1,741,899 research outputs found
Arbuscular mycorrhizal fungi in the Sub-Saharan Savannas of Benin an their association with yam (Dioscorea spp.) : potential of yam growth promotion and reduction of nematode infestation
No full textThe arbuscular mycorrhiza is the most widely occurring and important microbial symbiosis for
agricultural crops and well known to facilitate plant mineral nutrient uptake, particularly under
conditions of P-limitation - as it is common in tropical soils due to leaching or/and severe
immobilization - and, moreover, it is understood to improve plant water relations and provide
resistance against pests and pathogens. Yam (Dioscorea spp.) is the most important tuber crop in
terms of coverage area in West Africa, particularly in Benin and Togo. Alarmingly, the annual
yam production per hectare has recently decreased considerably due to a loss of soil fertility and
pest and disease (especially nematode) damage. Under field conditions, yam and arbuscular
mycorrhizal fungi (AMF) are naturally associated with each other. Currently, however, data on
the ecology of AMF in West Africa are lacking with very limited information on the mycorrhizal
status of yam. There may be potential to improve growth and to protect plants against nematodes
by AMF but this is possibly dependent on specific AMF-nematode-host combinations. The
present project aimed at studying AMF indigenous to West Africa, with respect to yam growth
promotion and yam nematode suppression. The specific objectives focused on assessing the (1)
diversity of AMF, including their distribution, abundance and relation to agronomic practices
and ecological conditions; (2) the mycorrhizal status of yam; and (3) the specific associations
between (a) yam-AMF, and (b) yam-AMF -nematode in vivo under greenhouse conditions.
In the first part of our study, we determined the influence of three ecological zones (from wettest
to driest) and of land use intensity on the diversity of AMF in the yam growing area of Benin,
West Africa. In each zone, four ‘natural’ and four ‘cultivated’ sites were selected. ‘Natural’ sites
included three natural forest savannas (at least 25-30 years old) and a long-term fallow (6-7 years
old). ‘Cultivated’ sites comprised yam fields established immediately following forest clearance,
mixed cropping maize (Zea mays) and peanut (Arachis hypogaea) fields, peanut fields, and fields
under cotton (Gossypium hirsutum), which was the most intensively managed crop. Soil samples
were collected towards the end of the wet season in each zone. AMF spores were extracted and
identified morphologically. A total of 60 AMF species was detected, with only seven species
sporulating in AMF trap cultures that were set up with various AMF host plants. Higher species
richness was observed in the northern most, driest ecological zone Sudan Savanna (SU) than in
the adjacent zones to the south with increasing humidity, namely the Northern Guinea Savanna
(NG) and the Southern Guinea Savanna (SG), mainly due to a high proportion of species in the
Gigasporaceae, Acaulosporaceae and Glomeraceae. Within each ecological zone, spore density
and species richness were generally higher in the natural savannas and in association with yam
than in the other cultivated sites. These parameters were lowest under the intensively managed
cotton, and intermediate in the fallows, indicating that the high richness of the natural savannas
is not necessarily restored during fallowing.
Assuming that yam is an arbuscular mycorrhizal crop, we addressed the question of which AMF
species are associated with yam. Our aim was to propagate the AMF communities from three
natural forests and three adjacent yam fields of the SG in Benin in trap cultures and to assess the
AMF richness, identifying those associated with yam. Soil samples were collected in the dry
season (February 2005) and used to identify AMF spores directly and also to establish AMF trap
cultures on yam (tissue culture plantlets of D. rotundata and D. cayenensis) and, for comparison,
on Sorghum bicolor. In the trap cultures, AMF root colonization was particularly high in yam
(70-95%), compared with S. bicolor (11-20%). Based on spore morphotyping, 37 AMF species
were detected in the ‘trap’ rhizosphere of S. bicolor, while 28 and 29 species were identified as
fungal symbionts of D. cayenensis and D. rotundata, respectively. Following eight months
cultivation in trap cultures, yam tuber dry weight was generally higher in mycorrhizal than in
non-mycorrhizal control pots.
We also hypothesized that indigenous AMF species and strains isolated from yam plantlets in
trap cultures may be more beneficial for yam plant growth compared to non-indigenous isolates.
We screened indigenous AMF species and strains that have been isolated from the trap cultures
and compared their effects on micro-propagated white yam plantlets (D. rotundata) (cv. TDr89-
02461) against exotic AMF isolates in pot experiments over seven months. First, we tested
several indigenous and non-indigenous (South America and Asia) G. etunicatum strains with
regard to their effect on yam growth promotion and mineral accumulation in the tissues.
Secondly, three isolates each of nine indigenous AMF species and three additional non-tropical
AMF species were screened on the same yam cultivars. We found that most tropical AMF
isolates of G. etunicatum increased yam tuber dry weight, while the non-tropical AMF isolates
had a lower or no effect, but instead increased tuber P concentrations, when compared to nonmycorrhizal
controls. Glomus mosseae, G. hoi, G. etunicatum, Acaulospora scrobiculata and A.
spinosa generally had a positive effect on tuber growth, while isolates of G. sinuosum and
Kuklospora kentinensis generally did not.
Finally, we assessed the interaction between yam and AMF in the presence or absence of plant
parasitic nematodes. Yam vplants cultivated in vitro were used, which were inoculated with
commercial inocula of G. mosseae and G. dussii (Biorize, Dijon France). In the presence of
nematodes (Scutellonema bradys and Meloidogyne spp.), inoculation of G. mosseae generally
increased growth of micropropagated yam plantlets and yam tuber weight production, especially
cultivars from D. alata. Tubers were, in general, less infected with S. bradys, but not necessarily
with Meloidogyne spp. However, application of G. mosseae and G. dussii to micropropagated
plantlets resulted in improved quality of yam tubers, when challenged with nematodes, compared
to nematode inoculation without AMF, indicating a positive effect of AMF on yam productivity.
Our results indicate that the AMF richness is high in the ‘yam belt’ of Benin, but that it is
strongly influenced by the ecological zone and by the intensity of land cultivation after forest
clearance. Our results also indicate that in controlled pot studies, AMF can suppress nematode
damage and additionally lead to improved quality and weight of yam tubers. The present results
remain preliminary, however, while results from ongoing studies currently in the field will help
to determine further their potential in the longer term. These results provide exciting prospects
for African crop production, in addition to illuminating the wide and diverse species richness of
West African AMF and their potential benefits
An Analysis of the Supply for Seed Yams in Nigeria
No full textThis study was conducted to examine the supply of seed yam in major yam producing areas of Northern and Southern Nigeria using the supply function analysis. A cost-route approach was adopted in eliciting data from 120 seed yam farmers and marketers spread across the six states studied in 2006 using the multi-stage random sampling technique. Results show that price of seed yam and age had a significant relationship with value of seed yam supplied at the 1.0% level. Disposable income was significant at the 5.0% level, while labour cost and supplier experience were negatively related with value of seed yam supplied at the 10.0% and 1.0% levels respectively. Price of substitute and credit had a negative relationship with value of seed yam. The elasticity of supply of seed yam with respect to income is positive but inelastic while the elasticity of supply with respect to years of experience and labour were negative and elastic. Price of seed yam had positive price elasticity. Result of the field work show that there were no commercial structures for supply of seed yam in Nigeria. Farmer’s only sell seed yams after satisfying own requirements. The results therefore call for policies aimed at ensuring framers entitlement to productive resources and to target farmers in credit and large-scale farm enterprise.Seed Yams in Nigeria, Determinants of Supply and Supply Elasticities
State of the art of yam production
No full textYam is a labor-intensive and weed-sensitive food crop. The labor-intensive nature of the yam means that the production process requires the attention of the farmer all year round. However, the dwindling labor situation and the proliferation of weeds have forced farmers to think of modern ways of controlling weeds on their farms, that is, the adoption of chemical (herbicides) weed control. Even though the adoption of these chemicals has no doubt brought relief to the farmers and has resulted in increased yam production over the years, it has also brought in its wake, negative externalities of environmental pollution, human health effects, and food quality issues. The study was thus designed to investigate how yam is produced, the human and environmental health effects of how yam is produced, and food quality effects of how yam is produced. This was done through literature review, and field and laboratory experiments. It was revealed that, in recent years, new innovations have been introduced in yam production, the manner in which farmers handle herbicides in their yam production process exposes them to high doses of pesticides, thereby endangering their lives. The study findings also suggest that the use of herbicides in yam production does not affect the quality of the yam
The search for bioactive compounds in tropical plants to target hormone imbalance associated diseases
No full textBenign prostatic hyperplasia (BPH) and/or prostate cancer (PC) will affect at least 50% of the
males once they have reached their fifties. However, despite the range of medical therapies
available, effective treatment against BPH and PC still currently remains inadequate for some.
The annoying symptoms of BPH are mainly attributed to an enlarged prostate. Therefore, the
current treatment strategy is to halt the androgen-dependent growth of the prostate and reduce
its size. Several drugs have been employed with variable success to control prostatic growth.
However, patients tend to self-medicate over a long period. As a result, this leads to another
problem, unpleasant long-term side effects.
The treatment of PC in its early stages often warrants disease free survival for about 70-80% of
the patients. Despite early aggressive therapy, 20% of the cases, unfortunately, experience
disease progression to a state where the cancer no longer responses to therapy. At the
moment, well-established medical options for this condition are limited and thus PC is one of the
leading causes of cancer-associated deaths in western countries.
Evidence has supported the undoubted role of the androgen-signalling pathway in BPH, the pre
cancerous prostatic hyperplasia and dysplasia that may progress to PC. The reduction of
androgen-dependent prostatic growth has been the rational endocrine therapy for both BPH and
PC. However, since the etiology of both diseases is multi-faceted, it is necessary to consider
other contributing factors to develop more effective medication.
Medicinal plants are considered to be multi-component drugs (they contain numerous
phytochemicals) and are thought to display a wide range of beneficial effects. They have been
used therapeutically for centuries. Because of their historical place in medicine, they may have
a better safety profile than synthetic drugs.
The objective of this thesis is to identify tropical medicinal plants, which could be used to target
or support treatments for BPH and PC. Twenty herbal plants, with no known to date indications
for both diseases, were selected. They were fractionated by using different ethanol (EtOH)
concentrations. The initial screen (Chapter 4) aimed to identify plant extracts with the ability to
inhibit the proliferation of LNCaP cells, an androgen dependent human prostate cancer cell line.
All extracts were tested at a concentration of 30 μg/mL.
Four extracts, Api, (70% EtOH Alpinia oxyphylla extract), Aquil (70% EtOH Aquilaria sinensis
extract), Astra (aqueous Astragalus membranaceus extract) and P9605 (96% EtOH Piper
cubeba extract) were selected for further investigations.
Recent research has demonstrated that androgens are not solely responsible for BPH and PC,
estrogens, defective apoptosis and inflammation are, for example, also involved. An
experimental test system using several methodological approaches was designed to test the
above-mentioned extracts. The potential cytotoxicity of the extracts was investigated first to
ensure that they did not attenuate LNCaP growth by inducing unspecific cell death. The extracts
were also tested on HepG2 cells, a human hepatocarcinoma cell line, to identity any potential
induction of liver-toxicity. Anti-androgenic and anti-estrogenic effects were determined by
observing if the extracts 1) blocked the production of certain androgens and estrogens, 2) the
steroid hormone receptor activation process, and 3) the actions of these sex hormones. The
ability to induce apoptosis and the anti-inflammatory properties of the extracts were also tested.
The methods employed were validated and synthetic controls were used whenever possible
and compared with literature.
Api reduced the cellular viability of LNCaP and HepG2 cells at 20-30 μg/mL. It was not further
investigated because the apparent reduced LNCap cell growth was most probably attributed to
due to its cytotoxicity. The other extracts were non-cytotoxic on both cell lines at 30 μg/mL.
Astra inhibited androgen-dependent growth of LNCaP cells, however it did not show significant
anti-androgenic, anti-estrogenic and anti-inflammatory properties. Unfortunately, it is beyond
the scope of this project to discover its anti-proliferative mode of action.
The results of Aquil and P9605 derived from the test system were more promising. P9605
inhibited 5a-reductase type II and aromatase, which were involved in synthesising
dihydrotestosterone (DHT) and estradiol respectively. It also antagonised the effects of DHT by
several mechanisms. Furthermore, it inhibited the cyclo-oxygenases (COX) and 5-lipooxygenase
which are involved in generating inflammatory mediators. Aquil possessed similar
properties as P9605, except that it had no effects on the COXs.
In conclusion, we have identified some possible mechanisms of 2 tropical plants, Aquilaria
sinensis and Piper cubeba, which could potentially be used to prevent/alleviate BPH and/or PC.
This is the first time that these plants have shown to possess anti-androgenic and antiestrogenic
properties
Factors Affecting Antioxidative Ability of Dioscorea Yam-Containing Surimi Gel
No full text[[abstract]]Previous research indicated that addition of Dioscorea yam to surimi gel resulted in the mark decrease of antioxdiative ability in yam-containing surimi product. The objective of this study was to investigate the factors affecting the antioxidative ability of yam-containing surimi gel, including heating treatment, salt addition and surimi gel. Total phenolic content and reducing power of Tainung No. 1 Dioscorea yam decreased about 40% and 50% respectively, after heating at 90℃ for 30 min, while the DPPH scavenging ability was not affected. Addition of various proportions of different salts (NaCl, KCl or MgCl2) did not affect antioxidative ability of Dioscorea yam. Extraction of Dioscorea yam with 50% ethanol of various pH condition (pH 3-11) did not influence antioxidative ability. Although salt addition or heating treatment may improve the gel-forming ability of surimi-gel product, they resulted in the decreases of total phenolic content in yam-containing surimi product. The combination of salt addition and heating treatment appeared to decrease total phenolic content. Due to the non-detectable DPPH scavenging ability in yam-containing surimi product, it is necessary to elevate the DPPH scavenging ability to detectable range by adding gallic acid prior to the investigation of possible factors affecting antioxidative ability in yam-containing surimi product. Salt addition alone did not affect total phenolic content, DPPH scavenging ability and reducing power, while heating treatment resulted in the decrease of total phenolic content and DPPH scavenging ability
Effect of drying conditions of yam ( Dioscorea japonica Thunb.var.
No full text[[abstract]]The focus of this study is to develop the optimal drying method
for yam(Dioscorea pseudojaponica Yamamoto) . Various
processing approaches were used, including freeze drying, cold
air drying, and hot air drying. Several product aspects were
examined , including physicochemical proerties ,biologically
active ingredvients,and sensory evaluation. Then we chose the
peel-containing yam powder with higher diosgenin contant and
better antioxidant actives to produce starch vermicelli. The
vermicelli showed that the freez drying yam product,had
highest L value, solution viscosity, sensory evaluation scores,
and diosgenin residue.
The physicochemical properties of starch vermicelli with
the additive of freezing drying flours derived from
peel-containing yam were examined. It showed that the lowest
yam powder content group had the highest Lvalue, WI
value,tensile force ,and sensory evaluation scores. Basing on
the biologically active substances contant and sensory
evaluation scores of starch vermicelli, the product with 50%
yam powder is better than other test group
The Making-decision of Meteropolitan Consumer of Yam in Taiwan
No full text[[abstract]]Due to the increase of national income, people start to change their habit of consumption, leading ahead towards the selection of healthy foods. For this reason, agricultural units recently attempt to introduce an ideal sort of healthy food, Yam ,into the domestic market with the purpose of adding alternatives as well as incomes of the farmers. However, the result of the introduction was unsatisfactory as throughout the years, the planting area has been decreased from 500 acres to 144 acres (with the data of the year of 2005). For this, we have to explore the reason, answering what are the decisions of consumers? Is there any strategy to promote the competitiveness of Taiwanese Yam? Answers of all these questions constitute an essential part of this paper.
The paper adopts the following approach which further divides the consumers? decisions into the various stages in sequence: the demand of recognition, the collection of information, pre-buying evaluation, stage of purchase, stage of consumption, stage of divestment. With the methods of questionnaires and interviews, the study analyzes and compares all divergent decisions influencing consumers? decisions of purchasing Yam, thinking the possibility of proposing a direction for the later development and management of Yam in the Taiwanese market. The results discovered by this study are: The domestic consumers of Yam prefer still the Japanese products and the major way of consumption are cooking for health. Generally speaking, the different brands of Yam remain unknown for the domestic consumers who are keen to select domestic Red Yam
Food poisoning due to yam flour consumption in Kano (Northwest) Nigeria
No full textFood poisoning is known to occur sporadically from time to time due to poor hygienic preparations. Its occurrence rarely assumes epidemic proportion. The objective was to report the occurrence of food poisoning due to yam flour among three families which occurred almost in quick succession between March and July 2007 among three families in Kano. They presented with diarrhea, vomiting, abdominal pain, convulsion and loss of consciousness. They all recovered within 48hours of admission. Investigations indicated that the use of certain lethal preservatives for the processing of the yam flour might be responsible. Poisoning from consumption of yam flour should be a differential diagnosis of acute seizure disorders or occurrence of vomiting, diarrhea and abdominal pain in the tropics. It is recommended that education on proper processing of all food products in view of the public health implicatio
Model-based Gait Recognition
No full textModel-based Gait Recognition concerns identification using an underlying mathematical construct(s) representing the discriminatory gait characteristics (be they static or dynamic), with a set of parameters and a set of logical and quantitative relationships between them. These models are often simplified based on justifiable assumptions such as the system only accounts for pathologically normal gait. Such a system normally consists of gait capture, a model(s), a feature extraction scheme, a gait signature and a classifier (Figure 1). The model can be a 2- or 3-dimensional structural (or shape) model and motion model that lays the foundation for the extraction and tracking of a moving person. An alternative to a model-based approach is to analyse the motion of the human silhouette deriving recognition from the body’s shape and motion. A gait signature that is unique to each person in the database is then derived from the extracted gait characteristics. In the classification stage, many pattern classification techniques can be used, such as the k-nearest neighbour approach
Yam affects the antioxidative and gel-forming properties of surimi gels
No full text[[abstract]]"The antioxidative activities and textural properties of pollock surimi gels containing four
different yams were determined to evaluate the potential of using yam as a health ingredient and an
alternative source for starch in surimi-based seafoods. Surimi gels containing 20% fresh yam showed
higher α,α-diphenyl-β-pricryl-hydrazyl (DPPH) radicals scavenging activities and total phenolic contents
than the gels without yam. Two tested cultivars, 70W34 and 70W35, did not show significant reductions
in antioxidative activities when used in surimi gel while three other cultivars revealed species-dependant
declines in both the DPPH scavenging activities and total phenolic contents. The surimi gel containing
the cultivar 70R20 showed the highest breaking forces and deformations. In general, 20% fresh yam could
be used to form a yam-containing surimi gel having similar textural properties with a potato starch
containing pollock surimi gel. The dried yam powders might be used at the amount of 30% fresh yam
equivalent without causing significant losses of the textural properties of pollock surimi gels.
2005 Society of Chemical Industry
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