Yam Tubers Research Articles

Transciptome Analysis Molecular Mechanism of Starch Synthesis During Tuber Development in Chinese Yam (Dioscorea opposita)

Yam (Dioscorea opposita) is a kind of vegetables with important nutritional, medicinal and economic value. To reveal the relationship between starch synthesis and gene expression in yam tubers at gene transcription level, transcriptome profiling was conducted by RNA-Seq in Bikeqi yam (Dioscorea opposita Thunb.) tubers at five key developmental stages (105, 120, 135, 150, and 165 days after sowing, DAS). Based on transcriptome sequencing data, a total of 45,867 unigenes were obtained. The results showed that 135 days after sowing are the key period of starch accumulation. During yam tuber development, 1,941 candidate differentially expressed genes (DEGs) were successfully classified into three GO categories, respectively, and there were 292, 267 and 478 unigenes in cellular component, molecular function and biological process. There were 767, 90 and 73 DEGs enriched in metabolic, plant hormone signal transduction and Plant-pathogen interaction pathway by Kyoto Encyclopedia of Genes and Genomes (KEGG), individually. Especially 72 DEGs were enriched in starch and sucrose metabolism pathway. In this pathway, the metabolic process was mainly positive regulated by genes encoding sucrose synthase, glucose-1-phosphate adenylyltransferase, alpha-trehalase, and so on. There was negative regulated by genes encoding beta-glucosidase. 10 DEGs involved in starch synthesis were selected to prove the accuracy of the RNA-Seq data by qPCR, 85% (34/40) of the results were consistent. The results lay a theoretical foundation be used for further understanding the starch synthesis mechanism of yam tubers development and accelerating breeding progress.

The effects of calcium fertilizer on anthracnose and Rhizopus tuber rot of yam

Yam (Dioscorea spp) production is beset in the field and in storage by major fungal pathogens, namely Colletotrichum gloeosporioides that causes anthracnose in the field, and Rhizopus stolonifer that causes tuber rot in storage. Alternative control measures are imperative as conventional control of these pathogens is either ineffective or detrimental. This study investigated the effects of calcium fertilizer on the incidence and severity of anthracnose and Rhizopus rot of yam. Calcium nitrate fertilizer was applied to soils naturally infected with C. gloeosporioides, at the rates of 0, 3, and 4kg ha-1. D. rotundata variety Efuru was planted. The treatments were arranged in a randomized complete block design with three replicates. Anthracnose disease rating relied on natural endemic infection in the field, while inoculation of harvested yam tubers was carried out using R. stolonifer. There was no significant effect of calcium amendment of the soil on anthracnose severity in D. rotundata or on the agronomic parameters. D. rotundata tubers treated with 3 and 4kg ha-1 calcium soil amendments had reduced infection by R. stolonifer in storage compared to the control treatments. The study concluded that calcium applied to the soil had reduced storage losses by R. stolonifer in D. rotundata but had no influence on anthracnose severity in the field. Therefore, 3kg ha-1 of calcium nitrate applied to the soil can be used to improve D. rotundata tuber resistance to R. stolonifer, and is recommended for high-quality tuber storage.

Enhanced Carbohydrate Metabolism and Salinity Tolerance of Tobacco Plants Overexpressing a Vacuolar H+-ATPase Subunit B2 (DoVHAb2) Gene from Yam (Dioscorea opposita Thunb.)

ATP synthase plays a vital role in plant growth and stress tolerance, functional studies of DoVHAb2 in yam tuber starch metabolism and salinity tolerance have so far not been reported. Full-length cloning and analysis of DoVHAb2 were conducted to ascertain its function. The gDNAs were cloned and analyzed. Quantitative real-time polymerase chain reaction (qRT-PCR) was probed in yam tuber developmental stage and different organs of DoVHAb2. Transient expression vector was constructed and injected into tobacco leaves to observe the subcellular localization of genes. Overexpressed fusion vector of gene was constructed and transformed into tobacco by Agrobacterium-mediated method to identify the function of DoVHAb2 gene. In the results, the full-length of DoVHAb2 was 1926 bp, encoding 488 amino acids, and it was divided into 14 exons and 15 introns, its highest expression was found in tubers than in stems and leaves in yam, the yam DoVHAb2 protein was localized to cytoplasm. The starch content, ADP glucose pyrophosphorylase, starch synthase and ATPase activity were significantly higher in transgenic tobacco plants than in the wild-type. The transgenic plants also had higher leaf differentiation rate, soluble protein content, superoxide dismutase and peroxidase activities, and lower malondialdehyde content than the wild type under NaCl stress. In conclusion, the results indicated that overexpression of DoVHAb2 enhanced starch metabolism and conferred salinity tolerance.

Phytochemical and Antioxidant Analysis of Fermented ‘Dayak’ Wild Yam (Dioscorea hispida Dennst), Purple Yam (Dioscorea alata) and Air Potato (Dioscorea bulbifera L.) Tuber Flour

Tubers of Dioscorea spp. contain many compounds that have physiological activity that can act as antioxidants and are proven to have various health uses. Antioxidant compounds have a very important role in the health of the human body. Various scientific evidence show that antioxidant compounds reduce the risk of various chronic diseases such as cancer and coronary heart disease.The study aimed to determine the phytochemical content and antioxidant activity of fermented Dayak wild yam (Dioscorea hispida Dennts), Purple Yam (Dioscorea alata var. Purpurea) and Air Potato (Dioscorea bulbifera) tubers flour was carried out. Phytochemical testing was carried out by the Harborne method (1987) and antioxidant activity using DPPH (1,1-diphenyl-2-picrylhydrazyl) method. The data obtained were analyzed descriptively from the average value of 3 replications for each parameter. Phytochemical analysis results showed the presence of alkaloids, tannins, triterpenoids and carbohydrates. While the results of the antioxidant activity testing showed that the IC50 value of fermented Dayak wild yam flour (WYF) was 227.43 ppm, air potato tuber flour (APF) was 15.77 ppm and purple yam tuber flour (PYF) was 7.70 ppm. Thus it can be concluded that all three tubers belonging to Dioscorea spp. all of them contain antioxidants with the order of the strength of antioxidant activity sequentially from the strongest to the weakest are PYF, APF and WYF.

Amylase-Producing Fungi and Bacteria Associated with Some Food Processing Wastes

Amylases are enzymes that catalyze the hydrolysis of glycosidic bonds present in starch to release simple sugars. They are one of the most important enzymes in numerous commercial processes. In this investigation, fungal and bacterial strains from the following agro-industrial wastes were isolated and screened for amylolytic ability: soil from oil palm plantation, shea seed, date fruit, coconut meat, cassava effluent, cassava peel, cassava tubers, yam and potato tubers, starch medium, parboiled water from noodles and rice. The results revealed the presence of Geotrichum, Aspergillus, Penicillium, Trichoderma, Rhizopus and Fusarium spp. Five major genera of bacterial species namely Corynebacterium, Pseudomonas, Lactobacillus, Micrococcus and Bacillus were isolated and screened for amylase activity. Cassava soil had the highest heterotrophic bacterial count of 5.7 x105cfu/g and coconut meat waste had the lowest heterotrophic bacterial count of 1.3 x105cfu/g. All isolated microorganisms had the amylolytic ability. The fungal isolates had higher amylase activity when compared with the bacterial isolates. This investigation reveals organisms with high amylase activity.

INVESTIGATION OF PLANT-PARASITIC NEMATODES OF YAM IN SELECTED YAM FARMS IN TWO LOCAL GOVERNMENT AREAS OF RIVERS STATE

Investigation of plant-parasitic nematodes of yam in selected yam farms in two Local Government Areas of Rivers State was conducted. A total of 22 yam farms were selected and assessed, 12 from Emohua and 10 from Etche Local Governemnet Areas (LGA). Two tubers of yam ready to be harvested were randomly selected and the soil around it were collected, bagged individually and transported to the laboratory for bioassay. Sieve plate nematode extraction technique was used for extraction of nematodes from the tubers and soil. The purpose of the study was to identify the plant parasitic nematodes that affect yam in the selected zone and likely to predict if nematode was a predisposing agent to yam rot in the study area. The results showed that in Emohua LGA, Meloidogtne spp. with mean population of 90.407±0.543 were the most prevalent species in the soil samples followed by Heterodera spp. with 38.622±0.891 and Pratylenchus spp. with 26.322±0.962 while in the roots and yam tuber Meloidogyne spp. had the most prevalent species with mean population of 69.510±0.907, followed by Scutellonema spp. with 15.651±2.201 and then Ditylenchus spp. with 13.7651±2.644. Also, in Etche LGA, Meloidogyne spp., Tylenchulus spp. and Rotylenchulus spp. had the most prevalent species in the soil with mean populations of 24.920±0.479, 22.426±1.093 and 20.202±0.828 respectively. In the roots and yam tubers, Scutellonema spp., Meloidogyne spp. and Heterodera spp. in that order had the most prevalent species with mean populations of 17.814±0.253, 13.240±0.286 and 10.619±0.401 respectively. Data analysis showed that plant-parasitic nematodes recovered from the soil and roots/yam tuber were statistically significant at P<0.05. These showed that the presence of these plant-parasitic nematodes in the study area suggests that they are important pests of yams even though their presence is not noticed by farmers. They could be attributed to poor yield in yams in the study areas.

Storage of Fresh Yam (Dioscorea alata L.) under Controlled Conditions

Freshly harvested "Florido" yam tubers (a highly desirable variety of the species D. alata) were subjected to a temperature of around 32° C. (90° F.) and a relative humidity of 90 percent. Wounded tissues were suberized in about 4 days. This curing may be accomplished either in controlled environmental rooms or under tropical prevailing ambient conditions. The formation of the cork tissue during suberization protects tubers from infection by microorganisms if stored under reduced temperatures. Cured and uncured tubers were stored in a properly ventilated Forma Scientific room at 16° C. ± 1° (59° to 62.9° F.), and a relative humidity of 70 percent. Uncured samples suffered high losses due to physiological breakdown as well as markedly higher weight losses than similarly handled cured ones which showed no signs of internal decay during the storage period. Cured tubers kept under conditions noted above, at temperatures below those prevailing in tropical areas, had the dormant period lengthened by 4 additional months. High-quality tubers can be provided by this means for the fresh market and for processing during the off-season. Although the yam tubers hardened slightly during storage, weight losses were kept at a fairly low level and the palatability of the tubers remained very high, as determined by sensory evaluation.

Physico-chemical characterization of fresh tuber of water yam (Dioscorea alata) germplasm

Information of the physical and chemical characteristics in water yam tuber (Dioscorea alata) is needed to complete the database of germplasm, support the breeding activities and utilization for both food and industry purposes. This study was conducted at the Food Chemistry Laboratory of Iletri to observe the physical and chemical characteristics of the water yam fresh tuber derived from 22 Iletri’s germplasm accessions. The fleshed of water yam color were varied, namely white, yellow, mixture of white and purple, white and yellow, yellow and purple. The trial was arranged using a completely randomized design with three replications. The moisture content ranged from 56.08-80.03%, dry matter 18.82-43.02%, ash 2.56-4.97% dw, starch 61.81-75.87% dw, amylose 28.40-43.15% dw, and reducing sugar 0.27-1.49% dw. The fiber content varied widely from 4.33% to 13.99% dw. The water yam also had a wide range of texture, ranging from soft to hard with a hardness level of 6.78-57.78 N. Based on the starch and fiber contents of the fresh tuber, MLGAR 0071, MLGAR 0183, MLGAR 0003 and MLGAR 0006 accessions were potential to be used as parent materials in breeding program to obtain superior varieties of water yam with high starch and fiber contents.

Disease Resistance Attributes Conferred by Mineral Fertilizer in Dioscorea Species

This study investigated proximate content, phenol as well as mineral content effects of an 8-mineral content fertilizer, namely Bounty, on resistance attributes in the nourished tubers of four Dioscorea species varieties, compared to those sourced from farmers plots within Ogun state, which had been nourished with the natural replenishment of at least 2 to 4 years fallow. The experiment was a 4 by 3 factorial arranged in RCBD (randomized complete block design) with 12 treatment combinations and 3 replicates. Main factor was variety that is Dioscorea rotundata varieties Oniyere (from South West Nigeria) and Abuja (from middle belt Benue/Plateau of Nigeria), D. cayenensis var. Igangan/Alo (from South West Nigeria) and Dioscorea alata var. Agbodo (from South West Nigeria).  Treatments were Bounty fertilizer at the rates 0.6 ml l–1 as well as 1.2 ml l–1 and farmers’ plot (FPT, with no fertilizer). The Bounty-fertilized tubers were harvested from the Teaching and Research Farms of the Directorate of University Farms, Federal University of Agriculture, Abeokuta, Ogun State, Nigeria at 6 months after planting (6 MAP). Farmers plot tubers were also harvested at 6 MAP. Analysis was done after processing of the tubers. Among the proximate components, moisture, dry matter, ash, crude fibre and carbohydrate of mean values 14.05%, 85.96%, 2.77% dm, 8.55% dm and 82.71% dm were comparable/similar in the four varieties. However, Oniyere (white guinea yam – South West Nigeria) was lower in fat and higher in crude protein than the other three varieties. Abuja, Igangan and Agbodo were comparable/similar in fat content, but Igangan (yellow guinea yam) had lower crude protein than Agbodo (water yam) whereas Abuja (white guinea yam – Middle Belt Nigeria) and Agbodo were similar/comparable in crude protein. Bounty-fertilized tubers at the 2 concentrations were lower in ash (mean 2.63% dm) and carbohydrate (80.98% dm) than Farmers plot tubers (FPT), (3.06 and 86.17% dm respectively). But they were higher in phenol and calcium, with means of 189.82 and 22.16 mg/100 g dm respectively than farmers plot tubers (means of 120.77 and 16.89 mg/100 g dm). Both calcium and phenol have been reported in increased resistance to disease in plants including Dioscorea spp. in literature. Correlation tests in this study indicated significance between calcium (from the fertilizer) and tuber phenol (r = 0.4523). Calcium correlated significantly also with crude fibre (r = 0.9325) and crude fibre with phenol (r = 0.7110). Calcium correlated significantly also with tuber potassium which was not supplied from the fertilizer (r = 0.6662), indicating that increased uptake of calcium would enhance uptake of potassium. Consequently potassium supported by Nitrogen (the highest component, 15% w/w in Bounty Fertilizer) would have positive effect on tuber yield, as the highest proportion (91% to 94%) of total N and K are reported to be accumulated in yam tubers at harvest. These results underscore effects of mineral nutrition (such as Bounty) for increased disease resistance and increased yield, over natural replenishment after fallow which the smallholder farmer depends on solely in Nigerian traditional yam farming system.

Regulatory mechanism of GA3 on tuber growth by DELLA-dependent pathway in yam (Dioscorea opposita).

Endogenous and exogenous GA3 responses to DoEXP and DoXTH depend on the DoGA20ox1, DoGA3ox1, DoGA2ox3, DoGA2ox4, DoGID1a, and DoDELLA1 to regulate yam tuber growth. Yam tuber undergoes significant alteration in morphogenesis and functions during growth, and gibberellins (GA) are considered potentially important regulators of tuber growth. However, it is little known about the regulation of GA metabolism and GA signaling components genes in tuber growth of yam. In this study, the cloning and expressions of GA3 level, GA metabolism and signaling genes, and cell wall genes in tuber growth in response to GA3 and GA biosynthesis inhibitor paclobutrazol (PP333) treatments were studied. The contents of GA3 accumulated at the tuber growth, with the highest levels in the early expansion stage. DoGA20ox1, DoGA3ox1, and four DoGA2ox genes were significantly abundant in the early expansion stage of tuber and gradually declined along with tuber growth. Three DoGID1 and three DoDELLA genes were showed different expression patterns in the early expansion stage of tuber and gradually declined along with tuber growth. Five DoEXP and three DoXTH genes expression levels were higher in the early expansion stage than in other stages. Exogenous GA3 increased endogenous GA3 levels, whereas the expression levels of DoGA20ox1, DoGA3ox1, DoGID1a, and DoDELLA1 were down-regulated in the early expansion stage of tuber by GA3 treatment, DoGA2ox3 and DoGA2ox4 were up-regulated. PP333 application exhibited opposite consequences. Thus, a mechanism of GA3 regulating yam tuber growth by DELLA-dependent pathway is established.

Ecological and Edaphic Drivers of Yam Production in West Africa

Yam is an important food and cash crop in West Africa (the yam belt) whose production is traditionally nonsedentary due to its substantial nutrient demand. Population growth, urbanization, and existing soil degradation have made nonsedentary farming virtually impossible. Despite the numerous research invested in yam production within and outside the yam belt, some gaps remain to be filled owing to changing climate events and global developments. Alarmingly, the yam belt is facing sharp yield declines despite increasing production areas. The key edaphic and ecological drivers of yam production in the global yam belt were reviewed. The implications for yam production were discussed along with prospects for future research, sustainable production, and soil management. The main findings are that (1) agroecological zone, postplanting cultural practices, and climate change and variability ecological drivers, while (2) tillage, soil type, texture, and fertility were the edaphic factors. The most critical among the drivers, principally, soil fertility, entails the biological and chemical through which nutrients are released lude, and physical soil fertility which enhances low bulk density, porosity, and water retention for free yam tuber expansion. Soil fertility was the most cited driver, which explains why yam is often the first crop in the cropland cultivation cycle in the yam belt. Data show that yam yields decline with time under native fertility and mineral fertilizer application due to the voracious nutrient extraction by tubers. Conversely, yields increase chronologically under organic fertilizer application due to the additive effects of the latter on soil properties. Thus, a yam fertilizer program to develop specific yam fertilizer formulations and the adoption of the Terra Preta Model are proposed to sustain future yam production.

PHYSICOCHEMICAL PROPERTIES OF FLOUR AND STARCH OF PURPLE WATER YAM (Dioscorea alata) TUBER AND THE DIFFERENCE ON SENSORY ACCEPTANCE OF THE COOKIES PRODUCED

Purple water yam tubers (PWYTs) or Dioscorea alata are edible tubers containing bioactive compounds that are beneficial to human health. Its high carbohydrate content can be used to make flour or starch to increase its shelf life and food diversification. However, this food is unpopular among several communities in Indonesia, particularly for the juveniles due to limited processing knowledge. Therefore, this study aims to characterize the physicochemical properties of purple water yam flour (PWYTF) and starch (PWYTS) in order to assess consumers' acceptability toward gluten-free cookies. The PWYTF was prepared by drying peeled tubers, which was subsequently grounded. Meanwhile, the PWYTS was prepared by homogenizing the peeled tubers with water, the sediment from supernatant was dried. The chemical properties, such as moisture, ash, fiber, protein, and lipid, were determined using the Indonesian national standard procedures for flour. The physical properties, namely pH, bulk density (BD), water/oil absorption capacity (W/OAC), water/oil binding capacity (W/OBC), swelling power (SP) and solubility (Sol) were evaluated. The PWYTF and the PWYTS were used to make gluten-free cookies, with their physical properties and consumer's acceptability evaluated using semi-trained panelists. Yields of both the PWYTF and the PWYTS were 36.10% and 26.63%, respectively. The chemical compositions of the PWYTF and the PWYTS were significantly different (p0.05) for carbohydrate (80.34 and 80.78 %), crude protein (0.78 and 0.81%), and crude fiber (2.0 and 1.9%) except for the ash content (2.6 and 0.5%), lipid (0.3 and 0.1%), and moisture (13.77 and 15.70%). Furthermore, their physical properties were also significantly different (p0.05) for pH (6.62 and 5.84), BD (0.46 and 0.68 g/mL), WAC (2.07 and 0.46 g/g), WBC (1.07 and 0.49 g/g), SP, and Sol except OAC (1.63 and 1.49 g/g) and OBC (0.63 and 0.49 g/g). The cookies made from the PWYTS were appreciated with the highest hardness and rated from panelists. Therefore, the PWYTS can be used in place of a commercial wheat flour to make cookies..

Morphological Characteristics of Scutellonema bradys Populations Responsible for Yam Dry Rot in Côte d’Ivoire

The great diversity of agroecological factors that cover the yam production area in Côte d’Ivoire can be a source of morphological variability within Scutellonema bradys species, responsible for yam dry rot. This study aims at identifying the morphological group(s) of S. bradys which infect(s) yam Dioscorea cayenensis-rotundata. Two hundred ten yam tubers for sale in food markets in the Autonomous District of Abidjan were sampled from traders. After extraction and identification, a morphological characterization was carried out on S. bradys populations using morphological descriptors. Yam tubers sampled from food markets came from three agroecological zones namely dry tropical savannah, semi-deciduous dense forest and transitional forest areas. Morphometric variables and ratios used individually did not help identify morphological groups. Principal component analysis, however, performed with the most discriminating variables and ratios revealed three morphological groups named "large", "medium" and "small" in males and females and confirmed by the agglomerative hierarchical clustering. Each group consisted of a rate greater than 48% of individuals from a given agroecological zone. Three morphological groups of S. bradys are associated with yam dry rot in Côte d’Ivoire. Pathogenic and molecular characterization of the morphological groups would be necessary with a view to researching control methods.

The quality improvement of yam flour (Dioscorea alata) through the fermentation process

Yam (Discore alata) is a local tuber used as a substitute for wheat flour and a source of non-rice carbohydrates. The processing into flour expands the diversification of yam’s product. However, the flour produced does not resemble wheat flour, so the processing needs to be modified. This study compared several properties of modified yam flour with four treatments. The four treatments were fermentation for 12 hours with Bi-Mocaf starter, fermentation for 18 hours with tape yeast, fermentation for 72 hours with pure water and without fermentation treatment. This study found: yam flour had an average moisture and ash content of 19% and 9.00%. The fermentation with tape yeast produced the highest yield (20.40%). The highest amylose content (7.23%), protein (4.25%), viscosity (3.65 cp), carbohydrate (74.20%), and energy (319.81 kcal) were produced by fermentation in 12 hours with the Bi-Mocaf fermentor. Without fermentation, treatment formed the highest dietary fiber (18.27%) and fat content (0.780%). The processing into flour is expected to expand product diversification and increase the added value of yam tubers.

Compositional and Functional Analyses of Dioscorea Odoratissima (Bush Yam) Flour and Starch as Influenced by Pre-Treatment

Dioscorea odoratissima (DO), an under-utilized famine crop is usually cooked, either peeled or unpeeled before consumption. Information on the effect of peeling on the nutritional attributes of D. odoratissima is scanty. In this study, nutritional and functional properties of flour and starch from peeled and unpeeled DO tuber were evaluated. Flour (UF) and starch (SU) from unpeeled yam tuber was significantly higher in starch compared to peeled yam flour (PF) and starch (PS), respectively. Crude protein content was significantly higher in UF and SU, compared to PF and PS. Alkaloids, phenolics, flavonoid, tannins, and trypsin inhibitor levels were significantly higher in UF and SU compared to PF and PS. PS exhibited significantly higher solubility, pasting clarity and swelling capacity compared to SU. In vitro starch digestibility, α-amylase and α-glucosidase activities positively correlate with amylose/amylopectin ratio in both flour and starch samples. UF and SU exhibited significantly higher antioxidant activity compared to PF and PS. These data emphasize the importance of pre-treatment with regard to applicability of DO flour and starch.

Transcriptome Sequence Reveals Candidate Genes Involving in the Post-Harvest Hardening of Trifoliate Yam Dioscorea dumetorum.

Storage ability of trifoliate yam (Dioscorea dumetorum) is restricted by a severe post-harvest hardening (PHH) phenomenon, which starts within the first 24 h after harvest and renders tubers inedible. Previous work has only focused on the biochemical changes affecting PHH in D. dumetorum. To the best of our knowledge, the candidate genes responsible for the hardening of D. dumetorum have not been identified. Here, transcriptome analyses of D. dumetorum tubers were performed in yam tubers of four developmental stages: 4 months after emergence (4MAE), immediately after harvest (AH), 3 days after harvest (3DAH) and 14 days after harvest (14DAH) of four accessions (Bangou 1, Bayangam 2, Fonkouankem 1, and Ibo sweet 3) using RNA-Seq. In total, between AH and 3DAH, 165, 199, 128 and 61 differentially expressed genes (DEGs) were detected in Bayangam 2, Fonkouankem 1, Bangou 1 and Ibo sweet 3, respectively. Functional analysis of DEGs revealed that genes encoding for CELLULOSE SYNTHASE A (CESA), XYLAN O-ACETYLTRANSFERASE (XOAT), CHLOROPHYLL A/B BINDING PROTEIN 1, 2, 3, 4 (LHCB1, LHCB2, LHCB3, and LCH4) and an MYB transcription factor were predominantly and significantly up-regulated 3DAH, implying that these genes were potentially involved in the PHH as confirmed by qRT-PCR. A hypothetical mechanism of this phenomenon and its regulation has been proposed. These findings provide the first comprehensive insights into gene expression in yam tubers after harvest and valuable information for molecular breeding against the PHH.

Anti-reproductive efficacy of Adansonia digitata Powder against Dinoderus porcellus Associated with Yam Chips Spoilage in Jos Metropolis, Nigeria

This study assessed the reproduction inhibition effects of Adansonai digitata plant part powders against D. porcellus affecting yam chips. Reproduction of adults D. porcellus were monitored with various doses of Adansonai digitata plant part powders and untreated yam chips as negative control (0 g). The finding of the research indicated that all treatments exhibited anti-reproduction potential and strong inhibition of D. porcellus emergence. The result of analysis of variance showed significant difference between the treated samples and the control (untreated) after 37 days. Adansonai digitata stem bark powders (10 g) was able to achieve no reproduction(0.00) after 37 days exposure. Based on this results, combining yam chips with 10 g of Adansonai digitata stem bark powders could ensure adequate management of D. porcellus destroying yam chips and yam tubers as a whole.
 Keywords: Adansonai digitata, D. porcellus, yam chips, Stem bark powder, Leaf powder

Predicting quality, texture and chemical content of yam (Dioscorea alataL.) tubers using near infrared spectroscopy

Despite the importance of yam ( Dioscorea spp.) tuber quality traits, and more precisely texture attributes, high-throughput screening methods for varietal selection are still lacking. This study sets out to define the profile of good quality pounded yam and provide screening tools based on predictive models using near infrared reflectance spectroscopy. Seventy-four out of 216 studied samples proved to be moldable, i.e. suitable for pounded yam. While samples with low dry matter (<25%), high sugar (>4%) and high protein (>6%) contents, low hardness (<5 N), high springiness (>0.5) and high cohesiveness (>0.5) grouped mostly non-moldable genotypes, the opposite was not true. This outline definition of a desirable chemotype may allow breeders to choose screening thresholds to support their choice. Moreover, traditional near infrared reflectance spectroscopy quantitative prediction models provided good prediction for chemical aspects (R2 > 0.85 for dry matter, starch, protein and sugar content), but not for texture attributes (R2 < 0.58). Conversely, convolutional neural network classification models enabled good qualitative prediction for all texture parameters but hardness (i.e. an accuracy of 80, 95, 100 and 55%, respectively, for moldability, cohesiveness, springiness and hardness). This study demonstrated the usefulness of near infrared reflectance spectroscopy as a high-throughput way of phenotyping pounded yam quality. Altogether, these results allow for an efficient screening toolbox for quality traits in yams.

Agricultural price transmission across space and time: The case of cowpea and yam markets in Nigeria

The transmission of price changes to markets has attracted renewed interest since the international food price spikes of 2007 to 2011. In response to this, this paper investigates the long-run behaviour of Nigerian cowpeas and yam tuber retail prices across space and time from 2000 to 2015. We employed the augmented Dickey-Fuller unit root test, the Johansen co-integration test, the Granger causality test, the vector error-correction model (VECM) and variance decomposition analysis. The Johansen co-integration test confirmed the presence of a long-run relationship across the markets, while the VECM revealed that the speed of adjustment to equilibrium after price shocks in the yam and cowpea markets varied across space (market) and period (time), with the food crisis in the period pre-2007 to 2011 fastest and the food crisis in the period 2007 to 2011 slowest. We are of the opinion that the presence of a long-run relationship in Nigerian cowpea and yam markets is a call for participants to explore opportunities for gainful trade.

Quality Evaluation of Yam (Dioscorea rotundata) and carrot (Daucus carota L.) Flour Blends for Production of Stiff Dough and Biscuits

This study evaluates the quality of yam and carrot flour blends for the production of stiff dough and biscuits. Flour samples were prepared from yam tubers and carrot flours .The carrot flour was used to substitute 5, 10, 15, and 20 of the yam flour on the stiff dough. Biscuits were prepared from various blends of wheat flour, carrot flour and yam flours. The proximate composition, functional properties, vitamin, minerals and sensory attribute of the flour blends were carried out using appropriate standard methods for the analysis. The sensory properties of the stiff dough and biscuits were determined. The proximate composition of the flour blends were significantly (P< 0.05) different for the moisture (7.52.-6.89%), ash (2.00-2.36%), protein (4.90-4.55%), fat (1.41-1.25%) and carbohydrate (82.09-77.73%). The water absorption (2.53 – 4.10%) and least gelation concentration( 6.43-12.03%) of the blends increased while the bulk density (0.65-0.53 g/ml), dispersibility (1.49 -2.50%), swelling capacity( 2.59 -3.83%) and foaming capacity (26.73-6.44 g/ml).The blends were rich in iron( 8.43-19.22 mg/100g), zinc (7.43-18.11 mg/100g), magnesium (94.54-170.49 mg/100g) and phosphorus (30.63-84.01 mg/100g). The blends were rich in pro-vitamin A (5.51-17.42). Vitamin B1 (0.43-0.84) and vitamin C (4.81-17.81 mg/100g). The sensory scores recorded on the flour blends for appearances (7.10- 8.50), texture (7.40 -8.10), taste (7.10 -7.85), aroma (6.70 -7.60) and acceptability (6.35-7.70) decreased with increasing level of carrot flour in the blends. The biscuits containing 75% wheat flour, 20% yam flour and 5% carrot flour was the most preferred.