Resynthesized Brassica napus L.: A review of its potential in breeding and genetic analysis

Brassica napus (AACC) is an important oleiferous crop species which is believed to have originated spontaneously as an amphidiploid between B. campestris (AA) and B. oleracea (CC). Thus, resynthesizing B. napus has been widely adopted as a breeding strategy to introduce desirable variation from the parental diploids into this species, which has been greatly facilitated by the development of in vitro techniques. Examples of using resynthesized B. napus in practical breeding are attempts to breed for yellow-seeded character, sterility maintainer function in the nap cytoplasmic male sterility system, high oleic acid content, spontaneous diploid androgenesis, and the character of apetaly. The usefulness of newly resynthesized B. napus in genetic analysis is indicated by examples such as the detection of the silent A-genome locus for the enzyme glucosephosphate isomerase in cultivated rapeseed, and the independent inheritance of flower colour and erucic genes in the C-genome. By comparing genotypes of resynthesized B. napus with those of the actual parental species, we have been able to identify genome specific isozyme loci which can be used as chromosome markers. In conclusion, resynthesisof B. napus will continue to be adopted as an effective strategy for both practical and academic interests.