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ISHS Acta Horticulturae 732: VIII International Symposium on Canopy, Rootstocks and Environmental Physiology in Orchard Systems

CAN FRUIT SIZE AND COLOURING OF 'JONAGOLD' BE IMPROVED BY AN INTERSTOCK?

Authors:   J. Vercammen, G. van Daele, A. Gomand
Keywords:   interstock, M.27, Granny Smith, Delcorf and M.9
DOI:   10.17660/ActaHortic.2007.732.20
Abstract:
For most fruit growers, the ideal tree is one that does not grow too vigorously, demands little labour and produces a good yield of high quality fruits every year. For Belgian apple growers, this mainly means a tree on M.9, a moderately vigorous interstock. Although in most cases M.9 is satisfactory, in some circumstances trees with less vigour are needed. Furthermore, the colouring is not always as good as it should be and recently, we have observed that ‘Jonagold’ is often too large when grown on M.9. In many cases, a tree with vigour between that of M.9 and M.27 is needed. One way to achieve this is the use of M.27 as an interstock, in the hope that the advantages of M.9 (yield and size) and of M.27 (colouring and labour) will be found in the interstock tree. However, from our experiments it appears that the use of M.27 as an interstock holds too many risks to be advisable. In some cases, the vigour is even less than when M.27 is used as a rootstock. The interstock trees have a tendency to cease growth after 4 to 5 years, which causes the fruits to remain too small and the colouring to diminish year after year. Another possibility is the use of ‘Granny Smith’ or ‘Delcorf’ as an interstock. Both interstocks provide a clear growth reduction, without influencing the yields too much. Because of this, the production efficiency is even better than with the “knipbomen” (trees with a two-year-old trunk and a one-year-old head) on M.9. An additional advantage is the fact that the average fruits weigh 20 to 25 grams less. On the other hand, the fruits do not colour any sooner and the percentage of A2++ does not increase compared with the “knipbomen”. However, since the fruit size is considerably smaller, the number of kilos of A2++ in the 70-85 mm size class is clearly bigger than in case of the knipbomen. If the results are confirmed in the following years, both interstocks could be interesting alternatives.

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