Natural variants of pearl millet (Pennisetum typhoides) with altered levels of set II alcohol dehydrogenase activity

Two linked genes, Adh1 and Adh2, specify three sets of ADH isozymes in pearl millet. Set I is a homodimer specified by Adh1, Set III is a homodimer specified by Adh2, and Set II is a heterodimer consisting of one ADH1 subunit and one ADH2 subunit. Dry seeds exhibit only Sets I and II. Anaerobic treatment of seeds greatly increases the activity of Sets I and II and causes the Set III isozymes to be expressed. In the investigation reported here, the ADH zymogram phenotypes of 112 inbred pearl millet lines were analyzed. Two kinds of naturally occurring ADH variant strains were observed: in the low-activity variant, Set II activity is low in the dry seed, and no Set III activity is present upon anaerobic treatment. In the high-activity variant, Set II activity is high and Set III isozymes are expressed in the dry seed. The mutation in the high-activity strain appears to affect the product of Adh2 and not the product of Adh1. Dominance tests show that the mutations in both types of variant strains act in cis. These observations and linkage tests indicate that the mutations are closely linked to or at the Adh2 locus.This work was supported by a PHS National Research Service Award Training Grant in Genetics to the Biology Department of the University of Oregon.