Study On Molecular Mechanism Of Heterosis Of Chinese Fir (Cunninghamia Lanceolata (Lamb.) Hook)

There is an obvious heterosis in the intraspecific hybridization of Chinese fir, and the performance of hybrid combinations is closely to the component of parents'combining ability and the action mode of them, but this is unclear of the molecular mechanism of heterosis of F1 hybrids. To reveal the molecular basis of heterosis and the modification at genetic and epigenetic regulation level of Chinese fir was one of the main intentions. The main results are as follows:1. Significant phenotypic differences were found among the F1 hybrid combinations of Chinese fir for most of the growth characteristics; positive and negative heterosis was measured in all of the characteristics. Significant general combining ability as wel1 as maternal effects were obtained.But specific combining ability,male effects,specific reciprocal effects seem to be negligible. SCA effecting was significantly positive correlation with heterosis.2. The correlation coefficients between GD and heterosis of growth and wooden traits of F1 hybrids were all not significant. The correlation coefficients between average GD and general combining ability, maternal effecting, paternal effecting of four characters for each parent were all significant.3. About 22.45% of the 5'-CCGG sites in the genome of Chinese fir were in methylation. The cytosine methylation patterns between hybrids and their parents were compared, extensive cytosine methylation alterations including hype-and demethylation as well as the potential conversion of methylation types occurred in the hybrid compared with the parents; the demethylation loci that occurred in cross sha36×sha21 were greater than those sha21×sha36.4. The inner-methylation of double-stranded DNA was the main pattern of the genomic DNA methylation on Chinese fir. The methylation percentage at CCGG sites among the six crosses was significantly lower than their parent's selfing. There were significantly negative correlation between both the inner methylation of double-stranded DNA, outer methylation of single-stranded DNA patterns and the heterosis.