Search

The preharvest application of Ca-containing foliar fertilizers can reduce the incidence of bitter pit (BP) in apples and improve fruit quality by increasing the Ca content and decreasing both the N content and the N/Ca ratio in fruits. In this study, we aimed to investigate the control efficacy of Ca-containing fertilizers on the incidence of BP and their effects on the Ca and N contents in bagged 'Fuji' apples by spraying foliar fertilizer containing calcium chloride (CaCl2 ), calcium nitrate [Ca(NO3 )2 ] or calcium formate [Ca(HCOO)2 ] at an early stage, five days after full bloom (DAFB) and 40 DAFB, and at a late stage, 80 DAFB and 125 DAFB.; Results: The incidences of BP were reduced significantly by 43.2-73.0%, and the efficacy of spraying at an early stage was significantly higher than that of spraying at a late stage. The Ca content of bagged apple fruits increased whereas the N content and N/Ca ratio decreased after spraying Ca-containing foliar fertilizers; however, the Ca content, N content and N/Ca ratio of apple leaves were differentially influenced.; Conclusion: Foliar fertilizer containing CaCl2, Ca(NO3 )2 or Ca(HCOO)2 can be used at an early stage to control BP in apple and improve the quality of bagged apple fruits. © 2018 Society of Chemical Industry.; © 2018 Society of Chemical Industry.

BACKGROUND: The effect of subjecting ‘Golden Reinders’ apples to a low O2 pre-treatment (LOT; 1–2% O2) was evaluated as a strategy to decrease the rate of bitter pit (BP) incidence after standard cold storage (ST). Immediately after harvest, apples were stored for 10 days at 20 °C under low O2. Thereafter, apples were cold-stored (0–4 °C) for 4 months and changes were monitored in terms of BP incidence, fruit quality traits and mineral element concentrations. RESULTS: After 4 months cold storage, LOT apples presented a 2.6-fold decrease in the rate of BP incidence (14%) versus the values obtained for standard cold-stored fruits (37% BP incidence). LOT increased flesh firmness, total soluble solids and titratable acidity as compared to the quality traits determined for cold-stored fruits. Lower cortex Ca and Mg concentrations as compared to ST apples were determined in association with LOT, 2 months after cold storage. CONCLUSION: Application of a LOT prior to cold storage may be a promising strategy to reduce the incidence of BP and preserve fruit quality, which should be further investigated. Copyright © 2009 Society of Chemical Industry

Chemometric techniques were used to analyse the effects of two preharvest calcium strategies applied to increase the calcium content and improve the quality of Golden Smoothee apples after prolonged storage in controlled atmosphere, ultralow-oxygen (CA-ULO; 1% O 2 , 2% CO 2 ) conditions. In a two-year study the strategies applied by sprays were started 10 and 60 days after full bloom (DAFB) with 10 and six calcium sprays respectively at 15 day intervals throughout the growing season. The most effective results for increasing the calcium content of the apples were attained when the calcium was applied from 60 DAFB with six sprays. Although the chamber effect and mainly the length of storage differentiate the fruits much more than the calcium spray strategies, the evaluation of the results suggests that calcium and firmness remain correlated for up to 4 months of cold storage under CA-ULO conditions. The effect of calcium decreases with storage time. Titratable acidity and bitter pit incidence correlated negatively with calcium content in year 2. Comparison of the results obtained in the two years indicates that the relationship between calcium and the quality attributes depends not only on the calcium content per se, but also on other factors such as the nutritional status. Le calcium est connu pour ses effets benefiques sur la conservation des pommes. Les effets du traitement par pulverisation des pommes golden smoothee avant leur recolte sur la composition en calcium a ete etudie. Le protocole le plus efficace est celui ou le traitement a lieu 60 jours apres floraison complete en 6 pulverisations a 15 jours d'intervalle.Le taux de calcium et la fermete de la pomme restent correlles pendant 4 mois lors de l'entreposage frigorifique sous oxygene faible (1%O2-2%CO2). L'effet du calcium diminue avec la duree d'entreposage.

BACKGROUND: Californian Granny Smith apples are very susceptible to bitter pit (BP) and superficial scald symptoms that developduringcoldstorage.Themainpreventivemeansarediphenylaminedippingand/orgaseousapplicationoftheethylene inhibitor1-methylcylclopropene(1-MCP),whichiseffectiveagainstsuperficialscaldbutnotagainstBP.Thisstudyinvestigated the efficacy of a non-chemical alternative, low-O2 (LO2) stress, in preventing these two physiological disorders. RESULTS: Application of LO2 stress at 20 ◦ C for 10 days prior to cold storage of Granny Smith apples reduced superficial scald and BP incidence and severity during 8 months at 0 ◦ C. LO2 treatments induced volatile alcohols and reduced ethylene and 6-methyl-5-hepten-2-one (MHO-on) production, thereby reducing superficial scald development after 4 months at 0 ◦ C. In addition, LO2-treated fruits had higher pectin methyl esterase (MdPME) gene expression, similar to that of 1-MCP-treated fruits, associated with their higher firmness. Conversion of MHO-on to 6-methyl-5-hepten-2-ol (MHO-ol) in LO2-treated fruits may explain the lower scald development. CONCLUSION: The ratio between MHO-on and MHO-ol might serve as an index of superficial scald severity. Reduction of BP symptoms in LO2-treated fruits could be due to accumulation of volatile alcohols in the peel tissue. c � 2010 Society of Chemical Industry

Calcium, magnesium, phosphorus and potassium were measured in residues of samples of Cox's Orange Pippin apples stored in air at 2.8-4.4°C, removed at intervals and extracted with either distilled water or 75% ethanol. Little potassium was left in the residue after extraction with water, but 15% remained after extraction with ethanol. More phosphorus (85%) was extracted by ethanol than by water. Calcium and magnesium became less soluble during storage. Higher proportions of calcium and magnesium were removed by water than by ethanol initially but, whereas these differences between solvents remained fairly constant for calcium, those for magnesium decreased. When decreases in proportions of soluble calcium and magnesium were small little bitter pit and no breakdown developed in the fruit. Little change in the proportions of mineral constituents, other than phosphorus occurred whilst the fruit was on the tree during the 6 weeks before harvest. Proportions of phosphorus remaining in the residues after extraction with either solvent diminished, especially during the 3 weeks before harvest when apples had been sprayed with calcium nitrate. Otherwise orchard treatments had little effect on the proportions of mineral constituents that could be extracted. Although symptoms developed when the proportion of calcium insoluble in water rose above 40% of the total, some increases in susceptibility to bitter pit caused by orchard treatment or storage conditions were not associated with differences in insoluble calcium.

The distribution of calcium at harvest, its subsequent redistribution within the fruit during storage in air at 2.8°C and bitter pit development in samples of Cox's Orange Pippin apples picked at intervals during September and October were investigated. The distribution of calcium in the fruit changed on the tree and during storage. The percentages of pitted apples, assessed in January, were poorly related to calcium concentrations in the whole fruit or in any fruit zone at harvest. Redistribution of calcium from the mid and outer cortical tissues to the core zone was followed, at longer intervals over successive picks, by the appearance of bitter pit lesions. The earliest-picked sample was less affected by bitter pit than samples picked later in September. The least bitter pit occurred in samples picked in October, after the climacteric rise in respiration, and these fruits were apparently less subject to fluctuations in calcium concentrations during storage.

Apples affected with bitter pit had higher levels of most volatile organic compounds than sound fruit. Reducing the susceptibility of fruit to pit by the application of calcium sprays also resulted in reduced levels of most volatiles. However, it appears that the volatiles are not causatively associated with pit as they did not cause an increase in the incidence of pit when added to the fruit. A significant positive correlation between pre-harvest levels of acetaldehyde and development of pit was found but the extent of the remaining variation precluded the use of the method for commercial grading of fruit for pit susceptibility.

Separation and analyses of sound Cox's Orange Pippin apples and those with disorders, after storage for 18 weeks at 3.3°C, revealed that sound apples had the lowest, apples rotted by Gloeosporium spp slightly higher, apples with bitter pit higher, and apples affected by breakdown even higher proportions of calcium in the residue after extraction with distilled water, although total concentrations of calcium in these samples were in the reverse order. Lower proportions of calcium, magnesium and potassium were extracted by 75% ethanol from fruit with breakdown than from sound apples, and similarly lower proportions of magnesium, and magnesium and potassium were extracted by water from apples with bitter pit and breakdown, respectively. Proportions of phosphorus extracted by either solvent were not obviously related to disorders. The high concentration of magnesium in pitted tissue, in relation to that in adjacent sound tissue, was evenly divided between the fractions soluble and insoluble in water, but that of calcium was mainly in the insoluble fraction.

Analyses of apples, of various varieties and from many sources, affected by lenticel blotch pit and/or watercore showed that calcium concentrations in the fruit were usually extremely low. The severity of lenticel blotch pit, either on the tree or during storage, increased with decreasing concentrations of calcium and/or increasing concentrations of potassium. Split and cracked apples had lower concentrations of calcium or higher concentrations of potassium than sound fruit from the same sources. The disorders usually occurred when mean concentrations of calcium in bulked random samples of fruit fell below 4 mg 100 g−1 fresh wt and lenticel spotting was noted on apples with concentrations at this level. Incidences of these disorders in the orchard therefore indicate that the fruit is likely to develop bitter pit and breakdown during storage.

Calcium concentrations in individual apples grown in Australia, South Africa and New Zealand, and affected by lenticel blotch pit, were low (1.5–3.1 mg per 100 g fresh weight). Bulked samples of Cox's Orange Pippin fruit grown in 19 orchards in New Zealand and imported in 1971 and 1974 had, on average, lower concentrations of phosphorus and nitrogen than is usual in this variety grown in England. Comparisons of concentrations of calcium and the incidence of bitter pit in these samples indicated a similar threshold of 5.5 mg per 100 g above which the disorder was unlikely to occur and which is similar to that found for bulked English Cox apples. Although bitter pit symptoms were visible externally in many apples, about twice the number were found to be affected by the disorder when cut.

The problems of relating low fruit calcium concentrations in stored apples to the development of bitter pit lesions are reviewed. They include nomenclature, anomalous fruit analyses, variability in the susceptibility of apples to pitting and in the time and rate of pit development, effect of harvest date, accumulation of calcium in pitted tissue and the apparant translocation of calcium during storage from the core into zones of tissue most at risk. Recent evidence suggests that bitter pit lesions are induced by the removal of calcium from these outer zones to meet intermittent demands by the core tissue.

Data for bulked samples of ungraded Cox's Orange Pippin fruit obtained from many sources over a period of 18 years show that there is a general inverse relationship between mean mass per apple and mean calcium concentration. Part of the scatter around the regression curve was accounted for by differences between years but there were larger differences between samples of the same size picked from different orchards in the same year. Even with the most favourable conditions the observed samples with mean mass per apple greater than 150 g had less than 5 mg Ca/100 g when no calcium sprays were applied and in general most samples with mean masses per apple greater than 110g were likely to have concentrations of calcium below this and hence were liable to develop bitter pit. Fruit calcium level was a more important determinant of liability to bitter pit than was mean mass per apple. Although there was some evidence of the same relationship between calcium concentration and mass when apples from the same tree were analysed individually other factors often negated it. Two- to three-fold differences in calcium concentration were observed in individual apples from the same tree.

Calcium concentrations in median transverse sections of Cox's Orange Pippin apples stored at 4°C in either air or 1.25% oxygen (< 0.3% carbon dioxide) were measured at weekly intervals for 25 weeks. Large fluctuations of calcium concentration occurred in all zones of fruit from both stores throughout storage. The low oxygen atmosphere had little effect on the concentration of calcium in the cortex and redistribution of calcium from the core zone to the outer zones other than causing a decline in calcium concentration in the peel towards the end of storage when calcium concentration was generally rising in the peel of the air-stored fruit. The results are discussed in relation to the suppression of calcium deficiency disorders by low oxygen storage and to earlier experiments on calcium redistribution and bitter pit development.

Transverse calcium redistribution from the cores to the outer zones of the fruit was interrupted for a short period when calcium was imported by the cores of both Cox and Spartan apples, especially at 3.5°C. Bitter pit lesions developed in mid and outer cortical tissues of Cox fruit stored at 3.5°C 2 to 4 weeks after calcium concentrations in these zones were reduced. Redistribution of magnesium from the outer zones to the cores of Spartan apples occurred during storage at 3.5°C but was inhibited at 0°C. Redistribution of magnesium in Cox's Orange Pippin apples was mainly from inner cortex to the core and outer zones at 3.5°C and from central to outer zones at 0°C, but immediately low temperature breakdown become evident at 0°C, magnesium was transferred from the peel and core to the affected zones. The redistribution of phosphorus to the cores, which occurred in Spartan apples (resistant to low temperature breakdown) stored at either 3.5°C or 0°C was barely evident in Cox fruit (susceptible to low temperature breakdown) stored at 3.5°C and did not occur at 0°C. Irrigated grass compared with overall herbicide soil management increased the proportion of calcium in the core zones of both Cox and Spartan apples and the proportion of magnesium in the core zone of Spartan apples at harvest. Irrigated grass management also increased the rate of calcium redistribution in Cox and Spartan fruit during storage and altered magnesium redistribution in Spartan apples stored at 0°C.

There is evidence that the incidence of each of three storage disorders of Cox's Orange Pippin apples (senescent breakdown, low-temperature breakdown and bitter pit) is affected by the mineral composition of the fruit. These effects have been studied by comparing initial average compositions of bulk samples with the storage behaviour of bulk replicates and by experiments with individual apples in which apples were analysed after their storage record was known. It is suggested that if the Ca level in an apple is less than 3 mg/100 g fresh weight it will be liable to senescent breakdown at an early stage of storage. A P concentration of less than 8 mg/100 g may have the same result even if the Ca level is high. Low-temperature breakdown is less likely in apples with high levels of K, P and Mg than in apples with low levels of these elements. The results confirm that low average Ca concentration is associated with bitter pit. It is suggested that if the average Ca concentration exceeds 5 mg/100 g fresh weight the sample will probably be free from this disorder. The relationship between Ca and bitter pit in apples stored individually was not clearly defined.

The amount of calcium in mature apples appears to be related to certain storage disorders. For Cox's Orange Pippin a difference of 2 mg in a total calcium content per fruit of about 5 mg can make the difference between good and bad keeping. Most of the calcium moves into the fruit during the first few weeks of its development (approximating to the period during which the cell walls are being formed). Thereafter (during the period of cell expansion) the movement of calcium is no longer in one direction only, and as much as 1 mg may move out of the fruit. This may be of the same order of magnitude as that contributed by calcium sprays, which are now commonly applied to improve storage quality. The factors affecting the movement of calcium into or out of apples are not known, but the limited evidence available suggests that movement of calcium out of the fruit may occur during periods of abnormally dry weather. These are the conditions which are usually associated with the occurrence of bitter pit.