Peer review

Alternate backcrossing and selling has been employed to convert 5 corn belt inbreds to high-amylose inbreds, with selection in each generation for maximum amylose content. Genetically, the ultimate amylose content is determined by the ae gene in combination with a modifier complex. After three generations of backcrossing, all possible single crosses were made among the inbred lines from each backcross generation and among the recurrent parents. These single crosses were grown under three environments to determine the rate of convergence to the recurrent parent. Significant deviations from expected indicated that selection for maximum amylose content slowed the theoretical rate of convergence to the recurrent parent for such traits as whole kernel oil and protein content, test weight, shelling percentage, ear height, and grain yield. During successive generations of backcrossing the amylose level was maintained, indicating that selection for modifier genes was effective. Selection for positive modifiers in each backcross generation may have carried along linked genes, inhibiting the convergence to the recurrent parent for some traits. These results indicate that when selection pressure is applied for maximum amylose content, more than the expected number of backcrosses will be necessary to convert corn belt inbreds to equally desirable high-amylose inbreds.

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