Rhizomania and storage rot resistance in USDA-ARS plant introduction lines evaluated in Idaho, 2018

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, 30 USDA-ARS Beta vulgaris Plant Introduction (PI) Lines and four check cultivars were screened. The lines were grown in a sugar beet field infested with BNYVV during the 2018 growing season in a randomized complete block design with 6 replications. At harvest on 15 October 2018, roots were dug and evaluated for rhizomania symptoms and also placed in an indoor commercial sugar beet storage building. After 119 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 check had 97% foliar symptoms and a high root disease severity rating. The three resistant checks had 0 to 6% foliar symptoms and the lowest root ratings. Based on root ratings, only 2 PI Line entries were not significantly more susceptible than the resistant checks and most lines were not different from the susceptible check. However, entry 3 (Ames 8447) was the only entry that had both a low foliar rating and was also among the lowest for storage rot. The root rating for entry 3 may have been affected by poor inherent root shape and may not necessarily represent a lack of resistance to BNYVV. The foliar rating and resistance to storage rot both suggest entry 3 should be reevaluated for resistance to BNYVV. Entry 3 may serve as a starting point for identifying additional sources of resistance to BNYVV and storage rots