| Brassica napus L.is the largest oil crop in China,and its heterosis is significant.B.napus is the main cultivated species.The genetic basis of B.napusis relatively narrow compared with other Brassicaspecies.Plant breeding requires newgenetic resources,importingand aggregating of different good traits.Genetic structure and genetic diversity analusis of germplasm has become an important basis for breeding.Genetic diversity is the basis of germplasm resources evaluation and heterosis utilization.In a certain range,the greater the genetic difference of parents,the more significant heterosis.Thus,to understand the genetic diversity among parents,divide the parents into different heterosis groups,it is helpful to guide the selection of strong heterosis combinations and make more effective use of heterosis.In this study,30 elite B.napus lines were evaluated for their genetic diversity by agronomic characters and SSR(Simple Sequence Repeats)and SRAP(Sequence-related Amplified Polymorphism)markers.The obtained results will provide guidance for parent selection and hybrid breeding in the future.The results are as follows:1.Analysis of variance(AMOVA)of 11 agronomic and quality traits of 30 parent lines showed that the variation degree of the tested materials reached a very significant level.Cluster analysis and principal component analysis showed that most maintainer lines and restorer lines were separated from each other.The variance analysis showed that the coefficient of variation within populations was 86.40%,the difference among populations was 13.60%,showing that the difference within maintainers and restorers was greater than that between them.The results showed that there was a certain genetic difference between restorer lines and maintainer lines.2.12 pairs of primers with high polymorphismscreened out from 43 pairs of SRAP primer combinationswere used to amplify 32 lines.A total of 77 polymorphic bands were detected,with an average of 6.4 polymorphic bands per pair of primer combinations.The average polymorphic rate was 98.72%.Each pair of primers could amplify 4~9 polymorphic sites.The polymorphic bands amplified by primer combination Em5+Me22andEm5+Me23were the highest.Only 4 polymorphic loci were amplified by primer combination Em5+Me30 and Em12+Me18.Polymorphism information content of SRAP primercombinations wasfrom 0.47(Em14+Me20)to 0.78(Em14+Me22),with an average of 0.59.3.8stable polymorphic primers screened out from 36 pairs of SSR primers were used for amplifying the 32 tested lines.As a result,51 loci were amplified,of which,49 were polymorphic.The average was 6.13 with the average polymorphicpercentage of 96.08%.BrgMS343 primers could amplify 8 polymorphic loci.BrgMS629 could only amplify three polymorphic loci.Each primer could amplify3~8polymorphic loci.Polymorphism information content of each SSR primer combinations ranged from 0.22(BrgMS90)to 0.65(BrgMS629),with an average of 0.43.4.Amplication results of SSR and SRAP markers were used to do cluster analysis of 32 rapeseed lines.The results showed that the tested lines were divided into three groups at the genetic similarity coefficient of 0.65.The first group consists of 19 lines,14 of which are restorerers,including Q10 C,Sh11,Q7 C,S11R,Z821 R,and5 aremaintainers,Zhong 4,CZ49,ZY18,2000B7 and New B1.The second group consists of 10 lines,all the lines are maintainers except one restorer(Y6).The third group includes ZY72,No.31(B.juncea)and No.32(B.rapa).The results of principal component analysis,population structure analysis and cluster analysis are basically consistent.The analysis of molecular variance showed that the variance components of maintainers and restorers were 95.46%and 4.54% respectively,the difference within maintainers(44.02%)and restorers(41.20%)was basically the same,and the difference between maintainers and restorers was the smallest(2.03%). |
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