Thirty-one sugar beet germplasm breeding lines and releases produced by the USDA-ARS sugarbeet
program at Salinas, CA, and one line from the USDA-ARS sugarbeet program at East Lansing, MI, were
evaluated for resistance to rhizomania under south-central Idaho conditions at Twin Falls, ID. The field had been
identified as having Beet necrotic yellow vein virus (BNYVV), which overcomes resistance conditioned by the
Rzl gene. Single-row plots 10 ft long with 22-in. spacing were planted on 23 May 05. Plants were thinned to 4 to
6-in. spacing in mid-Jun. The materials were predominantly multigerm; they were hand thinned to single plants
during the first week of Jul. The trial layout was a randomized complete block with eight replicates, however, the
blocks were divided into 16 sub-blocks of six rows in which single-row plots of two entries and four control lines
were randomized. The control lines were Beta443OR (Rzl gene), GO17R (Rz2 gene), Angelina (Rzl+Rz2 genes)
and Beta6600 (no resistance to rhizomania). This allowed each entry plot to have its own control (Local Control).
This was necessary given the uneven distribution in the field of resistance breaking strains of BNYVV. Naturally
occurring Curly top virus infection was found throughout the field early in the season. Many plants of the
rhizomania susceptible control were killed apparently by curly top and therefore this should be considered when
evaluating the results. Plants were scored 19 Sep for curly top using a 0-9 scale with 0 showing no symptoms and
9 being dead. Plants were topped, roots lifted then scored on 12-13 Oct. Four teams evaluated the trial for
rhizomania with each team rating two replicates. Each root was scored based on the traditional 0 to 6 scale which
was converted to a 0 to 9 scale. The categories were 0, 1, 3, 5, 6, 7 and 9 with 0-3 being resistant, 5-7 susceptible
and 9 was dead. The average disease severity was determined to create a disease index (DI) for each entry and
control. A second index (DI2) was calculated for each entry-plot to evaluate the entry relative to the mean of the
Rz2 and Rzl+Rz2 Local Controls (DI of entry/mean DI of the Rz2 and Rzl+Rz2 Local Controls). The percent
healthy roots (categories 0-3 combined) and the percent of healthy roots relative to Rz2 and Rzl+Rz2 Local
Controls were calculated (PR and PR2, respectively). The DI and DI2 were transformed with the inverse square root
and analyzed using PROC MIXED - SAS with Dunnett's test (P = 0.05) option and PROC GLM – SAS with
Fisher's protected LSD test (P = 0.05) option, respectively. PR and PR2 were analyzed with PROC GLM –SAS
using Dunnett's test (P = 0.05) and Fisher's protected LSD (P = 0.05) test, respectively. The analysis of variance
of DI2 showed that block effects were significant, therefore Spearman's partial correlation (PROC CORR
Spearman partial - SAS) was used to analyze the relationship of D1, PR, DI2, PR2, and curly top. PROC CORR
Spearman -SAS was used to analyze the relationship between DI and DI2
