--D. Barloy and M. Beckert

Phenotypic observation of DH lines. During the last summer we observed in the field more than two hundred selfed progenies of DH plants obtained through anther culture from different genetic stocks. Some of them resulted from spontaneous chromosome doubling, the others were colchicine treated. These first observations concerned the aspects of the lines at the agronomic and morphological levels. Whatever the origin of the material, it looks very homogeneous and stable. A wider experiment planned this summer will characterize more precisely these different DH lines and their different selfed generations for homo-geneity and stability. By observing DH lines derived from well-responding homozygous lines in androgenesis it seems, in a first assumption, that gametoclonal variation might not play a major role in creating genetic variability.

Genetics of androgenesis. The androgenetic potential of such lines was also evaluated. The androgenetic response expressed as the percentage of responsive anthers, ranges from zero to more than 50% and this phenomenon is clearly not continuous: some lines show a null or close to null response, another group is close to 10 or 20% of response and the rest close to 40 to 50%. The data support the hypothesis that only a few genes might be responsible at least for the induction process. The quite good level of androgenetic potential of hybrids made between null or good responding material (Maydica, submitted) indicates a quite dominant or additive system. The fact that it is possible to get material with null response via androgenesis leads us to postulate a possible role of the anther wall in the physiological control at the mother plant level. In addition we did not find large differences between reciprocal crosses concerning the percentage of responding anthers or plantlet regeneration, suggesting that only nuclear genes might be involved.

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