Registration of Sugar Beet Germplasm R21 and R40 with Resistance to Rhizomania from Beta vulgaris subsp. maritima

Abstract

Rhizomania causes significant losses in sugar beet (Beta vulgaris L.) growing areas worldwide. Since 2003, isolates of Beet necrotic yellow vein virus (BNYVV), the causal agent of rhizomania, have been identified in the United States, Europe, and Asia that cause disease symptoms in germplasm with the Rz1 source of resistance. Durable resistance genes must be identified to protect sugar beet against current and evolving strains of the virus. This manuscript details the release and registration of sugar beet germplasm R21 (Reg No. GP‐291, PI 682085) and R40 (Reg. No. GP‐292, PI 682086) with high levels of rhizomania resistance developed and released by the USDA‐ARS at Salinas, CA, in cooperation with the Beet Sugar Development Foundation in Denver, CO. R21 and R40 are multigerm (MM), self‐sterile (Ss), open‐pollinated lines that maintain sugar and root yields under both the wild‐type (Type A) and Rz1 resistance‐breaking (Type‐A, IV) strains of BNYVV. They are products of repeated rounds of recurrent selection on enhanced, broadly based populations of >120 B. vulgaris subsp. maritima accessions (selected for rhizomania resistance) crossed with sugar beet. Allelic relationships between R21 and R40 are unknown. Each was derived from a different set of donor accessions, making it unlikely that they are the same gene. These broadly based germplasms provide useful genetic variability for continued sugar beet improvement.