Mitigating Oxidative Browning in Litchi by Regulating Biochemical Markers and Targeted Gene expression via Exogenous Nitric Oxide.

Abstract

Nitric oxide has been shown to influence oxidative metabolism in plants, enhancing their resilience to various biotic and abiotic stresses. Post-harvest oxidative stress is a key factor leading to quality deterioration in litchi (Litchi chinensis Sonn.) fruit, with visible symptoms that significantly reduce shelf life and consumer acceptability. Therefore, the effect of exogenous sodium nitroprusside (SNP; 1.0 mM and 2.0 mM) on litchi (cv. Purbi) fruit was examined during storage at 7 ± 1°C. Different biochemical changes related to post-harvest quality and pericarp browning of litchi were evaluated. The results suggested that SNP (2.0 mM) was significantly effective in reducing weight loss, the pericarp browning index and decay loss. The fruit subjected to SNP (2.0 mM) treatment retained more total anthocyanins and total phenolic content with reduced peroxidase and polyphenol oxidase enzyme activity. Other quality attributes, such as total soluble solids (TSS), titratable acidity and ascorbic acid, were also recorded to be greater in the SNP (2.0 mM)-treated fruits. These results were consistent with the expression profiles of LcPPO, LcPOD and Laccase genes. The expression levels of these genes were highly suppressed in the nitric oxide-treated fruits compared to those in the control fruits. Therefore, SNP (2.0 mM) treatment could reduce litchi pericarp browning and prolong the post-harvest life of fruit for up to eighteen days during cold storage.