Yam Dioscorea Research Articles

Performance of Yam (Dioscorea spp.) Varieties in East-Central Puerto Rico

The highest yielding yam cultivar in a yield trial planted at the Corozal Substation in east-central Puerto Rico was Seal Top (Dioscorea alata). It produced an estimated yield of 40.17 metric tons/ha (358.66 cwt/acre). The cultivar yielding least was Guinea amarillo (D. cayennenis) which produced 9.373 metric tons/ha (83.69 cwt/acre). Besides producing high yield when compared with locally planted cultivars, the tubers of Seal Top, Barbados and Smooth Statia are ovoid without attached roots, thus suitable for mechanical harvesting. Farm Lisbon and Hunte tubers are bifurcate and unsuitable for mechanical harvesting. There is little local market demand for tubers of this type of yam.

A new approach to improvement of yam Dioscorea rotundata

EFFORTS to improve the yam, D. rotundata, through hybridisation have been frustrated by the low rate of flowering, the very low rate of fruit setting and poor seed germination1–3. These constraints have confined the availability of genetic resources for selection to the small number of cultivars which have been vegetatively reproduced from time immemorial. This continued vegetative propagation and the lack of hybridisation have precluded the possibility of introduction of new genetic characteristics, resulting in a stagnation of yam improvement. To facilitate yam hybridisation, we have re-examined the problems of flowering and seed germination. We first reported4 yam seed germination in November 1973, and Doku stated that he had germinated yam seeds of D. rotundata (unpublished). Here we report the feasibility of germinating yam seeds, the rapid improvement of flowering, and the opportunity this development affords for expanding present germ plasm collections, thus facilitating yam improvement.

Título en español.

Se estudiaron algunas de las propiedades más importantes del almidón del ñame Florido (Dioscorea alata L.). El almidón contiene un 34 porciento de amilosa, el gránulo es de forma ovalada y tiene un diámetro de 31 µm, excediendo ambos los valores informados en la literatura. La viscosidad del almidón aumentó durante todo el proceso de cocción y enfriamiento. El almidón no exhibió un punto de viscosidad máximo, lo cual refleja la estabilidad del gránulo hinchado.

PREPARATION AND STORAGE PROPERTIES OF DRUM DRIED WHITE YAM (Dioscorea rotundata Poir) FLAKES

The white yam Dioscorea rotundata Poir was characterized, drum dried to different moisture levels, and stored at temperatures of 21.l °C, 29.4 °C and 37.8 °C for 90 days. Fresh and stored samples were analyzed for changes in color, ascorbic acid and organoleptic qualities. Freshly dried and reconstituted yam flakes were judged highly acceptable compared to conventionally mashed fresh yam and retained acceptability through storage. The taste panel consisted of persons from several West African countries. Changes in the flakes during storage are described.

Título en español.

Se estudiaron las características de la pastosidad en mezclas acuosas de ñame Florido (D. alata) preparadas de hojuelas instantáneas de cinco tamaños diversos. También se determinó el índice del valor azul (blue value index) en las cinco muestras. El tamaño de las hojuelas tuvo un marcado efecto en el índice del valor azul y en la viscosidad de las mezclas acuosas, según determinación hecha por el Amilo-Viscógrafo Brabender. El coeficiente de correlación entre el valor azul y la viscosidad inicial de las mezclas acuosas preparadas de hojuelas de ñame fue bastante alto (r = 0.96).

The response of yam (Dioscorea rotundata) to fertilizer application in Northern Ghana

SummaryField trials were carried out for three years in the savanna zone of northern Ghana to determine the fertilizer requirements of yam (Dioscorea rotundata). Under the conditions of the experiment, K was not important in yam fertilization. Release from the exchangeable reserves was adequate in meeting the crop demand. A small positive response to P applied at low levels (33·6 kg/ha) was observed and averaged only 5·6% increase in yield. N was the most important nutrient element and its application increased yields highly significantly. On the average, application of 33·6 kg/ha gave an increase of 13·5% and 67·2 kg/ha gave a 22·1% increase in yield. More N did not further increase yield.

Nematode Problems with Yams (Dioscorea spp.) in Nigeria

(1972). Nematode Problems with Yams (Dioscorea spp.) in Nigeria. PANS Pest Articles & News Summaries: Vol. 18, No. 1, pp. 89-91.

Two Types of Swidden Agriculture in Tropics

The swidden agriculture is widely distributed in the tropical zone. Its distribution seems to have been already clarified by D. Whittlesey. As it is well known, D. Whittlesey had classified this tropical native agriculture as two types: shifting cultivation and rudimental sedentary tillage.Nevertheless, according to the recent scientific results his two types are not always considered to be suitable to explain the tropical native agriculture. (Refer to Morgan, W.B.: Agriculture in Southern Nigeria, Econ. Geogr. Vol.35, 1959). Furthermore, among the researchers there are so diversified appreciation about the swidden agriculture that a scientific tendency has been brought on to seek after certain new type in the swidden agriculture in the tropics. For example, Komei Sasaki, having located many principal treatises of tropical swidden agriculture in the history, has suggested the two types concept in the Human Geography (The Jimbun-Chiri) Vol.17, No.6, 1965.:1) Millet cultivation type brought about in the Savanna environmentand2) Root cultivation type in the Rain Forest environment. Including Sasaki's concept most of the tropical swidden agricultural studies had been mainly centered upon the crop complex as well as upon the crop rotation system. Really they are mere one partial concept of the agriculture, and in such studies, we should say, they are touching to the agricultural complex rather at the standpoint of time than at its spacial side. Primarily doing of agriculture is embodied in cultivation of the ground. In this sense it is not to be approved that the concept of types centering upon the crop complex and the crop rotation system has enough ground to rely on.Therefore, in this treatise, I would like to investigate these types in touching to the crop rotation system at the standpoint of time and simultaneously to the land use pattern from the side of space. In other words, I am going ahead with my studies upon the relation between the crop rotation system and the land use pattern at the unit of village. I picked up as my research field Nigeria, West Africa, where presents a sharp contrast between the Savanna environment and the Rain Forest environment.According to the concept of the swidden agriculture in West Africa there are counted 9 kinds of the staple subsistence crop: Fonio Digtaria exilis, Maize Zea mays, Pearl Millet Pennisietnm typhoideum, Sorghum Sorghum spp., Finger Millet Eleusine coracana, Manioc Manihot utilissima, Taro Colocasia antiquorum, Yam Dioscorea spp., Plantain Musa sapientum, M. paradisiaca.Most extensively distributed cereals in Western Africa are Pearl Millet and Sorghum. They are cultivated at the Sudan Belt in the Savanna environment. On the other hand the representative crop from Roots is Yam. Maize has the range in every areas.The crop rotation system is found in Northern Nigeria where Pearl Millet and Sorghum are taken as staple subsistence crop. In Middle and Southern Nigeria Yam is the first year's crop in its rotation system. In Southern Nigeria there is one or two years of cultivated period and the planted crops are almost Roots. In some areas the planting percentage of Maize amounts 20-30%. In the Intermediate area between the North and the South, the rotation system is generally practised: in the first year they plant Yam, then after Cereals and Roots by rotation. In such a process we are able to recognize the transitive phases from the crop rotation system toward the millet cultivation type or the root cultivation type which Sasaki had suggested. This root cultivation type also coincides with the wood fallow as the fallow system.In comparing with each land use patterns at the unit of village, it has been made out that this pattern distinctly reflects the crop rotation system.

Microbial Rotting of Stored Yams (Dioscorea spp.) in Nigeria

SUMMARYThe incidence of rotting among three varieties of yams (Dioscorea rotunda, D. alata and D. cayenensis), stored in a yam barn at Ibadan for about four months, was between 0·6 and 68·5 per cent. The micro-organisms which caused rotting on experimental re-inoculation into yam tubers were the fungi, Botryodiplodia theobromae, Penicillium sp., Marcophomina phaseoli, Hendersonula toruloidea and a motile gram-negative orange-red pigmented bacterim, probably Serratia sp. This is the first record of the ability of M. phaseoli, and H. toruloidea to cause rotting in yam.

Respiration in Yam Tuber Tissue

YAMS (Dioscorea spp.) are major food crops in many tropical countries. Global production of the edible tubers is approximately 20 million tons/year, the most important producer area being West Africa, where they often contribute up to half the total calorific intake of the population1. The tubers are frequently stored for periods of several months and, although they are generally said to ‘store well’, it has been shown2–4 that appreciable losses in weight, of the order of 10 per cent after 3 months, and 25 per cent or more after 6 months, occur during the storage even of sound tubers. A number of storage rots are known5, and attack by these organisms can further enhance storage losses. It has been estimated1 that around a million tons of yams are lost, annually, in storage.

Observations on yams attacked by the yam beetle Heteroligus meles (Billb.) (Col., Dynastidae)

Several species of Dynastid beetles are serious pests of yam (Dioscorea) in Nigeria, the adults attacking the setts and new tubers underground. The base of the yam vine and the roots are not generally damaged. The most important species is Heteroligus meles (Billb.).H. meles does not breed in the yam fields, and the adults fly to them from breeding grounds that are distinct, and to which they return later.The cultivation and growth of the yam plant in Nigeria are briefly described. Small tubers, or cut pieces of tubers (setts) are planted. The earlier the date of planting and of emergence of the vine from the soil, the heavier the vine and the new tuber.An account is given of observations on the infestation, in relation to crop growth, of a plot of yellow yams (D. cayenensis) planted near Benin, in Western Nigeria on 29th March 1958.Adults of H. meles were taken, from 3rd April to 26th June and again from 8th to 21st November, between 7 and 9 p.m., at a light-trap placed at a distance of ¼ mile from the plot.Beetles entered the soil of yam hills within six inches of the vine, usually before 7 a.m., on mornings following evening flights, the entry holes usually being identifiable. The first vines were seen in the experimental plot on 19th April. Beetles did not enter a yam hill unless the vine had emerged.The longer the exposure to flying beetles, the more likely were plants to be attacked, and bigger vines attracted more beetles than did smaller ones. Later planting decreased beetle damage, but a lower yield resulted.At first the beetles fed on the sett, making and increasing the size of fewer lesions than later on the new yam. About the time that the flying period ended, the setts were starting to rot, and the beetles left the immediate vicinity of the yam plant, as no acceptable food was available. Most moved deeper into the soil, but a few left the plant altogether and flew away. After the new tubers had begun to develop, the beetles returned in early August from their positions deeper in the soil to feed on them, constantly making new lesions, more numerous but smaller than those made in the setts, averaging about 4 g. of yam eaten.During late August and again in late September, a few beetles moved underground from the original plants attacked to others. In mid-November, the beetles left the yam fields altogether, presumably returning to the breeding area.The reasons why the beetles fly away from the yam fields remain uncertain, but they may include the seasonal decline in rainfall, the maturation of the yam tuber and the development of the gonads.Factors that can affect the rate of attack are the dates of planting and harvesting in relation to the period during which the beetles fly, the method of cultivation and the variety of yam planted.

Yams and liver necrosis.

YAM (Dioscorea rotundata) is widely consumed in Ghana and other parts of West Africa and in some regions forms a staple of the diet. Toxic principles have been isolated from some species of yam, and it is widely known among farmers that the consumption of particular forms of yam may prove fatal1. Other species of yam when eaten in large quantities are said to lead to stupefaction2. It seemed desirable, therefore, to examine more closely the nutritional properties of those species of yam consumed commonly in Ghana.