| Rapeseed is an important oil crops, the understanding of the genetic diversity of rapeseed germplasm resources is the basic of genetic improvement of varieties. However, the genetic similarities of resources of china have not been clearly known, which influenced the fully utilization of the germplasm resources. Heterosis of rapeseed has been widely used in production. However, study of heterosis prediction and parental selection is still needed. Seed oil content (OC) and silique traits are the main aim of high yield breeding in rapeseed. However, the genetic basis and effective way of heterosis untilization of these traits have been rarely known. Study of the genetic diversity of germplasm resources, heterosis prediction, parental selection and genetic of silique traits and OC will be helpful for the utilization of heterosis and high yield breeding.This study analyzed the genetic diversity and characters of regional and breeding unit of 96 germplasm resources that collected from breeding unit of 12 provinces of china. A 6×6 incomplete diallel crosses were designed, and the inheritance of 10 yield related traits and OC were analyzed through field experiment of 4 environments in 3 years. The effect of genetic distance (GD), general combining ability (GCA), specific combing ability (SCA), methylation levels and parental performance for heterosis prediction, and the possibility of application of maternal and paternal inheritance for parental selection in hybrid breeding were analyzed. Furthermore, a F2:3 population was constructed for QTL mapping of silique traits and OC. The inheritance of silique traits and OC were analyzed, and candidate gene prediction, candidate gene cloning, molecular markers closely linking with the pleiotropic QTL were carried out. The main results are as follows:1. In the 96 germplasm resources, resources of the same province showed a higher genetic similarity, and the genetic diversity of resources of Hubei province showed the highest in the 12 provinces.2. Seed yield per plant (SY) showed the highest heterosis levels (26.07%), and SY of hybrid had higher environment adaptability than parens (environment variance was not significant). Heterosis showed significant potential for every trait (positive direction of heterosis levels). Through the analysis of inheritance of traits, all of the traits showed significant additive effect, except a significant epistasis effect of SY.3. Significant correlations were only detected between GD and heterosis of primary branch nubber (PBN) and thousand seed weight (TSW). Significantly correlats were detected between combining abilities and heterosis for all of the traits, except for the GCA of mainly inflorescence length (MIL) and seeds per silique (SS). Performance of F1 and parental lines, F1 and mean of parental lines of all the traits were detected to be significant correlated, except plant height (PH) of maternal parents. The variance of methylation levels of parents and heterosis of SY, MIL, mainly inflourescence siliques (MIS), SS, silique length (SL), and siliques per plant (SP) were found to be significantly correlated. These results revealed that heterosis could be predicted by combining abilitis and performance of parents, combined with GD and variance of methylation levels of parental lines.4. Through the analysis of variance of contribution ratio of combining abilities of parents and relationship of heterosis and conbining ability, paternal and maternal effects were detected in the heterosis inheritance. The results showed that TSW, SS, SL, OC, MIL, primary branch height (PBH), PBN, and MIS were primary controlled by the maternal parents, PH, SP, and SY were primary controlled by the paternal parents. Parents of hybrid could be selected through maternal and paternal effect.5. MIL and MIS was only detected to be significantly correlated in the parents. SY and OC, SP and OC, SY and SL were only detected to be significantly correlated in F1. However, SY and SP, OC and SL, OC and SS were detected to be significantly correlated in both F1 and the parents, which revealed that SY could be improved assisted by silique traits in hybrid.6. Through QTL mapping of silique traits and OC of 2 environments in a F2:3 population,26 QTL were detected, and 4 of which were first identified. Five pleiotropic QTL of silique traits and OC were detected. SS was mainly controlled by over dominant, SL was mainly controlled by partial dominant and epistasis, TSW and OC were mainly controlled by partial dominant and over dominant. No significant interaction was detected between environment and traits.7. Sixteen candidate genes were predicted for the 5 pleiotropic QTL. Two of the three cloned candidate gene had amino acid mutation at conserved region. The InDel markers designed for the pleiotropic QTL were found to be correlated with SS and TSW in a population consisted by 90 germplasm resources. |
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