| Wolfberry(Lycium barbarum L.),a traditional Chinese medicine,has been cultivated in our country for more than 2,000 years.The fresh wolfberry fruit is rich in nutrients,which is considered as “super fruit”.Fresh wolfberry fruits are prone to rot caused by pathogenic fungi during transportation,processing and storage after picking.Therefore,dried wolfberry fruits are mainly supplied in the market while fresh wolfberry fruits are rare.The use of antagonistic bacteria to prevent and control the contamination of pathogenic fungi has become a hot research spot in recent years.The volatile organic compounds(VOCs)produced by Bacillus has good antifungal effect,with low molecular weight and easy to spread,so avoid surface residues,which has application value in post-harvest storage and preservation of fruits and vegetables.In this study,the pathogenic fungi caused the postharvest rot of wolfberry fruits are isolated and identified.Using the isolated pathogenic fungi as indicator pathogenic fungi,a strain of Bacillus subtilis CL2,which produces antifungal VOCs,is selected from the tubers of Paris polyphylla,the VOCs produced by strain CL2 is analyzed and identified with gas chromatography‐ion mobility spectrometry analysis(GC-IMS).Finally,the effect of the prevention and control of the pathogenic fungus LB1 in vivo with VOCs produced by strain CL2 is explored.The main results of the study are as follows:1.Four pathogenic fungi were isolated and identified from the decayed wolfberry fruits postharvest.The morphological and molecular identification results showed that4 pathogenic fungi were Mucor circinelloides LB1,Fusarium arcuatisporum LB5,Alternaria iridiaustralis LB7 and Colletotrichum fioriniae LB8,respectively.2.Using 4 postharvest pathogenic fungi of wolfberry as indicator fungi,an endophytic strain CL2 that produces antifungal VOCs was selected from the tubers of Paris polyphylla by the two‐sealed‐base‐plates method.Through morphological,physiological and biochemical identification and 16 S r DNA identification,the strain CL2 were finally identified as Bacillus subtilis.3.By studying the effect of VOCs produced by strain CL2 on the growth and morphological structure of 4 wolfberry pathogenic fungi,the antifungal effect and mechanism of VOCs were preliminarily explored.The results showed that when cocultured with strain CL2,the VOCs produced by strain CL2 had a significant inhibitory effect on the growth of the 4 pathogenic fungi,and the inhibition rate for the growth of strain LB8 is 73%.Scanning electron microscope results showed that VOCs can cause abnormal hyphae morphology of 4 wolfberry postharvest pathogenic fungi,such as hyphae loss of linearity,surface depression,hyphae twisted and contracted,the ending of hyphae is enlarged,hyphae ruptured and folded.4.On the basis of the GC-IMS analysis,7 VOCs components produced by strain CL2 were identified.They were 2,3‐butanedione,butyl acetate,2‐heptanone,acetoin,2‐pentanone,3‐methylbutyric acid and butanol,respectively.The result of two‐sealed‐base‐plates method indicated that the main antifungal VOCs components produced by the strain CL2 were 2,3-butanedione and 3‐methylbutyric acid.5.The fresh wolfberry fruits inoculated with the pathogenic fungus LB1 were respectively co-cultured with the strains CL2,2,3-butanedione and 3‐methylbutyric acid to study their effect on the pathogenic fungus LB1 in vivo.Physiological indicators such as decay rate,hardness,total phenols,flavonoids and other physiological indicators of wolfberry fruits cultivated for 0 d,3 d,5 d,and 7 d were tested.The results show that the VOCs produced by strain CL2 and its components 2,3-butanedione and3‐methylbutyric acid can significantly reduce the decay rate of wolfberry fruits,which indicated that these VOCs components can inhibit the pathogenic activity of the pathogenic fungus LB1 in vivo,and they have the potential research value of being further developed as a preservative fumigant for postharvest wolfberry fruits. |
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