The permanent need for efficient plant breeding comes from the increment of human population, which is projected to reach 9.7 million by 2050. Novel approaches could be used to reach these goals more rapidly, raising the question of efficiency, as well. Spike length is one of the important components of grain yield formation in wheat. The influence of individual plan traits is getting more important to grain yield formation per area unit in stressful growing conditions, which are increasingly present due to global climate changes. The objectives of the present research were three-fold: (i) to determine the influence of a genotype, environment and their interaction on spike length and to evaluate stability of the trait; (ii) to present cause-causing links on a graphical example; (iii) to transform a number of possibly correlated variables into a smaller number of uncorrelated variables called principal components. Samples were obtained from 96 winter wheat cultivars grown in 2011/12 and 2012/13 on two locations. The wheat genotype population was profiled with 28 microsatellites. The ANOVA of the total phenotypic variation of the experiment shows that genotypes took the largest portion, followed by the influence of the GE interaction. Additional analysis of the GE interaction using the PCA analysis shows a statistical significance of the first two main components. In the conducted research, the dispersion of the points represents two subpopulations, but the geographical origin could not explain the grouping of genotypes within the same, so the division into two groups was done on the basis of their lines of descent.