| At present in the apple production of China, diploid varieties play a major part, but a few triploid varieties have good performance. The triploid apple breeding has become an important part in fruit polyploid breeding. But there was very little research on that had obtained polyploidy resources by hybridization, and also very few reports of hybrid mutation mechanism. Especially, the molecular mechanism of genetic variation of triploid apple obtained by crossing has rarely been reported. In this study, molecular mechanism of genetic variation and epigenetic variation in genome including the status and patterns of DNA methylation based on the investigation of the botanical characters of triploid hybrid progenies of ’Hanfu’×’4xGala’,’Fuji’×’4xGala’,’Golden Delicious’×’4xGala’ were studied, and the results are as follows:1. The coefficient of variation of leaves, branches and flowers of triploid hybrids of ’Hanfu’×’4xGala’ were among26.42%～1.33%and that of pollen PE was4.46%. The averages of most of the characters were lower than that of the mid-parents. Coefficient of varation of fruit characters were among5.12%～27.82%, and the same trend with the botanical characters. Characteristic aromas of6hybrids were effect by both parent, and the genetic trend of fruit aromas was paternal inheritance. The major effect factor on the sweetness of6triploid hybrids was fructose, and that of sour flavor was malic acid.2. Genetic variation of7triploid hybrids o f’Hanfu’×’4xGala’ was investigated based on ISSR and AFLP. The percentage of polymorphic bands (PPB) of ISSR was60.00%, observed number of alleles (Na) was1.6000, effective number of alleles (Ne) was1.4204, Nei’s gene diversity (H) was0.2368and Shannon’s Information index (I) was0.3464. And these were lower than that of AFLP. The UPMGA cluster showed that most of7triploid hybrids were tend to the female parent’Hanfu’based on ISSR and AFLP. The analysis indicated that ISSR and AFLP both can use to analyze the genetic diversity of apple triploid hybrids, and these triploid hybrids were maternal inheritance.3. Genetic variation of29triploid hybrids of ’Fuji’×’4xGala’ was investigated based on ISSR. The percentage of polymorphic bands (PPB) was77.42%, observed number of alleles (Na) was1.7742, effective number of alleles (Ne) was1.4004, Nei’s gene diversity (H) was0.2355and Shannon’s Information index (I) was0.3574. Genetic variation of61triploid hybrids of ’Golden Delicious’×’4xGala’ were investigated based on ISSR. The percentage of polymorphic bands (PPB) was36.55%, observed number of alleles (Na) was1.9655, effective number of alleles (Ne) was1.5322, Nei’s gene diversity (H) was0.3092 and Shannon’s Information index (I) was0.4641. In the80triploid hybrid progenies, the bands of hybids were most come from female parent, and there was a certain increase and deletion in the strips, and these triploid hybrids were maternal inheritance.4. The total methylation ratios of7triploid hybrids of ’Hanfu’×’4xGala’ were among14.74%to20.00%, the full methylated ratios were among5.41%to10.38%, and the hemi-methylated ratios of that were among5.85%to14.59%. Compared with ’Hanfu’, the total methylation ratios, the full-methylatied ratios and hemi-methylated ratios were mostly tended to increase. But all of that were tended to decrease compared with’4xGala’.There was no obvious trend with that of their parents. The total methylation ratios of29triploid hybrids of ’Fuji’×’4xGala’ were among14.65%to27.96%, the full methylated ratios were among8.25%to17.40%, and the hemi-methylated ratios of that were among4.19%to10.82%. Compared with ’Fuji’, the total methylation ratios and hemi-methylatied ratios were mostly tended to increase, but full methylated ratios was tended decrease. But all of that were tended to decrease compared with ’4xGala’. The total methylation ratios of61triploid hybrids of ’Golden Delicious’×’4xGala’ were among10.74%to28.86%, the full methylated ratios were among7.84%to24.22%, and the hemi-methylated ratios of that were among2.10%to11.84%. Compared with ’Golden Delicious’, the total methylation ratios and the full-methylatied ratios were mostly tended to increase, but hemi-methylated ratios was tended decrease. But all of that were tended to decrease compared with ’4xGala’.5. There were five patterns of DNA methylatiion in these three hybridized combinations including monomophism (A), demthylation (B), hyermethylation (C), hypomethylation (D) and intermediate methylation (E).During the process of genome recombination and triploidization in apple triploid hybrids, a great number of hypermethylations and demethlation were occurred, a small amout of occurrence methane phenomenon and a very small part of the methylation status were between parents. In total10differential fragments were obtained by MSAP.8can be detected in the apple genome, and the high homology fragments were located in the contig of8,9,10,12and16chromosomes, but the specific function is not described. |
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