Tomato Fruit Yield and Quality as Affected by Grafting and Growing System

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1 Tomato Yield and Quality as Affected by Grafting and Growing System M.M. Qaryouti, W. Qawasmi, H. Hamdan and M. Edwan National Center for Agricultural Research and Technology Transfer (NCARTT) Baq a Jordan Keywords: Tomato grafting, salt stress; yield, fruit quality, open soilless system Abstract An experiment was conducted to study the effect of grafting on yield, quality and shelf life of tomato using simplified open soilless system vs. conventional soil cultivation. The experiment was carried out at Al-Karama station which represents areas north of the Dead Sea where soil salinity is the limiting factor for higher yields. F1 cv. (most commercial tomato cultivar grown in Jordan) two rootstocks (He-man and Spirit) was compared with non-grafted (control) plants in both simplified open soilless system (containers filled with volcanic tuff) and conventional soil cultivation. Uniform 45 days-old seedlings of grafted and nongrafted were transplanted in two 500m 2 uncontrolled plastic houses on Nov. 4, 2004, irrigated with nutrient solution after taking into consideration nutrients available in irrigation water. s were harvested at full mature stage to determine fruit yield, number of fruits per plant and fruit weight. Random fruit samples from cluster 3 and 5 were used to determine fruit outer and inner quality and shelf life. The results showed that fruit yield was improved by grafting in both growing systems. yield increased by 12-27% in soilless cultivation and by 16-38% in soil cultivation with grafting on He-Man and Spirit, respectively. quality in terms of total soluble solids, antioxidant capacities, vitamin C, lycopene and β- carotene content were reduced or slightly improved by grafting in both growing systems. However, fruit size and shelf life were not affected and fruit firmness improved by grafting but these parameters were improved in soilless as compared with soil cultivation. This variations in our results between soilless and soil cultivation and the behavior of the rootstocks might due to the fact that plants grown in soilless culture were not under salt stress as compared with those grown in soil. The result also showed that using simplified open soilless system improved productivity and fruit quality in terms of fruit size, shelf life and firmness. However, more studies needed to determine the effect of grafting on inner quality of tomato fruit. INTRODUCTION Grafted solanaceous plants have been expanded greatly in the recent years in order to reduce infections caused by pathogens, to enhance tolerance to abiotic soil stresses, such as low temperature, drought, and salinity (Ahn et al., 1; AVRDC, 2001) and to enhance nutrient uptake (Fernandez-Garcia et al., 2003). In addition to such traditional advantages, grafted seedlings have been attracting the interest of greenhouse hydroponic (soilless culture) growers internationally, since grafting is thought to provide increased vigor to the scion, which is especially significant in longer crop cycles (Leonardi and Romano, 2004). This increased vigor is perhaps due to the rootstock acting as a superior conductor of water, providing more water and nutrients to the stems, leaves and fruits, mainly because of the better developed root system. This has resulted in some increase in numbers of hydroponic tomato growers utilizing grafted seedlings and increasing production of grafted tomato seedlings (Leonardi and Romano, 2004). In most Mediterranean countries including Jordan, salinity is one of the most limiting factors for expand protected cultivation. For this reason, introduction of grafting techniques might be one of the solutions to reduce salinity negative effect on plants. The Proc. I st IS on Fresh Food Quality Eds. A.N. Fardous et al. Acta Hort. 741, ISHS

2 effect of grafting on tomato fruit quality was not yet clear. For this reason, in this paper, a commercial tomato cultivar two rootstocks and ungrafted were compared in two growing systems (simplified open soilless system and conventional soil cultivation) in order to investigate the effect of using grafting techniques on tomato fruit yield, outer and inner fruit quality and shelf life of tomato fruits. MATERIALS AND METHODS Treatments The experiment was carried out in two (500 m 2 ) uncontrolled plastic houses and in each plastic house 6 treatments were done as follows: Growing system Grafting 1 Open simplified soilless system Non grafted 2 He Man 4 Spirit 6 Conventional soil cultivation Non grafted 7 He Man Spirit Soilless treatment was done in 12x0.2x0.3 m containers filled with volcanic tuff and covered with black plastic mulch (Fig. 1), while soil cultivation treatments consist of 12x 0.2 raised beds covered with black plastic mulch. On Nov. 4, 2004, uniform, 45-days old tomato seedlings were transplanted in to experimental fields (soilless and in soil) and each experimental unit contains 24 plants with plant density 2.5 plants m -2. The experimental design was factorial with four replicates. Soil and Water Analysis Soil and water samples were taken pre-planting to determine soil and water salinity and nutrient content (Table 1). Nutrient Solution and Irrigation Water and nutrient requirements for both soilless and soil cultivation were supplied with nutrient solution having the following composition (ppm): N 171, P 48, K 304, Ca 180, Mg 48, Fe 3, Mn 2, B 1, Zn 0.4, Cu 0.2 and Mo 0.1 after taking into consideration those nutrients available in the irrigation water for the soilless treatments and plus those available in soil for soil cultivation. Stock nutrient solution was prepared in two tanks and injected into irrigation water using Venturi injectors. Water application for soilless treatment was done by filling each container up to 10 cm height and refilled when needed; ph and EC of the nutrient solution were checked daily and adjusted between ph and EC ds m -1. In the soil cultivation, time and quantity of water application was based on tensiometers and on Class A pan readings according to following recommended equation (Sha ban et al., 17): ETa = (Epan x Kp x Kt) x Kc x Kr Where, ETa = Actual water requirement (mm/day) Kp = Pan coefficient (0.75) Kt = Solar transitivity inside plastic houses (0.7) Kc = Crop coefficient (0.45 for primary stage, 0.75 for development stage and 0.85 for productive stage). Kr = Plant cover coefficient (Kr = (Area covered with crop/area of the field)+ 0.1). Yield and Quality s were harvested at the mature red stage (stage -10 of the color scale, 200

3 Ctifl, Bergere, France) starting from Feb. 23 to May 30, 2005 for soilless treatments and from March 3 rd to June 15, 2005 for soil cultivation. The harvested fruits were separated into exportable yield (fruit with diameter above 55 mm) and non-exportable (fruit diameter less than 55 mm), counted and weighed to determine number of fruit per plant and fruit weight. Random fruit samples from clusters 3 and 5 were taken to determine physical traits: dry weight %, fruit diameter and firmness (determined with compression tester in which 2 kg weight is placed the equator of the fruit for 10 sec and mm compression is measured). dry matter (dm) was determined by drying to a constant weight at 70 o C in a Shel. Laboratory ventilated oven. Juice samples were used directly for the determination of Total soluble solids (TSS) using Reichert-Jarg Digital (ABBE Mark II model 10481) refractometer and expressed as Brix%. Freeze dried fruit samples from cluster 3 of each treatment were used to determine fruit inner quality analysis; Organic acids are given as Citric acid (Auerwald et al., 1 after LMBG; Acker et al., 168 after international sap union 162). Vitamin C content and the carotene content were detected by HPLC (Davey et al., 2003; Sander et al., 14). The content of reducing agents in the phenol and flavonoid extract was measured with the Folin-Ciocalteu-Test and is expressed as Gallic acid equivalents (Singleton et al., 18) The extraction of phenols and flavonoids was modified after a method of Tura and Robards (2002) with 80% MeOH following Ethylacetat. Carotenoids were extracted with MeOH / THF following Hexan (Hart and Scott, 15). For the detection of antioxidative capacity (AC) a 2,2 -azino bis- (3-ethylbenzothiazoline-6-sulfonsäure) (ABTS) discoloration assay was used (Cano et al., 2000). In this System the ABTS.+ is created at the beginning of the measurement by adding 120 µm Peroxidase (POD) and 700 mm H 2 O 2 solution to 2 mm ABTS in Ethanol. By adding acidified Ethanol (0,7% H 3 PO 4 ) the POD gets stabilized in the lipophilic system. All concentrations are referred to stock solutions. Reagents are dissolved in Ethanol, with exception of the water soluble POD. The absorption of the generated radical is measured at 734 nm in a photometer for 6 minutes. After 2 minutes the test extracts (solved in CH 2 Cl 2 / EtOH 500/1500 ml for carotene, 1000 ml EtOH for flavonoids and 1000 ml 80% MeOH for phenols) are added. The difference of absorption between 2 and 6 minutes is used as reference value for the antioxidative capacity of the substrate which is referred to as troloxequivalents. Uniform fruit samples (stage 6 of the color scale, Ctifl, Bergere, France) were used to determine fruit shelf life after storing the fruits in refrigerator (6-8 o C) and at room temperature (20 o C). The data for all measurements were subjected to single factor analysis of variance and means were separated using Duncan s Multiple Range Test at p<0.05. RESULTS The results showed a significant improve in exportable yield (fruits with diameter larger than 55 mm) with grafting on both rootstocks in soilless cultivation as compared with non-grafted (Table 2), while in soil cultivation, only grafting on spirit improved exportable yield significantly. Non-exportable yield was not affected significantly by grafting, while in soil cultivation grafting on He-man increased nonexportable yield significantly as compared with other treatments. In soilless cultivation, total yield was improved significantly by grafting except for He-Man; same trend was observed in soil cultivation. In general, plant exportable yield and total yield were improved by soilless cultivation as compared with soil cultivation, this increase due mainly to the effect of soil salinity (Table 1). Average fruit number per plant was also improved by grafting in both growing systems (Table 2), while average fruit weight was not affected by grafting in soilless cultivation and in general by grafting except for using He-Man. In general, fruit dry matter %, fruit size, pericarp thickness, were not significantly affected by grafting (Table 3), although a slight improvement was observed in soilless as compared to soil cultivation especially for pericarp thickness. In soilless cultivation, fruit TSS (Brix %) decreased with grafting treatments as compared with non grafted, 201

4 while in soil cultivation this percentage was increased with grafting. firmness was greater in soilless as compared with soil cultivation, however, grafting has a slight effect on fruit firmness (Table 3). Grafted tomato in soilless culture decreased antioxidant capacities and vitamin C content (Table 4) while is soil cultivation, their content was not affected significantly except an increase in vitamin C content when Spirit. Galic acid content was not affected by grafting in soilless treatment and only increased significantly when He-man. Lycopene and β-carotene decreased with grafting treatments in soilless cultivation, however, their content increased or not affected with grafting in soil cultivation (Table 4). The highest lycopene and β- carotene content observed form non grafted in soilless, while in soil cultivation the highest lycopene content was found in He-man and when spirit for β-carotenoid. shelf life in terms of change in fruit color and firmness with time was not affected and fruit firmness was greater by grafting but these parameters were improved in soilless as compared with soil cultivation. DISCUSSION The overall objective of our study was to promote grafting tomato in marginal areas where soil salinity is the limiting factor for high yields (Table 1) through testing the behavior of grafted and non-grafted tomato in soilless system in comparison to soil cultivation. In general, vegetable grafting has been motivated by the need to increase plant yields (Kim et al., 18; Asao et al., 1). Our results showed that fruit yield was improved by grafting in both growing systems but to higher extend in soilless system which due to the effect of soil salinity in soil cultivation compared to unstressed plant grown in soilless culture (EC of nutrient solution was ranged between 3 to 3.5 ds m -1 ). quality in terms of total soluble solids, Antioxidant capacities, vitamin C, lycopene and β-carotene content were not improved by grafting in both growing systems and even reduced in soilless cultivation. However, fruit size and firmness were not affected or improved by grafting but they were greater in soilless as compared to soil cultivation. ACKNOWLEDGEMENTS This work was financed by the European Union within the 5th Framework of the INCO-MED 2 ( ) Project N ICA3-CT ( ). Literature Cited Acker, et al Analysis of Total Phenols and Other Oxidation Substrates and Antioxidants by Means of Folin-Ciocalteu Reagent, Methods of Enzymol. 2, Ahn, S.J., Im, Y.J., Chung, G.C., Cho, B.H. and Suh, S.R. 1. Physiological responses of grafted cucumber leaves and rootstock roots affected by low root temperature. Sci. Hort. 81: Auerswald, H., Schwarz, D., Kornelson, C., Krumbein, A. and Brückner, B. 1: Sensory analysis, sugar and acid content of tomato at different EC values of the nutrient solution, Scientia Horticulturae 82, Asao, T., Shimizu, N., Ohta, K. and Hosoki, T. 1. Effect of rootstocks on the extension of harvest period of cucumber (Cucumis sativus L.) grown in non-renewal hydroponic. J. Jap. Soc. Hort. Sci. 68(3): AVRDC Improvement and stabilisation year-round vegetable suppliers. Asian Vegetable Research and Development Center, Report 2001, Program II, Project 4: Cano, A., Acosta, M. and Arnao, M.B. 2000: A method to measure antioxidant activity in organic media: application to lipophilic vitamins, Redox Report 5 (6), Davey, M.W., Dekempeneer, E. and Keulemans, J. 2003: Rocket-powered high- 202

5 performance liquid chromatographic analysis of plant ascorbate and glutathione, Analytical Biochemistry 316, Fernandez-Garcia, N., Cerda, A. and Carvajal, M Grafting, a Useful Technique for Improving Salinity Tolerance of Tomato. Acta Hort. 60: Hart, D.J. and Scott, K.J. 15: Development and evaluation of an HPLC method for the analysis of carotenoids in foods, and the measurement of the carotenoid content of vegetables and fruits commonly consumed in the UK. Food Chem. 54, Kim, H.T., Kang, N.J. and Kang, K.Y. 18. Selection of PusanDaemok 1 for high yield and quality in rootstock of cucumber. RDA J. Horti. Sci. 40(2): Leonardi. C. and Romano, D Recent Issues on Vegetable Grafting. Acta Hort Sander, L.C., Sharpless, K.E., Craft, N.E. and Wise, S.A. 14. Development of Engineered Stationary Phases for the Separation of Carotenoid Isomers, Anl. Chem. 66, Singleton, V.L., Orthofer, R. and Lamuela-Raventós, R.M. 18. Analysis of Total Phenols and Other Oxidation Substrates and Antioxidants by Means of Folin- Ciocalteu Reagent, Methods of Enzymol. 2, Sha ban,m., Abu-Taleb, M., Baqa in, A. and Hamdan, M. 17. Irrigation Scheduling for Vegetables Inside Plastic Houses Using Pan Evaporation Readings in the Jordan Valley. Water Quality Improvement and Conservation Program. Ministry of Water and Irrigation. Tura, D., and Robards, K Sample handling strategies for the determination of biophenols in food and plants, Journal of Chromatography A 75,

6 Tables Table 1. Salinity and nutrient content of soil and water pre planting samples in soil cultivation treatment at Al-Karama station, Sample EC ph ppm (ds m -1 ) Ca Mg Na Cl Soil 0-30 cm Soil cm Water Table 2. Interactive effects of growing system and grafting on plant yield, number of fruit per plant and fruit weight of green house tomato grown at Al-Karama experimental site, Planting system Soilless Treatments Yield Kg m 2 Grafting Exportable yield* Non grafted He-Man Spirit Non- Exportable yield Total yield Average fruit number per plant Average fruit weight ab** 2.15 a b 63.6 a 50.8 a 6.81 a a.735 a 67.6 a 57.5 a 6.74 a a a 6.4 a 5.0 a Soil Non grafted c bc d 40.1 c 47.0 a He-Man bc b 5.43 cd 46.8 bc 46.8 a Spirit 5.20 ab 1.14 c bc 52.2 b 50.0 a * s with diameter above 55 mm. **Values within columns having different letters are significantly different according to DMRT ( p<0.05) 204

7 Table 3. Interactive effects of growing system and grafting on fruit quality of green house tomato grown at Al- Karama experimental site, Treatments Planting system Soilless Soil Grafting Non grafted He-Man Spirit Non grafted He-Man Spirit D W % length (cm) diameter (cm) pericarp thickness (cm) TSS (Brix %) firmness (cm compressed*).25 a* 3.77 ab 5.50 a 0.38 ab 6.3 a 0.28 c 8.48 a 3.75 ab 5.55 a 0.38 ab 4.3 c 0.33 bc 8.28 a 4.45 a 5.18 ab 0.43 a 4.5 c 0.35 bc 8.35 a 3.83 ab 4.78 ab 0.15 c 6.1 a 0.48 ab 8.48 a 3.57 b 5.33 ab 0.20 c 6.3 a 0.55 a 8.3 a 3.43 b 4.33 b 0.28 bc 5.3 b 0.45 ab **Values within columns having different letters are significantly different according to DMRT ( p<0.05) Table 4. Interactive effects of growing system and grafting on fruit quality of green house tomato grown at Al-Karama experimental site, Treatments Antioxidant capacities (Trolox in 100g FW) Vit. C (mg / 100g FW) Folin test (Galic acid in 1 00g FW) Lycopene (mg Carotenoid / 100 g FW) β-carotinoid (mg Carotenoid / 100 g FW) Planting Grafting System Soilless Non grafted 7.80 a* a bc a a grafted on He-Man 4.06 c.1 d 8.12 c f d grafted on Spirit 3.25 c 7.8 e ab 1.28 e b Soil Non grafted 6.21 b.36 cd bc d bc grafted on He-Man 6.77 ab c a 1.50 b c grafted on Spirit 5.87 b b ab c a **Values within columns having different letters are significantly different according to DMRT ( p<0.05) 205

8 Figures 10 without grafting He-Man Spirit Refrigerator 10 Room temperature Change in fruit color without grafting He-Man Spirit Soilless 7 6 without grafting He-Man Spirit 7 6 without grafting He-Man Spirit Soil Days after harvesting Fig. 1. Interactive effects of grafting and growing systems on tomato fruit shelf life (change in fruit scale, Ctifl, Bergere, France) stored in refrigerator an at room temperature Refrigerator without grafting He-Man Spirit Room temperature Change in fruit Firmness without grafting He-Man Spirit Days after harvesting 0 without grafting He-Man Spirit without grafting He-Man Spirit Soilless Soil Fig. 2. Interactive effects of grafting and growing systems on tomato fruit shelf life (change in fruit firmness (mm compressed) stored in refrigerator an at room temperature. 206