Reversal of dominance in a gene on chromosome 5A controlling frost resistance in wheat

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Abstract
The genetic effects on frost resistance, when chromosome 5A from wheat (Triticum aestivum L.) cultivars with varying degrees of frost resistance (Cheyenne, Hope) and T. spelta were substituted into an identical genetic background ('Chinese Spring') were analysed using the parents and the F1, F2, and BC progeny generations. In the crosses CS/Ch 5A × CS/Ts 5A and CS/Ch 5A × CS/H 5A, the parents differed from each other only with respect to chromosome 5A. In the first experiment, the F1 hybrids and the parents were frozen at temperatures of −10, −11, −12, −13, and −14 °C and in the second experiment at −10, −12, and −14 °C. Chromosome 5A of 'Cheyenne' was found to carry a gene controlling intense frost resistance and that of T. spelta and of 'Hope', a gene controlling weak frost resistance. For both pairs of parents and at all freezing temperatures the additive gene effect was greater than the dominant gene effect. The additive to dominant ratio changed from one freezing temperature to the other. At a high (−10 °C) freezing temperature frost resistance was dominant; as the temperature decreased, the direction of dominance was reversed and at the lowest (−14 °C) freezing temperature frost sensitivity became dominant.Key words: Triticum aestivum, wheat, chromosome substitution 5A, frost resistance, dominance.