Abstract:

To understand the mechanism of bud mutation in Malus × domestica Borkh.‘Fuji’，DNA methylation patterns and epigenetic variations were identified using MSAP（Methylation Sensitive Amplified Polymorphism）molecular marker analysis and UPGMA cluster analysis in a population of 35 ‘Fuji’bud sports lines（Red Fuji）. Results indicated that：(1) MSAP amplication pattern varied among different bud sports lines. Total methylation was ranged from 27.90% to 36.16%，and 32.87% in average. Inner-methylation of double-stranded DNA was the main pattern in a primary‘Fuji’cultivar and its bud sports lines. (2) The CCGG sites remained primary methylation patterns during the occurrence of bud sports together with‘Fuji’. (3) In total，12 methylation variation patterns were detected from 68.57% Red Fuji lines. The frequence of hypomethylation was significantly higher than that of hypermethylation. Moreover，CG hypomethylation was significantly higher than that of CHG（P < 0.01）. (4) Average similarity coefficience among 36 bud sports lines was 0.89，ranging from 0.79–0.92. In the UPGMA dendrogram，the primary Fuji cultivar fell out of the group of bud sports lines. Most recently bud spot lines had tendency to cluster together；typeⅠ（flushed-skin color pattern）and typeⅡ（striped-skin color pattern）bud sports lines were mixed into differents. In summary，DNA methylation and demethylation happened at the same time，demethylation was the main methylation pattern. CG hypomethylation plays an important role in the occurrence of Red Fuji. Our results would be great help in future epigenetic study of‘Fuji’sports lines，and CG hypomethylation would be as an emphysis to explore the mechanism of sports line occurence.

Key words: Malus ×, domestica Borkh.‘Fuji’, red color bud mutation, DNA methylation, methylation sensitive amplified polymorphism, epigenetic variation