Review: Breeding spring canola (Brassica napusL.) by the use of exotic germplasm

Abstract

Rahman, H. 2013. Review: Breeding spring canola ( Brassica napus L.) by the use of exotic germplasm. Can. J. Plant Sci. 93: 363–373. The need of broadening genetic diversity in spring canola (Brassica napus) breeding programs seems to be the general consensus among canola breeders and researchers. Diversity analysis by the use of molecular markers has identified several B. napus gene pools as well as allied Brassica species that are genetically distinct from spring canola B. napus; and these gene pools can be used for the improvement of this crop. Use of genetically diverse and un-adapted B. napus germplasm in the breeding of spring canola can be challenging, as introduction of several unwanted traits/alleles from exotic germplasm into spring canola occurs, and this would require repeated cycles of breeding for improvement. Similarly, use of allied species can be even more challenging due to the difficulties associated with interspecific hybrid production, sterility of hybrids, linkage drag, and the introduction of unwanted alleles. However, this can be compensated in the long-term perspective for the improvement of this crop. Some research efforts have been made in recent years to broaden allelic diversity in spring canola for the improvement of seed yield and other traits in open-pollinated and hybrid cultivars with promising results. Seed yield is a complex trait which is controlled by several gene loci with multiple alleles at these loci as well as interactions between loci and different alleles. This makes the identification of right allelic combinations an extremely challenging task. However, canola breeders have been able to make steady improvements in this crop in past decades based on the amount of allelic diversity present in existing breeding material. Introduction of favourable new alleles in breeding programs would allow breeders to create superior allelic combinations, enhancing the diversity in current breeding materials to further improve the crop. With the availability of the Brassica genome sequence, knowledge of sequence variation in specific genes and cost-effective high-throughput genotyping, it is expected that molecular plant breeding will play an important role in the breeding of canola cultivars. Discovery of favourable allele combinations in a short span of time is likely to be facilitated through the application of modern breeding tools.