Fig. 3

PCA biplot (a) with clusters delimitation (solid black lines and italics numbers); the barycenter of the supplementary variables most contributing to cluster variances are highlighted with colors (2018, orange; 2019, green; Se0, red; Se60, blu) and symbols (Cappelli, circle; Marco Aurelio, triangle). The other supplementary variables are reported in grey. Boxplots of distributions of yield (b) and grain protein concentration (c) resulting from the cluster analysis. Symbols and colors of boxplot charts reflect the visuals used in the PCA biplot