Inheritance of a Mutation which Suppresses Flowering in Red Clover

A spontaneous mutation isolated from stocks of red clover (cultivarS123) prevents flower initiation unless plants are suppliedexogenously with gibberellin. Mutant plants are also more uprightand densely tillering in their growth habit. Inheritance ofthe non-flowering character was analysed in a series of crossesbetween wild-type S123 and mutant plants. Hybridity followingintercrossing was confirmed using electrophoretic variants ofcytoplasmic phosphoglucose isomerase coded by a- and b-allelesof the nuclear gene Pgi-2. All F₁ plants flowered normally andwere heterozygous at the Pgi-2 locus. However, F₂ segregationsdid not provide the expected ratios, with flowering plants exceedingpredicted levels. One back-cross involving an F₁ plant and themutant parent gave flowering:non flowering and ab:aa Pgi-2 ratiosof 2:1 rather than the expected 1:1. The results are consistentwith the existence of a zygotic lethal factor, originally presentin heterozygous (non-lethal) form in the mutant (non-flowering)parent and tightly linked to the mutated gene. Segregants whichwere non-flowering always displayed the characteristic mutantgrowth form and seeds borne on these plants were lighter incolour than those borne on normal plants. Thus, there existsin red clover a gene designated ‘dig’ (developmentinfluencing gibberellin) which has several pleiotropic effectsincluding suppressing the initiation of flowering in normallyflorally-inductive environments. There are at least two allelicforms of the gene, F (flowering) and f (non-flowering).