Transcriptome profiling of Nephelium lappaceum: Sodium nitroprusside-induced delays of postharvest browning.

Sodium nitroprusside (SNP), as a nitric oxide donor, is widely used in postharvest fruit physiology and metabolism. Our previous study has indicated that SNP plays a crucial role in postharvest browning control of rambutan, but the molecular mechanism underlying this process is still unclear. In this research, we investigated the gene expression and function of postharvest rambutan in response to SNP during browning. We found 7336 differentially expressed genes (DEGs), among which 2206 were upregulated and 5130 were downregulated. Gene Ontology (GO) enrichment as well as Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were performed, and the real-time quantitative PCR (qPCR) data were consistent with transcriptome data. The DEGs relevant to rambutan pericarp browning were mainly involved in anthocyanin biosynthesis, phenolic oxidation, reactive oxygen species (ROS) production, and energy supply. It was shown that SNP regulated the synthesis and degradation of anthocyanins, accumulation of phenols, level of ROS and energy metabolism to suppress the postharvest browning of rambutan. Also, one WRKY transcription factor involved in ROS metabolism was observed to be differentially regulated. These findings add to our insights into the molecular mechanisms of the SNP-induced browning delays of rambutan, which has implications for subsequent studies on molecular mechanisms of fruit browning.

Biological prevention and control of pitaya fruit canker disease using endophytic fungi isolated from papaya.

Pitaya fruit canker is an important disease in pitaya production. Facilitating resistance through the application of biological control principles is a promising alternative to traditional control strategies. This study evaluated the induced resistance of Penicillium rolfsii, numbered Y17 isolated from papaya leaves in pitaya fruit, and evaluated the activity of the defense enzymes, total antioxidant capacity (T-AOC), and malondialdehyde (MDA) content of the treated fruit. The results demonstrate that treatment with Y17 effectively induced resistance of pitaya fruit to canker disease caused by Neoscytalidium dimidiatum, with an inhibition rate of 70.87%. In addition, Y17 notably improved the activities of peroxidase, catalase, and polyphenol oxidase as well as the T-AOC of the treated samples. Y17 treatment reduced the MDA content in these fruits. Taken together, our results suggest that Y17 treatment could trigger pitaya fruit defense responses and effectively induce resistance to fruit canker disease.

Sodium Nitroprusside Functions in Browning Control and Quality Maintaining of Postharvest Rambutan Fruit.

Surface browning after harvest is the primary constraint affecting the storage life and market circulation of rambutans. In this study, rambutan fruits were soaked in sodium nitroprusside at different concentrations and stored at 25°C for 8 days to explore the effects on postharvest quality and browning. The weight loss, browning index and superoxide anion radical, hydrogen peroxide and malondialdehyde contents of the treated fruits were reduced compared to those of the control fruits (soaked in distilled water). And fruits treated with sodium nitroprusside had a higher total phenolic content and lower polyphenol oxidase and peroxidase activity. In addition, compared with the control, the treated fruits exhibited higher phenylalanine ammonia lyase, ascorbate peroxidase and superoxide dismutase activities; titratable acidity; and soluble solid, vitamin C and protein contents, indicating high fruit quality. Overall, sodium nitroprusside treatment at 200 µmol L-1 demonstrated the most positive preservation effects. Therefore, sodium nitroprusside treatment, particularly at 200 µmol L-1, can be used as an eco-friendly, safe and convenient method for postharvest quality management and high-efficiency preservation of rambutan fruits.