Periodicity analysis of VicTR-A repeats in Vicia narbonensis and Vicia pannonica. The nucleotide autocorrelation analysis of VicTR-A sequences from V. narbonensis (A) and V. pannonica (B), measuring the excess of pairs of identical nucleotides at various distances (2–500 base pairs). Sequence periodicity was calculated for a distance of k base pairs and nucleotide X as a difference CXX(k) = pXX(k)-pX.pX, where pXX is the observed frequency of identical nucleotides X and pX is the proportion of nucleotide X in the sequence [26, 27]. The periodicity is revealed as regularly spaced peaks. The results combining periodicities of all four nucleotides are shown.