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 winter wheat varieties from the period 1934-1994 using two types of PCR-based DNA profiling (AFLPs, amplified fragment length polymorphisms, and SSRs, simple-sequence repeats, microsatellites), seed storage protein analysis and morphological descriptors. The varieties were grouped into a series of decadal 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 between, decades. A further range of statistical indices provided little evidence for any significant narrowing of overall diversity over the time studied. Principal co-ordinate analysis showed that the diversity in the time periods overlapped and that the most modern group of varieties encompassed the majority of the diversity found in earlier decades. The consistent indication is that plant breeding has resulted, over time, in a qualitative, rather than a quantitative, shift in the diversity of winter wheat grown in the UK.