INTRODUCTION

The regeneration of potato plants from somatic tissues such as leaf mesophyll protoplasts is now well established (Gunn 1982). Examination of the somaclones raised from these tissues has revealed variation for a range of characters, some such as resistance to common scab (Streptomyces spp.) being of economic importance in potato breeding (Gunn et al. 1985). However it has been demonstrated that the variation occurs only for a limited number of characters and in many respects the somaclones are identical to the parental variety from which they were derived (Secor & Shepard 1981). This suggests that it may be possible to upgrade existing varieties by selecting amongst somaclones for improvements in those characters in which the parental variety performs poorly while maintaining the same level of character expression for those characters in which the parental variety performs well (Thomson et al. 1986). Some recent data obtained to explore this possibility are reported here.

MATERIALS AND METHODS

The data were recorded from field trials of somaclones derived from either Feltwell or Maris Piper which are varieties bred at the Plant Breeding Institute, Cambridge. The trials comprised either two or three replicates of six-tuber plots grown in 1984 and 1985. Total harvested yield and general tuber appearance were recorded. In 1985 the produce from those somaclones selected from the 1984 trials was riddled to obtain the different size grades of the tubers.