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This article in CS

  1. Vol. 21 No. 2, p. 217-219
    Received: Apr 11, 1980

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F3 Yield Response to F2 Selection for Gibberellic Acid Insensitivity in Eight Wheat Crosses1

  1. L. O'Brien and
  2. A. T. Pugsley2



The hypothesis that the Gai/Rht alleles have a positive pleiotropic effect on grain yield was investigated by examining the F3 yield responses to F2 seedling selection for GA3 insensitivity within eight wheat(Triticum aestivum L.) crosses. Seedlings were liberally sprayed with a 100 ppm solution of GA3 (Berelex) at the three-leaf stage. Seven days after spraying they were visually sorted into two groups, those that were insensitive and those responsive to applied GA3 as expressed by elongated internodes and a general etiolated appearance. Significant F3 yield increases were obtained in response to F2 seedling selection for GA3 insensitivity in two out of four crosses with the Gai/Rht 1 genotype and three out of four crosses with the Gai/Rht 2 genotype. In seven out of the eight crosses, the highest yielding F3 lines came from the GA3 insensitive populations, but the large Least Significant Differences that resulted from the use of two replicate randomized complete block yield experiments meant the differences among lines were generally not significant. Selection for GA3 insensitivity was simple and rapid, however, the visual classification into only two groups in this study meant that the so-called GA3 sensitive group contained plants heterozygous for GA3 insensitivity. Actual measurement of the height to the second leaf node was the most reliable means of selection for GA3 response among seedlings. Selection for reduced plant height at the F2 seedling stage resulted in subsequent F3 yield increase because of the positive pleiotropic effect of the Gai/Rht genotype on yield. The technique can be integrated with any breeding methodology.

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