Using grafted vegetables to increase tolerance to salt and toxic elements

Semi-arid and arid regions are characterized by water scarcity and long dry summers. To ensure continued food supply and to combat desertification in these regions, marginal waters such as saline water and treated domestic sewage (effluent) are increasingly used for irrigation. These conditions may decrease plant growth and fruit yields of vegetables, which are relatively sensitive to environmental stress, and increase the accumulation in plant shoots of toxic elements which could enter the human food supply. In addition, the use of highly saline water for irrigation may increase the susceptibility of plants to soil and airborne pathogens. Experiments conducted in the field and in greenhouses show that grafting, a horticultural technique whereby tissues from one plant are inserted into those of another so that the two sets of vascular tissues may join, in general increases the tolerance of vegetable plants to salinity, high concentrations of toxic elements, and soilborne diseases. Moreover, the concentrations of toxic elements, such as B, Zn, Sr, Mn, Cu, Ti, Cr, Ni, Cd, and Na are lower in the tissues of grafted than in those of nongrafted plants. This difference is most likely a result of exclusion of toxic elements by the rootstock of the grafted plants. It is suggested that grafting could be a useful tool to increase the tolerance of vegetable plants to salt, toxic elements, and soilborne diseases, and to prevent the entry of contaminants and saline elements into the human food supply under arid and semi-arid conditions.