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Table des matières
- Précédente - Suivante
Cassava what are the research priorities for improving
production in relation with processing and marketing?
J. P. Raffaillac
National cassava crops related to populations show the special importance of this staple foodstuff in the African countries that account for 50 percent of world production. Research on cassava production should take the entire industry into account in order to incorporate certain features of production objectives that may vary according to whether cassava is a food crop (the most common case) or a cash crop for use as animal feed or in industry. The two fold issue in the years to come consists of 'producing more' and 'obtaining a food-stuff of competitive quality' and researchers in agronomy should examine first of all the increase in production in the face of a decrease in soil fertility, whereas fertilisation (mainly potassic) is often not particularly compatible with processing techniques and end-product quality. A few examples drawn from agronomic research results illustrate this interdependence between factors of production and the processing or marketing of cassava. p. 20
The characterisation and evaluation of root and tuber
plants and plantains
V. Lebot
The cult vat on of root and tuber crops (Colocasia, Dioscorea, Ipomoea, Manihot, Xanthosoma spp., etc.) and plantains (Musa spp.) is based mainly on vegetative multiplication. As a result, most cultivars do not benefit from the genetic recombinations resulting from sexuality. Their adaptive potentials are thus practically nil in comparison with species with sexual multiplication. Genetic resources are therefore extremely valuable and must be carefully conserved and protected. The characterisation and evaluation of cultivars are fundamental stages in the process of improving and developing these crops. A common methodology can be used for these species; it proceeds by successive stages In the identification of morphotypes, zymotypes, chemotypes, cytotypes and genotypes It is aimed essentially at identifying agreements or revealing discordance are used to account for the structure of variability. The results obtained for yam, taro, plantain and kava are described succinctly and agree to show that, given the difficulties in the genetic improvement of these plants, it is urgent to characterise and evaluate existing genetic resources. Potentially interesting cultivars certainly deserve to be selected and multiplied. The author considers that the method described is the only one that enables rapid progress in this field.
Yam production in a Bariba village in northern Benin
R. Dumont
A survey was performed in sixteen farms, twelve of which practised tillage using animal traction. In all cases 95 percent of yam cultivation was based on the D. cayensi-rotundata complex and, within this, four early varieties with two harvests and three late varieties with a single harvest account for the greater proportion of production. Cultural constraints and the solution to the seed yam problem vary according to the varietal factor. Animal traction did not cause a decrease in the importance of yam in farming and cotton growing seems to draw benefit from yam.
Identification of the factors enhancing the occurrence of
an unusual stem and root rot in cassava in Togo. Cultural
practices are accused
B. Boher, A. Ptcholo y B. Tchabana
A plant pathology survey confirmed the economic importance of a root and stem rot of cassava in the Danyi plateau zone in south-west Togo. The causal agent was characterised as the fungus Lasiodiplodia theobromae. This species has a large host spectrum and, although it had previously been observed on cassava, it has never been considered to be responsible for damage on a scale observe in plants in this part of Togo. Studies under controlled conditions and in the field showed that incidence of the disease was related to the susceptibility of the varieties grown on the plateau and to the practice of keeping cuttings for a long time, thus stimulating the production of large quantities of inoculum. Most of the varieties tested in the Togolese national cassava collection were found to be resistant to this rot. These results make it possible to envisage the very rapid reduction of incidence of the disease by combining the improvement of cultural practices and the use of resistant varieties suited to the agro-ecosystem of Danyi plateau.
Control of the cassava mealybug in Africa
P. A. Colatayud, B. Le Rü
Cassava, a staple foodstuffs for nearly 500 million people, has suffered recently from attack by the cassava mealybug, Phenacoccus manihoti. This oligophagous pest reproduces by thelytokous parthenogenesis and feeds on the elaborate sap of cassava. Biological and varietal control, and especially the introduction into Africa of an endoparasite Epidinocarses lopzi (Hymenoptera), make it possible to reduce damage 'in some cases.
Characterisation of the cassava sour starch agroindustry in
The department of Cauca Colombia
V. Gottret, G. Henry, D. Dufour
The small-scale sour starch agroindustry of the Cauca valley comprises the largest concentration of sour starch producers, producing the highest output of the product In Colombia. The immediate objectives of the study described in this paper are to assess the industry and to characterize Its main technical and socio-economic aspects. A further aim is to assess technology adoption and impact and, base on this, to develop a future research and development agenda involving all levels of the market channel.
Levels of technology are closely correlated to plant size and product output, and to distance from the major highway. The smaller plants further from the highway and higher in the mountains, manifested the lowest levels of technology utilization, output, efficiency, credit use and technical assistance. Of five designated technology levels observed in the plants, the two lowest levels showed negative returns to investment. The industry in general is dynamic from a technology-adoption point of view, as smaller low-technology plants are replaced by larger high-technology units.
Preliminary study for the design of equipment for the
extraction of starch from Canna edulis in Colombia
S. Degrés. H. Garcia Bernal.
The functional properties of Canna edulis starch enable uses that are particularly appreciated by consumers (biscuits, fresh pasta, etc.), but the arduousness of extraction limits production. A structural study of techniques led to identification of the unsatisfactory features of starch extraction in Colombia and the defining of equipment urgently required by farmer-producers.
The importance use of roots. tubers and cooking bananas in
the human diet in the world
S. Trèche
Roots, tubers and cooking bananas (RTB) form only 5.4% of total food energy sources world-wide but, as they are very unevenly distributed, they can be of considerable importance in some parts of the world. Three species (potato, cassava and sweet potato) account for 86% of the food energy available from RTB, but other species (plantain, yam and minor species) may also be the main food energy source for certain populations. The countries in which the quantities of RTB available as food for humans are large enough to form a substantial economic issue are rarely the countries in which they are the main energy source in diets. However, the guidelines to be given to research on the use of RTB should not play down the studies required for adapting processing and marketing channels to the changes in the way of Re and food preferences in countries where they form essential resources for food security.