Identification, Distribution, and Testing for Resistance to Rhizomania in Beta maritima

Abstract

Many plants with a high level of resistance to rhizomania were found in 17 of 63 (27%) accessions of Beta maritima tested in either the greenhouse, the field, or both. Resistance to rhizomania was estimated by disease reaction or by enzyme-linked immunosorbent assay (ELISA) values for beet necrotic yellow vein virus (BNYVV) from plants that were grown in infested soil. Some resistant plants grown in the greenhouse and in the field were virus-free, as measured by ELISA. The number of plants within each accession that was free of the virus ranged from a few plants to all plants. Resistant accessions were from Denmark, England, France, and Italy. All plants tested were susceptible to the fungus Polymyxa betae, the vector of BNYVV. Successful crosses were made between sugar beet (B. vulgaris) and B. maritima. Resistance appeared to be dominant because F1 plants (resistant .times. susceptible) were all resistant or segregated for resistant plants. A significant correlation (r = 0.77) occurred between the mean greenhouse and field ELISA (BNYVV) values from 15 resistant types. Also, significant correlations based on a disease index (DI) were found among three greenhouse tests, between DIs from the greenhouse and field ELISA, and between greenhouse DIs and field root symptoms. Other correlations, greenhouse DIs versus greenhouse ELISA, greenhouse ELISA versus field DIs, and field DIs versus field ELISA, were not significant. These data suggest that plants of B. maritima with resistance to rhizomania can be selected either in the greenhouse or the field and that this resistance can be transferred to sugar beet. This is the first detailed report of rhizomania resistance in B maritima.