The presented article reflects the first part of the research paper in which an experimental analysis of the possibilities of use in Zea mays L. of some genetic models with a genome with pronounced expression of marker systems at morphological, biochemical and molecular-protein level is performed. The paper focuses on the traditional identification of maize lines with genes of endosperm structure at the level of morphological markers (according to UPOV requirements). The example of the use of a group of maize mutations with endosperm structure genes: opaque2 (o2), sugary2 (su2) and waxy1 (wx1), shows that morphological markers that are quite widely used in the assessment of varieties according to distinctiveness, uniformity and stability criteria need additional parameters, which would allow a complete and extensive marking characterization of the breeding material.