Effects of glycine betaine on the postharvest quality and cell wall metabolism of Malus domestica fruit

Quality decline resulting from senescence and fungal invasion is a crucial factor that impacts the economic value of fruit. The present study aimed to reveal the impacts of 10 mmol L−1 glycine betaine immersion for 10 min on cell wall degradation in 'Qiujin' apples during storage at ambient condition for 15 d. The results showed that glycine betaine exhibited higher levels of soluble solids content, flesh firmness, and water-insoluble pectin, while also delaying the increase in mass loss, total colouration difference, and water-soluble pectin content. Furthermore, glycine betaine effectively restrained the enzymatic activities and gene expressions of pectate lyase, pectin methylesterase, polygalacturonase, cellulase, β-galactosidase, and β-glucosidase, thereby inhibiting the reduction in water-insoluble pectin content and the formation of water-soluble pectin. These findings suggest that glycine betaine can preserve the postharvest quality of 'Qiujin' apples by suppressing the activity and gene expression of key enzymes involved in cell wall metabolism, as well as reducing respiratory rate and ethylene release. In conclusion, the utilisation of glycine betaine treatment may present an effective technique for alleviating softening in postharvest apples and can serve as a promising natural alternative to synthetic chemicals.