| Papaya is one of the medicinal and edible plants.Endophytic fungi isolated from papaya plants may have biologically active components of the same or similar structure as the host plant.Through screening the active strains of the endophytic fungi of the papaya and analyzing the active effect of the strains,it can be of great significance to applicate the endophytic fungi resource of the plant with potential value.In this study,the endophytic fungi in different parts of the papaya were isolated by tissue separation,and the morphology and molecular biology were used to classify and identity the endophytic fungi.The endophytic fungi with good antioxidant activity in papaya were screened by DPPH and ABTS free radical scavenging test.The flavonoids in the antioxidant active components of the strain with good antioxidant activity were identified by chemical chromography5 thin layer chromatography and ultraviolet spectrometry.In the method of plate confrontation,strains with antibacterial activity in endophyticfungi of papaya were screened out.The control effect of the active strain on the anthracnose of the papaya fruit was analyzed by screening the obtained active strain on the material papaya fruit,and the control mechanism of anthracnose was studied.The main research results are as follows:(1)Isolation and identification of endophytic fungi from papaya:131 endophytic fungi were isolated from papaya,including 31 from the stem,45 from the leaf and 55 from the fruit.The results of morphological observation and molecular biological identification showed that they belonged to 20 genera,such as Aspergillus,Collelotrichum,Candida,Cladosporium,Penicillium,Fusarium,Phoma,Phyllosticla,Trichoderma,Talaromyces,Diaporthe,Phialemonium.Aspergillus and Colletotrichum were the dominant groups of endophytic fungi of papaya,with relative separation frequency of 47.33%and 14.50%.respectively,the rest of the isolates were less than 10%.(2)Screening of antioxidant activity strains of endophytic fungi of papaya:The ethyl acetate extract of 100μg/mL endophytic fungi was used as the initial screening concentration.DPPH and ABTS radical scavenging were used to screen the antioxidant activity strains,and 7 strains with high antioxidant activity were screened out,and free radical scavenging rate is more than 50%.The strain Y17(Penicillium rolfsii)shows a better antioxidant activity,which is less than 20μg/mL for both free radicals.Furthermore,five kinds of color reaction of flavonoids were used.TLC and UV were used to identify the flavonoids in ethyl acetate extracts of endophytic fungi of papaya.It was found that strain G41(Penicillium citrinum)was positive for all five kinds of color reaction flavonoids.TLC method showed that it contained the same or similar flavonoids as quercetin.UV detection spectrum showed that it accorded with the UV spectrum characteristics of flavonoids.It indicated that endophytic fungi of papaya contained flavonoid-producing endophytic fungi.(3)Screening of antibacterial activity strains from endophytic Fungi of Papaya:Five common plant pathogenic fungi were used as indicator bacteria to screen antibacterial activity strains by plate confrontation method,then 13 strains showed antibacterial activity against at least one tested pathogenic fungus.The strain Y17 showed bacteriostatic effect on the pathogen of papaya anthracnose(Colletotrichum gloeosp),and showed broad-spectrum bacteriostatic activity.The experimental results showed that the area of anthracnose spot was significantly reduced after treated with strain Y17 fermentation liquid,and the area of anthracnose spot was effectively inhibited.Besides,the results showed that the enzyme activities of CAT.POD and SOD in fruits treated with strain Y17 were improved to some extent compared with those in the control group.The content of malondialdehyde(MDA)in the soaked fruit of strain Y17 was significantly lower than that of the treated group inoculated only with anthrax.This indicated that the treatment with strain Y17 fermentation broth could increase the activity of antioxidant defense enzymes such as CAT,POD and SOD in papaya fruits,delay the accumulation of MDA in papaya fruits,and thus improve the resistance of papaya fruits to anthrax infection. |
