Did Modern Plant Breeding Lead to Genetic Erosion in European Winter Wheat Varieties? Xiu-Qiang Huang, Markus Wolf, Martin W. Ganal, Simon Orford, Robert M.D. Koebner, and Marion S. Ro ¨der* ABSTRACT The objective of this study was to assess whether modern plant breeding has led to any loss of genetic diversity in modern European winter wheat varieties (Triticum aestivum L.). For this purpose, a collection of 511 widely grown winter wheat varieties of Central and Northern Europe was genotyped with 42 microsatellite markers. In the varieties representing the National List of the UK during the 1980s and 1990s the allelic richness and gene diversity were lower than in the varieties of Recommended Lists covering the time period 1945– 2000. However, no apparent quantitative loss of genetic diversity was found by comparing the different decadal groups of varieties present in the Recommended Lists. Analysis of molecular variance (AMOVA) showed that the variance component among varieties within decadal groups accounted for 96.41% of the genetic variation, but among decadal groups only for 3.59%. The Fst values increased from the 1950s to the 1990s compared to the 1940s with a slight decrease in the 1970s. These results suggested that modern plant breeding has re- sulted in changes of alleles present in the germplasm; however, it appears that modern plant breeding has resulted in no apparent loss of allele numbers, or genetic diversity, in the investigated European wheat varieties over time. F EARS HAVE often been expressed that modern in- tensive plant breeding leads inevitably to genetic erosion (Vellve ´, 1993), which if correct, would have se- rious consequences both for the genetic vulnerability of crops and for their plasticity to respond to changes in the production environment. It is therefore vital for plant breeding programs to maintain sufficient diversity to allow for the production of new varieties able to with- stand attack from new races and pathovars of continu- ously evolving pathogenic microorganisms (Tripp, 1996). The forecast changes in abiotic environmental condi- tions, including the effects of global warming, altered agricultural practices, and the presence of pollutants in the environment will all play their part in requiring a genetic remodelling of plant varieties. The risk of erosion implicates the systems that deliver the products of modern plant breeding systems. Within the EU, this includes Plant Breeders’ Rights (PBR), National Listing (NL) and selection at regional or na- tional levels in voluntary Recommended List (RL) trials or their equivalent. Before they can be marketed in the member states of the European Union, newly bred varieties of crop plants undergo statutory testing, part of which requires that varieties are distinct (D) uniform (U) and stable (S). This DUS testing also forms the basis for the system of intellectual property protection for plant breeders, known as Plant Breeders’ Rights. In many countries there is then a further series of RL trials and tests, either regionally or nationally based, which ensure that farmers have a source of objective advice to direct their choice of variety(ies), in terms of their spe- cific agronomic or commercial attributes. These systems undoubtedly exert a considerable influence on the vari- eties grown. In the UK, the RL reflects varieties which are considered by the regulatory authorities to have the potential to provide a consistent economic benefit to the whole industry. As a result, the overwhelming bulk of all commercial crops grown in the UK comprise RL varieties, although there is no obligation on pro- ducers to restrict varietal choice to these. Crops can- not be commercially traded, however, unless the variety appears on the NL, and to do so they must have been demonstrated as DUS and to be of satisfactory value for cultivation and use. Typically, the RL includes a lim- ited number of cultivars—for example, the 2005/2006 list for UK winter wheat consists of less than 20 entries (www.hgca.com/publications/documents/varieties/ ww06rlcand.xls; verified 11 Dec. 2006), while the NL is much wider, as it includes many outclassed but still commercially viable varieties. A comparison of the ge- netic diversity between RL and NL therefore represents an opportunity to address the issue as to whether the bulk of the UK commercial crop (i.e., the RL) is less or equally diverse as the totality of the crop (i.e., the NL). It has been argued that modern plant breed- ing and its interaction with the NL and RL systems inevitably cause genetic erosion through convergent breeding, manifested as a temporal decline in crop ge- netic diversity. However, objective evidence for this view is lacking. DNA-marker techniques have provided the tools for directly measuring genetic diversity and hence to test for the occurrence of genetic erosion (Almanza-Pinzo ´n et al., 2003). The picture emerging from the analysis of various wheat gene pools is not uniform. Donini et al. (2000) concluded from a set of UK RL winter wheats that changes in the composition and occurrence of al- leles rather than the number of alleles characterized the Xiu-Qiang Huang and Marion S. Ro ¨ der, Leibniz Institute of Plant Ge- netics and Crop Plant Research (IPK), Corrensstr. 3, 06466 Gater- sleben, Germany. Xiu-Qiang Huang, present address: Cereal Research Centre, Agric. and Agri-Food Canada, Winnipeg, Manitoba, R3T 2M9, Canada; Markus Wolf and Martin W. Ganal, TraitGenetics GmbH, Am Schwabeplan 1b, 06466 Gatersleben, Germany; Simon Orford and Robert M.D. Koebner, John Innes Centre Norwich Research Park, Colney NR4 7UH, UK. Received 21 Apr. 2006. *Corresponding author (roder@ipk-gatersleben.de). Published in Crop Sci. 47:343–349 (2007). Crop Breeding & Genetics doi:10.2135/cropsci2006.04.0261 ª Crop Science Society of America 677 S. Segoe Rd., Madison, WI 53711 USA Abbreviations: AMOVA, Analysis of molecular variance; DUS, distinct (D) uniform (U) and stable (S); He, gene diversity; NA, alleles per locus; NL, National Lists; PBR, Plant Breeders’ Rights; PCoA, Principal Coordinate Analysis; PIC, polymorphism informa- tion content; RL, Recommended Lists; UPGMA, unweighted pair- group method with arithmetic average. Reproduced from Crop Science. Published by Crop Science Society of America. All copyrights reserved. 343 Published online February 6, 2007