Roots and tubers
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Browsing Roots and tubers by Subject "Cassava"
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Item Breeding Cassava for Virus Resitance(1947) Nicholas, R.F.W.; AmaniSo long as cassava (Manihot utilissima Pohl.) continues to rank as a staple food for a large proportion of the indigenous population of East Africa, the improvement of the crop must figure in the agricultural economics of the country. The comparative freedom of the crop from pests, and its drought resisting qualities, render it of particular value as an "insurance policy" against famine when it is less afflicted by drought and locusts than other crops. That it is, however, subject 'to great reduction in yield, due to infection by the mosaic virus, has been recognized for many years. In Zanzibar, Briant and Johns (1940), have shown that the loss in a non-tolerant variety, propagated from diseased cuttings, may be as high as 95 per cent. Experimental work at Amani demonstrated that this virus was transmitted by a white fly, Bemisia sp. (Storey and Nichols, 1938); field experiments showed that natural infection was mainly seasonal and in certain areas extremely high. These experiments also demonstrated that some varieties are less prone to infection than others. This disease occurs throughout East AfricaItem Long-Term and Short-Term Cassavas(July, 1944) Jameson, J. D.; Oates, C.; Muir, J. C.; Allnutt, T. B.; Nichols, R. F. W.; Department of Agriculture Kawanda, Kampala ,Uganda, Department of Agriculture Kenya, Department of Agriculture Tanganyika Territory, Department of Agriculture Zanzibar, Cassava Investigation of AmaniIt has been suggested here that correspondents to your journal might be able to throw light on a curious disparity in the practice of cassava cultivation between the various East African territories. In those parts of Uganda where cassava is an important reserve against famine it is the custom to plant up the greater part of the acreage with so-called "long-term" varieties. This description is perhaps not sufficiently definitive, but by it is meant varieties which stay in the ground for two or more years without appreciable deterioration to the tubers. The advantages of this course are presumablyItem Notes on Cassava Preparation in North Kavirondo and Samia(1944/1945) Anderson, G.W.; Department of Agriculture, KenyaInnumerable types of cassava are grown in the Samia and North Kavirondo areas, but of these, six are most generally popular mainly for the reason that they are, with one exception, early to medium in maturity and at the same time" sweet". That is to say they have not the strong bitter flavour of later maturing types—a bitterness which necessitates a longer method of preparation and which prevents the roots being used until they are almost fully developed. Of these popular varieties the earliest is Mbironyango, a variety introduced to the Bantus from Jaluo country, which matures in about eight months but which can be lifted and used in four. Next in order of maturity come four varieties which mature in about a year, but they also can be lifted early—anything from six months onwards. These are, Miti juma and Dodo, two varieties believed to have come in the first instance from the Uganda side of the border; Khasimbctsio and Namugassa, two locally named types which appear to have been in cultivation for several generations. Miti juma and Khasimbasio are two of the most common. The former for the reason that, although an early cassava, the roots can remain in the ground after reaching maturity for a period of up to three or four years without deterioration—a very popular characteristic in areas where the people are not prone to overexertion. Khasimbasio is popular for the reason that it yields quite heavily and, according to general belief amongst native growers, does not suffer to the same extent as other varieties from mosaic diseases.Item Strong Sweet Potatoes in Zanzibar(1945) Tidbury G. E.Unlike cassava, some varieties of which can be safely left in the ground for several months after the crop is ripe, sweet potatoes must be dug when the tubers are fully grown or rotting and insect infestation will rapidly destroy the crop. A further disadvantage of this crop in Zanzibar is that during the hot season, November to February, tuber formation does not take place even if the vines survive the hot, dry weather. There is thus a great shortage of sweet potatoes during the first half of each year. Some attention has, therefore, been given in this Protectorate to finding a simple method whereby the sweet potato can be stored for several months.Item Variation in Pollen and Ovule Fertility in Varieties of Cassava, and the Effect of Interspecific Crossing on Fertility(1963) Jennings, D.L.Records of the set of seeds obtained from intraspecific cassava crosses, from interspecific crosses between other Manihot species and cassava, and from backcrosses to cassava of three generations of interspecific hybrids are used to assess the variation in pollen and ovule fertility. It is concluded that the capacity of cassava varieties to set seeds has been reduced since they have evolved from non-tuberous wild forms and have been propagated vegetatively. Fertility was found to be very variable, and the capacity of the pollen of a variety to promote seed-set was not related to the fertility of the variety's female flowers. This situation would be expected if reduction in the fertilities of the two sexes were caused either by loss of balance in the genes controlling the functioning of the male gametophyte, or by unbalance of those concerned with the functioning of the female gametophyte or the tissues which nurture the embryo. Additional causes of sterility, probably including meiotic irregularities, appeared to operate in the Fl interspecific hybrids, but such factors were probably not important after the first backcross generation. Manihot melanobasis, a wild form which is normally propagated by seed and whose relationship to cassava should be regarded as subspecific, contributed factors which enhanced the fertility of its hybrids with cassava. This form could be used in cassava breeding as a "donor" of seed fertility, but use could also be made of some existing varieties which still possess a moderately high capacity to set seed. It is desirable to select these as one parent when making difficult crosses.
