In Keszthely, the breeding of grass species have several decades long history. Among other things, the aim of the maintenance work of the registered varieties is to preserve the ploidy levels that have been reported in the variety descriptions. Flow cytometry is a fast, modern tool for examining plant DNA content. In our pilot study, we compared the genome size of the four grass species maintained at the MATE Georgikon Campus with the data of known samples of similar ploidy levels published for the given grass species in the international database. Our results showed a high degree of agreement with the theoretically expected values, supporting the applicability of flow cytometry in plant breeding and in variety maintenance.