Effects of root systems of tomato genotypes on growth and earliness,studied in grafting experiments at low temperature

Summary The contribution of the roots to growth and earliness of 29 genotypes of tomato cultivated under low energy conditions, was analysed in two grafting experiments.There were significant effects of the rootstocks on the vegetative growth, earliness and fruit production of the different scions, but not on plant length or number of leaves or trusses. There was hardly any interaction between rootstock and scion.The commercial rootstock KNVF and a commercial breeding line especially promoted vegetative growth of all scions, but the former delayed flowering of the scion by 6–7 days. The breeding line also stimulated early flowering. Most of the IVT breeding lines selected for growth and early production under low energy conditions scored very poorly as rootstock.Implications for breeding tomatoes with efficient root systems are discussed.