Molecular genotyping of “Rizor” and “Holly” rhizomania resistances in sugar beet

Rhizomania is the most damaging and widespread disease of the sugar beet crop and is caused by Beet necrotic yellow vein virus vectored by the fungus Polymyxa betae. The only disease man- agement tool used is resistant varieties. In the last 30 years, ‘‘Rizor’’ and ‘‘Holly’’ (Rz1) resistances have been the most widely used. Despite the lack of information, a common origin for both types of resistance was hypothesized by some breeders. The aim of this study was to assess the phylogenetic relationship between Rizor and Rz1 by means of SNP analysis. Fifty leaf samples of each were genotyped with a fingerprinting panel of 192 SNPs, using the QuantStudio 12K Flex system coupled with Taqman OpenArray technology. Analysis of molecular variance and principal coordinate analysis confirmed that Rizor and Rz1 cannot be distinguished as separate sources of resistance.