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Effect of phosphorus on the fruit yield and food value of two landraces of Trichosanthes cucumerina L.- Cucurbitaceae
Food Chemistry Food Chemistry 100 (2007) 1259–1264 www.elsevier.com/locate/foodchem
Analytical, Nutritional and Clinical Methods
Effect of phosphorus on the fruit yield and food value of two landraces of Trichosanthes cucumerina L.- Cucurbitaceae O.C. Adebooye *, F.M. Oloyede Department of Plant Science, Obafemi Awolowo University, Ile-Ife, Nigeria Received 1 April 2005; received in revised form 1 August 2005; accepted 2 October 2005
Abstract Studies were conducted in the early season of 2002 and 2003 at the Teaching and Research Farm, Obafemi Awolowo University, IleIfe, Nigeria to evaluate the effect of phosphorus (P) on fruit yield and chemical composition of two landraces of Trichosanthes cucumerina L. For the purpose of the study, two landraces of T. cucumerina named Landrace I and Landrace II were used. The five levels of phosphorus evaluated were 0, 30, 60, 90 and 120 kg P2O5 ha1 using single super phosphate fertilizer (8% P). Statistical analysis showed that 90 kg P2O5 ha1 gave statistically significant higher fruit yield (16.4 tons ha1) compared to other P levels. The fruit yield of the two Landraces did not differ significantly. Except for crude protein content, the 90 kg P2O5 ha1 produced significantly higher ether extract (1.22 g 100 g1), crude fibre (1.93 g 100 g1), moisture content (90.5 g 100 g1), ash (0.90 g 100 g1), total sugars (0.81 g 100 g1) and ascorbic acid (28.7 mg 100 g1) than other P levels. The essential amino acids compositions were also significantly higher at 90 g 100 g1 compared to other lower P levels. Landrace I had significantly higher ether extract (0.90 g 100 g1) content than Landrace II (0.62 g 100 g1) while Landrace II in turn had significantly higher total sugar (0.76 g 100 g1) compared to Landrace I (0.61 g 100 g1). The essential amino acids composition is high and the oxalate composition is low. The high ascorbic acid and amino acid content together with a low oxalate composition suggested a strong basis for encouraging the cultivation of this indigenous fruit vegetable to augment nutrient requirement, improve diet and consequently alleviate poverty, preserve the biodiversity and increase the gene bank of neglected wild species of high quality nutrient sources. 2005 Elsevier Ltd. All rights reserved. Keywords: Trichosanthes cucumerina L.; Phosphorus; Fruit yield; Nutrient quality
1. Introduction The suitability of snake tomato (Trichosanthes cucumerina L.) for use as a substitute to the regular tomato (Lycopersicon esculentum (L.) Mil) is due to its sweet tasting, aromatic and blood red pasty endocarp pulp when it is fully ripe. It is known that the paste of T. cucumerina does not go sour as fast as the paste of L. esculentum. Survey conducted in Southwest Nigeria also showed that T. cucumerina fruit is used as substitute to the regular tomato by the poor rural people especially, only during the off-season when prices of regular tomato are very high; suggesting
*
Corresponding author. Tel.: +234 8033783121; fax: +234 36232401. E-mail address: [email protected] (O.C. Adebooye).
0308-8146/$ - see front matter 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2005.10.002
that its consumption is directly related to the level of poverty (Onagoruwa Pers. Com). Yadava and Yasmeen (1994) reported that T. cucumerina is used as a tonic and in curing coughs and that the seeds are used as purgative, anthelmintic and in the treatment of syphilis. There is dearth of information in the literature on cultivation practices for T. cucumerina while the literature is replete with information on the general cultivation packages for L. esculentum. Despite all the attention concentrated on L. esculentum, reports showed that it is not exceedingly rich in any nutrient (Stevens, 1974). For example, Adebooye (2001) reported that the vitamin C content of tomato is about 15.0 mg 100 g1 fruit, which is only about 50% of that of sweet orange (Citrus sinensis (L.) Osb.) 10% that of pepper (Capsicum frutescens L.), and 8% that of carrot (Daucus carota L.). Studies by Adebooye,
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Oloyede, Opabode, and Onagoruwa (2005) on the chemical composition of three landrace morphotypes of T. cucumerina showed that the seeds of T. cucumerina are good sources of crude protein (26.2–26.6 g 100 g1), fat (44.6– 57.2 g 100 g1), phosphorus (78.0–81.5 mg 100 g1) and calcium (41.0–46.7 mg 100 g1) while the pulp is a good source of ascorbic acid (23.1–23.3 mg 100 g1) and the anti-nutritional oxalate content was low (1.20– 2.62 g 100 g1) suggesting that mineral nutrients (calcium and magnesium) will not be held in unavailable form. With respect to mineral nutrition of T. cucumerina, there is dearth of information in the literature. A mineral element that has been reported to be important for fruit growth and development is phosphorus (P). Studies by the International Institute of Tropical Agriculture (IITA), Ibadan Nigeria in 1989–1998 showed that phosphorus deficiency is a major yield-limiting factor in several locations in southwest Nigeria. As reported by Aduayi, Chude, Adebusuyi, and Olayiwola (2002), P is the mineral nutrient needed by tomato plant in largest quantity in Southwest Nigeria compared to other macronutrients. Widespread P deficiency in Nigerian soils results from the low organic matter content and high P-fixation capacity of the soils (Mokwunye, 1979, 1999). Based on our understanding of the fertility status and P requirement of farmlands at the Obafemi Awolowo University, Ile-Ife, Nigeria, this study was designed to investigate the effect of five levels of phosphorus fertilizer on fruit yield and nutrient composition of two landraces of T. cucumerina. 2. Materials and methods The studies were conducted at the Teaching and Research Farm, Obafemi Awolowo University, Ile-Ife, Nigeria, during the early season of 2002 and repeated during the early season of 2003. The site is located on latitude 0728 0 N and longitude 0433 0 E and about 244 m above sea level. Ile-Ife lies in the rainforest vegetation characterized by bimodal rainfall pattern with peaks in June and September. The average rainfalls were 1300 mm and 1365 mm while the average daily temperatures were 28.5 C and 29 C at the study location during 2002 and 2003, respectively. From the experimental site, 10 core soil samples were taken. The samples were mixed together to form a composite sample. Thereafter the soil sample was air-dried, and passed through a 2 mm sieve. Soil total N and organic carbon in soil were determined by the Kjeldahl method and Walkley and Black (1934) method, respectively. Available phosphorus was determined by Bray 1-P method (Bray & Kurtz, 1945) while K, Ca and Mg were first extracted using neutral normal NH4OAc (Knusden, Petereson, & Prat, 1984) thereafter, K was determined by flame photometry while Ca and Mg were determined by using atomic absorption spectrophotometer model BUCK Scientific 200 A. The experiment was a split plot design in a factorial arrangement with four replications. The factors were two landraces of T. cucumerina: Landrace I has long fruit with
deep green background and white stripes when unripe while Landrace II has light green long fruit when unripe; and four levels of phosphorus with one control (0, 30, 60, 90 and 120 kg P2O5 ha1). The landraces served as main plots while the P levels served as the sub plots. The P levels were calculated based on the results of soil analyses which showed that available P (Bray-P) was 5.80 mg/kg and was considered inadequate when compared with the critical value of 10–16 mg/kg for southwest Nigeria, (Sobulo, Fayemi, & Agboola, 1975; Agbede & Aduayi, 1978; Aduayi et al., 2002). Other macro and micronutrients were found to be present at adequate levels in the soil used for this study. The plot size was 9 m · 4 m. Paths between the plots and the replicates were 2 m each. The plants were raised directly from seeds and there were 2 plants per stand. The plants were spaced 1.0 m · 1.0 m to give a total of 5 rows and 100 plants per plot. Plantings were done on April 16th 2002 and April 21st 2003, when rainfall had stabilized. The P was applied 15 days after planting using single super-phosphate fertilizer (8% P). Basal application of Nitrogen and Potassium was done at the rates of 40 and 30 kg ha1, respectively at 15 days after planting. Data were collected from the three middle rows while the first and fifth rows served as guard rows. Data were collected on number of marketable fruits harvested, number of flowers aborted and the fruit yield of the two variants. At full ripening, fifty fruits of each landrace per phosphorus level were harvested separately from the four middle rows in each plot. The fruits were taken to the laboratory and weighed. Thereafter, the fruits were split open; the seeds were extracted and then depulped. The pulp for each morphotype and phosphorus level was dried in a Gallenkamp oven at 80 C for 48 h. The dried pulp samples were ground into powder separately using a Wiley micro hammer stainless mill. The pulp samples at the different P levels were subjected to chemical analyses separately. To ensure quality control, the ground samples were stored separately in screw-capped bottles and stored in a refrigerator at 5 C until they were needed for analyses. Fresh samples were used for determination of total sugar immediately after harvest. All the chemical analyses described below were carried out in triplicate using the routine chemical analytical methods of Association of Official Agricultural Chemists (AOAC) (1995). To 5 g fresh pulp sample was added water at 80 C for 1 h to ensure that denaturation of enzyme occurred thus avoiding enzyme-mediated changes during extraction. The extract was heated with anthrone reagent in a boiling water bath for 1 h. The sample was filtered and the absorbance of the filtrate was read at 620 nm with a spectrophotometer. The essential amino acids were read directly using the Beckman 126AA amino acid analyzer following the methods of Spitz (1973); and Moore (1963). The ether extract content was determined by Soxhlet extraction method (Association of Official Agricultural Chemists (AOAC) (1995)). About 2 g of the ground sample
O.C. Adebooye, F.M. Oloyede / Food Chemistry 100 (2007) 1259–1264
was put into a fat free extraction thimble and plugged lightly with cotton wool, petroleum ether was added up to 300 ml mark and the content was boiled for 2 h ensuring that the ether siphon until the siphoning was no longer noticed. After draining, the extraction thimble was removed and dried. The thimble was weighed and ether extract content determined by difference. Nitrogen content was determined by the Kjedhal method. The crude protein content was determined by multiplying the nitrogen value by factor 6.25. The moisture content was determined by drying 10.0 g of the ground cotyledon samples in the oven at 80 C for 48 h. The proportional difference in weight converted to percentage was expressed as percent moisture content. The ash contents of the samples were obtained by digesting 5 g ground cotyledon sample in a muffle furnace at 550 C for 1 h. The proportional difference in weight converted to percentage is expressed as percent ash content. The crude fibre was determined by digesting 5.0 g of the ground cotyledon sample in 1.25% H2SO4 and 1.25%NaOH. The oxalate content was determined by using the HPLC method as described by Wilson, Philip, and Robert (1982). The ascorbic acid was determined by extracting 10 g of fresh pulp sample in 90 ml distilled water for one hour. The mixture was filtered and stored in at 5 C. A standard indophenol solution was prepared and 2 ml of it was filled in a burette while the 10 ml sample filtrate was filled in the burette. Titration was done and the titre value was used in calculating the ascorbic acid concentration. Data collected were subjected to analyses of variance (ANOVA) using the standard method for split plot design according to Steele and Torrie (1995). Means, where significantly different were separated using the DuncanÕs multiple range test (DMRT) at 5% level of probability. 3. Results and discussion Table 1 shows the result of ANOVA for the various parameters determined. P levels significantly affected all the parameters except oxalate composition of the two landraces of T. cucumerina. Landrace only significantly affected ether extracts and total sugar contents of T. cucumerina while the interaction of landrace and phosphorus had no significant effect on all the parameters measured. Table 2 shows that the number of marketable fruits harvested per
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Table 2 Effect of phosphorus on average fruit yield of snake tomato across landraces P level kg P2O5 ha1
No of marketable fruits harvested plant1
Fruit yield (t ha1)
No of rotted fruits plant1
No of aborted flowers plant1
0 30 60 90 120
6.1d 7.9c 9.4b 13.1a 13.0a
3.1d 6.8c 9.4b 16.4a 16.1a
10.3a 7.5b 6.2c 4.5d 4.5d
22.9a 17.8b 15.8c 9.5d 9.6d
Means with the same letter in each column are not significantly different at 5% level of probability according to DuncanÕs multiple range test. Values are means of 2002 and 2003 studies.
plant under 90 and 120 kg P2O5 ha1 did not differ significantly but they were significantly higher than those harvested under all other phosphorus levels. The fruits harvested under 90 kg P2O5 ha1 was 38.3% higher than those harvested under 60 kg P2O5 ha1 while the number of fruits harvested under 60 kg P2O5 ha1 was 19.0% higher than those harvested under 30 kg P2O5 ha1. Also, the number of fruit harvested under 30 kg P2O5 ha1 was 29.5% higher than those that did not receive phosphorus fertilizer. The same trend was obtained in the fruit yield at different levels of phosphorus application. The number of flowers aborted per plant and the number of fruit rotted were significantly affected by the phosphorus level. Plants under 90 and 120 kg P2O5 ha1 aborted significantly fewer numbers of flowers compared to plants under 0, 30 and 60 kg P2O5 ha1. Plants that did not receive P aborted significantly higher number of flowers compared to other P levels. The results showed that there was no significant difference in the number of flowers aborted between the plants under 90 and 120 kg P2O5 ha1. It can also be deducted from the result that the lower the level of applied phosphorus the higher the number of flowers aborted. The same result was obtained in the effect of P level on the number of fruits rotted. There was no significant difference in the number of fruits rotted between the plants under 90 and 120 kg P2O5 ha1, but the number of rotted fruits increased with decreasing level of P applied. This overall result shows that at 90 kg P2O5 ha1 the plants yielded
Table 1 ANOVA table for affects of landrace and P level on fruit production characteristics, fruit yield, and quality factors for Snake tomato Source
Numbers of Aborted flowers
Rotted fruit
Landrace (L) P level (P) Interaction L·P
ns **
ns **
ns
ns
Marketable fruit
Fruit yield
Ether extract
Protein
Fiber
ns **
ns **
* **
ns ns
ns
ns
ns
ns
ns, *indicates non-significant, or significant at P 6 0.05, respectively, ANOVA.
Crude
Moisture
Ash
Total sugar
Ascorbic acid
Oxalate
ns **
ns **
ns **
* **
ns **
ns ns
ns
ns
ns
ns
ns
ns
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O.C. Adebooye, F.M. Oloyede / Food Chemistry 100 (2007) 1259–1264
optimally. Aduayi et al. (2002) had earlier suggested that P recommendation in the forest zone of Southern Nigeria be 90 kg P2O5 ha1 for tomato plants cultivation. Previous studies by Zekri and Obreza (2003) reported that when P is too low, citrus trees will exhibit limited flower development with reduced fruit set and fruit yield. Also, Steven (2002) in his study of foliar sprays to increase fruit size and yield in Californian citrus reported that phosphorus (phosphite) and potassium mixture at 7.3 L ha1 increase yield without reducing fruit size. The significant effect of P as shown in this paper on number of marketable fruits, aborted flowers and overall fruit yield of T. cucumerina may be explained by the central role played by P in energy systems of plants. Adams (1986) reported that when P level is optimum, much of energy required for plant metabolism which is stored chemically in the form of complex organic phosphates adenosine triphosphate (ATP) will be made available and released as required. Therefore, important chemical processes involved in growth will be driven steadily. The significant effect of P on the number of flowers aborted and number of rotted fruits in T. cucumerina as shown in this study was also consistent with the findings of Skinner, Cook, and Matthews (1988); and Skinner and Matthews (1989), who reported that P deficiency in grapevines inhibit the initiation and maintenance of fruit clusters and flowers within developing buds. As a result, fruit yield from P-deficient grapevines is reduced. Zekri and Obreza (2003) in their studies on macronutrient deficiencies in citrus, reported that when P is too low, leaves shed prematurely and fruit can drop before normal harvesting time. They also reported that trees will exhibit limited flower development with reduced fruit set and fruit yield. This furthermore corroborates the findings of Lauer and Blevins (1989) on soybean that the primary effect of limited P on soybean reproductive growth was to increase flower and pod abortion. The effect of phosphorus on the proximate composition of snake tomato is presented in Table 3. The fruits under 90 kg P2O5 ha1 and 120 kg P2O5 ha1 had higher ether extract and crude fibre content compared to the fruits under every other level of P. At 0 and 30 kg P2O5 ha1 there was no significant difference in ether extract composition. P levels did not significantly affect crude protein content. The crude fibre contents followed perfectly the trend observed for ether extract.
The moisture contents at 60, 90 and 120 kg P2O5 ha1 were significantly higher than the contents at 0 and 30 kg P2O5 ha1. There was no significant difference among the moisture contents at 60, 90, and 120 kg P2O5 ha1. The ash contents followed the same trend as the moisture content. The total sugar contents at 90 and 120 kg P2O5 ha1 was significantly higher than at all other phosphorus levels. Total sugar content was 87.6%, 54.3% and 39.3% higher at 90 kg P2O5 ha1 than at 0, 30 and 60 kg P2O5 ha1, respectively. The ascorbic acid contents at 90 and 120 kg P2O5 ha1 were significantly higher than at all other phosphorus levels. The amount of ascorbic acid at 60 kg P2O5 ha1 was also significantly higher than the contents at 0 and 30 kg P2O5 ha1. At 0 kg P2O5 ha1, the fruit had the least content of ascorbic acid. The oxalate content (2.4–2.6 mg 100 g1) was not significantly affected by phosphorus levels. The effect of Landraces on the proximate composition of snake-tomato fruit is presented in Table 4. The ether extract content was 48.4% higher in Landrace I compared to Landrace II. The result also showed that Landrace II was 24.6% higher in total sugar content compared to Landrace I. The crude protein, crude fibre, moisture, ash oxalate and ascorbic contents of the two variants were not significantly different. Table 5 shows the essential amino acid composition of the snake tomato as affected by phosphorus levels. Results show that all the amino acids increased with increasing P levels up to 90 kg P2O5 ha1. The result also shows that all the amino acids were present in significantly higher amounts at 90 and 120 kg P2O5 ha1 than at other P levels. It can be suggested from these results that P plays a significant role in amino acid production because the amino acid composition declined as the P level reduced. The values of the different amino acids showed that T. cucumerina is a good source of amino acids when compared with the oranges, pepper and tomato earlier reported by Adebooye (2001). The implication of this is that T. cucumerina can be a good source of essential amino acids for man and animals consumption. Amino acids are the ‘‘building blocks’’ of the body protein. Besides building cells and repairing tissue, they form antibodies to combat invading bacteria and viruses; they are part of the enzyme and hormonal system; they build nucleoproteins (RNA and DNA); they carry oxygen throughout the body and participate in muscle activity (Lehninger, 1990).
Table 3 Effect of phosphorus on the proximate composition of snake tomato fruits across landraces P Levels kg P2O5 ha1
Ether extract
Crude protein
Crude fibre
Moisture
Ash
Total sugar
1
0.64c 0.66c 0.90b 1.22a 1.19a
Oxalate acid 1
g 100 g 0 30 60 90 120
Ascorbic mg 100 g
1.84a 1.92a 1.85a 2.39a 2.02a
1.34c 1.47c 1.63b 1.93a 1.90a
88.1b 87.9b 89.5a 90.5a 89.7a
0.64b 0.64b 0.80a 0.90a 0.89a
0.55c 0.59c 0.70b 0.81a 0.78a
15.3d 18.6c 20.6b 28.7a 27.7a
2.4a 2.6a 2.5a 2.4a 2.4a
Means with the same letter are not significantly different at 5% level of probability according to DuncanÕs Multiple range tests. Values are means of 2002 and 2003 studies.
O.C. Adebooye, F.M. Oloyede / Food Chemistry 100 (2007) 1259–1264
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Table 4 The effect of Landraces on the proximate composition of snake tomato fruits across phosphorus levels Ether extract
Crude protein
Crude fibre
Moisture
Ash
Total sugar
Ascorbic acid
1
mg 100 g
g 100 g Landrace 1 Landrace 2 LSD 5%
Oxalate
1
0.90 0.62 0.24
2.06 1.94 NS
1.63 1.53 NS
88.8 89.0 NS
0.76 0.78 NS
0.61 0.76 0.10
20.3 19.2 NS
2.80 2.50 NS
Means with the same letter are not significantly different at 5% level of probability NS = not significant at 5% level of probability. Values are means of 2002 and 2003 studies. Table 5 Effect of P levels on Amino acid composition of T. cucumerina across phosphorus levels Amino acid
0
30
60
90
120
14.8b 1.45b 2.51b 6.05b 1.42b 0.56b 3.05b
17.1c 1.91c 3.55c 7.60c 1.76c 0.75c 4.50c
19.9d 2.85d 4.80d 8.65d 2.15d 0.96d 6.90d
18.9d 2.84d 4.91d 9.05d 2.12d 0.86d 6.55d
kg P2O5 ha1 Arginine Histidine Isoleucine Leucine Methionine Tryptophan Valine
12.2a 1.10a 2.30a 5.68a 0.94a 0.45a 2.05a
All values are expressed on g 16 g1 N. All values are means of 2002 and 2003 studies. In each row, means followed by different alphabets are significantly different at 5% level of probability.
4. Conclusion
References
The results of this study showed that the protein, fat, ascorbic acid and amino acid composition of T. cucumerina are high enough and compare favourably with the composition of other known important edible fruits. The high quantity of its paste, its palatability and aroma are additional good qualities of T. cucumerina. The low and safe oxalate content also suggested that the availability of Ca and Mg in T. cucumerina for man and animal use would not be threatened. Further studies on the improvement of this novel plant are a worthwhile effort to broaden the food base and widen the income base. It is also important to conduct further studies into the relationship between P supply and amino acid synthesis in this plant because as P level increased, the essential amino acids contents increased up to 90 kg P2O5 ha1. Improving this plant will also help in its conservation and prevent it from the threat of extinction. It is globally acknowledged today that many plants are facing threat because, they have for long been neglected by research and development process and T. cucumerina falls into this category.
Adams, P. (1986). Mineral nutrition. In J. G. Atherton & J. Rudick (Eds.), The tomato crop (pp. 281–324). New York: Chapman and Hall Publishers. Adebooye, O. C. (2001). Effects of intra-row spacing and phosphorus levels on growth and post-harvest qualities of fruits of three varieties of tomato (Lycopersicon lycopersicum (L.) Karst). Unpublished Ph.D. Thesis Department of Agronomy, University of Ibadan, Ibadan, Nigeria. 166pp. Adebooye, O. C., Oloyede, F. M., Opabode, J. T., & Onagoruwa, O. O. (2005). Fruit characteristics and nutrient composition of landrace morphotypes of snake tomato. Journal of Vegetable Science, 11(4), in press. Aduayi, E. A., Chude, V. O., Adebusuyi, B. A., & Olayiwola, S. O. (2002). Fertilizer use and management practices for crops in Nigeria (3rd ed.). Federal Fertilizer Department, Federal Ministry of Agriculture and Rural Development, Abuja, pp. 90. Agbede, O. O, & Aduayi, E. A. (1978). Role of P and Mg in some growth components and yield of potted Ife Plum Tomato plants in two soil series of southwest Nigeria. East Africa Agriculture and Forestry Journal, 43, 246–251. AOAC (1995). Official methods of analysis (15th ed.). Washington, DC: Association of Official Analytical Chemists, 1120 pp.. Bray, R. H., & Kurtz, L. T. (1945). Determination of total organic and available forms of phosphorus in soils. Soil Science, 59, 39–45. Knusden, D., Petereson, G. A., & Prat, P. F. (1984). Lithium, sodium and potassium. In A. L. Page et al. (Eds.), Methods of soil analyses Part 2 (2nd ed. Agronomy Monograph 9, pp. 225–246). Madison: ASA and SSSA. Lauer, M. J., & Blevins, D. G. (1989). Flowering and podding characteristics on the main stem of soybean grown on varying levels of phosphorus nutrition. Journal of Plant Nutrition, 12, 1061–1072. Lehninger, A. L. (1990). Biochemistry. New York: Worth Publishers Inc, 1104 pp. Mokwunye, A. U. (1979). P fertilizers in Nigerian Savanna soils. II. Evaluation of three PO4 sources applied to maize at Samaru. Tropical Agriculture, 56, 65–68.
Acknowledgements The Central Analytical Laboratory and the Animal Science Analytical Laboratory, Obafemi Awolowo University, Ile-Ife, Nigeria carried out the proximate and mineral analyses. The United Nations University/Institute for Natural Resources in Africa (UNU/INRA) funded this research through a project on nutritional studies of underexploited African vegetables (INRA 2004/0002).
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Mokwunye, A. U. (1999). Food security through science. African Recovery, 44, 28–29. Moore, S. (1963). On the determination of cystine as cysteic acid. Journal of Biological Chemistry, 238, 235–237. Skinner, P. W., Cook, J. A., & Matthews, M. A. (1988). Responses of grapevine cvs Chenin Blanc and Chardonnay to phosphorus fertilizer applications under phosphorus-limited conditions. Vitis, 27, 95–109. Skinner, P. W., & Matthews, M. A. (1989). Reproductive development in grape (Vitis vinifera L.) under phosphorus limited conditions. Scientific Horticulture, 38, 49–60. Spitz, H. D. (1973). A new approach for sample preparation of protein hydrolysates for amino acid analysis. Analytical Biochemistry, 56, 66–73. Steele, S. G. D., & Torrie, J. H. (1995). Principles and procedures of statistics. US: McGraw-Hill Book Cmpany, Inc, 481pp. Steven, F. (2002) Foliar sprays to increase fruit size and yield in California citrus. (NSW, Agriculture, Dareton).
Sobulo, R. A., Fayemi, A. A., & Agboola, A. (1975). Nutrient requirements of tomatoes in SW Nigeria II. Foliar analysis for assessing N, P and K requirements. Experimental Agriculture, 1, 137–143. Stevens, M. A. (1974). In P. L. White (Ed.), Varieties influence on nutritional value (pp. 22–30). Frutura Publishing Co Inc. Walkley, A., & Black, I. A. (1934). An examination of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic titration method. Soil Science, 37, 29–38. Wilson, C. W., III, Philip, E. S., & Robert, J. K. Jr., (1982). Analysis of oxalic acid in carambola (Averrhoa carambola l.) and spinach by highperformance liquid chromatography. Journal of Agriculture and Food Chemistry, 30(6), 1106–1108. Yadava, R. N., & Yasmeen, S. (1994). Trichosanthes cucumerina L. Phytochemistry Journal, 36, 1519. Zekri, M., & Obreza, T. A. (2003). Macronutrient deficiency in citrus: Nitrogen, Phosphorus and Potassium. University of Florida, Institute for Food and Agricultural Sciences. 2–3pp.
Analytical, Nutritional and Clinical Methods
Effect of phosphorus on the fruit yield and food value of two landraces of Trichosanthes cucumerina L.- Cucurbitaceae O.C. Adebooye *, F.M. Oloyede Department of Plant Science, Obafemi Awolowo University, Ile-Ife, Nigeria Received 1 April 2005; received in revised form 1 August 2005; accepted 2 October 2005
Abstract Studies were conducted in the early season of 2002 and 2003 at the Teaching and Research Farm, Obafemi Awolowo University, IleIfe, Nigeria to evaluate the effect of phosphorus (P) on fruit yield and chemical composition of two landraces of Trichosanthes cucumerina L. For the purpose of the study, two landraces of T. cucumerina named Landrace I and Landrace II were used. The five levels of phosphorus evaluated were 0, 30, 60, 90 and 120 kg P2O5 ha1 using single super phosphate fertilizer (8% P). Statistical analysis showed that 90 kg P2O5 ha1 gave statistically significant higher fruit yield (16.4 tons ha1) compared to other P levels. The fruit yield of the two Landraces did not differ significantly. Except for crude protein content, the 90 kg P2O5 ha1 produced significantly higher ether extract (1.22 g 100 g1), crude fibre (1.93 g 100 g1), moisture content (90.5 g 100 g1), ash (0.90 g 100 g1), total sugars (0.81 g 100 g1) and ascorbic acid (28.7 mg 100 g1) than other P levels. The essential amino acids compositions were also significantly higher at 90 g 100 g1 compared to other lower P levels. Landrace I had significantly higher ether extract (0.90 g 100 g1) content than Landrace II (0.62 g 100 g1) while Landrace II in turn had significantly higher total sugar (0.76 g 100 g1) compared to Landrace I (0.61 g 100 g1). The essential amino acids composition is high and the oxalate composition is low. The high ascorbic acid and amino acid content together with a low oxalate composition suggested a strong basis for encouraging the cultivation of this indigenous fruit vegetable to augment nutrient requirement, improve diet and consequently alleviate poverty, preserve the biodiversity and increase the gene bank of neglected wild species of high quality nutrient sources. 2005 Elsevier Ltd. All rights reserved. Keywords: Trichosanthes cucumerina L.; Phosphorus; Fruit yield; Nutrient quality
1. Introduction The suitability of snake tomato (Trichosanthes cucumerina L.) for use as a substitute to the regular tomato (Lycopersicon esculentum (L.) Mil) is due to its sweet tasting, aromatic and blood red pasty endocarp pulp when it is fully ripe. It is known that the paste of T. cucumerina does not go sour as fast as the paste of L. esculentum. Survey conducted in Southwest Nigeria also showed that T. cucumerina fruit is used as substitute to the regular tomato by the poor rural people especially, only during the off-season when prices of regular tomato are very high; suggesting
*
Corresponding author. Tel.: +234 8033783121; fax: +234 36232401. E-mail address: [email protected] (O.C. Adebooye).
0308-8146/$ - see front matter 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2005.10.002
that its consumption is directly related to the level of poverty (Onagoruwa Pers. Com). Yadava and Yasmeen (1994) reported that T. cucumerina is used as a tonic and in curing coughs and that the seeds are used as purgative, anthelmintic and in the treatment of syphilis. There is dearth of information in the literature on cultivation practices for T. cucumerina while the literature is replete with information on the general cultivation packages for L. esculentum. Despite all the attention concentrated on L. esculentum, reports showed that it is not exceedingly rich in any nutrient (Stevens, 1974). For example, Adebooye (2001) reported that the vitamin C content of tomato is about 15.0 mg 100 g1 fruit, which is only about 50% of that of sweet orange (Citrus sinensis (L.) Osb.) 10% that of pepper (Capsicum frutescens L.), and 8% that of carrot (Daucus carota L.). Studies by Adebooye,
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Oloyede, Opabode, and Onagoruwa (2005) on the chemical composition of three landrace morphotypes of T. cucumerina showed that the seeds of T. cucumerina are good sources of crude protein (26.2–26.6 g 100 g1), fat (44.6– 57.2 g 100 g1), phosphorus (78.0–81.5 mg 100 g1) and calcium (41.0–46.7 mg 100 g1) while the pulp is a good source of ascorbic acid (23.1–23.3 mg 100 g1) and the anti-nutritional oxalate content was low (1.20– 2.62 g 100 g1) suggesting that mineral nutrients (calcium and magnesium) will not be held in unavailable form. With respect to mineral nutrition of T. cucumerina, there is dearth of information in the literature. A mineral element that has been reported to be important for fruit growth and development is phosphorus (P). Studies by the International Institute of Tropical Agriculture (IITA), Ibadan Nigeria in 1989–1998 showed that phosphorus deficiency is a major yield-limiting factor in several locations in southwest Nigeria. As reported by Aduayi, Chude, Adebusuyi, and Olayiwola (2002), P is the mineral nutrient needed by tomato plant in largest quantity in Southwest Nigeria compared to other macronutrients. Widespread P deficiency in Nigerian soils results from the low organic matter content and high P-fixation capacity of the soils (Mokwunye, 1979, 1999). Based on our understanding of the fertility status and P requirement of farmlands at the Obafemi Awolowo University, Ile-Ife, Nigeria, this study was designed to investigate the effect of five levels of phosphorus fertilizer on fruit yield and nutrient composition of two landraces of T. cucumerina. 2. Materials and methods The studies were conducted at the Teaching and Research Farm, Obafemi Awolowo University, Ile-Ife, Nigeria, during the early season of 2002 and repeated during the early season of 2003. The site is located on latitude 0728 0 N and longitude 0433 0 E and about 244 m above sea level. Ile-Ife lies in the rainforest vegetation characterized by bimodal rainfall pattern with peaks in June and September. The average rainfalls were 1300 mm and 1365 mm while the average daily temperatures were 28.5 C and 29 C at the study location during 2002 and 2003, respectively. From the experimental site, 10 core soil samples were taken. The samples were mixed together to form a composite sample. Thereafter the soil sample was air-dried, and passed through a 2 mm sieve. Soil total N and organic carbon in soil were determined by the Kjeldahl method and Walkley and Black (1934) method, respectively. Available phosphorus was determined by Bray 1-P method (Bray & Kurtz, 1945) while K, Ca and Mg were first extracted using neutral normal NH4OAc (Knusden, Petereson, & Prat, 1984) thereafter, K was determined by flame photometry while Ca and Mg were determined by using atomic absorption spectrophotometer model BUCK Scientific 200 A. The experiment was a split plot design in a factorial arrangement with four replications. The factors were two landraces of T. cucumerina: Landrace I has long fruit with
deep green background and white stripes when unripe while Landrace II has light green long fruit when unripe; and four levels of phosphorus with one control (0, 30, 60, 90 and 120 kg P2O5 ha1). The landraces served as main plots while the P levels served as the sub plots. The P levels were calculated based on the results of soil analyses which showed that available P (Bray-P) was 5.80 mg/kg and was considered inadequate when compared with the critical value of 10–16 mg/kg for southwest Nigeria, (Sobulo, Fayemi, & Agboola, 1975; Agbede & Aduayi, 1978; Aduayi et al., 2002). Other macro and micronutrients were found to be present at adequate levels in the soil used for this study. The plot size was 9 m · 4 m. Paths between the plots and the replicates were 2 m each. The plants were raised directly from seeds and there were 2 plants per stand. The plants were spaced 1.0 m · 1.0 m to give a total of 5 rows and 100 plants per plot. Plantings were done on April 16th 2002 and April 21st 2003, when rainfall had stabilized. The P was applied 15 days after planting using single super-phosphate fertilizer (8% P). Basal application of Nitrogen and Potassium was done at the rates of 40 and 30 kg ha1, respectively at 15 days after planting. Data were collected from the three middle rows while the first and fifth rows served as guard rows. Data were collected on number of marketable fruits harvested, number of flowers aborted and the fruit yield of the two variants. At full ripening, fifty fruits of each landrace per phosphorus level were harvested separately from the four middle rows in each plot. The fruits were taken to the laboratory and weighed. Thereafter, the fruits were split open; the seeds were extracted and then depulped. The pulp for each morphotype and phosphorus level was dried in a Gallenkamp oven at 80 C for 48 h. The dried pulp samples were ground into powder separately using a Wiley micro hammer stainless mill. The pulp samples at the different P levels were subjected to chemical analyses separately. To ensure quality control, the ground samples were stored separately in screw-capped bottles and stored in a refrigerator at 5 C until they were needed for analyses. Fresh samples were used for determination of total sugar immediately after harvest. All the chemical analyses described below were carried out in triplicate using the routine chemical analytical methods of Association of Official Agricultural Chemists (AOAC) (1995). To 5 g fresh pulp sample was added water at 80 C for 1 h to ensure that denaturation of enzyme occurred thus avoiding enzyme-mediated changes during extraction. The extract was heated with anthrone reagent in a boiling water bath for 1 h. The sample was filtered and the absorbance of the filtrate was read at 620 nm with a spectrophotometer. The essential amino acids were read directly using the Beckman 126AA amino acid analyzer following the methods of Spitz (1973); and Moore (1963). The ether extract content was determined by Soxhlet extraction method (Association of Official Agricultural Chemists (AOAC) (1995)). About 2 g of the ground sample
O.C. Adebooye, F.M. Oloyede / Food Chemistry 100 (2007) 1259–1264
was put into a fat free extraction thimble and plugged lightly with cotton wool, petroleum ether was added up to 300 ml mark and the content was boiled for 2 h ensuring that the ether siphon until the siphoning was no longer noticed. After draining, the extraction thimble was removed and dried. The thimble was weighed and ether extract content determined by difference. Nitrogen content was determined by the Kjedhal method. The crude protein content was determined by multiplying the nitrogen value by factor 6.25. The moisture content was determined by drying 10.0 g of the ground cotyledon samples in the oven at 80 C for 48 h. The proportional difference in weight converted to percentage was expressed as percent moisture content. The ash contents of the samples were obtained by digesting 5 g ground cotyledon sample in a muffle furnace at 550 C for 1 h. The proportional difference in weight converted to percentage is expressed as percent ash content. The crude fibre was determined by digesting 5.0 g of the ground cotyledon sample in 1.25% H2SO4 and 1.25%NaOH. The oxalate content was determined by using the HPLC method as described by Wilson, Philip, and Robert (1982). The ascorbic acid was determined by extracting 10 g of fresh pulp sample in 90 ml distilled water for one hour. The mixture was filtered and stored in at 5 C. A standard indophenol solution was prepared and 2 ml of it was filled in a burette while the 10 ml sample filtrate was filled in the burette. Titration was done and the titre value was used in calculating the ascorbic acid concentration. Data collected were subjected to analyses of variance (ANOVA) using the standard method for split plot design according to Steele and Torrie (1995). Means, where significantly different were separated using the DuncanÕs multiple range test (DMRT) at 5% level of probability. 3. Results and discussion Table 1 shows the result of ANOVA for the various parameters determined. P levels significantly affected all the parameters except oxalate composition of the two landraces of T. cucumerina. Landrace only significantly affected ether extracts and total sugar contents of T. cucumerina while the interaction of landrace and phosphorus had no significant effect on all the parameters measured. Table 2 shows that the number of marketable fruits harvested per
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Table 2 Effect of phosphorus on average fruit yield of snake tomato across landraces P level kg P2O5 ha1
No of marketable fruits harvested plant1
Fruit yield (t ha1)
No of rotted fruits plant1
No of aborted flowers plant1
0 30 60 90 120
6.1d 7.9c 9.4b 13.1a 13.0a
3.1d 6.8c 9.4b 16.4a 16.1a
10.3a 7.5b 6.2c 4.5d 4.5d
22.9a 17.8b 15.8c 9.5d 9.6d
Means with the same letter in each column are not significantly different at 5% level of probability according to DuncanÕs multiple range test. Values are means of 2002 and 2003 studies.
plant under 90 and 120 kg P2O5 ha1 did not differ significantly but they were significantly higher than those harvested under all other phosphorus levels. The fruits harvested under 90 kg P2O5 ha1 was 38.3% higher than those harvested under 60 kg P2O5 ha1 while the number of fruits harvested under 60 kg P2O5 ha1 was 19.0% higher than those harvested under 30 kg P2O5 ha1. Also, the number of fruit harvested under 30 kg P2O5 ha1 was 29.5% higher than those that did not receive phosphorus fertilizer. The same trend was obtained in the fruit yield at different levels of phosphorus application. The number of flowers aborted per plant and the number of fruit rotted were significantly affected by the phosphorus level. Plants under 90 and 120 kg P2O5 ha1 aborted significantly fewer numbers of flowers compared to plants under 0, 30 and 60 kg P2O5 ha1. Plants that did not receive P aborted significantly higher number of flowers compared to other P levels. The results showed that there was no significant difference in the number of flowers aborted between the plants under 90 and 120 kg P2O5 ha1. It can also be deducted from the result that the lower the level of applied phosphorus the higher the number of flowers aborted. The same result was obtained in the effect of P level on the number of fruits rotted. There was no significant difference in the number of fruits rotted between the plants under 90 and 120 kg P2O5 ha1, but the number of rotted fruits increased with decreasing level of P applied. This overall result shows that at 90 kg P2O5 ha1 the plants yielded
Table 1 ANOVA table for affects of landrace and P level on fruit production characteristics, fruit yield, and quality factors for Snake tomato Source
Numbers of Aborted flowers
Rotted fruit
Landrace (L) P level (P) Interaction L·P
ns **
ns **
ns
ns
Marketable fruit
Fruit yield
Ether extract
Protein
Fiber
ns **
ns **
* **
ns ns
ns
ns
ns
ns
ns, *indicates non-significant, or significant at P 6 0.05, respectively, ANOVA.
Crude
Moisture
Ash
Total sugar
Ascorbic acid
Oxalate
ns **
ns **
ns **
* **
ns **
ns ns
ns
ns
ns
ns
ns
ns
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O.C. Adebooye, F.M. Oloyede / Food Chemistry 100 (2007) 1259–1264
optimally. Aduayi et al. (2002) had earlier suggested that P recommendation in the forest zone of Southern Nigeria be 90 kg P2O5 ha1 for tomato plants cultivation. Previous studies by Zekri and Obreza (2003) reported that when P is too low, citrus trees will exhibit limited flower development with reduced fruit set and fruit yield. Also, Steven (2002) in his study of foliar sprays to increase fruit size and yield in Californian citrus reported that phosphorus (phosphite) and potassium mixture at 7.3 L ha1 increase yield without reducing fruit size. The significant effect of P as shown in this paper on number of marketable fruits, aborted flowers and overall fruit yield of T. cucumerina may be explained by the central role played by P in energy systems of plants. Adams (1986) reported that when P level is optimum, much of energy required for plant metabolism which is stored chemically in the form of complex organic phosphates adenosine triphosphate (ATP) will be made available and released as required. Therefore, important chemical processes involved in growth will be driven steadily. The significant effect of P on the number of flowers aborted and number of rotted fruits in T. cucumerina as shown in this study was also consistent with the findings of Skinner, Cook, and Matthews (1988); and Skinner and Matthews (1989), who reported that P deficiency in grapevines inhibit the initiation and maintenance of fruit clusters and flowers within developing buds. As a result, fruit yield from P-deficient grapevines is reduced. Zekri and Obreza (2003) in their studies on macronutrient deficiencies in citrus, reported that when P is too low, leaves shed prematurely and fruit can drop before normal harvesting time. They also reported that trees will exhibit limited flower development with reduced fruit set and fruit yield. This furthermore corroborates the findings of Lauer and Blevins (1989) on soybean that the primary effect of limited P on soybean reproductive growth was to increase flower and pod abortion. The effect of phosphorus on the proximate composition of snake tomato is presented in Table 3. The fruits under 90 kg P2O5 ha1 and 120 kg P2O5 ha1 had higher ether extract and crude fibre content compared to the fruits under every other level of P. At 0 and 30 kg P2O5 ha1 there was no significant difference in ether extract composition. P levels did not significantly affect crude protein content. The crude fibre contents followed perfectly the trend observed for ether extract.
The moisture contents at 60, 90 and 120 kg P2O5 ha1 were significantly higher than the contents at 0 and 30 kg P2O5 ha1. There was no significant difference among the moisture contents at 60, 90, and 120 kg P2O5 ha1. The ash contents followed the same trend as the moisture content. The total sugar contents at 90 and 120 kg P2O5 ha1 was significantly higher than at all other phosphorus levels. Total sugar content was 87.6%, 54.3% and 39.3% higher at 90 kg P2O5 ha1 than at 0, 30 and 60 kg P2O5 ha1, respectively. The ascorbic acid contents at 90 and 120 kg P2O5 ha1 were significantly higher than at all other phosphorus levels. The amount of ascorbic acid at 60 kg P2O5 ha1 was also significantly higher than the contents at 0 and 30 kg P2O5 ha1. At 0 kg P2O5 ha1, the fruit had the least content of ascorbic acid. The oxalate content (2.4–2.6 mg 100 g1) was not significantly affected by phosphorus levels. The effect of Landraces on the proximate composition of snake-tomato fruit is presented in Table 4. The ether extract content was 48.4% higher in Landrace I compared to Landrace II. The result also showed that Landrace II was 24.6% higher in total sugar content compared to Landrace I. The crude protein, crude fibre, moisture, ash oxalate and ascorbic contents of the two variants were not significantly different. Table 5 shows the essential amino acid composition of the snake tomato as affected by phosphorus levels. Results show that all the amino acids increased with increasing P levels up to 90 kg P2O5 ha1. The result also shows that all the amino acids were present in significantly higher amounts at 90 and 120 kg P2O5 ha1 than at other P levels. It can be suggested from these results that P plays a significant role in amino acid production because the amino acid composition declined as the P level reduced. The values of the different amino acids showed that T. cucumerina is a good source of amino acids when compared with the oranges, pepper and tomato earlier reported by Adebooye (2001). The implication of this is that T. cucumerina can be a good source of essential amino acids for man and animals consumption. Amino acids are the ‘‘building blocks’’ of the body protein. Besides building cells and repairing tissue, they form antibodies to combat invading bacteria and viruses; they are part of the enzyme and hormonal system; they build nucleoproteins (RNA and DNA); they carry oxygen throughout the body and participate in muscle activity (Lehninger, 1990).
Table 3 Effect of phosphorus on the proximate composition of snake tomato fruits across landraces P Levels kg P2O5 ha1
Ether extract
Crude protein
Crude fibre
Moisture
Ash
Total sugar
1
0.64c 0.66c 0.90b 1.22a 1.19a
Oxalate acid 1
g 100 g 0 30 60 90 120
Ascorbic mg 100 g
1.84a 1.92a 1.85a 2.39a 2.02a
1.34c 1.47c 1.63b 1.93a 1.90a
88.1b 87.9b 89.5a 90.5a 89.7a
0.64b 0.64b 0.80a 0.90a 0.89a
0.55c 0.59c 0.70b 0.81a 0.78a
15.3d 18.6c 20.6b 28.7a 27.7a
2.4a 2.6a 2.5a 2.4a 2.4a
Means with the same letter are not significantly different at 5% level of probability according to DuncanÕs Multiple range tests. Values are means of 2002 and 2003 studies.
O.C. Adebooye, F.M. Oloyede / Food Chemistry 100 (2007) 1259–1264
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Table 4 The effect of Landraces on the proximate composition of snake tomato fruits across phosphorus levels Ether extract
Crude protein
Crude fibre
Moisture
Ash
Total sugar
Ascorbic acid
1
mg 100 g
g 100 g Landrace 1 Landrace 2 LSD 5%
Oxalate
1
0.90 0.62 0.24
2.06 1.94 NS
1.63 1.53 NS
88.8 89.0 NS
0.76 0.78 NS
0.61 0.76 0.10
20.3 19.2 NS
2.80 2.50 NS
Means with the same letter are not significantly different at 5% level of probability NS = not significant at 5% level of probability. Values are means of 2002 and 2003 studies. Table 5 Effect of P levels on Amino acid composition of T. cucumerina across phosphorus levels Amino acid
0
30
60
90
120
14.8b 1.45b 2.51b 6.05b 1.42b 0.56b 3.05b
17.1c 1.91c 3.55c 7.60c 1.76c 0.75c 4.50c
19.9d 2.85d 4.80d 8.65d 2.15d 0.96d 6.90d
18.9d 2.84d 4.91d 9.05d 2.12d 0.86d 6.55d
kg P2O5 ha1 Arginine Histidine Isoleucine Leucine Methionine Tryptophan Valine
12.2a 1.10a 2.30a 5.68a 0.94a 0.45a 2.05a
All values are expressed on g 16 g1 N. All values are means of 2002 and 2003 studies. In each row, means followed by different alphabets are significantly different at 5% level of probability.
4. Conclusion
References
The results of this study showed that the protein, fat, ascorbic acid and amino acid composition of T. cucumerina are high enough and compare favourably with the composition of other known important edible fruits. The high quantity of its paste, its palatability and aroma are additional good qualities of T. cucumerina. The low and safe oxalate content also suggested that the availability of Ca and Mg in T. cucumerina for man and animal use would not be threatened. Further studies on the improvement of this novel plant are a worthwhile effort to broaden the food base and widen the income base. It is also important to conduct further studies into the relationship between P supply and amino acid synthesis in this plant because as P level increased, the essential amino acids contents increased up to 90 kg P2O5 ha1. Improving this plant will also help in its conservation and prevent it from the threat of extinction. It is globally acknowledged today that many plants are facing threat because, they have for long been neglected by research and development process and T. cucumerina falls into this category.
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Acknowledgements The Central Analytical Laboratory and the Animal Science Analytical Laboratory, Obafemi Awolowo University, Ile-Ife, Nigeria carried out the proximate and mineral analyses. The United Nations University/Institute for Natural Resources in Africa (UNU/INRA) funded this research through a project on nutritional studies of underexploited African vegetables (INRA 2004/0002).
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