Research On Antifungal Mechanism Of Ramulus Cinnamomi Main Active Ingredients Against Blue Mould And The Preservation Effects On 'XinYu Tangerine'

New, non-toxic and highly-effective natural fungicide has beening a major focus in the research field both at home and abroad in recent years. This experiment was based on our team's early research results of separation identification of Ramulus cinnamomi main antifungal active ingredients: cinnamaldehyde and cinnamia acid, use a kind of citrus postharvest main pathogens—Penicillium italicum as the selected strains, Chinese herbal medicine Ramulus cinnamomi for the material, further study were studied on their antifungal spectrum, antifungal mechanism, biological control effects on the damaged and inoculated ‘Xinyu tangerine' and fresh-keeping effects of Ramulus cinnamomi extracts and its combined coating, so as to lay certain theoretical foundation for natural antiseptic material instead of chemical fungicide, and provide certain reference value for Chinese herbal medicine and its active substances applied on disease control and fresh-keeping in citrus etc other fruits and vegetables in the future, it also has the vital significance for the development of green and pollution-free disinfection preservative in fruits and vegetables.The main results were as follows:1. Using double dilution method and mycelial growth rate method, determine the indoor virulence of the main antifungal active ingredients: cinnamaldehyde and cinnamia acid of Ramulus cinnamomi to fifteen kinds of plant pathogens such as Penicillium italicum ? Penicillium digitatum and Fusarium oxysporum f. sp.niveum. The result suggested that cinnamaldehyde and cinnamia acid showed different degrees of inhibition,they had a broader antifungal spectrum. In the study, cinnamaldehyde had the best inhibition effect on Phomopsis sp., EC50 value was 0.0179 mg/mL and it had the worst effect on Penicillium digitatum, EC50 value was 0.7551 mg/mL; cinnamia acid had the best effect on Phomopsis mauritiana and Botryosphaeria dothidea, EC50 value was 0.0061mg/m L and it had the worst effect on Penicillium digitatum, EC50 value was 0.9945mg/m L.2. In this research, cinnamaldehyde and cinnamia acid as Ramulus cinnamomi main antifungal active ingredients were utilized to investigate the antifungal activities and mechanism against Penicillium italicum. The spore germination, cell membrane permeability, mycelium morphology, mycelia inclusion contents and key enzymes activities of metabolism were discussed to explain the potential mechanism. The results showed that the minimum inhibitory concentration(MIC) and the minimum fungicidal concentration(MFC) of cinnamaldehyde were 0.025 mg/mL and 0.1 mg/mL, and to cinnamic acid, they were 0.1 mg/mL and 0.4 mg/mL, respectively. Cinnamaldehyde and cinnamic acid had interference effects on spore germination, mycelial growth development,resulted in mycelium presented distortion and expansion and fracture, they also could damage the normal structure and stability of cell membrane effectively, caused cell membrane's diffusion, led to exosmose of mycelial inclusion, decreased succinate dehydrogenase and malate dehydrogenase activities, damaged the tricarboxylic acid cycle process, and then affected the growth and metabolism of mycelium.3. According to the effects of 500 times and 1000 times diluted prochloraz on Penicillium italicum and preservation effects on damaged ‘Xinyu tangerine', elected the suitable concentrations of cinnamaldehyde and cinnamic acid, analysed the effects of protection and defense-related enzymes activities of 25 mg/mL and 8 mg/mL cinnamaldehyde and 30 mg/mL and 15 mg/mL cinnamic acid. The results showed that,compared with the control group, all treatments could decrease the disease incidence and index(p<0.05), enhance the fruit living protection effectively, reduce the consumption of nutrients, inhibit MDA and H2O2 accumulating, improve and hold higher SOD, PAL, PPO and POD activities, induced and enhanced the defense abilities of ‘Xinyu tangerine',strengthen fruit's resistance to the disease. The results suggested that 25 mg/mL cinnamaldehyde and 30 mg/mL cinnamic acid were proved better.4. Effects of 100 mg/mL Ramulus cinnamomi on fresh-keeping of ‘Xinyu tangerine'were investigated during storaged at(5 ± 1)? and RH 85%~90%. The results showed that Ramulus cinnamomi extracts significantly reduced decay rate, weight loss rate and MDA content of fruits in comparison with the control group at middle and later storage periods, and it also could delay the degradation speed of total soluble solids, total sugar,Vitamin C and titratable acidity content, keep higher CAT, SOD, PAL, POD and PPO activities, which suggested that Ramulus cinnamomi extracts effectively maintain the postharvest quality and flavor of fruit and play a good role in the fresh-keeping of ‘Xinyu tangerine'.5. The preservation effects of ‘Xinyu tangerine' during ambient temperature storage were conducted with Ramulus cinnamomi extracts and its combined coating. Compared with the control group, during the storage period, treatments with Ramulus cinnamomi or combined coating could decrease the decay rate and weight loss of fruit effectively,substantially delayed the reduction of total soluble solids, Vitamin C and total sugar content, and reduce the degradation rate of titratable acidity, and those treatments also could obviously restrain the increasement of MDA content, keep higher activities of SOD,CAT and POD at the later storage period, delay the arrival of PAL and PPO top activity and present a significant difference with the control group, and Ramulus cinnamomi extracts combined 1.5% alginate and 700 mg/L citric acid presented the best effect.