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  1. Vol. 19 No. 6, p. 815-819
     
    Received: Apr 5, 1979
    Published: Nov, 1979


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doi:10.2135/cropsci1979.0011183X001900060017x

Effects of Intergenotypic Competition on Plant Height, Days to Heading, and Grain Yield of F2 through F5 Bulks of Spring Wheat1

  1. R. H. Busch and
  2. D. Luizzi2

Abstract

Abstract

The effect of intergenotypic competition in F2 through F5 bulk generations was evaluated in six tall/semidwarf crosses of spring wheat (Triticum aestivum L.). The bulks had been advanced each generation in competitive yield plots at a commercial production seeding rate. Approximately 100 seeds of each generation (F2 to F5) were sampled in each cross, space-planted, and plant height and days to heading, both found to be monogenic in these crosses, were measured on each plant. The three photoperiod insensitive/sensitive crosses had excess numbers of short plants in the F2 and F3 but two of the three crosses fit monogenic expectations in the and F4 and F5 The sensitive/sensitive crosses fit the expected genetic ratio each generation. A minor shift toward tallness was observed by the F5 when data from the five homogeneous crosses were pooled. Individual insensitive/sensitive crosses fit the expected genetic ratios for days to heading in F5, but when pooled over crosses an excess late-heading plants was detected.

Grain yield of the F2 through F6 of each of the six crosses across generations did not differ significantly. Correlations of the F2 bulk yields with yields of through F6 bulks remained positive with no appreciable decrease. Apparently, changes in bulk populations grown in North Dakota, heterogeneous for plant height and days to heading, were due primarily to genetic segregation, with intergenotypic competition having only minor, but significant, effects. These relatively minor shifts should not inhibit ease of selection for semidwarfism or early heading from competitively grown bulks in North Dakota.

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