An unstable adh1 mutant

In an attempt to isolate an adh1 mutant by the allyl alcohol selection described by Osterman and Schwartz (Genetics 83:63-65, 1976) we poisoned pollen from plants homozygous for bz2-m and containing Ac obtained from D. Schwartz. The bz2-m allele responds to Ac and is probably caused by Ds, and we hoped that the transposition to the Adh1 locus on the same chromosome would be not too infrequent. Poisoned pollen of bz2-m, Ac was used to pollinate W22. From the rare F1 seeds, we obtained only one plant, which showed a 1:1 ratio of alcohol dehydrogenase-positive and -negative pollen grains by in situ staining (Freeling, Genetics 83:701-717, 1976). This plant was selfed and the mutant was found to be viable in the homozygotes. No enzyme activity was detected in the pollen and in the scutellum, and by preliminary experiments, no material cross-reacting with maize alcohol dehydrogenase antiserum was found either.

The mutant is unstable (approximately 10-4 to 10-3 of the pollen grains of the homozygous plants were alcohol dehydrogenase-positive). Plants producing stable pollen were also observed. Segregation of the property to produce unstable pollen and of Ac showed strong but no absolute linkage between these two traits. In addition, we found a single F2 plant (8010540-17), of which the whole F3 progeny produced unstable pollen, regardless of the presence or absence of Ac.

These experiments will have to be extended, because the presence or absence of Ac was not in all cases determined by appropriate test crosses, but in some cases by either the phenotype of the kernels from which the plants were grown or the phenotype of the anthers producing the pollen (bronze versus variegated bronze). This is not unequivocal in all cases.

The data available are interpreted best by assuming that the unstable adh1 mutant which probably originated by the insertion of a transposable element is under the control of a regulatory element different from Ac but linked to it, and that it can be transposed from its locus to the vicinity of adh1 (the case of plant 8010540-17).

H. P. Doring, M. Motto, F. Salamini, and P. Starlinger

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