LAUSR

The rare chance of homoelogous exchange results in a low efficiency to transfer elite locus between subgenomes of allopolyploid in vivo. Here, we propose a breeding strategy to synchronously improve the subgenomes of allopolyploid, as a case of Sclerotinia sclerotiorum resistance improvement in Brassica napus. The resistance of both parental species was firstly improved by identifying resistance source in B. oleracea and transferring the resistance loci from resistant B. oleracea into B. rapa. The resistance loci from B. rapa and B. oleracea were then pyramided by resynthesizing B. napus. Four groups of resynthesized B. napus, comprising of 37 lines with or without resistance loci from B. rapa and/or B. oleracea, were evaluated for Sclerotinia resistance across 3 years. Significant differences were found among the four groups for both leaf and stem resistance. The group of resynthesized B. napus carrying resistance loci from B. rapa and B. oleracea exhibited the highest level of resistance, out of which one prominent line showed 2.7-fold higher stem resistance than “Zhongshuang 9,” a partial resistant Chinese rapeseed variety. Our data highlights that the strategy of synchronous improvement of subgenomes can efficiently improve allopolyploids.