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Article

Streptomyces hanimojiang sp. nov. AMJ-169, a Novel Biocontrol Agent Producing Volatile (1S)-(-)-α-Pinene, Suppresses Strawberry Postharvest Rot Caused by Neopestalotiopsis rosae

by
Huaying Zhang
1,2,3,†,
Miaoyi Zhang
2,3,†,
Xiaojuan Li
2,3,
Tao Jing
2,3,
Yankun Zhao
2,3,
Yufeng Chen
2,3,
Junting Feng
2,3,
Zai Zheng
2,3,
Wei Wang
2,3,
Dengfeng Qi
2,3,
Kai Li
2,3,
Jianghui Xie
2,
Daipeng Chen
1,* and
Dengbo Zhou
2,3,*
1
School of Tropical Agriculture and Forestry, Hainan University, Haikou 570228, China
2
State Key Laboratory of Tropical Crop Breeding, Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agricultural Sciences, Haikou 571101, China
3
Sanya Research Academy, Chinese Academy of Tropical Agriculture Science, Sanya 572019, China
*
Authors to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Horticulturae 2026, 12(5), 577; https://doi.org/10.3390/horticulturae12050577 (registering DOI)
Submission received: 24 March 2026 / Revised: 25 April 2026 / Accepted: 30 April 2026 / Published: 8 May 2026
(This article belongs to the Special Issue Research Progress on Growth and Development Biology of Berry)
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Abstract

Postharvest rot caused by Neopestalotiopsis rosae severely threatens strawberry production globally. Here, a novel species of Streptomyces was isolated and identified through polyphasic taxonomy, for which we propose the name Streptomyces hanimojiang sp. nov. AMJ-169. Its volatile organic compounds (VOCs) inhibited N. rosae hyphal growth by 70 ± 3.81%, with (1S)-(-)-α-pinene identified as the key antifungal component (EC50 = 0.018 mL·L−1). Fumigation with 6× EC50 α-pinene reduced fruit rot by 97.52% in a concentration-dependent manner. SEM observations showed that α-pinene caused severe hyphal damage and suppressed pathogen colonization on fruit surfaces. Transcriptomic analysis further indicated that α-pinene treatment was associated with redox regulation, glutathione metabolism, phenylpropanoid metabolism, and carbon-metabolism-related responses in strawberry fruit. These findings suggest that α-pinene controls postharvest anthracnose through direct antifungal activity on fungal hyphae together with host-associated physiological regulation, highlighting its potential as a sustainable postharvest biocontrol candidate.

1. Introduction

Strawberries (Fragaria × ananassa Duch.) are a globally popular fruit, valued for their distinctive flavor, fragrance, and nutritional content [1]. However, its soft texture and high moisture content make it highly susceptible to postharvest fungal decay, particularly in tropical and subtropical regions where warm and humid conditions accelerate disease development [2]. The pathogen Neopestalotiopsis rosae (Maharachchikumbura, K.D. Hyde & Crous, 2014) [3] has recently emerged as a destructive and widespread fungal pathogen responsible for postharvest strawberry fruit rot. This pathogen mainly infects hosts via wounds and natural openings, secretes cell wall-degrading enzymes to destroy plant tissues, and favors high humidity and moderate temperature for conidial germination and disease outbreak, posing a serious threat to strawberry production and leading to substantial economic losses worldwide [4]. The reliance on conventional fungicide-based control for managing postharvest fungal decay in fresh-consumed soft fruits like strawberries presents significant challenges due to concerns regarding residues, the development of fungicide resistance, and overarching sustainability requirements [5]. These limitations necessitate the exploration and implementation of alternative, integrated management strategies to ensure fruit quality and safety, with biocontrol approaches gaining increasing attention for their eco-friendly characteristics.
Volatile organic compounds (VOCs) produced by microorganisms represent a significant and expanding area of research for their potent antifungal properties, particularly in the context of postharvest pathogen control and sustainable agriculture [6]. These natural compounds offer an environmentally friendly alternative to synthetic fungicides, which are increasingly scrutinized for their environmental impact, potential health risks, and contribution to fungicide resistance [7]. Microbial VOCs are characterized by their ability to readily diffuse in the headspace, act effectively without direct contact with the host plant or fruit, and are inherently compatible with residue-minimizing strategies, aligning with contemporary demands for sustainable agricultural practices and consumer safety [8]. Numerous studies have demonstrated the efficacy of VOCs from various microbial sources against a wide range of postharvest pathogens. For instance, specific yeast and bacterial strains have been shown to produce VOCs that inhibit the growth of significant fungal pathogens responsible for fruit spoilage [9].
Streptomyces species belonging to actinomycetes are renowned for their ability to produce a wide array of secondary metabolites, many of which possess significant antimicrobial, antifungal, and anticancer properties. The genus Streptomyces is a crucial source for the discovery of novel bioactive natural products, including a diverse range of volatile organic compounds (VOCs) [10]. These microorganisms are widely distributed in various environments, such as soil, marine sediments, and atmospheric precipitation, indicating a vast, yet largely unexplored, biosynthetic potential [11,12]. Notably, strains isolated from unique ecological niches (e.g., subtropical forest soils) often exhibit distinct metabolic profiles, making them promising candidates for discovering novel bioactive VOCs [13,14]. The VOCs produced by Streptomyces are of particular interest due to their gaseous nature, allowing them to diffuse through environments and exert effects without direct contact [15]. This characteristic is highly advantageous for applications such as fumigants in food preservation and biocontrol agents in agriculture [16,17]. For example, the rhizospheric actinomycete Streptomyces lavendulae SPS-33 has been shown to produce VOCs that effectively inhibit Ceratocystis fimbriata, the causal agent of black spot disease in postharvest sweet potato [14]. This demonstrates the potential for Streptomyces-derived VOCs to contribute to sustainable disease management strategies.
The mechanisms of action of Streptomyces VOCs are diverse and may include direct inhibition of microbial growth, disruption of membrane integrity, interference with metabolic processes, and structural damage to fungal hyphae. Some VOCs may also modulate host defense-associated responses, further enhancing their protective effects against pathogens [18]. This dual mode of action—direct antifungal activity and modulation of host defense responses—makes Streptomyces-derived VOCs particularly effective for postharvest disease control, as they can simultaneously target the pathogen and strengthen the host’s resistance. This multifaceted mode of action often provides a broader spectrum of activity compared to single-target synthetic fungicides, making them less prone to developing resistance in pathogens. The vast, largely untapped genetic resources within Streptomyces species, particularly those from underexplored environments, hold significant promise for future discoveries in this field [11,12].
In this study, we hypothesized that selected Streptomyces strains from subtropical soil can produce abundant antifungal volatile organic compounds as key active components. These function by disrupting fungal cell structure and redox homeostasis, while also regulating strawberry fruit defense metabolism, thereby comprehensively suppressing N. rosae infection and alleviating postharvest rot.

2. Materials and Methods

2.1. Isolation and Screening of Antagonistic Actinomycetes Strains

Soil samples were collected on 2 August 2025 from a subtropical forest in Mojiang Hani Autonomous County, Pu’er City, Yunnan Province, China. A random sampling strategy was adopted, and three spatially independent replicate sites were sampled at a depth of 10–30 cm. The collected soil samples were thoroughly mixed before actinomycete isolation. One gram of mixed fresh soil was added to 9 mL of sterile water and shaken at 180 rpm and 28 °C for 1 h. Actinomycetes were isolated following the standard method of Williams et al. (1983) [19]. The resulting suspension was serially diluted to 10−1, 10−2, and 10−3. Each dilution was plated in triplicate on starch-casein agar (SCA) supplemented with 50 mg/L rifampicin and 50 mg/L nystatin (rifampicin: Sigma-Aldrich, St. Louis, MO, USA; nystatin: Sigma-Aldrich, St. Louis, MO, USA). These concentrations were selected based on commonly used doses in related actinobacterial isolation studies and validated in our preliminary experiments, which could effectively inhibit miscellaneous bacteria and fugal contaminants without affecting the growth of Streptomyces strains. Plates were incubated at 28 °C for 1–2 weeks. Morphologically distinct colonies were purified and preserved at −80 °C in 30% glycerol.
Neopestalotiopsis rosae was isolated from strawberries and preserved in the Laboratory of Tropical Biotechnology, Chinese Academy of Tropical Agricultural Sciences (Haikou, China). The antagonistic activity was preliminarily screened using the four-spot inoculation method [20]. A mycelial plug of N. rosae was placed at the center of a PDA plate, with actinomycete isolates inoculated at four symmetrical points 2.5 cm away. Plates containing only the fungal plug served as control. After incubation at 28 °C for 7 days, the radial growth was measured. The percentage of inhibition (IP%) was calculated as follows: IP% = 100 × [(C − T)/C], where C and T are the average colony diameters in the control and treatment groups, respectively. Each assay was performed in triplicate.
A secondary screening was performed on candidate actinomycetes from the initial round using a double-plate assay to evaluate VOC-mediated antagonistic activity. Each actinomycete isolate was streaked across the entire surface of a yeast extract (YE) agar plate to form a lawn and incubated at 28 °C for 2 days. The plate was then paired face-to-face with a potato dextrose agar (PDA) plate centrally inoculated with a 5 mm mycelial plug of N. rosae, and the two plates were sealed to form a closed volatile-exposure system and co-incubated at 28 °C for 7 days. For the control, a pathogen-inoculated PDA plate was paired with an actinomycete-free YE plate. The inhibition percentage (IP%) was calculated based on fungal radial growth. Finally, strain AMJ-169 was selected for further study because it showed the strongest antifungal activity in both direct antagonism and VOC-mediated inhibition assays.

2.2. Identification of Novel Antagonistic Actinomycetes Species of Strain AMJ-169

The morphology of strain AMJ-169 was examined by scanning electron microscopy SEM; (Zeiss Sigma VP, Carl Zeiss AG, Oberkochen, Germany). Cultural characteristics were assessed on eight media following the International Streptomyces Project (ISP) methods. The colors of aerial mycelia and any diffusible pigments were documented using the ISCC-NBS color charts. Utilization patterns of carbon and nitrogen sources were determined according to Zhou et al. (2021) [21]. The physiological and biochemical characteristics of strain AMJ-169 were comprehensively profiled, including tolerance to different pH levels and NaCl concentrations, starch hydrolysis, siderophore production, nitrate reduction, H2S production, and Tween 20, Tween 40, and Tween 80 degradation, as well as antibiotic susceptibility against 10 standard antibiotics using the disk diffusion method [20]. For chemotaxonomic analysis, the composition of menaquinones and cell-wall amino acids was determined by HPLC (Agilent 1260 Infinity, Agilent Technologies, Santa Clara, CA, USA) [22], polar lipids were profiled by thin-layer chromatography (TLC; Merck KGaA, Darmstadt, Germany), and cellular fatty acids were analyzed by gas chromatography (Agilent 6890, Agilent Technologies, Santa Clara, CA, USA) using the standard MIDI system (Sherlock Version 6.1, MIDI, Inc., Newark, DE, USA).
For phylogenetic analysis, PCR amplification of the 16S rRNA gene was performed with primers 27F and 1492R [23]. Sequence alignment was conducted using the EzBioCloud database (https://www.ezbiocloud.net/identify, accessed on 6 June 2025)) [24], and a neighbor-joining tree was constructed with MEGA 7.0 software (https://www.megasoftware.net/, accessed on 23 June 2025). Genomic DNA was extracted using the Wizard® Genomic DNA Purification Kit (Promega Corporation, Madison, WI, USA) and sequenced on an Illumina Hiseq X Ten platform (Illumina, Inc., San Diego, CA, USA) with PE150 mode. Raw reads were assembled using SPAdes v4.0.0 (https://cab.spbu.ru/software/spades/, accessed on 2 July 2025) with k-mer parameters optimized by kmergenie (v1.7051, http://kmergenie.bx.psu.edu/, accessed on 8 July 2025) and further improved using GapCloser v1.12 (https://github.com/Chuibingyu/GapCloser, accessed on 13 July 2025). A whole-genome-based phylogenetic tree was reconstructed using the Type (Strain) Genome Server (TyGS, https://tygs.dsmz.de/, accessed on 15 July 2025)) with default parameters [25]. Gene prediction was performed with Glimmer v3.02 (https://ccb.jhu.edu/software/glimmer/, accessed on 23 July 2025) [20]. Biosynthetic gene clusters were predicted using antiSMASH v7.0.0 (https://antismash.secondarymetabolites.org/, accessed on 16 September 2025) with default parameters. For genomic taxonomy, Average Nucleotide Identity (ANI) and digital DNA–DNA hybridization (dDDH) values were calculated using the OrthoANI online tool (https://orthoani.ezbiocloud.net/, accessed on 18 September 2025) and GGDC (v2.1) (https://ggdc.dsmz.de/, accessed on 18 September 2025), respectively.

2.3. Identification of VOC Components in Strain AMJ-169

To analyze the volatile chemical profile, 100 µL of a strain AMJ-169 suspension (106 CFU mL−1) was inoculated into a sterile 50 mL flask containing 15 mL of YE solid medium. The flask was sealed with sterile foil and sealing film. A control flask was prepared with distilled water in place of the bacterial suspension. After incubation at 28 °C for 7 days, VOCs were collected by solid-phase microextraction (SPME) using a 50/30 µm DVB/CAR/PDMS fiber (Supelco, Bellefonte, PA, USA). The fiber was exposed to the headspace at 45 °C for 30 min and desorbed at 250 °C for GC–MS analysis. VOCs were analyzed using an Agilent 7890A gas chromatograph coupled to a 5975C Inert XL MSD equipped with an HP-5MS UI column (Agilent Technologies, Inc., Santa Clara, CA, USA). Helium was used as the carrier gas at 1 mL/min with a split ratio of 10:1. The oven program was 50 °C for 5 min, then 5 °C/min to 150 °C for 1 min, followed by 20 °C/min to 300 °C for 3 min. Mass spectra were acquired in full-scan mode over m/z 45–450 [26]. Compounds were annotated by comparison with the NIST14 library, and their relative contents were estimated based on peak areas.

2.4. Antifungal Activity Evaluation of Identified VOCs

The antifungal activity of selected VOCs was assessed by a dual-plate assay. Standard compounds included propanoic acid, 2-methyl-, ethyl ester (PubChem CID: 7342); (1S)-2,6,6-trimethylbicyclo [3.1.1]hept-2-ene (PubChem CID: 440968); bicyclo [3.1.1]heptane, 6,6-dimethyl-2-methylene-, (1S)- (PubChem CID: 440967); and acetic acid, 2-ethylhexyl ester (PubChem CID: 7635). All compounds were obtained from Shanghai Macklin Biochemical Co., Ltd. For preliminary activity assessment, a 5 mm mycelial plug of N. rosae was placed at the center of a PDA plate. Sterile filter paper discs (13 mm diameter) were impregnated with 10 µL aliquots of the pure compounds, achieving a theoretical headspace concentration of 0.017 mL/L, and placed in Petri dish lids. Plates were sealed and incubated at 28 °C for 7 days. Control treatments received an equal volume of sterile water. The inhibition percentage (IP%) was calculated according to Section 2.1. To determine the EC50 of the most effective volatile compound, the same dual-plate setup was used with a dilution series ranging from 0.0015625 to 0.05 mL/L. EC50 was calculated in SPSS version 22 using a LOGIT model with log10-transformed concentrations [27].

2.5. Effect of (1S)-(-)-α-Pinene on Controlling Strawberry Postharvest Rot

Based on its superior antifungal activity in the initial in vitro screen, (1S)-(-)-α-pinene ((1S)-2,6,6-trimethylbicyclo [3.1.1]hept-2-ene) was selected for further investigation. Strawberry fruits (Fragaria × ananassa Duch. cv. ‘Benihoppe’) at 80–90% red coloration, moderate firmness, and uniform size were selected, surface-disinfected with 75% alcohol for 30–60 s, rinsed 3–5 times with sterile water, and air-dried on sterile filter paper. Standardized artificial wounds were made in the equatorial region using a sterile needle, with dimensions of 2 mm depth and 3 mm width. Each wound received 20 µL of sterile water followed by a 5 mm mycelial plug of N. rosae. Five fruits were placed in one 2 L plastic box, and the box was treated as the biological replicate. Aliquots of (1S)-(-)-α-pinene corresponding to 1×, 2×, 4×, and 6× EC50 were applied to separate sterile polystyrene dishes (3.5 cm diameter) placed inside the boxes. Boxes were sealed with three layers of Parafilm and incubated at 28 °C. Evaluations were conducted at 0, 5, 7, and 9 days post-inoculation, with three independent boxes per treatment. Disease development was evaluated according to Oztekin and Karbancioglu (2021) [28].
The oxidative status of strawberry fruit was evaluated by determining malondialdehyde (MDA) content and the activities of antioxidant enzymes, including superoxide dismutase (SOD) and ascorbate peroxidase (APX). All assays were performed using commercial kits from Solarbio Science & Technology Co., Ltd. (Beijing, China). Fresh strawberry fruit tissues were collected, immediately frozen in liquid nitrogen, and stored at −80 °C until use. Frozen samples were ground to a fine powder under liquid nitrogen and homogenized in the extraction buffers supplied with the kits. Homogenates were centrifuged at 4 °C, and the supernatants were collected for analysis. All assays were performed with at least three biological replicates, and each biological replicate was analyzed in technical triplicate.

2.6. Antifungal Mechanism of (1S)-(-)-α-Pinene on Strawberry Postharvest Rot

The effects of (1S)-(-)-α-pinene on fungal hyphae of N. rosae were assessed as described in Section 2.4. After 5 days of incubation, peripheral mycelia from the colony edge were sampled. Samples were fixed in 2.5% glutaraldehyde in PBS (pH 7.2) at 4 °C overnight, washed twice with PBS, dehydrated through a graded ethanol series, immersed in tert-butanol for solvent substitution, freeze-dried (EYELA FUD-2110, Tokyo Rikakikai Co., Ltd., Tokyo, Japan), sputter-coated (Cressington 108 Auto, Cressington Scientific Instruments, Watford, UK), and observed by SEM at an acceleration voltage of 20 kV [29]. The morphology of strawberry fruit at the wound sites was observed using SEM following the treatment methods described above. For transcriptome analysis, strawberry fruits treated with 6× EC50 α-pinene and untreated control fruits were sampled after 5 days of co-incubation. Three biological replicates were analyzed per group. RNA-seq libraries were prepared using the Illumina Stranded mRNA Prep, Ligation kit (Illumina, Inc., San Diego, CA, USA) with 1 µg of total RNA, quantified using Qubit 4.0 (Thermo Fisher Scientific, Waltham, MA, USA), and sequenced on an Illumina NovaSeq X Plus platform (PE150). Differentially expressed genes were identified using DESeq2 with thresholds of |log2FC| ≥ 1 and padjust ≤ 0.05.

2.7. Statistical Analysis

All data were analyzed using SPSS software (Version 22, SPSS Inc., Chicago, IL, USA). For physiological and plate-based assays, one-way analysis of variance (ANOVA) followed by Duncan’s multiple range test was used to determine significant differences among treatments at p < 0.05 after checking homogeneity of variances. Results are expressed as mean ± standard deviation. For transcriptomic analysis, differential expression was performed using DESeq2 with thresholds of |log2FC| ≥ 1 and padjust ≤ 0.05 (FDR-corrected).

3. Results

3.1. Screening and Isolation of Antagonistic Actinomycetes Strains

Forty actinomycete isolates were obtained from the soil samples (Figure 1A) and 20 isolates demonstrated antagonistic activity against N. rosae (Figure 1B). Strain AMJ-169 exhibited the strongest antifungal activity, with a mycelial inhibition rate of 63 ± 1.0% (Figure 1C). Secondary double-plate screening revealed that seven actinomycete isolates produced antagonistic volatiles against N. rosae (Figure 1D). Strain AMJ-169 was the most effective, with a mycelial growth inhibition rate of 70 ± 3.81% (Figure 1E). The above findings prompted further investigation into strain AMJ-169.

3.2. Taxonomic Identification of Strain AMJ-169 as a Novel Antagonistic Actinomycete Species

SEM morphological examination showed that the strain had straight to slightly curved aerial hyphae and elliptical spores (Figure 2A). Cultural characterization showed robust growth on all tested media. The aerial mycelium was pale yellow on Gause No. 1 but white on other media, with no diffusible pigment produced (Table S2). The strain tolerated salinity up to 3% and a pH range of 4–9 (Table S3).
Physiologically, it tested positive for urease activity, starch hydrolysis, decomposition of cellulose, phosphate solubilization, and siderophore production, but was negative for lipase activity, gelatin liquefaction, nitrate reduction, nitrogen fixation, H2S production and IAA synthesis (Table S4). Furthermore, substrate utilization tests confirmed its ability to metabolize 16 carbon sources and 7 nitrogen sources (Table S5). Antibiotic susceptibility profiling revealed that strain AMJ-169 was susceptible to seven antibiotics, including chloramphenicol, lincomycin, ciprofloxacin, erythromycin, tetracycline, gentamicin, and ceftriaxone, as well as resistant to three others, namely trimethoprim-sulfamethoxazole (TMP-SMX), ampicillin, and penicillin G (Benzylpenicillin) (Table S6).
For strain AMJ-169, the complete 16S rRNA gene sequence (1347 bp) was determined and deposited in the NCBI database, where it was assigned the accession number PX884397. Based on EzBioCloud analysis of its 16S rRNA gene sequence, strain AMJ-169 showed a close phylogenetic relationship with type strains of the genus Streptomyces. With 98.44% 16S rRNA gene sequence similarity, strain AMJ-169 was most closely related to Streptomyces roseirectus CRXT-G-22. Initial phylogenetic analysis using the 16S rRNA gene placed strain AMJ-169 in a distinct, fully supported clade (100% bootstrap) with Streptomyces roseirectus CRXT-G-22 (Figure 2B). This close relationship was subsequently confirmed by phylogenomics, as they again formed a clade with 100% bootstrap support in the genome-based tree (Figure 2C).
For genomic taxonomy, nine type strains were selected based on their phylogenetic proximity to strain AMJ-169 in both 16S rRNA and whole-genome sequence trees. The Average Nucleotide Identity (ANI) between AMJ-169 and its closest relative, Streptomyces roseirectus CRXT-G-22, was 83.47%, which is well below the established species delineation threshold of 95–96% for Streptomyces [30]. Moreover, the digital DNA-DNA hybridization (dDDH) value was 33%, also significantly lower than the 70% species threshold [31] (Figure 2D).
The chemotaxonomic characteristics of strain AMJ-169 are described in Table 1. The major menaquinone components were MK-9(H8) (44.566%), followed by MK-10(H4) (41.509%), and MK-9(H6) (13.925%) (Figure S1). The cell wall of strain AMJ-169 was characterized by the presence of LL-diaminopimelic acid (LL-DAP). The major polar lipids were the phospholipids DPG and PE. Additionally, PI, PIM, PL1–5, PGL, GL1–4, AGL, AL1–2, L1–4, and APGL were also identified (Figure 3). The major fatty acids were 16:0 (23.84%), 16:0 iso (20.66%), 14:0 iso (14.8%), and 15:0 anteiso (12.21%) (Table S7). The chemotaxonomic properties of strain AMJ-169 were consistent with its classification within the genus Streptomyces.
Strains AMJ-169ᵀ and CRXT-G-22ᵀ differ distinctly in morphological, physiological and biochemical characteristics: Strain AMJ-169ᵀ produces straight to slightly curved aerial hyphae and elliptical spores with a smooth surface, while strain CRXT-G-22ᵀ forms branched substrate and aerial mycelium and straight chains of smooth-surfaced spores. Additionally, strain AMJ-169ᵀ is unable to liquefy gelatin, degrade Tweens, or reduce nitrate, whereas strain CRXT-G-22ᵀ exhibits gelatin liquefaction, Tween degradation, and nitrate reduction activities. Furthermore, regarding pH and NaCl tolerance, strain AMJ-169ᵀ grows at pH 4.0–9.0 and in the presence of 1–3% NaCl, while strain CRXT-G-22ᵀ grows at pH 5.0–11.0 and tolerates up to 6% NaCl. In terms of pigment production, strain CRXT-G-22ᵀ produces a black soluble pigment on ISP7 medium, a trait not observed in strain AMJ-169ᵀ, which does not produce any diffusible pigment on any of the tested media. The aerial mycelium colors on different ISP media also differ between the two strains: for example, on ISP2, strain AMJ-169ᵀ is white, while strain CRXT-G-22ᵀ is Pale Lumiere Green; on ISP4, strain AMJ-169ᵀ is white, while strain CRXT-G-22ᵀ is Tiber Green; and on ISP7, strain AMJ-169ᵀ is white, while strain CRXT-G-22ᵀ is Pale Fluorite Green (detailed results are shown in Table 2 and Table 3) [32].
Taken together, the combined phenotypic and genotypic data support the proposal that strain AMJ-169 represents a novel species within the genus Streptomyces. Therefore, we propose the name Streptomyces hanimojiang sp. nov. for this novel species. The type strain has been deposited in the Guangdong Microbial Culture Collection Center (GDMCC) under accession number GDMCC 4.497T.

3.3. Genome Analysis and Annotation of Streptomyces sp. nov. AMJ-169

The complete genome of strain AMJ-169 comprises 8,976,836 bp and has an average G + C content of 71.564% (Figure S2A). The assembly consisted of 47 scaffolds and 65 contigs, with a sequencing depth of 743× and completeness of 100%. The genome harbors 7618 predicted coding sequences, along with 2 rRNA, 66 sRNA, and 67 tRNA genes. Furthermore, 13 genomic islands were identified within the genome. COG analysis revealed that 5806 genes could be classified into 24 functional categories, accounting for 76.21% of all protein-coding genes in the genome (Figure S2B). A total of 3604 genes were assigned GO terms, representing 47.31% of all predicted protein-coding genes in the genome (Figure S2C). Functional annotation assigned 5120 protein-coding genes to KEGG metabolic pathways (Figure S2D).
Strain AMJ-169 possesses a rich diversity of biosynthetic potential, with 40 gene clusters identified in its genome. Major categories encompassed amglycycl, betalactone, blactam, butyrolactone, hglE-KS, indole, lanthipeptide-class-I, melanin, NAPAA, NRPS, NRPS-like, phosphonate, pyrrolidine, RiPP-like, siderophore, T1PKS, T2PKS, T3PKS, and terpene. Fourteen of these gene clusters were functionally annotated using MIBiG, of which 9 exhibited a sequence similarity exceeding 80% to known clusters (Figure S3).

3.4. Identification and Antifungal Activity of VOC Components from Strain AMJ-169

All volatile components released by the Streptomyces strain were first identified via GC–MS analysis, and their antifungal activities were further verified using corresponding commercial standards. Four major candidate compounds were detected in the treatment group, namely propanoic acid, 2-methyl-, ethyl ester; (1S)-2,6,6-trimethylbicyclo[3.1.1]hept-2-ene; bicyclo[3.1.1]heptane, 6,6-dimethyl-2-methylene-, (1S)-; and acetic acid, 2-ethylhexyl ester (Figure S4). In the antifungal activity assay, (1S)-(-)-α-pinene was the most effective compound, with inhibition reaching 90.59% (Figure 4A). Therefore, it was selected for EC50 determination against N. rosae. The concentration range was set from 0.0015625 to 0.05 mL/L (compound volume/airspace volume), and the EC50 of (1S)-(-)-α-pinene was determined to be 0.018 mL/L (Figure 4B). Under in vitro conditions, untreated hyphae exhibited smooth surfaces, intact tubular morphology, and extensive mycelial networks, whereas α-pinene treatment resulted in severe hyphal deformation, shrinkage, localized collapse, fragmentation, and loss of structural continuity (Figure 4C,D).

3.5. Efficiency of (1S)-(-)-α-Pinene on Controlling Strawberry Postharvest Rot

To determine the inhibitory activity of (1S)-(-)-α-pinene against N. rosae during strawberry fruit storage, we assessed the pathogen’s infection capacity on fruit treated with varying multiples of the compound’s EC50 concentration. The volatile compound (1S)-(-)-α-pinene significantly reduced rot severity in strawberry fruits in a concentration-dependent manner. A notable reduction in lesion area was observed on treated fruits compared with the control (Figure 5A). At 9 dpi, the lesion areas were 39.072 cm2 (CK), 3.859 cm2 (1× EC50), 3.333 cm2 (2× EC50), 1.761 cm2 (4× EC50), and 0.968 cm2 (6× EC50), corresponding to disease inhibition rates of approximately 90.12%, 91.47%, 95.49%, and 97.52%, respectively (Figure 5C,D). Under the warm, humid, sealed incubation conditions used in this assay, the control fruit developed severe decay covering nearly the entire visible fruit surface, which explains the very large lesion area recorded in the control treatment.

3.6. Effects of (1S)-(-)-α-Pinene on Fungal Hyphae and Host Responses

In situ SEM observation of strawberry fruit surfaces revealed that α-pinene markedly suppressed pathogen colonization and expansion on host tissues. In the control treatment, abundant hyphae formed dense, continuous networks that adhered tightly to the fruit peel, indicating strong colonization ability. In contrast, α-pinene-treated fruit exhibited substantially reduced hyphal abundance, sparse and disorganized hyphal distribution, and obvious morphological abnormalities, which prevented the formation of an intact mycelial network (Figure 5B). Collectively, the in vitro and in situ SEM results indicate that the compound directly damages fungal hyphae and suppresses pathogen attachment, growth, and spread on the fruit surface. Compared with the control, fruit treated with 2× EC50 showed significantly lower malondialdehyde (MDA) content, indicating attenuated lipid peroxidation under pathogen infection (Figure 5E). Superoxide dismutase (SOD) activity was enhanced in treated fruit (Figure 5F), whereas ascorbate peroxidase (APX) activity was lower than that in the control (Figure 5G). These results suggest that α-pinene treatment modulated the oxidative status of strawberry fruit, as evidenced by reduced oxidative damage and altered antioxidant enzyme activities.
Given that α-pinene treatment significantly affected antioxidant enzyme activities and lipid peroxidation, we further examined the associated transcriptomic responses in strawberry fruit. Principal component analysis (PCA) showed a clear separation between α-pinene-treated and diseased control samples, with PC1 explaining 86.80% of the total variation (Figure S5A). Differential expression analysis identified 20,016 significantly differentially expressed genes (|log2FC| ≥ 1, padjust ≤ 0.05), including 9493 up-regulated and 10,523 down-regulated genes (Figure 6A). GO enrichment showed that VOC-responsive genes were mainly involved in metabolic processes, oxidation–reduction processes, and oxidoreductase activity (Figure 6B). KEGG analysis further revealed significant enrichment in carbon metabolism, amino acid metabolism, lipid metabolism, and glutathione metabolism (Figure 6D). WGCNA identified an MEgreen module strongly correlated with α-pinene treatment, and 39 core genes were selected from this module based on network-related criteria and differential-expression relevance (Figure 6C and Table S8). Overall, these results indicate that α-pinene treatment was associated with transcriptomic reprogramming in strawberry fruit, particularly in redox- and metabolism-related pathways.

3.7. Description of S. hanimojiang sp. nov. AMJ-169

S. hanimojiang sp. nov. AMJ-169 (ha.ni.mo.jiang. N.L. masc. adj. hanimojiang, referring to Mojiang Hani Autonomous County, the geographic origin of the type strain) cells are Gram-positive, aerobic, and non-motile actinobacteria forming well-developed, extensively branched substrate mycelium and aerial hyphae. Aerial hyphae are straight to slightly curved and differentiate into chains of elliptical spores. Spore surfaces are smooth, as observed by scanning electron microscopy. The strain grows well on ISP2, ISP3, ISP4, ISP5, ISP6, ISP7, Gause No. 1, and PDA media. Aerial mycelium is pale yellow on Gause No. 1 and white on the other tested media. No diffusible pigments are produced. Growth occurs at pH 4.0–9.0 and in the presence of up to 3% (w/v) NaCl. The strain is positive for urease activity, starch hydrolysis, decomposition of cellulose, phosphate solubilization, and siderophore production, but negative for lipase activity, gelatin liquefaction, nitrate reduction, nitrogen fixation, H2S production, and indole-3-acetic acid (IAA) synthesis.
Chemotaxonomic analysis revealed that the cell wall contains LL-diaminopimelic acid. The predominant menaquinones are MK-9(H8), MK-10(H4), and MK-9(H6). The major polar lipids are diphosphatidylglycerol (DPG) and phosphatidylethanolamine (PE), accompanied by phosphatidylinositol (PI), phosphatidylinositol mannosides (PIM), several unidentified phospholipids, glycolipids, aminoglycolipids, aminolipids, and phosphoglycolipids. The major cellular fatty acids are 16:0, 16:0 iso, 14:0 iso, and 15:0 anteiso.
The type strain, AMJ-169T (GDMCC 4.497T), was isolated from forest soil collected in Mojiang Hani Autonomous County, Pu’er City, Yunnan Province, China. The genome of the type strain is 8,976,836 bp in length with a DNA G + C content of 71.56 mol%. On the basis of phenotypic, chemotaxonomic, and genomic characteristics, strain AMJ-169 represents a novel species within the genus Streptomyces.

4. Discussion

Postharvest rot, caused by N. rosae, critically compromises strawberry fruit quality and leads to severe economic losses, particularly under the warm, humid conditions typical of tropical and subtropical regions [33]. Although synthetic fungicides remain widely used, growing concerns regarding environmental pollution, human health risks, and fungicide resistance have accelerated the development of safe and sustainable alternatives [34,35]. Among these, VOCs from microorganisms present a promising, residue-free strategy for postharvest protection [36]. In this study, we identified (1S)-(-)-α-pinene as the key antifungal VOC from a novel Streptomyces strain AMJ-169, and systematically revealed its dual mechanisms against strawberry postharvest rot via direct fungicidal activity and host-induced resistance.
As prolific producers of structurally diverse secondary metabolites, Streptomyces species are recognized as important sources of bioactive volatiles [36]. In the present study, bioactivity-guided analysis identified (1S)-(-)-α-pinene as the most active antifungal VOC from strain AMJ-169, with an EC50 value of 0.018 mL/L against N. rosae. The antifungal activity observed for α-pinene is consistent with effects reported for other monoterpenes and microbial VOCs, such as 2-phenylethanol, 3-methyl-1-butanol, and andisoamyl acetate, which commonly disrupt fungal membrane integrity and interfere with cellular redox homeostasis [6,7]. However, the exceptionally low EC50 value of (1S)-(-)-α-pinene in this study indicates a higher specific potency than many structurally related volatiles previously characterized from microbial sources. Although these broad mechanisms of action may be shared across the compound class, the potent fumigant activity, favorable safety profile, and residue-minimizing properties of (1S)-(-)-α-pinene distinguish it from other microbial volatiles. Thus, while the observed antifungal efficacy is not exclusive to α-pinene, its superior potency and practical applicability underscore its particular promise as a postharvest preservative. Moreover, fumigation with α-pinene effectively reduced disease severity in strawberry fruit in a concentration-dependent manner. These results indicate that α-pinene may function as an efficient, non-contact, and residue-minimizing preservative candidate for fragile fruits such as strawberries [37]. Its protective effects appear to involve two associated components: direct antifungal activity against the pathogen and modulation of host-associated physiological responses [38]. Direct antifungal activity was supported by scanning electron microscopy, which revealed severe hyphal deformation, shrinkage, and collapse [39]. These structural abnormalities suggest that α-pinene may target the fungal plasma membrane and/or cell wall, possibly by disrupting ergosterol biosynthesis or altering membrane lipid fluidity given its lipophilic nature. Furthermore, the observed interference with redox homeostasis implies that mitochondrial electron transport chains or membrane-bound oxidoreductases could serve as additional intracellular targets. Although these putative cellular targets remain to be experimentally validated, they provide a plausible mechanistic basis for the potent fungicidal activity of (1S)-(-)-α-pinene. In addition, SEM observation of the fruit surface indicated that α-pinene treatment impeded pathogen attachment and colonization [40,41,42]. At the host level, α-pinene treatment reduced MDA accumulation and altered antioxidant enzyme activities, suggesting mitigation of oxidative damage and modulation of redox homeostasis in infected fruit [43].
Transcriptomic analysis further indicated that α-pinene treatment was associated with broad transcriptional changes in strawberry fruit, including significant enrichment of genes involved in phenylpropanoid metabolism, glutathione metabolism, oxidation–reduction processes, and carbon metabolism. These pathways are commonly associated with plant defense, redox buffering, and metabolic adjustment under stress [44,45]. This system, potentially supported by Gamma-glutamyltranspeptidase and membrane-associated MAPEG proteins, detoxifies peroxides while maintaining redox balance, with Aldehyde Dehydrogenases and Aldo-Keto Reductases further neutralizing toxic aldehyde byproducts [46]. The reinforcement of these defense pathways necessitated a reconfiguration of central carbon metabolism. Differential expression of key glycolytic/gluconeogenic enzymes, such as Pyruvate Kinase and Phosphoenolpyruvate Carboxykinase, indicated an adaptive flux adjustment to supply essential ATP, reducing power, and metabolic precursors for biosynthesis [47]. Thiamine pyrophosphate-dependent enzymes likely served as crucial nodes linking this metabolic reprogramming to the antioxidant response [48]. Furthermore, the regulatory scope was broadened by other induced enzymes, including Cytochrome P450s (xenobiotic detoxification), Copper Amine Oxidases (potential signaling), and Histidine Phosphatases [49,50]. However, because direct functional validation of individual genes and pathways was not performed, these results should be interpreted as treatment-associated transcriptomic responses rather than definitive proof of specific downstream mechanisms. The 39 candidate core genes identified by co-expression analysis provide useful targets for future functional studies [44].
Notably, the antifungal compound (1S)-(-)-α-pinene identified in this study was derived from a novel Streptomyces strain with abundant biosynthetic gene clusters, highlighting the potential of underexplored microbial resources for developing green postharvest control agents [51]. Nevertheless, this study has certain limitations. All experiments were conducted under controlled laboratory conditions, and the practical efficiency, stability, and economic feasibility of α-pinene fumigation in commercial postharvest systems remain to be verified. In addition, a matched solvent control was not used for the pure volatile assay, which should be optimized in future work. Fruit quality attributes were not directly measured, and the functions of key candidate genes require further genetic or biochemical verification.

5. Conclusions

In conclusion, the present study identified and characterized a novel actinomycete strain, Streptomyces hanimojiang sp. nov. AMJ-169, which exhibited strong antagonistic activity against Neopestalotiopsis rosae, the causal agent of strawberry postharvest rot. The volatile organic compound (1S)-(-)-α-pinene was identified as the key antifungal component produced by this strain, with strong inhibitory activity against N. rosae in vitro and an EC50 value of 0.018 mL·L−1. Fumigation with (1S)-(-)-α-pinene effectively reduced strawberry fruit rot in a concentration-dependent manner. Mechanistic observations in this study support direct damage to fungal hyphae and suppression of pathogen colonization on fruit surfaces, together with host-associated physiological and transcriptomic responses linked to redox regulation and defense-related metabolism. These findings highlight the potential of α-pinene derived from the novel Streptomyces strain as a promising postharvest biocontrol candidate, while further validation under practical storage conditions is still required.

Supplementary Materials

The following supporting information can be downloaded at https://www.mdpi.com/article/10.3390/horticulturae12050577/s1. Figure S1: Quinone component analysis of strain AMJ-169; Figure S2: Genome analysis of strain AMJ-169; Figure S3: Some compounds with similarity scores above 80% were predicted by antiSMASH; Figure S4: Identification of volatile organic compounds produced by Streptomyces sp. strain AMJ-169; Figure S5: Transcriptomic and co-expression network analysis in strawberry fruit under α-pinene treatment; Table S1: Genome login information of similar strains; Table S2: Characteristics of strain AMJ-169 on different cultural media; Table S3: The growth of strain AMJ-169 under different pH and salt concentration; Table S4: Biochemical characteristics of strain AMJ-169; Table S5: Utilization of carbon and nitrogen sources by actinomycete AMJ-169; Table S6: Antibiotic susceptibility test; Table S7: Fatty acid composition analysis of strain AMJ-169; Table S8: Identification of 39 core genes via co-expression network analysis.

Author Contributions

Writing—review and editing, Conceptualization and funding acquisition, D.C. and D.Z.; writing—original draft preparation, H.Z. and M.Z.; methodology, X.L., J.F. and Y.C.; validation, resources, W.W. and D.Q.; investigation, Z.Z. and K.L.; data curation, H.Z. and Y.Z.; writing—review and editing, T.J., J.X. and D.Z.; project administration, T.J., D.C. and D.Z. All authors have read and agreed to the published version of the manuscript.

Funding

This study was supported by the National Natural Science Foundation of China (32360706), Hainan Provincial Key Research and Development Program (ZDYF2025GXJS137), Hainan Provincial Science and Technology Commissioner Project (KJTP202501); Basic Research Fund of Chinese Academy of Tropical Agricultural Sciences (1630052026004; 1630042025014); China Agriculture Research System (CARS-31) and Innovation Project for Scientific and Technological Talents in Hainan Province (KJRC2023B16).

Data Availability Statement

The original contributions presented in the study are included in the article/Supplementary Materials. Further inquiries can be directed to the corresponding authors.

Conflicts of Interest

The authors declare that they have no conflicts of interest.

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Figure 1. Screening and antifungal evaluation of isolates against Neopestalotiopsis rosae. (A) Morphology of 40 strains on YE medium. (B) Antifungal activities of 20 actinomycetes against N. rosae. (C) Quantification of mycelial inhibition by the 20 strains. (D) Antifungal activity of VOCs produced by 7 strains and Mycelial inhibition rate% (E) when N. rosae. is exposed to VOCs. Different letters indicate significant differences (p < 0.05; Duncan’s test).
Figure 1. Screening and antifungal evaluation of isolates against Neopestalotiopsis rosae. (A) Morphology of 40 strains on YE medium. (B) Antifungal activities of 20 actinomycetes against N. rosae. (C) Quantification of mycelial inhibition by the 20 strains. (D) Antifungal activity of VOCs produced by 7 strains and Mycelial inhibition rate% (E) when N. rosae. is exposed to VOCs. Different letters indicate significant differences (p < 0.05; Duncan’s test).
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Figure 2. Identification of strains AMJ-169. (A) Morphological characteristics of strain AMJ-169. (B) Phylogenetic tree constructed based on the complete 16S rRNA gene sequence (1347 bp) using the neighbor-joining method. (C) Phylogenetic tree constructed based on the concatenated sequences of five housekeeping genes (atpD, gyrB, recA, rpoB, and trpB; 9381 bp) using the neighbor-joining method. Bootstrap values (1000 replicates) are shown at the nodes. Bar = 0.002 or 0.1 substitutions per nucleotide position. (D) ANI (Average Nucleotide Identity) and dDDH (digital DNA-DNA Hybridization) values between strain AMJ-169 and its closely related species.
Figure 2. Identification of strains AMJ-169. (A) Morphological characteristics of strain AMJ-169. (B) Phylogenetic tree constructed based on the complete 16S rRNA gene sequence (1347 bp) using the neighbor-joining method. (C) Phylogenetic tree constructed based on the concatenated sequences of five housekeeping genes (atpD, gyrB, recA, rpoB, and trpB; 9381 bp) using the neighbor-joining method. Bootstrap values (1000 replicates) are shown at the nodes. Bar = 0.002 or 0.1 substitutions per nucleotide position. (D) ANI (Average Nucleotide Identity) and dDDH (digital DNA-DNA Hybridization) values between strain AMJ-169 and its closely related species.
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Figure 3. TLC profile of cell wall lipids and DAP isomers in strain AMJ-169. APu/PM = auxiliary chromogenic reagents; Ninhydrin (amino groups), Molybdenum Blue/Phosphomolybdate (Reagent D, phosphorus groups), 1-Methylnaphthol (glycosyl groups). PL4 < L2: lower migration rate of PL4 than L2. For abbreviations, see the text. LL-/meso-/DD-DAP = diaminopimelic acid isomers.
Figure 3. TLC profile of cell wall lipids and DAP isomers in strain AMJ-169. APu/PM = auxiliary chromogenic reagents; Ninhydrin (amino groups), Molybdenum Blue/Phosphomolybdate (Reagent D, phosphorus groups), 1-Methylnaphthol (glycosyl groups). PL4 < L2: lower migration rate of PL4 than L2. For abbreviations, see the text. LL-/meso-/DD-DAP = diaminopimelic acid isomers.
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Figure 4. Antifungal activity of selected volatiles and α-pinene. (A) Antifungal activities of ethyl isovalerate, (1S)-(-)-α-pinene, (-)-β-pinene, and 2-ethylhexyl acetate. (B) Antifungal activity of (1S)-(-)-α-pinene at different concentrations. (C,D) Effects of (1S)-(-)-α-pinene on hyphal morphology of pathogenic fungi.
Figure 4. Antifungal activity of selected volatiles and α-pinene. (A) Antifungal activities of ethyl isovalerate, (1S)-(-)-α-pinene, (-)-β-pinene, and 2-ethylhexyl acetate. (B) Antifungal activity of (1S)-(-)-α-pinene at different concentrations. (C,D) Effects of (1S)-(-)-α-pinene on hyphal morphology of pathogenic fungi.
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Figure 5. Effects of (1S)-(-)-α-pinene fumigation on disease development and physiological responses in strawberry fruit. (A) Disease symptoms on fruit after inoculation with N. rosae. (B) Mycelial infection on fruit surface observed by SEM. (C) Fruit lesion area at 5, 7, and 9 d after inoculation with N. rosae. Values are means ± SEM (n = 3). Different lowercase letters indicate significant differences among treatments within the same time point (Tukey’s HSD test, p < 0.05). (D) Interaction profile plot illustrating the treatment-by-time interaction. Two-way ANOVA: treatment, F4,30 = 655.5, p < 0.001; time, F2,30= 225.5, p < 0.001; treatment × time interaction, F8,30 = 169.7, p < 0.001. (E–G) Changes in MDA content (E), SOD activity (F), and APX activity (G). Different letters indicate significant differences at the same time point (Duncan’s test, p < 0.05).
Figure 5. Effects of (1S)-(-)-α-pinene fumigation on disease development and physiological responses in strawberry fruit. (A) Disease symptoms on fruit after inoculation with N. rosae. (B) Mycelial infection on fruit surface observed by SEM. (C) Fruit lesion area at 5, 7, and 9 d after inoculation with N. rosae. Values are means ± SEM (n = 3). Different lowercase letters indicate significant differences among treatments within the same time point (Tukey’s HSD test, p < 0.05). (D) Interaction profile plot illustrating the treatment-by-time interaction. Two-way ANOVA: treatment, F4,30 = 655.5, p < 0.001; time, F2,30= 225.5, p < 0.001; treatment × time interaction, F8,30 = 169.7, p < 0.001. (E–G) Changes in MDA content (E), SOD activity (F), and APX activity (G). Different letters indicate significant differences at the same time point (Duncan’s test, p < 0.05).
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Figure 6. Transcriptomic profiling of strawberry fruit in response to αpinene treatment. (A) Volcano plot of DEGs. Red: up-regulated; blue: down-regulated. (B) GO enrichment analysis of DEGs. Top enriched terms in BP, CC, and MF categories. (C) Heatmap of representative core genes. Rows: core genes; columns: treatments/replicates. Color intensity reflects expression levels. (D) KEGG pathway enrichment analysis of DEGs. Most significantly enriched metabolic and signal transduction pathways.
Figure 6. Transcriptomic profiling of strawberry fruit in response to αpinene treatment. (A) Volcano plot of DEGs. Red: up-regulated; blue: down-regulated. (B) GO enrichment analysis of DEGs. Top enriched terms in BP, CC, and MF categories. (C) Heatmap of representative core genes. Rows: core genes; columns: treatments/replicates. Color intensity reflects expression levels. (D) KEGG pathway enrichment analysis of DEGs. Most significantly enriched metabolic and signal transduction pathways.
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Table 1. Chemotaxonomic characteristics of strain AMJ-169. 
Table 1. Chemotaxonomic characteristics of strain AMJ-169. 
CharacteristicAMJ-169CharacteristicAMJ-169
Major menaquinones (%) Major fatty acids (0.5%)
MK9(H8)44.566Sum In Feature 90.91
MK10(H4)41.50917:1 anteiso w9c1.88
MK9 (H6)13.92517:0 iso1.68
Major fatty acids (0.5%) 17:0 anteiso2.45
14:0 iso14.8017:0 cyclo7.57
14:01.46Sum In Feature 50.61
15:0 iso6.57Summed Feature 32.63
15:0 anteiso12.21Summed Feature 50.61
16:1 iso H2.25Summed Feature 90.91
16:0 iso20.66
Sum In Feature 32.63
16:023.84
Table 2. Morphological, physiological and biochemical characteristics of strain AMJ-169 and nearest type strain of Streptomyces. 
Table 2. Morphological, physiological and biochemical characteristics of strain AMJ-169 and nearest type strain of Streptomyces. 
Characteristics12
MorphologyStraight to slightly curved aerial hyphae, elliptical spores with smooth surfaceBranched substrate and aerial mycelium, straight chains of smooth-surfaced spores.
Physiological
pH range for growth4–95–11
NaCl tolerance (%)1–30–6
Gelatin liquefaction−+
Tween degradation−+
Nitrate reduction−+
Strain: 1. Strain AMJ-169, 2. S. roseirectus CRXT-G-22; +, Positive or present; − Negative.
Table 3. Cultural characteristics of strain AMJ-169 and nearest type strain of Streptomyces. 
Table 3. Cultural characteristics of strain AMJ-169 and nearest type strain of Streptomyces. 
MediumAerial Mycelium ColorSubstrate Mycelium ColorSoluble PigmentGrowth
12121212
ISP2WhitePale Lumiere GreenWhiteSnuff BrownNoneNoneGoodGood
ISP3WhiteWhiteWhiteLight Ochraceons-BuffNoneNoneGoodGood
ISP4WhiteTibber GreenWhiteClear Yellow-GreenNoneNoneGoodGood
ISP5WhiteSea-foam GreenWhiteIsabella ColorNoneNoneGoodGood
ISP6WhiteWhiteWhiteClay colorNoneNoneGoodGood
ISP7WhitePale Fluorite GreenWhiteWalnut BrownNoneBlackGoodGood
Gause’s No. 1White Pale yellow None Good
PDAWhite White None Good
Strain: 1. Strain AMJ-169, 2. S. roseirectus CRXT-G-22; ISP2, Trytone-yeast extract agar; ISP3, Oatmeal agar; ISP4, Inorganic salts starch agar; ISP5, Glycerol–asparagine agar; ISP6, Peptone–yeast extract iron agar; ISP7, Tyrosine agar.
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MDPI and ACS Style

Zhang, H.; Zhang, M.; Li, X.; Jing, T.; Zhao, Y.; Chen, Y.; Feng, J.; Zheng, Z.; Wang, W.; Qi, D.; et al. Streptomyces hanimojiang sp. nov. AMJ-169, a Novel Biocontrol Agent Producing Volatile (1S)-(-)-α-Pinene, Suppresses Strawberry Postharvest Rot Caused by Neopestalotiopsis rosae. Horticulturae 2026, 12, 577. https://doi.org/10.3390/horticulturae12050577

AMA Style

Zhang H, Zhang M, Li X, Jing T, Zhao Y, Chen Y, Feng J, Zheng Z, Wang W, Qi D, et al. Streptomyces hanimojiang sp. nov. AMJ-169, a Novel Biocontrol Agent Producing Volatile (1S)-(-)-α-Pinene, Suppresses Strawberry Postharvest Rot Caused by Neopestalotiopsis rosae. Horticulturae. 2026; 12(5):577. https://doi.org/10.3390/horticulturae12050577

Chicago/Turabian Style

Zhang, Huaying, Miaoyi Zhang, Xiaojuan Li, Tao Jing, Yankun Zhao, Yufeng Chen, Junting Feng, Zai Zheng, Wei Wang, Dengfeng Qi, and et al. 2026. "Streptomyces hanimojiang sp. nov. AMJ-169, a Novel Biocontrol Agent Producing Volatile (1S)-(-)-α-Pinene, Suppresses Strawberry Postharvest Rot Caused by Neopestalotiopsis rosae" Horticulturae 12, no. 5: 577. https://doi.org/10.3390/horticulturae12050577

APA Style

Zhang, H., Zhang, M., Li, X., Jing, T., Zhao, Y., Chen, Y., Feng, J., Zheng, Z., Wang, W., Qi, D., Li, K., Xie, J., Chen, D., & Zhou, D. (2026). Streptomyces hanimojiang sp. nov. AMJ-169, a Novel Biocontrol Agent Producing Volatile (1S)-(-)-α-Pinene, Suppresses Strawberry Postharvest Rot Caused by Neopestalotiopsis rosae. Horticulturae, 12(5), 577. https://doi.org/10.3390/horticulturae12050577

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