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Mango flowering is interannually variable and temperature dependent. Flowering intensity declines with increasing pre-flowering temperatures associated with global warming, potentially limiting yields. Additionally, floral density that does not contribute to greater yield represents an unnecessary drain on plant resources such as nutrients, water, and carbohydrates. This can lead to reduced fruit bearing capacity in later stages of cropping or contribute to interannual yield variation. The objective of this work was to identify the floral density compensation point (FDCP), above which additional flowering becomes redundant, and below which surplus carbohydrates are partitioned to existing flowers, fruit, vegetative growth, or stored. Over two growing seasons, the number of inflorescences on 32 Calypso® mango trees in Dimbulah, Australia were thinned by up to 95%, resulting in floral densities between 0.09 and 4.14 inflorescences per trunk cross sectional area (cm2). Fruit yield, number, composition, vegetative growth, and starch concentration in terminal growth units were measured for each of the trees. Calypso® mango trees have excess floral density, beyond the maximum fruit biomass the tree can support to harvest. Below the FDCP, the tree is unable to compensate for low numbers of inflorescences, and floral density was strongly positively correlated with fruit number and yield, and strongly negatively correlated with fruit per panicle and total soluble solids concentration of ripe fruit. Above the FDCP fruit yield, number and total soluble solids concentration were only weakly related to floral density as they appear limited by carbohydrate availability rather than flowering. Fruit weight, vegetative regrowth of fruiting and non-fruiting terminals, and the starch concentration in terminal growth units were less dependent upon the FDCP and changed continuously across the floral densities evaluated. This information will be valuable for managing mango flowering unde

Orchard intensification of temperate tree crops such as apple, has led to significant increases in productivity. In this research program, we aimed to adapt the principles and management systems that have made these intensive systems so productive to the less developed, extensive orchard systems of subtropical and tropical tree crops. For the work we chose the commercially important avocado, macadamia and mango, because of their high potential for improved productivity. The key components of modern apple orchard systems that allow them to be so productive are orchard light relations, vigour management, crop load, and tree and shoot architecture. Our approach has been to improve understanding of these key components through research, which we used to develop alternative management options and radically redesign orchard production systems. This research used applied field experiments, molecular genetics and plant modelling. A major focus of the program has been large scale Planting Systems Trials for each crop, where we investigated how the key components interacted with each other at different tree planting densities, scion varieties, rootstocks, and tree training systems.

Avocado (Persea americana Mill.) yields are low compared to other fruit crops, commonly less than 10 t ha-1 in Australia, prompting our research into improving productivity through understanding and improving crop load capacity. When we removed varying percentages of inflorescences on 3-year-old ‘Hass’ trees in a trial at Childers, central Queensland, Australia, we found clear relationships between number of inflorescences and yield, yield and vegetative growth, as well as yield and fruit size. In a second trial, we removed the whole or part of the vegetative tip of indeterminate inflorescences on 3-(then 4-)year-old ‘Hass’ trees to reduce vegetative competition with fruit growth. Spring fruit set increased in these tipping treatments in one of two years of the trial, but final fruit set did not differ from the control in either year. In the same trial, foliar application of “Cytolin” (®Sumitomo Chemicals, 19 g L-1 6-benzyladenine and 19 g L-1 gibberellins4+7) at the end of the extension of the spring flush to increase increasing axillary branching and thus fruiting sites, increased the total length of summer vegetative growth of shoots but not branching

Productivity in temperate tree crops such as apple has been lifted several-fold by research focusing on optimising a combination of canopy components including light relations, vigour control, tree architecture and crop load. This paper outlines the research behind the Small Tree-High Productivity Initiative (STHPI), which is focused on improving productivity of mango, avocado and macadamia. Preliminary results from work we are undertaking for each of the above canopy components in mango will be outlined. A rootstock screening trial to identify vigour-managing, high-productivity rootstocks is being undertaken, and we present a comparison of the best-performing low-medium vigour rootstock varieties compared with control 'Kensington Pride' (KP) rootstock at 6 months old. Comparisons between 'Keitt', 'NMBP 1243' and 'Calypso' scion cultivars with regard to tree diameter, height and canopy growth at different orchard densities and training systems will also be presented. Preliminary results from an orchard light-relations study indicate that mango yields continued to increase with light interception up to 50%, and reached a maximum of 20-30 t ha-1 at 68% light interception in KP trees approximately 25 years old. In a crop load trial, inflorescence thinning in a 'Calypso' orchard did not significantly reduce yields when up to 90% of inflorescences were removed, but did when 95% of inflorescences were removed, as trees were unable to compensate by adjusting fruit set, size and yield. Inflorescence thinning beyond 80% increased the number of fruit set per panicle, and thinning up to and including 90% of inflorescences increased fruit weight from 340 g to ›400 g per fruit. This project is still in its initial stages; however, early indications suggest there may be opportunities to improve early orchard yields through optimising light interception in an orchard's life, potentially through the use of higher densities, and that rootstocks and tree training methods, once identi