Benefits of ethylene removal during apple storage

The potential use of an ethylene absorbent in controlled atmosphere storage of two varieties of apple has been investigated. With Golden Delicious, the rise in ethylene concentration during controlled atmosphere storage can be delayed for about 40 days but not prevented by inclusion of potassium permanganate in the storage container. But with Bramley's Seedling, potassium permanganate can delay ethylene accumulation for over 200 days. Ethylene treatment of Bramley's Seedling in a flowing stream of 5% CO₂:3% O₂:92% N₂ caused accelerated softening, accumulation of α-farnesene and earlier onset of superficial scald. Use of potassium permanganate to remove ethylene during storage in static controlled atmosphere conditions retarded all three processes in Bramley's Seedling kept in 5% CO₂:3% O₂ and in 9% CO₂:12% O₂. However, in one experiment, ethylene removal in 5% CO₂:3% O₂, led to external and internal symptoms of CO₂ damage. A subsequent investigation of the combined effects of harvest date, store temperature and ethylene removal in 5% CO₂:3% O₂ did not show any damage or accumulation of succinic acid which is known to be involved in CO₂ injury. This experiment revealed that ethylene removal could be successfully accomplished on Bramley fruit harvested up to a month after the usual date and little α-farnesene accumulated in this fruit. Nevertheless scald did develop on late picked fruit and this raises doubts about the causal role of farnesene in scald.     

The influence of harvest maturity, calcium concentration and storage conditions on the keeping quality of Spartan apples grown in England

Spartan apples from several commercial orchards were stored in three successive years. The principal physiological disorders that developed were scald and core rowning. These disorders were minimised by picking at the end of September and storing in either 2% O₂ or 2% CO₂+ 2% O₂ at 1.5°C. Fruit calcium concentrations were usually high enough to avoid flesh breakdown but could be increased without risk of skin damage by dipping in a 2% solution of calcium chloride. It was concluded that storage of Spartan for up to 9 months is possible provided that fruit calcium concentrations are adequate and that picking date and storage conditions are optimised.     

Causes and effects of changes in xylem functionality in apple fruit

BACKGROUND AND AIMS: The xylem in fruit of a number of species becomes dysfunctional as the fruit develops, resulting in a reduction of xylem inflow to the fruit. Such a reduction may have consequential effects on the mineral balance of the fruit. The aim of this study was to elucidate the dynamics and nature of xylem failure in developing apples (Malus domestica) showing differing susceptibilities to bitter pit, a calcium-related disorder. METHODS: Developmental changes in xylem functionality of the fruit were investigated in "Braeburn" and "Granny Smith" apples by using a dye infusion technique, to stain the vasculature along the path of dye movement. The vascular bundles were clearly visible in transverse section when fruit were sectioned equatorially. The intensity of staining of the vascular bundles in the fruit was recorded at regular intervals throughout the season. Tissue containing dysfunctional bundles was fixed and embedded in wax for subsequent sectioning and examination. KEY RESULTS: As the season progressed, an increasing proportion of vascular bundles failed to show any staining, with the most marked change occurring in the primary bundles, and in nearly all bundles with increasing distance from the stalk end of the fruit. Decreased conductance in the primary bundles of "Braeburn" occurred earlier than in "Granny Smith". Microscopy revealed that the xylem in vascular bundles of the fruit suffered substantial damage, indicating that the mode of dysfunction was via the physical disruption of the xylem caused by expansion of the flesh. CONCLUSIONS: Results support the view that the relative calcium deficiency of apple fruit is due to a progressive breakdown of xylem conductance caused by growth-induced damage to the xylem strand in the bundle. The earlier onset of xylem dysfunction in the cultivar more susceptible to bitter pit suggests that the relative growth dynamics of the fruit may control the occurrence of calcium-related disorders.     

Fungitoxic and phytotoxic effect of some surface-active agents applied for the control of apple powdery mildew

Mixtures of methyl esters of fatty acids (‘Off-Shoot O’) and mixtures of fatty alcohols (‘Off-Shoot T’), applied during the late autumn (November), eradicated apple powdery mildew (caused by Podosphaera leucotricha) from infected buds. Applications in the spring at bud-burst were less effective. The autumn sprays caused little damage to the cultivars Bramley's Seedling, Cox's Orange Pippin and Golden Delicious but on Worcester Pearmain 50% of the buds were killed by a 5% Off-Shoot O spray. The bud-burst sprays were damaging and reduced yield on the Cox and Bramley trees. A 5% a.i. mixture of nonanol/lissapol applied to a range of commercial cultivars was effective in eradicating powdery mildew but was more phytotoxic than the Off-Shoot compounds. Spraying Cox trees later in the winter failed to reduce the damage. Eradication of the overwintering stage of the disease resulted in low spore concentrations during the following spring and early summer, enabling some economies to be made in the summer mildew fungicide programme.     

The ultrastructure of the outer tissues of cold-stored apple fruits of high and low calcium content in relation to cell breakdown

The outer tissues of Cox's Orange Pippin apples from samples with initially high and low calcium content were examined in the electron microscope following 53, 81 or 99 days in air storage at 3 ^oC. Cell ultrastructure within tissues of both high and low calcium apples was comparatively normal in fruit stored for the shorter period but low calcium fruit showed symptoms of membrane breakdown after 81 days. The greatest structural differences were observed after storage for 99 days when low calcium fruits contained more cells exhibiting breakdown of membranes and organelles than high calcium apples and also showed more severe symptoms of cell wall breakdown.     

Possible roles of calcium and ammonium in the development of bitter pit in apple

Apple trees ( Malus pumila Mill . var. domestica Fuji/ Malus prunifolia rootstock) showed a high susceptibility to bitter pit when supplyed with ammonium salt instead of nitrate (control) in the nutrient solution. When apple fruit was affected by bitter pit, a lower calcium as well as a higher nitrogen and ammonium-nitrogen contents was observed in the fruit flesh near the calyx end. The activity of the mitochondrial Ca²⁺-uptake of the fruit flesh near the calyx end was higher when the tree was grown with ammonium salt than when grown with nitrate. Both the activities of succinate: cytochrome c oxidoreductase and the mitochondrial Ca²⁺-uptake per g of tissue were higher in affected fruit than in healthy fruit. Each of chlorpromazine, N-(6-aminohexyl)-5-chloro-l-napthalenesulfonamide (W-7) and N-(6-aminohexyl)-l-naphthalenesulfonamide (W-5), calmodulin antagonists, was infiltrated into the fruit for 20 min under reduced pressure (about 1 × 10⁴ Pa). Few days later, numerous bitter pit-like spots were observed in both fruit treated with W-7 and chlorpromazine, while only a few spots were observed after the infiltration with W-5, a less potent calmodulin antagonist. A possible mechanism for the occurrence of bitter pit is discussed.     

A comparison of the use of Bacillus subtilis with conventional fungicides for the control of apple canker (Nectria galligend)

In a factorialized field trial cells of Bacillus subtilis or phenylmercuric nitrate (PMN) were applied as sprays in autumn to manually defoliated apple trees, cv. Bramley's Seedling, artificially infected with Nectria galligena. Trees were additionally sprayed with dithianon at intervals in May and June or left unsprayed at this time. B. subtilis in conjunction with dithianon, and PMN with dithianon were equally effective in the control of canker over a 2-yr period. Dithianon alone gave some control, as did PMN but B. subtilis was not effective without additional applications of dithianon.     

A study of gene expression changes at the <Emphasis Type="Italic">Bp-2</Emphasis> locus associated with bitter pit symptom expression in apple (<Emphasis Type="Italic">Malus pumila</Emphasis>)

Bitter pit is a physiological disorder of apples that develops in the latter stages of fruit development and during storage. It is characterized by localized necrotic cells that collapse and form pits in the epidermis and outer cortex of fruit. The disorder has been associated with low calcium concentrations, and poor calcium distribution within the fruit. To date, the mechanism that leads to individual cell necrosis, while surrounding cells remain healthy, is not fully understood. In order to ascertain the underlying process of bitter pit incidence in apple fruit, a large mapping population of “Braeburn” (susceptible to bitter pit)?×?“Cameo” (resistant to bitter pit) was used to map the trait over two growing seasons. A subset of 94 genotypes from the mapping population representing the full range of phenotypes in the same ratio as the full population were selected for genotyping and functional characterization. RNA-Seq analysis on fruit samples of three resistant and three susceptible lines at seven developmental stages (21, 42, 63, 84, 105, 126, and 147 days post fertilization) identified a number of candidate genes displaying differential gene expression. A subset of candidate genes selected based on their position within the identified QTL interval on linkage group 16 were validated by RT-qPCR, and two candidate genes displaying differential gene expression were highlighted as strong candidates for the control of bitter pit symptom expression at the Bp-2 locus.     

L'epoca Della Differenziazione Delle Gemme Fiorali Nell'olivo

Abstract

Calcium, as in general for all plants, is very important for fruit trees and a tight correlation between leaf content and cropping efficiency has been found.

The annual removal of calcium oxide of an orchard has been estimated in kg per hectare: pear 200, apple 180, peach 150, grape 60–130, olive 35–70, kiwi 55–60.

The rootstock affects the calcium uptake from the soil and content of the scion; frequently a higher calcium content is found in trees grafted an dwarfing rootstocks as pear on quince, apple on M9 and M26, peach on Damas.

By the horticultural point of view, calcium is responsible of two main problems: chlorosis due to high active Ca content in the soil and bitter pit, on the apposite, due to a low Ca level in the fruits.

From soil and leaf studies it seems clear that lime-induced Fe chlorosis results from two conditions: a) slow availability of Fe in the soil, and b) immobilization of Fe in the tree in forms that are not available for chlorophyll formation.

Breeding tolerant rootstocks has been the practical solution of chlorosis for most of the susceptible species.

Bitter pit is a physiological disorder of apple fruits, sometime already evident before picking, more frequently after harvesting, during the storage.

The prevention of the disorder is, essentially, a good horticultural practice (pruning, fertilization, irrigation, fruit thinning). Very effective are also Ca sprays as chloride or nitrate, or citrate, or phosphate, starting after setting, 4–5 times every 10–12 days.     

Calcium in plant senescence and fruit ripening

Abstract. Calcium has long been associated with regulation of the ripening process of fruit and post-harvest storage life. Specifically, maintenance of relatively high calcium concentrations in fruit tissue results in a slower rate of ripening, as seen in lower respiration rates, reduced ethylene production, and slower softening of fruit flesh. There are also some specific fruit disorders such as bitter pit, which can be prevented if sufficient calcium is present. Senescence of other plant tissues such as leaves and flowers has also been shown to be retarded by the application of calcium.
Work leading to the above information is reviewed and discussed in the context of what is currently known of cellular regulation of calcium in plants. The major sites for the action of calcium in senescence and ripening are suggested to be in membrane structure and function, and in cell wall structure. Although high external concentrations of calcium are an advantage in reducing the rate of senescence or ripening, it is emphasized that normal cell function requires the maintenance of low concentrations of free calcium in the cell cytosol. It is suggested that one possible feature of senescence is a breakdown in such cellular regulation.     

The response of apples cv. Cox's Orange Pippin to different concentrations of oxygen in the storage atmosphere

The response of apples cv. Cox's Orange Pippin to storage in flowing streams of air and nitrogen mixed to generate atmospheres ranging from 0.5% to 2% oxygen was examined in two seasons. The benefits of reducing store oxygen concentrations below 1.25% were small but storage in 0.75% may be advantageous for Cox's Orange Pippin apples in seasons when flesh firmness is low at harvest. Ethanol-induced flesh breakdown was recorded in samples stored in 0.5% O₂ in one season and the risk of low temperature breakdown was increased in oxygen levels below 1.25%. Ethylene production was reduced by lowering the oxygen concentration.     

The seasonal release of spores of Nectria galligena from apple cankers in Northern Ireland

Trapping of ascospores and conidia of Nectria galligena Bres. released from cankers on Bramley's Seedling apple trees over a period of three years showed that ascospores were most prevalent in the spring and early summer, and conidia from early summer to late autumn. Few ascospores were released in late summer or mid-winter but a minor period of discharge occurred in autumn. The distribution of cankers within trees in various orchards was also examined, and most were found to occur at the junctions of different seasons' growth. Possible reasons for this are discussed.     

Mercurous nitrate as a histochemical reagent for calcium phosphate in bone and pathological calcification and for calcium oxalate

Synopsis An aqueous solution of mercurous nitrate reacts with bone and tissue calcified sites with the formation of brown to black amorphous masses and feathery crystals, the last resembling the crystals formed from the action of an aqueous solution of mercurous nitrate on calcium orthophosphate. Calcium oxalate reacts with this mercurous nitrate solution to form brown to black deposits on the surface of the oxalate particles; this suggests an adsorption phenomenon. The brown deposits are blackened by ammonium hydroxide, gold chloride, and many sulphur-containing compounds.     

Control of purple spot of loquat fruit (Eriobotrya japonica) by means of mineral compounds

Treatments to control purple spot of loquat fruit (Eriobotrya japonica) were tested based on the hypothesis that the disorder appears as a consequence of water unbalance between flesh and epidermal tissues caused by their different ability for sugar accumulation. Calcium nitrate, calcium chloride, Ca‐EDTA, ammonium nitrate and potassium nitrate at a concentration of 150 mm applied 2 weeks before fruit colour break reduced significantly the proportion of purple‐spotted fruit, giving rise to a reduction of water potential of the epidermal tissue that allows it to retain water. The most favourable date of treatment was during the 2 weeks prior to fruit colour break.     

Inhibition of yeast respiration and fermentation by benomyl, carbendazim, isocyanates, and other fungicidal chemicals

The inhibition of yeast (Saccharomyces cerevesiae) metabolism by fungicidal chemicals was investigated. Glucose- or ethanol-dependent yeast respiration was measured with an oxygen electrode, and manometric determination of carbon dioxide release was used to measure fermentation. Both respiration and fermentation were inhibited more by benomyl than by identical molar concentrations of its breakdown product, carbendazim. Butyl isocyanate, another benomyl breakdown product, inhibited respiration more but inhibited fermentation less than the parent compound. Of the isocyanates tested, hexyl isocyanate was the most inhibitory towards both activities. Captan was more active and iprodione less active than benomyl. Because benomyl rapidly broke down to carbendazim when it was prepared in 80% ethanol, only 59% of the dissolved benomyl was intact when it was added to yeast to determine its effect on respiration or fermentation.     

The mechanism of calcium uptake by liver microsomes: effect of anions and ionophores

The mechanism of calcium uptake by liver microsomes was investigated using various anions and ionophores. Calcium uptake was shown to be specific to microsomes and unlikely to be due to contamination by plasma membranes by correlation of calcium uptake to the marker enzymes specific for these two fractions. Under the conditions employed, phosphates, sulfate, chloride, acetate, nitrate, thiocyanate, maleate, succinate and oxalate all stimulated calcium uptake by microsomes, but to different degrees. The greatest effect (4-6-fold) was observed with phosphate. On the contrary, phosphate is the only anion that stimulates the plasma membrane calcium uptake to any significant degree. Treatment of isolated microsomes with 4,4'-diisothiocyano-2,2'-disulfonic acid stilbene (DIDS) resulted in inhibition of ATP- and anion-dependent calcium uptake. A lipid-permeable organic acid such as maleate retained its ability to promote calcium uptake in DIDS-treated microsomes. However, a lipophilic anion, such as nitrate, stimulated calcium uptake only in the presence of the protonophore carbonyl cyanide m-chlorophenylhydrazone (CCCP). In addition, 2 microM valinomycin, when added in the absence or presence of 10 to 100 mM K+, had no stimulatory effect on calcium uptake. These results appear to be consistent with a model in which the active uptake of calcium into microsomes involves electroneutral Ca2+-nH+ exchange.     

Relationship between water-soluble Ca and other elements and bitter pit occurrence in 'Idared' apples: a multivariate approach

The mineral composition of sound fruits of Idared apple and those with symptoms of bitter pit was investigated at two sites on M9 rootstock (Sites 1 and 2) and two sites on MM 106 rootstock (Sites 3 and 4). Concentrations of N, P, K, Ca and Mg were measured. Mg and Ca concentration were determined in water soluble (WS) and water-insoluble (WI) fractions. The sum of these fractions was regarded as the total concentration (T). At all four sites, Ca (WS) was significantly higher in sound fruit. Principal component analysis (PCA) of data from individual locations showed that the first PCA component accounted for a high proportion of total variance (85% and 70% for Sites 1 and 2 and 70% and 69% for Sites 3 and 4, respectively). Projections of the samples into the planes of the first two PCA components revealed exact classification of the bitter pit status for all samples. The projections revealed that the first PCA component was essential for classification of the status. Determination of the distribution of components of the first PCA indicated that deficiency of water soluble Ca was the most significant factor related to development of bitter pit in ‘Idared’ apples.     

Comparison of fungicides for the control of Rhizoctonia solani causing datnping-off of mung bean (Phaseohis aureus)

Of 41 fungicides tested in the laboratory, copper carbonate, copper sulphate, mercuric chloride, Agrosan GN, quintozene, kasugamycin, carboxin, pyracar-bolid, carbendazim, chloroneb, benomyl, Ohric, RH 893 (2-n-octyl-4-isothiazole-3-one) and Terrazole were most inhibitory to the mycelial growth of Rhizoctonia solani on Czapek's agar plates and had EC₅₀ values of less than 1 μg a.i./ml, while copper oxychloride, Udonkor, zineb, ziram, F 319 (3-hydroxy-5-methyl isoxazole) and anilazine were much less toxic, ziram being least inhibitory with an EC₅₀ of 214 μg a.i./ml. Of 17 fungicides tested in the greenhouse as seed treatments, thiabendazole, carbendazim, benomyl, thiophanate-methyl, dichlozoline and Ohric gave 80–90% control of damping-off of mung bean seedlings. A single soil drench with thiophanate-methyl and two drenches with benomyl gave about 90% disease control, More seedlings with R. solani infection survived when thiophanate-methyl was used as a post-inoculation soil drench than when benomyl or chloroneb were used.     

BACTERIAL ROTTING OF APPLE FRUIT

Three bacterial isolates obtained from a rotten apple were found to produce actively spreading firm brown rots when stab-inoculated into Bramley's Seedling apples, but bacteria were not found at the front of the rot.
One isolate was a capsulated, non-motile, non-fluorescent, Gram-negative rod apparently not described previously. The name proposed for the isolate is Pseudomonas pomi. The other two isolates were the same and were non-capsulated, non-fluorescent, Gram-negative motile rods, usually with two polar flagella, and were considered to be identical with Ps. melophthora Allen & Riker (Allen & Riker, 1932).
The three isolates grew on media at pH 5.0 and in apples with juice of pH 3.5. For each isolate the square of the distance of the front of the rot from the point of inoculation of apples, was found to be directly proportional to the time after inoculation. The isolates were able to invade fruit at the stalk and eye ends and where the skin had been pricked. No apparent infection followed spraying leafy shoots or flowers of Bramley's Seedling trees with bacterial suspensions and there was no visible reaction after hypodermic inoculation of bacterial suspensions into apple shoots.     

Vitamin biosynthesis by germinating seeds at low temperature and in overmoistened soil]

The distribution of farnesene and farnesene hydroperoxide in apples of different varieties was studied. The relationship between the content of these compounds and the pathological browning of the apple surface, scald was followed. It was shown that 1) farnesene and farnesene hydroperoxide were concentrated in the cuticle; 2) there was no distinct correlation between farnesene concentration and scald, 3) there was a direct correlation between the concentration of farnese hydroperoxide and scald development; 4) the factors that inhibited farnesene oxidation (antioxidants, low oxygen concentration, mineral oils--farnesene absorbers) slowed down the scald development during apple storage.