Description
Trifolium occidentale is a diploid wild relative of T. repens with adaptation to dry, saline coastal habitats. Transfer of drought and salt-tolerant adaptive traits from this potential source of germplasm to T. repens could be valuable if interspecific hybridization can be achieved efficiently. To achieve hybridisation, 4x plants of T. occidentale were generated through colchicine chromosome doubling. Interspecific 4x F1 plants were achieved without embryo rescue. F2 populations and backcross (BC) hybrids to white clover were also efficiently achieved. Although male and female fertility in primary F1 and F2 hybrids were lower than in white clover, they were adequate to produce large amounts of seed from small numbers of inflorescences. Thus, early generation pre-breeding interspecific hybrid populations can be readily developed, opening the way for transfer of traits from T. occidentale to white clover. For effective introgression (backcross) breeding, it is also essential that interspecific chromosome pairing and recombination occur. In this study, it was apparent that chromosome pairing was occurring not only between T. occidentale and T. repens subgenomes, but also between the ancestral subgenomes of T. repens. Thus, interspecific hybridization has the potential for major genome recombination and opens the way for introgression of traits from T. occidentale into white clover. Eighty hybrid families, comprising backcross one (BC1), backcross two (BC2) and their inter-crosses, were evaluated in the field and compared with eight commercial T. repens cultivars and nine T. repens x T. uniflorum backcrosses under three natural summer droughts. Some hybrid families performed as well as, or better than, elite cultivars and had superior recovery after drought periods. Selected plants were inter-crossed to further reshuffle the inter-specific chromosomes for introgression.
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Cytological and Agronomic Evaluation of Interspecific Hybrids Between Trifolium repens L and T. Occidentale coombe
Trifolium occidentale is a diploid wild relative of T. repens with adaptation to dry, saline coastal habitats. Transfer of drought and salt-tolerant adaptive traits from this potential source of germplasm to T. repens could be valuable if interspecific hybridization can be achieved efficiently. To achieve hybridisation, 4x plants of T. occidentale were generated through colchicine chromosome doubling. Interspecific 4x F1 plants were achieved without embryo rescue. F2 populations and backcross (BC) hybrids to white clover were also efficiently achieved. Although male and female fertility in primary F1 and F2 hybrids were lower than in white clover, they were adequate to produce large amounts of seed from small numbers of inflorescences. Thus, early generation pre-breeding interspecific hybrid populations can be readily developed, opening the way for transfer of traits from T. occidentale to white clover. For effective introgression (backcross) breeding, it is also essential that interspecific chromosome pairing and recombination occur. In this study, it was apparent that chromosome pairing was occurring not only between T. occidentale and T. repens subgenomes, but also between the ancestral subgenomes of T. repens. Thus, interspecific hybridization has the potential for major genome recombination and opens the way for introgression of traits from T. occidentale into white clover. Eighty hybrid families, comprising backcross one (BC1), backcross two (BC2) and their inter-crosses, were evaluated in the field and compared with eight commercial T. repens cultivars and nine T. repens x T. uniflorum backcrosses under three natural summer droughts. Some hybrid families performed as well as, or better than, elite cultivars and had superior recovery after drought periods. Selected plants were inter-crossed to further reshuffle the inter-specific chromosomes for introgression.
