Effect of part-tree flower thinning on fruiting,vegetative growth and leaf photosynthesis in ‘Cox’s Orange Pippin’ apple

Flower clusters were removed at full bloom from ten year old ‘Cox’s Orange Pippin’ trees on M.9 rootstocks, over the whole tree, on alternate branches or on whole sides. Mean fruit weight per tree at harvest was linearly dependent on leaf area per fruit and on light interception per fruit, both relationships accounting for over 90% of the variance. These relationships did not differ between treatments, implying either a mobile pool of carbohydrate or photosynthetic adjustment within the tree to crop load. Measurements of leaf photosynthesis in July and September showed no statistically significant differences in photosynthetic rate of spur or extension shoot leaves on bearing or non-bearing branches. Although the treatments caused no overall effects on shoot growth or leaf area per tree, sides of trees without fruit had greater leaf area and shoot growth than did sides bearing fruit. Fruit mineral composition and percentage dry weight were not affected by treatment except where the treatments significantly altered fruit size. In the following spring, although the treatments did not affect the total number of flower buds produced, branches that were deflowered in the previous spring carried significantly more flower buds than did branches which had cropped.     

The effect of boron upon leaf development and growth of the apple cultivar ‘Cox’s Orange Pippin’

One-year-old ‘Cox’s Orange Pippin’ trees planted in pots in sand culture in the spring of 1970 were (during the growing seasons of 1970–72) watered with nutrient solutions containing 0, 0.12, 0.23, 1.2, 3.5 or 7.0 mg boron per litre.

With increasing boron supply, the boron concentration of the leaves increased, the growth of current year’s shoots and to some extent of other plant parts increased, and summer leaf-fall and the occurrence of necrotic leaf spots (‘Cox spots’) decreased. The percentage of healthy leaves was greatest when boron in leaf dry matter was about 30 ppm.

In 1972 the trees with highest boron supply suffered from incipient boron toxicity and increased incidence of ‘Cox disease’ flowering was delayed, and the percentage of dead buds was increased. In the latter part of the summer the leaves curled upwards, turned purple and became brittle.     

The effect of summer pruning and nitrogen on growth,cropping and storage quality of Cox’s Orange Pippin apple

Pruning in late summer was compared with winter pruning on mature 23-year-old spur pruned trees of Cox’s Orange Pippin on M.2 rootstock. Two nitrogen treatments were superimposed, namely a standard dressing of 126 units N (sulphate of ammonia) applied in March as compared with 288 units N (nitrate of soda) applied in mid-August at the time of summer pruning. Summer pruning reduced trunk girth increment, advanced blossom development, increased the amount of red colour on the fruits and drastically reduced the incidence of bitter pit in stored fruit. The treatments did not affect cropping. Nitrogen treatments had no overall effect upon the incidence of bitter pit, but in the first season, when bitter pit was most prevalent, high levels of N applied in August reduced the amount, a similar trend being recorded the following year.     

The Relation Between Time of Picking and Storage Disorders in Cox’s Orange Pippin Apple Fruits

In four successive seasons. Cox’s Orange Pippin apples were picked at weekly intervals and stored under various conditions to assess the effect of time of picking on wastage from different causes.

Mean fruit weight increased by up to 20% over the 6 to 10 weeks of the picking periods.

The maturity of the fruit when picked was assessed by following the respiration pattern of samples kept at 12°C.

The results for successive pickings of fruit kept at 37°-38° F. (2.8°-3 ·3° C.) (normal cold storage temperature for Cox) and all removed from store at the same time, showed more core flush in early-picked apples, and more senescent breakdown and rotting in late-picked apples. There was no sudden change in liability to any of these disorders which could be associated with any particular stage of maturity. There were no consistent effects of time of picking on the amount of bitter pit or on weight loss during storage.

Storage at 32° F. (o° C.) (below the recommended temperature for the storage of Cox’s Orange Pippin) resulted in low temperature breakdown. This disorder tended to be less severe in apples picked just before the climacteric rise in respiration rate.

It is concluded that, for any particular orchard, picking date should be based not only on maturity as judged by colour and size, but on the expected liability of the fruit to disorders, such as core flush and rotting due to Gloeosporium, and on the type and period of storage required.     

An Experiment in Pruning Cox’s Orange Pippin Apple Trees in Alternate Years

Five pruning treatments were compared on Cox’s Orange Pippin on M.II rootstock, viz.

1. Open-centre tree, established-spur pruned

2. Open-centre tree, renewal-pruned

3. Delayed open-centre tree, established-spur pruned

4. Delayed open-centre tree, renewal-pruned

5. Regulated-pruned tree.

At 15 years, secondary pruning treatments were begun and carried on for a further 7-year period, the trees being pruned by the same methods but either annually or in alternate years. Differences in growth and cropping between trees pruned to open-centre and delayed open-centre shapes were small, but open-centre trees cropped more heavily than did delayed open-centre trees when renewal-pruned, probably on account of their greater branch spread. The method used in pruning the laterals had an effect upon cropping during the first 10 years. At the end of the trial there was no effect of either primary or secondary treatments upon trunk girth, neither was there a significant difference in girth increment between the secondary treatments. Almost the same amount of wood was removed from trees pruned in alternate years as from those pruned annually, but a greater proportion of old to new wood was removed from trees pruned in alternate years. Pruning in alternate years increased the cropping of established-spur pruned trees but not with regulated or renewal-pruned trees. There was no consistently adverse effect upon fruit size but, when a year of heavy setting followed a winter when the trees were left unpruned, fruit size was reduced and early fruit thinning would have been necessary to lessen the proportion of fruit in the two smallest size grades. With this variety fruit colour was unaffected by pruning in alternate years.     

The Cuticles of Cox’s Orange Pippin Apples from a Manurial Trial

The cuticles of fully-grown Cox fruits from a manurial trial were examined quantitatively. No differences attributable to fertilizer treatment were found in the weights of the cuticles per unit area of surface nor in their major components. This implies that the variations in susceptibility of fruits to storage rots that have been associated with nutritional differences in the manurial trial are not determined by variations in cuticle thickness or composition.     

Fruit-Thinning Effects on the Development and Storage Quality of Cox’s Orange Pippin Apple Fruits

Fruit-thinning treatments were applied in the three seasons 1963–65 to Cox trees to investigate the relationships between leaf : fruit ratio, fruit size, cell volume and cell number, and the incidence of rotting and disorders following air storage at 2·8° C. (37° F.) and o° C. (32° F.). Progressively more severe thinning was required, sis fruit development proceeded, to obtain a similar increase in fruit size. This declining response to thinning was accompanied by a progressively smaller increase in the cell numbers of fruits as the treatments were delayed. Thinning also caused an increase in cell-enlargement rate but the magnitude of the response varied between different experiments and did not appear to be related to the developmental stage at which the treatment was applied.

The larger fruits from thinned trees were more susceptible to bitter pit, breakdown, and rotting caused by Gloeosporium perennans, but were less susceptible to low-temperature injury than fruits from unthinned trees. Bitter-pit incidence was related to fruit size within each treatment and was more severe in fruit where the ratio between the potassium and calcium concentrations was high. Low-temperature injury was associated with fruit with low dry matter and potassium contents. Susceptibility to this disorder and to rotting was also influenced by fruit maturity as measured by the progress of the climacteric rise in respiration rate. There were no marked relationships between storage disorders and the numbers or size of cells in fruits produced by the various treatments included in these experiments.     

Prediction of storage quality of ‘Cox’s Orange Pippin’ apples from nutritional and meteorological data using multiple regression models selected by cross validation

Summary

An experiment was carried out over a six year period to relate the storage quality of ‘Cox’s Orange Pippin’ apples to the mineral composition of leaves, fruitlets and fruits and to the climatic conditions during development. The apples were sampled from 24 orchards over a wide geographic area. The extent to which physiological disorders, bitter pit and low temperature breakdown (LTB), and quality attributes, greenness and firmness, of stored fruit could be predicted either before or at harvest was determined. For each response variable, a short-list of up to 12 potential explanatory variables was selected from an initial set of up to 54 possible explanatory variables, using stepwise regression techniques. Predictive models were generated by selecting variables from the initial short-list using a cross validation technique. The average incidence of bitter pit in controlled atmosphere (CA) storage at 1.2% O2 (<1% CO₂) was 4% compared with 12% for similar samples stored in air. Predictive models accounted for up to 67% of the variance in bitter pit in air-stored fruit but the percentage was lower (39%) for fruit stored in CA. The concentrations of calcium and potassium in fruit were particularly important for predicting bitter pit in air-stored fruit but less so for fruit stored in CA where more explanatory variables were required for prediction. Fifty one per cent of the variance of LTB in fruit stored in CA was accounted for by a nine-variable model incorporating three climatic variables. A simple three-variable model (leaf nitrogen concentration, harvest firmness and fruit dry weight) accounted for 67% of the variance in ex-store firmness and the addition of other nutritional and climatic variables increased the percentage variance accounted for to 76%. Seventy-one per cent of the variance in the greenness of fruit after CA storage was accounted for by a six-variable model. The possible physiological significance of the explanatory variables in each model is discussed.     

The Effects of Fruit Thinning on the Development of Cox’s Orange Pippin Apples in Relation to the Incidence of Storage Disorders

Severe hand thinning of fruitlets on Cox’s Orange Pippin trees five weeks after full blossom led to a doubling of fruit weight by harvest. Although the rate of cell division was stimulated slightly, the larger fruit size was due mainly to an increased rate of cell enlargement.

The respiration rate of whole fruits was slightly higher after thinning and the onset of the climacteric rise was advanced. Respiration per cell was correspondingly higher in the larger cells of the thinned fruit and respiration per unit protein was similar to that of fruit from unthinned trees.

Potassium, magnesium, and phosphorus contents, expressed on a fresh weight basis, were higher in the cortical tissue of the thinned fruits. Calcium per unit fresh weight was unaffected by thinning and the ratio of calcium to cell surface remained relatively constant throughout development in both types of fruit.

Senescent breakdown and bitter pit developed during storage only in the thinned fruit. Slight differences in the incidence of rotting and low temperature breakdown between the two types of fruit are attributed to the effects of maturity rather than of fruit size.     

Pruning affects carbohydrate accumulation in the shoots and leaves of ‘Precoce de Tyrinthe’ apricot

Summary

This study was conducted in Mut-Mersin, Turkey, to determine the effects of various times of pruning (no pruning = control; only summer (July, August, or September) pruning in 1994 and 1995; only winter pruning in 1995 and 1996; both summer + winter pruning in 1994-1995 and 1995-1996) on the carbohydrate contents of annual shoots and leaves of young ‘Precoce de Tyrinthe’ apricot trees. Although carbohydrate content in annual shoots was highest in the control trees during the first year, the summer + winter pruning gave the highest values in the second year. In 1995 total sugar and sucrose contents of the leaves was greatest following winter pruning, but starch content was higher in the leaves of control trees. The content of reducing sugars was greatest in leaves of trees pruned in both September + winter. In 1996, levels of total sugars and starch were highest following September pruning, starch content was highest in the control, and; reducing sugars in the leaves were highest following August + winter pruning.     

The long-term effects of pre-planting soil fumigation on the growth and cropping of cvs Laxton’s Fortune and Cox’s Orange Pippin on M.2 rootstock,planted on land affected with a replant disease of apple

Soil fumigation of land affected by apple replant disease, using chloropicrin at 281 1 ha^-1 before planting-out, caused increases in shoot numbers, trunk girth and of 35% in total crop accumulated over 10 years for cv Cox’s Orange Pippin on M.2 rootstock. Chloropicrin at 1121 ha^-1 gave rise to a smaller response, and DD at 5621 ha^-1 was ineffective. Cv Laxton’s Fortune on M.2 showed little response to any treatment.     

Short-term effects of changes in soil management and nitrogen fertilizer application on ‘Bramley’s Seedling’ apple trees.

Soil managment in a ‘Bramley’s Seedling’ orchard, established in a system of herbicide treated tree rows and mown grass alleys, was changed to provide three treatments: complete grass cover, overall herbicide and a continuation of the existing system. Differential rates of N fertilizer (nil, 62.5 kg ha-1) were applied to each soil management regime. In comparison with herbicide strips, complete grass was intensely competitive, particularly with nil application of N fertilizer, reducing tree growth and yield and greatly decreasing leaf N. Leaves from trees in complete grass (nil N) plots contained higher concentrations of P, K and B but lower ones of Ca, Mn and Cu. Compared with the change from herbicide strip to complete grass management, effects of changing to overall herbicide were smaller. There were slight increases in leaf N concentration but no increases in tree growth or fruit yield. Leaf Mn concentration was increased in overall herbicide. Although application of N fertilizer to grass plots increased leaf N concentration by 0.4% and the three-year girth increment, yield was less than that of trees in herbicide strips. Nitrogen fertilizer applied to herbicide strips or overall herbicide plots slightly increased leaf N content but there was no effect on yield or girth increase. Applying N fertilizer to complete grass plots reduced the concentration of P, K and B in leaves but increased leaf Ca, Mn and Cu.     

Improvement of fruit quality and storage potential of ‘Braeburn’ apple through deficit irrigation

Summary

We explored the potential of deficit irrigation (DI) applied at different times during the growing season for improving fruit quality and storage potential of ‘Braeburn’ apple growing in a commercial orchard. Because DI often reduces fruit size, effects of fruit size on fruit quality were also examined. The irrigation treatments were: commercially irrigated control (C), early deficit irrigation (EDI) applied from 63 to 118 d after full bloom (DAFB), and late decifit irrigation (LDI) applied from 118 DAFB to final harvest on 201 DAFB. Both EDI and LDI improved fruit quality in terms of increases in: dry-matter concentration (DMC) at harvest, flesh firmness, total soluble solids, and total soluble sugars both at harvest and after storage. The DI fruit had less weight loss during storage than did C fruit. Deficit irrigation affected the concentrations of a few individual aroma volatiles but not total volatile concentration. Incidence of physiological disorders was not affected by irrigation treatments. Mean fruit weight was lower in DI than in C but the difference was not significant. Among the quality attributes studied, only firmness and DMC were affected by fruit size with their values being higher in smaller fruit.     

Competition for water between inflorescences and leaves in cut flowering stems of Grevillea ‘Crimson Yul-lo’

Summary

Grevillea cv. ‘Crimson Yul-lo’ has large bright red terminal inflorescences on leafy stems and has recognised commercial potential as a cut flower crop. A major limitation is its relatively short vase-life, often terminated by early wilting of the inflorescence despite apparently turgid leaves. An investigation of the water relations of cut Grevillea ‘Crimson Yul-lo’ stems revealed that the water potential of inflorescences on intact stems in vases was significantly higher (i.e., less negative) than that of leaves from day-0 to day-3 of vase-life. Thereafter, the water potential of inflorescences declined more rapidly than that of leaves, accompanied by visible wilting of the tepals and styles of individual florets. Removal of leaves from the stems reduced both water uptake and water loss, and delayed the onset of a negative water balance in the inflorescence. Bagging of entire stems, leaves only, or inflorescences only, with micro-perforated plastic film to reduce transpiration, reducing leaf number to reduce leaf area, or supplying abscisic acid to reduce leaf stomatal aperture, all aided relative fresh weight retention by stems and extended vase-life. Four or six leaves on a stem caused greater loss in inflorescence water content than zero or two leaves. Considered collectively, these findings show that competition for water between the inflorescence and the leaves in cut Grevillea ‘Crimson Yul-lo’ stems contributes to the onset of inflorescence wilting and their short vase-life.     

Evidence of Clonal Variation and Latent Virus Effect on the Vigour of Cox’s Orange Pippin Apple Trees on M.9 Rootstocks

Apple trees on M.9 EMLA rootstocks free from known virus are at least 50% larger than those on M.9a containing latent virus. Evidence is presented that about half of this difference can be attributed to clonal variation and the rest to virus effects.     

The effect of gibberellins and cytokinins on fruit development of Bramley’s Seedling apple

Two applications of a 1 : 1 mixture of gibberellins A₄ and A₇ to either frost damaged or artificially decapitated Bramley's Seedling apple flowers resulted in increased fruit set and yield. It also increased the crop in an orchard without pollinators. Gibberellic acid was not effective. The addition of cytokinins had no beneficial effects and caused malformation.     

The Effect of Frequent Spraying with Calcium Nitrate Solutions on the Mineral Composition and the Occurrence of Bitter Pit of the Apple Cox’s Orange Pippin

In several commercial orchards the percentages of Ca and K in the leaves and fruit of the cultivar Cox’s Orange Pippin were determined at intervals during one or more years. The values for a series of untreated trees were continually compared with those of a comparable series of trees which were sprayed at about seven-day intervals with a Ca(NO₃)₂ solution. At the end of each experiment the fruit was placed in storage and later examined for the incidence of bitter pit.

The Ca contents of leaves and fruit and the quotient (K+Mg)/Ca in the leaves of untreated trees showed only a moderate relationship with the percentage of bitter pit. The K content of the fruit was more closely correlated, however.

The level above which much bitter pit was unlikely to occur was found to be approximately 7.5–8 mg Ca in a fruit of 140 g fresh weight.

The total amount of Ca in the untreated fruit increased in a rather regular and comparable fashion in the various experiments. The rate of increase was somewhat higher during the first period of development, until the fruit reached about 20–40 g in weight, than during its subsequent growth.

Spray treatments increased the Ca content of the leaves by 0.2–0.5% of the dry weight; a maximum of 4 mg Ca was added to the fruit, an increase of 47% on the basis of the amount already present. In general the Ca level increased progressively during the season with successive spray applications, and 9–15 sprays reduced bitter pit incidence to about 5%.

The permeability of the fruit tissue to ions diminished as a result of the sprays, and it is suggested that an increase in cell membrane permeability may be involved in the development of the disease.

For commercial orchards, more frequent sprays may need to be applied than are recommended at present to provide effective control of bitter pit.     

Response of the phenylpropanoid pathway to Venturia inaequalis infection in maturing fruit of ‘Braeburn’ apple

Summary

This study investigated the activities of key enzymes in the phenylpropanoid pathway and the accumulation of phenolic products in apple peel in response to infection with Venturia inaequalis [(Cooke) G. Wint.]. We compared healthy apple peel with apple peel showing symptomatic scab lesions, and with peel tissue from 1 – 2 mm around the scab lesions in fruit 1 month before maturity [140 d after full bloom (DAFB)] and at physiological maturity (175 DAFB). Infection with V. inaequalis enhanced the synthesis of some phenolic compounds. Compared to healthy peel, scab lesion tissue had ≤ 3.1-times higher hydroxycinnamic acid content, ≤ 1.3-times higher dihydrochalcone content, and ≤ 3.9-times higher flavan-3-ol content. Scab lesions showed slightly higher phenylalanine ammonia-lyase, chalcone synthase, chalcone isomerase, flavonol synthase, and dihydroflavonol 4-reductase activities. The total amount of phenolics remained relatively stable between the two sampling dates, except for epicatechin and caffeic acid which decreased in amount toward fruit maturity, and levels of catechin which increased in more mature fruit. During fruit maturation, only chalcone synthase and chalcone isomerase activities decreased in all tissues examined. This study showed that the phenylpropanoid pathway in apple fruit peel changed significantly following infection with the apple scab pathogen.     

Effects of different rootstocks and training systems on the mineral composition of ‘Delicious’ apple leaves

Leaf mineral composition as affected by different rootstocks, cultivars, training systems and their combinations was measured during 1987 and 1988. Trees on M.7 had significantly higher concentrations of N, P and Fe, whereas those on MM. 106 maintained higher values of K, Ca, Mg and Mn during both years. Between cultivars, Red ‘Delicious’ showed greater accumulation of N, P, Mg and Fe but K and Cu levels were found to be more in Starking ‘Delicious’. All mineral nutrients except Ca and Mg accumulated more in spindle-bush trained trees than those under modified central leader system. The Mineral composition of Starking ‘Delicious’ grafted on M.7 rootstock and trained as a spindle bush produced the best yield efficiency and fruit quality, and fell within the normal range.