Seedlessness and Fruit Quality Traits of Gibberellin Induced Parthenocarpic Fruit in Seven Tomato Genotypes ( Solanum lycopersicum L . )

Parthenocarpic fruit development is regulated by a plant hormone, i.e. gibberellin. The response of seven lines of tomato to gibberellin was investigated to distinguish the degree of parthenocarpy and to compare the quality of seedless and seeded fruits. The flower from stage 12 (size 5 mm) until 4 days after anthesis was sprayed with GA3 0 mmol/L and 0.06 mmol/L. The treatments were arranged in Randomized Complete Block Design with three replications. GA3 0.06 mmol/L reduced pollen germination, whose pollen germination (28.98%) was lower than 0 mmol/L (46.06%). The total numbers of seeds and fertilized seeds of treated fruit were significantly reduced in comparison with the control. Gibberellin application also increased the number of degenerated seeds. Within the genotypes studied, four groups were distinguished, which showed a different degree of parthenocarpy in response to gibberellin application. Kaliurang 206 and A65 are categorized as seedless with a 93.65% and 89.58% reduction in the total number of seeds, respectively. Gamato 1 is categorized as low-seeded with an 83.83% reduction in the total number of seeds. Gamato 3, Gamato 5, and B78 are categorized as medium-seeded with a 69.83-80.85% reduction in the total number of seeds, whereas A175 is categorized as normal-seeded with a 36.94% reduction in the total number of seeds. Gibberellin significantly increased the sugar content by 14.04% and reduced the ascorbic acid content by 9.68% of parthenocarpic fruits compared with the untreated.


Introduction
The majority of seeds are undesirable features in many crops, particularly edible fruit.Some seeds have a bitter taste, are hard, and cause a digestive problem.Seeds and their cavities could be replaced by edible fruit tissue and it is more desirable than seeded fruit.Seedless fruits are developed from unfertilized ovary due to the absence of pollination and/or fertilization, and they are therefore called parthenocarpy (Varoquaux, Blanvillain, Delseny, & Gallois, 2000).Parthenocarpy is a useful trait for industrial purposes, especially the tomato sauce industry because seeds should be removed before processing in order to obtain the best quality of the sauce (Rotino et al., 2005;Sato, Peet, & Gardner, 2004).In addition, parthenocarpy may improve the quality of the fruit through the increased sugar content of the fruit (1°Brix higher than normal fruits), high dry matter content, less acidity, less cellulose, and higher contents of carotene and lycopene than seeded fruit (Lukyanenko, 1991).
The Faculty of Agriculture, Gadjah Mada University had developed six new lines of tomatoes, namely Gamato 1, Gamato 3, Gamato 5, A65, A175, and B78.These tomato lines were derived from different parents.Gamato 1, Gamato 3, A65, A175 were derived from GM1 × Gondol Hijau, whereas Gamato 5 and B78 were derived from GM3 × Gondol Putih.These tomato lines had obovoid-shape fruit and round-shape fruit, big fruit size, high yield and were suitable for industrial purposes.However, the tomato fruit contained a lot of seeds which could become a problem for the tomato sauce and drink industries.In addition, they will hire more laborers and increase production cost.The objective of this study was to determine the degree of parthenocarpy of new tomato lines exposed to the GA 3 application before anthesis and to compare the fruit quality between seedless and seeded tomato fruits.

Plant Material and Experimental Design
Tomato plants (Solanum lycopersicum L.) cv Gamato 1, Gamato 3, Gamato 5, Kaliurang 206 and tomato lines A65, A175, B78 were used in the experiments.Gamato 1, Gamato 3, A65, A175 are pure lines that derived from GM1 × Gondol Hijau, while Gamato 5 and B78 are derived from GM3 × Gondol Putih.Kaliurang 206, a commercial cultivar grown in the wide area, was used as a check cultivar.The experiment had been conducted in the greenhouse of The Seed Development Center of Horticultural Crop, Special Region of Yogyakarta, Indonesia.The flowers from stage 12 (size 5 mm) until 4 days after anthesis was sprayed with GA 3 0 mmol/L and 0.06 mmol/L.The treatments were arranged in Randomized Complete Block Design with three replications.The experimental unit was consisted of eight plants.The plants were grown in mulched soil (silver and black plastic polyethylene film) at the spacing of 50 cm × 60 cm.Standard agronomic techniques were applied during the growing season from November 2014 to January 2015.Non-emasculated flowers were sprayed with gibberellic acid (GA 3 ) (Merck) 0.06 mmol/L and 0 mmol/L (control).Spraying GA 3 started on the first flower (stage 12) according to Brukhin et al. (2003) until 4 days after anthesis with an interval of 3 days for 6 applications from cluster 1 to cluster 3.

Data Collection
Collected data consisted of pollen germination, the total number of seeds per fruit, the reduction in the number of seeds per fruit (%), the total number of fertilized seeds per fruit, the reduction in the number of fertilized seeds (%), the degenerated seeds per fruit, the sugar content, the ascorbic acid content, and fruit firmness.Three plants were chosen as plant sample in all experimental units.Two fruits were sampled from three plant samples in all experimental units for the total number of seeds per fruit, the reduction in the number of seeds per fruit (%), the total number of fertilized seeds per fruit, the reduction in the number of fertilized seeds (%), the degenerated seeds per fruit, the sugar content, the ascorbic acid content, and fruit firmness.Two flowers were collected at anthesis (stage 20) for pollen germination assessment from one plant sample in all experimental units.Pollens were germinated on the liquid medium containing 12% (w/v) sucrose, 0.01% boric acid (H 3 BO 3 ), and pH 6.4 according to Wang et al. (2003).Pollen density was 1500/1 ml medium.Pollens were homogenized 1 min with vortex and incubated at room temperature of 25 °C.The incubated pollen was observed with a microscope (Kruss, Germany) at a magnification of 100x.The picture of each sample was captured 5 replications using Optilab Viewer.The fruit firmness was measured using Penetrometer (Bareiss Pruefgeraetebau GmbH type BS 61 II).The sugar content was determined using refractometer (ATAGO Pocket refractometer, Japan, 0-53% Brix).The ascorbic acid (vitamin C) content was determined by titration method according to Jacobs (1962).The degree of parthenocarpy was determined using a modified method of Mazzucato et al. (1998).Seedless (0-15 seeds), low-seeded (16-25 seeds), medium-seeded (26-50 seeds), and normal-seeded (> 51 seeds).

Statistical Analysis
Data were analyzed with Analysis of Variance (ANOVA) according to randomized complete block design and Duncan's Multiple Range Test (P ≤ 0.05).Data processing and statistical analysis were carried out with SAS 9.3.www.ccsen Figure 1 Note.Shad 1 (Gam1), significant fruit.Parthenocarpic fruits had valuable features for increasing their potential economic values.Tomato genotypes used in this study are proposed for industrial tomatoes such as the sauce and juice industries.The enhancement of tomato fruit quality with a high sugar content and less acidity is preferable for the consumer.This method has a constraint on its application to indeterminate plants because flowering does not occur simultaneously, so that the spraying of GA 3 should be done more thoroughly on each cluster.It is, however, easy to be applied to determinate plants.It is also feasible to adopt this method and apply it to other species, but there is a need to ensure the right and appropriate GA 3 concentrations to induce parthenocarpy.