Potato and biotechnology

In vitro conservation, molecular markers and recombinant DNA technologies are creating new opportunities in potato production and transformation

Key points

The potato industry has benefited from major recent discoveries about plant's genetics, physiology and pathology.

Micropropagation is helping developing countries produce lowcost, disease-free tuber "seed" and increase potato yields.

Use of molecular markers helps identify desirable traits in potato collections, thus simplifying the development of improved varieties.

Sequencing of the complete potato genome, now under way, will significantly increase knowledge and understanding of genetic interactions and functional traits.

Genetically modified varieties have the potential to produce more stable yields, improve nutritional quality and facilitate non-food industrial uses, but must be carefully assessed before release.

New molecular biology and plant cell culture tools have enabled scientists to understand better how potato plants reproduce, grow and yield their tubers, how they interact with pests and diseases, and how they cope with environmental stresses. Those advances have unlocked new opportunities for the potato industry by boosting potato yields, improving the tuber's nutritional value, and opening the way to a variety of non-food uses of potato starch, such as the production of plastic polymers.

Producing high-quality propagation material

Unlike other major field crops, potatoes are vegetatively reproduced as clones, ensuring stable, "true-to-type" propagation. However, tubers taken from diseased plants also transmit the disease to their progenies. To avoid that, potato tuber "seed" needs to be produced under strict disease control conditions, which adds to the cost of propagation material and therefore limits its availability to farmers in developing countries.

Micropropagation or propagation in vitro offers a low-cost solution to the problem of pathogens in seed potato. Plantlets can be multiplied an unlimited number of times, by cutting them into single-node pieces and cultivating the cuttings. The plantlets can either be induced to produce small tubers directly within containers or transplanted to the field, where they grow and yield low-cost, diseasefree tuber "seed". This technique is very popular and routinely used commercially in a number of developing and transition countries. For example, in Viet Nam micropropagation directly managed by farmers contributed to the doubling of potato yields in a few years.

Protecting and exploring potato diversity

The potato has the richest genetic diversity of any cultivated plant. Potato genetic resources in the South American Andes include wild relatives, native cultivated species, local farmer-developed varieties, and hybrids of cultivated and wild plants. They contain a wealth of valuable traits, such as resistance to pests and diseases, nutrition value, taste and adaptation to extreme climatic conditions. Continuous efforts are being made to collect, characterize and conserve them in gene banks, and some of their traits have been transferred to commercial potato lines through cross-breeding.

To protect collections of potato varieties and wild and cultivated relatives from possible diseases and pest outbreaks, scientists use a variation of micropropagation techniques to maintain potato samples in vitro, under sterile conditions. Accessions are intensively studied using molecular markers, the identifiable DNA sequences found at specific chromosomal locations on the genome and transmitted by the standard laws of inheritance.

Obtaining improved varieties

Potato genetics and inheritance are complex, and developing improved varieties through conventional cross breeding is difficult and time consuming. Molecular-marker based screening and other molecular techniques are now widely used to enhance and expand the traditional approaches to potato in food production. Molecular markers for characteristics of interest help identify desired traits and simplify the selection of improved varieties. Such techniques are currently applied in a number of developing and transition countries, and commercial varieties are expected to be released within the next few years.

Through the Potato Genome Sequencing Consortium, significant progress is being made in mapping the complete DNA sequence of the potato genome, which will enhance our knowledge of the plant's genes and proteins, and of their functional traits. Technical advances in the fields of structural and functional potato genomics - and the ability to integrate genes of interest into the potato genome - have expanded the possibility of genetic transformation of the potato using recombinant DNA technologies. Transgenic varieties with resistance to Colorado Potato Beetle and viral diseases were released for commercial production in the early 1990s in Canada and the USA, and more commercial releases can be expected in the future.

Transgenic potato varieties offer the possibility of increasing potato productivity and production, as well as creating new opportunities for non-food industrial use. However, all biosafety and food safety aspects must be carefully assessed and addressed before their release.

Glossary

cell culture - in vitro growth of cells isolated from multi-cellular organisms;
functional genomics - research aimed at determining patterns of gene expression and interaction in the genome;
genome - the entire complement of genetic material present in each cell of an organism;
genome sequencing - process of determining the exact order of chemical building blocks that make up the DNA of an organism;
genetically modified - transformed by the insertion of one or more transgenes;
in vitro - in an artificial environment (e.g. cells, tissues or organs cultured in glass or plastic containers);
micropropagation - miniaturized in vitro multiplication or regeneration of plant material under aseptic and controlled environmental conditions;
molecular biology - study of living processes at molecular level;
molecular marker - a genetic marker that is assayed at the DNA level;
trait - one of the many characteristics that define an organism;
transgene - an isolated gene sequence - often derived from a different species - used to transform an organism.

This factsheet was prepared by Andrea Sonnino of the Research and Extension Division and Kakoli Ghosh of the Plant Production and Protection Division, FAO