ISHS Acta Horticulturae 279: III International Workshop on Temperate Zone Fruits in the Tropics and Subtropics
ADAPTATIONS OF APPLE TO TROPICAL GROWING CONDITIONS |
| Author: | E.W.M. Verheij |
| Abstract:
The apple, a tree of the high latitudes, reverts to a shrub when grown unattended in the tropics. It seems that as the distance between apex and root system increases, the feed-back control between shoot and root fades out, after which vigorous new ground shoots take over. This habit of growth is typical for shrubs. Apples in the tropics contain few if any seeds. Cross-pollination appears not to be necessary; in warm, sunny conditions pollen may be shed before the flowers open. Both shrub habit and cleistogamy are more pronounced for ill-adapted (high-chilling) cultivars; 'Anna', a better adapted (low-chilling) cv for instance, branches more easily and does require cross-pollination for good fruit set. The production of 2 crops per tree per year in East Java may be made possible by the use of an unidentified low-chilling 'Chinese crab apple' as a rootstock. When grown on its own, this stock has numerous actively growing shoots almost all the time. Propagation and rooting of this stock in vitro look promising; production of virus-free material is underway. Pomologists can learn from apple growing in the tropics: close observation of the phenology of apple plants in the tropics, including growth habit, pollination and rootstock effects, reveals unexpected modes of growth, flowering and fruiting and throws new light on the adaptability of the apple. | |
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