 12 rhizomania test entries and 4 standard susceptible check varieties. All varieties were entered into the curly top nursery operated by the Beet Sugar Development Foundation (BSDF) to be rated for resistance to curly top virus disease. Experimental design was a randomized complete block with 8 replications. Plots were 4 rows wide by 25 ft long with a 5 ft alley between each tier. Plots were seeded with a cone planter at 8 seeds/ft on May 7, and hand thinned to an average 8 inch spacing. Plots were hand weeded and no chemical weed control was applied. Plants were machine topped and the two center rows were machine lifted on October 12-13. Two sugar samples and one tare sample per plot were analyzed at the Amalgamated Sugar company tare lab at Paul.

Disease was very uniform in the trial, and yields of the best resistant varieties were high considering the severity of disease and the abbreviated growing season. All commercial and experimental varieties tested as rhizomania resistant, with the exception of HM 2981, were significantly higher in root yield and recoverable sugar per acre than the susceptible checks. All varieties except for Beta 4006R and SX 1516 were tested under disease-free conditions in the standard variety tests. Beta 5KJ5017 and HM 2981 were equal to or higher in curly top resistance in the BSDF curly top nursery than the resistant check, US 41.

Rhizomania Resistant Transgenic Varieties

Rhizomania resistant transgenic varieties, one Liberty Linked and one Roundup Ready, were included in the rhizomania variety trial for field performance testing. Because of the restrictions prohibiting delivery of transgenic sugarbeets to Amalgamated Sugar Company's processing facilities, root samples for the transgenic varieties and two standard rhizomania resistant varieties for comparison were analyzed for tare in the field, then delivered to Betaseed Inc. for analysis of sugar content, sodium, potassium and amino nitrogen.

Beta 7CG9236LL was lower in root yield than the check variety Beta 4035R and higher in sugar content. HM 118RR was the lowest in root yield and sugar content in this comparison and appeared to have no resistance to rhizomania.