The Use of Genetical Variation in Roots to Improve Productivity

Abstract

The majority of the most important fruit and nut crops and many ornamentals are still totally or partly propagated by grafting on seedling rootstocks. Genetic variation between these rootstocks can be used for selection. New propagation techniques like stenting (simultaneously cutting and grafting) and root grafting are presented here as promising tools for selecting higher yielding root systems for many crops. Some applications are presented in this paper. New rootstocks for roses with promotive effects on bottom break formation, plant architecture, productivity, flower quality or resistance to nematodes were selected. Root grafting of walnut (Juglans regia) proved to be possible. This enables rootstock selection among trees grafted on seedlings and showing rootstock induced variation. In crops where own rooted cuttings are used the plants can be considered as an unintentional compromise between the different functions of shoots and roots. Variation in root quality between cultivars of Chrysanthemum indicated that own roots are not always the best for optimal growth and quality development. In breeding programmes of vegetatively propagated crops like Chrysanthemum, root quality should be optimized.