RELATIONSHIP OF FLOWERING TIME, RATE OF SEED-GERMINATION, AND TIME OF LEAF BUDBREAK AND USEFULNESS IN SELECTING FOR LATE-FLOWERING APPLES

The relationship between dormancy of seeds and buds of apple (Malus x domestica Borkh.) might provide breeders with an early opportunity to select for delayed development. Seeds of late-flowering genotypes require much longer exposure to chilling temperatures than those of early flowering genotypes, and they germinate over a much longer period. In three progenies that exhibit much variation for the two traits, seed germination time was correlated with time of leafing-out of the resulting seedlings, and could be used to select for delayed budbreak. However, selection would be ineffective when little genetic variation for seed germination and budbreak is present. Leafing-out ratings in the nursery in the 2nd year were highly correlated with those in the 3rd year, indicating that selection for late leafing in the nursery during the 2nd year would be more effective than selection based on seed dormancy, especially in progenies exhibiting little genetic variability for this trait. Breeders can effectively use both relationships by first eliminating early germinating seeds and then eliminating early leafing seedlings.