Abstract:
In the common morning glory (Ipomoea purpurea) a mutator system located at white flower alleles (a) of locus A/a causes revertant sectors of blue anthocyanins on flowers and stems, and the mutator behaves genetically as though transposons are inserted into a alleles (resulting in unstable a alleles, denoted a*). Results of this study show that germ-line revertant A genes have very low (A --> a) germ-line mutation rates (< 0.0005) compared to rates of a* --> A mutations (typically about 0.005). Another type of allele derived from lineages carrying a* alleles exhibits much greater floral sectoring rates (and hence rates of mutation in the floral epidermis), but these alleles have unchanged rates of stem sectoring and germ-line reversions. New mutant morphologies, such as double flowers, are obtained with high frequency from a *a* and other lineages. Sectoring rates in the floral epidermis are influenced by genotypes at a recessive pigment-intensifier locus (I/i), which is unlinked to locus A/a, and this is analogous to mutators in Petunia hybrida. Sectoring rates appear to be increased when plants are grown under colder conditions. In wild populations of I. purpurea in the southeastern United States, a* and stable a alleles rarely are present in frequencies exceeding 1 %; however, they are often present in somewhat lower frequencies, as are various other deleterious morphological mutants. These observations are consistent with the hypothesis that one or more families of transposons are present and active in these populations.

KeyWords Plus:
ANTIRRHINUM-MAJUS, TRANSPOSABLE ELEMENTS, IPOMOEA-PURPUREA, INSTABILITY, LOCUS

Addresses:
EPPERSON BK, UNIV CALIF RIVERSIDE,DEPT BOT & PLANT SCI,RIVERSIDE,CA 92521

Publisher:
OXFORD UNIV PRESS INC, CARY