Original Paper Environ. Control Biol., 52 (3), 155
160, 2014 DOI: 10.2525/ecb.52.155

Effects of the Rare Sugars D-psicose and D-tagatose on the Sugar Content and Incidence of Blossom End Rot in Tomato Grown Hydroponically with Salinity Treatment

1 1 1 1 2 2 Yoshihiro YAMADA ,KazumasaKAKIBUCHI , Ayako KOZUKI , Yutaka ISHIDA ,KenIZUMORI , Shigeyuki TAJIMA , 2 3 3 Kazuya AKIMITSU , Takeo OHKOUCHI and Fumito KASAI

1 Shikoku Research Institute Inc., 2109
8 Yashima-nishimachi, Takamatsu, Kagawa 761
0192, Japan 2 Faculty of Agriculture, Kagawa University, 2393 Ikenobe, Miki, Kida, Kagawa 761
0795, Japan 3 Mitsui Chemicals Agro Inc., 1358 Ichimiyake, Yasu, Shiga 520
2362, Japan

(Received March 4, 2014; Accepted June 12, 2014)

Low sugar content of fruits in winter, and blossom end rot in summer, are serious problems in the production of tomato with high soluble solids content. In the present study, we investigated the effects of the rare sugars D-psicose and D-tagatose on the sugar content of fruits and incidence of blossom end rot during several cropping seasons. We determined a highly positive correlation between the sugar content and the cumulative solar radiation during the maturation period. Treatment with D-psicose resulted in an increase in the sugar content over every cropping season. It resulted in a reduction in the in- cidence of blossom end rot, a reduction in stomatal conductance, and an increase in the relative water content in summer. On the other hand, it resulted in an increase in the incidence of blossom end rot in winter and rainy season. Treatment with D-tagatose had no effect on the sugar content, incidence of blossom end rot, water potential, stomatal conductance, or rela- tive water content. Our results indicate that treatment with D-psicose is advantageous for increasing the sugar content in winter and preventing the incidence of blossom end rot in summer.

Keywords : D-allulose, fruit quality, monosaccharide, solar radiation, water relations

rot, and reduced yield (Ito et al., 1994; Oka et al., 2004). INTRODUCTION Therefore, appropriate regulation of drying stress is re- quired (Saito et al., 2006). Rare sugars are defined by The International Society Kakibuchi et al. (2011) showed that the application of of Rare Sugars as “monosaccharides and their derivatives the rare sugar D-psicose inhibited transpiration and reduced that rarely exist in nature.” The effects of rare sugars have the incidence of blossom end rot in tomato grown recently been investigated. For example, D-allose and D- hydroponically with salt application. Their study was con- psicose have been shown to induce disease resistance in ducted in a warm season, and did not verify the effects of rice and lettuce (Kano et al., 2010; 2011; 2013; Ishida et D-psicose in other seasons. al., 2012). Ishida et al. (2011) demonstrated that D-tagatose In the present study, we investigated the effects of D- reduced the flower-setting node order of morning glories, psicose and another rare sugar, D-tagatose, on the sugar and accelerated flower bud differentiation in strawberries. content and incidence of blossom end rot during production Kakibuchi et al. (2011) reported that some monosacchari- of tomato with high soluble solids content, in warm and des, including rare sugars, especially L-fructose and D- cool seasons. psicose inhibit transpiration. Therefore, these rare sugars may function as antitranspirants for use in various cultiva- MATERIALS AND METHODS tion systems, e.g., production of tomato with high soluble solids content. Plant materials and growth conditions The production of tomato with high soluble solids Tomatoes (Solanum lycopersicum L., cv. Momotaro 8; content is a cultivation method for increasing the sugar Takii Seed Co., Ltd., Japan) were grown in a greenhouse content of fruits by applying a higher level of drying stress with acrylic panels. The temperature was maintained through restriction of irrigation (Ito et al., 1994) or root vol- within the range 15
35°C. Tomato plugs were grown in ume (Ishigami et al., 1994), use of a nutrient solution with rockwool cubes (75 mm
75 mm
65 mm, Delta 4G, high electrical conductivity (Noguchi et al., 2012), or appli- Grodan, Netherlands) and transplanted to rockwool slabs cation of a salt solution (Oka et al., 2004; Araki et al., (900 mm
195 mm
75 mm; Grotop Master 2075 A1W, 2009). However, excessive drying stress results in de- Grodan, Netherlands) when the first truss was visible. The creased fruit weight, increased incidence of blossom end plants were fertilized with a half-strength Otsuka-A solu-

Corresponding author : Kazumasa Kakibuchi, fax: 81
87
887
0003, e-mail : [email protected]

Vol. 52, No. 3 (2014) 
 Y. YAMADA ET AL.

tion (Otsuka Chemical, Co., Osaka, Japan), with an EC of weight. We measured the sugar content of the fruits by ex- 1.2 dS m
1. The nutrient solution was supplied at a rate of pressing the juice and using a refractometer (PR-1; Atago 960 mL individual
1 day
1 through a drip irrigation tube, at Co., Japan). 2-h intervals during the daytime (6:00
16:00). The main To elucidate the mechanism of action of rare sugars on shoot of each plant was pinched to leave two leaves above the sugar content and incidence of blossom end rot, we the first truss, and all lateral shoots were removed. measured the water potential, stomatal conductance, and The rare sugars D-psicose (D-allulose) and D-tagatose relative water content of the leaves. We made these meas- were supplied by the Rare Sugar Research Center, Kagawa urements in experiments 2 to 4. However, we did not University. D-psicose is the C3-epimer of D-fructose, and measure the water potential in experiment 4, because of dif- D-tagatose is the C4-epimer of D-fructose (Fig. 1). ficulties with the measuring equipment. The water poten- At the day of anthesis, drip irrigation was stopped tial represents the water absorption power, and therefore after two times irrigation in the morning. At 10 : 00 am, to- leaves with low water potential are expected to absorb mato plants in rare sugar treatment were watered to the more water from fruits, thereby increasing the sugar con- plant foot with 350 mL of a nutrient solution containing 50 tent of the fruits. Stomatal conductance corresponds to the mmol L
1 rare sugar using a beaker. Tomato plants in con- transpiration rate, and the relative water content is used as trol were similarly watered 350 mL of a nutrient solution an indicator of the drying stress. Increasing leaf transpira- without rare sugar. From the next day of anthesis of the tion inhibits the influx of calcium to fruits, and increases first flower to the end of experiment, 2.98 g L
1 of NaCl the incidence of blossom end rot (Adams and Ho, 1993). was added to the nutrient solution, to maintain the same os- Most blossom end rot occurs 3 weeks after anthesis (Saito motic potential (290 kPa) as a high electrical conductivity et al., 2006), and therefore we measured the water poten- nutrient solution (EC8.0dSm
1). Fourteen days after tial, stomatal conductance, and relative water content dur- anthesis, rare sugar treatments were repeated at the same ing the daytime (11:00
14:00) on sunny days 3 weeks after way as the day of anthesis, but using nutrient solution con- anthesis. We used the unshaded leaflet above the first truss taining 2.98 g L
1 . In experiment 1, plants were trans- for all measurements. We measured the water potential by planted on June 14, 2011, and flowered on June 21, 2011. using a pressure chamber (Model 3005; Soil Moisture In experiment 2, plants were transplanted on September 28, Equipment Corp., USA) and the stomatal conductance by 2011, and flowered on October 18, 2011. In experiment 3, using a Porometer (Leaf Porometer; Decagon Devices, Inc., plants were transplanted on May 28, 2012 and flowered on USA). We calculated the relative water content by using May 27, 2012. In experiment 4, plants were transplanted the following equation with fresh weight at sampling time, on July 23, 2012 and flowered on July 30, 2012. The effect maximum weight in the leaf at full turgor, and dry weight. of D-psicose treatment was tested in experiment 1, and the Relative water content (%)100(fresh weight at effects of D-psicose and D-tagatose were tested in experi- sampling time  dry weight) / (maximum weight in the ments 2
4. In each experiment, 6 individual tomato plants leafatfullturgor dry weight) were used. We sampled one leaflet per plant, and immediately de- Measurements termined the fresh weight. The leaflets were then placed on We measured the shading rate of the greenhouse using a plug tray containing water, and shaded at room tempera- irradiance meter (LP9021RAD, Delta OHM, Netherlands). ture. We measured the leaf weight after 5 h as the maxi- We calculated the cumulative solar radiation in the green- mum weight of the leaf at full turgor. We determined the house based on the shading rate and the daily cumulative dry weight after drying the leaf in an oven at 70°C. solar radiation recorded by the Japan Meteorological Agency (http://www.jma.go.jp/jma/menu/report.html). We RESULTS used the sum of the daily cumulative solar radiation during the maturation period for analyses. The tomato fruits were Table 1 shows the cumulative solar radiation during harvested when completely red. We recorded the harvest- the maturation period, the start day of anthesis, the start day ing date, presence or absence of blossom end rot, and fruit of harvest, the average fruit weight, and the average sugar content. We used these data to calculate the correlation co- efficients between environmental factors and fruit quality indexes of control plants (Table 2). We determined a highly positive correlation between the sugar content and the cumulative solar radiation during the maturation period (Fig. 2, r0.984, P0.05). We found no statistically sig- nificant correlation between the incidence of blossom end rot and the environmental factors, but there was a negative correlation between the incidence of blossom end rot and the duration of the maturation period (Fig. 3, r
0.886). The sugar content of plants treated with D-psicose was higher than that of control plants and plants treated

Fig. 1 Fisher projections of D-fructose, D-psicose (D-allulose), with D-tagatose (Table 1). The incidence of blossom end and D-tagatose. rot in plants treated with D-tagatose was almost identical to

 Environ. Control Biol. EFFECTS OF RARE SUGARS ON TOMATO

Table 1 Effects of rare sugars on the duration of the ripening period and the fruit quality Cumulative Duration of Average fruit Incidence of Average Start day of Average Treatment solar radiation the maturation weight blossom end marketable yield  harvest (date) Brix (°) (MJ m 2) period (days) (g/fruit) rot (%) (g/plant) 1 Control 462.1 July 29 38 73.6 9.1 66.7 95.7 D-psicose 462.1 July 29 38 51.1 (n.s.) 9.3 (n.s.) 33.3 110.6 (n.s.) 2 Control 268.6 Dec. 10 53 131.1 7.5 0 393.3 D-psicose 268.6 Dec. 11 54 117.7 (n.s.) 8.1 (n.s.) 11.8 235.4 (n.s.) D-tagatose 268.6 Dec. 8 51 136.4 (n.s.) 7.6 (n.s.) 0 250.0 (n.s.) 3 Control 292.0 July 6 40 107.2 7.3 27.8 143.0 D-psicose 292.0 July 9 43 47.2 (n.s.) 9.0 (n.s.) 88.9 15.3 (*) D-tagatose 292.0 July 5 39 107.0 (n.s.) 7.5 (n.s.) 11.1 107.0 (n.s.) 4 Control 540.8 Sep. 8 40 47.7 9.5 43.8 31.8 D-psicose 540.8 Sep. 10 42 39.6 (n.s.) 10.3 (n.s.) 21.4 46.5 (n.s.) D-tagatose 540.8 Sep. 8 40 34.2 (n.s.) 9.6 (n.s.) 31.3 30.7 (n.s.) Number of plants used in each treatment was 6. Symbols in parentheses indicate the result of t-test with control (*: P
0.05).

Table 2 Correlation coefficients between environmental factors and fruit quality. Asterisks denote a significant correla- tion by t-test (P
0.05).

Environmental factors Duration of Cumulative the maturation solar radiation period Sugar content 0.984* 0.588 Fruit quality Incidence of 0.771 0.886 blossom end rot

Fig. 3 Effects of rare sugars on the relationship between the duration of the maturation period and the incidence of blossom end rot.

Fig. 2 Effects of rare sugars on the relationship between the cumulative solar radiation during the maturation period and the sugar content of tomato fruits. Fig. 4 The relationship between fruit weight and Brix. that of control plants, but was slightly lower when the dura- tion of the maturation period was short (Table 1). The in- cidence of blossom end rot in plants treated with D-psicose tagatose treatment (Fig. 4). Therefore, D-psicose treatment was lower than that of control plants when the duration of reduced fruit weight while increased sugar content (Table the maturation period was
40 days, but was higher than 1). However, in the summer, because of the reduction of that of control plants when the duration of the maturation the incidence of blossom end rot, D-psicose treatment period was 40 days. The highest incidence of blossom tended to increase the marketable yield in spite of the re- end rot (88%) in plants treated with D-psicose occurred duction of fruit weight (Table 1). when the duration of the maturation period was 43 days. The water potential of plants treated with D-psicose or The sugar content was negatively correlated with the fruit D-tagatose did not differ significantly from that of control weight, and it was not altered by D-psicose treatment or D- plants; however, the water potential of plants treated with

Vol. 52, No. 3 (2014) 
 Y. YAMADA ET AL.

Fig. 5 The effect of rare sugars on the water potential Fig. 6 The effect of rare sugars on the stomatal conductance. of leaves. Vertical bars represent the standard deviation Vertical bars represent the standard deviation (n6).  (n 4). No significant difference was detected accord- Asterisks denote a significant difference in comparison  ing to Dunnett’s test (P 0.05). with the control by Dunnett’s test (P0.05).

D-psicose was slightly lower (Fig. 5). The stomatal con- ductance of plants treated with D-psicose was lower than that of control plants in every cultivation season; on the other hand, the stomatal conductance of plants treated with D-tagatose treatment did not differ significantly from that of control plants (Fig. 6). The relative water content of plants treated with D-psicose did not different significantly from that of control plants in November or June, but was significantly higher than that of control plants in August (Fig. 7). The relative water content of plants treated with D-tagatose did not differ significantly from that of control Fig. 7 The effect of rare sugars on the relative water content of leaves. Vertical bars represent the standard deviation plants (Fig. 7). (n6). The asterisk denotes a significant difference in comparison with the control by Dunnett’s test (P DISCUSSION 0.05).

The production of tomato with high soluble solids content is attractive to growers because of high fruit price. hand, treatment with D-tagatose did not affect the sugar However, low sugar content of fruits in winter, and high in- content (Table 1), water potential (Fig. 5), stomatal conduc- cidence of blossom end rot in summer, are serious prob- tance (Fig. 6), or relative water content (Fig. 7). Thus, D- lems. tagatose seems to have no effect on the water status of In the present study, we showed that the sugar content tomato. of fruits was correlated with the cumulative solar radiation Treatment with D-psicose reduced the transpiration during the maturation period (Table 2). This result indi- rate (Fig. 6) and increased the relative water content in cates that the sugar content may be controlled by regulating warm seasons (Fig. 7). These results indicate that treat- the solar radiation during the maturation period. Gosselin ment with D-psicose alleviates drying stress. Thus, an in- et al. (1996) demonstrated an increase in the sugar content crease in fruit weight and a decrease in sugar content would by using supplemental irradiation under conditions of in- be expected. However, we determined a decrease in fruit adequate irradiance. However, to the best of our knowl- weight and an increase in sugar content (Table 1). The edge, we are the first to report a correlation between the sugar content was negatively correlated with the fruit sugar content and the cumulative solar radiation in the pro- weight, and it was not altered by rare sugar treatment (Fig. duction of tomato with high soluble solids content. The 4). Therefore, the increase of sugar content in D-psicose mechanism of increasing the sugar content of fruits during treatment seemed to be a concentration effect caused by the the production of tomato with high soluble solids content is prevention of water inflow to the fruits. It means, in spite considered to be a concentration effect caused by a de- of alleviation of drought stress by D-psicose treatment, crease in the water content, rather than an increase in the water absorption power of leaves did not decrease. sugar content (Sakamoto et al., 1999). Therefore, in the The mechanism of this phenomenon is not clear, but it present study, the observed correlation between the sugar seems that D-psicose influences the plant in such a way as content and the cumulative solar radiation during the matu- to cause an increase in the sugar content, while maintaining ration period seems to be derived from the increased sugar the water content in leaves. One possible mechanism for concentration in the fruit, caused by promotion of transpira- this effect is osmotic adjustment, i.e., the increase in water tion under conditions of high irradiance. absorption power of the leaf through an increase in the The sugar content of plants treated with D-psicose soluble content of cells within the leaf. In the present was higher than that of control plants and plants treated study, we did not verify the influence of osmotic adjust- with D-tagatose, in every cultivation season. On the other ment; however, we observed a decrease in the water


 Environ. Control Biol. EFFECTS OF RARE SUGARS ON TOMATO

potential of plants treated with D-psicose in the cool season Basic and Applied Researches for Innovations in Bio-oriented (Fig. 5), suggesting the occurrence of osmotic adjustment. Industry. The incidence of blossom end rot increases during conditions of high leaf transpiration (Adams and Ho, 1993) REFERENCES and high enlarging rates of fruits (Yoshida et al., 2007). In the present study, we observed a negative correlation be- Adams, P., Ho, L. C. 1993. Effects of environment on the up- tween the incidence of blossom end rot and the duration of take and distribution of calcium in tomato and on the inci- the maturation period (Table 2). This result is consistent dence of blossom-end rot. Plant Soil 154:127
132. with those of previous studies, because fruit enlarges more Araki, T., Watanabe, S., Wajima, T., Kitano, M., Nakano, Y., Okano, K. 2009. Short-term application of the concen- rapidly at a high temperature. We further observed that trated deep seawater for production of high quality tomatoes treatment with D-psicose reduced the incidence of blossom by single-truss and high density cultivation. Environ. Control end rot when the maturation period was July to August Biol. 47:37
46. (Table 1). This result was repeated in experiment 1 and ex- de Freitas, S. T., Shackel, K. A., Mitcham, E. J. 2011. Abscisic periment 4, both the maturation period was summer (Table acid triggers whole-plant and fruit-specific mechanisms to in- 1). Increasing leaf transpiration is known to inhibit the in- crease fruit calcium uptake and prevent blossom end rot de-
flux of calcium to fruits, and to increase the incidence of velopment in tomato fruit. J. Exp. Bot. 62: 2645 2656. Gosselin, A., Xu, H., Dafiri, M. 1996. Effects of supplemental blossom end rot (Adams and Ho, 1993). Therefore, by re- lighting and fruit thinning on fruit yield and source-sink rela- ducing leaf transpiration, treatment with D-psicose treat- tions of greenhouse tomato plants. J. Jpn. Soc. Hortic. Sci. 65 ment may alleviate drying stress, thereby maintaining the :595
601. influx of calcium to fruits and preventing the incidence of Ishida, Y., Kakibuchi, K., Aritomo, H., Kudo, R., Kozuki, A., blossom end rot. Application of abscisic acid to tomato Izumori, K., Tajima, S., Akimitsu, K., Tanaka, K., Ohkouchi, was previously shown to inhibit transpiration, maintain T. 2011. Effects of rare sugars on the flower bud differen- xylem water potential, and increase xylem flow into fruits, tiation of plants. In: Proc. 5th International Symposium of
thereby preventing the incidence of blossom end rot (de Rare Sugars, Kagawa, 9 12 November, p 60. Ishida, Y., Kakibuchi, K., Kudo, R., Izumori, K., Tajima, S., Freitas et al., 2011). On the other hand, in the present Akimitsu, K., Tanaka, K. 2012. Effects of rare sugars on study, we determined an increased incidence of blossom growth and disease occurrence in head lettuce. Acta. Hortic. end rot in plants treated with D-psicose in winter, and par- 927: 929
934. ticularly in rainy seasons. Nishina et al. (1993) used a fog- Ishigami, K., Horiguchi, M., Nakajima, T., Matsuura, H. 1994. cooling system in summer, and demonstrated a high Studies on the development of growing system for tomatoes incidence of blossom end rot. The temperature and the with high sugar content. (in Japanese with English summary)
relative humidity of this study was probably similar to the Bull. Shizuoka Agric. Exp. Stn. 38:61 72. Ito, H., Niwa, K., Fukuda, M. 1994. Studies on stable produc- rainy season in our present study. Taken together, the re- tion of the high brix tomato by low node-order pinching and sults of our present study and those of previous investiga- dense planting culture. (in Japanese with English summary) tions indicate that inhibition of leaf transpiration results in Res. Bull. Aichi Agric. Res. Ctr. 26: 201
208. decreased incidence of blossom end rot in dry and hot con- Kakibuchi, K., Aritomo, H., Kudo, R., Kozuki, A., Ishida, Y., ditions, and increased incidence of blossom end rot in wet Izumori, K., Tajima, S., Akimitsu, K., Tanaka, K., Ohkouchi, and cool conditions. T. 2011. Study on the use of rare sugars in hydroponics. In: In tomato cultivation, not only sugar content, market- Proc. 5th International Symposium of Rare Sugars, Kagawa, 9
12 November, S37. able yield is important. D-tagatose treatment did not affect Kano, A., Fukumoto, T., Ohtani, K., Yoshihara, A., Ohara, T., the fruit weight and marketable yield (Table 1). D-psicose Tajima, S., Izumori, K., Tanaka, K., Ohkouchi, T., Ishida, Y., treatment decreased marketable yield in winter, but in- Nishizawa, Y., Ichimura, K., Tada, Y., Gomi, K., Akimitsu, creased in summer (Table 1). Although D-psicose treat- K. 2013. The rare sugar D-allose acts as a triggering mole- ment always decreased fruit weight, it decreased the cule of rice defense via ROS generation. J. Exp. Bot. 64: incidence of blossom end rot in summer so that increased 4939
4951. marketable yield. In winter, D-psicose treatment decreased Kano, A., Gomi, K., Yamasaki-Kokudo, Y., Satoh, M., Fukumoto, marketable yield caused by the reduction of fruit weight T., Ohtani, K., Tajima, S., Izumori, K., Tanaka, K., Ishida, Y., Tada, Y., Nishizawa, Y., Akimitsu, K. 2010. A rare sugar, and by the increase of the incidence of blossom end rot. D-allose, confers resistance to rice bacterial blight with However, high sugar content increases the price of tomato upregulation of defense-related genes in Oryza sativa. and may be able to increase the income. Phytopathology 100:85
90. In summary, we have shown that treatment with D- Kano, A., Hosotani, K., Gomi, K., Yamasaki-Kokudo, Y., psicose results in increased sugar content in all cultivation Shirakawa, C., Fukumoto, T., Ohtani, K., Tajima, S., Izumori, seasons, and reduced incidence of blossom end rot in sum- K., Tanaka, K., Ishida, Y., Nishizawa, Y., Ichimura, K., Tada, mer, by inhibiting transpiration and alleviating drying Y., Akimitsu, K. 2011. D-Psicose induces upregulation of defense-related genes and resistance in rice against bacterial stress. Therefore, treatment with D-psicose represents a blight. J. Plant Physiol. 168: 1852
1857. valuable tool for the production of tomato with high soluble Nishina, H., Chuo, I. -H., Tanaka, M., Hashimoto, Y. 1993. solids content, to increase the sugar content in winter and Prevention of occurrence of blossom-end rot of tomato fruits prevent the incidence of blossom end rot in summer. by air flow to fruits and analysis of the mechanism. (in Japanese with English summary) SHITA J. 5:26
38. This work was supported by the Program for Promotion of Noguchi, A., Okuda, Y., Ichimura, M. 2012. Effects of high

Vol. 52, No. 3 (2014)

 Y. YAMADA ET AL.

electrical conductivity of nutrient solution at different devel- Sci. 75: 392
398. opmental stages on yield and fruit quality in tomatoes grown Sakamoto, Y., Watanabe, S., Nakashima, T., Okano, K. 1999. with a single-truss high density planting system. (in Japanese) Effects of salinity at two ripening stages on the fruit quality of J. Agric. Sci. Tokyo Univ. Agric. 57:9
13. single-truss tomato grown in hydroponics. J. Hortic. Sci. 74: Oka, I., Sue, N., Takahashi, H. 2004. Effects of salt application 690
693. on total soluble solids and fruit weight of tomato grown in hy- Yoshida, Y., Matsuno, T., Shingai, A., Goto, T. 2007. Growth, droponics. (in Japanese with English summary) Hortic. Res. yield and fruit quality of tomato as affected by root zone re- (Japan) 3:149
154. striction in combination with solar-mediated fertigation re- Saito, T., Fukuda, N., Nishimura, S. 2006. Effects of salinity gime. (in Japanese with English summary) Sci. Rep. Fac. treatment duration and planting density on size and sugar con- Agr., Okayama Univ. 96:37
42. tent of hydroponically grown tomato fruits. J. Jpn. Soc. Hort.


 Environ. Control Biol.