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Massimo Tagliavini and Bruno Marangoni

Most deciduous fruit crops in Italy are grown in the north and especially in the eastern part of the Po River Valley (mainly in the Emilia Romagna and Veneto regions) and in the Adige River Valley (South Tyrol and Trento provinces). Soils in the wide Po River Valley, where pear (Pyrus communis), peach and nectarine (Prunus persica), kiwifruit (Actinidia deliciosa), plum (Prunus domestica and P. insititia), apricot (Prunus armeniaca), cherry (Prunus avium), and apple (Malus domestica) are grown, are alluvial, generally fertile, fine textured, alkaline, often calcareous and well enriched with Ca. Apple plantings are concentrated in the Adige Valley and located on a variety of soil types, including sandy loam, loamy sand soils or sandy clay, sometimes calcareous. Integrated fruit production is gaining importance and represents more than 80% of apple production in South Tyrol and about 60% of peach and nectarine production in Emilia Romagna. Under these conditions, the main objectives of mineral nutrition are to reconcile production and environmental concerns (minimize nutrient leaching, soil pollution, volatile emissions). In particular, fertilization aims to improve external and internal fruit quality and storage ability, reduce production costs, maintain soil fertility, avoid nutrient deficiency and excess and control tree vigor. Nitrogen applications have strongly decreased in recent years and there is a need to improve the efficiency of N fertilizers while avoiding deficiencies. Research is focussing on application technology, timing of N uptake, internal cycling of N and methods for assessing the need for N application (e.g., using estimates of native soil N availability). Early diagnosis of bitter pit is recommended for guiding applications of Ca sprays. Iron deficiency and chlorosis is a major problem in pear, peach and kiwifruit grown in alkaline and calcareous soils and Fe chelates are usually applied annually to the soil or to the canopy. Current research is focused on agronomic means for controlling the problem and on developing rootstocks tolerant to Fe deficiency.

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Duane W. Greene

`Gardiner Delicious'/MM.lO6 apple (Malus domestics Borkh.) trees were initially sprayed in 1985 with paclobutrazol (PB) at 250 mg.liter-1 at tight cluster and again on 10 and 25 June and 29 July. From 1986 through 1988, PB sprays of 85 or 100 mg·liter-1 were applied at either petal fall (PF) + 2 or PF + 4 weeks and one to two additional sprays were applied per year when growth resumed. Promalin was applied to one group of trees that received PB starting at PF + 2 weeks. PB reduced terminal, lateral, and total shoot growth the year of application and in subsequent years. Although average shoot length of lateral and terminal shoots was reduced, the greatest reduction in growth occurred because PB prevented spurs from growing into lateral and terminal shoots. Compared to unsprayed trees, PB reduced pruning time in all 4 years by 23% to 70%. PB increased bloom only the first year after application, but increased fruit set for 2 years due to a carryover effect. Application of PB in 1985 caused a reduction in fruit size, sometimes in soluble solids concentration, length: diameter (L : D) ratio, and pedicel length. Promalin either overcame the reduction in the ratio or increased it in 1986. Reduced rates of PB in subsequent years caused few adverse effects on the fruit. PB increased flesh firmness when applied at PF + 2 weeks but not at PF + 4 weeks. Trees treated with PB produced fruit with higher flesh Ca and less bitter pit, cork spot, and senescent breakdown following regular air storage. Chemical names used: ß -(4 -chlorophenyl)methyl α -(1,1-dimethylethyl) -1H-l,2,4-triazole-1-ethanol (paclobutrazol, PB); gibberellins A4+7 plus N-(phenylmethyl) -1H-purine-6-amine (Promalin).

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Roy K. Simons, Frank N. Hewetson, and Mel Chih-Yu Chu


Anatomical changes in ‘York Imperial’ apples were studied sequentially throughout the growing season to discover tissue variances occurring within the fruit at different stages of development. Several abnormalities have occurred during fruit enlargement, some of which may develop into corking disorders, including bitter pit and cork spot. Cellular abnormalities appeared contiguous to large lacunae, senescing vascular bundles or in tissues where cell proliferation was apparent.

Abnormalities adjacent to necrotic vascular bundles in the outer cortical region were apparent early in. the life of the fruit, by 14 days after full bloom. Changes in cellular structure continued 65 days after full bloom from the outer cortex to the epidermis, and extended to the bundles underlying this area. Cell division had ceased, and the cell walls were thick with a distinct demarkation line between the affected and unaffected tissues. Tissues of the basin region were susceptible to the development of corking disorders, while senescent vascular bundles and meristematic tissues were evident within the core line.

Necrosis of vascular bundles extended along the core line in the fruit apex 95 days after full bloom, and tissue proliferation occurred by 115 days. Fruit development 126 days after full bloom revealed large lacunae in the outer cortex and extreme cell proliferation resembling callus tissue in the cavity at the point of fruit-pedicel attachment.

Origin of corking disorders, visible on fruit nearing maturation (112 days after full bloom), could be traced from tissue anomalies in the outer cortex. The spots appeared irregular in outline, yellowish-green in color; while a glossy, scalded appearance surrounded this area. Meristematic activity of the parenchyma cells along the core line was apparent 126 days after full bloom.

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R.E. Byers, D.H. Carbaugh, and L.D. Combs

Prohexadione calcium applied as a series of three applications starting soon after petal fall to `Fuji'/M.9 apple trees reduced the number of pruning cuts, pruning time, pruning weight per tree, current season's shoot length, individual shoot weights, and increased number of nodes on the lower 40 cm of shoots. Fruit diameter, soluble solids, starch, or individual fruit weights were not affected by Apogee sprays. Fruit color and firmness were slightly increased in only one experiment. Growth suppression appeared to be greater on trees cropping more heavily. When trees were more heavily thinned, less shoot growth control was achieved. Apogee applied at 250 mg/L in three applications caused a significant increase in fruit set when compared to the control. Alone Vydate, Carbaryl+Oil, or Carbary+Accel+Oil caused fruit thinning, but neither ethephon nor shading 3 days caused significant thinning. Apogee did not influence results of chemical thinners when applied between the first and second Apogee applications. The 10% and the 27.5% Apogee formulations gave similar shoot growth inhibition when applied with Regulaid or Oil+Silwet L-77. When using hard water (well water), the 27.5% Apogee formulation was not as effective as the 10% formulation. The 10% Apogee formulation has more NH4SO4 than the 27.5% formulation w/w; NH4SO4 is used to prevent inactivation of Apogee by calcium and other cations when hard water is used for spraying. The addition of CaCl (frequently used to reduce bitter pit and corkspot disorders) to the 27.5% Apogee formulation caused poorer growth control than with hard water alone. When Apogee was used at 125 mg/L, the addition of NH4SO4 restored the effectiveness of the hard water+CaCl mixture. Alone the additives NH4SO4, Ca Cl, Regulaid, and/or Oil plus L-77, had no effect on tree growth. Apogee plus L-77+Oil provided additional growth suppression when compared to Apogee+Regulaid. In 1998, three applications of Apogee (63 mg/L) or ethephon (135 mg/L) did not affected shoot growth of `Fuji'/M.9 trees at these low rates. Combinations of Apogee and ethephon gave good control of tree growth. Flowering and fruit set were not promoted by any of these applications.

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Frank J. Peryea

Postbloom zinc (Zn) sprays are replacing dormant and postharvest sprays as the primary means for applying Zn in commercial apple (Malus ×domestica) orchards. We conducted a multiyear field study comparing the phytoavailability of Zn in 11 commercially available Zn spray products, plus reagent-grade Zn nitrate and a water-sprayed control, applied postbloom at identical Zn concentrations to `Golden Delicious' apple trees. Two sprays were applied per season (mid-May and mid-June), at per-spray rates of either 0.5 lb/acre in 2000 or 1.0 lb/acre in 2001 and 2002. No sprays were applied in 2003 in order to evaluate carry-over effects. The Zn sprays had no effect on fruit number, bitter pit or russeting, or on leaf green color. Zinc concentrations of detergent plus acid-washed leaves (a procedure used to remove surface residues of the Zn sprays) sampled in August and of unwashed winter buds sampled the following January were used as indices of tree Zn status. Leaf Zn concentration generally increased in the order: Zn phosphate < Zn oxide = Zn oxysulfate < chelated/organically complexed Zn ≤ Zn nitrate. There was little consistent difference among chelated and organically complexed Zn products. Leaf Zn concentration varied considerably between seasons, and was not related to Zn application rate. All of the Zn sprays increased leaf Zn concentrations to desirable levels. Because the inorganic Zn-based products typically are substantially less expensive per unit of Zn, it may be less costly and just as effective to use a higher rate of an inorganic Zn product as to use a lower rate of a more expensive chelated or organically complexed Zn product. On the other hand, use of low rates of highly phytoavailable Zn products minimizes release of the nutritionally essential but potentially ecohazardous metal into the environment. There was no detectable lasting effect of the three previous seasons of Zn sprays on leaf Zn in 2003. Similarly, there was no detectable effect in any year of the Zn spray treatments on bud Zn concentration the following winter. These results suggest that the amount of Zn supplied by the sprays at the tested rates was insufficient to promote substantial Zn accumulation within the trees, thereby validating the recommendation for annual application of Zn nutritional maintenance sprays.

Open access

Bernardita Sallato, Matthew D. Whiting, and Juan Munguia

hypodermal layers ( Fig. 1 ). Although GS resembles other apple physiological disorders, such as bitter pit (BP), blotch pit, and other cork-type disorders, GS is distinguished for its green color in early stages and that it develops exclusively preharvest

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CHLORIDE SPRAYS CONTROL BITTER PIT IN `HONEYCRISP' APPLES `Honeycrisp' is a new apple variety that is generating both consumer demand and high prices for producers. `Honeycrisp' is highly susceptible to the calcium-related fruit disorder known as bitter pit

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of 50.25 ft from starting point). Managing Bitter Pit in ‘Honeycrisp’ Apples With Foliar Calcium Although ‘Honeycrisp’ apples are very popular with consumers, they are prone bitter pit, a physiological disorder that results in unmarketable fruit and

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Thomas Sotiropoulos, Nikolaos Koutinas, Antonios Petridis, and Ioannis Therios

’ do not show symptoms of the physiological disorder ”bitter pit” or ”external browning.” The fruit maintains firmness, juiciness, and flavor very well in standard cold storage (0 to 1 °C) for ≈5 months. Origin The cultivar Odysseus is a cross between

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Paweł Wójcik, Anna Skorupińska, and Hamide Gubbuk

Calcium deficiency in apple ( M. domestica Borkh.) flesh is a serious problem for many varieties ( Wójcik, 2004 ). Apples with a low Ca status are sensitive to cracking, sunburn, and some physiological disorders (bitter pit, cork spot, superficial