New Zealand Journal of Crop and Horticultural Science abstracts
Effect of foliar-applied gibberellins and soil-applied paclobutrazol
on reproductive and vegetative growth of `Braeburn' apple trees
growing under a high-density planting system
T. KHURSHID
D. L. McNEIL
M. C. T. TROUGHT
Department of Plant Science
Lincoln University
P.O. Box 84
Canterbury, New Zealand
Abstract Five-year-old `Braeburn'/MM.106 (
Malus
domestica Borkh.) trees growing under a high-density (10 000 trees/ha)
planting system were treated with paclobutrazol (PBZ) as a soil drench at 250
mg (a.i.) per tree in August 1993. Gibberellin (GA), GA3 or GA4, was sprayed on
vegetative buds at 0, 10, or 100 ug per bud at three times between 22 November
and 22 December 1992 (before PBZ treatment), or in 1993 (after PBZ treatment).
Data on yield and yield components and vegetative growth were collected for 2
years. Time of GA application did not affect vegetative and reproductive growth
components. The total shoot number, total shoot length, and total bud number
were consistently reduced with PBZ application for 2 years of application. GA
caused a decrease in shoot number across 2 years whereas total shoot length and
total bud number were increased with GA treatment across 2 years. Fruit yield
was decreased with PBZ application by 42 and 23% across 2 years in Trial A and
by 27 and 12% across 2 years in trial B. Total fruit number per tree were
decreased with PBZ application and varied from year-to-year showing biennial
bearing (BI) patterns in both trials. PBZ plus GA reversed the PBZ effects on
fruit yield and total fruit number and reduced bienniality in trees for 2
years. GA application to the trees which had previously received PBZ was most
effective in reducing BI values. Mean fruit weight was not affected with PBZ
treatment. The deleterious effects of these two plant growth regulators were
reversed by the combined use of PBZ and GA, which provided a balanced yield and
vegetative growth and prevented the trees from going into biennial bearing. No
consistent, significant effects of GA types or GA levels or their combination
with PBZ on vegetative and reproductive growth were found. It is suggested that
PBZ and GA can be used to manipulate apple tree growth in a high-density apple
production system and their use in a cultural management system for
high-density apple orchards should be explored.
Keywords apple; Malus domestica; high-density;
paclobutrazol; GA3; GA4; plant growth regulators
New Zealand Journal of Crop and Horticultural Science, 1997, Vol. 25:
49-58
0114-0671/97/2501-0049 $2.50/0 (c) The Royal Society of New Zealand
1997
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