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Scottish and American scientists are collaborating in deep-freeze research which could underpin the future breeding of new varieties of food crops.

The University of Abertay Dundee is coordinating the Nato-funded project, working with the Scottish Crop Research Institute and the United States Agricultural Research Service in a series of experiments designed to test cryopreservation, storing plant material at temperatures as low as 196 degrees below freezing.

Erica Benson of UAD's department of molecular and life sciences said successful plant breeding depended on reliable conservation of plant material, not only commercial varieties but also those from which they are descended and their wild relatives. "Seeds are relatively easy to conserve, and a vast amount of genetic material is currently available for research and breeding from seeds kept in store all over the world," she said. "Yet for species such as soft fruits and potatoes which reproduce without seeds, this often means keeping large numbers of individual plants growing in fields where they are expensive to maintain, as well as being open to attack from pests and the weather."

Cryopreservation is used to conserve cell cultures from many plants. It could be used to keep genetic material for developing new varieties, but researchers must first overcome difficulties in freezing more complex structures such as a growing shoot.

Dr Benson and Barbara Reed of the US Agricultural Research Service are preserving disease-free blackcurrant plant shoots from the SCRI in liquid nitrogen, using three different methods. They will later examine how ice forms in individual cells in the shoots when frozen, and what factors might influence the success of freezing. The aim is to prevent the formation of large ice crystals which can damage the sensitive plant tissue.