Original Article

Heredity (1994) 72, 237–241; doi:10.1038/hdy.1994.33

Mixed model for estimating the effects of the Rht1 dwarfing allele, background genes, CCC and their interaction on culm and leaf elongation of Triticum aestivum L., spring wheat

A Beharav1, A Cahaner1 and M J Pinthus1

1The Hebrew University of Jerusalem, Faculty of Agriculture, Rehovot 76100, Israel

Correspondence: A Cahaner, The Hebrew University of Jerusalem, Faculty of Agriculture, Rehovot 76100, Israel

Received 7 July 1993.

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Abstract

A model for the effects of a single gene (SG), background genes (BG), an environmental factor (EF) and the effects of their interactions on quantitative traits is developed. It is a mixed model where SG and EF have fixed effects while BG have a random effect. This model is applied to the analysis of the effects of the dwarfing alleles at the Rht1 locus (SG), interfamily variation (representing BG) and the growth regulant CCC (EF) on coleoptile, leaf and culm length of spring wheat. Culm length of F7 families was tested in a field experiment in the absence of lodging. Coleoptile and leaf lengths of F9 seedlings were examined in a growth room at 18°C. Each family was descended from a single F5 plant, heterozygous at the Rht1 locus. Within each family the homozygous tall (rht1) and the homozygous semi-dwarf (Rht1) genotypes were identified. Thus, comparing nearly isogenic genotypes within random families in advanced generations enabled the estimation of all the main effects and interactions between SG, BG and EF. The restricted maximum likelihood (REML) method was used in the analysis of variance.

In all the three organs CCC caused significant shortening which was somewhat greater in the rht1 than in the Rht1 genotype and the CCC times Rht1 interaction effect on culm length was significant. Considerable and significant interfamily variation was found for all three characters. A significant CCC times family interaction effect on the length of the first leaf was obtained. This interaction effect was of a specific trend indicating a distinct increase in the response to CCC with greater leaf length. No CCC times Rht1 times family or Rht1 times family interaction effects were detected. The use of two graphical/analytical methods proved to be complementary for a complete evaluation of two-way interactions (CCC times families and CCC times Rht1 in the present study).

Keywords:

environmental factor, interaction, polygene, quantitative trait, single gene

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