For four years a process for the improvement of alfalfa of the "Tierra de Campos" ecotype was carried out, selecting on the one hand plants suitable for harvesting and on the other hand plants suitable for grazing. A new selection was then made of the plants selected, seeking the homozygotic ones for different alleles of the locus Pgi‑2. These homozygotic groups can be used as mother plants for obtaining future synthetic varieties and would incorporate a kind of identification that would differentiate them from the other extant commercial varieties which would be polymorphic for this isozyme. With this type of selection we avoid problems in the identification of a new variety. Analysis of the more relevant physiological and morphological characteristics of alfalfa confirmed that this type of homogenization does not have a negative effect on cultivation.