Analysis Of Cytoplasmic Diversity In Brassica Napus L. And Diversity Of The A Genome In Brassica Crops

Brassica napus L.is an important oil crop in China as well as in the world.Nowadays,B.napus has a relatively narrow genetic background and a low genetic diversity.Thus it is of great importance to broaden the genetic background of B.napus.In this study,the cytoplasmic specific SSR primers developed by other researchers were employed to analyse the diversity of 181 B.napusaccessions,and SSR primers specific for the A genome of Brassica crops were used to study the A genome diversity of 68 tested accessions of B.naups,46 of B.rapa and 13 of B.juncea.The results are as follows:1.The study employed the multiple PCR technique and cytoplasmic specific SSR primers to analyse the cytoplasmic diversity of 181 B.naups accessions.The results of the multiple PCR showed that among the 181 accessions tested,110 accessions were found to be Nap cytoplasm type,52 to be Pol type and 19 to be Cam type.Of the 24 tested SSR primers,four pairs of chloroplast primers and one pair of mitochondrial primer successfully amplified 13 polymophic bands in total,with an average 2.6 bands per primer,ranging from 2 to 4.The PIC value ranged from 0.364 to 0.671 with a mean of 0.442 per locus.Totally,7 cyto-haplotypes were detected and named from BnHl to BnH7,respectively.There were three haplotypes detected in all the 19 Cam type materials distributed among 3 haplotypes,17 of them posessed BnHl.The 52 Pol materials contained 3 haplotypes and 50 of them posessed BnH2.One hundread and ten Nap type materials contained 3 haplotypes and 104 of them possessed BnH6.All the accessions were clustered into 2 groups.The first group contained all the materials with Cam type,51(98.08%)materials with Pol type and only 2 materials with Nap type.The second group contained all the remained 108 Nap accessions.This suggested that there is a more closer relationship between the Cam type and the Pol type materials,and both of them have a farther relationship with the Nap type2.Fifteen polymorphic SSR primers were screened out from 192 primers,and with them 58 polymorphic bands were amplyfied among the tested B.naup,B.rapa and B.juncea accessions,with an average 3.87 bands per primer,ranging from 2 to 7.The PIC value ranged from 0.173 to 0.831 with a mean of 0.567 per locus.All the accessions were clustered into 2 groups.The first group consisted of all the B.naups accessions,and the second group consisted of all the B.rapa and B.juncea accessions.The PCA analysis and the population structure analysis revealed the similar results with the cluster analysis.The result of molecular variance analysis showed that the percentage of variation among population was 36.86%and the percentage of variation within population was 63.14%.The Fst value between B.naups and B.rapa was 0.3491,between B.naups and B.juncea was 0.4192,and between B.rapa and B.juncea was 0.3645.This indicated that B.naups and B.juncea had a reletively high genetic variance.Our results suggested that there is more room to enrich the genetic diversity of B.napus by the use of B.rapa and B.juncea genetic resources.