| Rapeseed（Brassica napus L）is an allotetraploid species of Brassicaceae family.It is an important oilseed crop around the world and has various secondary uses.During the breeding history of rapeseed,more focus is given to improve yielding ability to meet the increasingly global demands for oil and other uses.As one of the three yield components,the number of seeds per silique（SN）largely determines the final seed yield,while the number of seeds per silique is directly associated with the number of ovules per ovary（ON）.The present study was carried out to dissect the genetic bases ON,SN and difference between ON and SN（ON-SN）.To understand the genetic basis of ON,SN and ON-SN,two inbreeding accessions（7-5 and ZY50）differing largely in SN and ON,were used to generate a set of biparental population consisting of 180 double haploid（DH）lines.The DH population and its parents were planted in 3 consecutive seasons（2015-2017）for phenotyping,and the data was integrated for QTL analysis.The main results are as follows.1,Phenotypic analysis showed that the DH population displayed a normal distribution and transgressive segregation for the observed traits（ON,SN and ON-SN）suggesting its suitability for QTL mapping analysis.ON has significant positive association with SN,while ON-SN was found to be negatively associated with SN.2,On the basis of the genetic linkage map constructed in our lab previously,which includes 2236 SNP and 66 SSR markers and covers a map length of 1951.5 cM with the average marker distance of 0.85 cM,we used the phenotypic data for QTL scanning.A total of 14 QTLs were identified for the three traits.Five QTLs were detected for ON,including qON-A3,qON-A7-1,qON-A7-2,qON-A10,qON-C6.Three of them,including qON-A7-1,qON-A7-2 and qON-A10,can explain the phenotypic variations of15.5%,17.38%and 9.28%,respectively,which seemed to be the QTL with major effects.Some QTL for two or three traits were observed to be co-localized,while others specific for one trait were independently distributed,suggesting that these QTL underlying genes may be involved in seed number regulation in different approaches.3,To further characterize the three QTL（qON-A7-1,qON-A7-2 and qON-A10）for ON,the DH lines individually carrying these QTLs were crossed to the corresponding parents towards constructing the near-isogenic lines for these QTLs.Presently,we have got the BC3F1 generation for qON-A7-1 and qON-A7-2,and the BC1F1 plants for qON-A10 independent QTL.In summary,we presented the preliminary findings for genomic loci controlling the primary determinants of seed yield.The results from our study will help to resolve the genetic control of ON and the SN and will contribute to the understanding of genetic regulation of rapeseed plant yield. |
