Is the heterosis of the Corn Belt Dent derived from the interspecific vigor of independent domestications of Mexican and Guatemalan teosinte?

Since the early studies of H. A. Wallace and W. L. Brown, of E. Anderson, of G. S. Johnston and others, the heterosis of Corn Belt Corn has been shown repeatedly to stem from combining Northern Flint-like inbreds with Southern Dent-like ones.

There are a number of floral and cytological traits that seem to associate the Northern Flints with Guatemalan teosinte on the one hand, and the Mexican teosintes with the Southern Dent on the other. The Northern Flints and Guatemalan teosinte have reduced floral condensation, flat staminate glumes and lack internal chromosome knobs. The Southern Dents and the Mexican teosintes have a higher level of floral condensation, round staminate glumes and internal chromosome knobs. There are several objections to this new hypothesis which I cannot at present explain, but this does not mean that the hypothesis is invalid. Rather, the objections may reflect inadequate information. The Guatemalan teosinte has terminal knobs unknown in corn--its Northern Flints included. Certain of these terminal knobs (or large chromomeres) are known to extend the length of the chromosome over its homologue in corn (C. V. Pasupuleti and W. C. Galinat, 1982). But why and how should such knobs be shed during an origin of the ancestor of the Northern Flints? Is a primitive form of Nal Tel such a domesticate of Guatemalan teosinte and the ancestor of the Northern Flint? Where is the archaeological record of such origin by domestication? The early archaeological record is incomplete, if not absent, but it may be discovered.

Walton C. Galinat

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