Genetic control of the pre-anthesis development of spring rape (Brassica napus L.). II.* Identification of individual genes controlling developmental pattern

Abstract

Controlled environment studies of variation in the duration of the vegetative phase of spring rape were conducted with the objective of detecting major genes determining vernalization response. These studies involved analyses of variation within early generation segregating populations and between inbred-backcross lines.

Distributions of unvernalized F₂ plants from crosses between Target, Bronowski, and Isuzu were clearly bimodal when grown under continuous light at 25°C. Duplicate recessive genes were found to determine the vernalization requirement of Bronowski. In Isuzu, however, the vernalization requirement was determined by two independent genes, one having a markedly greater effect than the other on vernalization response. The genes in Bronowski occurred at different loci from those in Isuzu, and Target, which had no vernalization requirement, possessed the dominant alleles of all four genes.

Plants having a significantly shorter vegetative phase than Target were also detected in F₂ and backcross populations of crosses between Target and the other two cultivars. Analyses of the distribution of inbred-backcross lines showed that this character was determined by genes from Isuzu and Bronowski which were not expressed when associated with the parental genotype.

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*Part I, Aust. J. Agric. Res., 30: 251 (1979).