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Inheritance of Prolificacy in Maize¹

The inheritance of prolificacy and the relationship of multiple ear development to time intervals between developmental stages of reproductive structures were studied in maize (Zea mays L.) in three different experiments using both quantitative and qualitative methods of genetic analysis.

A six-line diallel involving unrelated parents, F₁'s, and F₂'s were grown at population densities of 17,200 and 34,400 plants/ha over 2 years. General (GCA) and specific (SCA) combining ability effects were significant for both ear number and multiple-ear-weight index (MEWI). This index is defined as the total grain weight minus first ear grain weight divided by total grain weight. The ratio of GCA to SCA fixed-effects variance ranged from 3.7:1 to 7.4:1 for ear number and from 2.5:1 to 7.2:1 for MEWI. Higher ratios were usually associated with the low population density. Phenotypic correlations and the correlations of GCA effects were strongly positive for the time intervals, first-to-second ear shoot emergence, and first-to-second silk. Also, silking interval was negatively correlated with both ear number and MEWI.

In a second experiment, six unrelated parents and 15 F₁'s were dissected daily and the dates of initiation of tassel and ear shoot meristems recorded. General combining ability effects were highly significant for the time periods tassel-to-first ear shoot initiation and first-to-second ear shoot initiation. Only the time period between initiation of the first and second ear shoot was correlated with ear number (–0.57**) and MEWI (–0.63**).

In an experiment involving related inbred lines, their F₁'s, F₂'s, and backcrosses, additive gene effects were highly significant for ear number and MEWI, and dominance effects were significant (0.05 level) for MEWI. Negative correlations were observed between both ear number and MEWI and the time periods, ear shoot emergence-to-pollen-shed, first-to-second ear shoot emergence, and first-to-second silk. For the F₁ and segregating generations of one pair of related lines, a greater frequency of second ears occurred on plants having fewer nodes above the first ear. In both experiments prolificacy factors segregated in a manner predictable from the penetrance and genetic segregation inferred from parents and F₁'s. The genetic analysis on two pairs of related lines indicated that a single locus or group of linked loci account for the majority of the variation in ear number an their segregating generations.

Key Words: Ear number • Floral initiation • Silk delay • Penetrance • Zea mays L.

² Assistant professor, Dep. of Plant Breeding and Biometry, Cornell Univ., Ithaca, NY 14853; professor, Dep. of Agronomy, Madison, WI 53706; assistant professor, Dep. of Community and Environmental Medicine, Univ. of California, Irvine, CA 92717, respectively.

Received for publication April 11, 1978.

This article has been cited by other articles:

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