Biological Control of Plant Diseases Caused by Pathogenic Microorganisms

A special issue of Plants (ISSN 2223-7747). This special issue belongs to the section "Plant Protection and Biotic Interactions".

Deadline for manuscript submissions: closed (30 November 2023) | Viewed by 35320

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Department of Plant Pathology, College of Plant Protection and Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou 510642, China
Interests: biocontrol; biodegradation; quorum sensing; quorum quenching
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Pathogenic microorganisms can cause crop diseases in various plants, leading to a decline in the quality and yield of crops. To more sustainably mitigate the impact of crop diseases on plant health and productivity, there is a need for safer and more eco-friendly strategies than chemical prevention. As an alternative, biological control has received increasing attention in pathogen management. The use of microorganisms or their metabolites to prevent plant diseases is eco-friendly and usually safe for food products. In recent years, quorum quenching based on quorum sensing has been adopted as a potential biocontrol approach for controlling plant diseases due to its relationship with pathogenic multi-antibiotic-resistant microorganisms. This Special Issue aims to collect research dealing with the biological control of plant diseases via quorum quenching, antagonistic microorganisms, or their metabolites that have relevance in phytopathology, microbiology, biochemistry, molecular biology, genetics, chemistry, or any omics-based science. Original investigations as well as concise review manuscripts from experts in the relevant research fields will be considered for publication.

Dr. Shaohua Chen
Guest Editor

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Keywords

  • biocontrol
  • pathogens
  • plant diseases
  • antagonistic microorganisms
  • quorum sensing
  • quorum quenching
  • metabolites
  • metabolism

Published Papers (13 papers)

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Research

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14 pages, 3353 KiB  
Article
The Isolate Pseudomonas multiresinivorans QL-9a Quenches the Quorum Sensing Signal and Suppresses Plant Soft Rot Disease
by Siqi Liu, Xixian Zhu, Zhenchen Yan, Hui Liu, Lianhui Zhang, Wenjuan Chen and Shaohua Chen
Plants 2023, 12(17), 3037; https://doi.org/10.3390/plants12173037 - 24 Aug 2023
Viewed by 1113
Abstract
Quorum sensing (QS) is a communication mechanism used among microorganisms that regulate the population density and behavior by sensing the concentration of signaling molecules. Quorum quenching (QQ), a novel, eco-friendly, and efficient method for disease control, interferes with QS by disturbing the production [...] Read more.
Quorum sensing (QS) is a communication mechanism used among microorganisms that regulate the population density and behavior by sensing the concentration of signaling molecules. Quorum quenching (QQ), a novel, eco-friendly, and efficient method for disease control, interferes with QS by disturbing the production and enzymatic degradation of signaling molecules, blocking communication among microorganisms, and thus has deep potential for use in plant disease control. Pectobacterium carotovorum can cause bacterial soft rot, resulting in yield reduction in a variety of crops worldwide, and can be mediated and regulated by the N-acyl homoserine lactones (AHLs), which are typical signaling molecules. In this study, a novel quenching strain of Pseudomonas multiresinivorans QL-9a was isolated and characterized, and it showed excellent degradation ability against AHLs, degrading 98.20% of N-(-3-oxohexanoyl)-L-homoserine lactone (OHHL) within 48 h. Based on the results of the gas chromatography–mass spectrometer (GC–MS) analysis, a possible pathway was proposed to decompose OHHL into fatty acids and homoserine lactone, in which AHL acylase was involved. Additionally, it has been demonstrated that the QL-9a strain and its crude enzyme are promising biocontrol agents that can considerably reduce the severity of the soft rot disease brought on by P. carotovorum, consequently preventing the maceration of a variety of host plant tissues. All of these results suggest promising applications of the QL-9a strain and its crude enzyme in the control of various plant diseases mediated by AHLs. Full article
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9 pages, 655 KiB  
Article
Biological Control of Severe Fungal Phytopathogens by Streptomyces albidoflavus Strain CARA17 and Its Bioactive Crude Extracts on Lettuce Plants
by Antonia Carlucci, Andrea Sorbo, Donato Colucci and Maria Luisa Raimondo
Plants 2023, 12(10), 2025; https://doi.org/10.3390/plants12102025 - 18 May 2023
Cited by 2 | Viewed by 1321
Abstract
Lettuce crop is an important horticultural crop of several Mediterranean countries, including Italy. The Italian region which is a major producer of lettuce crops is Apulia, where this crop is cultivated in open fields an in greenhouses. Since several microbial pathogens are responsible [...] Read more.
Lettuce crop is an important horticultural crop of several Mediterranean countries, including Italy. The Italian region which is a major producer of lettuce crops is Apulia, where this crop is cultivated in open fields an in greenhouses. Since several microbial pathogens are responsible for important diseases found on lettuce produced in greenhouses, in this study, the experimental activities focused on the most severe fungal soilborne pathogens, i.e., Sclerotinia sclerotiorum and Athelia rolfsii. Their control is often performed with fungicides which cause public concern over the environment and human health. The main aims of this study were to determine the biocontrol efficacy of a Streptomyces strain in vitro and in vivo conditions on lettuce seedlings against Athelia rolfsii and Sclerotinia sclerotiorum as severe fungal soilborne pathogens through the application of its vegetative propagules and putative bioactive crude extracts via filtrate culture. The results obtained confirm a significant effectiveness of CARA17 strain to control the severity of both fungal soilborne pathogens during two different experiments: when it is used as vegetative propagules and as a culture filtrate containing putative bioactive metabolites in vitro and in vivo conditions. These preliminary results demonstrated that the actinomycetes CARA17 strain is valid as a biocontrol agent (BCA) against both the severe phytopathogens used in this study. The biocontrol action performed from the CARA17 strain is clearly and mainly due to the putative bioactive crude extracts produced, but further studies are necessary to identify which metabolites (polyphenols, terpenes, fatty acids, etc.) are produced from this Streptomyces strain. Full article
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15 pages, 2065 KiB  
Article
Chemical Identification of Secondary Metabolites from Rhizospheric Actinomycetes Using LC-MS Analysis: In Silico Antifungal Evaluation and Growth-Promoting Effects
by Hazem S. Elshafie, Laura De Martino, Carmen Formisano, Lucia Caputo, Vincenzo De Feo and Ippolito Camele
Plants 2023, 12(9), 1869; https://doi.org/10.3390/plants12091869 - 2 May 2023
Cited by 13 | Viewed by 2618
Abstract
The rhizosphere is a rich source of actinomycetes which can produce several potential biologically active secondary metabolites. The principal goal for this research is to extract, purify, and characterize the bioactive secondary metabolites produced by three different strains of actinomycetes isolated from the [...] Read more.
The rhizosphere is a rich source of actinomycetes which can produce several potential biologically active secondary metabolites. The principal goal for this research is to extract, purify, and characterize the bioactive secondary metabolites produced by three different strains of actinomycetes isolated from the rhizosphere of rosemary, black locust, and olive. The plant growth-promoting effect (PGPE) of the studied strains of actinomycetes on Ocimum basilicum L. (basil) and the disease-control effect on necrotic stem lesions of “black leg” caused by Fusarium tabacinum on basil were evaluated in silico. The cell-free culture filtrates from the studied actinomycetes isolates were evaluated in vitro for their antimicrobial activity against some common phytopathogens. The secondary metabolites obtained from the cell-free culture filtrates have been chemically characterized using high-resolution electrospray ionization of liquid-chromatography/mass-spectrometric detection (ESI-(HR)Orbitrap-MS). Results of the in silico trial showed that all studied isolates demonstrated PGPE on basil seedlings, improved some eco-physiological characteristics, and reduced the disease incidence of F. tabacinum. The extracted metabolites from the studied actinomycetes demonstrated antimicrobial activity in a Petri-plates assay. The chemical analysis revealed the presence of 20 different components. This research emphasizes how valuable the examined isolates are for producing bioactive compounds, indicating their putative antimicrobial activity and their potential employment as fungal biocontrol agents. In particular, the obtained results revealed the possibility of green synthesis of some important secondary metabolites, such as N-Acetyl-l-histidinol, Rhizocticin A, and Eponemycin, from actinomycetes. The bioactive metabolites may be successively used to develop novel bio-formulations for both crop protection and/or PGPE. Full article
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20 pages, 2872 KiB  
Article
Native Trichoderma Induced the Defense-Related Enzymes and Genes in Rice against Xanthomonas oryzae pv. oryzae (Xoo)
by Md. Rashidul Islam, Rabin Chowdhury, Arpita Saha Roy, Md. Nazmul Islam, Mamuna Mahjabin Mita, Samrin Bashar, Plabon Saha, Ridwan Ahmed Rahat, Mehedi Hasan, Mst. Arjina Akter, Md. Zahangir Alam and Md. Abdul Latif
Plants 2023, 12(9), 1864; https://doi.org/10.3390/plants12091864 - 30 Apr 2023
Cited by 3 | Viewed by 2694
Abstract
The application of Trichoderma is a form of biological control that has been effective in combating Xanthomonas oryzae pv. oryzae, the causative agent of the devastating disease known as bacterial blight of rice. In this present study, four strains of Trichoderma, viz., [...] Read more.
The application of Trichoderma is a form of biological control that has been effective in combating Xanthomonas oryzae pv. oryzae, the causative agent of the devastating disease known as bacterial blight of rice. In this present study, four strains of Trichoderma, viz., T. paraviridescens (BDISOF67), T. erinaceum (BDISOF91), T. asperellum (BDISOF08), and T. asperellum (BDISOF09), were collected from the rice rhizosphere and used to test their potentiality in reducing bacterial blight. The expression patterns of several core defense-related enzymes and genes related to SA and JA pathways were studied to explore the mechanism of induced resistance by those Trichoderma strains. The results primarily indicated that all Trichoderma were significantly efficient in reducing the lesion length of the leaf over rice check variety (IR24) through enhancing the expression of core defense-related enzymes, such as PAL, PPO, CAT, and POD activities by 4.27, 1.77, 3.53, and 1.57-fold, respectively, over control. Moreover, the results of qRT-PCR exhibited an upregulation of genes OsPR1, OsPR10, OsWRKY45, OsWRKY62, OsWRKY71, OsHI-LOX, and OsACS2 after 24 h of inoculation with all tested Trichoderma strains. However, in the case of RT-PCR, no major changes in OsPR1 and OsPR10 expression were observed in plants treated with different Trichoderma strains during different courses of time. Collectively, Trichoderma induced resistance in rice against X. oryzae pv. oryzae by triggering these core defense-related enzymes and genes associated with SA and JA pathways. Full article
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26 pages, 4657 KiB  
Article
Exploring the Biocontrol Efficacy of Trichoderma spp. against Rigidoporus microporus, the Causal Agent of White Root Rot Disease in Rubber Trees (Hevea brasiliensis)
by Wen Ze Go, Kit Ling Chin, Paik San H’ng, Mui Yun Wong, Chuan Li Lee and Pui San Khoo
Plants 2023, 12(5), 1066; https://doi.org/10.3390/plants12051066 - 27 Feb 2023
Cited by 7 | Viewed by 2491
Abstract
Rigidoporus microporus, which causes white root rot disease (WRD) in Hevea brasiliensis, is a looming threat to rubber plantation in Malaysia. The current study was conducted to determine and evaluate the efficiency of fungal antagonists (Ascomycota) against R. microporus in rubber trees under [...] Read more.
Rigidoporus microporus, which causes white root rot disease (WRD) in Hevea brasiliensis, is a looming threat to rubber plantation in Malaysia. The current study was conducted to determine and evaluate the efficiency of fungal antagonists (Ascomycota) against R. microporus in rubber trees under laboratory and nursery conditions. A total of 35 fungal isolates established from the rubber tree rhizosphere soil were assessed for their antagonism against R. microporus by the dual culture technique. Trichoderma isolates can inhibit the radial growth of R. microporus by 75% or more in the dual culture test. Strains of T. asperellum, T. koningiopsis, T. spirale, and T. reesei were selected to assess the metabolites involved in their antifungal activity. Results indicated that T. asperellum exhibited an inhibitory effect against R. microporus in both volatile and non-volatile metabolite tests. All Trichoderma isolates were then tested for their ability in producing hydrolytic enzymes such as chitinase, cellulase and glucanase, indole acetic acid (IAA), siderophores production, and phosphate solubilization. From the positive results of the biochemical assays, T. asperellum and T. spirale were selected as the biocontrol candidates to be further tested in vivo against R. microporus. The nursery assessments revealed that rubber tree clone RRIM600 pretreated with only T. asperellum or with the combination of T. asperellum and T. spirale was able to reduce the disease severity index (DSI) and exert higher suppression of R. microporus compared to other pretreated samples, with the average DSI below 30%. Collectively, the present study demonstrates that T. asperellum represents a potential biocontrol agent that should be further explored to control R. microporus infection on rubber trees. Full article
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15 pages, 1148 KiB  
Article
Isolation and Screening of Antagonistic Endophytes against Phytophthora infestans and Preliminary Exploration on Anti-oomycete Mechanism of Bacillus velezensis 6-5
by Jiaomei Zhang, Xiaoqing Huang, Yuqin Hou, Xiangning Xia, Zhiming Zhu, Airong Huang, Shun Feng, Peihua Li, Lei Shi and Pan Dong
Plants 2023, 12(4), 909; https://doi.org/10.3390/plants12040909 - 17 Feb 2023
Cited by 8 | Viewed by 2288
Abstract
Phytophthora infestans, the notorious pathogen of potato late blight, leads to a severe decline in potato yields and even harvest failure. We isolated 201 endophytic isolates from healthy root tissues of potatoes, among which 41 showed strong antagonistic activity against P. infestans [...] Read more.
Phytophthora infestans, the notorious pathogen of potato late blight, leads to a severe decline in potato yields and even harvest failure. We isolated 201 endophytic isolates from healthy root tissues of potatoes, among which 41 showed strong antagonistic activity against P. infestans. Further, the tolerance to stress and the potential application against potato late blight of these antagonistic isolates were tested. Most of them were extremely tolerant to stresses such as acid–alkali, temperature, UV, salt, and heavy metal stress. However, some antagonistic isolates with excellent stress tolerance might be pathogenic to potatoes. Combining the screening results, a total of 14 endophytes had excellent comprehensive performance in all the tests. In this paper, the endophyte 6-5 was selected among them for the preliminary exploration of the anti-oomycete mechanism. Analysis of the 16S rDNA sequence revealed that 6-5 had a high homology to the corresponding sequence of Bacillus velezensis (99.72%) from the NCBI database. Endophyte 6-5 significantly inhibited the mycelial growth of P. infestans, with an inhibition rate of over 90% in vitro assays, and deformed the hyphal phenotype of P. infestans. In addition, endophyte 6-5 could secrete protease and cellulase, and produce antagonistic substances with high thermal stability, which might be helpful to its antagonistic activity against P. infestans. Furthermore, it was demonstrated that 6-5 had the ability to improve the resistance of potato tubers to late blight. In short, our study described the process of isolating and screening endophytes with antagonistic activity against P. infestans from potato roots, and further explored the potential of biocontrol candidate strain 6-5 in potato late blight control. Full article
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15 pages, 2166 KiB  
Article
Antagonistic Strain Bacillus halotolerans Jk-25 Mediates the Biocontrol of Wheat Common Root Rot Caused by Bipolaris sorokiniana
by Kun Kang, Zhipeng Niu, Wei Zhang, Shan Wei, Yangyong Lv and Yuansen Hu
Plants 2023, 12(4), 828; https://doi.org/10.3390/plants12040828 - 13 Feb 2023
Cited by 5 | Viewed by 2245
Abstract
Common root rot caused by Bipolaris sorokiniana infestation in wheat is one of the main reasons for yield reduction in wheat crops worldwide. The bacterium strain JK-25 used in the current investigation was isolated from wheat rhizosphere soil and was later identified as [...] Read more.
Common root rot caused by Bipolaris sorokiniana infestation in wheat is one of the main reasons for yield reduction in wheat crops worldwide. The bacterium strain JK-25 used in the current investigation was isolated from wheat rhizosphere soil and was later identified as Bacillus halotolerans based on its morphological, physiological, biochemical, and molecular properties. The strain showed significant antagonism to B. sorokiniana, Fusarium oxysporum, Fusarium graminearum, and Rhizoctonia zeae. Inhibition of B. sorokiniana mycelial dry weight and spore germination rate by JK-25 fermentation supernatant reached 60% and 88%, respectively. The crude extract of JK-25 was found, by Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS), to contain the surfactin that exerted an inhibitory effect on B. sorokiniana. The disruption of mycelial cell membranes was observed under laser scanning confocal microscope (LSCM) after treatment of B. sorokiniana mycelium with the crude extract. The antioxidant enzyme activity of B. sorokiniana was significantly reduced and the oxidation product malondialdehyde (MDA) content increased after treatment with the crude extract. The incidence of root rot was significantly reduced in pot experiments with the addition of JK-25 culture fermentation supernatant, which had a significant biological control effect of 72.06%. Its ability to produce siderophores may help to promote wheat growth and the production of proteases and pectinases may also be part of the strain’s role in suppressing pathogens. These results demonstrate the excellent antagonistic effect of JK-25 against B. sorokiniana and suggest that this strain has great potential as a resource for biological control of wheat root rot strains. Full article
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13 pages, 2498 KiB  
Article
Biological Control of Aspergillus flavus by the Yeast Aureobasidium pullulans In Vitro and on Tomato Fruit
by Izabela Podgórska-Kryszczuk
Plants 2023, 12(2), 236; https://doi.org/10.3390/plants12020236 - 4 Jan 2023
Cited by 9 | Viewed by 4534
Abstract
Aspergillus flavus is an important pathogenic fungus affecting many crops and is one of the main sources of their aflatoxin contamination. The primary method of limiting this pathogen is using chemical fungicides, but researchers focus on searching for other effective agents for its [...] Read more.
Aspergillus flavus is an important pathogenic fungus affecting many crops and is one of the main sources of their aflatoxin contamination. The primary method of limiting this pathogen is using chemical fungicides, but researchers focus on searching for other effective agents for its control due to many disadvantages and limitations of these agrochemicals. The results obtained in the present study indicate the high potential of two yeast strains, Aureobasidium pullulans PP4 and A. pullulans ZD1, in the biological control of A. flavus. Under in vitro conditions, mycelial growth was reduced by 53.61% and 63.05%, and spore germination was inhibited by 68.97% and 79.66% by ZD1 and PP4 strains, respectively. Both strains produced the lytic enzymes chitinase and β-1,3-glucanase after 5 days of cultivation with cell wall preparations (CWP) of A. flavus in the medium as a carbon source. In addition, the tested yeasts showed the ability to grow over a wide range of temperatures (4–30 °C), pH (4–11), and salinity (0–12%) and showed tolerance to fungicides at concentrations corresponding to field conditions. Both isolates tested were highly tolerant to cupric oxychloride, showing biomass gains of 85.84% (ZD1) and 87.25% (PP4). Biomass growth in the presence of fungicides azoxystrobin was 78.71% (ZD1) and 82.65% (PP4), while in the presence of difenoconazole, it was 70.09% (ZD1) and 75.25% (PP4). The yeast strains were also tested for antagonistic effects against A. flavus directly on tomato fruit. Both isolates acted effectively by reducing lesion diameter from 29.13 mm (control) to 8.04 mm (PP4) and 8.83 mm (ZD1). Full article
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12 pages, 2841 KiB  
Article
Microbial Community Succession Associated with Poplar Wood Discoloration
by Xiaohua Zhang, Hao Liu, Heming Han, Bo Zhang, Cunzhi Zhang, Jian He, Shunpeng Li and Hui Cao
Plants 2022, 11(18), 2420; https://doi.org/10.3390/plants11182420 - 16 Sep 2022
Cited by 4 | Viewed by 1609
Abstract
Microbes are common inhabitants of wood, but little is known about the relationship between microbial community dynamics during wood discoloration. This study uses simulation experiments to examine the changes in the microbial communities in poplar wood at different succession stages. The composition and [...] Read more.
Microbes are common inhabitants of wood, but little is known about the relationship between microbial community dynamics during wood discoloration. This study uses simulation experiments to examine the changes in the microbial communities in poplar wood at different succession stages. The composition and structure of the microbial communities changed significantly in different successional stages, with an overarching pattern of bacterial diversity decreasing and fungal diversity increasing from the early to the late successional stages. Nevertheless, succession did not affect the composition of the microbial communities at the phylum level: Proteobacteria and Acidobacteria dominated the bacterial communities, while Ascomycota and Basidiomycota dominated the fungal communities. However, at the genus level, bacterial populations of Sphingomonas and Methylobacterium, and fungal populations of Sphaeropsis were significantly more prevalent in later successional stages. Stochastic assembly processes were dominant in the early successional stages for bacteria and fungi. However, variable selection played a more critical role in the assembly processes as succession proceeded, with bacterial communities evolving towards more deterministic processes and fungal communities towards more stochastic processes. Altogether, our results suggest that bacteria and fungi exhibit different ecological strategies in poplar wood. Understanding those strategies, the resulting changes in community structures over time, and the relationship to the different stages of poplar discoloration, is vital to the biological control of that discoloration. Full article
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15 pages, 3847 KiB  
Article
Target Mechanism of Iturinic Lipopeptide on Differential Expression Patterns of Defense-Related Genes against Colletotrichum acutatum in Pepper
by Joon Seong Park, Gwang Rok Ryu and Beom Ryong Kang
Plants 2022, 11(9), 1267; https://doi.org/10.3390/plants11091267 - 9 May 2022
Cited by 7 | Viewed by 2023
Abstract
Bacillus subtilis KB21 is an isolate with broad spectrum antifungal activity against plant pathogenic fungi. Our aim was to produce and purify antifungal lipopeptides via fermentation using B. subtilis KB21 and verify their antifungal mechanism against pepper anthracnose. When the KB21 strain was [...] Read more.
Bacillus subtilis KB21 is an isolate with broad spectrum antifungal activity against plant pathogenic fungi. Our aim was to produce and purify antifungal lipopeptides via fermentation using B. subtilis KB21 and verify their antifungal mechanism against pepper anthracnose. When the KB21 strain was cultured in tryptic soy broth medium, the antifungal activity against pepper anthracnose correlated with biosurfactant production. However, there was no antifungal activity when cultured in Luria-Bertani medium. KB21 filtrates showed the highest degree of inhibition of mycelia (91.1%) and spore germination (98.9%) of Colletotrichum acutatum via increases in the biosurfactant levels. Using liquid chromatography-mass spectrometry (LC-MS) and LC-tandem MS (LC-MS/MS) analyses, the component with antifungal activity in the fermentation medium of the KB21 strain was determined to be the cyclic lipopeptide (CLP) antibiotic, iturin A. When the iturin fractions were applied to pepper fruits inoculated with conidia of C. acutatum, the lesion diameter and hyphal growth on the fruit were significantly suppressed. In addition, iturin CLP elevated the gene expression of PAL, LOX, and GLU in the treatments both with and without following fungal pathogens. Overall, the results of this study show that iturin CLPs from B. subtilis KB21 may be potential biological control agents for plant fungal diseases. Full article
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19 pages, 3801 KiB  
Article
Isolation of the Novel Strain Bacillus amyloliquefaciens F9 and Identification of Lipopeptide Extract Components Responsible for Activity against Xanthomonas citri subsp. citri
by Xin Wang, Liqiong Liang, Hang Shao, Xiaoxin Ye, Xiaobei Yang, Xiaoyun Chen, Yu Shi, Lianhui Zhang, Linghui Xu and Junxia Wang
Plants 2022, 11(3), 457; https://doi.org/10.3390/plants11030457 - 7 Feb 2022
Cited by 13 | Viewed by 3591
Abstract
Citrus canker, caused by Xanthomonas citri subsp. citri (Xcc), is a quarantine disease that seriously affects citrus production worldwide. The use of microorganisms and their products for biological control has been proven to be effective in controlling Xanthomonas disease. In this [...] Read more.
Citrus canker, caused by Xanthomonas citri subsp. citri (Xcc), is a quarantine disease that seriously affects citrus production worldwide. The use of microorganisms and their products for biological control has been proven to be effective in controlling Xanthomonas disease. In this study, a novel Xcc antagonistic strain was isolated and identified as Bacillus amyloliquefaciens F9 by morphological and molecular analysis. The lipopeptide extract of B. amyloliquefaciens F9 (F9LE) effectively inhibited the growth of Xcc in an agar diffusion assay and restrained the occurrence of canker lesions in a pathogenicity test under greenhouse conditions. Consistent with these findings, F9LE treatment significantly inhibited the production of extracellular enzymes in Xcc cells and induced cell wall damage, with leakage of bacterial contents revealed by scanning electron microscopy and transmission electron microscopy analyses. In addition, F9LE also showed strong antagonistic activity against a wide spectrum of plant pathogenic bacteria and fungi. Furthermore, using electrospray ionization mass spectrometry analysis, the main antimicrobial compounds of strain F9 were identified as three kinds of lipopeptides, including homologues of surfactin, fengycin, and iturin. Taken together, our results show that B. amyloliquefaciens F9 and its lipopeptide components have the potential to be used as biocontrol agents against Xcc, and other plant pathogenic bacteria and fungi. Full article
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18 pages, 1724 KiB  
Article
Biological Control of Celery Powdery Mildew Disease Caused by Erysiphe heraclei DC In Vitro and In Vivo Conditions
by Hamada F. A. Ahmed, Mahmoud F. Seleiman, Adel M. Al-Saif, Maha A. Alshiekheid, Martin L. Battaglia and Ragab S. Taha
Plants 2021, 10(11), 2342; https://doi.org/10.3390/plants10112342 - 29 Oct 2021
Cited by 20 | Viewed by 3176
Abstract
The present study aimed to investigate the potentiality of certain biocontrol agents, namely Bacillus subtilis, B. pumilus, B. megaterium, Pseudomonas fluorescens, Serratia marcescens, Trichoderma album, T. harzianum and T. viride, as well as the synthetic fungicide [...] Read more.
The present study aimed to investigate the potentiality of certain biocontrol agents, namely Bacillus subtilis, B. pumilus, B. megaterium, Pseudomonas fluorescens, Serratia marcescens, Trichoderma album, T. harzianum and T. viride, as well as the synthetic fungicide difenoconazole to control celery powdery mildew caused by Erysiphe heraclei DC, in vitro (against conidia germination and germ tube length of E. heraclei) and in vivo (against disease severity and AUDPC). In vitro, it was found that the antifungal activity of the tested biocontrol agents significantly reduced the germination percentage of the conidia and germ tube length of the pathogen. The reduction in conidia germination ranged between 88.2% and 59.6% as a result of the treatment with B. subtilis and T. album, respectively compared with 97.1% by the synthetic fungicide difenoconazole. Moreover, the fungicide achieved the highest reduction in germ tube length (92.5%) followed by B. megaterium (82.0%), while T. album was the least effective (62.8%). Spraying celery plants with the tested biocontrol agents in the greenhouse significantly reduced powdery mildew severity, as well as the area under the disease progress curve (AUDPC), after 7, 14, 21 and 28 days of application. In this regard, B. subtilis was the most efficient followed by B. pumilus, S. marcescens and B. megaterium, with 80.1, 74.4, 73.2 and 70.5% reductions in disease severity, respectively. In AUDPC, reductions of those microorganisms were 285.3, 380.9, 396.7 and 431.8, respectively, compared to 1539.1 in the control treatment. On the other hand, the fungicide difenoconazole achieved maximum efficacy in reducing disease severity (84.7%) and lowest AUDPC (219.3) compared to the other treatments. In the field, all the applied biocontrol agents showed high efficiency in suppressing powdery mildew on celery plants, with a significant improvement in growth and yield characteristics. In addition, they caused an increase in the concentration of leaf pigments, and the activities of defense-related enzymes such as peroxidase (PO) and polyphenol oxidase (PPO) and total phenol content (TPC). In conclusion, the results showed the possibility of using tested biocontrol agents as eco-friendly alternatives to protect celery plants against powdery mildew. Full article
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Review

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23 pages, 1704 KiB  
Review
Biotechnological Tools to Elucidate the Mechanism of Plant and Nematode Interactions
by Arshad Khan, Shaohua Chen, Saba Fatima, Lukman Ahamad and Mansoor Ahmad Siddiqui
Plants 2023, 12(12), 2387; https://doi.org/10.3390/plants12122387 - 20 Jun 2023
Cited by 1 | Viewed by 4137
Abstract
Plant-parasitic nematodes (PPNs) pose a threat to global food security in both the developed and developing worlds. PPNs cause crop losses worth a total of more than USD 150 billion worldwide. The sedentary root-knot nematodes (RKNs) also cause severe damage to various agricultural [...] Read more.
Plant-parasitic nematodes (PPNs) pose a threat to global food security in both the developed and developing worlds. PPNs cause crop losses worth a total of more than USD 150 billion worldwide. The sedentary root-knot nematodes (RKNs) also cause severe damage to various agricultural crops and establish compatible relationships with a broad range of host plants. This review aims to provide a broad overview of the strategies used to identify the morpho-physiological and molecular events that occur during RKN parasitism. It describes the most current developments in the transcriptomic, proteomic, and metabolomic strategies of nematodes, which are important for understanding compatible interactions of plants and nematodes, and several strategies for enhancing plant resistance against RKNs. We will highlight recent rapid advances in molecular strategies, such as gene–silencing technologies, RNA interference (RNAi), and small interfering RNA (siRNA) effector proteins, that are leading to considerable progress in understanding the mechanism of plant–nematode interactions. We also take into account genetic engineering strategies, such as targeted genome editing techniques, the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR associated protein 9 (Cas9) (CRISPR/Cas-9) system, and quantitative trait loci (QTL), to enhance the resistance of plants against nematodes. Full article
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