CHARACTERIZATION OF AN UNSTABLE ANTHOCYANIN PHENOTYPE AND ESTIMATION OF SOMATIC MUTATION-RATES IN PEACH

The peach [Prunus persica (L.) Batsch] cultivar Pillar shows variegati on in anthocyanin production in both vegetative and reproductive tissu es. This phenotype is heritable, although the degree of variegation di ffers with genetic background in progeny of outcrosses. Genetic eviden ce supports the hypothesis that the unstable phenotype is caused by an active transposable element. Reversion to wild-type anthocyanin produ ction in Pillar gave rise to mericlinal and periclinal chimeras of pig mented and nonpigmented tissues. Reversion events in LI and LII histog enic cell layers of Pillar produced different phenotypes that could be easily distinguished. The reversion rate in the LI and LII layers was determined using the rate at which periclinal mutant buds and shoots were formed. The reversion rates to wild type in the LI and LII histog enic layers ranged from 0 to 10(-2), and from 0 to 3.6 x 10(-2) mutati ons per branching event, respectively. In families where reversion rat es in the LI and LII histogenic layers could both be measured, the rev ersion rate in the LI layer was about fourfold greater than in the LII .