LINKAGE OF THE ALCOHOL-DEHYDROGENASE STRUCTURAL GENES IN PEARL-MILLET (PENNISETUM-TYPHOIDES)

Pearl millet produces 3 ADH [alcohol dehydrogenase] isozymes, Sets I, II, and III. Naturally occurring ADH electrophoretic variants affecting Sets I and II isozymes but not III have been previously described. Analysis of such variants led to the identification of the adh1 structural gene. The existence of a 2nd Adh structural gene was inferred from dissociation-reassociation studies of Set II. A naturally occurring variant affecting the electrophoretic mobility of Sets III and II but not Set I is described. Analysis of this variant confirms the existence of a 2nd structural gene, Adh2. Crosses utilizing this Adh2 marker reveal a dissimilarity with maize and other plants such as sunflower and narrow-leafed lupins. Adh1 and Adh2 of pearl millet do not segregate independently; no recombinants have been observed. This is the 1st major difference encountered in an otherwise remarkably similar genetic and environmental control of the ADH isozymes in maize and millet. The organization of the Adh genes of pearl millet may reflect a more primitive arrangement than that of maize.