An alternative strategy to increase tomato tolerance to sub-optimal temperature (T) is to develop tolerant rootstocks and graft elite cultivars onto them.To attain this goal, a better understanding of adaptive mechanisms to sub-optimal T, associated with root functions and root-signaling through hormonal messengers, is needed.In the present study, the commercial tomato cultivar Kommeet was grafted onto the tomato cv.Moneymaker (cold-sensitive) or onto the line accession LA1777 of the wild species Solanum habrochaites (cold-tolerant).