Construction Of Linkage Maps And Gene Mapping Of Three Mutant Traits In Brassica Napus L.

Rapeseed(Brassica napus)is one of the globally most important oil crop for oilseed production.Breeding for plant varieties with ideal plant type and high photosynthetic efficiency can help increase yields in crops.The dwarf mutant Bndwf1,yellowish leaf mutant cdel and down-curved leaf mutant Bndcll of B.napus were used to map the genes after constructing high-density SNP genetic maps.These works may supply novel materials for plant type breeding and high photosynthetic efficiency breeding in B.napus.The main results are as following:1.Gene mapping of the dwarf trait of Bndwf1(1)Inheritance of the dwarf trait:The Bndwfl mutant had deep-green leaf color at the:seedling stage,and obviously shorter archetceture than the wild-type at the harvest stage.In the BC1 population,BC1F2 populations and BC1F2:3 populations derived from the cross between zhongshuang11(ZS11)and Bndwfl,the ratio of dwarf plants vs.tall plants agreed with the Mendel separation of 1:1,3:1 and 3:1,thus the dwarf trait of the Bndwfl mutant may be inferred to be controlled by one dominant gene.Analysis of the agronomic traits in the BC1 population indicated that the dwarf phenotype was caused by reduction of the branching height,the main raceme length and together with the average branching interval.However,the yield of the dwarf plants was not significantly lower than the tall plants in the BC1,BC1F2 and BC1F2:3 populations.(2)Gene mapping:A high-density SNP genetic map was constructed with 150 individuals from the "ZS11 ×(ZS11 × Bndwf1)" BC1 population.The map comprises 1307 bins representing 11650 SNP markers in 19 linkage groups(LGs)and the map is totally 1869.95 cM in length.The locus was mapped in a 228-kb region between SNP markers M19695 and M19704 on the B.napus A09 chromosome based on the SNP genetic map.(3)Analysis of the homologous segments and candidate genes:After searching in genome databases of B.rapa,B.oleracea and B.napus cv.’Darmor-bzh’,the homologous segments of the mapping interval were obtained on the chromosome A09 of B.rapa,chromosome C09 of B.oleracea and chromosome C09 of B.napus cv.’Darmor-bzh’.By alignment with these 4 homologous segments,we perfected the gene annotation in the mapping interval,and got 22 genes in the mapping interval.At last,12 genes were identified as candidate genes for the BnDWFl locus.2.Gene mapping of the yellowish leaf trait of cdel(1)Inheritance of yellowish leaf trait:The cdel mutant exhibited yellowish-leaf phenotype and showed phenotype of deficiency in chlorophyll content in comparison with wild type at seedling stage.After budding,the leaf color of cde1 mutant became gradually to green.The buds of cdel mutant were light-yellow while that of wild type were green.In the one F2 and four F2:3 populations derived from the cross between ZS11 and cdel,the ratio of yellowish leaf plants vs.green leaf plants agreed with the Mendel separation of 3:1,thus it was inferred that the yellowish leaf trait of the cdel mutant was controlled by one dominant gene.(2)Gene mapping:A high-density genetic map was constructed with 89 individuals from the "ZS11 × cde1" F2 population.The map comprises 2878 bins representing 13347 SNP markers in 19 LGs and the map is totally 1968.6 cM in length.The CDE1 locus was mapped in a 378-kb region between SNP markers M29912 and M29878 on the chromosome C08 in B.napus cv.’ZS11’ based on the SNP genetic map.(3)Analysis of the homologous segments and candidate genes:After searching in genome databases of B.rapa,B.oleracea,B.napus cv.’ZS11’ and B.napus cv.’Darmor-bzh’,the homologous segments of the mapping interval were obtained on them.By alignment with these homologous segments,we perfected the gene annotation in the mapping interval,and got 39 genes in the mapping interval.At last,2 genes were identified as candidate genes for the CDE1 locus.3.Gene mapping of the down-curved leaf trait of Bndcll(1)Inheritance of down-curved leaf trait:The leaves of the Bndcll mutant have sharply down-curved and crinkled phenotype,with short petioles at the seedling stage.At the mature stage,the Bndcll mutant plant exhibits a compact and dwarf plant type,while its wild-type exhibits a tall plant type.In the BC1 and reciprocal cross F2 populations derived from the parents ZS11 and Bndcll,the ratio of down-curved vs.normal leaf plants agreed with the Mendel separation of 1:1,3:1 and 3:1,thus down-curved leaf trait of the Bndcll mutant may be inferred to be controlled by one dominant gene.Analysis of the plant type-related traits in the BC1 population indicated that the compact plant type was caused by reduction of the branching height,the main raceme length and together with the average branching interval.(2)Gene mapping:A high-density SNP genetic map was constructed with 109 individuals from the "ZS11 ×(ZS11×Bndcl1)" BC1 population after SNP genetyping.The map comprises 819 bins representing 7490 SNP markers in 19 LGs and the map is 1583.28 cM in length.The BnDCLl locus was mapped in a 6.89 cM interval between SNP markers M46180 and M49962 on the chromosome C05 in B.napus cv.’Darmor-bzh’ based on the SNP genetic map,and the genetic mapping interval is corresponding to a 16.354-Mb physical region.In summary,present works have mapped genes/QTLs related to oilseed rape plant type and leaf colour traits,will provide basis for gene functionality researches and molecular breeding with the novel accessions.