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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)_gibberellins(4+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.

The temporal passage of fruit through the supply chain and the selection of consumable fruit by shoppers depend primarily upon fruit firmness. Traditionally, fruit firmness measuring methods, like Effegi and conical probes, are relatively inefficient and destructive. Simple, accurate and non-damaging methods of measuring fruit firmness are ideally required to help assure eating quality to the consumer without fruit wastage. The firmness of 'Hass' avocado fruit at a range of ripening stages was measured with the various different firmness measuring techniques of the Sinclair iQ Firmness Tester (SIQFT), the Electronic Firmometer (EF), the Analogue Firmness Meter (AFM) and hand squeezing. Measurements were made by each method at different points on the same fruit. Destructive bruise assessment was performed 48 h later, thereby allowing sufficient time for fruit to express any bruising resulting from the act of firmness measurements. Non-linear relationships were determined between fruit firmness values measured with the different techniques. The adjusted R2 for the relationship between the SIQFT and the EF was 91.6%. For the SIQFT and the AFM, the adjusted R2 was 73.7%. It was 77.7% for the SIQFT and hand squeezing. A significantly (P

Australian avocado production has increased 73% in the last 7 years, which has raised interest in increasing domestic consumption and expanding export markets (currently less than 3% of Australian avocado production is exported). Export opportunities in the European Union have been identified, but the current seafreight duration of 39-42 d is one of the major constraints. Quality of fruit at the start of storage, storage system, and storage duration are key factors in outturn fruit quality. To test the ability of Australian 'Hass' avocados to withstand a long seafreight journey, fruit from six growers in south-east Queensland were ripened (no ethylene) at 18°C without storage or after being held for 42 d in either: air at 5°C; or air at 1°C after low temperature conditioning for three days at 6°C; or air at 5°C after treatment with 1-MCP (0.3 μl L -1 ) for 18 h at 5°C; or a standard 20 foot controlled atmosphere (CA; 2% O 2 /5% CO 2 ) container at 5°C. To simulate further coolstorage after arrival in the export market, additional fruit from the CA container were also held in air at 5°C for a further 3-7 d before ripening without or with ethylene. External fruit quality was assessed during storage (except for CA fruit) and on removal, and external and internal quality assessed at an eating ripe stage. CA storage resulted in excellent outturn quality, both at removal and at eating ripe. Following CA storage, fruit could be stored for an additional seven days under air at 5°C with no further loss of ripe quality. 1-MCP treated fruit had also good outturn quality, but ripening was variable. Air storage at 5°C or low temperature conditioning then holding at 1°C resulted in significant quality loss due to mainly flesh diseases, diffuse discolouration, and vascular leaching.

To obtain the maximum benefits from dynamic controlled atmosphere (DCA) storage, several parameters of operation need to be optimised. These parameters include the time after harvest at which the lowest safe O 2 level is first established (delay), the degree of back-off in O 2 above the low O 2 stress point (back-off), and the frequency of resetting the lowest safe O 2 level during storage (frequency). The DCA operating parameters delay, back-off and frequency were investigated by storing 'Hass' avocado fruit for 6 weeks at 5°C in DCA. Fruit were held in air for 48 or 96h after harvest before the initial lowest safe O 2 level was established by backing-off by 0.2 or 0.8% O 2 . The lowest safe O 2 level was reset every 10 d (repeat) throughout storage, or left as that achieved at the start of DCA (once). In addition, to determine whether the fruit response to the DCA operating parameters changes through the harvest season, fruit were harvested during the early (late October), mid (mid December) and late (mid February) periods of the harvest season. Fruit quality following DCA was optimised by setting the DCA O 2 level soon after harvest, backing-off to just above the low O 2 stress point, and repeatedly re-setting the O 2 level during storage. The main effect of frequency was on skin colour and rots (fuzzy patches; FP) at the end of storage, and on the time to ripen after storage. In contrast, the effects of back-off were on FP and diffuse flesh discoloration and delay on stem-end rot expression. There were no major differences in the responses of fruit harvested at different times of the season to the DCA operating parameters. It is concluded that for New Zealand-grown 'Hass' avocados, DCA should be established within 2-4 days of harvest, backing-off to just above the low O 2 stress point and resetting the lowest safe O 2 level every 10 days.

The objective of the present work was to verify the ethylene absorption effect on the avocado fruit conservation stored under different temperatures and modified atmosphere. Ten fruits were packed in the plastic boxes wrapped in low density polythene bags. Two lots of samples: one without ethylene absorption but with "Green Keeper ® " absorber, under temperatures of 3, 6 and 20°C. The bag inside air samples were taken by the use of a syringe and the CO 2 and C 2 H 4 were determined through the gas chromatography process. The physical quality index was evaluated through the fruit peel resistance loss by the maximum rupture force determined by the puncture test on three equidistant equatorial zones on 15 fruits collected in the random way from the bags. The analysis were done at 0, 5, 7, 9 and 11 days under the temperature of 20°C; and 0, 11, 18, 25, 32, 39, 46, 53 and 60 days under temperatures of 3 and 6°C. From the results obtained it can be concluded that for temperatures of 20°C, the use of ethylene absorber induces the avocado ripeness process delay indicated by higher peel resistance evaluated through the maximum puncture force. For the temperature of 6°C the ethylene absorber effect occurred on the ripeness from 39 th day. However, for temperature of 3°C the metabolic activity blockade occurs and the ethylene absorbing action did not happen.