This investigation is a mimesis to what usually happens in nature, where the plants are normally exposed to sublethal environmental stresses before their exposure to the lethal level of stresses. The gradual increase of environmental stress, gives plants a suffficient time to prepare their defensive means to withstand the lethal level of stress. In order to develope a suitable screening technique, it was essential to determine the induction as well as the lethal levels of stress, as important components of such proposed tool. This technique was applied to screen some tomato genotypes, and assess the genetic variability among them, in order to evaluate their salinity stress response , and selecting the highly salt tolerant types.