Cytoplasmic effects on peroxidase activity in crosses between two genotypes of flax (Linum usitatissimum L.)

Crosses were made between two flax genotypes which differed markedly in dregee of basal branching and activity of peroxidase per gramme fresh weight. The two reciprocal F 1 hybrids and parental genotypes were crossed in all combinations to produce four F 2 progenies, four first backcross progenies to either parent, and the parental genotypes plus F 1's. Altogether, 16 progenies resulted; individual plants in each progeny were assayed for peroxidase activity. Plants were sampled at 35 and at 70 days after germination; activities were expressed on a log scale. A model was fitted by weighted least squares procedures to the mean log activities of the 16 progenies in each sample. The model contained parameters for additive and dominance genetic effects, as well as for cytoplasmic effects in terms of differences between all progenies of the one compared to the other reciprocal F 1. Such cytoplasmic effects could thus be evaluated in a maternal or a paternal direction, over F 2's and both backcrosses. The fitting technique involved the sequential elimination of redundant parameters in the model until the minimum group had been found adequately summarising the data. Additive and dominance parameters were significant in each sample; in the second sample (70 days) there were also significant cytoplasmic effects transmitted by male gametes of the reciprocal F 1's.