Discriminating maize inbred lines using molecular and DUS data

To be eligible for the protection in form of the Plant Breeders’ Rights (PBR), a potential new variety must meet the criteria of Distinctness, Uniformity, and Stability (DUS). In most of the European countries, testing for DUS is, or will become, the consistent part of variety trials. It is based on a set of traits suggested by UPOV, which are traditionally, and predominantly, morphological characters that should have some agronomic relevance. Being affected by environmental factors, morphological markers require repeated testing over years. Multiplied by the growing numbers of candidate varieties, it would inevitably cause either dramatic increase of trial costs, or equal decrease of trial precision. Necessity of the cost reduction, due to general limitation of resources, raises the need for the alternative system of DUS testing. Proven to have high discriminative power, unaffected by environmental factors, molecular markers become the obvious candidates. However, they are still not widely accepted for use in DUS testing, due to non-uniformity within varieties, often observed at the molecular level. In this study total of 41 maize inbred lines were scored for 32 DUS characters prescribed by UPOV. The same set of inbred lines was genotyped at 28 SSR loci. The aim of the study is to compare the results obtained by using DUS data and SSR markers to discriminate maize inbred lines. Further comparisons will be done with available pedigree information, in order to assess power of both data types to detect the degree of relatedness between lines. We will also try to establish parallels between morphological and molecular markers, and point out morphological traits that could be associated with the variability at the molecular level. Suitability of the SSR markers for DUS testing will be reviewed from the aspects of their discriminative power, cost reduction, and others.