Provocation of mutability in the level of mutation expressed at the pal-rec gene in Antirrhinum majus.

The pallida gene of Antirrhinum majus governs anthocyanin production. The nature of the mutability displayed by its unstable allele pal-rec was dramatically altered following crosses between two pal-rec pal-rec lines with certain separately maintained lines. In both cases a minority of progeny in F1 or F2 revealed unprecedented infrequent mutability termed 'Low mutability'. These Low plants and their sibs showed many areas of contrasting mutability superimposed on their initial mutability level. This frequent 'shifting' and Low mutability persisted through several generations of offspring obtained by both selfing and crossing to a non-mutable tester line. Evidence is presented to suggest a hypothesis that the two features of altered mutability are two aspects of the same phenomenon caused by joint action of two independent factors J and k, one contributed by each parental line at the outcross.A separate gene, eosinea, governs anthocyanin type, eos eos plants having pelargonin in place of wild-type magenta cyanin. In addition to the previously known simple depression of pal-rec to Pal mutation frequency in eos eos plants, eos also influences the action of J and k when heterozygous (i.e. Eos eos), thus contributing a basal and a third tier of control influencing mutability of pal-rec.Three levels of control are thus identified, the middle tier being governed by the partnership of J and k producing not a simple change but a complex mutability of mutability.