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by Derrick Schokman

It was heartening to learn from a recent newspaper report that the Agriculture Ministry has set up a Rs. 8 million plant tissue culture laboratory at Wariyagala, Nillambe, with the intent of producing the country's requirement of potato planting material.

It reminded me that the successful introduction of potato as a cultivable crop in this country was one of the great achievements of the Department of Agriculture in the early years after independence.

Potato was discovered in the upper reaches of the Bolivian and Peruvian Andes by the Spanish conquistadroes. They brought it to Europe in the 16th century. Consequently it was thought that this food crop could only be cultivated successfully in cold climes.

That is why commercial potato production here was confined in the beginning to the cool uplands of the N'Eliya and Badulla districts. Premier Dudley Senanayake's "Grow More Food" campaign was just gathering momentum. Potato production which had been a mere 4,800 tons in 1966 rocketed to 29,000 tons in 1969.

Having been involved in that campaign as a young agricultural officer. I still visualise the scenario, and with the words of that popular song "Carry me back to the 'Virginy, where the corn and 'taters grow" ringing in my ears I am transported back to where the tea (instead of corn) and taters grew, dominating the landscape of the central highlands. Potato had become the second most widely cultivated crop next to tea in that region.

To extend

The development of subsequent technology made it possible to extend potato cultivation to drier climates as well, so long as night temperatures were cool enough to permit tuber formation.

This led to the cultivation of spuds in the Jaffna peninsula during the Maha season. As a result by 1977 there was a total of 8,000 acres under potato: 3,000 acres apiece in the N'Eliya and Badulla districts and 2,000 acres in the Jaffna district.

And so another exceptionally nutritious, easy to cook, home-grown food was added to the local diet, rich in all the vital nutrients except calcium, and vitamins A and D. Plenty of potassium, iron, magnesium, vitamins band (together with complex carbohydrates and a better quality protein than soya.

And potato is not fattening as once thought. The very opposite is now known to be true - boiled potato contains only 23 calories per ounce. Additionally it is rich in dietary fibre which makes it an easily digested and absorbed food.

Planting Material

What more could one ask, everything appeared to be so well and good. There was, however, a fly in the ointment so to speak - the nagging problem of planting material. Potato does not usually grow from pure seed like rice or any other cereal or grain legume.

Potato seed is very poorly viable, which means that it has to be propagated by tubers.

The Department of Agriculture warned farmers not to use any of their harvested tubers as planting material, because tubers grown under tropical conditions would be infected by pests and diseases that only show themselves after planting, especially virus and viroid infections. Clean planting material free of disease had therefore to be imported from potato producing countries in the cool temperate zone.

Apart from the disease factor, the large quantity of tubers required - 18 cwt to the acre - was an expensive item from the country's scarce foreign exchange situation on the one hand, and the farmers' cost of production bill on the other amounting to one half the total.

The alternative was to cut down on tuber imports for planting by producing at least a part of that need domestically. The Department of Agriculture took on the responsibility of doing this in farms over 6,000 feet in the N'Eliya area to ensure clean, disease-free planting material.

These home-grown tubers, along with imported tubers, were issued to farmers who were taught how to store a portion of their harvest without spoiling or the loss of energy to meet the next season's planting demands.

In collaboration with the International Potato Institute (CIP) and Philippine "know-how", inexpensive diffused light storage structures were set up. Farmers soon realised that storing tubers for planting in such structures not only reduced sprouting which affected emergence and stem density, but also showed up spoilage and insect infestation which could be easily detected and remedied.

These operations mitigated somewhat the import of potato planting material. The Department of Agriculture also attempted to introduce a rapid vegetative propagation method with stem cuttings. But this method did not find favour with farmers who found the cuttings difficult to handle and plant.

The local production of tubers for planting also ran into trouble when the Department of Agriculture had to close down some of its farms over 6,000 feet for environment reasons.

The high dependence on imported tubers therefore continued and became more costly with time. Profit margins diminished and many potato farmers were forced out of business.

Tissue culture

Meanwhile scientists at the Department of Agriculture, encouraged by the acceptance of tissue culture in the USA (1985) as a means of propagating potato cleanly and cheaply began their own research in the Central Agricultural Research Institute at Peradeniya.

Potatoes can be propagated in test-tubes while still in the embryonic state, allowing them to form mini or micro stem tubers on the tissue-cultured plants and storing them safely from disease infections. This method of propagation has been adopted in over 30 countries, and has been especially successful in Vietnam.

The research on micro propagation conducted at the Central Agricultural Research Institute has now come of age in the recently opened Plant Tissue Culture Laboratory (PTCL). The production of clean planting material has effectively become an almost separate industry from the production of retail potatoes.

The Director General of the Samurdhi Authority, to which the laboratory is affiliated, has said that the intention is to supply micropropagated planting material for 2,000 acres by the end of this year (2003) and 15,000 acres in three years. He also holds out the prospect of selling micropropagated material to farmers at one-sixth the cost that they are presently paying for tubers.

If this ambitious goal is achieved, it will be a fitting climax to Sri Lanka's potato saga.

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