Screening Of Candidate Genes For Traits Related To Seed Test Weight And QTL Mapping Of Pod Related Traits In Brassica Napus L

The number of siliques per plant,the number of seed per silique(SPS)and the thousand seed weight(thousand seed weight,TSW)are the three major components affecting the yield of Brassica napus L.,while TSW is mainly affected by the seed volume(seed volume seed volume,SV)and the degree of seed filling(test weight test weight,TW).TW is one of the main components of TSW,which can reflect the accumulation capacity of photosynthetic products in seeds to a certain extent and has a certain degree of influence on improving crop yield.As the main site of photosynthesis in rapeseed seeds,the traits associated with TW also have an important impact on seed quality.Over the years,studies related to TW-linked QTL have mainly focused on wheat and maize crops,while only a few studies related to TW in oilseed rape have been reported.Dissecting the genetic basis of seed weight can not only deepen our understanding of seed development,but also improve the breeding efficiency of oilseed rape and provide an important theoretical basis for other researchers to conduct high yield and quality research in oilseed rape in the future.In this study,a total of 186 lines of the Brassica napus L.RIL population were used for the following analyses:(1)correlation analysis and QTL localization for TW,TSW and SV in four consecutive years;(2)transcriptome analysis of SNP183(large TW seeds)and SNP64(small test weight,TW seeds)seeds at 20 d,30 d and 40 d in 2020-2021;(3)(3)Combining QTL localization and RNA-seq to screen candidate genes associated with the Brassica napus L.TW and its component traits(TSW and SV);(4)Performing transcriptomic analysis of silique length(SL),silique width(SW),seed density(SD),grain filling rate(GFR),seed photosynthetic area(SPA),and Number of seed per silique(SPS)were QTL localized and correlated with TW and its component traits(TSW and SV)to explore their association,and the following conclusions were drawn.1.The correlation analysis of TW and its constituent traits(TSW and SV)in the Brassica napus L.RIL population for four consecutive years showed that TW was significantly positively correlated with TSW at the 0.01 level,and the relationship with SV was unstable due to the influence of environment;TSW and SV were both significantly positively correlated at the 0.01 level for four consecutive years,indicating that in the kale RIL population,increasing TW or SV is expected to increase the yield of Brassica napus L.by increasing the size of TSW.2.By QTL localization analysis of TW and its component traits(TSW and SV),a total of 30trait-associated QTL were localized in this study,distributed on 13 chromosome,A01,A02,A03,A05,A06,A07,A09,A10,C01,C03,C04,C07 and C08,explaining 2.31%-15.61%,including 6QTL associated with TW,9 QTL associated with TSW and 15 QTL associated with SV.3.9080(5526 up-regulated,3554 down-regulated),7677(4315 up-regulated,3362down-regulated)and 10481(6243 up-regulated,4238 down-regulated)differences were screened at20 d,30 d and 40 d,respectively,by transcriptome sequencing(RNA-seq)analysis of seeds from three periods of SNP183 vs SNP64 in the Brassica napus L.RIL population.4238 down-regulated)differentially expressed genes(DEGs),indicating that the development of rape seeds was mainly regulated through up-regulation of genes;by performing GO and KEGG analysis,DEGs in the three periods were mainly regulated through participation in metabolic pathways such as starch and sucrose metabolism,tryptophan metabolism,glyoxylate and dicarboxylic acid metabolism and carbon metabolism.4.Combining QTL localization and RNA-seq analysis,a total of 135 trait-associated candidate genes were screened,including 45 candidate genes associated with TW,20 candidate genes associated with TSW,and 99 candidate genes associated with SV,which are mainly involved in the seeds through encoding transcription factor families(WRKY,ARF and NAC,etc.),enzymes and hormone-responsive proteins.5.The correlation analysis of silique related traits with TW and its component traits(TSW and SV)in the three periods showed that TW showed some positive correlation with SL at the late stage of silique development,GFR had the greatest effect on TW at 30 d-40 d,and SW,SD,SPA and SPS had little effect on TW.TSW had positive correlation with SL,SW,SD,GFR and SPA to varying degrees,while TSW had positive correlation with SL,SW,SD,GFR and SPA.The relationship between SV and silique related traits and the relationship with TSW maintained some uniformity,but the effect of GFR on SV showed significant positive correlation in all three periods and reached highly significant positive correlation at 20 d-30 d and 30 d-40 d.The TW of Brassica napus L.seeds was mainly influenced by SL and GFR at the later stages of development,indicating that the larger the "bank",the larger the seed filling,and the more likely to get large TW seeds.6 By QTL localization analysis of silique related traits,a total of 33 trait-linked QTL were located,which were distributed on 10 chromosome,A03,A05,A06,A07,A08,A09,C01,C04,C08 and C09,and could explain 3.91%-31.81% of the phenotypic variation,among which 7 QTL were associated with SL,5 QTL were associated with SW and 5 QTL were associated with SD.7 QTL associated with SL,5 QTL associated with SW,6 QTL associated with SD,1 QTL associated with GFR,9 QTL associated with SPA,and 5 QTL associated with SPS.