Risk Assessment And Effect Analysis On Fruit Quality Of Akebia Trifoliata Fruit Disease

As the third generation of new dietary health fruit,Akeba trifoliate is under great threat from potential fungal diseases when wild species are domesticated into cash crops for large-scale cultivation.Therefore,rapid and effective assessment of disease risk is an important and valuable work for the commercial development of wild plant resources.Studies have shown that diseases not only affect the appearance quality of fruits such as size and shape,but also affect the internal quality of fruits..When plants are stressed by diseases,they often evolve a whole set of mechanisms to resist external stresses.In order to avoid huge economic losses,we evaluated the potential disease risk of widely cultivated Akebia trifoliate from the aspects of symptoms,fungal diversity and differentially expressed sequences.The appearance quality and internal quality of Akebia trifoliata fruits with different disease levels were measured to evaluate the impact of the disease on the industry.To investigate the damage of membrane lipid and antioxidant enzymes of Akebia trifoliata in different stages of susceptible and resistant for understanding the mechanism of resistance to disease stress.The results are as follows:1.By field observation,we found some discernible symptoms of four diseases including powdery mildew,anthracnose,fruit shrinkage and brown spot.Secondly,comparison analysis of ITS sequence between resistant and susceptible sample suggested that Cercospora,Colletotrichum and Strelitziana could contain the potential pathogens.Finally,Total 20 putative pathogenic fungi were deduced according to the artificial threshold that the read number was larger than 1200 and the ratio of the read in susceptible pool to that in resistant pool was more than 20 by transcriptome sequencing and they would result five reported diseases and seven putative unknown disease risks on Akebia trifoliate fruits,in which anthracnose,powdery mildew and brown spot would ranked in the top three position.2.Compared with healthy Akebia trifoliate,the appearance quality of infected Akebia trifoliate changed obviously,the fruit weight decreased significantly and became lighter,the pericarp thickness became lighter and thinner,the seed rate increased,the edible rate decreased,and the fruit shape changed in different degrees.By measuring the total amount of soluble solid,titrable acid,vitamin C and amino acid content in different disease degrees,there were significant differences among different disease degrees,and the fruit nutrient content decreased significantly with the deepening of disease degrees.3.In the process of studying the antioxidant activity in the peel of Akebia trifoliate at different stages,it was found that the SOD activity,POD activity and CAT activity of susceptible Akebia trifoliate were generally higher than those of resistant Akebia trifoliate,indicating that susceptible Akebia trifoliate plants produce a large amount of antioxidant enzymes to alleviate the damage.The trend of antioxidant change was different at different growth stages,but all showed an obvious peak in June,which was related to the production more MDA for membrane lipid peroxidation of pericarp during this period.