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Shirin Shahkoomahally and Asghar Ramezanian

treatments to maintain qualitative characteristics of kiwifruit during cold storage. Materials and Methods Plant material Mature, unripe kiwifruit ( Actinidia deliciosa cv. Hayward) of medium-sized (80 to 120 g) fruits, free from visible defects or decay

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David L. Warfield and Edwin Seim

The root structure of kiwifruit was investigated by sequential trenching and eventual removal of whole vines. The vines had a shallow (30 to 60 cm.) spreading root system with few sinker roots. Roots extended beyond the canopy. Radial distribution of major roots arising from the crown was non-uniform. In several instances, roots mimicked the top by tying themselves into knots.

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M. Cristina Pedroso, M. Margarida Oliveira, and M. Salomé S. Pais

Nodal segments and shoot tips of axenic shoot cultures of `Hayward' kiwifruit were inoculated on modified Murashige and Skoog (MS) medium supplemented with zeatin at 1 mg·liter-1 and IAA at 0.05 mg·liter-1 (H1) or on MS medium without growth regulators (H2). Inocula cultured on H2 medium all developed into normal plantlets, while those cultured on H1 medium developed into shoots, 18% of them abnormal. Rooting of H1 shoots was induced by a 24-h immersion in a solution of IRA at 20 mg·liter-1. H2 plantlets were directly transferred to soil. Statistical treatment of the results revealed no significant differences, in terms of plant development, between the two micropropagation methods used. However, the presence of a functional root system on 5-week-old H2 plantlets resulted in 100% plant survival, but only 70% of in vivo-rooted shoots from H1 survived. Nevertheless, H1 still allowed for an important reduction of costs and manipulation. Chemical names used: indole3-acetic acid (IAA).

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Arlie A. Powell and Ed Tunnell

It has been shown that the `Hayward' kiwifruit requires ≈1000 chilling hours for satisfactory production of female flowers, leading to full cropping in the southeastern United States. Part of the area along the Gulf Coast frequently suffers from inadequate winter chilling, resulting in poor cropping of `Hayward'. Studies were conducted over a 4-year period in a mature `Hayward' planting near the Gulf Coast to evaluate the efficacy of hydrogen cyanamide sprays in replacing lack of chilling and improving cropping. Rates of 2%, 3%, and 4% (v/v) of 50% Dormex significantly increased yield, with the highest rate providing the maximum yield. Fruit size and overall fruit quality from Dormex treatments were good. Dormex sprays performed quite well when only 600 to 700 chilling hours were received in the test area.

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F. Mencarelli, L. Lanzarotta, R. Massantini, and R. Botondi

Kiwifruits were picked by hand and gently placed in pulp trays. Impact tests were conducted by dropping the fruits from heights of 30 cm onto different sandpapers to provide a uniform abrasion surface. Abrasion tests were conducted by compressing the fruits with a fixed load of 3.5 N (Instron equipment) onto different sandpapers and pulling out the fruits. Compression test was performed by using the previous procedure with a fixed load of 4.5 N for different period of time (minutes). Increase of transpiration rate and ethylene production was observed in fruits abraded with sandpaper which slight wounded the peel. Impact onto sandpaper, caused the appearance of white lignifted filaments in the flesh. Increase in soluble solids and softness of flesh and core was observed in injured fruits. Healing process and polyamines effect will be discussed.

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R. Messina, R. Testolin, and M. Morgante

The usefulness of isozyme banding patterns as genetic markers in kiwifruit [Actinidia deliciosa (A. Chev.) C.F. Liang et A.R. Ferguson] was investigated using starch gel electrophoresis. Fifty-four entries putatively belonging to seven female and two male kiwifruit cultivars were examined for 13 enzyme systems (AAT, ACO, GDH, G6PDH, IDH, MDH, ME, MNR, NDH, 6PGD, PGI, PGM, and SKDH). Four enzyme systems, ACO, MDH, NDH, and SKDH, showed identical banding patterns in all clones surveyed. Of the remaining enzymes, AAT, PGI, and PGM had the best discriminating power. Six enzyme systems (GDH, G6PDH, IDH, ME, MNR, and 6PGD), though showing polymorphic banding patterns, were poorly resolved. All the New Zealand cultivars were uniquely identified by the simultaneous comparison of the AAT, PGI, and PGM zymograms. Some enzyme systems were also polymorphic among plants within the same cultivar, thus proving the heterogeneity of kiwifruit material introduced into Europe in the early 1970s.

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Teresa F. Wegrzyn and Elspeth A. MacRae

The activities of several cell wall-associated enzymes of the outer pericarp were assayed during softening of kiwifruit [Actinidia deliciosa (A. Chev.) C.F. Liang et A.R. Ferguson var. deliciosa cv. Hayward] treated with ethylene. The activity of polygalacturonase (EC 3.2.1.15) increased slightly during fruit softening, while β-galactosidase (EC 3.2.1.23) activity remained constant. Salt-extracted pectinesterase (EC 3.1.1.11) activity increased during ethylene treatment, then dropped rapidly to low levels as fruit softened. Residual pectinesterase activity, extracted after digestion of the cell wall pellet with a fungal enzyme mix, decreased on softening. The rapid softening of kiwifruit in response to ethylene treatment may be initiated by an induction of pectinesterase activity, causing increased de-esterification of cell wall pectins, followed by degradation of solubilized pectin.

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Nicky G. Seager and Roger M. Haslemore

Experiments investigating kiwifruit [Actinidia deliciosa (A. Chev) C.F. Liang et A.R. Ferguson var. deliciosa] maturation were undertaken requiring the determination of total soluble sugar (TSS) and starch concentrations in numerous fruit samples. The phenol-sulfuric acid assay was judged to he a convenient method for determining TSS from tissue extracts and gave results similar to those obtained by high-pressure liquid chromatography. The starch procedure adopted involved gelatinizing fruit tissue using hot water and a thermostable α -amylase (Termamyl); hydrolizing starch using amyloglucosidase; and determining glucose using glucose oxidase. The methods enabled one person to analyze up to 40 kiwifruit samples for TSS and starch concentrations during 9 hours and likely will be applicable to research concerning fruit development and maturation.

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W.A. Dozier Jr., A.W. Caylor, D.G. Himelrick, A.A. Powell, A.J. Latham, J.A. Pitts, and J.A. McGuire

Own-rooted, 4-year-old kiwifruit plants [Actinidia deliciosa (A. Chev.) C.F. Liang et R. Ferguson var. deliciosa] protected by a Styrofoam insulation wrap with a water-filled pouch (Reese clip-on trunk wrap) or by microsprinkler irrigation sustained less freeze injury than unprotected plants under field conditions at temperatures as low as -17.8C. Trunk splitting occurred on the plants, but no injury was detected on canes, buds, or shoots in the canopy of the plants. Unprotected plants had more trunk splitting and at greater heights than protected plants. New canes developed from suck- ers of cold-injured plants and developed a trellised canopy the following season.

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María Victoria González, Manuel Rey, and Roberto Rodríguez

A simple and reliable protocol for plant regeneration from petioles of micropropagated plants of kiwifruit [Actinidia deliciosa (A. Chev) Liang and Ferguson, var. deliciosa `Hayward'] is described. Morphogenic callus was initiated by culturing petioles taken from in vitro-propagated plants. From the media tested, Cheng's K(h) medium plus 0.1 μm IAA, 4.5 μm zeatin, and 2% sucrose was the best for callus induction, maintenance, and shoot bud formation and development. Bases of developed shoots were immersed in 5 mm IBA for 15 seconds; subsequent culture in half-strength K(h) basal medium achieved 82% rooting. Regenerated plantlets were successfully transplanted to soil with 97% survival. Chemical names used: indole-3-acetic acid (IAA); indole-3-butyric acid (IBA); 2-methyl-4-(1H-purin-6-ylamino)-2-buten-1-ol (zeatin).