Mechanism Of Phenolics On Resisting Fusarium Wilt Of Banana

Plant polyphenols is an important secondary metabolites. They participate in stress tolerance response in plant, especially play an important role in resistance to biotic stress and abiotic stress. In this study, five banana varieties (two groups of sense, anti-mutation varieties and a high resistance variety) were selected as material. Banana were infected by Fusarium Race4species, and then we analysised the dynamic changes of phenolics in banana cell. Activity changes of related enzymes were studied to discuss the mechanism of phenolics against banana Fusarium Wilt, and it would provide a reference for the prevention and control of banana Fusarium wilt and disease-resistant breeding. The main results were as follows:1. The optimum conditions for HPLC which separated10kinds of phenolics of banana was obtained. The optimal condition as follows: the mobile phase A: v (formic acid): v(water)=0.5:99.5; the mobile phase B:100%methanol; column Venusil XBP-C18(250mm×4.6mm,5μm); Detector: the UV detector; The detection wavelength:280nm; column temperature:35℃; flow speed:1.0ml/min; volume of sample:10μl. Gradient elution program:0～10min,4%B～20%B;10～15min,20%B～42%B;15～22min,42%B～50%B;22～34min,50%B～62%B;34～36min,62%B～85%B;36～46min,4%B.2. There were closely relationship between total phenolic, total phenolic acid and banana resistance. After the banana were infectded by Fusarium Wilt, the content of total phenolics in high resistant variety’Gold finger’was obvious higher than other varieties. The peak value of total phenolics content in resistant variety ’Nongkeyihao’ was higher than in ’Brazil’. There were differences for content of phenolic acid between resistant cultivar and susceptible cultivar. There was a significant increase for the content of total phenplic acid in ’Gold finger’.3. There were low content of the free phenolics in cytoplasm, and chlorogenic acid was the highest content. We detected5species of ester-bounded phenolics: hydroxybenzoic acid, chlorogenic acid,vanillic acid,4-coumaric acid,ferulic acid. also, the content of vanillic acid was the highest in the ester-bound phenolics. For cell wall bound phenolics, the main varieties were Catechol, p-hydroxy benzoic acid, vanillic acid,4-coumaric acid, ferulic acid, salicylic acid and ellagic acid. The content of ferulic acid was relatively higher than others. 4. The chlorogenic acid in cytoplasm and4-coumaric acid、hydroxybenzoate in cell wall play an important role in resisting Fusarium wit of banana. The content of chlorogenic acid in resistant variety’Gold finger’was highest in the free phenols of cytoplasm. For ester bound phenolic in cytoplasm, the peak values of chlorogenic acid, p-hydroxybenzoic acid in’nongkeyihao’ and ’Gold finger’ were more than those in susceptible varieties. In the cell wall bound phenolics, the content of P-hydroxybenzoic acid in ’nongkeyihao’ and ’8818-1’ were respectively higher than ’Brazil’ and ’8818’.5. In resistant varieties of bananas, the activities of defense-enzymes (PAL, POD) were higher than those in the susceptible varieties, and there were larger amplitude variation in the activities of defense-enzymes after banana infected by Fusarium wit. The activity of PAL increased higher in resistant varieties than the susceptible varieties. After infected by Fusarium wit, the activity of POD in resistant varieties increased, and the enzyme activity of the high resistant variety ’Gold finger’ was highest. After inoculation with the pathogen, The PPO activity of all cultivars showed an increase, however, no obvious difference was found between resistant and susceptible varieties. The resistant varieties showed larger decrease of the soluble proteins during the descent stage, and had higher increase during the rising stage than the susceptible varieties, Also, the contents of soluble protein in resistant varieties were higher than those in the susceptible varieties during the later period of infection.