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Abstract

In commercial apple (Malus domestica Borkh.) orchards,
early cropping is a very important economic consideration. Orchard
turnover is now occurring more rapidly through the release of new
varieties and this demands the minimisation of plant establishment costs.
It has been reported that young trees with branches produce crops much
earlier than those with no branches.
A series of experiments have been conducted to explore
the factors involved in branch production, and to examine some methods
of manipulating or inducing branches in nursery and one-year-old apple
trees, particularly spur type 'Red Delicious'.
The results presented confirm that spur type Red Delicious
apple nursery trees produce very few branches when compared with
Golden Delicious and Red Fuji, on MM106 rootstocks. Chemical
treatments, of Cytolin (BA+GA₄₊₇) at 800 ppm (single application) and
four sequential applications of 200 ppm, induced lateral shoot formation
on nursery trees; but the sequential applications produced narrow branch
crotch angles. A more detailed study showed that BA is the main effective
ingredient of the mixture, when applied as a single spray.
GA₄₊₇ alone induced branching when applied in 4
sequential applications at 200 ppm, but the lateral shoots had narrow
crotch angles. The GA₄₊₇- induced branch crotch angles became wider,
while the branches were growing.
NAA at 10 ppm did not influence the Cytolin- or GA₄₊₇-
induced branch crotch angle, when applied at different periods of growth.
Cytolin was also applied to one-year-old apple orchard trees to induce lateral shoots, at lower concentrations than applied to the
nursery trees. An optimum concentration range of Cytolin concentration
of between 80 and 100 ppm is suggested. Concentrations of Cytolin were
used up to 200 ppm without phytotoxicity symptoms. The higher
concentrations resulted in excessive lateral shoot production but shoot
length was reduced.
Other growth regulators i.e. M&B 25,105, thidiazuron, or
paclobutrazol were also tested on nursery trees, but they produced
unwanted side effects without any significantly increase in the number of
lateral shoots.
Mechanical treatments i.e. the removal of young or
mature leaves, lower lateral shoots or buds did not induce any increased
lateral growth. The removal of leading shoot tips induced a cluster of
lateral shoots, immediately below the apical node but these had narrow
crotch angles.
The results are discussed in terms of the possible
relationships between the plant hormones and their influence on lateral
shoot induction. The practical considerations required to fully utilise the
spur type apple varieties' natural advantages in early cropping are also
discussed.

Item Type:	Thesis - Coursework Master
Authors/Creators:	Jarassamrit, N
Keywords:	Apples
Copyright Information:	Copyright 1989 the Author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).
Additional Information:	Includes bibliographical references (p. 173-191). Thesis (M.Agr.Sc.)--University of Tasmania, 1991
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