Tall Off-Types in Semidwarf Spring Wheat with Height-Reducing Genes Rht1 and Rht2
- E. W. Storlie,
- H. Xie and
- L. E. Talbert
An objective of wheat (Triticum aestivum L.) breeding and seed purification programs is to develop uniform cultivars. However, lack of uniformity may occur due to outcrossing, mechanical mixtures, or aneuploidy. We were interested in the prevalence of aneuploidy resulting in tall off-types in semidwarf wheat cultivars. Rht1 and Rht2 are the most common height-reducing genes deployed, and reside on chromosomes 4B and 4D, respectively. In this study, tall off-types were selected from 11 cultivars representing Rht1 and Rht2 genotypes. The chromosomal constitution of the tall off-types were determined based on phenotypic and cytogenetic analysis of offspring. Six cultivars with Rht1 genotypes produced an average frequency of 0.15% monosomic 4B plants that averaged from 16 to 22% taller than the height of euploid plants. Five cultivars with Rht2 genotypes produced an average frequency of 0.06% monosomic 4D plants that averaged 12 to 18% taller than the height of euploid plants. Our results indicate that tall off-types resulting from monosomic 4B and 4D conditions occur in several semidwarf cultivars. However, the frequency and phenotypic effect are greater in semidwarf cultivars with Rht1. Thus, use of Rht2 to cause semidwarf habit may help minimize the problem of tall off-types.
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