QTL Mapping Of Major Plant-type Traits Related To Plant Height And Silique Length In Brassica Napus L.

Improvement of plant types is one of important ways to reform yield and qualities of rapeseed, and the study on the genetic analysis and QTL mapping of traits associated with plant type could provide a basis for molecular marker assisted breeding of the new B.napus. In this study, a population consisting of 185 F2 lines, which was derived from a cross of the 10D130 (semi-dwarf and short silique) and ZS11 (high stem and long silique), was used as the field test materials. Eleven plant type-associated traits were analyzed and the related QTLs were mapped. The major results are as following:Using SSR markers to screen parents (10D130 and ZS11) and 350 of 1864 markers showed 18.8% polymorphism. In final,269 markers and 313 polymorphic sites were screening by deleting some blurred, nonspecific or segregation distortion markers. The resulting map consisted of 17 linkage groups and 234 maker locus, covering 1167.7cM with an average of 4.99cM between markers.Using the method of composite interval mapping (CIM) to analyze the 11 related plant type traits, a total of 19 plant height-associated traits QTLs were detected on the linkage of A01, A02, A05, A09 and C09. Among them,2 QTLs were detected for valid branch height on linkage groups A02 and C09, the LOD score range from 2.9 to 5.73, and the phenotypic variation was explained by the single putative QTL varied from 5.58% to 10.75%; 3 QTLs related to plant height were detected on linkage groups A01, A05 and A09, the LOD score range from 2.77 to 4.16, and the phenotypic variation was explained by the single putative QTL varied from 5.09% to 12.78%; Only 1 QTL related to major inflorescence length was detected on linkage group A02, the LOD score was 4.07 and the phenotypic variation was explained by the single putative QTL was 6.52%; For numbers of valid branch,3 QTLs were detected on A01 linkage group, with the individual QTL accounting for 5.04%～5.76% of the phenotypic variation and the LOD score range from 2.8 to 6.6; 4 QTLs for major stem length were assigned on linkage groups A02 and A05, with the LOD score range from 3.54 to 5.61 and the individual QTL accounting for 6.52%-10.29% of the phenotypic variation; 3 QTLs controlling MIL/MSL (the ratio of major inflorescence length and major stem length),2 QTLs for major inflorescence silique density and 1 QTL for valid branch space were identified on linkage group A02, the LOD score range from 2.89 to 12.5,4.82 to 6.15,and 4.01 respectively, and the individual QTL accounting for the phenotypic variation are 8.28%～16.96%,5.25%～8.07%, and 6.79%, respectively.A total of 12 silique length-associated traits QTLs were detected, including 4 QTLs for each trait, including silique length, silique body length and break length. The QTLs for silique length were detected mainly focus on linkage groups A01, A03 and A09, the LOD score range from 2.73 to 19.82, and the phenotypic variation was explained by the single putative QTL varied from 9.56% to 11.92%; QTLs for silique body length were assigned on linkage groups A01, A03 and A09, with the LOD score range from 3.34 to 21.07 and the individual QTL accounting for 9.87%～16.26% of the phenotypic variation; The QTLs related to break length were detected on linkage groups A02 and A05, with the LOD score range from 3.31 to 7.33 and the individual QTL accounting for 5.61%～15.51% of the phenotypic variation.QTL clusters contained 14 QTLs, from 7 different species, were detected on A02 linkage group. Among them, the confidence interval of valid branch height, major inflorescence length, major stem length, MIL/MSL, major inflorescence silique density and break length have overlapping regions, apart from the QTLs for major inflorescence length and MIL/MSL, the other enhancing alleles derived from 10D130; The QTLs for major stem length and MIL/MSL have same position, but the enhancing alleles come from different parents; The QTLs for major inflorescence silique density and break length have same position and the enhancing alleles come from same parent 10D130. On linkage group A01, the QTLs for plant height, valid branch number, silique length and silique body length have overlapping regions, and their enhancing alleles come from same parent 10D130. Overlapping regions were detected on linkage groups A03 and A09 between QTLs for silique length and QTLs for silique body length, and on linkage group A05 between QTLs for plant height and QTLs for major stem length, respectively, and their enhancing alleles come from same parent ZS11.These results suggested that plant-type traits related to plant height and silique length are typical quantitative traits, which will be useful for facilitating molecular marker-assisted breeding and provide positive influence on plant-type development.