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The importance of healthy grapevine propagation material is known at least since Roman times (Schöffling & Stellmach, 1993). The cause of degeneration was not known, but its effect on vine performance. Consequently, health state of plants was determined by their performance. Despite the fact that no written records exist, some kind of selection was certainly going on over centuries. Modern clonal selection commenced with Gustav Fröhlich in 1876 (Fröhlich, 1900). He assessed the performance of Silvaner vines over several years and only propagated the vine with the highest yield. Over the following years his idea of using yield as the major parameter for vine performance and health status was complemented by other German researchers resulting in a distinct clone assessment system implementing three successive steps. This system proved to be such effective that since the mid-1950s virtually only clonal material is used in Germany. This may appear surprising as the role of virus infection in plants was only established when Stanley detected tobacco mosaic virus (Stanley, 1935). Over the next decades a number of viruses were identified as the cause of degeneration in grapevines (Table 1).With the development of ELISA and more recently PCR assays for their identification, the production of virus-tested propagation material is no longer guess-work and requires years of visual evaluation, indexing and performance trials in the field. Virus infection can reduce both yield and vine quality significantly (Walter & Martelli, 1996; Walter & Martelli, 1997) (Ipachn 2004). Consequently virus-free propagation material is a key to productive vineyards and a competitive wine industry. The aim of this paper is to summarize research in the development of pathogen-free grapevine clonal material and to present the Geisenheim approach as an example for a clonal selection program.

The importance of pathogen-free grapevine propagation material in regards to clonal selection and rootstock breeding in Germany