Study On The Relationship Between Genetic Variation Of DNA Methylation And Heterosis In Soybean Immature Grains

In this paper,3 soybean materials including Jilin 38(NO.3),Yi 3(NO.6)and Jilin 47(NO.19)were used as parents,and 6 hybrid combinations were obtained by field hybridization according to Griffing complete diallel crosses design.Using 3 parents and 6 hybrid combinations as experimental materials,through the study of traits and the technology based on MethylRAD,the level of methylation and the situation of inheritance and variation were tested to explore the correlation between DNA methylation of soybean immature grains and soybean heterosis.The results were as follows:1.Among the 6 hybrid combinations,all 12 traits were analyzed,3 and 6 reciprocal combinations had the strongest MPH and BPH,6 and 19 reciprocal combinations had the weakest MPH and BPH,3 and 19 was in the middle.Among all 12 traits,the strongest MPH traits were the number of branches,the number of seeds per plant,the weight per plant,and the number of pods per plant;the weakest MPH traits were the insect infected grain rate,plant height,bottom pod height and 100-grain weight;the medium MPH traits were stem diameter,number of nodes,at and protein.The law of the BPH was similar to the MPH,except that the order was slightly different.According to the appearance of various traits,the heterosis of 6×3 combination performed the best.2.The DNA methylation level and the situation of inheritance and variation of immature grains of soybean were analyzed.It was found that the DNA methylation levels of 9 materials were high and there were differences.The methylation variation can be divided into three categories: Class A was parental demethylation and progeny methylation(18.33%-28.73%);Class B was parental methylated and progeny demethylation(18.38%-27.12%);Class C was that both the parents and the offsprings were methylated,but there were differences in methylation levels(52.59%-58.54%).3.The site number of methylation and methylation levels of the hybrids with strong heterosis combinations were generally between two parents,and the site number of methylation and methylation levels of the hybrids with the medium heterosis combinations were lower than those of two parents.Among weak heterosis combinations the sites number of methylation of the hybrids were lower than those of two parents,and the methylation level were lower than the parents at the CCGG site,but higher than the parents at the CCWGG site.Thus,the number of methylation sites between two parents was beneficial to improve heterosis,and hybrid methylation levels above the parent at CCWGG sites may result in reduced heterosis.4.DNA methylation of soybean immature grains had a certain relationship with heterosis,but only a few related significant or extremely significant.From the point of view of the MPH,the Class B had a highly significant negative correlation with the height of the bottom pod,and had a significant negative correlation with the number of nodes and stem diameter.From the BPH,the Class A had a significant positive correlation with the height of the bottom pod,and the grain weight reached a highly significant negative correlation with class A.Class B was highly significantly negatively correlated with the number of nodes,and was significantly negatively correlated with the height of the bottom pod and the stem diameter.