Author(s): Damodar Poudyala, Laxman Khatria and Ralf Uptmoora
Drought and low root zone temperature (RZT) hamper plant growth and leaf area development. Introgression lines (ILs) developed from a Solanum lycopersicum × Solanum habrochaites cross with the exotic parental line as donor were shown to significantly improve cold tolerance. The goal of the present study was to study agronomical and Physiological traits improving drought and, since adaptation to cold and drought is to some extent regulated by the same genetic mechanisms, low root zone tolerance in tomatoes. The parental lines of an IL library and ILs carrying quantitative trait loci (QTL) alleles for cold tolerance introgressed from S. habrochaites were used as plant material. The recurrent parent (RP) was grafted onto the IL (IL/RP) and self-grafted (RP/RP). Grafted plants were grown under two different RZTs (10°C and 20-26°C) and two soil moisture regimes (well-watered\ and drought stress). Agronomical and physiological parameters as green, non-green, and total leaf area, dry matter of plant parts, root to shoot ratio, osmotic adjustment, stomatal conductance, and stress tolerance index were measured and calculated. Plants grafted onto ILs produced higher total biomass and leaf area and probably regulated stomatal opening and closure more efficiently. The stm9 introgression from S. habrochaites LA1777 renders the scion more tolerant for low root-zone temperature and drought stress by a better stomatal regulation. Results confirm that an introgression of favourable genes from S. Habrochaites can improve cold and drought tolerance in grafted tomatoes and shoot turgor maintenance under root chilling is primarily a root-based trait.
