| Summary: | Biological control by antagonistic microorganisms are an effective and environmentally friendly approach in postharvest disease management. In order to develop a biocontrol agent for fresh walnut fruit preservation, the potential biocontrol effects of <i>Bacillus amyloliquefaciens</i> RD.006 and <i>Hanseniaspora uvarum</i> FA.006 against the main fungal pathogen of walnuts were evaluated. <i>Botryosphaeria</i> species showed the highest detection, and the JNHT01 strain showed the strongest pathogenicity. <i>Bot. dothidea</i> JNHT01 caused gray mold and brown rot on fresh walnuts, and its incidence rate reached 100% after an 8 days incubation. The growth of this fungal strain can be promoted by lighting, with a maximum growth rate achieved at a pH of 7 and at 28 °C. <i>B. amyloliquefaciens</i> RD.006 and <i>H. uvarum</i> FA.006 supernatants at a concentration of 1–15% <i>v</i>/<i>v</i> showed antifungal activity. The mycelial growth inhibition rates of <i>Bot. dothidea</i> JNHT01 were 23.67–82.61% for <i>B. amyloliquefaciens</i> RD.006 and 1.45–21.74% for <i>H. uvarum</i> FA.006. During <i>Bot. dothidea</i> JNHT01 growth, the biomass, nucleic acid leakage, and malondialdehyde content gradually increased, while the DPPH scavenging capacity and SOD activity decreased. The <i>B. amyloliquefaciens</i> RD.006 and <i>H. uvarum</i> FA.006 strains showed antifungal activity by damaging fungal cell membranes and reducing fungal antioxidant activity. Moreover, the antifungal effect of <i>B. amyloliquefaciens</i> RD.006 was higher than that of <i>H. uvarum</i> FA.006. Hence, the RD.006 strain of <i>B. amyloliquefaciens</i> can be considered a potential biocontrol agent for the management of postharvest walnut diseases caused by <i>Bot. dothidea</i>.
|
|---|