Abstract:

【Objective】 This experiment was aimed to discuss the relationship between cell wall metabolism and fruit softening, and their regulation in harvested ‘Jingbaili’ pear to provide a theoretical basis for improving fruit quality and inhibiting fruit softening.【Method】 Fruits of pear cultivar ‘Jingbaili’ (Pyrus ussuriensis Maxin. cv. Jingbaili) were used to investigate the changes in cell wall compositions, their metabolism-related enzymes, and their regulation by low temperature (0℃) and ethylene (1-MCP or ethephon). 【Result】 The contents of cell wall materials (CWM), covalent pectin (CSP), cellulose and semicellulose decreased, while the content of ionic pectin (ISP) and soluble pectin (WSP) increased during fruit softening. Activities of pectinesterase (PME) and polygalacturonase (PG) enhanced on the 3 rd day after harvest, and their peaks appeared on the 9th and 12 th days, respectively. Activities of β-galactosidase (β-Gal) and α-L-arabinofuranosidase (α-L-Af) increased initially and maintained this trend by the end of storage, while cellulase activity declined during fruit softening. Analysis of correlation showed that semicellulose, ISP and CSP had more relationship with firmness than WSP and cellulose; β-Gal and α-L-Af had more significantly correlation not only with firmness, but also with cell wall compositions than the other enzymes. Treatments with 0℃ and 1-MCP decreased the declines in cellulose, semicellulose and CSP contents, as well as the increases in ISP and WSP contents. Meanwhile, activities of β-Gal, α-L-Af, PME and PG were inhibited significantly, postponing fruit softening, but fruit softening was not facilitated by ethephon. 【Conclusion】 The changes in cell wall compositions had an important relationship to fruit ripening, which were resulted by their metabolism-related enzymes. Among them, β-Gal and α-L-Af could play more roles at early softening stage, PME and PG accelerated late fruit softening, while cellulase showed little effect. Fruit softening was obviously inhibited by 0℃ or 1-MCP, but it was not markedly facilitated by ethephon.

Key words: Pyrus ussuriensis Maxin. cv. Jingbaili, fruit softening, cell wall metabolism, regulation