2012, McFadyen, Lisa Maree, Robertson, David, Sedgley, Margaret, Kristiansen, Paul, Olesen, Trevor David

Macadamia ('Macadamia integrifolia' Maiden and Betche, 'M. tetraphylla' Johnson and hybrids) orchards in Australia are typically hedged around anthesis (September). Such hedging reduces yields, largely through competition for carbohydrates between early fruit set and the post-pruning vegetative flush, but also through a reduction in photosynthetic capacity caused by the loss of canopy. We examined whether hedging at other times might mitigate yield losses. Hedging time was found to affect yields across four cultivars: 'A4', 'A38', '344' and '816'. Yield losses were lower for trees hedged in November-December than for trees hedged in September. Yields for trees hedged in June were higher than for trees hedged in September in one experiment, but were similar in a second experiment. Yield losses for September and October hedging were similar. Hedging time changed the pattern of fluctuations in stem water-soluble carbohydrates (WSC). WSC declined shortly after hedging in September, October or November, and the declines preceded increases in fruit abscission relative to unpruned control trees. The increase in fruit abscission was less pronounced for the trees hedged in November, consistent with the idea that fruit become less sensitive to carbon limitation as they mature.

2009, Wilkie, John D, Sedgley, Margaret, Olesen, Trevor David

We examined the relationship between shoot growth and temperature and solar radiation in macadamia ('Macadamia integrifolia' Maiden and Betche, M. 'integrifolia X tetraphylla' Johnson) as an aid to developing pruning strategies for this crop. Trees growing at Alstonville (28.9°S) in northern NSW, Australia, were pruned at various times to promote vegetative flushing under a range of environmental conditions. Flush development in macadamia is cyclic: bud release and stem elongation followed by a period of dormancy, before bud release of the subsequent flush. The rate of bud release after pruning was best correlated with the product of the mean temperature and solar radiation (r² = 0.75, P < 0.0001), whereas the rate of flush development was best correlated with the mean temperature (r² = 0.76, P < 0.0001). The number of buds released per pruned stem was greater under higher temperatures and solar radiation (r² = 0.37, P < 0.001), but the length of the flush after pruning decreased with increasing temperatures (r² = 0.32, P < 0.01). The descriptive models were combined with long-term weather data to predict the duration and characteristics of flushes following pruning at various times of the year along Australia’s eastern seaboard, from Mareeba (17.0°S) to Coffs Harbour (30.38°S). Flush duration and stem length following June pruning were predicted to be greater than following early autumn or September pruning and to vary from year to year, and with location (latitude). We discuss the implications of the model predictions for productivity and propose pruning times intended to optimise flowering and yield. Further research is required to test these proposed pruning strategies.

2005, Mookerjee, Sonali, Guerin, Jenny, Collins, Graham, Ford, Chris, Sedgley, Margaret

Olive ('Olea europaea' L.) is a wind-pollinated, allogamous species that is generally not considered to be self-compatible. In addition, cross-incompatibilities exist between cultivars that can result in low fruit set if compatible pollinisers are not planted nearby. In this study, microsatellite markers were used to identify 17 genotypes that were potential pollen donors in a commercial olive orchard. DNA typing with the same primers was also applied to 800 olive embryos collected from five cultivars in the grove over 2 years of study. Pollen donors for the cultivars Barnea, Corregiola, Kalamata, Koroneiki, and Mission were estimated by paternity analysis, based on the parental contribution of alleles in the genotypes of the embryos. The exclusion probability for the marker set was 0.998 and paternity was assigned on the basis of the ‘most likely method’. Different pollen donors were identified for each of the maternal cultivars indicating that cross-compatibilities and incompatibilities varied between the genotypes studied. Cross-pollination was the principal method of fertilization, as selfing was only observed in two of the embryos studied and both of these were from the cultivar Mission. This is the first report where these techniques have been applied to survey the pollination patterns in an olive grove. The results indicate that careful planning in orchard design is required for efficient pollination between olive cultivars.

2012, Seifi, E, Guerin, J, Kaiser, B, Sedgley, Margaret

Paternity analysis was used to assess the self-incompatibility of the olive ('Olea europaea' L.) cultivar 'Kalamata' and to identify some compatible pollenisers under a Mediterranean-type climate. Eight microsatellite markers were used for genotyping three 'Kalamata' mother trees, 120 embryos, and all potential pollen donors. The identified alleles were analysed using FaMoz software and showed that 'Kalamata' was highly self-incompatible. Only three 'Kalamata' embryos were assigned to 'Kalamata' self-fertilisation, even though it was the most available pollen donor. The alleles were also analysed using NTSYS-pc (version 2.02 k) software and identified 54 potential pollen donors in the study site; however, not all of them were located within the effective pollination distance of the mother trees (30 m in olive). According to the results of this study, 'Kalamata' (as a host) was compatible with 'Barnea', 'Benito', and 'Katsourela' (six 'Kalamata' embryos assigned in each) but incompatible with 'Arbequina', 'Azapa', and 'Picual' (zero 'Kalamata' embryos assigned in each). The olive growers could use some of these compatible pollenisers with 'Kalamata' to guarantee good fruit set.

2008, Seifi, Esmaeil, Guerin, Jenny, Kaiser, Brent, Sedgley, Margaret

The influence of flower position on the inflorescence on opening day, gender, and petal persistence was studied in three olive cultivars: Manzanillo, Mission, and Frantoio. In each cultivar, 45 inflorescences were checked every morning from flower opening to petal fall. Perfect flowers opened mainly in the beginning of the flower opening period, and staminate flowers opened later. Flower position on the inflorescence had a highly significant effect on the opening day in all cultivars. Terminal flowers and the flowers located on the primary branches opened earlier than the flowers located on the secondary branches. Flower position had also a highly significant effect on gender in Manzanillo and Mission. In Manzanillo, the secondary branches had fewer perfect flowers than the primary branches. In Mission, the secondary branches had no perfect flowers at all. Among the primary branches, the branch arising immediately next to the terminal flower had the latest flowers to open and the lowest percent of perfect flowers. In Manzanillo, perfect flowers had significantly longer petal persistence than staminate flowers. To study flower competition within the inflorescence, the distal half of 120 inflorescences, on which the flowers tend to be perfect, in three trees of Manzanillo were removed about 1 month before full bloom. There was a highly significant effect on the percent of perfect flowers that opened on the proximal half. Flower competition may be a reason for pistil abortion in flowers located on secondary branches.

2013, McFadyen, Lisa, Robertson, David, Sedgley, Margaret, Kristiansen, Paul, Olesen, Trevor

In Australian macadamia ('Macadamia integrifolia' Maiden and Betche, 'M. tetraphylla Johnson' and hybrids) orchards, trees are generally side-hedged in early spring to maintain the inter-row for efficient orchard management. Hedging at this time increases fruit abscission and decreases yield due to competition for carbohydrates between fruit and post-pruning shoot growth, and to the loss of photosynthetic area. Girdling increases fruit set in many crops and the possibility that girdling might mitigate the effect of pruning on fruit abscission and yield was investigated in this study. Girdling was also investigated for its potential to control shoot growth and tree size. In the first experiment, in early spring around anthesis, trees were pruned (P), pruned and girdled (PG), or were left as unpruned and ungirdled control trees. Fruit per raceme over time, percent of racemes with fruit at 20 weeks post anthesis, fruit number per tree, nut weight, yield, and the shoot length and number of the post-pruning flush were measured. In a second experiment, trees were pruned (P) or pruned and girdled (PG) in autumn, and the shoot length and number of the post-pruning flush were measured. In a third experiment, trees were girdled at anthesis in 3 years over a 4-year period and shoot growth, tree height, yield, fruit number and nut weight were compared with ungirdled control trees. Girdling mitigated the effect of pruning on fruit abscission and yield but the mitigation was slight with PG trees producing 28% less yield than unpruned control trees. Girdling reduced shoot length and number but more so on unpruned branches (26% and 28%, respectively) than on pruned branches (10% and 14%, respectively). The tree height increment in girdled trees was around half that of ungirdled trees. In the 4-year study, girdling increased yield by around 10% in two out of four seasons, and decreased it in one season. Cumulative yields were similar for girdled and ungirdled trees. This study has shown that girdling was not useful in mitigating the effect of pruning on yield. However girdling was effective in controlling shoot growth and tree size, with no reduction in cumulative yield, and may be useful as a tree size control strategy. Further monitoring of long-term effects of repeat girdling is required to confirm this.

2009, Wilkie, John D, Sedgley, Margaret, Morris, Stephen, Muldoon, Steven, Olesen, Trevor D

Macadamia ('Macadamia integrifolia' Maiden and Betche, M. 'integrifolia X tetraphylla' Johnson) flowers are borne on racemes that usually originate from axillary buds in response to cool conditions. In this report, we examine the relationship between stem characteristics and the number of racemes produced, to improve our understanding of the control of floral initiation and axillary bud release.Two macadamia trees of each of the cultivars 'A4', '660', '695', and 'A38' were pruned annually for 3 years and the relationships between stem length, stem age, the number of vegetative flushes, stem orientation, and the number of racemes produced were quantified in year 4 (2006). In addition, trees of cultivar '849' were pruned in Autumn and early Summer, and the flowering characteristics of the post-pruning vegetative flushes were monitored the following Spring (2006). There were significant differences in the extent and location of racemes between cultivars. Racemes were produced preferentially on short stems that consisted of few vegetative flushes. In cultivar 'A4', 1-year-old stems were more likely to flower than 2-year-old stems; whereas, in cultivar 'A38', 2-year-old stems were more likely to produce racemes than 1-year-old stems. As stem orientation changed from horizontal to vertical, the likelihood of raceme production increased in cultivar '660' stems consisting of one flush and in '695' stems consisting of two flushes. Stem characteristics, particularly stem age and vigour, indicate the likelihood of flowering, but position within the canopy may be another important consideration. Canopy management practices that promote the production of short stems may increase whole-tree raceme production and, given the variation in the location of raceme production with cultivar, canopy management practices specific to cultivar should be considered.

2013, McFadyen, Lisa Maree, Robertson, David, Sedgley, Margaret, Kristiansen, Paul, Olesen, Trevor D

Yields of macadamia ('Macadamia integrifolia', 'M. tetraphylla', and hybrids) orchards tend to increase with increasing tree size up to ≈94% light interception. Beyond this, there is some indication that crowding leads to yield decline, but the evidence is limited to one site. Increasing tree size and orchard crowding also present numerous management problems, including soil erosion, harvest delays, and increased pest and disease pressure. The aim of this study was to better characterize long-term yield trends in mature orchards and to assess the effects of manual and mechanical pruning strategies on yield, nut characteristics, tree size, and economics. We monitored yield at four sites in mature '344' and '246' orchards for up to seven years and confirmed a decline in yield with crowding for three of the sites. There was a small increase in yield over time at the fourth site, which may reflect the lower initial level of crowding and shorter monitoring period compared with the other sites, and highlights the need for long-term records to establish yield trends. Pruning to remove several large limbs from '246' trees to improve light penetration into the canopy increased yield relative to control trees but the effect was short-lived and not cost-effective. Removal of a codominant leader from '344' trees reduced yield by 21%. Annual side-hedging of '246' trees reduced yield by 12% and mechanical topping of '344' trees caused a substantial reduction in yield of up to 50%. Removal of limbs in the upper canopy to reduce the height of '344' trees had less effect on yield than topping but re-pruning was not practical because of the extensive regrowth around the pruning cuts. Tree size control is necessary for efficient orchard management, but in this study, pruning strategies that controlled tree size also reduced yield. Research into the physiological response to pruning in macadamia is required to improve outcomes.

2009, Rabiei, Reza, Wu, Shubiao, Gibson, John, Hunt, Peter, Murison, Robert D, Sedgley, Margaret

Almond (Prunus dulcis) is the only nut crop of the Rosaceae. As one of the earliest species to bloom in spring, almond trees can experience severe crop loss due to late frosts and unfavourable climatic conditions. The Australian almond breeding program is one of the world's major almond breeding programs and has developed a genetic linkage map. One of the objectives of the project is to investigate the inheritance of flowering time. The flowering time of a 'Nonpareil' x 'Lauranne' population was evaluated for two years. The proportion of buds and flowers at seven stages of bud and flower development were recorded for each tree using the same procedures in each of two years. A proportional odds logistic model was used to analyse the data, considering the timing of development of buds and flowers as a latent variable that was estimated for each tree on each occasion recorded. These estimates of flower timing were then used in QTL analysis of flowering time. The goal of this project is to identify genetic markers useful in breeding for altered flowering time in almond.

2011, Wilkie, John D, Sedgley, Margaret, Olesen, Trevor David

Macadamia is a subtropical, evergreen tree which flowers in response to cool temperature, producing racemes that originate from axillary buds. The physiology of macadamia flowering, including some new data, and applications to canopy management are discussed. Floral initiation is also reliant on axillary bud release, which is affected by the timing of vegetative growth and characteristics of the stems. Other endogenous signals, including signals from the fruit, may also be involved. The most common form of canopy management in Australian macadamia orchards is mechanical hedging. Well timed autumn hedging or hedging in early winter would ensure the absence of immature vegetative flush that has the potential to suppress flowering. The relationship between flowering and yield in macadamia is largely unknown, so increasing flowering may not necessarily increase yield as with some other subtropical and tropical tree crops.