GENETICS OF SEED DORMANCY IN PAPAVER RHOEAS

Seed dormancy in a cross between wild Papaver rhoeas and its 'Shirley' cultivar appeared to be controlled by genes that displayed additive effects, dominance in the direction of low dormancy and non-allelic interaction of the duplicate type; in addition, there was a small maternal dominance effect in the direction of high dormancy. The genetics of seed dormancy in this cross is as predicted on Mather's theory of genetical architecture for a character that has been subject to strong directional selection. During the breeding of 'Shirley' poppies, at least six flower colour mutations were obtained in less than 20 years in a population whose effective size must have been very small. It is argued that, in view of the difficulty of detecting heritable variation for seed dormancy in wild poppies and the rarity of flower colour variants in wild P. rhoeas, it is possible that seed of the 'Shirley' cultivar lacks the dormancy of its wild ancestors because of mutation of one or two genes.