Assessment of table beet cultivars for rhizomania resistance in Michigan in field and greenhouse experiments

Rhizomania, caused by beet necrotic yellow vein virus, is a leading disease of sugar beet and is vectored by a soil-borne protist, Polymyxa betae. Since 2017, rhizomania has become increasingly important on table beet in Michigan. On table beet, rhizomania is characterized by increased proliferation of petioles causing scarring along the main taproot, elongation and constriction of the main taproot giving a “wineglass” shape, and secondary rootlet proliferation which traps soil and gives the beetroots a “bearded” appearance. With limited chemical control options, genetic resistance remains the primary method to limit rhizomania. Cultivars with marketed intermediate resistance were compared to susceptible check cultivars in replicated field and greenhouse experiments. The susceptible-check cultivars, ‘Boro’ and ‘Red Ace’, had consistently high rhizomania disease index values in two of three field studies and two of three greenhouse studies. Among the best performing cultivars in the first field trial were ‘Grenade’, ‘Manzu’, and ‘Redval’. In the second trial, ‘Bazzu’, Grenade, Manzu, ‘Power Cruz’, and ‘Rhizu’ were among the best performing cultivars. In greenhouse trials 1 and 3, Grenade had lower rhizomania disease index values compared to the susceptible check cultivars. In one of three greenhouse trials, Manzu, Bazzu, and Palau had lower rhizomania disease index values compared to the susceptible checks. Our results indicate that table beet cultivars with marketed intermediate resistance to rhizomania can be used to limit the disease in order to produce more marketable beets in Michigan.