Published on International Journal of Agriculture & Agribusiness
Publication Date: June 10, 2019
B. A. Lawal
Ladoke Akintola University of Technology (LAUTECH), Ogbomoso, PMB 4000
Ogbomoso, Oyo State, Nigeria
Identifying nutritional quality of a potential food crop species is essential; Winged bean is a unique leguminous crop in that most of its parts are edible and rich in protein. Hence the study carried out the proximate analysis of studied winged bean accessions. Field experiment was carried out at the Teaching and Research Farm, Ladoke Akintola University of Technology, Ogbomoso in 2015. Seeds of thirty eight (38) accessions of winged bean were obtained from the International Institute of Tropical Agriculture, Ibadan, Nigeria and were sown in three 4 m row plots spaced at 1 m × 1 m and replicated three times. The trial was laid out in a Randomized Complete Block Design (RCBD). Data were collected on number of germinated seeds (NGS) at 2, 3 and 4 weeks after sowing (WAS), Normalised Difference Vegetation Index (NDVI) values was recorded at 5, 6, 7, 8 and 9 WAS using the Greenseeker hand held optical sensor unit while seeds were analyzed for Moisture, Ash, Crude protein (CP), Crude fibre (CF) and Carbohydrate (CHO) contents using standard procedures. Data collected were subjected to analysis of variance and means were compared using the Least Significant Difference at 5% probability level. Results revealed that winged bean accessions influenced the NDVI values significantly at 5 and 6 WAS. Proximate analyses of the accessions were not significantly different (P> 0.05). Proximate content value ranges are: moisture (9.56 – 10.09 %), ash (3.73 – 5.84%), crude protein (24.48 – 24.71%), crude fibre (2.68 – 2.89%) and carbohydrate (56.06 – 58.06 %). The highest correlation coefficient between NDVI readings and proximate content was between NDVI at 6 WAS and seed ash content (r = 0.24; P <0.01) while NDVI at 5 WAS was negatively correlated (P>0.05) with seed carbohydrate (r = -0.04) whereas NDVI at 6 WAS was negatively correlated with crude protein and carbohydrate content (r = -0.10, and -0.23, respectively)of winged bean seeds. This study reveals that there is sufficient variation for various nutritional compositions evaluated in this study. Accessions TPT 12, TPT 43, TPT 17, TPT 2A and TPT 1A can be further studied for crude protein and crude fibre contents while TPT 48 and TPT 6-A have promising potentials for carbohydrate contents. Hence, location studies within the studied agro-ecological zone will assist in validating the nutrient contents of the evaluated accessions of winged bean.
Keywords: Accession; Proximate; Seed; NDVI; Winged bean.
Winged bean is a tropical crop that is recognized as one of the under-exploited legumes (Klu, 2000). It is unique among leguminous crops in that several parts of the plant (leaves, pods, seeds and tubers) are edible and rich in protein (Garcia and Palmer, 1980). Mahto and Dua, (2009) have recommended it as a potential food source in the tropics. In recent times, much attention has been drawn to the dependence of the world’s population on very few species of crops for food. This has resulted in the over tasking of the available conventional protein and energy sources to the extent that their supplies have been disproportionately lower, relative to the demand of the population (FAO, 2015).All food legumes are valuable sources of proteins, vitamins and minerals and occupy an important place in human nutrition. Assessment of genetic variations and relationships among these leguminous crops may therefore play a significant role in breeding programs to improve grain yield, oil and protein content.
Interest in winged bean is rapidly increasing as a high protein multipurpose crop. For instance, presently, winged bean is one of the most important vegetables in south India and Thailand. Breeding of winged bean as a grain legume requires the development of improved genotypes with the highest nutritional contents and lowest anti-nutritional factors. The nitrogen fixing capability of the crop has helped secure its role as a cover crop in intercrop systems as well as enriching the soil (Anugroho et al. 2010; Banerjee, 2008). It is adaptable to a wide range of environmental conditions and presently, there are hundreds of accessions, many of which were developed in China (Klu, 2000). What is known about winged bean today is roughly correspondent to what was known about the soybean 60 years ago. In Nigeria, there is no vivid record about the existence and cultivation of winged bean although there exist theories that it is cultivated and consumed in the southern part of the country.
Winged bean seeds had been reported to contain 14% of moisture, 33% of protein, 16% of fat and 5% of crude fibre (Pospisil et al., 1978). Furthermore, the proximate analysis conducted by the National Academy of Science (1975) reported that the crop contains 6.7-24.6% moisture, 23.8-37.4% protein, 15-20.4% fat, 3.6-4% ash, 28-31.6% carbohydrates and crude fibre of 5-12.5%.Claydon (1975) reported 8.7% moisture, 36.6% protein, 15.3% fat, 3.8% ash, 35.6% carbohydrates and 3.7% crude fibre. Recently, the proximate composition of winged bean leaves was reported by (Alalade et al.,2016), as75.29% moisture content, 24.71% dry matter, 26.29% crude protein, 4.10% ether extract, 10.04% crude fiber and 5.8% ash content. Amoo et al. (2006) however reported the proximate content of winged bean seeds as 9.22% Moisture content, 4.91% ash content, 17.51% fat content, 12.23% crude fibre, 33.83% crude protein and 22.30% carbohydrate. These reports however did not indicate the accession for which these values were obtained from; also, inter accession variations have been reported to exist among the proximate compositions of different accessions of winged bean.
New remote sensing tools that are based on irradiation are presently being used to estimate green biomass of various crops on the field (Liebisch, 2015).The use of this technology has been reported in rice (Jingfeng et al. 2013), yam (Kohtaro, 2018)), peanut (Zerbato et al, 2016) and pea (Klimek-Kopyra et al. 2018) among other crops. The GreenSeeker(R) handheld optical device (NTECH industries, 2007) is a spectro-radiometer that is been used for phenotyping in crop screening (Lu et al. 2012).It measures the normalized difference vegetation index (NDVI) which is based on specific wavelengths measurement that can be used for instance, to calculate the vegetation indices that can be used to estimate production potentials of agricultural crops, among numerous other applications. The Greenseeker measures NDVI on a numerical indicator and this measurements has been described to be highly correlated with grain yield in maize and other crops (Lu et al. 2012 and Cabrera et al., 2011). NDVI is calculated with the estimation of reflectance recorded in the visible region and near infrared region of the spectrum (Lu et al. 2012). It is useful in monitoring the vigour of green biomass and has been found to be comparable to the leaf area of plant (Lu et al. 2012, 2011). Jensen (2009) reported that by using vegetation indices, it is possible to determine agronomic parameters, such as leaf area index, percentage of green cover, chlorophyll content and green biomass among others. Crop germplasm that accrue abundant biomass as revealed by high NDVI values at the seedling stage of the crop are likely to produce high yields at harvest. Hence, screening of crop accessions with NDVI values at early stage of growth is important to reduce loss of resources. There are wide variations among the reported proximate composition of winged bean accessions and this may be due to several factors. In addition, there is a large number of winged bean accessions and efforts to evaluate them all may be expensive and time consuming. Hence there is a need to explore methods of screening large number of materials in limited time; therefore, this study evaluated the nutritional qualities of winged bean accessions and correlated the NDVI values to nutritional composition of Winged bean.
2. MATERIALS AND METHODS
Field experiment was carried out at Teaching and Research Farm, Ladoke Akintola University of Technology, Ogbomoso, Oyo State, Nigeria. The site (latitude 8o 7IN and longitude 4o 14IE) is characterized with two seasons which include the wet season spanning March to October and the dry season which starts in November and ends in February. The climatic condition of Ogbomoso is mostly influenced by the northeast trade wind and the South-west wind.
Seed of thirty eight (38) winged bean accessions (Table 1) were obtained from the Genetic Resources Centre of the International Institute of Tropical Agriculture (IITA), Ibadan. The seeds were scarified mechanically by cutting through the seed coat opposite the micropyle with a scalpel blade to enhance water imbibition, break internal dormancy and hasten germination. Each accession was sown in three 4 m row plots spaced at 1 m within and between rows and laid out in a randomized complete block design (RCBD) and replicated three times. Three seeds were sown per hole and later thinned to two plants per stand at 4 weeks after sowing (WAS). Staking was done when the plants reach the twining stage for plants to access adequate sunlight. Each stand was supported with 3 m long dried bamboo poles and the plants were trained to twine around the bamboo stake.
Number of Germinated Seeds was obtained by counting the number of seeds that germinated per plot at 2, 3 and 4 WAS. GreenSeeker(R) handheld optical sensor unit (NTECH industries, 2007) installed with red sensor, red waveband centered at 650 ± 10 nm, and near infra-red (NIR) band centered at 770 ± 15 nm, was used to measure NDVI value in each plot. The device was operated at about 60 cm above the crop starting from the first through the third row and recorded per treatment plot. Readings were taken in each plot at 5, 6, 7, 8 and 9 WAS.
Proximate contents of the seeds of each of the 38Winged bean accessions harvested was determined in the laboratory following the standard procedure of AOAC (2002). The analyzed proximate components are crude protein, ash content, moisture content and crude fibre content.
Data collected were subjected to analysis of variance (ANOVA) and treatment means were separated using the Least Significant Difference (LSD) at 5% significant level. The ANOVA was performed with SAS 9.0 software (SAS Institute, 2011). Correlation between variables was computed using PROC CORR in SAS (SAS Institute, 2011).
Accession of winged bean influenced (P< 0.05) seed germination and NDVI readings significantly (Table 2) while it had no significant effect (P≥0.05) on all the proximate contents of winged bean (Table 3). Number of germinated seeds mean at 2, 3 and 4 weeks after sowing (WAS)of the top and bottom ten accessions are shown in Table 4. Accessions TPT 53 had the highest mean germinated seeds (25.00) while TPT 7 had the lowest number of germinated seeds (16.00) at 2 WAS while at 3 and 4 WAS, TPT 32had the highest germinated seeds (25.33) and the least was obtained from TPT 7 (18.00 and 18.33 respectively). Normalised difference vegetation index (NDVI) of the top and bottom 10 winged bean accessions are presented in Table 5. TPT 2, 32 and 53 had the highest NDVI values (0.27) while TPT 7 and 126 had the lowest value (0.21) at 5 WAS. Across the weeks, TPT 2 maintained the lead while TPT 7 also followed with the least NDVI value. The mean proximate content for the top and bottom 10 winged bean accessions is presented in Table 6. Moisture content of winged bean accessions ranged from 9.56 to 10.09% with TPT 53 having the highest content (10.09%) and TPT 126 having the lowest (9.56%). Ash content varied between 3.73% and 5.84% with TPT 6 having the highest content. Crude protein varied between 24.48% and 24.71 % with TPT 4–A recording the highest content. Crude fibre content was between 2.68% and 2.89% with TPT 1A having the highest content. Carbohydrate content ranged from 56.06% to 58.06% with TPT 22 having the highest mean value. The Pearson correlation between every pair of measured NDVI values and proximate contents of the evaluated 38 winged bean accessions is presented in Table 7. There was positive and significant (P<0.01) correlation between every pair of all the NDVI values. Moisture content had no significant correlation with the NDVI values (P≥0.05) across the weeks. Also, ash and carbohydrate contents had no significant correlation with the NDVI values except at 9 WAS (r = 0.24; P<0.01 and r = -0.23; P<0.05respectively). Crude protein was equally negatively but significant correlated with NDVI at 5, 6 and 7 WAS (r = -0.26; P<0.01, r = -0.58; P<0.001 and r = – 0.25; P<0.05, respectively). Crude fibre was significantly but negatively correlated with NDVI at 5 and 6 WAS (r = -0.33; P<0.05 and r = – 0.49; P<0.01 respectively). 4. DISCUSSION There exist variations in germination among the tested accessions. The occurrence of highly significant influence of accession on Normalised Difference Vegetation Index (NDVI) value indicates that NDVI as a technique can be used to predict performance and quality of these set of accessions tried and that there is genetic variability among them. This is in agreement with the report of Mohanty et al. (2013) who reported that accessions exhibit variations for different traits within a population. In this regards, it was also observed that accessions that performed well for vegetative traits showed significant performance for Normalised difference vegetation index values at early stage of growth, thus, NDVI values at early growth stage can be gainfully used to identify promising accessions. However, the small range in the variation of the nutrient contents of winged bean seeds may point to a close ancestral descent between the evaluated accessions in this study. It could also be as a result of influence of soil microbial activities, the soil type as well as problems of adaptation because winged bean cultivation has not been previously reported in the experimental region prior to the conduct of this study. The aforementioned factors can significantly influence performance and nutrient contents as reported by Jiménez et al. (2012); Hagerman et al. (1998) and Dahiya et al. (1977). Singh et al. (2013) reported that high environmental influence and agronomic practices influenced the crude protein content of pigeon pea to a considerable extent and this could also elucidate the variation observed in the crude protein and other nutrients in this research. Tripathi et al. (1975) reported that the protein content of pigeon pea of late maturing cultivars was greater than the early maturing cultivars and maturity of the crop has an important role in accumulation of protein content during seed development. Furthermore, the carbohydrate content of seeds of all the accessions in this study was considerably high, which was almost double the range of 28% to 31.6% reported by NAS (1979) as well as the 22.30% reported by Amoo et al. (2006) in Nigeria. The use of remote sensing techniques can be gainfully used to predict the nutrient contents of crops (Lu et al., 2012; Cabrera et al., 2011). 5. CONCLUSION Winged bean is one of the leguminous crop that has promising potentials but it however remain an underutilized crop. The state of knowledge concerning the crop still requires further research and testing to access the crop’s future hence the need to assess it nutritional status and agronomic performance. This study reveals that there is sufficient variation for various nutritional compositions among the evaluated accessions and that some of the compositions are highly correlated to each other. Accessions TPT 12, TPT 43, TPT 17, TPT 2A and TPT 1A can be further studied for crude protein and crude fibre contents while TPT 48 and TPT 6-A have promising potentials for fat and carbohydrate contents. In conclusion, further studies across different locations in the studied agro-ecological zone will assist in validating the nutrient contents of the crop of the evaluated accessions of winged bean.