Identification of Rhizospheric Actinomycete SPS-33 and the Inhibitory Effect of its Volatile Organic Compounds against in Postharvest Sweet Potato ( (L.) Lam.).

Black spot disease, which is caused by the pathogenic fungal , seriously affects the production of sweet potato and its quality during postharvest storage. In this study, the preliminary identification of the rhizosphere actinomycete strain SPS-33, and its antifungal activity of volatiles and was investigated. Based on morphological identification and phylogenetic analysis of the 16S rRNA gene sequence, strain SPS-33 was identified as Volatile organic compounds (VOCs) emitted by SPS-33 inhibited mycelial growth and sporulation of and also induced a series of observable hyphae morphological changes. In an pathogenicity assay, exposure to SPS-33 significantly decreased the lesion diameter and water loss rate in sweet potato tuberous roots (TRs) inoculated with . It increased the antioxidant enzymes' activities of peroxidase, catalase, and superoxide dismutase as well as decreased malondialdehyde and increased total soluble sugar. In the VOC profile of SPS-33 detected by a headspace solid-phase micro extraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS), heptadecane, tetradecane, and 3-methyl-1-butanol were the most abundant compounds. 2-Methyl-1-butanol, 3-methyl-1-butanol, pyridine, and phenylethyl alcohol showed strong antifungal effects against . These findings suggest that VOCs from SPS-33 have the potential for pathogen control in sweet potato postharvest storage by fumigant action.