Conference Documents: Recent submissions

Now showing items 241-260 of 726

    • Root crops for food security in subSaharan Africa 

      Hahn, S.K. (1994)
      Food production in sub-Saharan Africa has not kept up with population growth and the increasing pressure of population on the land has decreased the resource base and caused the farming environment to become vulnerable to unpredictable climatic changes. Thus, there will be more acute food deficits in the future unless the productivity of food crops, including root crops, is increased by at least 3% per annum. Root crops are capable of efficient production of low cost calories under marginal soil ...

    • Screening cassava cultivars for resistance to the cassava anthracnose disease (CAD) 

      Ikotun, T.; Hahn, S.K. (1994)
      Forty-seven cultivars of cassava in IITA's trials were screened for their reaction to infection by Colletotrichum gloesporiodes f. sp. manihotis in the field. The following parameters were observed: (a) distance of first canker from the soil, (b) total number of cankers per plant, (c) size of cankers on young stem and shoot, (d) size of canker on material stem, and (e) size of cankers mature stems. Cultivars Isunikankiyan, 81/00110, 82/00142, and 84751 had cankers developing at the lowest level ...

    • Productivity of cassava intercrop as influenced by cassava variety and time of introducingrice into cassava 

      Jalloh, A.; Dahniya, Mohamed T.; Ezumah, H.C. (1994)
      The study was carried out to determine the most appropriate time of introducing rice into cassava with the aim of improving the total productivity of the intercrop. The rice variety Rok 16 was introduced into cassava at four different times—planted at the same time with cassava, and then at 2, 4, and 6 wk after cassava. The cassava varieties used were 80/40, an improved clone, and the local Cocoa. Both variety and time of introducing rice into cassava affected tuberous root yield of cassava. Variety ...

    • Cyanide and cassava breeding 

      Mahungu, N.; Hahn, S.K.; Chheda, H.R. (1994)
      Cassava (Manihot esculenta Crantz) contains cyanogenic glucosides which lead to the release of hydrogen cyanide (HCN) after hydrolysis. A study carried out using six cassava populations revealed that the broad-sense heritability for HCN was relatively low at 34.58 and 32.18 percent in roots and leaves respectively. Relationships between HCN in roots and leaves and twenty other cassava characters were examined. None of the characters was found significantly related to cyanide content in either leaf ...

    • Can biological control resolve the larger grai borer crisis? 

      Markham, R.; Borgemeister, C.; Meikle, W. (1994)
      The accidental introduction of the lager grain borer, Prostephanus truncates, in the early 1980s result in destructive pest outbreaks in small-farm maize stores in both East and West Africa. Studies comparing the situation in rural maize stores in Costa Rica (in the pest's neotropical area of origin) with that control of natural enemies in Central America and that classical biological control of the pest in Africa might be feasible. The search for appropriate natural enemies is reviewed, with ...

    • The cassava biotechnology network and African agriculture research and development programmes 

      Thro, A.M.; Roca, W.; Asiedu, Robert (1994)
      In modern biological research, cassava has been an orphan crop, because most advances have taken place in developed countries where cassava is not grown. In order for cassava to profit from biotechnology, efforts around the world must be pooled, integrating developing countries into the process. The Cassava Biotechnology Network fosters developments which are environmentally acceptable and promote the well being of small-scale farmers within sustainable cassava production systems. The network will ...

    • Interspecific hybridization in the genus Manihot progress and prospects 

      Asiedu, Robert; Hahn, S.K.; Bai, K.V.; Dixon, A. (1994)
      Most cassava (Manihot esculenta Crantz) improvement programs depend on the range of variability available within the cultigen for breeding varieties adapted to target environments. Efforts by some programs to introduce additional variability from wild Manihot species into cassava have led to improved diseases and pest resistance as well as higher ploidy levels. They have also provided insights into the evolution of the genus. Much remains to be investigated. This paper reviews the progress from ...

    • Genotype environment interaction studies with cassava 

      Otoo, J.; Dixon, A.; Asiedu, Robert; Okeke, J.E.; Maroya, N.; Tougnon, K.; Okoli, O.; Tetteh, J.P.; Hahn, S.K. (1994)
      Multilocational trials were conducted in several agroecological zones in West Africa to assess the magnitude of genotype x environment (G x E) interaction and to identify stable varieties which could be used in breeding programs in the region. The reaction of the varieties to major cassava diseases and pests was also assessed. Ten clones, including 7 IITA improved cassava clones, were used in the study. Results from 22 trials conducted in a randomized complete block design revealed a highly ...

    • Production and distribution of virusfree yam (Dioscorea rotundata Poir.) 

      Ng, S.Y.C. (1994)
      The international distribution of vegetative plant parts is restricted by the risks of introducing diseases and pests to non-infected areas. Methods used at IITA to produce and distribute virus-free yams to requesting national programs and collaborators are described. The selected yam clones are cleaned from virus disease infection through thermotherapy and meristem culture. The regenerated plants are virus indexed. The negatively indexed plants are then multiplied in vitro for international ...

    • Genotypic stability and adaptability: analytical methods and implications for cassava breeding for low input agriculture 

      Dixon, A.; Asiedu, Robert; Hahn, S.K. (1994)
      Stable as well as adaptable genotypes of high-yielding cassava cultivars, should be developed and made available to farmers, to ensure increases in cassava production in a target region or country in sub-Saharan Africa. As farmer-to-farmer contact is the primary means of diffusion of new crop varieties, improved cassava cultivars should satisfy farmers' needs for a stable yield from year to year, yet be adaptable to the range of growing conditions that may exist across the targeted area of diffusion. ...

    • Distribution and disease recovery of African cassava mosaic virus (ACMV) in stems of resistance and susceptible cassava 

      Njock, T.E.; Atiri, G.; Thottappilly, G.; Hahn, S.K. (1994)
      The base section of the ACMV-susceptible clone 60506 recorded the highest disease incidence and severity relative to all other sections of the moderately resistant clone TMS 4(2)1425 and the resistant clone TMS 30001. However, in all clones, the base section recorded higher disease than either the top or middle sections. The highest frequency of diseased nodes was recorded from the base section of clone 60506. This frequency dropped consistently from the base, through the middle, to the top sections ...

    • The effect of different agroecological zones and plant age on the cyanogenic potential of six cassava clones 

      Githunguri, C.M.; Ekanayake, I.J.; Chweya, J.A.; Dixon, Alfred G.O.; Imungi, J. (1998)
      The effects of plant age on the cyanogenic potential (CNP) of leaves (CNP-L) and storage roots (CNP-R) of selected cassava clones, TMS 30001, TMS 4(2)1425, TME1, TME2,Isunikankiyanand Dakata Wariya were studied in two agroecological zones in West Africa. The two zones were represented by Kano in the Sudan Savanna zone with a unimodal annual rainfall averaging 844 mm and Ibadan in the forest-savanna transition zone with a bimodal rainfall averaging 1253mm per year. Plants were sampled periodically ...

    • Deleterious influence of water logging on potato in warm climates 

      Ekanayake, I.J. (1994)
      Water logging is a potential abiotic stress problem in the warm tropical potato growing areas, particularly in the lowland rice-based cropping systems. A field experiment was conducted in San Ramon, Peru during the rainy season to evaluate the effects of water logging on 12 clones (8 lowland tropical adapted clones and 4 highland adapted clones). A single week-long flooding period during the tuberization stage was sufficient to significantly reduce the tuber productivity of most clones. The flood ...

    • Postharvest technology and commodity marketing 

      Ferris, R.S.B. (1998)

    • Attributes of cassava varieties desired by farmers in subSaharan Africa 

      Nweke, F.; Dixon, A.; Asiedu, Robert; Folayan, S.A. (1994)
      Manihot esculenta.This paper which is based on information collected as part of Collaborative Study of Cassava in Africa (COSCA) provides information on cassava genotypes cultivated in sub-Saharan Africa. It shows that there is a high degree of turnover in the cassava genotypes cultivated. Farmers abandon the cultivation of genotypes which do not meet their need, they introduce better genotypes into their cropping systems whenever such are available to them. The attributes which the farmers desire ...

    • Improved cassava for inland valley agroecosystems 

      Ekanayake, I.J.; Dixon, A.; Asiedu, Robert; Izac, A.M. (1994)
      A substantial impact on Africa agriculture can be made through research on crop improvement for the extensive inland valley agro-ecosystems (IVS) extending from the humid forest to the savanna zones in sub saharan Africa. Systematic surveys of farmers have shown that cassava is a favoured upland crop for the IVS. Screening of cassava for IVS adaptation in the sub Saharan Africa is a continued activity at IITA. Preliminary results indicate that elite clones TMS 85/00025 (15.9t/ha), TMS 63397 (13.3 ...

    • Importance of cassava processing for production in subSaharan Africa 

      Nweke, F.I.; Bokanga, M. (1994)
      This paper is based on information collected from about 600 villages in the ten largest cassava-producing countries within the framework of the Collaborative Study of Cassava in Africa (COSCA). The objective of the paper is to show that growth in cassava production in the region will depend more on improvement in processing technology than on breeding for low cyanogenic potential. The paper shows that in the region, cassava is produced for sale. Most of the cassava produced is processed to improve ...

    • Cassava production trends in Africa 

      Nweke, F.; Polson, R.; Strauss, J. (1994)
      This paper which is based on primary information collected over a wide area in sub-Saharan Africa shows that cassava production is expanding in the region. The expansion is in response to demographic and market pressures as well as to periodic famine caused by drought, plant pests and disease or by civil disturbances. In addition, adoption of improved processing techniques is also aiding the expansion in cassava production.

    • An agroecologically oriented introduction of cassava germplasm from Latin America into Africa 

      Porto, M.C.; Asiedu, Robert; Dixon, A.; Hahn, S.K. (1994)
      An agroecologically-based germplasm enhancement strategy to further broaden the genetic base of cassava in selected ecologies of Africa was initiated by CIAT and IITA in 1990. Crosses are being made at CIAT, in Colombia, using parents adapted to four different agroecologies of South America with homologues in Africa. Selection of parents is made on the basis of resistance to pests and specific quality traits such as low cyanide content, yellow root flesh, and mealiness. Resistance to ACMD is being ...

    • Technical performance of a root crop chipping machine 

      Jeon, Y.W.; Halos, L.S. (1994)
      Reducing the size of tubers to be processed into a food product which requires fermentation and drying has been recognized as an effective method of reducing processing time and improving the product quality. A root crop chipping machine was developed and tested. The manually operated machine has a capacity of 68 kg h-1 for unsoaked tuber and over 100 kg h-1 for soaked tubers. The power driven unit has a capacity of about 1 000 kg h-1 with minimum amount of substandard (or fine) chips. The recommended ...