| Longan (Dimocarpus longan Lour.) is a famous subtropical fruit species in the South of China. Since longan fruit mature in the hot season, the fruit deteriorate rapidly after harvest due to percarp browing, aril break down and decay. This paper reports the changes of active oxygen metabolism, pathogenesis-related proteins, defense related enzyme, phenolics metabolism in longan after inoculation with Lasiodiplodia theobromae Pat.,the major pathogen in China. The results were as follows:Disease index of Longan fruit and browning index of pericap increased gradually with the infection of Lasiodiplodia theobromae Pat.. Activities of chitinase andĪ²-1,3-glucanase increased, which were the major defense enzymes, and activity of PAL, POD and PPO enhanced sharply, which were the key enzyme related to the metabolism of lignin, plant protection and phenolics. The activity of antioxidative enzymes SOD, CAT,APX and the content of endogenous antioxidants AsA , GSH reduced, the formation of active oxygen free radical and the activity of LOX activity strengthen greatly, the content of MDA and cell membrane permeability increased rapidly. The activity of POD, PPO related to pericap browning increased, and the content of total phenol and flavonoids decreased significantly.In summary, the reducing mechanism of longan fruit postharvest disease resistance has been proposed. That was: disease resistance of fruit rapidly increased with the infection of Lasiodiplodia theobromae Pat.. However, the capacity of pericap to scavenge active oxygen was reducing, increasing of reactive oxygen species accumulation was intensifying damage of membrane systems, the activity of defense related enzymes was decreasing; PPO, POD in the cell organelle was touching phenolic compounds ,which caused the appearance of phenolic content enzymatic oxidation, the injury of organization structure and the attenuation of functions, the disease resistance of longan fruit lost finally. |
PDF Full Text Request