Changes in fruit quality and carotenoid profile in tomato (Solanum lycopersicon L.) genotypes under elevated temperature K.S. Shivashankara, K.C. Pavithra, R.H. Laxman, A.T. Sadashiva1, T.K. Roy and G.A. Geetha Division of Plant Physiology and Biochemistry ICAR-Indian Institute of Horticultural Research Hesaraghatta Lake Post, Bengaluru - 560 089, India E-mail: shivaiihr@yahoo.com ABSTRACT Tomato (Solanum lycopersicon L.) is a rich source of carotenoids, especially lycopene, and is affected severely by high temperatures under tropical conditions. To study the effect of elevated temperature on lycopene content and other quality parameters, five tomato genotypes, viz., RF4A, Abhinava, Arka Saurabh, IIHR 2195 and Arka Vikas, were grown in a temperature gradient tunnel (TGT) facility under 33.4 and 35.4ºC temperature conditions. Fruits were analyzed for total carotenoids, total phenols, total flavonoids, total sugars, TSS, acidity, Vitamin C besides carotenoids profile (βββββ-carotene, lycopene, phytoene and luteoxanthin content). Results revealed that all the quality parameters studied were superior at 33.4ºC, compared to 35.4ºC in all the genotypes. ‘IIHR 2195’ recorded highest total phenols (479.28mg/100g dw), total flavonoids (70.27mg/100g dw), ferric reducing antioxidant potential (FRAP) (310.53mg/100g dw), diphenyl picryl hydrazyl (DPPH) radical (487.89mg/100g dw), Vitamin C content (292.25mg/ 100g dw) and total sugars (606.88mg/g dw) at 33.4ºC and at 35.4ºC. ‘RF4A’ and ‘Arka Vikas’ were found to have better total carotenoids content and lycopene at higher temperature than other genotypes. ‘Arka Vikas’ recorded highest total soluble solids (TSS) (8.9ºBrix) and acidity (0.80%) at 35.4ºC. Higher TSS and acidity were recorded at 35.4ºC than at 33.4ºC in all the five genotypes. Genotypic variation was observed in the above stated biochemical parameters in response to elevated temperatures. Key words: Tomato, TGT, antioxidants, elevated temperature, UPLC 1Division of Vegetable Crops, ICAR-Indian Institute of Horticultural Research, Hesaraghatta Lake Post, Bengaluru - 560 089, India INTRODUCTION Global warming is an important issue threatening most horticultural crops, and can lead to serious consequences in food production. Tomato, being sensitive to temperature, is likely to be influenced by elevated temperatures under a climate change scenario (Laxman et al, 2013). Increase in temperature under climate-change circumstances affects crop yield, in turn affecting sustained supply for meeting a growing demand. Tomato, an important horticultural crop in India, is currently the second largest vegetable in terms of production. It is one of the most consumed vegetables in the world. Tomatoes are rich in bioactive compounds, including carotenoids (lycopene, β-carotene, phytoene and luteoxanthin), ascorbic acid, flavonoids and phenolic compounds (Kaur et al, 2013). Along with phenols, higher intake of flavonoids, Vitamin C and carotenoids has been reported to reduce the risk of many degenerative diseases (Agarwal and Rao, 2000). Optimal mean daily temperatures for tomato lie between 21 and 24°C, depending on the developmental stage (Geisenberg and Stewart, 1986). Supra-optimal temperatures cause a series of complex morphological, physiological, biochemical and molecular changes that adversely affect plant growth and productivity (Wang et al, 2003). Temperature has a significant influence on many aspects of growth and development in tomato. Temperature below 16ºC can cause flower abscission, while temperature above 30ºC can cause fruit cracking and blotchy ripening (Islam, 2011). Impact of high temperature on the plant is not limited to flowering and fruit-set, but also subsequent development and maturity of the fruit, and fruit quality. Lee and Kader (2000) reported higher Vitamin C content in tomato grown under low temperatures than that under high temperature. High temperature also affects biosynthesis of carotenoids, J. Hortl. Sci. Vol. 10(1):38-43, 2015 39 Fruit quality and carotenoids in tomato under elevated temperature especially lycopene (Kaur et al, 2013). Environmental factors other than temperature, like, plant nutrition and light, can also considerably affect biosynthesis of carotenoids. Phenolic acids and flavonols are reported to increase under high temperature conditions in strawberry (Wang and Zheng, 2001). Although sufficient literature is available on fruit quality parameters in different tomato genotypes, studies on varietal response to elevated temperature in terms of fruit quality are scanty and this information is essential to identify varieties suited to a changing climate. Therefore, the present experiment was set in a temperature gradient tunnel to study the effect of temperature on fruit quality parameters and carotenoid profile in five tomato genotypes. MATERIAL AND METHODS The experiment was carried out at ICAR-Indian Institute of Horticultural Research, Bengaluru, in a temperature gradient tunnel during the months of October 2011 to February 2012. Bengaluru is located at 13º58' N latitude, 78ºE longitude and 890m above mean sea level. Five genotypes of tomato (Solanum lycopersicon L.), viz., RF4A, Abhinava, Arka Saurabh, IIHR 2195 and Arka Vikas, were selected for the study. Twenty-five day old seedlings were transplanted into 20 litre capacity plastic containers filled with soil, FYM and sand, in the ratio of 2:1:1. Temperature gradient tunnel (TGT) measuring 18m length, 4.5m width and 3m height, covered with a polycarbonate sheet was used in the study. One week after transplanting, the containers were shifted to TGT for imposition of temperature treatments. One set comprising six plants each of the five genotypes was placed near the cooling pad and another set with the same number of plants was placed towards the fan (where the average air temperature was about 2°C higher than at the cooling-pad end). Daily temperatures and relative humidity (RH) during fruit growth period recorded inside TGT are shown in Fig. 1. The gradient inside TGT was maintained only during daytime, as TGT worked on the pad-and-fan system. Since there was no gradient in the night-time minimum temperature, only one value for temperature is indicated (Fig. 1). Photosynthetically active radiation (PAR) inside the TGT was about 85% of that of the light outside. The plants were provided with recommended dose of fertilizer, and suitable crop protection measures were applied when required. Freshly-harvested, fully ripe fruits were used for analysis. Fruits were crushed in a blender and a known quantity of the homogeneous mass was set apart for analysis. Quality parameters like TSS, % acidity, Vitamin C content, total phenols, total flavonoids, FRAP, DPPH, total carotenoids and total sugars were analyzed. Total soluble solids (TSS) were recorded using a digital refractometer (ARKO India Ltd., Model DG-NXT) and expressed in ºBrix. Acidity was determined by the titration method (AOAC, 942.15) using phenolphthalein as the indicator. Acidity was expressed in per cent citric acid equivalent. Vitamin C content was determined using 2,6- dichlorophenol indophenol (DCPIP) method (AOAC, 967.21) and calculated as mg ascorbic acid equivalent per 100g dry weight. Total phenols present in 80% methanol extract were estimated by Folin-ciocalteu method (Singleton and Rossi, 1965). Methanol extract was mixed with FCR reagent and the color developed with 20% sodium carbonate reagent. Intensity of color developed was read at 700nm using a spectrophotometer (T80+ UV/VIS Spectrophotometer, PG Instruments Ltd., UK). Results were expressed in mg gallic acid equivalent per 100g dry weight. Total flavonoids content was estimated as per Chun et al (2003). Flavonoids present in the 80% methanol extract were estimated using 5% NaNO2 and 10% AlCl3. Absorbance of the pink mixture was read at 510nm and expressed as mg catechin equivalent per 100g dry weight. Antioxidant capacity was measured as FRAP, using a modified method of Benzie and Strain (1996). Methanol extract (0.2ml) was mixed with 1.8ml FRAP reagent. Intensity of the blue colour that developed was measured at 593nm. Total antioxidant capacity (as ferric reducing antioxidant potential) was calculated and the antioxidant capacity was expressed as mg ascorbic acid equivalent antioxidant capacity (AEAC) per 100g dry weight. Radical-scavenging ability was measured using DPPH radical assay of Kang and Saltveit (2002). A 0.2ml aliquot of methanol extract was mixed with 0.3ml of 10mM acetate buffer (pH 5.5) and 2.5ml methanolic 0.2mM DPPH solution. Reduction in color due to scavenging of DPPH radicals by antioxidants was estimated by reading the absorbance at 517nm. Radical-scavenging ability was expressed as weight of the sample required for 50% Fig. 1. Daily maximum/minimum temperature (°C) and relative humidity (%) during the last 35 days of fruiting season J. Hortl. Sci. Vol. 10(1):38-43, 2015 40 reduction in DPPH radicals. Total sugars present in the 80% ethanol extract were estimated using dinitrosalicylic acid method (Miller, 1959). A 0.2ml aliquot of extract was mixed with DNS reagent and the absorbance read at 540nm, expressed as mg glucose equivalent per gram dry weight using a standard curve. Total carotenoids and lycopene content were analyzed by spectrophotometric method (Lichtenthaler, 1987). Carotenoids were estimated by extracting with acetone, partitioned to hexane, and their absorbance read at 470 and 503nm. Standards were used for calibration, and results were expressed as mg per 100g dry weight. Carotenoid profile by UPLC Carotenoid profile was estimated by UPLC as per Serino et al (2009) with minor modifications. Acquity-UPLC system from Waters (Milford, MA, USA) consisting of a quaternary pump, auto sampler injector and PDA detector equipped with Acquity-UPLC BEH-C18 column (1.7μm, 2.1X50mm) with BEH-C18 (1.7μm, 2.1X5mm) guard column was used. Instrument control and data processing were done using Mass Lynx software. The mobile phase consisted of phase-A acetonitrile:methanol:ethyl acetate (53:7:40) and phase-B methanol. Isocratic flow rate of 0.2ml/ min was used in the ratio of A:B (95:5) for 6 min with PDA scanning from 200 to 650nm. Individual carotenoids were identified by diode array spectral characteristics, retention time and relative elution order compared to standards and values in literature. Carotenoids were quantified as β-carotene equivalents. A known quantity (1ml) of hexane extract was evaporated to dryness, and residual carotenoids were dissolved in the mobile phase and filtered through 0.2μm nylon filter prior to ion injecting in UPLC for further analysis. The detection was monitored at 450nm for β- carotene, 470nm for lycopene, 286nm for phytoene and 420nm for luteoxanthin. Statistical analysis Data were subjected to Analysis of Variance using ANOVA, and, means were compared, with critical difference at P≤0.05. RESULTS AND DISCUSSION Changes in fruit quality parameters in five tomato genotypes at two temperature conditions are presented in Table 1. TSS increased with increase in temperature in all the genotypes (5.6 to 7.2ºBrix) and ranged from 3.8 to 7.1ºBrix at 33.4ºC, and at 35.4ºC, it ranged from 4.5 to 8.9ºBrix. Similar trend was observed in per cent acidity too. Acidity ranged from 0.34 to 0.68% at 33.4ºC, whereas, at 35.4ºC, the acidity ranged from 0.39 to 0.80%. Sugars and acids are important components in tomato fruit flavor (George et al, 2004; Kaur et al, 2013). Increase in titratable acidity with increase in temperature has been reported (Khanal, 2012). Among genotypes, Arka Vikas recorded the highest TSS (8.9ºBrix) and acidity (0.80%) at 35.4ºC. Higher temperature is known to enhance soluble solids level in relation to ambient temperature conditions (Gunawardhana and De Silva, 2011; Khanal, 2012). Table 1. Changes in fruit quality parameters of five tomato genotypes at two temperature conditions Genotype Mean TSS Acidity Vitamin C Total Total FRAP DPPH Total Total temperature (ºBrix) (%) (mg/100g phenols flavonoids (mg/100g (mg/100g carotenoids sugars during dw) (mg/100g (mg/100g dw) dw) (mg/100g (mg/g fruiting stage dw) dw) dw) dw) RF4A 33.4ºC 5.9 0.53 265.68 344.51 44.63 209.34 321.56 270.36 375.91 35.4ºC 7.1 0.66 272.49 378.99 45.06 160.37 306.32 191.97 366.21 Abhinava 33.4ºC 6.1 0.46 272.06 361.73 42.83 202.06 310.16 228.98 423.03 35.4ºC 8.6 0.66 263.70 377.48 43.21 168.35 293.08 136.14 221.03 Arka Saurabh 33.4ºC 3.8 0.34 225.94 336.88 33.03 198.39 315.28 269.14 403.99 35.4ºC 4.5 0.39 258.59 419.68 45.52 191.93 318.73 176.74 264.38 IIHR 2195 33.4ºC 4.9 0.46 292.25 479.28 70.27 310.53 487.89 205.13 606.88 35.4ºC 6.8 0.64 271.63 461.61 66.88 231.92 415.20 155.45 379.79 Arka Vikas 33.4ºC 7.1 0.68 226.19 352.64 49.66 208.72 343.55 197.33 347.23 35.4ºC 8.9 0.80 212.87 436.62 64.40 192.90 377.65 158.24 254.68 Mean 33.4ºC 5.6 0.49 256.42 375.01 48.08 225.81 355.69 234.19 431.41 35.4ºC 7.2 0.63 255.86 414.88 53.01 189.09 342.20 163.71 297.22 CD for varieties (V) (P≤0.05) 0.02 0.01 1.98 1.67 0.82 1.36 1.40 0.81 1.86 CD for temperature (T) (P≤0.05) 0.01 0.01 NS 0.67 0.33 0.55 0.56 0.32 0.74 CD for V x T (P≤0.05) 0.05 0.03 3.96 3.34 1.64 2.73 2.80 1.62 3.72 NS= Non-Significant Shivashankara et al J. Hortl. Sci. Vol. 10(1):38-43, 2015 41 Vitamin C content did not show significant differences among the two temperature treatments. However, among genotypes, IIHR 2195 and RF4A recorded higher Vitamin C content at 33.4ºC and 35.4ºC respectively compared to other genotypes. Total phenols and flavonoids increased with increase in temperature in all the genotypes (375.01 to 414.88 and 48.08 to 53.01 mg/100g dw for total phenols and total flavonoids respectively). Higher total phenols and flavonoids were observed in cv. IIHR 2195. Phenolic substances are reported to have a protective effect on ascorbic acid (Toor and Savage, 2006). Therefore, presence of phenolics and flavonoids in tomato cells may have helped maintain ascorbic acid level. Ferreyra et al (2007) also reported ascorbic acid level to be not significantly affected by temperature during the growth season. Wang and Zheng (2001) found elevated growth temperature of 30ºC to significantly enhance the content of phenolic acids and flavonols in strawberry. Accumulation of phenolics at higher growth temperature has been reported in other crops too (Wang, 2006; Toor et al, 2006). Total antioxidant capacity and radical-scavenging ability were assessed using FRAP and DPPH methods respectively. All the genotypes recorded significantly higher FRAP and DPPH at 33.4ºC. Among genotypes, higher FRAP and DPPH values were recorded in IIHR 2195 at both 33.4ºC and 35.4ºC. ‘RF4A’ and ‘Abhinava’ recorded lower FRAP values at 35.4ºC compared to other genotypes. ‘Abhinava’ recorded lower DPPH values at both 33.4ºC and 35.4ºC. All the genotypes recorded higher total sugars at 33.4ºC than at 35.4ºC. IIHR 2195 recorded the highest total sugars (606.88mg/g dw) at 33.4ºC. Temperature changes are known to affect fruit maturation and growth through influencing regulation of the enzymes acid invertase and sucrose synthase or cell-expansion and division and regulation of sugar transport into the fruit (Fleisher et al, 2006). Gautier et al (2005) reported decrease in sugar content in cherry tomato when fruit temperatures increased. Sugar content in purple passionfruit juice was highest at low growth temperature, and lowest at high growth temperature. More sucrose accumulated at low temperature, while glucose and fructose content increased at higher temperature (Utsunomiya, 1992). All these studies support our observations in tomato. In the present study, all the genotypes studied recorded higher total carotenoids and lycopene content at 33.4ºC than at 35.4ºC. Carotenoid profiles indicated that β-carotene, lycopene, phytoene and luteoxanthin content was greater at 33.4ºC in all genotypes. Temperature had a significant influence on total carotenoids and lycopene content. High temperature may lead to degradation of lycopene (Demiray et al, 2013), in addition to a reduced synthesis (Helyes et al, 2007). Temperatures greater than 30ºC lead to inhibition of lycopene synthesis in normal red cultivars of tomato and synthesis is restored when the temperature drops below 30ºC. These temperature effects vary with the tomato cultivar (Garcia and Barrett, 2006). Temperatures below 12ºC strongly inhibit lycopene biosynthesis, while temperatures over 32ºC stop this process altogether (Dumas et al, 2003). Temperature during fruit ripening plays a more important role in lycopene biosynthesis than it does during fruit growth period. Fig. 2 shows chromatograms of tomato carotenoids at 33.4ºC and 35.4ºC. All the carotenoid pigments under study diminished at 35.4ºC in all five genotypes (Table 2). Greatest reduction was observed in two major pigments, lycopene and phytoene. However, reduction was lower in ‘RF4A’ and ‘Arka Vikas’. Higher reduction was noticed in ‘Abhinava’. In conclusion, Changes in fruit quality parameters in five tomato genotypes under elevated temperature were studied under TGT. Variations were observed among tomato genotypes for fruit quality parameters at elevated temperature. Increase in temperature improved TSS and per cent acidity, but decreased total carotenoids, lycopene Fig. 2. UPLC chromatograms of carotenoids in tomato fruit extract. Chromatogram A represents carotenoid profiling at 33.4°C (maximum temperature near the cooling pad) and chromatogram B represents carotenoid profiling at 35.4°C (maximum temperature towards the fan). Peaks identified are: (1) Luteoxanthin, (2) Lycopene, (3) βββββ-Carotene and (4) Phytoene J. Hortl. Sci. Vol. 10(1):38-43, 2015 Fruit quality and carotenoids in tomato under elevated temperature 42 and total sugars in all the genotypes studied. Among the genotypes, IIHR 2195 was found to be better in terms of total phenols, total flavonoids, FRAP, DPPH and total sugars at 33.4ºC, as also at 35.4ºC. ‘Arka Vikas’ was found to be high in TSS and per cent acidity at 33.4ºC. RF4A and Arka Vikas were found to be good at maintaining lycopene level at elevated temperature, compared to the other genotypes. Genotype IIHR 2195 is recommended for cultivation at elevated temperatures. ACKNOWLEDGEMENT This work was carried out under a project entitled “National Initiative on Climate Resilient Agriculture (NICRA)”, Indian Council of Agricultural Research (ICAR), New Delhi. The authors are grateful to Director, IIHR, Bengaluru, for providing necessary facilities. REFERENCES Agarwal, S. and Rao, A.V. 2000. Tomato lycopene and its role in human health and chronic diseases. Can. Med. Assoc. J., 163:739-744 Association of Official Analytical Chemists. 2000. In: Official Methods of Analysis, 17th edition, Titratable acidity of fruit products, 942.15. AOAC International, Gaithersburg Association of Official Analytical Chemists. 2006. In: Official Methods of Analysis, Ascorbic acid, 967.21, 45.1.14. AOAC International, Gaithersburg Benzie, I.F.F. and Strain, J.J. 1996. The ferric reducing ability of plasma (FRAP) as a measure of antioxidant power: The FRAP assay. Anal. Biochem., 239:70-76 Chun, O.K., Kim, D.O., Moon, H.Y., Kang, H.G. and Lee, C.Y. 2003. Contribution of individual polyphenolics to total antioxidant capacity of plums. J. Agri. Food Chem., 51:7240-7245 Demiray, E., Tulek, Y. and Yilmaz, Y. 2013. Degradation kinetics of lycopene, β-carotene and ascorbic acid in tomatoes during hot air drying. Food Sci. Tech., 50:172-176 Dumas, Y., Dadomo, M., Lucca, G.D. and Grolier, P. 2003. Effects of environmental factors and agricultural techniques on antioxidant content of tomatoes. J. Sci. Food Agri., 83:369-382 Ferreyra, R.M., Vina, S.Z., Mugridge, A. and Chaves, A.R. 2007. Growth and ripening season effects on antioxidant capacity of strawberry cultivar Selva. Sci. Hort., 112:27-32 Fleisher, D.H., Logendra, L.S., Moraru, C., Both, A.J., Cavazzoni, J., Gianfagna, T., Lee, T.C. and Janes, H.W. 2006. Effect of temperature perturbations on tomato (Lycopersicon esculentum Mill.) quality and production scheduling. J. Hort. Sci. Biotech., 81:125- 131 Garcia, E. and Barrett, D.M. 2006. Assessing lycopene content in California processing tomatoes. J. Food Proc. Pres., 30:56-70 Gautier, H., Rocci, A., Buret, M., Grasselly, D. and Causse, M. 2005. Fruit load or fruit position alters response to temperature and subsequently cherry tomato quality. J. Sci. Food Agri., 85:1009-1016 Geisenberg, C. and Stewart, K. 1986. Field crop management. In: The Tomato Crop (Atherton, J.G. Table 2. UPLC data on phytoene, lycopene, βββββ-carotene and luteoxanthin in five tomato genotypes at two different temperature conditions Genotype Phytoene Lycopene β-Carotene Luteoxanthin (mg/100g dw) (mg/100g dw) (mg/100g dw) (mg/100g dw) 33.4ºC 35.4ºC % 33.4ºC 35.4ºC % 33.4ºC 35.4ºC % 33.4ºC 35.4ºC % increase/ increase/ increase/ increase/ decrease decrease decrease decrease over over over over 33.4ºC 33.4ºC 33.4ºC 33.4ºC RF4A 29.20 27.05 -7.35 174.38 130.43 -25.20 11.38 5.95 -47.70 4.48 4.94 10.36 Abhinava 67.02 35.10 -47.64 150.65 88.91 -40.98 8.11 6.20 -23.52 3.88 2.17 -44.16 Arka Saurabh 29.74 17.67 -40.58 175.54 121.34 -30.87 5.74 3.67 -36.09 5.01 2.95 -41.20 IIHR 2195 36.67 19.25 -47.49 131.46 88.38 -32.77 7.69 3.69 -52.06 4.03 2.23 -44.57 Arka Vikas 30.08 17.64 -41.37 146.46 122.61 -16.29 4.39 5.22 18.67 3.43 1.61 -53.19 Mean 38.54 23.34 170.78 122.65 7.46 4.94 4.17 2.78 CD for varieties 0.40 2.68 0.46 0.13 (V) (P≤0.05) CD for temperature 0.16 1.07 0.18 0.05 (T) (P≤0.05) CD for V x T 0.80 5.36 0.92 0.27 (P≤0.05) J. Hortl. Sci. Vol. 10(1):38-43, 2015 Shivashankara et al 43 and Rudich, J. eds.) pp. 511-557 George, B., Kaur, C., Khurdiya, D.S. and Kapoor, H.C. 2004. Antioxidants in tomato (Lycopersium esculentum) as a function of genotype. Food Chem., 84:45-51 Gunawardhana, M.D.M. and De Silva, C.S. 2011. Impact of temperature and water stress on growth yield and related biochemical parameters of okra. Trop. Agri. Res., 23:77-83 Helyes, L., Lugasi, A. and Pek, Z. 2007. Effect of natural light on surface temperature and lycopene content of vine ripened tomato fruit. Can. J. Pl. Sci., 87:927- 929 Islam, M.T. 2011. Effect of temperature on photosynthesis, yield attributes and yield of tomato genotypes. Int’l. J. Expt’l. Agri., 2:8-11 Kang, H.M. and Saltveit, M.E. 2002. Antioxidant capacity of lettuce leaf tissue increases after wounding. J. Agri. Food Chem., 50:7536-7541 Kaur, C., Walia, S., Nagal, S., Walia, S., Singh, J., Singh, B.B., Saha, S., Singh, B., Kalia, P., Jaggi, S. and Sarika. 2013. Functional quality and antioxidant composition of selected tomato (Solanum lycopersicon L.) cultivars grown in Northern India. Food Sci. Tech., 50:139-145 Khanal, B. 2012. Effect of day and night temperature on pollen characteristics, fruit quality and storability of tomato. Master’s Thesis, Department of Plant and Environmental Sciences, Norwegian University of Life Sciences, Norway Laxman, R.H., Srinivasa Rao, N.K., Bhatt, R.M., Sadashiva, A.T., John Sunoj, V.S., Biradar, G., Pavithra, C.B., Manasa, K.M. and Dhanyalakshmi, K.H. 2013. Response of tomato (Lycopersicon esculentum Mill.) genotypes to elevated temperature. J. Agrometeorol., 15:38-44 Lee, S.K. and Kader, A.A. 2000. Pre-harvest and post- harvest factors influencing Vitamin C content of horticultural crops. Postharvest Biol. Technol., 20:207-220 Lichtenthaler, H.K. 1987. Chlorophylls and carotenoids: Pigments of photosynthetic biomembranes. Meth. Enzymol., 148:350-382 Miller, G.L. 1959. Use of dinitrosalicylic acid reagent for determination of reducing sugars. Anal. Chem., 31:426-428 Serino, S., Gomez, L., Costagliola, G. and Gautier, H. 2009. HPLC assay of tomato carotenoids: validation of a rapid micro-extraction technique. J. Agri. Food Chem., 57:8753-8760 Singleton, V.L. and Rossi, J.A. Jr. 1965. Colorimetry of total phenolics with phosphomolybdic-phosphotungstic acid reagents. Amer. J. Enol. Viticult., 16:144-158 Toor, R.K. and Savage, G.P. 2006. Changes in major antioxidant components of tomatoes during post- harvest storage. Food Chem., 99:724-727 Toor, R.K., Savage, G.P. and Lister, C.E. 2006. Seasonal variations in the antioxidant composition of greenhouse grown tomatoes. J. Food Comp. Anal., 19:1-10 Utsunomiya, N. 1992. Effect of temperature on shoot growth, flowering and fruit growth of purple passion fruit (Passiflora edulis Sims var. edulis). Sci. Hort., 52:63-68 Wang, S.Y. 2006. Effect of pre-harvest conditions on antioxidant capacity in fruits. Acta Hort., 712:299- 305 Wang, S.Y. and Zheng, W. 2001. Effect of plant growth temperature on antioxidant capacity in strawberry. J. Agril. Food Chem., 49:4977-4982 Wang, W., Vinocur, B. and Altman, A. 2003. Plant responses to drought, salinity and extreme temperatures: towards genetic engineering for stress tolerance. Planta, 218:1-14 (MS Received 24 November 2014, Revised 30 April 2015, Accepted 15 May 2015) J. Hortl. Sci. Vol. 10(1):38-43, 2015 Fruit quality and carotenoids in tomato under elevated temperature