Location: Soil Management and Sugarbeet Research
Title: USDA-ARS pre-breeding germplasm evaluated for Rhizomania and storage rot resistance in Idaho, 2021Author
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Submitted to: Plant Disease Management Reports
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 5/29/2022 Publication Date: 8/9/2022 Citation: Dorn, K.M., Strausbaugh, C.A. 2022. USDA-ARS pre-breeding germplasm evaluated for Rhizomania and storage rot resistance in Idaho, 2021. Plant Disease Management Reports. 16. Article eV125. Interpretive Summary: Sugar beet production is threatened by multiple below ground pathogens. These pathogens can cause both decreases in potential yield and loss of sugar due to root rot during storage. Agricultural Research Service scientists in Fort Collins, CO and Kimberly, ID screened sugar beet germplasm produced by USDA-ARS breeding programs. Tapping into the decades of breeding done by USDA, the scientists identified four germplasm lines with good resistance to both Rhizomania and storage rot. These germplasm lines will serve as a starting point for mapping genes responsible for these traits, along with creating more tolerant elite varieties for growers. Technical Abstract: Thirty sugar beet (Beta vulgaris L.) lines from multiple USDA-ARS pre-breeding programs and five check cultivars were screened for resistance to Beet necrotic yellow vein virus (BNYVV), the causal agent of rhizomania, and to storage rot. The rhizomania evaluation was conducted at the USDA-ARS North Farm in Kimberly, ID. The plots were one row 10-ft long with 22-in. between-row spacing and arranged in a randomized complete block design with 6 replicates. The trial relied on endemic field inoculum for rhizomania and storage rot development. The plots were rated for rhizomania foliar symptom (percentage of plants with yellow, stunted, upright leaves) development on 19 Aug. The plants were mechanically topped and hand harvested on 18-19 Oct. At harvest, ten roots per plot were rated for rhizomania symptom development using a scale of 0 to 9 (0 = healthy and 9 = dead). At harvest, eight roots per plot were also placed in a mesh-onion bag and kept in an indoor commercial storage facility (temperature set point 34°F) in Paul, ID on 19 Oct. On 28 Feb 22, after 132 days in storage, the roots were evaluated for the percentage of root surface area covered by fungal growth or rot. Except for root ratings, data were analyzed in SAS using the general linear model (Proc GLM) procedure, and Fisher’s protected least significant difference (a = 0.05) was used for mean comparisons. The root ratings were rank transformed prior to analysis with the mixed linear models (Proc MIXED) procedure, but the non-transformed means have been presented. Mean separation for root ratings was based on a PDIFF comparison with a probability cutoff of 0.05. Rhizomania symptom development was uniform and other disease problems were not evident in the plot area. The BNYVV susceptible check plots (Check 1 and Red beet) had 100% foliar symptoms and high root disease ratings. Resistant check 3 had 0% foliar symptoms and a low root rating which indicates that resistance based on two genes is holding up. Single gene resistance (Checks 2 and 4) had foliar ratings ranging from 2 to 4% indicating single gene resistance is not completely effective, but the root ratings were still good. Four entries (4, 6, 8, and 10) had a level of BNYVV resistance similar to at least one of the resistant checks based on both foliar and root ratings. A number of the entries had resistance to fungal rots in storage, but only entries 4, 6, 8, and 10 performed well for all three variables. Some entries may serve as a starting point for identifying additional sources of resistance to BNYVV and storage rots. |
