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Kiwiberries (Actinidia arguta ‘Hortgem Tahi’) are a convenient, grape-sized (∼ 12 g) kiwifruit with an edible skin that are easier to eat than standard kiwifruit. In this study, we examined consume...

Conventional planting and management systems for almond (Prunus dulcis (Mill.) D. A. Webb) orchards involve trees trained from an early age to produce multiple large scaffold branches, which in mature orchards form closed light inefficient canopies. Treatments included a single round of selective limb removal pruning applied at the start of the research to remove the large scaffold branches that cause shading between trees. Treatments were applied to two groups of 5-year-old ‘Nonpareil’ trees on ‘Nemaguard’ rootstock planted at 6 × 3 m spacing (556 trees/ha) in the Riverland region of South Australia. Each year, reflective ground covers were installed beneath one group of pruned trees to reflect light back into the lower canopy zones. A third group of control trees were left unpruned without reflective ground covers. Yield, kernel quality and light transmission within canopy zones were monitored for 3 subsequent years. Results demonstrated that in control trees, less than 10% of incoming sunlight was transmitted to lower canopy zones. This was insufficient to ensure cropping in these zones. Although pruning selected limbs and using reflective ground covers increased the amount of light and thus yields in the lower canopy zones, this was not sufficient to increase total tree yield nor improve kernel quality. Furthermore, the fruit in these lower zones were not ready for harvest until 2–3 weeks after the main crop.

We compared the long-term effects of whole-vine source-sink manipulation on yield, composition, and quality of fruit from mature field-grown kiwifruit (Actinidia chinensis Planch. var. chinensis) ‘Hort16A’ vines. Four contrasting source/sink-modifying treatments were applied to vines each year from Spring 2003 to 2007: 1) control—standard canopy management techniques, no trunk girdle; 2) extended trunk girdle (ETG)—girdle was opened in late summer, kept open over winter, and allowed to heal the next spring; 3) “feast”—cropload was kept low and leaf numbers kept high, no trunk girdle; and 4) “famine”—fruit numbers were kept high and vines were heavily pruned to stimulate regrowth, no trunk girdle. Fruit from the famine vines were smaller with lower dry matter concentration (DMC; dry weight as a percentage of fresh weight) and had delayed maturity relative to fruit from the control vines. Return bloom was reduced in the famine vines, resulting in ≈42% less fruit in the famine vines compared with the feast vines, and this difference remained consistent across all three seasons. Fruit from the feast treatment were larger with advanced maturity relative to fruit from control vines; there were no differences in fruit numbers in subsequent seasons. Fruit DMC was higher and maturity was advanced in the ETG vines relative to the control vines. Fruit numbers in the ETG vines consistently increased relative to the control vines each season. There were no consistent treatment effects on fruit mineral concentrations, except that fruit from the feast vines had higher nitrogen concentrations than fruit from the famine vines. Seasonal variation in the incidence of storage disorders was large; in years when disorders were present, physiological pitting incidence was higher in fruit from the treatments that advanced maturity and the incidence of low temperature breakdown was highest in treatments that delayed maturity. Although the treatments affected vine productivity, fruit DMC, and storage performance, there was no evidence of a gradual decline in quality and productivity after 4 years of treatment application.

†Background and Aims In kiwifruit (Actinidia), the number of nodes per shoot is highly variable and is influenced by genotype and environmental conditions. To understand this developmental plasticity, three key processes were studied: organogenesis by the shoot apical meristem during shoot growth; expansion of phytomers; and shoot tip abortion. †Methods Studies were made of organogenesis and shoot tip abortion using light and scanning electron microscopy. The effect of temperature on shoot growth cessation was investigated using temperature indices over the budbreak period, and patterns of shoot tip abortion were quantified using stochastic modelling. †Key Results All growing buds began organogenesis before budbreak. During shoot development, the number of phytomers initiated by the shoot apical meristem is correlated with the number of expanding phytomers and the mean internode length. Shoot tip abortion is preceded by growth cessation and is not brought about by the death of the shoot apical meristem, but occurs by tissue necrosis in the sub-apical zone. For most genotypes studied, the probability of shoot tip abortion is higher during expansion of the preformed part of the shoot. Lower temperatures during early growth result in a higher probability of shoot tip abortion. †Conclusions Organogenesis and shoot tip abortion are controlled independently. All buds have the potential to become long shoots. Conditions that increase early growth rate postpone shoot tip abortion.

We developed a framework for the quantitative description of Actinidia vine architecture, classifying shoots into three types (short, medium and long) corresponding to the modes of node number distribution and the presence/ absence of neoformed nodes. Short and medium shoots were self-terminated and had only preformed nodes. Based on the cut-off point between their two modes of node number distribution, short shoots were defined as having nine or less nodes, and medium shoots as having more than nine nodes. Long shoots were non-terminated and had a number of neoformed nodes; the total number of nodes per shoot was up to 90. Branching patterns for each parent shoot type were represented by a succession of branching zones. Probabilities of different types of axillary production (latent bud, short, medium or long shoot) and the distributions of length for each branching zone were estimated from experimental data using hidden semi-Markov chain stochastic models. Branching was acrotonic on short and medium parent shoots, with most axillary shoots being located near the shoot tip. For long parent shoots, branching was mesotonic, with most long axillary shoots being located in the transition zone between the preformed and neoformed part of the parent shoot. Although the shoot classification is based on node number distribution there was a marked difference in average (per shoot) internode length between the shoot types, with mean values of 9, 27 and 47 mm for short, medium and long shoots, respectively. Bud and shoot development is discussed in terms of environmental controls.

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 Actinidiaspecies (A. chrysanthaMerri., A. deliciosa(A. Chev.) C. F. Liang et A.R. Ferguson, A. eriantha Benth., A. hemsleyana Dunn, A. kolomikta(Maxim. et Rupr.) Maxim., A. macrosperma 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 lowvigor rootstocks produced a higher proportion of slow-growing shoots. Shoot termination also occurred earlier on lowvigor 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 influ enced 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.