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Reduction of Quadrivalent Frequency in Autotetraploid Maize During a Period of 10 Years

Andre Gilles and L. F. Randolph
American Journal of Botany
Vol. 38, No. 1 (Jan., 1951), pp. 12-17
Stable URL: http://www.jstor.org/stable/2437987
Page Count: 6
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Reduction of Quadrivalent Frequency in Autotetraploid Maize During a Period of 10 Years
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Abstract

The relative frequency of quadrivalent and bivalent association of the chromosomes was studied in a strain of autoploid maize at the beginning and end of a 10-year period. Plants were grown in 1948 from remnant seed of the 1937 harvest and seed of the 1947 harvest. There were fewer quadrivalents and more bivalents at the diakinesis stage of meiosis at the end of the 10-year period than there were at the beginning of the period, the average frequencies being 7.46 and 8.47, respectively. The results suggest that autoploids which form multivalents with a relatively high frequency at the time of their origin during their subsequent evolutionary history may shift to the bivalent type of synapsis that is characteristic of most alloploids. The presence or absence of quadrivalent association of the chromosomes in natural polyploids may not be a reliable criterion for determining their manner of origin by autoploidy or alloploidy.

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