Analysis Of Quantitative Genetics And The Genes Related To High Linolenic Acid Trait In Brassica Napus L.

Enhancing the nutritional value of fatty acids is the main goal of rapeseed quality improvement,and the three fatty acids(oleic acid,linoleic acid and linolenic acid)rich in canola can be further optimized and adjusted.It was advocated to reduce the proportion of linolenic acid in the past because it was thought that the unsaturated bonds of linolenic acid are easy to oxidize,which was not conducive to the storage and cooking of edible oil.However,in recent years,various important nutrition and health effects of linolenic acid have been discovered and improving linolenic acid as a new breeding direction.In this study,breeding lines R8Q10 and YH25005 with 15%-20% linolenic acid,which were selected by our research group,were used for quantitative genetic analysis,cloning of FAD2 and FAD3 genes in linolenic acid biosynthesis pathway,fluorescence quantitative PCR,and transcriptome sequencing to clarify the genetic and molecular mechanism of the formation of high linolenic acid rapeseed germplasm,so as to lay a foundation for guiding high linolenic acid breeding.The main results are as follows:1.Through the analysis of the genetic separation model of ‘combined major gene +polygene’ in different generations of the cross between the high and low linolenic acid lines,the optimal genetic model of R8Q10×SW and YH25005×SW for linolenic acid are inaccordance with two pairs of additive major gene + additive dominant polygene,but the genetic effect of polygene are greater than that of the major gene,indicating that the minor-effect polygenes have a greater contribution to the linolenic content of Brassica napus L.It is necessary to accumulate minor-effect genes to obtain higher linolenic acid.2.In the analysis of related genes FAD2 and FAD3,the fluorescent quantitative expression results showed that the expression levels of FAD2 and FAD3 in high linolenic acid strains were significantly up-regulated than those with lower linolenic acid.Partial results of cloning and sequencing showed that,FAD2 of high linolenic acid R8Q10 and YH25005 had no significant amino acid difference compared to the ordinary rapeseed JA177.There are intron and exon mutations in several copies of FAD3 which we cloned,resulting single amino acid differences.Mutation by A For T in the 478 th nucleotide downstream of start condon ATG,in CDS of C.FAD3.c-R8Q10 and C.FAD3.c-JA177 and the corresponding amino acid at position 160 mutate from N(asparagine)to I(isoleucine).For the c DNA sequencing of A.FAD3.b,2 and 3 clones of R8Q10 and YH25005 respective,nucleotide at position 814 is mutated from T to C,and the corresponding amino acid is atposition 272 from C(cysteine)to R(Arginine).3.The transcriptome of the seeds 24 days after pollination of high linolenic acid lines R8Q10 and YH25005,low linolenic acid line A28,and low linolenic acid and high oleic acid line SW,were sequenced and a total of 84.19 Gb clean data was obtained.Transcriptome comparison results show that elevated expression of some genes encoding transcription factors such as FUS3 and NF-YC in R8Q10 and YH25005 seeds may be one of the reasons for the increase of FAD3.