Abstract:In this study, the full red fruits of six big fruit type Ziziphus jujuba Mill. varieties (‘Junzao’, ‘Zanxindazao’, ‘Jingudazao’, ‘Hamazao’, ‘Jinzandazao’ and ‘Xinzhengdamaya’) cultivated in Xinjiang were used as research objects. We observed the pericarp tissue structure, measured the cell wall components and metabolismrelated enzyme activities, analyzed the changes in the expression of extension protein genes. And then, we analyzed the fruit cracking difference of them. In order to find the internal regular pattern that causes the fruit cracking difference. The result might be providing a theoretical basis for the cultivation and introduction of varieties resistant to fruit cracking. The results showed that: (1) ‘Junzao’, ‘Zanxindazao’, and ‘Jingudazao’ are the fruit cracking varieties, while ‘Hamazao’, ‘Jinzandazao’ and ‘Xinzhengdamaya’ have better fruit cracking resistance. (2) The cuticle thickness of the six varieties were significantly different from each other, and ‘Jinzandazao’, ‘Hamazao’ and ‘Xinzhengdamaya’ were larger than others. while the epidermal thickness was not different. There were significant differences in the cavity/pulp area rank from low to high, which were ‘Hamazao’ < ‘Xinzhengdamaya’ < ‘Jinzandazao’< ‘Junzao’ < ‘Jingudazao’ < ‘Zanxindazao’. (3) The contents of cellulose, protopectin, soluble pectin, and the activities of cellulase and pectin were all different among the six cultivars. Among them, the content of protopectin in crack resistant cultivars ‘Jinzandazao’, ‘Hamazao’ were significantly lower than that of other cultivars, this means that there is a correlation between the propectin content and the cracking rate. While the change trend of cellulose content and cellulase activity is basically constant, so there no correlation was found between the other indices and their cracking rates. (4) The expression levels of ZjEXP11 and ZjEXP12 in the pericarp of the fruit cracking resistance varieties were significantly lower than those in the fruit cracking varieties. Therefore, this study speculated that the expression level of ZjEXP11 and ZjEXP12 in the pericarp were correlated with the fruit cracking. In summary, There are significant differences in fruit cracking of Xinjiang big fruit type jujube among cultivars. compared with the cracking sensitive cultivars, the cracking resistant cultivars had thicker cuticle and epidermal layer, smaller pulp cavity area, lower propectin content and lower expression level of ZjEXP11 and ZjEXP12.