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 e ffects, dominance in the direction of low dormancy and non-allelic int eraction of the duplicate type; in addition, there was a small materna l dominance effect in the direction of high dormancy. The genetics of seed dormancy in this cross is as predicted on Mather's theory of gene tical architecture for a character that has been subject to strong dir ectional 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 argue d that, in view of the difficulty of detecting heritable variation for seed dormancy in wild poppies and the rarity of flower colour variant s in wild P. rhoeas, it is possible that seed of the 'Shirley' cultiva r lacks the dormancy of its wild ancestors because of mutation of one or two genes.