Genetic Control of Cold Hardiness and Vernalization Requirement in Winter Wheat

Abstract

A high level of cold hardiness is essential to ensure consistent overwintering of wheat (Triticum aestlvum L.) in the Northern Great Plains region of North America. Consequently, a clear understanding of the genetic control of cold hardiness would facilitate plant breeding efforts directed at cultivar improvement for this area. Although several genetic studies have been conducted, there is not a general consensus on the mode of gene action controlling the expression of cold hardiness in wheat. This study used one spring and four winter cultivars representing a wide range of cold hardiness potential to investigate the mode of inheritance and interaction of cold hardiness, determined in a controlled environment that allowed for maximum expression of cold hardiness potential, and vernalization requirement in wheat. Differences in growth habit between parental cultivars were controlled by the Vrn₁ gene. Cold hardiness, estimated as the temperature at which 50% of the plant population was killed (LT_5o), was controlled by genes with either dominant or additive effects. At least one dominant gene was associated with cold hardiness differences between spring and winter wheat, while genes with mainly additive effects determined differences in cold hardiness among cultivars with the winter growth habit. Broad sense heritability estimates for LT_5o in the controlled environment considered ranged from 0 to 88% with most estimates exceeding 50%. In the F₂‐derived F₃ generation, hardy transgressive segregates were most common in crosses between relatively nonhardy cultivars, but no segregates were significantly hardier than the hardiest parental cultivar. Lack of a vernalization requirement did not hinder the development of cold hardiness; however, distribution of F₂‐derived F₃ lines provided evidence of possible genetic linkage or pleiotropism between the gene segregating for growth habit and a gene or genes controlling cold hardiness.