Preliminary Study On Self-incompatibility Of Rapeseed (Brassica Napus L.)

Cultivated Brassica napus(AACC,2n=38) is a self-compatible plant that arising from interspecies hybridization between two self-incompatible species,B.oleracea (CC,2n=18) and B.rapa(AA,2n=20).S haplotype is widespread in B.napus,but the molecular mechanism of self-compatibility is complicated and still unknown presently.In this study,S-1300,a B.napus self-incompatible line and 125 accessions collected from China and foreign countries were used as plant materials,in which the aim was to analyze the genetic control of self-incompatibility in rapeseed. Homology-based candidate gene method was used to develop molecular markers linked with self-incompatibility and to clone self-incompatibility genes.Distribution of S haplotypes and its relationship with the restorer-maintainer for S-1300 was also studied.The major results were as follows:1.Two F₂ populations and two BC₁ populations were generated from S-1300×Defender and S-1300×Yu No.9.All the plants and progeny from 86 plants were investigated for self-incompatibility/self-compatibility.The results suggested that self-incompatibility in S-1300 was under the single recessive locus control.2.One SCAR marker linked with self-compatibility and one CAPS marker linked with self-incompatibility were developed based on 7 primer pairs chosen from literatures about Brassica self-incompatibility.3.Based on homology-based candidate gene method,six dominant SCAR markers linked with S-locus were developed,of which three were completely linked with self-compatibility,and other three were totally linked with self-incompatibility. Two multiplex PCR markers were successfully developed which could discriminate all the three genotypes.No plant was found to be misclassified when multiplex PCR markers were used to marker-assisted selection for self-incompatibility/self-compatibility.4.S-locus was mapped to linkage group N7 of two B.napus linkage maps.5.SRK and SP11 fragments of S-1300 were cloned.The length of SRK-1300 was 5892 bp.This fragment was predicted to have 7 exons and 6 introns by GENESCAN.The length of SP11-1300 was 435 bp and showed high identity to classâ…¡SP11.S-I300 contained two classâ…¡S haplotypes,and the S haplotype in the A genome determined the self-incompatibility.6.SRK fragment and SLG of Defender were cloned.The length of SRK-Defender was 4281 bp,and was derived from classâ…¡S haplotype of B.oleracea.The length of SLG-Defender was 1336 bp,and was derived from classâ… S haplotype of B.rapa.Defender contained a classâ… S haplotype in the A genome and a classâ…¡S haplotype in the C genome.7.The evolution of three S-locus genes,SLG,SRK and SP11,were analyzed in Brassica.The phylogenetic analysis revealed that the divergence of classâ… and classâ…¡S haplotypes occurred first,and followed the divergence of S-locus genes, then Brassica specifics diverged.8.Self-incompatibility/self-compatibility of 125 F₁ from crossing S-1300 with 125 cultivated B.napus accessions were investigated.All the male materials were divided into two groups,restorers and maintainers.9.Two classâ… S haplotypes(S-â… _SLGa and S-â… _SLGb) and four classâ…¡S haplotypes (S-â…¡_SLGa,S-â…¡_SLGb,S-â…¡_SP11a and S-â…¡_SP11b) were identified in S-1300 and 125 accessions.S-â… _SLGa and S-â… _SLGb were derived from classâ… BrS-47 and BrS-21, respecitively.Both S-â…¡_SP11a and S-â…¡_SP11b were newly identified classâ…¡S haplotypes.S-â…¡_SLGa contained S-â…¡_SLGb derived from classâ…¡BoS-15.10.Eleven genotypes were grouped in S-1300 and 125 accessions.S-1300 had the specific genetype A^â…¡A^â…¡C^â…¡C^â…¡,A^â…¡was S-â…¡_SP11a and C^â…¡was S-â…¡_SLGa.There were six genotypes in restorers,and the most common genotype was A^â… A^â… C^â…¡C^â…¡,A^â… was S-â… _SLGa and C^â…¡was S-â…¡_SLGb.There were eight genotypes in maintainers,and the most common genotype contained two classâ…¡S haplotypes,S-â…¡_SLGb and S-â…¡_SP11b.Some genotypes were specific for restorers or maintainers,and there were some genotypes included both restorers and maintainers,which suggested the complicated self-incompatibility in B.napus.