Roots and tubers
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Item The Stimulation of Root Production in Cuttings by Synthetic Growth Promoting Substances(1938)The extraction of pure plant hormones from the plant during recent years, and their identification with certain chemicals that can be synthesized in the laboratory, has stimulated the attack on problems connected with the growth and rooting of the plant. The synthetic hormone had been found to be as effective as the natural product. While the production of certain growth reactions in the stem of a plant appeals only to the more academic research worker. the stimulation of rooting has an immediate practical appeal to the planter. By the application of these chemical substances to plant cuttings it ought to be possible to root them more quickly and easily than by any known horticultural practice. Workers in the Boyce Thompson Institute and elsewhere showed that plant tissues responded readily to these chemicals and could be easily stimulated to grow on cuttings of many plants.Item Studies of the Mosaic Diseases of Cassava(1938) Nichols, R.F.W.; Storey, H.H.; East African Agricultural Research StationThe symptoms of mosaic disease in cassava, although generally typical of the mosaic group, show wide variations, due in part to the varietal reaction of the plant, to its stage of development and to the environment. The most important cause of variations however is differences in the strains of the virus, of which we have recognized, through the study of symptoms, two groups of severe and mild strains. The viruses are transmitted across a graft, but we have failed to obtain mechanical transmission by needle or hypodermic injection. A Bemisia sp. can transmit both groups of strains. It can inoculate the plant only through immature leaves, less than about one-quarter of their full length. The virus so inoculated does not pass out of the leaf until about 8 days have elapsed. On the basis of this knowledge a convenient and reliable single-leaf cage technique has been developed. After the virus has entered the stem it passes rapidly to the base of this stem, but odp slowly into side branches from it or into other stems arising from the same original cutting. Infection of a plant with a mild strain of virus failed entirely to confer immunity from infection by severe strains introduced by grafting. If the severe strains were inoculated by insects there was an indication of some conferred resistance but insufficient to make the procedure practically useful in control.Item Derris or Tuba Root(Taylor & Francis, 1940) Worsley, R.R.; Production in East Africa; A.R.C.S., AmaniActive interest has been shown for some time past in the trials being carried out with Derris elliptica at the East African Agricultural Research Station, ,Amani, where a particularly toxic strain of this Malayan fish-poison and insecticide was introduced, via Kew, in 1928. It is now possible to give the yield and cost of production figures for the first normal crop of derris root harvested at Amani, the bulk of previous crops having been used for experimental purposes, or cut as planting material, for which there is a considerable demand in East Africa at present.Item Environment and the Growth of the Potato (Solanum Tuberosum) in Tropical East Africa(1943) Glover, J.; East African Agricultural Research Institute AmaniThe potato S. Tuberosum, which was possibly introduced into east tropical Africa as a subsidiary food crop for Europeans, is now for many Africans an appreciated source of food and others a cash crop of importance. Though a successful introduction, the yields of tubers have generally been lower than those obtained in temperate zones. Some have suggested that this might be due to the detrimental effect of short daylength and high air and soil temperatures. Moreau [1], in a survey of the climatic background of the commercial potato-growing areas in E. Africa, mainly in the cooler zones above 4,000 ft. on the mountain, masses, concluded that 'given good husbandry, excellent crops of S. Tuberosum can be raised in parts of tropical Mrica, even though air and soil temperatures seem unfavorably high. The short days seem to be of no practical importance.' He stresses, however, that his data are scanty.Item The Yield and Maturity Period of Potatoes (Solanum Tuberosum) at Low Latitudes(1943) Moreau, R.E.; East African Agricultural Research Institute AmaniVery definite opinions have been expressed that the potatoes of commerce are long-day plants. For example, Bald [I] writes that commercial potatoes 'produce a full crop where they receive more than 13 hours of full daylight each day. Many will produce 50 to 75 percent. Yield under short-day conditions, but never their maximum crop.' Even more emphatic statements have been made by Driver [2]: 'It has always been difficult, if not impossible, to grow potatoes in tropical countries. This is because potatoes have been bred for and become adapted to the light conditions of temperate regions and form tubers only when the daylight period reaches a certain minimum. In tropical regions, the daylight period does not exceed twelve hours, and this is insufficient to initiate tuber development.' Because short day-length is one invincible circumstance of tropical agriculture, and because the question is fundamental to a policy of potato selection for the tropics, the evidence I. for such statements as the foregoing needs dose examination. It is of course obvious at the outset to anyone aware of the East African potato-growing industry that the last part of Driver's statement does not apply to that country.Item 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 The Cutting and Treatment of Seed Potatoes(1945) Nattrass, R.M.During the present war the need for economy in material and transport has focused attention on the use of cut sets for potato seed.Item Onion Cultivation on Kilimanjaro(1947) Swynnerton,R. J. M; TanganyikaVigorous growth must be maintained in the onions and this can be brought about by regular watering, weeding and the application of sulphate of ammonia. Onion beds should be flooded at regular intervals in dry spells during the rains and thereafter until harvest and the soil should never be allowed to dry out.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 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.Item Potato Clonal Variation with Respect to the Relation between Fruit Set and Tuber Yield(1975) Kidane, M.; Haile, M.; Peloquin, S.J.; Department of Horticulture, University of WisconsinAlthough fruiting may have some physiolo-gical influence on vegetative growth or yield in some crops, there are few and conflicting observations concerning the relation between fruiting and tuber yield in potatoes. Bartholdi [2] studied the influence of flowering and fruit-ing upon vegetative growth and tuber yield in four selected potato cultivars (Russet Rural, Irish Cobbler, Minn 5-10-1-4-2, and Minn 5-2-4-2). He found that both flowering and fruiting caused significant reduction in vegeta-tive growth and tuber yield in all the cultivars he used. Possible effects of fruiting on tuber yield in some cultivars of andigena (Solanum andigenum) have also been observed by de la Puente (personal communication) in Peru. However, other results indicate that fruiting does not have any significant effect on tuber yield in potato. Working in reciprocal crosses between andigena and tuberosum clones in Ithaca, Cornell, Cubelios (personal communi-cation) found no effect of fruiting on tuber yield. Newman and Leonian [7] and Young [11] working with the cultivar Lookout Moun-tain found no definite correlation between seed production and yield of tubers. Stout and Clark [9] also found no difference in tuber yields between flowering and non-flowering plants of potato. Results obtained by Arthur et al. [1] also indicate that flowering does not have any effect on tuber production. In fact, they secured some of the best tuber yields from plants that bloomed profusely. An old idea that non-fruiting is due to tuber development was refuted by Werner [10]. He found no evidence that there is any relation between the extent of flower production and tuber production. He explained that elongation of the potato plant is genetically limited to a fairly definite number of nodes. As a result of differentiation of these nodes, the primordium of an inflorescence is initiated, but whether it develops entirely, part way, or hardly at all, is dependent upon the physiological conditions within the plant. According to Werner [10], this internal condition is a result of the external environment. The objective of this study was to evaluate the effect of fruiting on tuber yield.Item Potato growing in Kenya improvement through disease control, varietal selection and provision of healthy stock(Kenya Agricultural Research Institute, 1976) Todd, J.M.; Kenya Agricultural Research InstitutePotatoes are thought to have been introduced to East Africa by the early European settlers.How this was done and with what rate of success,how varieties suited to tropical upland conditions came to be selected,and how the crops was taken up by African cultivators are all parts of a story yet to be compiled from whatever primary sources remain.Item Storage and Processing Characteristics of Three Kenyan Potato Varieties(Jackson Ntongai Kabira, 1983) Kabira, J.N.The studies presented here were conducted to determine the storage and processing characteristics of three established Kenyan varieties of potato (Solanum tuberosum). They included the red-skinned Kerr's Pink and Desiree, and the white-skinned Kenya Baraka varieties, and were grown under similar cultural conditions at the National Potato Research Station (NPRS), Tigoni. Tests were carried out over a period of three growing seasons, starting in 1980/81.Item National Agricultural Research Project Quarterly Report of Activities and Progress July - September 1994(National Potato Research Centre, 1994) National Potato Research Centrenel - Dr. and Mrs. Filmore Bender departed Kenya July 30 at the end of his two-year tour of duty as long-term Research Management Advisor and Chief of Party. The Research The management Advisor position was not filled and Dr. Robert Hudgens is serving as MIAC-MU Team Leader in addition to his duties as Systems Agronomist.Item National Agricultural Research Project Quarterly Report of Activities and Progress July - September, 1995(National Potato Research Centre, 1995) National Potato Research CentrePersonnel - Dr. R. S. Malik was on home leave in the U.S. during portions of July and August. Vehicles - Transport for Technical Advisors is satisfactory. Due to reductions in staffing, two Isuzu Troopers were transferred from MIAC to KARI. Finance and Accounting - On July 20, the annual work plan and budget for the period July 1, 1995 - June 30, 1996 was approved by USAID and PIL 33 issued. The annual increment of funding to the KARI MIAC Contract for the period is $2.6 million. This is about 900,000 less than was planned for when NARP II was approved.Item Review of Kenyan Agricultural Research Vol. 22 Root and Tuber Crops(Kenya Agricultural Research Institute, 1997) Mailu, A.M.; Kenya Agricultural Research InstituteThese reviews have been produced as part of the Kenya Agricultural Research Database Project which was funded by the Netherlands government over the years 1992 to 1996. The aim of the project was to document all investigations and research related to agriculture in Kenya undertaken since the end of the last century, especially those items which had not been published. The computerized database now contains around 40,000 records, most containing abstracts or summaries, full bibliographic details, and information about where the documents can be found. We are conscious, however, that many items have not yet been included, especially the earlier material and many consultancy reports produced by the foreign and international donor, development, and research organisations. Specialists who read the reviews may be aware of important topics which have been omitted by the reviewer. If this is the case, we would ask that both the reviewer and KARl's Library and Information Services be informed so that the topic can be included in future revisions. Constant up-date will be required as new research information becomes available with the National Agricultural Research System in Kenya.Item Agri-business Development Support Project (ADSP) July-Sept 2001(Kenya Agricultural Research Institute, 2001) Kenya Agricultural Research InstituteThe degeneration trials were harvested on the 15th, 16th, and 17th of August in Ngecha, Murengeti, and Tigoni Centre respectively. The treatments consisted of dressing with a systemic insecticide, foliar spraying with insecticides, and untreated and unsprayed plots. In addition, a trial to compare the yield difference between first, second, and third-generation seed tubers was harvested at Tigoni on 24th August. Two varieties, Tigoni and Asante were used. The experimental design was an RCBD replicated three times. The yields were 31.6, 28.0, and 18.9 tlha for the first, second, and third-generation seed tubers respectively. ii) Harvesting of the trial on early and medium maturing varieties was done in Kakamega, (Kabras East Division) and Laikipia (Ngecha Division) on 4th and 6th September respectively. Results showed that the best performer in both.Item KARI Potato Research Priorities in Kenya: KARI impact assessment series(Kenya Agricultural Research Institute, 2001) Kenya Agricultural Research InstitutePotatoes are a high priority food crop in Kenya given that they occupy the 2nd place to maize as food energy source. The national potato research programme, continues to face a serious problem of scarce resources. As a result, the programme is under pressure to demonstrate clearly the benefits the taxpayers can expect from the resources that are availed and utilised in support of agricultural research.Item Guidelines for Production of Healthy Seed Potatoes In East And Central Africa(Kenya Agricultural Research Institute, 2006) Kabira, J. N.; Wakahiu, M.; Wagoire, W.; Gildemacher, P.; Lemaga, B.; Kenya Agricultural Research InstitutePotato is an important food and cash crop in East and Central Africa. It plays an important role in national food and nutrition security, poverty alleviation, and income generation and provides employment in production to consumption continuum. Potatoes mature in 3-4 months and can yield up to 40 t ha-1 • Most farmers obtain less than 10 t ha·1, mainly because of poor growing practices, low use of inputs and poor control of insect pests and diseases. Supply of good quality planting materials of improved varieties and timely availability can boost production of potatoes. Most farmers save and-plant seed from their own fields, or buy small tubers from neighbours or local markets. These practices allow diseases to build up resulting in low yields even when following recommended fertilisers and fungicides rates. Farmers should renew their seed stocks from clean sources such as research stations at least every 2-3 years, and then manage this seed carefully to minimise build-up of diseases and pests. This manual explains how to produce disease-free seed potatoes to support over one million ware potato growers in the region whose standard of cultivation requires to be upgraded.
