© 2006 Heron Publishing—Victoria, Canada
Vigor-controlling rootstocks affect early shoot growth and leaf area development of kiwifruit
Michael J. Clearwater (1, 2), Alla N. Seleznyova (3), T. Grant Thorp (4), Peter Blattmann (1), Andrew M. Barnett (1), Russell G. Lowe (1) and Paul T. Austin (3)
1. Horticulture and Food Research Institute of New Zealand, Te Puke Research Center, RD 2 Te Puke, New Zealand / 2. Corresponding author (mclearwater@hortresearch.co.nz) / 3. Horticulture and Food Research Institute of New Zealand, Private Bag 11030, Palmerston North, New Zealand
/ 4. Horticulture and Food Research Institute of New Zealand, Private Bag 92169, Auckland, New Zealand / Received May 13, 2005; accepted July 8, 2005; published online January 15, 2006
Summary
Patterns of shoot development and the production of different types of shoots were compared with scion leaf area index (LAI)
to identify how eight clonal Actinidia rootstocks influence scion development. Rootstocks selected from seven Actinidia species (A. chrysantha Merri., A. deliciosa (A. Chev.) C. F. Liang et A.R. Ferguson, A. eriantha Benth., A. hemsleyana Dunn, A. kolomikta (Maxim. et Rupr.) Maxim., A. kolomikta C.F. Liang and A. polygama (Sieb. et Zucc.) Maxim.) were grafted with the scion Actinidia chinensis Planch. var. chinensis ‘Hort16A’ (yellow kiwifruit). Based on an earlier architectural analysis of A. chinensis, axillary shoot types produced by the scion were classified as short, medium or long. Short and medium shoots produced a
restricted number of preformed leaves before the shoot apex ceased growth and aborted, resulting in a ‘terminated’ shoot.
The apex of long shoots continued growth and produced more nodes throughout the growing seasons. Mid-season LAI of the scion
was related to the proportion of shoots that ceased growth early in the season. Scions on low-vigor rootstocks had 50% or
less leaf area than scions on the most vigorous rootstocks and had a higher proportion of short and medium shoots. On low-vigor
rootstocks, a higher proportion of short shoots was retained during pruning to form the parent structure of the following
year. Short parent shoots produced a higher proportion of short daughter shoots than long parent shoots, thus reinforcing
the effect of the low-vigor rootstocks. However, overall effects of rootstock on shoot development were consistent regardless
of parent shoot type and nodal position within the parent shoot. Slower-growing shoots were more likely to terminate and scions
on low-vigor rootstocks produced a higher proportion of slow-growing shoots. Shoot termination also occurred earlier on low-vigor
rootstocks. The slower growth of terminating shoots was detectable from about 20 days after bud burst. Removal of a proportion
of shoots at the end of bud burst increased the growth rate and decreased the frequency of termination of the remaining shoots
on all rootstocks, indicating that the fate of a shoot was linked to competitive interactions among shoots during initial
growth immediately after bud burst. Rootstock influenced the process of shoot termination independently of its effect on final
leaf size. Scions on low-vigor rootstocks had a higher proportion of short shoots and short shoots on all rootstocks had smaller
final leaf sizes at equivalent nodes than medium or long shoots. Only later in the development of long shoots was final leaf
size directly related to rootstock, with smaller leaves on low-vigor rootstocks. Thus, the most important effect of these
Actinidia rootstocks on scion development occurred during the initial period of shoot growth immediately after bud burst.
Keywords:
Actinidia, architecture, shoot development, shoot termination.
