| Sorghum bicolorx Sorghum sudanense hybrids are annual gramineous forage crops with intergrated excellent parental traits.Their heterosis is especially prominent,but the molecular mechanism of the formation of the heterosis is not yet very clear.A great deal of scientific reports have proved that DNA methylation plays a vital role in hybrid vigor.To reveal the relationship between the heterosis of sorghum-sudangrass and DNA methylation,so as to predict its heterosis more effectively,and then provide a theoretical basis for for guiding the selection of its parents.In this paper,we used the NCII design to configure 36 hybrid combinations of sorghum-sudangrass,and then combined with the principal components and cluster analysis to comprehensively evaluate their agronomic traits,so as to screen out some combinations with strong superiority.After that,we used MSAP technique to explore the relationship between heterosis of strong dominant combinations at the seedling stage and DNA methylation.The main results are as follows:1.Based on the principal components and cluster analysis of 9 agronomic traits in a 2-year field trial of 36 sorghum-sudangrass hybrid combinations,we screened 7 strong-potential combinations with more comprehensive agronomic traits,namely 11Axred shell sudangrass,5A×21,5Axbrown shell sudangrass,8A×21 shell sudangrass,8Axbrown shell sudangrass,9Ax21,9Axbrown shell sudangrass.These materials can be applied in agricultural production after being validated by varieties.2.The total number of amplified fragments between the 7 superior sorghum-sudan-grass combinations and their parents was about the same.The hybrids and parent materials obtained 127 methylation sites on average,and the total methylation level ranged from 28.57%to 37.60%,and the average number of full methylation and semi-methylation sites were 106 and 21,respectively.The methylation levels ranged from 23.82%to 31.01%and 3.97%to 7.57%,respectively.The total methylation level of each hybrid material was consistently lower than that of its parents,and the full methylation model play a leading role compared with the semi-methylation model.3.The types of DNA methylation showed that the DNA methylation of sorghum-sudangrass is mainly based on type A(Maintaining the common type of methylation in both parents),type E(Demethylation type),which accounts for an average of 46.94%and 20.62%of the total methylation type,followed by C type(Maintain the parental methylation type),B type(Maintain the maternal methylation type),D type(Hypermethylation type)and F type(Other types),respectively.The average share was 11.94%,11.09%,6.79%and 2.99%,respectively.It is shown that the methylation type of hybrid F1 is mainly derived from the stable inheritance of both parents.4.Correlation analysis between DNA methylation level and agronomic traits and their heterosis showed that there was a significant negative correlation(-0.667*)between leaf length and total methylation level at seedling stage,but there was a very significant negative correlation(-0.757**)with the full methylation level.However,the overall performance is that the level of DNA methylation has a relatively weak correlation with the heterosis of agronomic traits.5.Correlation analysis between DNA methylation type and agronomic traits and heterosis showed that C-type methylation level was positively correlated with the mid-parent heterosis of leaf width and fresh-weight,while D-type methylation played an opposite role in mid-parent heterosis of fresh weight.It is shown that the specific type of methylation coordinated regulation of the formation of heterosis at the seedling stage. |
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