Because extreme environmental events are expected to increase with climate change, identifying candidate genes for stabilizing the protein composition of legume seeds or optimizing it in a given environment becomes increasingly important. To elucidate the genetic determinants of seed protein plasticity, major seed proteins from 200 ecotypes of Medicago truncatula grown in four contrasted environments were quantified after one-dimensional electrophoresis. Major protein bands were excised from the seed protein profile of five genotypes to identify protein variants.