| Kiwifruit,a genus of kiwifruit(Actinidia)berries of the family Actinidiaceae,is popular among consumers for being juicy,rich in vitamin C and strong in antioxidant ability.After harvest,it is highly susceptible to pathogenic fungi such as Botryosphaeria dothidea,Botrytis cinerea,and Phomopsis macrospore,which may cause the fruits to rot during storage,resulting in significant economic losses.The inhibitory effects of citral against Botryosphaeria dothidea,Phomopsis macrospore,and Botrytis cinerea and its antifungal mechanism against B.dothidea were studied.Meanwhile,the effects of citral treatment on disease resistance to soft rot and kiwifruit postharvest preservation under cold storage were investigated.The main research contents are as follows:1.The inhibitory effects of twelve essential oils on kiwifruit postharvest pathogens were studied.Citral,ionone,geraniol and methyl ionone showed strong inhibitory ability against B.dothidea through direct contact.Citral and tetrahydrolinalool showed strong inhibitory ability against B.dothidea through fumigation.Citral and geraniol had strong antifungal ability against P.macrospore by means of direct contact.Linalool,ionone and citral exhibited strong antifungal ability against P.macrospore with fumigation way.Citral and geraniol had good direct contact inhibition ability against B.cinerea.Linalool and tetrahydrolinalool had better fumigation inhibition ability against B.cinerea.Moreover,the direct contact inhibition ratio of citral against B.dothidea,P.macrospore,and B.cinerea(83.27%,100%,and 100%)were significantly higher than the other essential oils.The fumigation inhibition ratio of citral against B.dothidea(81.63%)were significantly higher than the other essential oils.Citral showed strong antifungal activity against B.dothidea and P.macrospore by direct contact and fumigation way.Citral had strong antifungal activity against B.cinerea by direct contact way.2.The results showed that citral had strong inhibitory activity against postharvest pathogens of kiwifruit,and the antifungal ability increased as concentration grew.The value for MIC of citral was 0.4 μL/m L against B.dothidea.Citral changed the morphology of the hypha of B.dothidea,which became rough,shriveled and even collapsed.The mycelial dry weight was reduced by citral treatment.The decrease in the lipid and ergosterol content in mycelia resulted in the damage to cell membrane permeability and cell wall integrity.The activities of respiratory related enzymes,such as MDH and SDH,were inhibited by citral.These results suggested that the lipophilicity of citral may affect the membrane fluidity and destruct the respiration of B.dothidea leading to the damage in the cell membrane,the leakage of cell contents,and the disorders of cell metabolic function.Hence,citral had strong antifungal ability to inhibit the mycelial growth of B.dothidea.3.The induction effect of citral(0.8 μL/m L)on the resistance to soft rot of kiwifruit was higher than that of other treatment group.The induction effect of citral(62.5 μL/L)was higher than that of other treatments.The diameter of lesions and the decay in postharvest kiwifruit inoculated with B.dothidea were reduced in citral treatment group,and the induction effect was increased by citral.The results showed that citral could effectively induce resistance to soft rot in kiwifruit by increasing the activities of antioxidant enzymes,defense related enzymes including APX,CAT,SOD,PAL,CHI and GLU,and enhancing related gene expression.4.Citral treatment significantly inhibited the increase of respiration intensity and weight loss rate of kiwifruit.Compared with the control group,the fruit treated with citral had higher hardness and ascorbic acid content,lower maturity index,and higher antioxidant ability.Citral treatment could significantly delay the maturation and senescence process of postharvest kiwifruit.The values for weight loss,ripening index of kiwifruit from citral fumigation treatment were less than that of direct contact treatment,and ascorbic acid content for citral fumigation group was higher than that of direct contact treatment.These findings suggested that citral fumigation treatment had better preservation effect than direct contact in postharvest kiwifruit. |
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