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Detection of Epistatic, Additive, and Dominance Variation in Winter Wheat (Triticum aestivum L. em Thell.)¹

The objectives of this study were to determine whether epistasis plays a significant role in the genetic systems for selected traits among several winter wheat (Triticum aestivum L. em Thell.) cultivars and to evaluate the importance of additive vs. dominance gene action for traits not influenced by epistasis. In each of two replicated experiments, two cultivars (referred to as testers L₁ and L₂) and their F₁ (L₃) were crossed to each of other cultivars and evaluated in a single field experiment. The deviations (cultivar x L₁ + cultivar x L₂ — 2 cultivar x L₃) were analyzed to provide a test for epistasis. An additive-lominance model was fitted to the data for those characters not affected by gene interactions.

Results of the two experiments were generally consistent with respect to the detection of epistasis. Epistasis affected the expression of heading date, kernels/spikelet, and grain yield, but not of plant height, protein content, tiller number, spikelets/spike, and kernels/spike in both experiments. Epistasis was indicated for kernel weight in one experiment but not the other. Expression of epistasis was influenced by particular cultivars, indicating that a limited number of cultivars may not be sufficient to detect nonallelic interactions for a character within this species.

Additive gene action was predominant in both experiments for protein content, spikelets/spike, and kernels/spike, suggesting that improvement of those characters can be achieved through standard selection procedures. Evidence for dominance gene action was obtained for plant height and kernels/spike in one experiment.

The results of this study indicated that epistasis may be a nontrivial factor in the inheritance of agronomic traits. Genetic models neglecting epistasis may result in biased information.

Key Words: Heading date • Plant height • Protein content • Yield components • Grain yield • Gene action

² Graduate research assistant, professor, and associate professor. Dep. of Agronomy, and associate professor, Dep. of Statistics, Oklahoma State Univ., Stillwater, OK 74074.

Received for publication March 12, 1975.