Genetic dissection of intersubgenomic heterosis in Brassica napus carrying genomic components of B. rapa

Abstract

Although strong intersubgenomic heterosis for seed production has been observed between “natural” domesticated Brassica napus (rapeseed, AACC) and a new type of rapeseed into which subgenomic components of Brassica rapa (AA) have been introgressed, the molecular genetic mechanism of this intersubgenomic heterosis is not understood. In this study, a recombinant inbred line population of new type rapeseed derived from a cross between B. napus and B. rapa, together with a population from a backcross with the parental line of B. napus, was used to identify single-locus quantitative trait locus (QTL) and interacting QTL pairs for yield and nine yield-related traits. More than half of single-locus QTLs and interacting QTL pairs detected were involved with the novel alleles induced by the introgression of B. rapa. The alleles directly from B. rapa A genome played a secondary role in contributing to intersubgenomic heterosis. Allelic and nonallelic interactions of both novel alleles generated by B. rapa introgression and the alleles directly from B. rapa A genome contributed to the intersubgenomic heterosis between “natural” domesticated rapeseed and new type rapeseed into which B. rapa had been introgressed. Six loci for fixed heterosis were identified and their possible applications are also discussed.