Academic literature on the topic 'Yams – Africa, Southern'

This paper combines the results of surveys carried out between 1995 and 2001 in Benin and Nigeria on farmers' practices in connection with the domestication of yams (Dioscorea rotundata), which is still an active process in West Africa. In Benin more than 500 yam producers belonging to four major yam-producing ethnic groups (Bariba, Mahi-Fon, Nago and Yom) and nearly 300 farmers in six different states of Nigeria were interviewed. The knowledge of wild yams is still alive even among farmers who have never domesticated yam. In the two countries the techniques described are very similar and the domesticated wild yams belong either to D. abyssinica in the northern part of the studied area (drier savanna zone) or to D. praehensilis in the southern part (humid savanna). The percentage of farmers who are domesticating or have recently domesticated yams varies from 3–14%. The domestication process mainly leads to early maturing cultivars, which are produced in double-harvest systems. The practice of domestication is decreasing, especially in the regions where commercial yam production is well developed.

Yams (Dioscorea spp.) are widely grown in China as vegetables and herbal medicine. However, studies on viral diseases on yams are still limited. As a pilot project of a government initiative for improving yam productivity, a small study was conducted in Guangxi, a southern province of China, on viral disease in yams. Incidence of virus-like disease for the three extensively grown D. alata cultivars, GH2, GH5, and GH6, were 12 to 40%, 12 to 29%, and 11 to 25%, respectively, as found in a field survey with a five-plot sampling method in 2010. A total of 112 leaf samples showing mosaic or mottling or leaves without symptoms were collected from the cvs. GH2, GH5, GH6, and seven additional cultivars (D. alata cvs. GY2, GY23, GY47, GY69, GY62, GY72, and D. batatas cv. Tiegun). To determine if the symptoms were caused by Yam mild mosaic virus (YMMV; genus Potyvirus, family Potyviridae), total RNA was extracted from leaves with a commercial RNA purification kit (TIANGEN, Beijing, China), and reverse-transcription (RT)-PCR was conducted with a YMMV-specific primer pair (4) that amplifies the 3′-terminal portion of the viral genome. A PCR product with the predicted size of 262 bp was obtained from samples of GH5 (number testing positive of total number of leaves = 5 of 12), GH6 (24 of 42), and GY72 (1 of 1), but not from asymptomatic leaves. PCR products from a GH5 sample (YMMV-Nanning) and a GH6 sample (YMMV-Luzhai) were cloned and sequenced using an ABI PRISM 3770 DNA Sequencer. The two PCR products were 97% identical at nucleotide (nt) level and with the highest homology (89% identity) to a YMMV isolate (GenBank Accession No. AJ305466). To further characterize the isolates, degenerate primers (2) were used to amplify viral genome sequence corresponding to the C-terminal region of the nuclear inclusion protein b (NIb) and the N-terminal region of the coat protein (CP). These 781-nt fragments were sequenced and a new primer, YMMV For1 (5′-TTCATGTCGCACAAAGCAGTTAAG-3′) corresponding to the NIb region, was designed and used together with primer YMMV UTR 1R to amplify a fragment that covers the complete CP region of YMMV by RT-PCR. These 1,278-nt fragments were sequenced (GenBank Accession Nos. JF357962 and JF357963). CP nucleotide sequences of the YMMV-Nanning and YMMV-Luzhai isolates were 94% similar, while amino acid sequences were 99% similar. BLAST searches revealed a nucleotide identity of 82 to 89% and a similarity of 88 to 97% for amino acids to sequences of YMMV isolates (AF548499 and AF548519 and AAQ12304 and BAA82070, respectively) in GenBank. YMMV is known to be prevalent on D. alata in Africa and the South Pacific, and has recently been identified in the Caribbean (1) and Colombia (3). To our knowledge, this is the first report of the natural occurrence of YMMV in China and it may have implications for yam production and germplasm exchange within China. References: (1) M. Bousalem and S. Dallot. Plant Dis. 84:200, 2000. (2) D. Colinet et al. Phytopathology 84:65, 1994. (3) S. Dallot et al. Plant Dis. 85:803, 2001. (4) R. A. Mumford and S. E. Seal. J. Virol. Methods 69:73, 1997.

Abstract The granitic and leucogranitic Yas and Schuitdrift Gneisses occur together as a large ovoid pre-tectonic batholith that crosses the Orange River border between South Africa and Namibia. They occur in the central parts of the Kakamas Domain in the Namaqua Sector of the Namaqua-Natal Metamorphic Province where they intrude, and are deformed together with, slightly older (~1.21 Ga) orthogneisses and granulite-facies metapelitic gneisses. The Yas Gneiss occurs mainly on the outer perimeter and northern parts of the batholith and comprises equigranular leucogranite gneiss and biotite granite augen orthogneiss, whereas the Schuitdrift biotite-hornblende augen gneiss is located at the centre and southern parts of the batholith. The batholith is strongly deformed with penetrative Namaqua-aged gneissic fabrics defined by grain-flattening of quartz and feldspar in the equigranular leucogneisses and aligned K-feldspar megacrysts in the augen gneisses. The gneissic fabric is refolded during a large-scale folding event that results in the dome-shape of the batholith and controls the present outcrop pattern of its various components. Flexure along the margins of the batholith refoliated the gneisses into a zone of mylonitic rocks. The Yas and Schuitdrift Gneisses have similar geochemistry and classify as alkali granites and alkali leucogranites. They are felsic (mean SiO2: 74.5 wt%) and potassic (mean K2O: 5.8 wt%) but have low MgO, CaO and Na2O, reflecting their low mafic mineral and plagioclase contents. The Schuitdrift Gneiss yielded U-Pb zircon ages of 1 191 ± 7 and 1 187 ± 6 Ma.

Background: The total antioxidant capacity of yam food grown in southern African regions was investigated by a polyglycine-glassy carbon modified electrode. The modified electrode was fabricated using glycine solution on glassy carbon electrode by electrodeposition method. The proposed modified electrode is found to be nearly 3.15-fold more sensitive than the bare electrode. For the measurement of the total antioxidants of yam, differential pulse stripping voltammetry (DPSV) was employed with standard quercetin compound. Methods: The total antioxidant capacity of yam was deduced by DPSV and cyclic voltammetry (CV) methods. The basic parameters for the stripping technique such as pH, accumulation time and accumulation potential were optimized as 20 s, 200 mV and a pH of 3 Britton-Robinson (B-R) buffer solutions in 0.5 mg quercetin/L, respectively. Results: In the optimization condition, the linear working range was determined between 5.0 μg/L and 80.0 µg/L for the quercetin. The detection (LOD) and quantification (LOQ) limits of quercetin were found to be 0.39 µg/L and 1.39 µg/L on the modified electrode by DPSV, respectively. The procedure was also applied to natural yam samples and total antioxidant capacity of 0.1 kg of yam was determined as 96.15 ± 0.85 µg/L of equivalent quercetin at 95% confidence level with the relative standard deviations of 0.88%. Conclusion: Sensitive and selective voltammetric method was developed for the determination of total antioxidant capacity in yam. Moreover, the modified polyglycine-glassy carbon electrode was constructed more selectively for quercetin. As a result, a simple, sensitive and rapid new voltammetric method for the determination of antioxidants has been developed using the modified electrode.

Notulae Scientia Biologicae (http://www.notulaebiologicae.ro), Issue 2, Volume 10, 2018: The papers published in this issue (http://www.notulaebiologicae.ro/index.php/nsb/issue/current) represent interesting novelties in different topics of life science. Among the exciting researches, we invite you to find news about: combining microsatellite markers and ampelography for better management of Romanian grapevine germplasm collections; investigation of the breeding mechanism of African yam bean (Sphenostylis stenocarpa); ultrasonic assisted seed priming to alleviate aging damages to milk thistle (Silybum marianum) seeds; floristic diversity, vegetation analysis and threat status of plants in various forest types in Dharmapuri Forest Division, Tamilnadu, Southern India etc. Notulae Scientia Biologicae journal has moved to online-only publication at the start of 2017. At the same time, we maintain our standard publication, as printed form, with 'classic' style - volume, issue, pagination.

Abstract A new distribution map is provided for Beet mosaic virus. Potyviridae: Potyvirus. Hosts: beetroot (Beta vulgaris), sugarbeet (Beta vulgaris var. saccharifera) and white yam (Dioscorea alata). Information is given on the geographical distribution in Europe (Albania, Austria, Belgium, Bulgaria, Croatia, Czech Republic, Denmark, France, Germany, Greece, Mainland Greece, Italy, Mainland Italy, Lithuania, Netherlands, Poland, Portugal, Russia, Far East, Southern Russia, Slovakia, UK, England and Wales, Ukraine), Asia (China, Nei Menggu, Shandong, Xinjiang, Iran, Israel, Japan, Hokkaido, Kazakhstan, Kyrgyztan, Lebanon, Turkey, Uzbekistan), Africa (Egypt, Nigeria, Tunisia), North America (USA, California, Colorado, Idaho, Michigan, New Mexico, Texas, Utah, Washington, Wisconsin), South America (Argentina), Oceania (Australia, Queensland). Beet mosaic virus is transmitted in a non-persistent manner by more than 28 species of aphid, including Myzus persicae and Aphis fabae (Hemiptera: Aphididae).

In this investigation the chemistry of three southern African plants used for medicinal purposes was investigated. The plants were Dioscorea dregeana, Avonia rhodesica and Equisetum ramossisimum. Extracts of all three of these plants have been found to be active on the central nervous system. The structures of the compounds isolated were determined by using 1H and 13C n.m.r., i.f., UV-VIS, - mass spectroscopy and chemical methods. D. dregeana yielded two alkaloids and three aromatic compounds. A. rhodesica contained a large amount of wax which was analysed by GC-MS and its distribution and physical nature on the surface of the leaves was determined by SEM (scanning electron microscopy). This plant also contained two sterols. Equisetum ramossisimum extracts contained a carotenoid and several porphyrins, as well as large amounts of silica. A DTSA X-ray microanalysis system (which was a component of the scanning electron microscope) was used to determine the distribution of silica in the stem.
Thesis (M.Sc.)-University of Natal, Durban, 1998.

AbstractClimate change is a global issue threatening food security, environmental safety, and human health in tropical and developing countries where people depend mainly on agriculture for their livelihood. Nigeria ranks among the top in the global yam production. It has the largest population in Africa and has been able to secure food for its growing population through food crops especially yam. Unfortunately, the recent increase in termites’ colonies due to climate change threatens yam yield. Besides harming man and environment, pesticides are expensive and not easily accessible to control the pests. This prompted a study which aimed at applying a biotrado-cultural approach in controlling the termites, as well as improving soil chemical properties and yam production. The study hypothesized that Chromolaena odorata and Elaeis guineensis sludge improved soil nutrient and yam yield and consequently decreased termites’ outbreak. In a randomized design experiment of five blocks and five replicates, five different treatments including unmanaged (UM), Vernonia amygdalina (VA), Chromolaena odorata (CO), Elaeis guineensis (EG) liquid sludge, and fipronil (FP) were applied in termites-infested agricultural soil. Data were collected and measured on the responses of soil chemical properties, termites, and yam yield to treatments using one-way ANOVA, regression, and multivariate analyses. The result showed that Chromolaena odorata (CO) and EG treatments were the best treatments for controlling termites and increase yam production. Termites were successfully controlled in VA and FP treatments, but the control was not commensurate with yam production. The experiment needs to be extended to other locations in the study region. It also requires an intensive and long-term investigation in order to thoroughly understand (i) the influence of climate change on the termites’ outbreak, (ii) the extent of termite damage to the crops, (iii) the impacts of climate change and variability on yam yields, (iii) the agricultural and economic benefits of the applied treatments, and (iv) the ecological and human health safety of the treatments.