Analysis of a Database of DNA Profiles of 734 Hybrid Tea Rose Varieties

Over 10,000 Hybrid Tea rose varieties have been described. The large number of varieties and the size of the reference collections may cause problems in DUS (Distinctiveness, Uniformity, and Stability) testing. Molecular markers may help to solve these problems by providing high power to identify and recognise seedlingderived varieties based on unique genotypes, while grouping mutants into groups with identical marker scores. Here we describe the use of a set of 11 rose microsatellite markers to generate a database of molecular profiles of Hybrid Tea varieties. The data were analysed with respect to reproducibility, discriminative power, genetic (sub) structure, and correlation between molecular and DUS characteristics. The use of the markers in the DUS context is discussed with respect to the options 2 and 3 as they were formulated by the UPOV-BMT working group. It is concluded that an option 3 approach (granting of PBR based on distinctness observed with molecular markers) is feasible for rose. INTRODUCTION The first Hybrid Tea rose was introduced in 1867 and since then more than 10,000 Hybrid Teas have entered the market. The large number of varieties may cause problems in distinctness, uniformity and stability (DUS) testing. One problem is the requirement to compare new varieties to all other varieties in common knowledge. Clearly, strict adherence to this concept is logistically and financially impossible, and DUS testing stations take a somewhat pragmatic view of common knowledge, limiting it to, e.g., varieties that can be grown in similar climatic zones. Nevertheless, this still means that many hundreds of rose varieties may have to be taken into account. Another problem is the reference collection. Maintaining a collection of greenhouse-grown roses is impractical because of the high costs and the occurrence of diseases. This is also the case for garden roses. When maintaining a collection is abandoned, the examination offices need to request reference varieties from the breeders. It is important that the identity of the material submitted can be verified. For this aspect of quality assurance molecular markers are ideally suited, as they are highly discriminating and can be assayed rapidly. A different use of molecular markers is for granting Plant Breeders Rights (PBR). This issue is heavily debated. Within UPOV the Biochemical and Molecular Techniques Working Group (UPOV-BMT) was set up to examine some of the issues related to the introduction of molecular markers in DUS testing. Three options are being considered (Button, 2006). Option 1 is the use of molecular characteristics as a predictor of traditional characteristics. It has two variants: (a) the use of molecular characteristics which are directly linked to traditional characteristics (gene specific markers), and (b) the use of a set of molecular characteristics which can be used reliably to estimate traditional characteristics; e.g. quantitative trait loci. Option 2 concerns the calibration of threshold levels for molecular characteristics against the minimum distance between two varieties for traditional characteristics. Option 3 is the development of a new system based on molecular markers. In this approach clearly distinguishable differences based on molecular characteristics would be considered as threshold levels for judging distinctness.