THE CYANOGENIC POLYMORPHISM IN TRIFOLIUM-REPENS L (WHITE CLOVER)

The cyanogenic polymorphism in white clover is controlled by alleles of two independently segregating loci. Biochemical studies have shown that non-functional alleles of the Ac locus, which controls the level of cyanoglucoside produced in leaf tissue, result in the loss of several steps in the biosynthetic pathway. Alleles of the Li locus control the synthesis of the hydrolytic enzyme, linamarase, which is responsible for HCN release following tissue damage. Studies on the selective forces and the distribution of the cyanogenic morphs of white clover are discussed in relation to the quantitative variation in cyanogenesis revealed by biochemical studies. Molecular studies reveal considerable restriction fragment length polymorphism for linamarase homologous genes.