James C. Reeves

Temporal trends in the diversity of UK wheat

Abstract 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.

DNA profiling and plant variety registration. III : The statistical assessment of distinctness in wheat using amplified fragment length polymorphisms

The use of AFLP analysis to produce DNA profiles from a set of 55 wheat varieties, commonly grown in the UK over the past 60 years, is described. Using six different primer pairs, 90 polymorphic bands were readily recognised and recorded. These AFLP bands are not significantly clustered and hence can be used with some confidence, even though they are not mapped. Statistical approaches to the analysis of the data were developed such that the discrimination between the varieties achieved by the use of the six primer pairs, both separately and in combination, could be derived and compared to that achieved by a common set of morphological descriptors. Various criteria for the definition of distinctness in terms of the number of band differences required between pairs of varieties were also compared. In general, higher levels of discrimination were achieved by the inclusion of greater numbers of bands in the analysis. The optimal number of polymorphic bands appears to be between v and 2v, where v is the number of varieties under test. Discrimination levels were adversely affected if the number of bands was below v/2. Distinctness levels achieved by the use of molecular markers can be calibrated so that they reproduce those seen with morphological characters. The results are discussed in relation to the possible use of DNA profiling methods for distinctness, uniformity and stability testing.

Temporal trends of genetic diversity in European barley cultivars (Hordeum vulgare L.)

The changes of genetic diversity over time were monitored in 504 European barley cultivars released during the 20th century by genotyping with 35 genomic microsatellites. For analysis, the following four temporal groups were distinguished: 1900–1929 (TG1 with 19 cultivars), 1930–1949 (TG2 with 40 cultivars), 1950–1979 (237 cultivars as TG3), and 1980–2000 (TG4 consisting of 208 cultivars). After rarefaction of allelic diversity data to the comparable sample size of 18 varieties, of the 159 alleles found in the first group (TG1) 134 were retained in the last group (TG4) resulting in a loss of only 15.7% of alleles. On the other hand 51 novel alleles were discovered in the group representing the last investigated time period (TG4) in comparison with the TG1. Novel alleles appeared evenly distributed over the genome, almost at all investigated genomic loci, with up to five such novel alleles per locus. Alleles specific for a temporal group were discovered for all investigated time periods, however analysis of molecular variance (AMOVA) did not reveal any significant population structure attributable to temporal decadal grouping. Only 2.77% of the total observed variance was due to differences between the four temporal groups and 1.42% between individual decades of the same temporal group, while 95.81% of the variance was due to variation within temporal groups. The distinction between two-rowed and six-rowed genetic types accounted for 19.5% of the total observed variance by AMOVA, whereas the comparison between ‘winter’ and ‘spring’ types accounted for 17% of the total observed variation. The analysis of linkage disequilibrium did not reveal statistically significant differences between the temporal groups. The results indicated that the impact of breeding effort and variety delivery systems did not result in any significant quantitative losses of genetic diversity in the representative set of barley cultivars over the four time periods.

Technology management and collaboration profile: virtual companies and industrial platforms in the high‐tech biotechnology industries

In this paper we discuss collaboration in the area of technology management. We propose the concept of collaboration profile to describe various forms of networks along key differentiating characteristics. The collaboration profile is then applied using two examples to illustrate different forms of collaboration in the biotechnology industries, the ‘virtual company’ and the ‘industrial platform’. Based on interviews with members of a virtual company as well as members of industrial platforms and drawing conclusions from theoretical insights, the advantages and disadvantages of these forms and their suitability for different stages of the technology life cycle will be discussed. Specifically, we address the following questions: What kind of collaboration profile applies to virtual companies and industrial platforms? How does the suitability of collaboration forms vary with the stage of technology development? Furthermore, we demonstrate the usefulness of the collaboration profile for analysing features and potential problems of collaborations by describing two examples. Focusing on the key characteristics of a collaboration helps to check the appropriateness of the collaboration form and to identify and manage respective problems.

The impact of breeding on genetic diversity and erosion in bread wheat

This paper examines the fate of alleles and changes of genetic diversity in old ( ca 1930s) versus more modern ( ca 1990s) UK bread wheat varieties using 14 mapped DNA microsatellite (simple sequence repeat, SSR) loci and morphological markers. The allelic constitution of varieties belonging to three time periods (early, intermediate, late) was determined. While at certain loci one or more SSR alleles were gained between early and late periods, at others the allelic representation remained constant, although a shift in allelic frequencies could sometimes be detected. No locus showed a clear, net loss in the total number of alleles over the time period. In a further group of loci, there was neither clear gain nor loss, but rather a dynamic flux of alleles. A comparison of the allelic constitution of the UK variety set with a larger genetic pool (non-UK varieties) showed that some loci were rather similar in allelic constitution, while others possessed additional diversity. Certain SSR alleles appeared to be associated with old or modern varieties, possibly indicating associations with chromosome regions under selection pressure. The same exercise was conducted on the basis of 14 of the morphological characteristics recorded in the course of distinctness, uniformity and stability testing of varieties. Overall, this analysis generated a similar picture of changes in diversity to that obtained from the microsatellite data.

Sequence Analysis of the Ribosomal DNA Spacer Region of Pyrenophora spp.; Evaluation of its Potential for PCR Detection in a Seed Health Test

The features of the three species of the Pyrenophora fungus which cause diseases of barley are summarised in Table 1. Seed transmission is an important feature of the disease complex and therefore seed testing is essential as part of an effective control strategy. Conventional seed health tests are time-consuming and labour-intensive. PCR-based techniques have the potential to overcome these problems. Here we evaluate the potential of the fungal intergenic region for development of a PCR-based detection strategy for these three pathogens. Sequencing of this region has been successfully used in other systems to design specific primers for PCR (Xue et al., 1992).