(TDZ), gibberellic acid (GA3)

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Effects of application of thidiazuron (TDZ), gibberellic acid (GA3), and 2,4‐dichlorophenoxyacetic acid (2,4‐D) on fruit size and quality of Actinidia deliciosa ’Hayward’ a

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F. Famiani , P. Proietti , M. Pilli , A. Battistelli & S. Moscatello

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Dipartimento di Scienze Agrārie e Ambientali, Università degli Studi di Perugia, Borgo XX Giugno, Perugia, 74–06121, Italy E-mail: b

Dipartimento di Scienze Agrārie e Ambientali, Università degli Studi di Perugia, Borgo XX Giugno, Perugia, 74–06121, Italy c

Istituto di Biologia Agroambientale e Forestale, Consiglio Nazionale delle Ricerche, Viale Marconi, 2–05010 Porano (TR), Italy Version of record first published: 19 Feb 2010.

To cite this article: F. Famiani, P. Proietti, M. Pilli, A. Battistelli & S. Moscatello (2007): Effects of application of thidiazuron (TDZ), gibberellic acid (GA3), and 2,4‐dichlorophenoxyacetic acid (2,4‐D) on fruit size and quality of Actinidia deliciosa ’Hayward’, New Zealand Journal of Crop and Horticultural Science, 35:3, 341-347 To link to this article: http://dx.doi.org/10.1080/01140670709510200

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New Zealand Journal of Crop and Horticultural Science, 2007, Vol. 35: 341—347 0014-0671/07/3503-0341 © The Royal Society of New Zealand 2007

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Effects of application of thidiazuron (TDZ), gibberellic acid (GA3), and 2,4-dichlorophenoxyacetic acid (2,4-D) on fruit size and quality of Actinidia deliciosa 'Hayward' F. FAMIANI P. PROIETTI M. PILLI Dipartimento di S cienze Agrārie e Ambientali Università degli Studi di Perugia - Borgo XX Giugno 74-06121 Perugia, Italy email: [email protected]

the growth potential of kiwifruit is much higher than is normally expressed.

A. BATTISTELLI S. MOSCATELLO Istituto di Biologia Agroambientale e Forestale Consiglio Nazionale delle Ricerche - Viale Marconi 2-05010 Porano (TR), Italy

INTRODUCTION

Abstract The effects of dipping fruit in solutions made from factorial combinations of 0 and 10 ppm thidiazuron (TDZ), 0 and 50 ppm gibberellic acid (GA3), and 0 and 20 ppm 2,4-dichlorophenoxyacetic acid (2,4-D) on fruit size and quality characteristics in Actinidia deliciosa 'Hayward' were evaluated. When the compounds were used together significant interactions, TDZ× GA3 and TDZ× GA3× 2,4D, were recorded for the increase in fruit weight (+42% and +94%, respectively, compared with untreated fruits that had an average weight of 82.7 g). TDZ and 2,4-D were very effective in increasing fruit weight when used alone (+31% and +32%, respectively, compared with untreated fruits) or in combination with the other compounds. GA3 only showed an appreciable effect when used in combination with TDZ or TDZ + 2,4-D. Growth regulator treatments did not affect seed weight and number per fruit. TDZ accelerated fruit ripening and caused a change in fruit shape. TDZ and GA3 did not affect the fruit carbohydrate content at harvest, whereas the use of 2,4-D slightly decreased the fruit total carbohydrate content. The results indicate that H06081; Online publication date 21 August 2007 Received 22 August 2006; accepted 11 April 2007

Keywords thidiazuron; gibberellic acid; 2,4dichlorophenoxyacetic acid; plant growth regulators; hormonal interaction; kiwifruit growth; carbohydrate content; kiwifruit; Actinidia deliciosa

Because of the widespread availability of kiwifruit (Actinidia deliciosa (A. Chev.) C.F. Liang et A.R. Ferguson) on the market, revenue depends largely on stable productivity and good quality. Size, carbohydrate content, and flesh firmness are key quality factors for kiwifruit. The size of fruit depends on the number and size of cells and this is influenced by hormonal signals that originate in the developing seeds (Phillips 2004). Promoting fruit growth using both natural and synthetic exogenous growth regulators has been studied in several species (Nickell 1991). Hopping (1976) showed that it was possible to promote kiwifruit growth by exogenous application of auxins, cytokinins, and gibberellins. Subsequently, Nickel (1986) and Iwahori (1988) obtained strong increases in fruit size of A. deliciosa 'Hayward' using CPPU (N-(2-chloro-4-pyridyl)-N'phenylurea), a synthetic cytokinin-like compound. Cruz-Castillo et al. (1992, 1993, 1999) showed that the addition of GA3 (gibberellic acid) and 2,4-D (2,4dichlorophenoxyacetic acid) increased the effect of CPPU on fruit growth of kiwifruit, but they did not report on the effects of the substances individually or on possible interactions among them. Thidiazuron (TDZ), another cytokinin-like compound, was also effective in increasing fruit size in A. deliciosa 'Hayward' (Famiani et al. 1999,2002) and cultivars 'Allison', 'Bruno', and 'Monty' (Pétri et al. 2001; Jindal et al. 2003). No data on the combined effects of auxin and gibberellin substances with TDZ are available. More knowledge about the combined effects of hormonal substances is useful to better understand the hormonal control of fruit growth.

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New Zealand Journal of Crop and Horticultural Science, 2007, Vol. 35

The aim of this work was to evaluate the effects and possible interactions of the application of exogenous growth regulators belonging to the auxin (2,4-D), gibberellin (GA3), and cytokinin (TDZ) groups, used singularly or in combination, on fruit growth and quality of A. dellclosa 'Hayward'.


MATERIALS AND METHODS Plant material and field treatments The trial was carried out in 1998 in central Italy in a mature commercial kiwifruit orchard of 'Hayward' (A. deliciosa), with 'Matua' as polliniser (female/ male vines = 5:1). The vines, trained on a T-bar trellis system and spaced 5× 4m, were grown on a medium textured soil with drip irrigation. Fifteen days after full bloom (AFB), fruits were dipped, for c. 5 s, in solutions of factorial combinations of TDZ, GA3, and 2,4-D, at concentrations of 0 and 10 ppm, 0 and 50 ppm, 0 and 20 ppm, respectively. One hundred fruits, distributed on five different vines (20 fruits vine"1), were used for each treatment. The different solutions were prepared by using stock solutions obtained by dissolving TDZ in dimethyl sulfoxide (DMSO) (10% p/v), 2,4-D in ethanol (5% p/v), and GA3 in NaOH 0.2M (5% p/v). "Agral" wetter (0.5 ml litre"1) was added to the solutions before using them for treatments. Fruit growth, weight, shape, and quality assessment From treatment application (15 days AFB) to harvest, fruit development was recorded by measuring the maximum diameter of 40 labelled fruits per treatment. At harvest, the same 40 fruits were used to determine the final fresh weight and to evaluate fruit size and shape, by measuring the fruit diameters and length and by calculating length/average diameter and maximum/minimum diameter ratios. Fruit dry matter content was determined on 15 fruits per treatment and flesh firmness and soluble solids content were determined on 40 fruits per treatment, as in Famiani et al. (1999). These 40 fruits were also used to estimate the number of seeds, by counting the visible seeds in the two half-fruit cross-sections. To determine the fresh and dry weights of seeds, 20 seeds per fruit were weighed before and after drying them at 90°C in a forced air oven to constant weight. A subsample of 25 fruits per treatment was ripened at 20°C for 1 month and flesh firmness and soluble solids content measured.

Carbohydrate measurements At harvest, carbohydrate measurements were performed on the external pericarp. Five individual fruits per treatment were used. Fruits were harvested from the vine, and the hair and epidermis were removed by scraping the surface with a sharp knife. The external pericarp was then removed and rapidly frozen in liquid nitrogen and stored at -80°C. Before analysis the frozen samples were ground to a fine powder under liquid nitrogen in a pre-cooled mortar. The extractions, in 80% ethanol, and the analysis, by spectrophotometric coupled enzymatic assay, were then performed as described by Antognozzi et al. (1996). Statistical analysis Data were statistically analysed by ANO VA according to a factorial design and the averages were compared by the Student-Newman-Keuls Test. Data on fruit growth are reported as mean + standard error.

RESULTS The influence of the different compounds on fruit growth was detectable 3 weeks after their application, showing a very rapid action (Fig. 1). When the three different compounds were used together, the following significant interactions on final fruit weight were recorded: TDZ× GA3 and TDZ× GA3× 2,4-D (Table 1). TDZ and 2,4-D were very effective in increasing both fresh and dry fruit weight when used alone and in combination with the other compounds, whereas GA3 only had an appreciable effect when used in combination with TDZ or TDZ + 2,4-D. The effects of TDZ, GA3, and 2,4-D on fruit length and diameters were, in general, similar to those described for fruit weight (Table 1). The application of growth regulators did not cause a change in the ratio between the maximum and minimum fruit diameters, whereas, in some instances, there was a change in the ratio between fruit length and average diameter (Table 1). In particular, the presence of TDZ always caused a reduction in the length/average diameter ratio. The addition of only GA3 or 2,4-D did not change the effect of TDZ on fruit shape, but the effect was reduced when all compounds were applied together. Application of TDZ, GA3, and 2,4-D did not cause changes in fruit seed number and weight (data not shown). There were no significant interactions between treatments on fruit dry matter content, flesh firmness, and soluble solids and carbohydrate contents;

Famiani et al.—Growth regulator influence on kiwifruit

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Fig. 1 Effects of growth regulators on fruit growth of 'Hayward' kiwifruit (Actinidia deliciosa). Bars represent the standard error of the mean. (TDZ, thidiazuron; GA3, gibberellic acid; 2,4-D, 2,4-dichlorophenoxyacetic acid; Days AFB, days after full bloom.)

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