HE VARIABILITY of grain storage-proteins of twelve wheat …..genotypes under stress (Siwa Oasis) and normal (Ashmon) habitats were analyzed using sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). It was clear that small differences were found in the SDS-PAGE analysis of wheat endosperm proteins among the studied genotypes. The defense isozymes [Peroxidase (Px), Polyphenol oxidase (PPO) and Malate dehydrogenase (Mdh)] were detected and their results concluded a prominent role, either directly or indirectly in stress responses. High polymorphisms were observed in most genotypes forMdh isozymes at Siwa habitat, meanwhile Px isozymes were decreased. Misr-1 genotype attained a higher level of Px isozymes under stress habitat as a trait to tolerance response. The changes of PPO isozymes showed a good correlation with the abiotic stress tolerance of wheat genotypes. Thus, PPO increased in Nesr, S8/17, ACSAD-2, ACSAD-3 and NBL genotypes under stress condition (Siwa habitat).