Rootstock Breeding between Site Adaptation and Abiotic Stress Tolerance

The introduction of rootstocks marks the first biologic pest control and at the same time the beginning of modern viticulture. Since then problems with unsuitable soil conditions may be overcome by using better adapted rootstocks. Despite this option, the number of rootstocks is still rather small and world-wide about half a dozen rootstocks are planted on approximately 60% of all sites. New soil born pests or diseases adapted to them could spread easily, repeating the phylloxera disaster. To overcome this threat more genetic rootstock diversity is needed. This task requires more new rootstocks, but also more knowledge about site adaptation of new and already existing varieties. Rootstock trials take 10 to 20 years and should be conducted on typical sites and usually private vineyards. This results in a number of restrictions regarding block size, replicates, number and kind of rootstocks being used. Despite these restrictions, such trials still provide valuable information on rootstock characteristics and site suitability. Results indicate that both already existing underutilized rootstocks, as well as recently developed hybrids with a complete phylloxera resistance mechanism, are suitable on many locations in Germany and provide the chance to enlarge genetic diversity in rootstocks and utilize site potential by better adapted rootstocks.