Genetic erosion and genetic ‘pollution’ in forage species and their wild relatives.

1. Genetic erosion and genetic ‘pollution’ in forage species and their wild relatives. Michael T. Abberton Legume Breeding and Genetics Team Institute of Grassland and Environmental Research John M. Warren Institute of Rural Sciences University of Wales Aberystwyth, Ceredigion, Wales, UK

2. Forage species • Often long-lived perennials • Widespread in agricultural and semi-natural landscapes • Often outbreeding with high levels of heterozygosity

3. Recruitment from seed is at a low level • Vegetative spread may result in dominance of a few clones • Hybridisation with ‘wild’ relatives can occur-likely to be at low levels in some cases (e.g. Trifoliums, ryegrass/fescue) more in others (e.g. perennial ryegrass/Italian ryegrass)

5. Genetic Erosion • Major threat is loss of habitat • Within species erosion likely to be significant for future breeding • Loss of diversity in a few wild relative species may be important

6. Using germplasm from sites of potential genetic erosion Collecting trips to Bulgaria, former Czechoslovakia and Poland Anticipated changes in management Expected that traditional managements would favour germplasm with traits for interest for future varieties in UK

7. 44 different lines from Poland characterised under field conditions as individual plants for Leaf size Height Spread Flowering date Flowering density Disease Rooting Tolerance to grazing Winter damage etc

8. Initial evaluation under cutting Four best lines selected Ac 4162 Ac 4164 Ac 4174 Ac 4179 Further evaluation under grazing Compared with control of same leaf size

9. Evaluation under continuous sheep grazing Clover D.M. Yield Kgha-1 2nd year 3rd year Ac 4162 1415 788 Ac 4164 1944 1473 Ac 4174 2271 1681 Ac 4179 2424 1850 S184 3176 2924 Menna 2902 1458 Best line identified 200 plants evaluated as spaced plants Evaluated under continuous sheep grazing in 2003 17 best plants selected

10. Selection line evaluated under continuous sheep grazing Control Selection line

11. Wild relatives collected at sites • T. fragerifum (strawberry clover) • T. angustifolium (narrow clover) • T. vesiculosum (arrow leaf clover) • T. spadiceum (large brown clover)

13. Related species that can hybridise to white clover • T. ambiguum. Hybridises with extreme difficulty. Ovule culture. Important in breeding of white clover • T. nigrescens (putative ancestor). Hybridises easily but F1 is annual triploid. Important in breeding of white clover • T. occidentale (putative ancestor) Diploid • T. uniflorum Tetraploid. Hybridises with difficulty

14. Priorities for in situ conservation in the clovers • T. fragiferum • T. repens • T. cherleri • T. hirtum • T. subterrranean • T. pratense Lamont et al Chapter 4 Plant Genetic Resources of Legumes in the Mediterranean Maxted and Bennett (eds) Kluwer 2001

15. White clover Genetic exchange between crop to wild relative unlikely to have significant impact: (i) Few species will cross (ii) Difficulty of hybridisation (iii) Low fertility of F1

16. In situ conservation of : T. ambiguum T. nigrescens and of the immense genetic diversity within the species itself is high priority with respect to white clover breeding. • Some related species may become of greater agricultural significance in their own right.

17. Genetic ‘pollution’ • Exchange between introduced varieties and semi-natural populations likely to be common • Exchange with related species less common and often resulting in hybrids of low fertility

18. Genetic exchange between introduced and semi-natural grasses (Warren et al Heredity 81 556-562 1998) • Compared perennial ryegrass (Lolium perenne) and Agrostis curtisii (limited distribution in S. England) using isozymes • Differences in genetic structure: deficit of heterozygotes in L. perenne

19. Agrostis curtisii: adjacent populations more genetically similar. • Not the case for L. perenne • Evidence of gene flow from introduced varieties into semi- natural grasslands e.g. Romney Marsh in Kent, Aberystwyth on the west coast of Wales • No apparent major impact on ecology

20. Effects on other species • Comparison of modern varieties and old varieties/landraces • Invertebrate counts at 3 N levels

23. Questions • Relationship between molecular diversity and diversity in important traits ? • Is hybridisation likely to upset clines of adaptive significance (e.g. cyanogenesis in white clover, keel colour polymorphism in Lotus corniculatus )? • Effects of hybrids (e.g. triploids) on conservation • Trait specific effects on fitness ?

24. Acknowledgements • Legume Breeding and Genetics Team, IGER: Huw Powell, Andy Williams, Athole Marshall • Department of Environment, Food and Rural Affairs • Biotechnological and Biological Sciences Research Council