The key traits of teosinte and maize are unstable in phenotype in each other's background. Stability depends upon a vascular system that can deliver the photosynthate necessary for initiation of the key traits without being either excessive or limiting.
Once a congruous combination is achieved, stability is assured. In reconstructing such a background for maize to have stable expression of two-ranking from teosinte, it was necessary to reduce vascular development in the pith with the string cob trait of primitive corn and increase vascular development in the rind with the combined effects of teosinte segments on chromosomes 3, 4, and 9. Interactions with teosinte segments on chromosomes 1 and 7 may also be involved, all of which increase the proportion of vascular development in the rind.
Walton C. Galinat
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