Genetic control of environmentally induced DNA variation in flax genotrophs

Abstract

Heritable changes can be induced in the amount of nuclear DNA of the Stormont Cirrus variety (PL) of flax when grown in the specific environments of nitrogen and phosphorus, but such changes did not occur in variety Royal (R). Changes occurred in the amount of nuclear DNA of R when the PL nuclear and cytoplasmic factors were introduced by crossing. In the experiments reported here, tests were made on the plasticity of the F1's of their reciprocal crosses to PL and R to understand why L and S genotrophs are stable. The results suggest that there may be a feedback from nucleus to cytoplasm in L0, which inactivates the cytoplasmic factor. Possibly a paramutation-like mechanism adjusts the different amount of DNA, or heterochromatin, between the homologous chromosomes in heterozygotes. L3 and S3 DNA has reverted to the same amount as in PL. This reversion in DNA appears to be accompanied by an increase in stability rather than in any gain in plasticity. Key words: environment, flax, genotrophs, DNA variation.