A comparative analysis of transgenic pineapple lines transformed with a polyphenol oxidase (PPO) gene (ppo) and the untransformed cultivar 'Smooth Cayenne' was made from plants grown in a series of field trials under cool subtropical conditions in southeast Queensland. In the four field trials where blackheart was recorded, all of the control lines expressed blackheart on each occasion and exhibited the greatest incidence (50%) and severity (34%) of symptoms. Irrespective of the gene transfer method or the gene construct used, 38% of the lines produced were regarded as blackheart resistant, having no blackheart symptoms in two or more trials. Five blackheart resistant transgenic lines consistently performed as well as or better than control plants in terms of fruit characteristics and quality. Crown Copyright (C) 2013 Published by Elsevier B.V: All rights reserved.

Changes in the quality of `Kensington' mangoes from the two major production regions in Queensland were measured after either a vapour heat treatment (VHT) in which seed surface temperature was held at 47°C for 15 min, or a hot water (HW) disease control treatment of 53°C for 5 min prior to VHT, combined with either storage at 10°C for 5 days followed by 22°C for 5 days or storage at 22°C for 10 days. Heat-treated mangoes had higher skin colour ratings, reflectance and chroma values, and lower hue angles than untreated fruit, indicating an enhancement of ripening. The severity of lenticel spotting and skin browning was increased in VHT fruit. Eating quality of the fruit was not altered by any of the heat treatments. The HW+VHT treatment combined with continuous storage at 22°C produced the highest quality fruit, and is recommended for air freight marketing.

Hot water treatment (HWT) offers a cost-effective method for fruit fly disinfestation but may cause injury to 'Kensington'' mango (Mangifera indica Linn.). Conditioning fruit with hot air before disinfestation may alleviate these injuries. Fruit from 2 major production regions in Queensland were subjected to conditioning treatments with hot air (38-40 degrees C) for 0, 4, 8, 12, and 16 h before HWT (fruit core temperature of 45 degrees C held for 30 min). Injuries to fruit not conditioned before HWT included accentuated lenticel spotting, external and internal cavities, and a starchy layer beneath the skin. Fruit conditioned for 8 or 12 h before HWT had minimal injuries. Conditioning with hot air before HWT has the potential to minimise and/or eliminate heat injuries associated with hot water disinfestation treatment. Further testing, particularly on a commercial scale, will be required to optimise these conditioning treatments for use by the Australian mango industry.

Zucchini (Cucurbita pepo L.) were disinfested by a high humidity hot air treatment (HT) to a fruit core temperature of 45 °C for 30 min, and then stored at 7–8 °C. Skin yellowing (indicated by percentage yellowing and hue angle) generally increased with storage time, and was exacerbated by HT. While zucchini quality can be maintained for up to 11 days following HT, it appears that chilling injury prior to such treatment reduces the ability of the fruit to withstand this method of disinfestation.

The quality of 'Kensington' mangoes (Mangifera indica Linn.) from 2 major Queensland production regions was evaluated following a hot air [HAT, also known as vapour heat (VHT)] disinfestation treatment (46.5 degrees C seed surface temperature held for 10 min under conditions of high humidity) combined with a disease control treatment (55 degrees C water for 5 min) prior to HAT, and storage conditions likely to be encountered during air shipment to Japan (either 10 degrees C for 5 days plus 22 degrees C for 5 days, or 13 degrees C for 5 days plus 22 degrees C for 5 days, or 22 degrees C for 10 days). Final quality was optimum if fruit were treated with HAT alone and stored at 22 degrees C. Fruit injury, in the form of skin browning and lenticel spotting, was particularly severe in HAT plus disease control fruit stored at 10/22 degrees C. Storage at 10 degrees C combined with heat treatments may be too stressful to fruit physiology, leading to fruit injury and reduced fruit quality at the market destination.

Mature and immature ‘Kensington’ mangoes (Mangifera indica Linn.) were treated with an experimental high humidity hot air treatment (HT) to a fruit core temperature of 46.5 °C for 10 min for disinfestation purposes and to test for fruit injury reportedly associated with fruit immaturity. Two methods of determining fruit maturity were examined with fruit harvested over two different seasons, in order to gain a broad range of maturities. No internal or external injury was caused to fruit at any maturity stage by the treatment. Mature HT fruit softened faster and had increased skin colour development compared to immature HT fruit. HT shows commercial potential since the physiological changes associated with treatment and maturity can be managed with careful postharvest handling practices. We recommend only mature fruit be harvested and treated since quality and market performance will be maximised.

Vapour heat treatment (VHT) was used as a possible disinfestation treatment against fruit flies for lychee fruit. On the basis of an optimum core temperature of 45°C for variety ‘Tai So’, this and two other varieties ‘Kwai May Pink’ and ‘Wai Chee’, were exposed to this temperature for various lengths of time. ‘Tai So’ and ‘Wai Chee’, but not ‘Kwai May Pink’, tolerated this temperature for 42 min. without significant reduction in fruit appearance, eating quality and disease control following 2 weeks storage at 5°C, during which transport to distant markets could be undertaken. Preliminary results suggest that 45°C for only 30 min. is sufficient to kill all stages of the Queensland fruit fly, Bactrocera tryoni, so at least two of the three varieties tested could safely survive these conditions without quality reduction.

Three cultivars of lychee (Litchi chinensis Sonn., ‘Tai So’, ‘Kwai May Pink’ and ‘Wai Chee’) were dipped in hot benomyl (Benlate®, 50 wettable powder (WP) 1 g l−1 at 48, 50 and 52°C) for times from 0.5 to 18 min. Appearance and disease incidence were assessed after storage at 5°C for 2 and 4 weeks. Treatments at 48°C for 1–3 min and at 50°C for 1–2 min were found to give the best disease control and most acceptable fruit appearance. ‘Tai So’ was the least affected by heat treatment and showed the greatest storage potential. A previous recommendation for cultivar ‘Bengal’ of 52°C for 2 min was found to be unsuitable for the cultivars tested. Conditions of 48–50°C for 2 min are recommended as providing the best control of disease with minimal loss of skin colour.

Three commercial sweet corn (Zea mays L.) cultivars, a cultivar recessive for the sugary (su) allele and bred for high sweetness and low starch (‘Aussie Gold 12’), a standard su cultivar (‘Rosella 425’) and a supersweet cultivar recessive for the shrunken-2 (sh2) allele (‘Sucro’), were compared under post-harvest conditions for carbohydrate composition and eating quality for the fresh market. Cobs were stored for up to 10 days at either 1, 4, 7 or 18°C. The sucrose content of fresh ‘Sucro’ was approximately three times that of the other two cultivars. After 10 days storage at 18°C, percent total sugar depletion was greater for ‘Sucro’ (74%) than for ‘Aussie Gold 12’ or ‘Rosella 425’ (57 and 58%, respectively), but ‘Sucro’ still contained significantly more sugars than the other cultivars after storage.

The survival of Pseudomonas solanacearum biovars 2 and 3 in three soils, a Nambour clay loam, a Beerwah sandy loam and a Redland Bay clay, was compared at pressure potentials of −0.003, −0.05 and −0.15 kPa. The soils were inoculated with mutants of P. solanacearum biovars 2 and 3, resistant to 2000 μg streptomycin sulphate ml−1 and their survival measured every 6 weeks for 86 weeks in the clay loam and clay and for 52 weeks in the sandy loam. Soil populations declined with the initial drying necessary to bring the soil moisture to the specific pressure potentials; the initial counts for biovar 2 varied between 0.20 and 2.00 × 109 cfu g−1 soil and for biovar 3 between 0.17 and 1.29 × 109 cfu g−1 soil.