ISHS Acta Horticulturae 538: Eucarpia symposium on Fruit Breeding and Genetics
DIFFERENT GROWTH HABITS IN APPLE AND CORRELATION BETWEEN GROWTH CHARACTERISTICS IN PROGENIES WITH A COMMON CO-GENE PARENT |
| Authors: | I. De Wit, E. Pauwels, J. Keulemans |
| Keywords: | prolepsis, syllepsis, apical dominance, apical control, acrotony, apple |
| Abstract:
Tree architecture is important in terms of production efficiency and pruning aspects. Since the natural tree habit is under genetic control, it is important to select suitable parents in a breeding programme. The aim of this work is to investigate the genetic control and physiology of both growth habit and vigour. Different growth characteristics of 3 different populations were measured at the end of the second growing season. These families had a common mother, ‘Telamon’ with its columnar (Co) gene, and three different fathers, ‘Braeburn’, ‘Sunrise’ and ‘Clone No. 110’, each chosen for their specific growth habit, normal, slender and columnar respectively. Only the growth characteristics, which are involved in apical dominance and apical control, are presented here. Both are important mechanisms in the control of tree architecture. The percentage of syllepsis is correlated with the level of apical dominance. The level of apical control can be expressed as the percentage of proleptic shoots. There is a greater percentage of sylleptic shoots originating in the first growing year than in the second one. Not only growth habit but also the parents affected the percentage of syllepsis, each year. It has been observed that columnar trees show less syllepsis than normal trees and the ‘Telamon’ x ‘Braeburn’ family possesses the greatest percentage of sylleptic shoots which suggests the lowest apical dominance. The percentage of proleptic shoots is not influenced by the parents but only by the growth habit; the columnar trees have less proleptic shoots than the normal trees. But a correlation between the percentage proleptic and sylleptic shoots is not found within each progeny. Only in the ‘Telamon’ x ‘Braeburn’ population, a negative correlation was detected, the other progenies didn’t show a significant correlation. The change in length of distal proleptic shoots according to their position is an expression of acrotony. The level of acrotony seems to be dependent on the progeny and the growth habit. It seems that trees with a normal growth habit always have a greater acrotony than columnar trees. | |
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