Abstract: 【Objective】 The differences of the firmness, fracturability, contents of aroma components and expression of softing relevant genes during later-developing stage of fruit between ‘Jonagold’ and its bud mutation were studied to completely understand the mechanism of a crisp-fleshed bud mutation of ‘Jonagold’ apple. Furthermore, these results will be beneficial for perfecting the theoretical system of the quality development of fruit texture. 【Method】 The fruits of ‘Jonagold’ apple variety and its crisp-fleshed bud mutation during later-developing stage were used. Some physiological index, such as the content of firmness, fracturability and aroma components, and the expression of genes participating in ethylene synthesis (ACO,ACS) and fruit softing (PG, PME, β-Gal, α-L-Af, XET, AM,LOX and β-xyl) were measured. 【Result】 The firmness and fracturability of the fruits of ‘Jonagold’ apple and its crisp-fleshed bud mutation during later-developing stage were decreased in general, especially 50-35 d before harvest. The firmness and fracturability of bud mutation were much higher than ‘Jonagold’. The species numbers and contents of ester compounds of ‘Jonagold’ apple were 1.5 times and 1.2 times of bud mutation, but the content of alcohols and aldehydes of ‘Jonagold’ apple were 15.1% and 14.3% of bud mutation; the expression of ACO changed very greatly during the development of ‘Jonagold’ fruit, while the expression of ACS and ACO changed little in the bud mutation, which were 73.9% and 1.1% of ‘Jonagold’ , and the expression peaks of bud mutation lagging behind ‘Jonagold’. In ‘Jonagold’ fruit, the expressions of PG, PME, β-Gal, α-L-Af, XET, AM,LOX and β-xyl during 113-120 d after fullbloom were all over 35% of the total expression, which were the main reasons of the firmness and fracturability declined rapidly; while the total expression of 12 genes measured, the bud mutation was 23.2% of ‘Jonagold’, which PG,α-L-Af, XET and β-Gal was 12.5%, 62.7%, 72.6% and 75.3%, respectively. 【Conclusion】 The species numbers and contents of ester compounds were higher in the fruits of ‘Jonagold’ apple than in its bud mutation, while the species numbers and contents of alcohols and aldehydes were opposite. The difference of the firmness and fracturability of the fruits of ‘Jonagold’ and its bud mutation during later-developing stages may be the results of synergistic effects of ACS, ACO, PG, β-Gal, β-xyl , a-L-Af and XET genes, among them, ACO, PG, β-Gal and XET may be the key genes.

Key words: ‘Jonagold&rsquo, apple , crisp flesh sport , texture , gene expression , aroma components