Fulltext – Functional Properties of Bitter Yam (Dioscorea dumetorum) as Influenced by Soaking Prior to Oven-drying. The plant is often purposely grown at spare points on the land as an insurance against famine years, and is also encouraged in hedgerows around a farm and. Notes. BRIEF DESCRIPTION A climbing vine with robust, spiny stems reaching up to m in length. The leaves are trifoliate with ovate leaflets, cm long.
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Search Titles Subjects Organizations. Root Crops 2nd edition NRI,p. Botanical name Dioscorea spp. Botany Dioscorea is a large genus of over species with subterranean tubers or rhizomes. The tubers are storage organs and often grown to a considerable size; they produce short, fibrous roots and annual shoots, which are twining except in dwarf speciesthe direction of twining being specific.
The leaves are petiolate, often cordate, with strongly marked reticulate veining unusual for a monocotyledonsometimes lobed, occasionally palmately compound. Many species produce bulbils in the dumeorum of the leaves which have the morphology and appearance of condensed stems and in a few instances are relatively large and tuberous. The flowers diozcorea small, and borne in long racemes, with male and female separate and usually borne on different plants.
The female flowers are followed by dehiscent capsules, usually trilocular, with 6 seeds, usually winged for wind dispersal, though many of the cultivated forms have become partially or dumstorum sterile.
The genus Dioscorea is divided into a number of taxonomic sections; the important food yams are grouped in the following: There are some 60 species that have been used for food, but most are of little importance; the above with the exception of D. Origin and distribution The genus Dioscorea is considered to be among the most primitive of the Angiosperms and was present and well diversified in part of the southern world at the end of the Cretaceous period approximately 75 million years agoand the early spread appears to have been via an antarctic continent whose climate was totally different in early geological times.
The occurrence of Dioscorea spp. Wild yams and domesticated cultivars occur throughout the tropical and subtropical world, with one dwarf species D. West Africa is the most important cultivation zone, where yam is a major staple, producing about 93 per cent of the world’s edible yams, but the crop is also of considerable importance in parts of eastern Africa, the Pacific area including Japanthe Caribbean and tropical America.
An exception is D. Rainfall-although generally considered drought resistant, yams require adequate moisture throughout their growing period and there is a positive correlation between high and regular rainfall, vine growth and tuber yield.
For optimum yields adequate moisture between the 14th and 20th weeks of growth is of great importance. The major areas of production are centred where there is a sharply demarcated dry season of months and a rainfall of cm or more during the growing season. In parts of West Africa yams are grown where the rainfall is as low as 60 cm per year, but yields are very poor, while crops are also obtained where the annual rainfall reaches cm.
Soil-good drainage is essential and for optimum yields a deep well-drained sandy loam is required. On heavy, waterlogged soils the tubers are liable to rot, while on poor soils the weak root system is unable to obtain sufficient water or nutrients to produce reasonably-sized tubers.
Most yams are grown on land after it has been cleared from bush; fallow mulching is often practiced and FYM at the rate of Fertilisers are not widely used but there is a wide response to treatment, particularly to the application of phosphorus and potassium.
Application should be months after growth commences. The application of potash alone has given yield increases in Nigeria, and it is also reported to increase the storage life of the tubers, while chlorine in the fertiliser adversely affects the starch content. Altitude-most yams can be grown successfully at low or medium elevations and some, such as D.
Day-length-the majority of Dioscorea spp. Planting procedure Material-edible yams are normally propagated by the use of small tubers seed yamscuttings off the tubers, setts pre-sprouted tubers or pieces of tuberor bulbils. It is possible to use vine cuttings, but tuber production by this method is generally uneconomic. All types of vegetative planting material other than vine cuttings are commonly referred to as setts. The best planting material is the small whole tuber and species such as D.
Other species such as D. In general, tops are preferred and the larger the sets, the earlier and greater is the rate of germination. The weight of sett used varies from about 0. Sometimes the body of the yam is cut off and the head left in the soil to grow and produce seed yams for propagation; this practice is known as ‘topping’ or ‘milking’. Most yams have a definite period of dormancy, but this may be broken by the use of a chemical such as ethylene chlorhydrin, where production of out-of-season tubers is required.
A recent development has been the production in Barbados of virus-tested planting material, in which yams grown from virus-free meristem tip cultures are being multiplied in the field and, after inspection, distributed for planting.
Dioscorea dumetorum – Wikipedia
This material has been tested in a number of Dunetorum islands and has given approximately double the yield obtained when conventional seed yams are planted, and the operation is now commercial.
Method-yams are usually intercropped with maize and vegetables, such as cucurbits, pumpkins, peppers and okra, but mono-culture, normally on small plots, is increasing in certain areas of West Africa and the Caribbean. Three types of planting systems are practiced: The last method is the most widespread and the mounds can vary from about 50 cm high and perhaps twice as wide at the bottom, to nearly cm high and twice this width at the base.
In the smaller mounds one sett is normally planted and in the larger ones three or four, or even eight to ten setts. In general, larger mounds are preferred and the setts are planted in holes dug in the sides near the natural ground level. They are planted deeply to avoid drying out of the young shoots and for this reason the head of the sett is also placed dkoscorea.
Sometimes, instead of individual mounds, ridges are used and the setts are planted along the sides of the ridges. Planting on the flat is only practiced in areas such as river flood plains, where the soil is deep and soft. In this system, the setts are planted in holes just below the soil surface.
Support for the diosccorea vines is usually provided, most often dumetorun or trellises, or strings attached to horizontal ropes or trees, sometimes corn stalks left from an intercrop of maize, or even bushes: However, a few cultivars, notably dumetorim D. Recent work suggests that with close planting other species may also give satisfactory yields without support. Planting is normally by hand, but a mechanical planter is now being used in Barbados. For optimum yields yams must be kept free from weeds, at least for the first three months of growth, and the following herbicides have been used successfully: Time of planting-yams are not normally grown under irrigation and in areas where the rains last months planting normally takes place just before or cioscorea the beginning of the rains.
Where the rainy season is less than 8 months it discorea been found that early planting, up to 3 months before the rains, can give a 30 per cent increase in yield. Field spacing-a wide range of planting distances is used, depending upon the species, the soil type and the water table and whether intercropping is practiced; mounds are often irregularly spaced and planting distances ranging from 0.
Generally, the wider the spacing the lower the yield and common spacings are 1. Pests and diseases Weeds-can be serious competitors with yams. While hand-weeding is the most common practice, pre-emergence spraying with atrazine or ametryn will control weeds until the plants have sprouted; subsequently paraquat carefully applied with a shielded spray may be used. In due course the foliage should become thick enough to cover the ground and eliminate weeds, especially when the vines are unslaked.
Pests-yam beetles of several species are important, especially in Africa: These attack the tuber setts and may prevent sprouting. Dusting the plant setts with 2 per cent aldrin or 0. In the Caribbean, the yam weevil Palaeopus costicollis causes similar damage and control is as for the yam beetles. The termite, Amitermes evancifer, is occasionally a serious pest of yam tubers in Africa.
Potentials of Trifoliate Yam (Dioscorea dumetorum) in Noodles Production
Yam scale Aspidiella hartii attacks stored yams in Africa, Asia and the Pacific; in the Caribbean its principal damage is to young vines which may be destroyed completely. It is important to use scale-free diocsorea material; this, together with the dusting recommended above, should provide adequate control. Only clean and healthy material should be planted again the dusting treatment recommended for yam beetles should be usedand, if aerial parts of the plant are affected, spraying with malathion or malathion plus an oil emulsion eg Triona or Albolineum is recommended.
Several species of nematodes attack yams.
The yam nematode, Scutellonema bradys, is widely distributed in both Old and New World tropics and causes ‘dry rot’ of the tubers. Pratylenchus coffeae, causing rather similar lesions, has been reported to attack yams in Puerto Rico, Jamaica and the Solomon Islands, while the root knot nematodes, Meloidogyne spp. Chemical control has not proved entirely satisfactory, though D-D and dibromochloropropane have given some reduction in the infestation rate.
Absence of host plants and a fallow period are recommended, and care must be taken to avoid planting infected material. Diseases-these include anthracnose caused by Glomerella cingulatawhich produces black necrotic lesions on leaves and stems, and can kill the plant by attacking the terminal bud, and leaf spot, caused by various species of Cercospora, Colletotrichum, and Phyllosticta.
Control involves sanitation by removal of crop debris, and fungicide treatment: During storage of the tubers, severe losses are caused by rotting due to Botryodiplodia theobromae, Aspergillus spp. These rots may also affect the growing plant when the setts consist of cut pieces of tuber, but are controlled by simple measures such as the painting of the cut surfaces with limewash or Bordeaux mixture, or coating with wood ash.
Rotting during storage may be minimised by treating cut or bruised surfaces of the harvested tubers in the same manner. Virus diseases have been reported from the Caribbean and West Africa, but are probably world-wide. Most are of the mosaic type causing leaf mottling, and most are serious only when the infection occurs early and is severe, dumetoeum to stunting and sometimes causing the production of numerous basal shoots, giving the plant a bushy appearance. In the Lesser Antilles an internal brown spotting first observed in Barbados is associated with virus infection; the affected tubers develop hard brown nodules in the flesh, often surrounded by necrotic areas, and the foliage has not always easily discernible mosaic symptoms.
Yields of affected plants may be reduced by half. No vector has been identified for any of these viruses, but duetorum meristem culture technique and the production of virus-tested yams has been developed and carried through to the commercial scale in Barbados. Growth period Most edible yams normally reach maturity months after planting, diiscorea in certain species a first harvest may be obtained after 5 months.
The growth period usually comes to an end at, or shortly after, the end of the rainy season: Harvesting and handling At the start of the dry season yam plants normally die back and the tubers are ready for harvesting, though in most cases they may be left in the ground for several weeks as deterioration is usually not rapid.
In some species, eg D. Large yams are usually dug out by hand with wooden spades or digging sticks, or with forks-a laborious task since great care has to diosclrea taken to avoid damaging the tubers. Yam species which produce a number of small tubers can be harvested mechanically with a potato spinner, but recent work in the Caribbean has developed a mechanical harvester suitable for the large-tubered D.
Aerial tubers or bulbils are usually plucked by hand from the vine as required. Yam tubers, if unaffected by pests and diseases, may be stored until their natural period of dormancy is broken.
It has already been noted that many species may be stored by leaving them unharvested during part, at least, of the dry season. Normally, however, yams are harvested and stored. The tubers must be clean and undamaged, excessive temperatures must be avoided and good aeration provided. Some varieties will keep in good condition for about 6 months, though the tubers may lose per cent or more of their weight, and the storage life differs between different species or even cultivars.
Several methods of storage are used: In West Africa yam barns are common, consisting of a wooden vertical or nearly vertical framework to which the dummetorum are individually tied: These frames provide excellent ventilation and the tubers can be protected from termite attack and flooding.
In the Pacific Islands specially constructed thatched huts with a raised platform, on dumetourm the yams are stacked, are used.