Journal of Agricultural Science, Cambridge (1996), 126, 441-448. © 1996 Cambridge University Press 441 General adaptability of potato genotypes selected in the UK for the Mediterranean region J. BROWN*, M. F. B. DALEf AND G. R. MACKAY Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, Scotland, UK (Revised MS received 18 July 1995) SUMMARY The recombinant genotypes generated with a potato breeding scheme cannot always be evaluated over the range of environments for which cultivar development is aimed. At the Scottish Crop Research Institute, the cultivar breeding programme aims to develop genotypes which perform well in one or more environments in the UK and/or countries around the Mediterranean basin. In each of three years (1984, 1985 and 1986) between 40 and 50 potato genotypes were selected solely on their phenotypic performance in an environment just south of Edinburgh in Scotland. These were then trialled at sites in four environments in the typical ware-producing regions of England and four environments around the Mediterranean region. Despite significant genotype x environment interactions for many traits, the superior genotypes tended to perform well over a wide range of environments. INTRODUCTION Genotype x environment interactions have been recognized by plant breeders for many years (Hill 1975). It is therefore common practice in many crop species to locate breeding stations in the region where the resulting new cultivars will be grown in order that selected genotypes will be better adapted to that particular region. However, many regions grow potato cultivars that were bred elsewhere. Potato crops are grown in many diverse countries with differing soil types, climates and daylengths, while most breeding programmes are located in the northern latitude countries of Europe and North America. The reason for having the breeding programmes in these areas is partly historical, but is also related to the many disease problems which are often associated with repeated vegetative multiplication. The potato is affected by more diseases than is any other major agricultural crop (Hind & Lapwood 1978). Most of these diseases are transmitted by, or the inoculum source derives from, the mother tuber to daughter tubers. To avoid disease accumulating within breeding stocks, potato breeders often carry out early gen- eration selection under conditions which are markedly different from the conditions which will exist in the • Present address: Plant Science Division, Department of Plant, Soil and Entomological Sciences, University of Idaho, Moscow, Idaho 83844-2339, USA. t To whom correspondence should be addressed. areas at which resulting cultivars are targeted. Consequently, the greatest selection pressure is often exerted while potato genotypes are grown under conditions conducive to high-grade seed production (high altitude, northern latitude and short growing seasons). The selected genotypes will not be tested under typical ware (grown for consumption) con- ditions until after the initial rounds of selection have been carried out. One objective of the SCRI potato programme is to develop desirable genotypes for use by the UK potato industry, both within the UK and also for export overseas. Details of a modern breeding scheme are given by Bradshaw & Mackay (1994). The present study examined data from within such a breeding programme to assess the consistency and efficiency of selection within UK trial conditions and compared these with results from the diverse environments found in trials in the Mediterranean area. The results presented here investigate the relationship between adaptability and selection of material assessed in three seasons in the UK (1984, 1985 and 1986) with their adaptability when assessed in the subsequent year in each of three seasons at four environments in the Mediterranean region (1985, 1986 and 1987). MATERIALS AND METHODS Genotypes examined in this study were all derived from the potato breeding programme at the Scottish Crop Research Institute, involving a diverse range of