Genetic And Molecular Biology Research On The Especially-long Pod Of Artificially Resynthesized Rapeseed (Brassica Napus L.)

Artificially resynthesized Brassica napus lines are the genetic resources of creating new germplasm, as well as obtaining more significant agronomic and economic characteristics of Brassica napus L.. With the help of resynthesis technologies, we can transform some beneficial traits of relative species into Brassica napus L., accordingly, the hereditary basis of rapeseed can be expanded, and the agronomic and economic characteristics of rapeseed can be modificated. A population of new rapeseed materials which are rich in genetic variation has been created by resynthesis technologies in Rapeseed Research Center of Sichuan Agricultural University. A lot of excellent metamaterials were selected from the population, such as specially-long pod Variant Line, high 1 000-grain weight line, multiple-branch line, and big pod, big seed line. In this study, in order to study the formation reasons of long-pod rapeseed, quantitative genetic analysis of specially-long pod resynthesized Brassica napus line H218 was investigated by the methods of molecular biology technologies such as GISH(Genomic in Situ Hybridization) and DNA methylation. The main results of the research are as the follows:1. The broad-sense heritability of whole-fruit length and fruit length are relatively higher than narrow-sense heritability in specially-long pod Brassica napus line H218, and narrow-sense heritability are significantly higher than the difference between broad-sense heritability and narrow-sense heritability, indicating that the contribution of additive effects to phenotype is much higher than non-additive effects. The broad-sense heritability and narrow-sense heritability of the length of beak are both lower, indicating that the ratio of heredity is lower. The whole-fruit length is controlled by at least five genes, the fruit length is controlled by at least six genes, the length of beak is controlled by at least two genes. In F2 population, the whole-fruit length, fruit length and the beak length are normal distribution, demonstrate that they are quantitative genetic traits controlled by multiple genes. The correlation analysis on F2 population indicated that they are significant positive between whole-fruit length and fruit length, beak length, the grains on each pod, fruit length and beak length, the grains on each pod. It means that select whole-fruit length can improve fruit length indirectly, selecting long pod trait can improve the grains on each pod indirectly.2. Genetic effects were analysed and genetic models were tested by the method of generation means analysis, the results showed that the whole-fruit length, the fruit length and beak length are not conform to simple additive-dominant-epistasis genetic model, but conform to [d]+[i]>[h]+[l], which suggests that the three traits are mainly behaved as additive effects, and it is hard for them to behave heterobeltiosis in F2 generation. The result of [d]+[h]>[i]+[j]+[l] suggests that the additive effects, dominant effects contribute more to phenotype variance than epistasis effects. The additive effects [d] of the three traits, the interaction effects between additive effects and additive effects [i] are showed as significant and positive, which proved that the genes of all the three traits are joint probability distribution. As far as the three traits are concerned, the sum of squares of additive effects are higher than that of the dominant effects, in different hybridized combination, the contribution of gene effects to total genetic variance are similarly, additive genetic variance contribute more than 80% to total variance, and additive is the main factor to genetic variance between generations. Dominant effects, epistasis effects also contribute to total genetic variance.3. TTC analysis was carried out on specially-long pod Brassica napus line H218, when it comes to the three traits, theχ2 value of I, I1,I2 were significant, which proved that there exist significant epistasis effects. Between the families, the sum, the difference, the sum and difference of the three traits showed as extremely significant differences, and the interaction models of i, j,l are all extremely significant differences, which suggest that three different of genes cooperate to each other, and result in three different traits, it also conform to additive-dominant-epistasis genetic model.4. Analysis especially-long pod Brassica napus line H218 with the model of main gene-multiple genes, C model is the best for whole-fruit length and fruit length, it also means that they are controlled by additive-dominant-epistasis multiple genes, no main gene effects was founded, it suggest that collect enhancin gene by recurrent selection, or transform these multiple genes by convergent backcross method can effect the whole-fruit length and fruit length. Heritability of multiple genes in B1, F2 population are relatively higher than B2 population, and genetic parameters are different based on hereditary background difference. The genetic model and genetic parameters of beak length are different based on different hereditary background.5.540 pairs of SSR primers are screened between especially-long pod H218 and Zhongyou 821,115 pairs of which showed difference, make use of the 115 pairs to screen between long pod gene pool and short pod gene pool in F2 population,3 pairs of primers showed difference, that is A05,J35,N05,which suggest that the three pairs of primers linked with pod length trait. Through software analysis, there are no linkage relationship among the three markers, t test was carried out by single marker analysis, and the result suggest that it is possible that markers A05 and N05 linked with QTL of length controlled, but not for J35.6. The total methylation ratio of long pod is lower than normal pod, the methylation ratio of long pod is lower than normal pod, the half methylation ratio of long pod is lower than normal pod, that is to say, the methylation ratio of long pod is lower than that of normal pod. Demethylation and submethylation level of especially-long pod rapeseed are higher than normal pod length rapeseed, total methylation, half methylation, super methylation level of normal pod length are higher than that of especially-long pod.7. Use genome DNA of B campestris L. as probe, chromosome of different Brassica napus L. as blocking DNA, especially-long pod rapeseed H218 performed higher homology with Brassica campestris L. than normal pod, which means the eapecially-long pod may has something to do with the transformation of special genes from Brassica campestris L.. Use genome DNA of Brassica oleracea var.alboglabra as probe, chromosome of different Brassica napus L. as blocking DNA, especially-long pod H218 performed higher homology with Brassica oleracea var.alboglabra than normal pod, which means the eapecially-long pod trait may has something to do with the transformation of special genes from Brassica oleracea var.alboglabra. In resynthesized Brassica napus line H218, special genes from Brassica campestris L. and Brassica oleracea var.alboglabra interact with each other, then formed especially-long pod, and can inherit stably to the next generation.