INTRODUCTION

Potato breeding involves selection over several years from a large number of clones, and the breeder has many varieties to maintain. Seed numbers are inevitably low for both practical and economic reasons. This is often a limiting factor in the progress of a variety through advisory and developmental trials. It is therefore advantageous to accelerate seed production at this stage by means of micropropagation.

The Potato Section of the National Institute of Agricultural Botany (NIAB) produces its own seed of new varieties for Recommended List trials and other advisory trials. Prior to 1982 primary propagation was carried out by virus tested stem cuttings (VTSC); this gave improved multiplication rates over tubers and the plants were free from pathogenic fungi (Hirst & Hide 1966). In 1982 NIAB replaced stem cuttings with in vitro propagation (micropropagation); this gave better control of multiplication, improved hygiene and easier transportation of material. Micropropagation reduced seed production time for most varieties by one year.

METHOD

The method consists of a phase of micropropagation followed by transfer to soil under glass and finally transplantation into the field (Wooster & Dixon 1985). Polythene tunnels or screenhouses may be used when field conditions are not suitable for high value seed.

Laboratory stage

The potato is relatively easy to propagate in vitro using axillary buds as the basic propagule. Initial explants can be taken from plant stems or tuber sprouts.