The genetical control of cold resistance and vernalisation requirement in wheat

Abstract

Vernalisation response in wheat is controlled by genes located on chromosomes 5A and 5D. The variety Chinese Spring has a winter or late allele (vrn1) on chromosome 5A and a spring or early allele (Vrn3) on 5D. Increasing the dosage of the former has no significant effect on vernalisation response, but when the dosage of the latter is increased the response is reduced and flowering takes place earlier in unvernalised plants. A background of alien cytoplasm from Aegilops ovata prolongs the vegetative phase of development and also increases the vernalisation response, although to a lesser extent than chromosomal changes. The same chromosomes are involved in the control of cold resistance. Alleles on 5A and 5D of Chinese Spring condition poor tolerance to low temperatures, while those on 5A of Cheyenne and 5D of Hope confer a higher degree of resistance. Cytoplasmic as well as chromosomal factors play an important part in determining the level of resistance of difference genotypes. Within the group of genotypes studied, there is no statistically significant relationship between vernalisation response and resistance to freezing to temperatures of −6° and −12°C, so that in spite of the fact that chromosomes of of homoeologous group 5 are implicated in the control of both vernalisation requirement and cold resistance there is no evidence that the characters are determined by the same genetic factors.