USDA-ARS plant introduction lines evaluated for rhizomania and storage rot resistance in Idaho, 2020

Authors: Dorn, Kevin; Strausbaugh, Carl

Submitted to: Plant Disease Management Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/18/2021
Publication Date: 8/16/2021
Citation: Dorn, K.M., Strausbaugh, C.A. 2021. USDA-ARS plant introduction lines evaluated for rhizomania and storage rot resistance in Idaho, 2020. Plant Disease Management Reports. 15. Article eV165.

Interpretive Summary: Thirty sugar beet USDA-ARS Plant Introduction lines and five check cultivars were screened for resistance to Beet necrotic yellow vein virus (BNYVV) (rhizomania) and storage rot at the USDA-ARS North Farm in Kimberly, ID using naturally infected field. The plots were rated for rhizomania, and foliar symptom (percentage of plants with yellow, stunted, upright leaves) was assessed on 24 Aug. At harvest, ten roots per plot were rated for rhizomania symptom development using a scale of 0 to 9 and samples selected for cold storage. After 131 days in storage, the roots were evaluated for the percentage of root surface area covered by fungal growth or rot. We found that a line with two genes had better resistance (resistant check 3 ) with only 1% foliar symptoms and a low root rating. Single gene resistance was less effective with Checks 2 and 4 having foliar ratings from 8 to 13%, but good root ratings. Ten entries (2, 3, 4, 12, 15, 22, 27, 28, 29, and 30) had BNYVV resistance similar to at least one of the resistant checks based on root ratings. Four entries performed well for all three variables and may serve as a starting point for identifying additional sources of resistance to BNYVV and storage rots.

Technical Abstract: Thirty sugar beet (Beta vulgaris L.) USDA-ARS Plant Introduction (PI) lines 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 which has Portneuf silt loam soil and had been in barley in 2019. In the spring the field was plowed and fertilized (110 lb N and 120 lb P2O5/A) and roller harrowed on 27 Mar 20. The germplasm was planted (density of 51,840 seeds/A) on 20 Apr. 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 crop was managed according to standard cultural practices for southern Idaho. 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 24 Aug. The plants were mechanically topped and hand harvested on 13-14 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; Plant Disease 93:632-638), with disease index (DI) treated as a continuous variable. 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 15 Oct. On 22 Feb 21, after 131 days in storage, the roots were evaluated for the percentage of root surface area covered by fungal growth or rot. Data were analyzed in SAS (Ver. 9.4) 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, but the non-transformed means have been presented in the table. Rhizomania symptom development was uniform and other disease problems were not evident in the plot area. The stand for four lines (6, 19, 20, and 21) was poor to non-existent. Thus only 26 PI lines were included in the table. The BNYVV susceptible check plots (Check 1 and Red beet) had 100% foliar symptoms and high root disease ratings. Resistant check 3 had 1% 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 8 to 13% indicating single gene resistance is not completely effective, but the root ratings were still good. Ten entries (2, 3, 4, 12, 15, 22, 27, 28, 29, and 30) had a level of BNYVV resistance similar to at least one of the resistant checks based on root ratings. Entry 11 was highly susceptible with a root rating worse than the sugar beet susceptible check. A number of the entries had resistance to fungal rots in storage, but only entry 4 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.