Biotechnology and Development Monitor, No. 20, p. 19-20.

Tissue Culture for Coffee: The case of Uganda By Calestous Juma, J.M. Magambo and Hugh Monteith

Keywords:	Uganda; Cell-/Tissue culture; Coffee.
Correct citation:	Juma, C., Magambo, J.M. and Monteith, H. (1994), "Tissue Culture for Coffee: The case of Uganda." Biotechnology and Development Monitor, No. 20, p. 19-20.

Beside the threat biotechnology may form to the export products of many developing countries, the same countries may also employ biotechnology in an attempt to increase their competitiveness, often in their traditional export sectors. An example is Uganda, which has initiated a major tissue culture programme to increase the productivity of coffee.

Many African countries have started biotechnology research to increase the competitiveness of their major cash crops. Some of these countries are dependent on one or two crops for their foreign exchange earnings, and the application of biotechnology to enhance their competitiveness might become essential to their participation in the world market. The case of coffee biotechnology research in Uganda, where researchers are trying to enhance the country's competitiveness in the world coffee market by increasing the stock for replanting, illustrates this point.

The importance of Uganda's coffee
Uganda has gone through two decades of political turmoil, economic decline and agricultural transformation. Since the coming to power of president Museveni in 1986, the country has embarked on a major economic recovery programme, which has resulted in a significant increase in economic performance reflected in an average annual growth rate of nearly five per cent.
Uganda is Africa's second largest coffee producer after Côte d'Ivoire. Coffee is its main export crop, in 1990 accounting for over 79 per cent of foreign exchange earnings. In terms of total domestic revenue, it contributed about 12 per cent in the form of export tax. Foreign exchange earnings decreased in the early 1990s due to the collapse of international coffee prices. The coffee export earnings of 1992 reached their lowest level of US$ 98 million, compared to the average annual earnings over the period 19821989 of US$ 300 million. The share of coffee exports in total exports dropped to about 55 per cent in 1993, while export of nontraditional products increased about 13 per cent between 1992 and 1993.
Coffee production is spread throughout all of Uganda. The robusta variety accounts for up to 92 per cent of total output. The production of coffee uses 250,000 hectares out of the country's 23.6 million hectares. The entire production is carriedout by approximately 1.2 million smallscale farmers, nearly 7.5 per cent of the population and 50 per cent of the smallholder population.

Although industrial output has been growing at a rapid rate of over 10 per cent annually in the last three years, Uganda still has one of the highest ratios of dependence on one cash crop in Africa. Its economy is therefore vulnerable to changes in international coffee prices, or to technological innovations that might enable the growing of coffee in countries which are not among the traditional producers.

Increasing coffee production
The replacement of old coffee trees, yield and quality improvements, and enhanced disease resistance of coffee have been a major policy area in Uganda. In 1990, the Makerere University in Uganda started a US$ 10 million programme to introduce clonal coffee trees in the country. The programme's finances were provided by the Uganda government and the European Union (EU). The aim is to replant all the farms by the end of 1995, providing sufficient financial resources.
About two years ago, it was decided to concentrate all research efforts and funds at a government research institute, the Kawanda Agricultural Research Institute (KARI), where research on tissue culture in coffee had also been conducted. Currently, the project is still funded by the EU and the government, while training and technical support is provided by the Centre for International Cooperation in Agricultural Research for Development (CIRAD, France). At present, both KARI and the University are conducting research in coffee tissue culture.
The yields of robusta in Uganda are around 600 kg of clean coffee per hectare, which is estimated to be 7580 per cent of the potential yield levels using lowinput techniques. The minimum yields for arabica are 450 kg per hectare, some 6075 per cent of the expected output under smallholder conditions. Six clones of robusta coffee capable of giving yields of 2 to 3.5 tonnes per hectare of clean coffee with fertilizer application have become available since the mid1970s. For example, clonal robusta varieties were developed in Uganda in the 1970s, but were not introduced because of the political turmoil of that time. Without fertilizer application, this robusta variety yields up to 1,100 kg of coffee per hectare, and is resistant to the coffee berry disease. Additionally, all six clones have large berries, ripe uniformly, and have a good quality. However, the farmgate price is still as high as that of the other varieties and only a small quantity of these six clones has been available from the coffee nurseries. The main reason for this is the absence of an available optimum propagation technique.

Coffee tissue culture
Conventionally, coffee is propagated from seed or by vegetative cuttings. Both these methods of propagation have disadvantages. Seed propagation is associated with inherent uncontrolled genetic variation in heterozygous cultivars, slow rates of multiplication of seed, and short span of seed viability. Propagation of coffee by vegetative cuttings guarantees uniformity. Since there is more uniformity within plants of the same clone than within plants of different clones, farmers are advised to plant mixed clones in their fields and not to use a single clone (controlled variation).
Cuttings generate relatively low multiplications rates as they can only be obtained from upright (orthotropic) branches. Also, rooting on vegetative cuttings can be very difficult without the application of rooting hormones. At present, approximately 8,000 plants can be produced per annum using this conventional propagation method. This is insufficient to meet the demand.
Multiplication by tissue culture techniques could provide a viable alternative to these traditional methods of coffee propagation. Tissue culture methods permit the production of relatively uniform plants on a massive scale in a shorter period, and with a narrower genetic base than is possible under the conventional methods. Again, the danger of this narrow genetic base is addressed by mixing clones.
Using tissue culture for the propagation of coffee plants, three different methods can be used: microcuttings, direct somatic embryogenesis, or plant regeneration from callus (see also Monitor no. 4).

Application of in vitro micropropagation on traditional African export products

crop	country
Oil palm Date palm Cocoa Coffee Tea Pyrethrum Suar cane Tabacco Ornamentals	Ivory Coast and Nigeria Algeria, Egypt, Morocco and Tunesia Nieria, Ghana, and Cote d'lvoire Kenya, Uganda and Zimbabwe Kenya Kenya Kenya and Zimbabwe Zimbabwe Kenya and Mauritius

Microcuttings or nodal culture comprise a tissue culture approach which entails culturing nodal stem segments carrying dormant auxiliary buds, and stimulating them to develop. Since this method involves the exploitation of buds already present on the parent stock plant, it provides means of clonal multiplication. Each single segment can produce 79 microcuttings every eighty days.
However, coffee nodule culture has high primary contamination rates ranging between the 60 and 100 per cent, depending on the age of the nodal segment cultured. This contamination is often due to fungi which emanates from the mother plant in the open fields.
Furthermore, coffee contains high levels of phenols, making phenolic oxidation a serious problem in primary root cultures. Phenolic oxidation is the browning of plant tissue culture and the adjacent culture medium due to the lightmediated oxidation of polyphenols to quinines which are highly toxic to the cultured tissue. It has also been noted that the rate of phenolic oxidation is dependent on the source of nodal segment and species, robusta coffee being more prone to phenolic problems than arabica coffee.
The problem of high contamination rates can be reduced by pretreating the mother plants with fungicides prior to the collection of the primary microcuttings. Also, microcuttings of the three nodes from the apex are normally used, since the rate of contamination tends to increase with the age of the nodal segment. In this connection, young plants grown in greenhouses are preferred as sources of microcuttings.
A promising solution to the problem of phenolic oxidation is presoaking of microcuttings in antioxidants such as citric acid and ascorbic acid prior to culture initiation. Antioxidants are also incorporated in the culture medium, while activated charcoal is incorporated in the medium for absorption effects.
At the first sign of phenolic oxidation, the cultured nodule segments are often transferred to a fresh medium.
In spite of all these precautions, great difficulties have been experienced with robusta coffee in laboratories in producing plants through microcutting. Therefore, before being properly exploited as a means of propagating Robusta coffee, it needs further investigation.

Direct somatic embryogenesis in coffee is normally induced by culturing leaf segments in a medium until the development of wellformed somatic embryos takes place. Direct somatic embryogenesis has several advantages over propagation by microcuttings. It does not have the problems of phenolic accumulation in the medium, and the contamination rates are generally very low. Furthermore, the genetic variability is relatively low at 510 per cent and the method permits the development of plantlets in larger numbers than is possible with the microcuttings method. For example, one leaf segment can produce hundreds of plantlets in a single culture cycle, whereas the microcutting method requires several subculturing cycles in order to get a comparable number of plantlets.
In cloning local robusta coffee, the Department of Crop Science at the Makerere University has now successfully obtained plantlets with this method. After 10 weeks of culturing, torpedoshaped embryoids were transferred to an appropriate regeneration medium where they developed into plantlets in four weeks. The plantlets were acclimatized, but the survival rate has remained low. More investigations on acclimatization techniques are needed before this method is to be commercially exploitable.
Propagation through callus regeneration is normally done by inducing it on leaf segments. After four weeks of culturing leaf segments on the appropriate medium, callus starts to form at the edges. The developed callus is then transferred to a germination medium and develops numerous embryoids in 56 weeks. The embryoids start differentiating into a first pair of leaves in another two weeks of growth. They are transferred to a germination medium where they develop into plantlets. The plantlets are acclimatized in the greenhouse, but the survival rate is again very low.
This method can generate more embryoids than the direct somatic embryogenesis method, but it has a high genetic variability rate (somaclonal variation). It also takes relatively longer to develop plantlets than the microcuttings or direct embryogenesis methods. However, this method can be a very useful tool in developing new plant varieties by screening and testing somaclonal variants for characteristics of agronomic potential.

Although the research is in its early stages and it will take several years before the techniques are applied, it might contribute to an improvement of Uganda's position on the international coffee market. Other coffeeproducing countries, such as Kenya and Colombia, are also conducting research on coffee, but they are generally putting more emphasis on arabica than on robusta.
Such technological responses, however, will not safeguard the longterm stability of the economy. There are too many other competitors entering the market and the prices are generally highly fluctuating. Economic stability will therefore depend on the economic diversification currently being planned.
Calestous Juma (ACTS)/J.M. Magambo (Makerere University, Uganda)/Hugh Monteith (ACTS).

Sources
C. Juma, J. M. Mugabe and P. KameriMbote, Coming to Life: Biotechnology in African economic recovery. Nairobi: ACTS Press/London: Zed Books (Forthcoming).

J.M.A. OpioOdongo (1992), Designs on the Land: agricultural research in Uganda, 18901990. Nairobi: ACTS Press.

J.M.A. OpioOdongo (1993), Research and Higher Education in Uganda. Nairobi: ACTS Press.

Personal communication with Dr. J. F. Kakule, Uganda National Council for Science and Technology.

Contributions to the Biotechnology and Development Monitor are not covered by any copyright. Exerpts may be translated or reproduced without prior permission (with exception of parts reproduced from third sources), with acknowledgement of source.

back to top	monitor homepage	index of this issue
	contact us