Growth, Yield, and Metabolic Responses of Temperature-stressed Tomato to Grafting onto Rootstocks Differing in Cold Tolerance

Tomato (Solanum lycopersicum cv. Kommeet) plants were either self-grafted, grafted onto the cold-sensitive cultivar Moneymaker or onto LA 1777, a cold-tolerant accession of Solanum habrochaites. Plants were grown at three different temperatures (T): optimal (19.4 degrees C), intermediate (17 degrees C), or low (14.6 degrees C). Grafting tomato 'Kommeet' onto LA 1777 increased shoot growth at intermediate and optimal T and root growth at low or intermediate T in comparison with self-grafting or grafting onto 'Moneymaker'. Reducing T significantly suppressed fruit yield as a result of reduced fruit number per plant without any interaction with grafting treatments. Grafting 'Kommeet' onto LA 1777 remarkably restricted fresh and dry fruit mass in comparison with self-grafting of 'Kommeet' as a result of a reduction in the fruit number per plant while not influencing flower number per plant and mean fruit mass, regardless of T regime. Negative effect of LA 1777 on fruit setting points to impairment of pollen fertility indicating signals originating from the root. At low and intermediate T, plants grafted onto LA 1777 were capable of increasing soluble carbohydrates, total amino acids, and guaiacol peroxidase activity in roots to higher levels than those grafted onto S. lycopersicum rootstocks while maintaining a significantly lower malondialdehyde content. These differences point to a much weaker oxidative stress in roots of plants grafted onto S. habrochaitis than those grafted onto S. lycopersicum rootstocks when exposed to low and intermediate T. Furthermore, plants grafted onto LA 1777 exhibited significantly higher levels of soluble carbohydrates, total amino acids, and guaiacol peroxidase activity in leaves and fruit and superoxide dismutase in fruit at low and intermediate T, which indicates that LA 1777 improved the level of antioxidant compounds in tomato shoots, thereby enhancing its adaptation to lower T than optimal.