| Heterosis refers to the phenomenon that two varieties with independent genetic backgrounds are hybridized as parents,and the F1 activity and main characteristics of the hybrid obtained are superior to those of their parents.These characteristics mainly include increased biomass,increased yield,and enhanced stress resistance.Although the mechanism of heterosis formation is not yet clear,it has been widely used in crops such as corn and rice,and the yield has also been significantly improved,making a significant contribution to global food security.However,the utilization of heterosis is limited to F1 generation.Due to the phenomenon of character segregation in F2 and later generations,it is necessary to produce seeds every year to utilize heterosis,while farmers also need to purchase hybrids every year This not only increases labor costs but also increases production costs,making it even more urgent to explore pure line varieties with heterosis.In this experiment,XiNong585 and CunMai16,which have excellent comprehensive traits such as yield,were used as parents to cross to obtain F1.Through continuous selfing of the hybrid and artificial selection with the main goal of 1000 grain weight,until F5 generations obtained a pure line with stable target traits and similar F1 heterosis,which is called Hybrid Mimics.By investigating the similarity of agronomic traits between the hybrid simulation line and hybrid F1,and transcriptome sequencing analysis,the gene expression basis between the simulation line and F1 at 15 days after anthesis was explored.The main experimental results are as follows:1.In terms of main agronomic traits,the selected hybrid simulation line Mimic 1 showed no significant differences in population yield,thousand grain weight,plant height,ear length,and other agronomic traits compared to the hybrid F1,while the number of grains per ear was significantly higher than that of F1;Mimic2 is significantly higher in 1000 grain weight than F1,while there is no significant difference in other agronomic traits compared to F1;The performance of the hybrid simulation weak line Small in population yield,thousand grain weight,and plant height is weaker than F1,and even lower than the low parent value.2.In terms of grain traits,there is a significant positive correlation between grain width and thousand grain weight,and the hybrid simulation lines Mimicl and Mimic2 have a super parental advantage in grain width,which is superior to the hybrid F1.3.In terms of grain filling characteristics,the growth pattern of the studied varieties(strains)during grain filling period shows an "S" curve;There is a significant positive correlation between the average filling rate and the thousand grain weight in the filling parameters.The performance of hybrid simulation lines Mimic1 and Mimic2 in average filling rate is similar to that of F1,both showing a certain degree of hyperparent advantage;However,Small’s performance in average grain filling is weaker than that of its lower parent resulting in a hybrid disadvantage.4.In the transcriptome analysis:(1)In terms of gene expression pattern similarity the gene expression pattern similarity between hybrid F1 and female parent Xinong 585 is higher than that of male parent Cunmai 16;The similarity of gene expression patterns between hybrid simulation lines Mimicl and Mimic2 and the female parent is higher than that of F1;The similarity of gene expression patterns between the vulnerable strain Small and F1 is higher than that of Mimicl and Mimic2.(2)In terms of the number of differentially expressed genes,compared to the median relative value(MVP),F1 has the least differentially expressed genes,while Small has the highest differentially expressed genes;There are a total of 32 differentially expressed genes shared by F1,Mimicl and Mimic2.(3)In gene function annotation and enrichment analysis,the GO annotation results of differentially expressed genes Mimicl and Mimic2 relative to the median MVP were similar to those of F1,while the GO annotation results of differentially expressed genes Small relative to MVP were more than those of F1;In the analysis of KEGG enrichment in biological metabolism,it was found that the hybrid simulation lines Mimicl and Mimic2 share three sucrose metabolism pathways with F1;The number of differentially expressed genes in the starch and sucrose metabolism pathway of Small is 60,significantly higher than the simulated lines Mimic1 and Mimic2. |
