Inhibition of senescence of plants increases their resistance to necrotrophic pathogens and to many abiotic stresses. Tomato plants regenerated from tumors induced by Agrobacterium tumefaciens T37 strain showed higher degree of tolerance to Phytophthora infestans infection. As regards the mechanism of the enhanced resistance to necrosis, increased phospholipid and galactolipid contents, in addition to decreased free sterols in the transformed plants gave greater stability to their membranes as compared to membranes from control plants. In addition, the elevated activity of some antioxidant enzymes such as superoxide dismutase and catalase in transformed tissues can also play a significant role in the tolerance to pathogenic and abiotic stresses