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

Xuewei Li,Chunmei Zhang,Sheng Qin,Ke Xing,Mingjie Xu,Shurui Cai,Yu Zhang,Beibei Li,Bo Yuan

doi:10.3390/microorganisms8030319

Abstract

Black spot disease, which is caused by the pathogenic fungal Ceratocystis fimbriata, 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 in vitro and in vivo was investigated. Based on morphological identification and phylogenetic analysis of the 16S rRNA gene sequence, strain SPS-33 was identified as Streptomyces lavendulae. Volatile organic compounds (VOCs) emitted by SPS-33 inhibited mycelial growth and sporulation of C. fimbriata in vitro and also induced a series of observable hyphae morphological changes. In an in vivo pathogenicity assay, exposure to SPS-33 significantly decreased the lesion diameter and water loss rate in sweet potato tuberous roots (TRs) inoculated with C. fimbriata. 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 C. fimbriata. These findings suggest that VOCs from S. lavendulae SPS-33 have the potential for pathogen C. fimbriata control in sweet potato postharvest storage by fumigant action.

Highlights

Sweet potato [Ipomoea batatas (L.) Lam.] is one of the 10 most important crops in the world
The results suggested that Volatile organic compounds (VOCs) produced by S. lavendulae SPS-33 inhibited spore production by affecting the normal growth and development of mycelia
The following work is to change the VOC composition and improve the antimicrobial ability of S. lavendulae SPS-33 by optimizing the culture medium and conditions. This is the first study that focuses on the VOCs produced by S. lavendulae

Summary

Introduction

Sweet potato [Ipomoea batatas (L.) Lam.] is one of the 10 most important crops in the world. It has the characteristics of low fat, low caloric, and high dietary fiber content. It is a medicinal plant, which has many important biological activities, such as anti-tumor, antibacterial, and antioxidant factors [1,2]. Sweet potato is widely planted in more than 100 countries in the world, of which the largest cultivated area is the continent of Asia. This is followed by Africa and South America. Sweet potatoes with good taste and a small size sell for a higher price

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