Heritability of flowering time within apple progeny

The flowering onset of 19 apple progeny was evaluated in 2005-2014 on a total number of 715 seedlings in comparison with their parents and grandparents. A very low flower set delays generally the onset of flowering by one day in comparison with a higher flower set. The maximum span between the first flowering onset and the last one within all the progeny of the study was 11 days. With one exception, the incidence of the first flowering dates of all the progeny fluctuated only within four days - April 28 and May 1. Among them, the great majority of the seedlings had the first flowering date span of not more than ± one day. The progeny of Pink Lady × Discovery was the most exceptional having the mean day on the April 17 and the span about two days longer. The means of the first flowering dates within seedling populations and corresponding dates of both their parents and grandparents were very highly correlated (r = 0.926 for parents and r = 0.877 for grandparents). The incidence of flowering onset dates in almost all progeny followed a typical Gaussian distribution, in which the majority of seedlings start flowering within 3 or 4 days. The maximum difference between both extremes (found only in one progeny) was 11 days. The share of seedlings in both extremes was, however, very small - less than 2%.