Regulation of nitric oxide treatment in the biosynthesis of aroma volatiles in peach fruit during storage.

Background. Nitric oxide (NO) is an important signaling molecule which could regulate different aspects of fruit ripening and senescence. However, the effects of NO treatment on the aroma volatiles of postharvest peaches is rarely reported. Materials and methods. In the present study, ‘Xiahui 6’ peaches were fumigated with 10 µL·L –1 NO for 3 h, then stored at 20°C for 9 days. Fruit firmness, SSC, TA, ethylene production, the content of fatty acids and aroma volatiles, and related gene expression were evaluated during storage. Results. Nitric oxide significantly maintained higher fruit firmness, SSC and TA at the end of storage, thus maintaining higher fruit quality. The gene expression of PpACS1/3 , PpACO were significantly depressed in NO-treated peaches, which resulted in the reduction of ethylene production. In addition, NO treatment delayed the decline of C6 volatiles, inhibited the formation of esters and lactones supported by a lower expression level of PpLOX3/4 , PpAAT1/2 , PpACX1/2/3/4 , PpFAD1/3 and a higher transcript abundance of PpLOX2 , PpHPL1 , PpADH1 . Additionally, the content of PA, SA, OA, LA and LeA reduced in response to NO treatment during the second half of storage, accompanied by a lower mRNA level in PpFAD1/2/3 . Conclusions. The effects of NO on peach aroma volatiles during storage were novel among the study of NO in peaches. In this study, NO maintained higher fruit quality, delayed the ripening and senescence of peach fruit after harvest. For aroma volatiles, NO maintained higher levels of C6 volatiles and reduced the content of esters and lactones in peaches, as well as the content of PA, SA, OA and LeA. These results together suggest that the effects of NO on peach aroma volatiles are a result of the regulation of genes related with the biosynthesis of aroma compounds, ethylene and fatty acids.