Characteristics of chilling injury-induced lignification in kiwifruit with different sensitivities to low temperatures

The extent of chilling injury (CI) of kiwifruit varies greatly among cultivars. The characteristics of CI-induced lignification and the effects of 1-methylcyclopropene (1-MCP) on CI of kiwifruit has been studied on Actinidia chinensis var. chinensis 'Hongyang' and A. chinensis var. deliciosa 'Xuxiang'. 1-MCP delayed and reduced the CI proportion of the subcutaneous flesh. CI-induced lignification was mainly concentrated in the flesh of 'Hongyang' fruit, but in the core of 'Xuxiang'. The lignified cells were formed by the deposition of lignin particles on the inside of the cell wall. The accumulation of lignin in the flesh of both cultivars was decreased after treating with 1-MCP, but the more serious lignification was observed in core tissues, especially those of 'Xuxiang'. Activities of phenylalanine ammonia-lyase (PAL), cinnamyl alcohol dehydrogenase (CAD), and peroxidase (POD) involved in lignin synthesis were analyzed. 1-MCP increased PAL and POD activities in both flesh and core tissues of the two cultivars, whereas CAD activity was enhanced in the core and decreased in the flesh. The results indicated that 1-MCP is effective in controlling the occurrence of CI, but the associated induced fruit core lignification in particular cultivars can be serious.