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V. 1 Current Research

Since cassava is a small farmers' crop, cultivated in tropical zones of the developing world, it is not particularly attractive to private sector researchers, who usually concentrate on those products that have a potential for large scale commercial application, distribution and marketing. However, because of Its high starch production potential, drought resistance and adaptability to different growing environments, cassava has been of particular interest to the public research network.

This chapter gives an overview of the main developments in biotechnology related to cassava and discusses their impact on world cassava trade. The technological information used is based on published patents but is also derived from the public sector network. Data on the public sector research was obtained through materials published by the Cassava Biotechnology Network24 and through a search of the web, centred particularly on the International Centre for Tropical Agriculture (Cali, Colombia) and the International Institute for Tropical Agriculture (Ibadan, Nigeria), which play major roles in the Cassava Biotechnology Network. Data on private sector research was obtained primarily from intellectual property filings, taking into account the likelihood that research (and patent filings) affecting cassava might arise as a by-product of research on potatoes, which are of greater commercial interest.

Cassava, like potato, is mostly propagated vegetatively by planting a piece of the stalk, which then grows into a new plant. This characteristic has important implications since, in the absence of sexual crossing, the new plant will be genetically identical to its “parent”. This vegetative propagation characteristic makes it harder to achieve rapid dissemination of specific materials, for each plant provides enough planting material for only about ten plants25. For this reason, an important breakthrough historically has been the development of tissue culture propagation of cassava. This technology presents several important benefits. One is the possibility of producing virus-free materials: by analysis of individual cells, those which have no virus particles can be picked out and used as the basis for regenerating a virus-free plant. Another is the possibility of producing large quantities of high quality planting material, because, when a good clone is identified, it can be multiplied into a large number of plants through tissue culture. If the cost of this technology can be kept adequately low, this may be the most efficient way to produce a variety of specific cultivars of a good quality and in sufficient quantity for distribution to farmers.

24These included the proceedings of the First, Second, and Third International Scientific Meetings of the Cassava Biotechnology Network. Those for the first two meetings in 1992 and 1994 were published by C1AT. That for the third meeting in 1996 was published as Volume 2, Numbers 1 &2, of the African Journal of Root and Tuber Crops, May 1997, and is cited here as CBNISM 3.

25A.M. Thro et al, Contributions of in vitro biology to cassava improvement, African Crop Sci. J.6:303 315 (1998).

Genetic modification through a transfer of specific genes permits the alteration or introduction of new characteristics to the plant in a more precise manner than with traditional breeding methods. However, to allow the potential of the genetic manipulation to be realized, techniques to regenerate the whole plant from the genetically modified cells are required. Currently, only the use of organized tissues, such as somatic embryos26, permits the full regeneration of cassava. Methods to modify the plant genetically include the bombardment of these tissue cells with DNA-coated particles, their penetration by the Agro-bacterium, or a combination of both27. Finally, it should be noted that genomic information is extremely important in contemporary biotechnology, and a genetic map is being developed for cassava in the public sector on a global basis.

i. Producer-oriented Biotechnology

There is substantial effort going into the improvement of cassava cultivars. One line of research, much of which is in the public sector and oriented toward the needs of the small farmer, seeks essentially to improve yields and especially by reducing the susceptibility of the plant to disease. Cassava is naturally relatively tolerant of poor soil and climate conditions, and its leaves drop near the plant, providing a form of fertilization and weed suppression. These are among the reasons why it is so widely grown and serves as a form of security crop for subsistence farmers. The public sector research has achieved important results, more than tripling potential yields to 20–30 tons per hectare and finding traditional breeding solutions to two major diseases, bacterial blight and mosaic disease. The research includes work of those of the global international agricultural research community28 and those of national institutes in Brazil29, India, and Thailand30.

26 Embryos derived by tissue culture from non-sexual tissues.

27CBNISM 3 at 163 195; Thro et al, (International Centre for Tropical Agriculture), “Biotechnology and Small scale Cassava Farmers,” Biotechnology and Development Monitor, No, 21 (Dec. 1994); Fauquet et al, U.K. Patent 9,609,368, ORSTOM & Scripps Research Institute, Genetically transformed cassava cells and regeneration of transgenic cassava plants, July 10, 1996; Wagenings Universiteitsblad, Genetic modification procedure developed for cassava, Wisp'r 1996, No. 18 (June 6,1996), available at

28 Priorities for Cassava Biotechnology Research 1995 1996, supra; T. Babaleye, (International Institute for Tropical Agriculture), Cassava, Africa's Food Security Crop,

29 See the program description on the EMBRAPA/CNPMF website at

30 Thiruvananthapuram, “India CTCRI releases 4 new crop varieties,” FT Asia Intelligence Wire, June 16, 1998; P. Arunmart, “New root could make Thailand global hub Yield almost double that of previous strain, “ Bangkok Post, May 14,1998.

Although many public sector programmes follow a traditional approach to managing viral diseases, some are applying biotechnology techniques to fight mosaic virus present in Africa and South America31, where it is estimated to cause losses of the order of 15–24 percent of the crop32. There are also biotechnology based efforts to increase resistance to viruses and other pests, particularly carried out by the private sector in connection with other crops, but applicable to cassava. Viral resistance is now frequently conferred by inserting into the plant a gene coding for the viral coat protein33. For reasons that are only partly understood, this confers resistance against the virus. Much of the basic work on this technology covers a variety of plants, and may be applicable to roots and tubers, even though initially developed on other plants. Alternative approaches are being explored34

Protection against insect predators requires different techniques. Here the genetic engineering technique being most widely explored and applied to tubers as well as to other plants, is the insertion into plants of a Bacillus Thuringiensis (Bt.) toxin gene. This bacillus kills the insect by means of a toxin that works in its gut through disrupting a biological pathway not found in mammals. The technology has been applied commercially to potatoes in Canada, Mexico, and the United States35. Its application to cassava is being examined at CIAT. Firms are also exploring different approaches to enhance crop resistance to insects. Another method to confer resistance against homopteran insects (whose digestive system is quite different from that of the insects generally considered in using Bacillus Thuringiensis) uses certain substances produced artificially by the plant. Although the claims of the related patent are much broader, its focus is on maize and rice.

31ILTAB, International Laboratory for Tropical Agricultural Biotechnology, Brochure, available at

32Thresh et al, African cassava mosaic virus disease: the magnitude of the problem, CBNISM 3 at 13.

33See footnote in IGG/GR/RI99/3 on this metholodology.

34For Instance, a patent was issued based on the insertion into plants of antisense RNA complementary to the messenger RNA of a specific virus, which apparently provides resistance to the virus.

35A.' Krattiger, Insect Resistance in Crops: A Case Study of Bacillus thuringiensis (Bt) and its Transfer to Developing Countries, (ISAAA Brief No. 2, 1997).

There are still other pests of importance to plants, including bacterial and fungal disease, and nematodes. Biotechnology methods to fight them are based typically on the insertion into plants of genes designed to attack the predators. An example, in which the patent describes research done on potatoes and explicitly claims application to potatoes along with other plants (but does not single out cassava), deals with the use of attacins or cecropins. These are antibacterial compounds produced by insects to disrupt bacterial infections and are described in the patent as providing potatoes with resistance to a “wide spectrum of bacteria, fungi and viruses”. Another example is an approach to protection against nematodes, based on triggering local destruction of affected plant cells when attacked by a nematode.

ii. Post harvest and processing technologies

Extending the root shelf life is considered highly beneficial goal for the cassava economy, as the rapid deterioration of the crop is a constraint for modem production, marketing and processing. Processing of the root has been the traditional method used by producers, with much of the treatment carried out on or near the farm. Simple techniques have been already developed to increase the storage time of the fresh root from a maximum of four days to two weeks36, which have been important, especially in Africa and Latin America where a large share of cassava trade is in fresh produce. The public sector research is also devoting significant attention to the biology of the deterioration processes, in the hopes that they might be slowed by appropriate genetic modification of the plant37. Since conventional breeding methods present some problems because of the nature of the crop38, genetic manipulation appears to offer the most promising route to extend the root shelf life after harvest. Current research concentrates on the identification of the genes that are involved in the physiological deterioration, especially those associated with the synthesis and degradation of phenylpropanoids, which provoke wound-induced responses. Genetic modification aimed at increasing the storability of cassava without the use of post-harvest treatment concentrates on delaying physiological deterioration and enhancing the wound-healing properties of the tissues.

36 CIAT and NRI have developed simple techniques based on plastic-bag storage of fungicide-treated roots.

37E.g., Y. Han et a), Isolation of post harvest physiological deterioration related to DNA clones from cassava, Rev Brasolliera de Mandioca,17:86 (1998); J. Huang et at, Molecular analysis of postharvest deterioration in cassava, Rev. Brasiliera de Mandioca,17:86(1998); CBNISM 3 at 89 131; Beeching et at, Physiological deterioration: toward a molecular understanding, CBNISM 3 at 99; J. Wenham, Post harvest deterioration of cassava; A biotechnology perspective, FAO Plant Production and Protection Paper 130 (FAO, 1995), available at

38In particular, because of the heterozygous nature of cassava.

iii. End-User Oriented Biotechnologies

Research is also oriented towards improving the quality of the product. For subsistence agriculture, the most important is work designed to lower the cyanogen content of the root, a cyanide compound which can be poisonous for consumers if not processed correctly. Modification of this characteristic is an important public sector research goal for certain beneficiaries and significant research to understand the biosynthetic pathway that leads to the cyanogenic products has been conducted. It is likely that this feature will become totally controllable39.

A second direction is to improve the quality of the product for specific uses. This is of particular importance to trade, for the feed or starch production characteristics of the plant can be modified. In this respect, there is substantial private sector interest, reflecting the commercial value of deeper understanding of the biochemical processes by which plants produce starches within the roots, and by which the starches (which are glucose polymers) can be broken into sugars. Scientists have characterized several forms of an enzyme, ADP glucose pyrophosphorylaze, which is involved in the production of starches, and claims the gene coding for this enzyme can be inserted into a variety of plants to alter their ability to synthesize starch, including cassava, potato, and maize. In other examples, enzymes within the plant modify the properties of the starch produced by the plant, including, for example, the balance between the linear polymer (amyloses) and the branched polymers (amylopectins). This can have an important effect on the industrial and culinary uses of the starch. There is one patent on a starch branching enzyme and others directly related to the gene that affects the branching structure and on plants transformed with the gene. The latter patent claims specifically mention cassava and potato. There are several other patents in this area. Although they deal with the uses of the starch, primarily maize starch, they imply that there is a market potential available from manipulating the starch characteristics within other plants. And at a third step in the biochemical pathway, scientists have identified microbial genes40 which alter the process of converting starch into sugar and consequently modify the composition of the plant product. Their claims cover application in many crops, specifically including, among others, maize, cassava, and potato41.

39 Thro et al, Contributions of in vitro biology to cassava Improvement, African Crop Sci J.6:303 315 (1998).

40 alpha-amylase and gluco-amylase.

41Another patent covers the gene coding for the cyclodextrin glycosyltransferase enzyme and transformed plants containing the gene. In this case, cyclodextrins may be produced, and maize, cassava, and potato are among the transformed plants specifically claimed.

It is clearly difficult to attempt a review of all the alternative applications that might be found for a product such as cassava that can be a basic source of industrial and nutritional raw material. As will be discussed below, there are many applications for industrial starches and the industrial starch market is a major evolving market in its own right. However, one important plausible, and quite different, application was noted realated to the use of glucans as substitutes for starches in making paper. Glucans are particular forms of glucose polymer and, as described in the patent, are made preferably in maize, but potato is the second choice, and cassava is among the third choice. There are also efforts to find new ways to use flours made from sources such as cassava, and to make the flour in new ways, as by incorporating greater amounts of fibrous material.

V.2 Broad Issues and Implications for Trade

Although the bulk of trade in cassava is from Thailand to the EC, there is a second trade in industrial starch derived from cassava, primarily from Thailand to other East Asian nations. In analyzing the impact of the new technologies, it is useful to explore first the general implications for each of the major uses of cassava (food, animal feed, and industrial starch) and then to explore the more specific implications for specific markets.

i. Broad Issues

Because of its economic importance to a large number of subsistence farmers, the application of advanced technology to cassava as a source of human food is the most important. This work is largely being done by the public sector. It appears likely that the global biotechnology community will succeed in helping provide more productive and disease resistant materials. However, distributing these to farmers may be more difficult. Even though the potential is for a significant boost of yields, these developments have only indirect trade implications. Some of the material produced by subsistence farmers may be traded to local urban centres, but little is likely to be traded internationally. Moreover, the use of cassava flour in local products may displace a small amount of international trade in grains.

In its animal feed and industrial starch roles, cassava benefits from its high productivity, but suffers from high transportation costs. Already, the potential yield of cassava exceeds 20 tonne/hectare fresh weight, or 8 tonne/hectare dry weight42, without taking into consideration the possible advances in productivity arising from the new biotechnologies. Such yields are greater than those of maize are and only sugar cane may surpass this level. The conversion of the cassava root from raw to wheat equivalent weight is a factor of 443, which indicates the magnitude of the transportation cost barriers to the use of cassava and, together with its perishability, explains why the shipments of cassava products to Europe are in chipped and dried form. Once the cassava is in Europe, its competition with other feedstuffs is essentially one based on cost, which is shaped by the domestic policies.

Cassava production is less than a third of the total root and tuber production, and the 17 million tonnes being exported to European countries are clearly a very small part of a the overall feed market. Thus, factors other than the cassava technology are likely to influence world demand for dry cassava. Assuming continued global economic growth, animal production will continue to increase in middle income nations as well as in Europe, as will the total feedstuff market. Whether cassava will play a role in this expanding market depends on at least three factors that are being shaped by the technology. First, will cassava producers be able to expand their production at a low enough production cost? The potential yield increases are certainly significant from this perspective and studies of the introduction of transgenic virus resistant potatoes into Mexico suggest that, because of the absence of the need for complementary inputs, the smaller farmer may be comparatively advantaged by this new technology44. One study of a related crop is certainly not enough evidence on which to base such an important conclusion, but it is at least conceivable that biotechnologies might, over the long term, economically favour a shift in the location of feedstuff production to smaller farmers, in particular new nations. The second question is whether it will be possible to obtain the on-farm (or at least in-region) post harvest processing necessary to overcome cassava's transportation cost disadvantage. There is already research in this area, and the question becomes one of whether this research will succeed. Finally, there is a third group of questions: to what extent does (or, with appropriate genetic modification, can) cassava provides a balanced or especially important input into the feedstuff mix and how will it compare with other feedstuffs? This is an area likely to receive research should the comparative costs of the products be favourable.

42 Cock et al, The Ideal Cassava Plant for Maximum Yield, Crop Science 19:271 79 (1979).

43 Comparative data and wheat equivalent data from C. Williams, The Agronomy of the Major Tropical Crops (Oxford 1975), based on 1964 data.

44 M. Qaim, Transgenic Virus Resistant Potatoes in Mexico: Potential Socioeconomic Implications of North South Biotechnology Transfer (ISAAA Brief No. 7,1998).

The technology review presented above suggests that, at least in principle, It is likely that any plant able to produce starch or sugars can be genetically modified to produce any form or starch or sugar useful in any industrial or nutritional market. Clearly, the Industrial starch market is growing globally and can be expected to continue to grow. Moreover, there is the ultimate potential of biomass application for energy or fuel production on a renewable basis. Cassava utilization for fuel production is, in general, not economical at this point, but might be so in particular regions or become so as a result of scarcity or increase in fossil fuel prices as a mechanism of managing climate change. There is no biological reason that cassava cannot grow in importance as a source of input for these markets and, based on its high per hectare productivity, ultimately become one of the most important sources. This issue will clearly be one of relative economics, with these differing from time to time and from country to country.

Institutional factors will also shape the utilization of starches from various plants, and generally favour maize starch. First, much of the private sector research on crop adaptation to industrial requirements is being carried out in the developed world and is concentrated on maize, the temperate zone's leading competitor to tropical cassava. To the extent that there is a technological race between the two crops, maize research is currently in a stronger position. Second, the global sugar/starch economy is probably one of the most regulated and politically complex in international agriculture. Third, as many developed world markets will face a choice between near-by maize and distant cassava supplies, they are likely to favour maize. Uncertainty regarding the stability of cassava starch supply to world markets may even make it difficult for cassava to attract the research and investment needed to obtain a significant share of the market.

ii. Implications for Trade

The factors shaping cassava chip and pellet flows, such as that from Thailand to Europe, include the economics of cassava production within Thailand and other potential source nations, the capabilities of the cassava product itself, the economics of alternative feeds within markets such as Europe (which is enormously influenced by internal European policies), the political factors affecting such trade, and the possible emergence of competition. It is only the first two and the last of these factors that are shaped by technology. As noted above, the technological trends may favour cassava or competing crops.

Since trade in cassava products is highly regulated, as evidenced by the role of quotas, probably the most important issue for developing nation exporters concerns possible changes in national policies. The question is whether alternative feed sources could become more easily available within Europe and other possible markets as a result of broader economic and agricultural policy changes, including a reform of EC agriculture policy. As it had been predicted that the new policy environment would entail a slowdown in imports of non-grain feedstuffs, policy factors are probably more important than the technology to assess the potential for trade in cassava products.

Other factors shaping the competitiveness of a nation's cassava chip exports, are those of production cost and transportation costs as well as relative disease risks. Here, it should be noted that there is significant research being conducted on a variety of different disease resistance, so that there is a possibility that new export production centres may emerge, perhaps in such major current producing nations as Nigeria or Brazil. Success in dealing with the African cassava mosaic virus might, for example, significantly improve the competitiveness of Africa as a source of cassava chips.

Success in delaying the deterioration process of cassava could, of course, also lead to an expansion of the local market for other cassava products. Moreover, as noted above, there is scope for adapting cassava to produce a variety of industrial starch products. In addition, there is the possibility of expanded trade in cassava flour, although this will probably depend heavily on consumer tastes. For most industrial products, however, there are many alternative sources and a research differential that, at this time, disadvantages cassava. Nevertheless, the likelihood that cassava production can be improved to make it suitable for industrial utilization is as great, if not greater than that of other crops. The obvious question is whether Thailand or Indonesia, or perhaps Brazil or an African nation, might find and apply the technology to develop certain of these products from cassava on a basis that is so economic as to permit the expansion of regional markets or, conceivably global markets.

iii. Issues for further research and development

It is clear that the technological changes may boost production in a number of regions, by raising yields or reducing the losses associated with pests or disease outbreaks. Considering the role of cassava in some countries facing serious poverty, increased production would be the most important achievement, and one that amply justifies substantial public sector research. However, because of the bulkiness of cassava, increased production will not necessarily mean trade, for cassava is unlikely to be traded under the form of fresh roots, at least in large volumes. This barrier is in addition to the uncertainty of cassava supplies and to the strong competition of alternative products.

The principal issue is whether cassava can be economically processed in a way that makes it more broadly competitive as an animal feed or as a source of industrial starch. However, for such purposes, cassava competes with a variety of other sources of biomass, each of which is also the basis of biotechnological research. The new opportunities for the developing world will derive from ways to process the product, to make it a more transportable animal feed, or to convert it into an industrial product, or even energy itself. Biotechnological modification of the crop might make some of these forms of processing more feasible. With continued appropriate work and success in these various technologies, a number of developing nations may find a way to build new global markets. They offer an important challenge for the global public sector research community

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