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This article in CS

  1. Vol. 9 No. 5, p. 647-651
    Received: Apr 10, 1969

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Evaluation of Synthetic Varieties of Upland Cotton Developed Under Two Levels of Natural Outcrossing1

  1. R. J. Kohel and
  2. T. R. Richmond2



For the development of synthetic varieties of cotton (Gossypium hirsutum L.), we chose four parental strains expected to exhibit high heterotic responses for yield. The synthetic varieties were developed over a three-yearperiod in an area of high natural crossing, and in an area of low natural crossing. In each area, combinations of self- and open-pollination were imposed to vary the level of heterozygosity in the resulting synthetic varieties

The synthetic variety produced by open-pollination in the area of high natural crossing contained a calculated 42% heterozyosity, and it yielded equal to the bulk of F1 hybrids among the parent strains. The synthetic variety produced by open-pollination in the area of low natural crossing contained a calculated 12% heterozygosity, and it exhibited no significant heterosis

The largest expressions of heterosis were for yield and to a lesser extent for boll size. Heterotic performance was correlated with the calculated heterozygosity of the synthetic varieties. The performance of the remaining characters appeared to be controlled by additive gene action.

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