Isolation and identification of Arbutus unedo L. fungi endophytes and biological control of Phytophthora cinnamomi in vitro

Cystathionine γ-lyase is an essential biocontrol-positive regulator of Trichoderma gamsii strain TC788

Some Trichoderma strains have been widely used in agriculture due to their biological control functions against plant pathogens. However, only a few intracellular biocontrol-related factors of them were explored. In this study, T. gamsii strain TC788 was discovered possessing comprehensive antagonistic capacity to the fungal phytopathogen Rhizoctonia solani causing damping-off disease of pepper, in which cystathionine γ-lyase is proved to be an essential biocontrol positive regulator as evidenced by combined analyses of transcriptome and proteome, proteins interaction network, and gene homologous recombination. Overexpression of cystathionine γ-lyase significantly up-regulated expression levels of six pathway proteins and enzyme activities of secreted proteins associated with biocontrol. It also increased contents of cysteine and hydrogen sulfide in enriched pathway of cysteine and methionine metabolism, and improved concentration of the main volatile organic compound, 6‑pentyl‑2H‑pyran‑2‑one, by 4.18 times. Pot experiments further confirmed that overexpressed strain of TC788 enhanced inhibiting ability against R. solani, promoted growth indicators, and induced systemic resistance of pepper seedlings compared with wild type strain. This work provides theoretical bases of biocontrol effects performed by strain TC788 against the phytopathogen, and explores preliminarily interaction between the strain and pepper plant.

Isolation and evaluation of growth-promoting endophytic bacteria from Zanthoxylum dissitum Hemsl

The slow growth rate of Zanthoxylum dissitum Hemsl. (Zanthoxylum) is the important factor causing the scarcity of its available wild resource. It has been reported that the plant endophytes can promote the plant growth and the synthesis of secondary metabolitesby by enhancing the efficiency of nutrient absorption by plants and regulating plant hormones. It is important to explore the promoting effects of endophytes on the growth of Zanthoxylum. The application of high-throughput sequencing technology in this study revealed the presence of three phyla, five classes, seven orders, and eleven genera of endophytic bacteria in Zanthoxylum. The most prevalent phyla, classes, orders, and genera were identified respectively as Proteobacteria, Gammaproteobacteria, Burkholderiales, and Pseudomonas. In this study, an endophytic growth-promoting bacterium was isolated and identified as Sphingomonas sp. The results revealed that the bacterium exhibited robust nitrogen fixation, phosphorus solubilization, and effective siderophore production capabilities. The phosphate solubilization index (SI) was found to be (1.266 ± 0.0157). Following a 48-h incubation period in an inorganic phosphorus liquid medium (PKO), the concentration of auxin (IAA) and gibberellin (GA) reached their highest levels, at (138.145 ± 65.111) μg/mL and (805.74 ± 123.86) μg/mL, respectively. Moreover, the study showed that the endophytic bacteria markedly enhanced the germination potential and rate of sorghum seeds, and promoted significantly the growth of the tissue culture seedlings of Zanthoxylum.

Inhibition and biocontrol potential of Ochrobactrum pseudogrignonense NC1 against four Phytophthora species

Phytophthora species are highly destructive soilborne oomycetes pathogens that spread through infested soil and water. Ochrobactrum pseudogrignonense NC1 has been shown to inhibit plant parasitic nematodes via volatile organic compounds (VOCs). In this study, we investigated the inhibitory effect of O. pseudogrignonense NC1 against four Phytophthora species on agar plates and in vivo bioassay. We found that NC1 significantly inhibited the mycelial growth and zoospore production of all four species of Phytophthora in a dose-dependent manner. The half maximal inhibitory concentration (IC50) values for inhibition of mycelial growth (or zoospore production) were 26% (14.8%), 18.9% (14.2%), 20.3% (8.3%) and 46.9% (4%) for Phytophthora capsici Leonian, Phytophthora infestans, Phytophthora parasitica var. nicotiana and Phytophthora sojae, respectively. The biocontrol efficiency of NC1 was 46.3% in pepper seedlings against P. capsici, almost 100% in potato tubers against P. infestans, 60% in tomato leave against P. parasitica and 100% in soybean leave against P. sojae, respectively. Our findings suggest that O. pseudogrignonense NC1 has great potential as a biocontrol agent for managing Phytophthora diseases.

Important soil microbiota's effects on plants and soils: a comprehensive 30-year systematic literature review

Clarifying the relationship between soil microorganisms and the plant-soil system is crucial for encouraging the sustainable development of ecosystems, as soil microorganisms serve a variety of functional roles in the plant-soil system. In this work, the influence mechanisms of significant soil microbial groups on the plant-soil system and their applications in environmental remediation over the previous 30 years were reviewed using a systematic literature review (SLR) methodology. The findings demonstrated that: (1) There has been a general upward trend in the number of publications on significant microorganisms, including bacteria, fungi, and archaea. (2) Bacteria and fungi influence soil development and plant growth through organic matter decomposition, nitrogen, phosphorus, and potassium element dissolution, symbiotic relationships, plant growth hormone production, pathogen inhibition, and plant resistance induction. Archaea aid in the growth of plants by breaking down low-molecular-weight organic matter, participating in element cycles, producing plant growth hormones, and suppressing infections. (3) Microorganism principles are utilized in soil remediation, biofertilizer production, denitrification, and phosphorus removal, effectively reducing environmental pollution, preventing soil pathogen invasion, protecting vegetation health, and promoting plant growth. The three important microbial groups collectively regulate the plant-soil ecosystem and help maintain its relative stability. This work systematically summarizes the principles of important microbial groups influence plant-soil systems, providing a theoretical reference for how to control soil microbes in order to restore damaged ecosystems and enhance ecosystem resilience in the future.

Isolation and Screening of Antagonistic Endophytes against Phytophthora infestans and Preliminary Exploration on Anti-oomycete Mechanism of Bacillus velezensis 6-5

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.

Protease Produced by Endophytic Fungi: A Systematic Review

The purpose of this systematic review was to identify the available literature of production, purification, and characterization of proteases by endophytic fungi. There are few complete studies that entirely exhibit the production, characterization, and purification of proteases from endophytic fungi. This study followed the PRISMA, and the search was conducted on five databases: PubMed, PMC, Science Direct, Scopus Articles, and Web of Science up until 18 May 2021, with no time or language restrictions. The methodology of the selected studies was evaluated using GRADE. Protease production, optimization, purification, and characterization were the main evaluated outcomes. Of the 5540 initially gathered studies, 15 met the inclusion criteria after a two-step selection process. Only two studies optimized the protease production using statistical design and two reported enzyme purification and characterization. The genus Penicillium and Aspergillus were the most cited among the eleven different genera of endophytic fungi evaluated in the selected articles. Six studies proved the ability of some endophytic fungi to produce fibrinolytic proteases, demonstrating that endophytic fungi can be exploited for the further production of agents used in thrombolytic therapy. However, further characterization and physicochemical studies are required to evaluate the real potential of endophytic fungi as sources of industrial enzymes.