Improvement Ofsclerotiniaresistance of a Polima CMS Restorer Line of Rapeseed Via Phenotypic Selection, Marker-Assisted Background Selection and Microspore Culture

Sclerotinia stem rot caused by Sclerotinia sclerotiorum is one of the most severe diseases of rapeseed in China and other major growing regions. The objective of this study was to improve the S. sclerotiorum resistance of 'Hui5200', an elite 'Polima' CMS restorer line, by introgression and fixation of resistance alleles from the partially resistant cultivar 'NingRS-1' via phenotypic selection (PS), marker-assisted background selection (MAB) and microspore culture. A progeny designated as 'RSH' with greatly improved Sclerotinia resistance and a similar genetic background as 'Hui5200' was obtained by two backcrosses and one selfing. From a selected elite progeny line (named as 7-5) double haploid (DH) lines were developed. By three cycles of PS considering economic traits and genetic distance analysis, four resistant DH restorer lines with elite economic traits were finally selected. The obtained resistant restorer lines have been used to produce commercial F-1 hybrids. The results indicated that backcrossing plus PS and MAB is effective and suitable for improving resistance of rapeseed to S. sclerotiorum.