Temporal trends in the diversity of UK wheat

The common assertion that scientific plant breeding leads to a narrowing in crop diversity has been examined. We have characterised the dominant UK wi nter wheat varieties from the period 1934-1994 using two types of PCR-based DNA profiling (AFLPs, amplified fragment length polymorphisms, and SSRs, s imple-sequence repeats, microsatellites), seed storage protein analysis and morphological descriptors. The varieties were grouped into a series of dec adal groups on the basis of their first appearance on the 'Recommended List ', and by analysis of molecular variance it was shown that an overwhelming proportion of the overall observed variance occurred within, rather than be tween, decades. A further range of statistical indices provided little evid ence for any significant narrowing of overall diversity over the time studi ed. Principal co-ordinate analysis showed that the diversity in the time pe riods overlapped and that the most modern group of varieties encompassed th e majority of the diversity found in earlier decades. The consistent indica tion is that plant breeding has resulted, over time, in a qualitative, rath er than a quantitative, shift in the diversity of winter wheat grown in the UK.