Temperature and duration of bud set process. Data were observed in two sites in Italy: Cavallermaggiore (CV) and Viterbo (VT). (a) Cumulative minimum temperature (CMT) and CMT < 10°C (CMT10) were calculated from July 1st for CV (red full lines) and VT (black dotted lines). Arrows indicate the two extreme genotypes for bud set stages (date2.5 and date0.5) in CV (red) and VT (black). Dots indicate population mean in CV (red) and VT (black) for the same stages. The upper lines refer to CMT, whereas the bottom lines refer to CMT10. (b) Phenotypic variation of subproc1 and subproc2 observed in CV (white boxes) and VT (grey boxes). The parent '58-861' is indicated by blue "+", and the parent 'Poli' by green "*". The significance level of differences between the two parents for each trait is indicated as: ns, non-significant; *, P ≤ 0.05; **, P ≤ 0.01; ***, P ≤ 0.001.