The Role Root Traits Play in the Tolerance of Tomato (Lycopersicon esculentum Mill.) Plants Under Low Night Temperatures.

Cultivated tomatoes (Lycopersicon esculentum Mill.) are grown widely and stand as a classic example of a plant that evolved in cold climates, yet is cultivated in warm climate crop. Exposure to low night time temperature (LNT) can cause irreparable damages and severely inhibit the growth and development at all life stages. Due to the natural variation of tomato plants, grafting may serve as a tool to mitigate cold stress on elite tomato cultivars. In the current study we determined whether different rootstocks can alleviate the adverse effects of night cold temperature. The impact of grafting tomato (cv. Ikram) was examined at LNT (12 hours of 4C) for 10 days, using non-grafted Ikram plants as controls. Under LNT, non-grafted tomato plants had significantly lower shoot and root dry weights. Photosynthetic rates and stomatal conductance did not change significantly after LNT exposure, as opposed to a significant decrease in the non-grafted plants. Moreover, grafting rootstocks resulted in higher mass of fine and coarse roots as compared to non-grafted plants. This study illustrated that vegetative growth of tomato plants at LNT is in part inhibited by poor root development. Improvement of root traits by grafting onto a low-temperature tolerant rootstock can serve as means to reduce susceptibility of tomato plants to LNT. In addition, development of chill tolerant tomato rootstocks may widen the geographical cultivation area of tomatoes and widen the growth duration in temperate climates.