Kimberly sugar beet germplasm evaluated for rhizomania and storage rot resistance in Idaho, 2019

Authors: Eujayl, Imad; Strausbaugh, Carl

Submitted to: Plant Disease Management Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/8/2020
Publication Date: 8/25/2020
Citation: Eujayl, I.A., Strausbaugh, C.A. 2020. Kimberly sugar beet germplasm evaluated for rhizomania and storage rot resistance in Idaho, 2019. Plant Disease Management Reports. 14:V139.

Interpretive Summary: Rhizomania, caused by Beet necrotic yellow vein virus (BNYVV), is an important viral disease problem worldwide, leading to significant yield loss in both the field and storage. Preventing rot and sucrose losses in storage is important to the economic viability of the sugar beet industry. The primary means of controlling these problems is through host resistance. Thus, eight Beta vulgaris germplasm lines from the USDA-ARS Kimberly sugar beet program and five check cultivars were screened to characterize them for both resistance to BNYVV and storability. Three entries had resistance to fungal rots in storage, but only the KEMS8 entry performed well for both storage and the foliar RZ rating. These three entries will serve as genetic sources for identifying additional resistance to BNYVV and storage rots, which will aid the sugar beet industry in improving sucrose yield and retention in commercial sugar beet cultivars.

Technical Abstract: Rhizomania caused by Beet necrotic yellow vein virus (BNYVV) and storage losses are serious sugar beet production problems. To identify sugar beet germplasm lines with resistance to BNYVV and storage rots, eight Beta vulgaris lines and five check cultivars were screened. The lines were grown in a sugar beet field infested with BNYVV during the 2019 growing season in a randomized complete block design with 6 replications. At harvest on 16 October 2019, roots were dug and evaluated for rhizomania symptoms and then placed in an indoor commercial sugar beet storage building. After 129 days in storage, samples were evaluated for the percentage of root surface area covered by fungal growth or rot. Rhizomania symptom development in the field was uniform and other disease problems were not evident in the plot area. The BNYVV susceptible sugar and red beet checks both had 100% foliar symptoms and a high root disease severity rating. The resistant check with two resistance genes, Rz1 + Rz2 (check 3), had no foliar symptoms and low root rating. The resistant checks with only one resistance gene had foliar symptoms ranging from 14 to 24%, but their root ratings were still within an acceptable range. Foliar symptoms indicate single gene resistance for BNYVV is becoming marginal. Based on foliar ratings, entry 6 (KEMS8) seemed healthy, but root ratings from this entry were significantly worse than the resistant checks. Entry 6 will be investigated further to make sure the root rating was an indication of susceptibility and not just poor root shape. These observations suggest that both foliar and root ratings should be utilized when considering resistance to BNYVV, since relying on just one type of rating may be misleading. Three entries (1, 2, and 6) had resistance to fungal rots in storage, but only entry 6 performed well for both storage and the foliar RZ rating. These three entries will serve as genetic sources for identifying additional resistance to BNYVV and storage rots.