| Rapeseed plays a major role in national production and resident life.Plant height(PH)is one of the key factors of its yield and resistance,especially the lodging resistance.Flowering time(FT)is another factor affecting the maturity and yield of rapeseed as well.PH and maturing period of rapeseed varieties have become key factors restricting the development of rapeseed industry in recent years.So the varieties with shorter height and earlier maturity are badly needed in the actual production.Therefore,it is of great significance to carry out genetic research on plant height and flowering period in Brassica napus L..In this study,two combinations “YG-1×72-27-1-2” and “HN92 ×74-1002”,were constructed from inbred lines of Brassica napus L..There was significant difference on flowering time of “YG-1×72-27-1-2”.Six generations(P1,P2,F1,F2,B1 and B2)derived from two crosses and F2:3 family from “YG-1×72-27-1-2” were planted in Yangling and Sanyuan respectively from 2016 to 2018.FT was recorded and PH with its related traits were measured in the mature stage.Results were as follows:1.The inheritances of PH and its related indicators were analyzed by mixed major gene plus poly-gene genetic model.Results showed that PH and its related traits of “YG-1×72-27-1-2” were controlled by two pairs of major gene.There were poly-gene effect in some indicators.In cross of “HN92×74-1002”,PH,the first valid branch height(VBH),main inflorescence length(MIL)and numbers of valid branch(BN)were dominated by two pairs of major gene.There were poly-gene effect in some traits while internodal length(IL)was dominated by poly-gene with additive-dominant-epistatic effect.The heritabilities among segregating generations(B1,B2 and F2)of five traits in “YG-1×72-27-1-2” were medium,which were between 42.58% to 67.94%.As for “HN92×74-1002”,the heritabilities of PH,VBH and MIL were between 44.09% to 77.27% while the heritabilities of IL and BN were between 15.24% to 25.09% only.The heritability of PH reached the highest in both crosses.Thus,the selection of plant height was effective in early generation on the breeding process of ideal plant height in Brassica napus L..2.The correlation analysis of PH related traits on “YG-1×72-27-1-2” and “HN92×74-100 2” showed that PH was significantly and positively correlated with VBH,MIL and IL.VBH was significantly and positively correlated with BN,and MIL was significantly and negatively correlated with IL.The results suggested that with the increasing of plant height,length of first valid branch,main inflorescence and internode length increased accordingly.The raise of first valid branch might lead to the decrease of branch numbers,and the add of main inflorescence result in the increase of internodal length.Therefore,VBH,MIL,IL and BN could be regarded as the relevant traits in the breeding process for suitable rapeseed height.3.The F2 population with 170 individuals derived from “YG-1×72-27-1-2” was used as test materials for mapping.1030 pairs of SSR primers were used to screened with polymorphism between parental lines and 119 pairs of primers were selected to be polymorphisms among parents,which accounted for 11.55% of all.The polymorphic analysis of F2 population was conducted by 119 pairs of differential primers,polymorphism could be detected repeatedly through 107 pairs of primers,and the polymorphism rate was 89.92%.160 marked sites with clear bands were obtained and were clustered into 18 linkage groups spanning 900.33 c M in length with a distance between the adjacent markers of 8.50 c M on average.4.The QTL analysis of PH relevant traits and flowering time was made basing on data from F2 population planted in Yangling(2017)and F2:3 families planted in Yangling and Sanyuan(2018).20 QTLs were detected in our study,including 15 QTLs of plant height relevant traits and 5 QTLs of flowering time.15 QTLs of PH related traits were composed of 3 QTLs of PH,2 QTLs of VBH,6 QTLs of MIL,1 QTL of IL and 3 QTLs of BN.A QTL repeat region,which was related to PH and its relevant indicators,was detected in linkage 1,2 and 5 respectively.The LOD score of 20 QTLs ranged from 2.54 to 5.87 and phenotypic variation explained by the single putative QTL varied largely from 0 to 21.75%.q MILYL-3 and q MILYL-2 were characterized by major QTL while the phenotypic variation of q MILYL-3 and q MILYL-2 was 21.75% and 19.17% respectively.Two candidate genes,Bra025720 and Bra025910,were detected in the repeat region of q MILYL-2 and q BN-2. |
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