ISHS Acta Horticulturae 538: Eucarpia symposium on Fruit Breeding and Genetics
BREEDING LOW-CHILL REQUIRING APPLE CULTIVARS (Malus x domestica BORKH.) IN SOUTH AFRICA |
| Authors: | I.F. Labuschagné, K. Schmidt, J.H. Louw, A. Sadie |
| Keywords: | prolonged dormancy, two-way selection, intraclass correlation coefficient. |
| Abstract:
Apple trees (Malus x domestica Borkh.) planted in the Western Cape region of South Africa develop prolonged dormancy symptoms because winters are not cold enough to satisfy chilling requirements of most commercial cultivars. A breeding program for high quality and area specific adapted apple cultivars without symptoms of prolonged dormancy was introduced in 1995 to explore the applicability of early screening to quantify chilling requirements at a young seedling stage for the purpose of selection. Broad sense heritability estimates show that approximately 30% of the total variation for number of buds sprouting, and 62% for time of bud sprouting is attributable to genetic differences between individual seedlings. Low intraclass correlation coefficients for number and time of bud sprouting between populations, indicate low variation between populations. Two-way mass selection for number of buds sprouting in one-year-old seedlings resulted in significant differences between the selection groups. Results suggest significant genetic variation within populations for chilling requirements, i.e., time and number of buds sprouting, and that young apple seedlings can be selected on an individual basis for adaptation to inadequate winter chilling conditions and for obtaining genetic improvement of the breeding stock. | |
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