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A field study was conducted to examine the effects of various bunch covering and harvest delay combinations on the environment inside bunch covers, and on fruit yield and quality parameters. Treatments included the use of both unsealed and initially sealed (but often ultimately leaky) clear covers under the industry standard blue/silver cover, and the inclusion of an ethylene absorbent inside 'sealed' covers. The finger length, girth and weight of 'sealed' cover bunches that were harvested late were increased by up to 11, 13, and 37% respectively. Maturity bronzing increased with increasing delay of harvest of 'sealed' cover fruit. Greenlife was increased by the 'sealed' cover treatment, but decreased with increasing delay of harvest of 'sealed' cover bunches, and was increased by the presence of KMnO,. Greenlife was inversely related to finger size such that any treatment resulting in larger fruit tended also to reduce greenlife. The peel of ripe fruit from 'sealed' covers was greyer than that of the controls. Delaying harvesting increased the pulp to peel ratio of ripe fruit by 4%. The flavour of 'sealed' cover fruit was blander than that of their counterparts, with delay of harvest further reducing flavour. Up to about 40% of bunches were lost before harvest, due to snapped stems or to rotting of the bunch when the harvest of 'sealed' cover bunches was delayed during the warmer part of the year. Consequently, the yield of fruit with greenlife in excess of 10 days was as high from the standard treatment as from any of the more elaborate treatments. However, the 'sealed' cover treatment, when harvested at the normal time, produced the most fruit with a greenlife greater than 30 days.

A field study was conducted to examine the effects of various bunch covering and harvest delay combinations on the environment inside bunch covers, and on fruit yield and quality parameters. Treatments included unsealed and initially sealed (but often ultimately leaky) clear covers under the industry standard blue/silver cover, and the inclusion of an ethylene absorbent inside the 'sealed' covers. This paper reports on the microclimate inside the bunch covers, and the modified atmosphere that developed inside the 'sealed' covers. During clear weather in January, average air temperatures inside bunch covers were 3, 5, and 6C above ambient for unsealed single covers, for unsealed double covers, and for 'sealed' double covers respectively. Differences were smallest at dawn, and greatest in the late afternoon. During clear weather in July bunch cover temperatures were 1, 1.5, and 2C above ambient respectively. Relative humidities were also influenced by covering, with 'sealed' cover humidity remaining above 95%. Carbon dioxide concentrations inside 'sealed' covers when bunches were harvested averaged 8%, but varied widely from <1 to 42%. Highest CO2 concentrations were obtained when weekly mean air temperatures were greater than 22C. Oxygen concentrations averaged 10% (range 2-19%), were lowest during the warmer part of the year, and were inversely related to CO2 levels. Ethylene concentrations varied between 0.03 and 9 L/L, were highest during the hotter part of the year, and were reduced by about 60% with the inclusion of KMnO4 inside 'sealed' covers. An iterative model with a .l h time step was used to simulate the expected O2 and CO2 levels inside the 'sealed' covers. Simulation results indicated that polyethylene permeability alone could not balance the computed respiratory gas exchange, and account for the changes in O2 and CO2 concentrations. It was necessary to incorporate a substantial leakage component into the model in order to simulate successfully the field observations.

Delicious apples were stored at four temperatures from 0C to 20C to produce fruit at different stages of deterioration. At regular intervals, the texture, flavour, and overall quality were assessed by a taste panel, and the flesh firmness, titratable acidity, soluble solids and starch content were measured. It was found that changes in flavour, texture and overall quality were highly correlated and that acceptability of fruit held at higher temperatures declined at a faster rate. During storage there was a decrease in flesh firmness and titratable acidity that was highly correlated with flavour, texture and overall quality. The use of either measurement would seem to be suitable to assess whether fruit were of a sufficiently high quality to warrant marketing. Soluble solids increased during storage but tended to stabilize at a maximum level of about 14%. Starch content decreased during storage to a level where it was undetected by the iodine test. Neither measurement appeared suitable to grade fruit for marketing.

The induction of six infection-related mRNAs (IRmRNAs) was studied in barley and wheat following infection by different pathogens. Barley was inoculated with the compatible pathogens, chlorostriate mosaic virus, barley stripe virus, Pseudomonas syringae, Pyrenophora teres, Bipolaris sorokiniana, Erysiphe graminis f. sp. hordei and the incompatible pathogens E. graminis f. sp. tritici, Puccinia graminis f. sp. tritici and Py. tritici-repentis. Wheat was inoculated with the compatible pathogens B. sorokiniana, Pu. Graminis f. sp. tritici and E. graminis f. sp. tritici and the incompatible pathogen E. graminis f. sp. hordei. Induction of the IRmRNAs was observed after inoculation with fungi but not by bacterial or viral infection. The results demonstrated that necrotrophic fungi will induce the mRNAs at very early stages of infection. The IRmRNAs are thus not specifically related to obligate parasites. A comparison of the extent and speed of mRNA induction following infection of both wheat and barley by closely related fungal species suggested a role for IRmRNAs 2, 5 and 6 in non-host resistance reactions. These studies indicate that cereals may resist fungal pathogens by the early activation of a series of defence genes.

Wheat plants (Triticum aestivum cv. Hartog) were stably transformed with the bar gene and the gene encoding the barley yellow mosaic virus coat protein. Cultured immature wheat embryos were bombarded with tungsten particles coated with the pEmuPAT-cp construct. Fifteen regenerating 'PPT- resistant' plants were selected on medium containing phosphinothricin. Of these, 11 plants had both the bar and cp genes integrated into the wheat genome and two plants had only the bar gene. Transmission of the two genes to progeny of two independent plants was confirmed. The barley yellow mosaic virus coat protein was detected in both the parent and progeny plants; however, bar gene expression occurred only in the parent plants.

Embryogenic callus, derived from immature embryos of an Australian wheat (Triticum aestivum L. cv. Hartog) was used to establish liquid cultures which consisted of cell clumps (2-8 mm in diameter); these have been maintained for 20 months and still retain their embryogenic potential. This was achieved by continuous selection of embryogenic clumps at subculture. Incubation of callus in medium containing low concentrations of 2,4-D facilitated the selection of embryogenic cell clumps. After more than 1 year in liquid medium, 37% of the cell clumps formed embryoids and green plants on differentiation medium. The addition of silver nitrate to the subculture medium, which contained 5 μM 2,4-D, enhanced the differentiation frequency of the callus. A study of embryogenic calli from different wheat cultivars showed genotype was important for the retention of embryogenic potential in liquid medium. Fine suspension cultures, consisting of rapidly growing small aggregates of 2-200 cells, were derived from liquid cultures of cv. Hartog. Cytological examination showed that the cells of the fine suspension cultures had the normal wheat chromosome complement (2n = 42). Following transfer to differentiation medium, the fine suspension cultures formed soft as well as solid callus, from which embryoids and green plants have been obtained. Protoplasts isolated from the fine suspension cultures formed green plants with morphologically normal shoots and roots.

The rotting of four guava cultivars was considerably reduced in laboratory experiments by dipping the fruit after harvest in solutions containing benomyl at 0.5-2.0 g/l. The optimum dip temperature was 48-50C with an exposure time of 5 min. Heated guazatine dips also reduced rotting but were less effective than benomyl and induced skin injury more readily; optimal conditions were a guazatine dip at 0.5 g/l for 5 min at 50C. Hot water dipping gave some reduction in rotting but was less effective than benomyl and guazatine.

Potassium permanganate reduced the concentration of ethylene and calcium hydroxide reduced the concentration of carbon dioxide in sealed polyethylene bags containing bananas. When the fruit that were not packed in sealed bags were ripe (16 days after the beginning of storage) all the fruit in sealed polyethylene bags were in a firm green condition and there was little difference between treatments in sealed polyethylene bags. After 29 days some of the fruit in sealed bags had softened, but fruit in bags containing potassium permanganate was firmer than fruit receiving other treatments, and this effect was more marked after 38 days. It was estimated that about two weeks additional storage life was obtained by packing potassium permanganate with the fruit.

The onset of brown heart was studied in Williams Bon Chretien pears stored in polyethylene bags for various periods at 30F and subsequently held at 68F for seven days. During storage at 30F the carbon dioxide contents of the atmospheres inside the bags varied from 3.4 to 7.1 per cent and the oxygen levels varied from 6.5 to 18.7 per cent. The proportion of pears with brown heart has been related quantitatively to storage period and concentrations of carbon dioxide and oxygen within the bag. The average incidence of brown heart increased linearly from about 9 per cent after 56 days to about 51 per cent after 118 days. The incidence of brown heart increased with increasing levels of carbon dioxide and fell as oxygen levels rose.

Experiments were carried out during a period of five years with Jonathan, Delicious, and Granny Smith apples, stored at 32F in polyethylene film bags. After storage for five to seven months best retention of ground colour, least weight loss, and least wastage from superficial scald and low-temperature breakdown were obtained in bags in which the levels of oxygen were low (minimum 3.6 per cent), or in those in which the levels of carbon dioxide were high (maximum 6.7 per cent). Low-temperature breakdown was decreased markedly when calcium chloride was placed inside the bags to reduce the humidity. The use of calcium hydroxide to absorb carbon dioxide did not reduce the disorder.

New South Wales grown Granny Smith apples were stored for seven months in three seasons. The effects of four controlled atmospheres and two air storage temperatures on final fruit quality and on development of senescent disorders were studied. To minimise superficial scald, to which the variety is very susceptible, the fruit was wrapped in diphenylamine wraps prior to storage. Assessment of quality after storage was made by panel judgments of appearance and edibility. The effects of the storage conditions on the development of disorders were assessed by scoring methods. In general, controlled atmosphere storage reduced the development of senescent disorders and proved superior to air storage in the maintenance of fruit qualify. Atmospheres containing carbon dioxide best preserved external appearance but an atmosphere of low oxygen with carbon dioxide removed resulted in superior internal quality. Of the treatments studied 5 per cent carbon dioxide with 2.5 per cent oxygen gave best overall fruit quality.

The preliminary work of Smock (1955) indicated that treatment of apples with diphenylamine (DPA) offered a promising new method of controlling superficial scald on cool-stored apples. The effect of DPA and various methods of application hare been widely studied under Australian conditions over five seasons, Granny Smith apples grom-n in New South Wales being used. Treatment of fruit with a suitable concentration of DPA prevented the development of scald on fruit cool-stored in air, in controlled atmospheres, and in polyethylene film box liners, even when scald was severe and not controlled by oiled wraps. DPA was successfully applied to the fruit by impregnating it into standard paper wraps, by post-harvest dipping, and by pre-harvest spraying. It was found that there was a quantitative relation between the severity of scald and the concentration of DPA required to control it. DPA was shown to have a very limited mobility in the fruit. Residues in the fruit were related to both the amount applied and the method of application, and in all cases were low after cool storage. DPA appears to have a sufficiently low phytotoxicity for use as a pre-harvest spray. Its human toxicity is still under investigation. If approved for use on apples it will probably be in a purified form.

In the past, experiments on controlled atmosphere storage have tested specific combinations of carbon dioxide and oxygen, usually in a manner which precludes determination of the effect of change in concentration of these gases. The data from the series of trials discussed in this paper permitted an investigation of the effect of concentrations of carbon dioxide and oxygen on the incidence of scald with simple and multiple linear regression techniques. The method was applied to data from three types of controlled atmosphere storage: (1) Carbon dioxide 2.5–10% at 2.5% oxygen, (2) Oxygen 1.25–20%, at near zero carbon dioxide, (3) Carbon dioxide 3.3–10.9% oxygen 2.2–16%. The relation between scald (Y), carbon dioxide concentration (x), and the reciprocal of oxygen concentration (z), was described by the regression equation:Y = y + b(x – x) + c(z – z), which implies that scald is directly proportional to carbon dioxide concentration and indirectly proportional to oxygen concentration. The effects of changes in concentration of the gases, as estimated by the regression coefficients, were consistent for size of fruit, season, and orchard, but the effect for oxygen was dependent on the method of maintaining the atmosphere. Good control of scald was obtained with low oxygen atmospheres, even after storage for 6–7 months.

Studies were made of the effect of different treatments on weight loss and breakdown of Jonathan apples. The apples were stored at 30F under high relative humidity except while the following treatments were applied : initial storage at 30F for 2, 4, 6, 8, and 10 weeks at 65 per cent relative humidity ; storage at 30F over calcium chloride for 8 weeks ; hydrocooling ; step-wise cooling from 36F to 30F ; and warming the fruit at 68F for 24 hours. The level of breakdown in all treatments depended on the loss in weight of the fruit. Initial storage at low humidity appears to be a practical method of reducing breakdown.

Thiabendazole, 2-amino butane, and Shirlan were compared as dip treatments for the control of black-end in bananas artificially inoculated with Gloeosporium musarum Cke. and Masse. Thiabendazole virtually eliminated black-end at a concentration of 0.014 per cent and did not cause damage at a concentration of 0.16 per cent. The 2-amino butane gave satisfactory control at 0.58 per cent, but this concentration damaged the fruit. Shirlan was the least effective fungicide as it gave only moderate control at 0.6 per cent, and this was accompanied by severe damage to the fruit.

The incidence of breakdown in Jonathan and Delicious apples stored in the presence of calcium chloride was studied. Jonathans from two orchards and Delicious from one orchard were stored at 32F in 1963, and Jonathan and Delicious from one orchard were stored at 30, 32, and 36F in 1964. On four occasions in 1963, and on three in 1964, samples were transferred from cool storage to storage at 68F and inspected for breakdown seven days later. In each of the thirty orchard-variety-season-storage period classes the decrease in incidence of breakdown with increased weight loss was always very highly significant (P<0.001), and varied from 2.1 to 8.7 degrees for each per cent of weight loss.

The behaviour of Jonathan apples in storage was studied in relation to the concentrations of carbon dioxide and oxygen in the storage atmosphere. A factorial design of 2, 4, and 6 per cent carbon dioxide and 1.2, 2.2, and 13.2 per cent oxygen was used and apples were removed from storage at 32F after 20, 23, and 26 weeks. The concentrations of carbon dioxide and oxygen in the storage atmosphere were related quantitatively to weight loss, ground colour, firmness, titratable acidity, and to the incidence of superficial scald and breakdown. Rest retention of weight, acids, ground colour, and firmness, and least wastage from superficial scald were found in atmospheres with high carbon dioxide and low oxygen concentrations, but more of the fruit in these atmospheres had breakdown.