Many studies on plant biostimulants and organic fertilizers have been focused on the ability of these products to increase crop productivity and ameliorate crop tolerance to abiotic stresses. ...However, little information is available on their effect on plant microbiota, whereas it is well known that microorganisms associated with plant play crucial roles on the health and productivity of their host. The aim of this study was to evaluate the effect of a vegetal-derived protein hydrolysate (PH), a vegetal-derived PH enriched with copper (Cu-PH), and a tropical plant extract enriched with micronutrients (PE) on shoot growth and the epiphytic bacterial population of lettuce plants and the ability of these products to enhance the growth of beneficial or harmful bacteria. The three plant-derived products enhanced shoot biomass of lettuce plants indicating a biostimulant effect of the products. Data obtained using culture-independent (Terminal Restriction Fragment Length Polymorphism and Next Generation Sequencing) and culture-dependent approaches indicated that foliar application of commercial products altered the composition of the microbial population and stimulated the growth of specific bacteria belonging to
,
,
, and
genus. Data presented in this work demonstrated that some of these strains exhibited potential plant growth-promoting properties and/or biocontrol activity against fungi and bacteria phytopathogens including
,
, and
species. No indication of potential health risks associated to the enrichment of human or plant bacterial pathogens emerged by the analysis of the microbiota of treated and no-treated plants. Overall, the findings presented in this study indicate that the commercial organic-based products can enhance the growth of beneficial bacteria occurring in the plant microbiota and signals produced by these bacteria can act synergistically with the organic compounds to enhance plant growth and productivity.
Apple ring rot, one of the most common apple postharvest diseases during storage, is caused by
. Fungicide application is the most widely used method to control this disease, but the increasing ...environmental and food safety concerns greatly limit their use. The present study aimed to examine the biocontrol activity and underlying action mechanism of
strain Pl7 against
. The results revealed that
strain Pl7 exhibited strong inhibitory activity against
by 69%
. The culture filtrate of strain Pl7 possessed cellulase, β-1, 3-glucanase, protease activity and mediated the antifungal activity against
. Further analysis demonstrated that culture filtrate of strain Pl7 could cause cell membrane permeabilization of
. Apple fruit suffering from ring rot induced by a carbendazim (CBZ)-sensitive or -resistant
isolate was much suppressed after being treated with strain Pl7, maintaining postharvest quality. The ability of strain Pl7 to swiftly colonize and thrive in apple fruit wounds was demonstrated by a re-isolation assay. Additional transcriptome studies of untreated and treated apple fruit with strain Pl7 revealed that strain Pl7 mostly changed the expression of genes functioning in plant secondary metabolite biosynthesis and plant-pathogen interaction. In light of these outcomes, the underlying antagonistic mechanism was investigated, and
strain Pl7 was identified as a promsing microbial biocontrol agent against apple postharvest decay.
Most Trichoderma species are beneficial fungi that promote plant growth and resistance, while Fusarium genera cause several crop damages. During the plant-fungi interaction there is a competition for ...sugars in both lifestyles. Here we analyzed the plant growth promotion and biocontrol activity of
T. asperellum
against
F. verticillioides
and the effect of both fungi on the expression of the maize diffusional sugar transporters, the SWEETs. The biocontrol activity was done in two ways, the first was by observing the growth capacity of both fungus in a dual culture. The second one by analyzing the infection symptoms, the chlorophyl content and the transcript levels of defense genes determined by qPCR in plants with different developmental stages primed with
T. asperellum
conidia and challenged with
F. verticillioides
. In a dual culture,
T. asperellum
showed antagonist activity against
F. verticillioides
. In the primed plants a delay in the infection disease was observed, they sustained chlorophyll content even after the infection, and displayed upregulated defense-related genes. Additionally, the
T. asperellum
primed plants had longer stems than the nonprimed plants. SWEETs transcript levels were analyzed by qPCR in plants primed with either fungus. Both fungi affect the transcript levels of several maize sugar transporters differently.
T. asperellum
increases the expression of six SWEETs on leaves and two at the roots and causes a higher exudation of sucrose, glucose, and fructose at the roots. On the contrary,
F. verticillioides
reduces the expression of the SWEETs on the leaves, and more severely when a more aggressive strain is in the plant. Our results suggest that the plant is able to recognize the lifestyle of the fungi and respond accordingly by changing the expression of several genes, including the SWEETs, to establish a new sugar flux.
Recently, the application of endophytes in the alleviation of different types of stresses has received considerable attention, but their role in drought stress alleviation and growth promotion in ...soybean is not well-stated. In this study, twenty bacterial endophytes were isolated from soybean root tissues and screened for plant growth-promoting (PGP) traits, biocontrol potential, and drought stress alleviation. Out of them, 80% showed PGP traits, and 20% showed antagonistic activity against
(ITCC 2389),
(ITCC 1800), and
(ITCC 3467), and only three of them showed drought tolerance up to 15% (-0.3 MPa). Results indicated that drought-tolerant PGP endophytic bacteria enhanced soybean seedling growth under drought stress conditions. Morphological, biochemical, and molecular characterization (16S rRNA) revealed that these three bacterial isolates, AKAD A1-1, AKAD A1-2, and AKAD A1-16, closely resemble
(GenBank accession No. MN079048),
(MW301101), and
sp. (MN079074), respectively. We observed that the soybean seedlings were grown in well-watered and drought-stressed soil showed the adverse effect of drought stress on morphological (stem length, root length, plant fresh and dry weight) as well as on biochemical parameters (a decline of photosynthetic pigments, membrane damage, etc.). However, soybean seedlings inoculated with these endophytes have improved the biomass significantly (
≤ 0.05) under normal as well as in drought stress conditions over control treatments by influencing several biochemical changes. Among these three endophytes, AKAD A1-16 performed better than AKAD A1-2 and AKAD A1-1, which was further validated by the ability to produce the enzyme 1-aminocyclopropane-1-carboxylate (ACC) deaminase in the following order: AKAD A1-16 > AKAD A1-2 > AKAD A1-1. Scanning electron microscopy images also showed a bacterial presence inside the roots of soybean seedlings. These findings supported the application of bacterial root endophytes as a potential tool to mitigate the effect of drought as well as of fungal diseases on the early seedling growth of soybean.
The main objective of this study was the investigation of different environmental growth conditions on the growth of chalk yeasts, Hyphopichia burtonii (HB), Wickerhamomyces anomalus (WA) and ...Saccharomycopsis fibuligera (SF). Through multiple methods, including radial growth, biocontrol assay, growth/no-growth modelling and a bread challenge test, the influence of pH (4.5–6.5), temperature (22–30 °C), propionic acid (0–0.3%) and presence of other spoilage fungi was assessed. This study showed that pH and temperature does not play a major role on the growth of HB, WA and SF. Only WA shows optimal growth at pH 4.5 and 30 °C on MEA. The likeliness of growth is the following: HB >SF >WA, except from WA at pH 4.5/30 °C. Biocontrol activity was observed against Aspergillus niger and Penicillium paneum in the presence of high concentrations of HB at 30 °C. Furthermore, this study showed that HB is most sensitive to propionic acid (PA), followed by SF and WA. The effectiveness of PA was also shown through bread challenge tests. The following order of sensitivity against PA was observed: HB >SF >WA. Breads inoculated with WA had a shorter shelf-life (2–3 days less).
•The influence of pH, temperature and propionic acid on chalk yeast growth was evaluated.•The in-vitro results were validated in sourdough bread through a challenge test.•Wickerhamomyces anomalus showed optimal growth at pH 4.5 and 30 °C.•Hyphopichia burtonii exerted antifungal activity at 30 °C against Aspergillus niger and Penicillium paneum.•Hyphopichia burtonii was most sensitive to propionic acid.
Several microorganisms in the plant root system, especially in the rhizosphere, have their own compositions and functions. Corm rot is the most severe disease of
, leading to more than 50% mortality ...in field production.
In this study, metagenomic sequencing was used to analyze microbial composition and function in the rhizosphere of
for possible microbial antagonists against pathogenic
.
The microbial diversity and composition were different in the
rhizosphere from different habitats. The diversity index (Simpson index) was significantly lower in the
rhizospheric soil from Chongming (Rs_CM) and degenerative
rhizospheric soil from Chongming (RsD_CM) than in others. Linear discriminant analysis effect size results showed that differences among habitats were mainly at the order (Burkholderiales, Micrococcales, and Hypocreales) and genus (
and
) levels. Correlation analysis of the relative lesion area of corm rot showed that
was the most negatively correlated bacterial genus (ρ = -0.7934,
< 0.001), whereas
was the most negatively correlated fungal genus (ρ = -0.7047,
< 0.001). The relative lesion area result showed that
from Qiaocheng had the highest resistance, followed by Xiuzhou and Jiande.
groups with high disease resistance had abundant pathogen resistance genes, such as chitinase and β-1,3-glucanase genes, from rhizosphere microorganisms. Further, 13 bacteria and 19 fungi were isolated from
rhizosphere soils, and antagonistic activity against pathogenic
.
was observed on potato dextrose agar medium.
corm experiments confirmed that
SR38,
sp. SR55,
SR379, and
sp. SR343 displayed biocontrol activity against corm rot disease, with biocontrol efficiency of 20.26%, 31.37%, 39.22%, and 14.38%, respectively.
This study uncovers the differences in the microbial community of rhizosphere soil of
with different corm rot disease resistance and reveals the role of four rhizospheric microorganisms in providing the host
with resistance against corm rot. The obtained biocontrol microorganisms can also be used for application research and field management.
Some Pseudomonas strains function as predominant plant growth-promoting rhizobacteria (PGPR). Within this group, Pseudomonas chlororaphis and Pseudomonas fluorescens are non-pathogenic biocontrol ...agents, and some Pseudomonas aeruginosa and Pseudomonas stutzeri strains are PGPR. P. chlororaphis GP72 is a plant growth-promoting rhizobacterium with a fully sequenced genome. We conducted a genomic analysis comparing GP72 with three other pseudomonad PGPR: P. fluorescens Pf-5, P. aeruginosa M18, and the nitrogen-fixing strain P. stutzeri A1501. Our aim was to identify the similarities and differences among these strains using a comparative genomic approach to clarify the mechanisms of plant growth-promoting activity.
The genome sizes of GP72, Pf-5, M18, and A1501 ranged from 4.6 to 7.1 M, and the number of protein-coding genes varied among the four species. Clusters of Orthologous Groups (COGs) analysis assigned functions to predicted proteins. The COGs distributions were similar among the four species. However, the percentage of genes encoding transposases and their inactivated derivatives (COG L) was 1.33% of the total genes with COGs classifications in A1501, 0.21% in GP72, 0.02% in Pf-5, and 0.11% in M18. A phylogenetic analysis indicated that GP72 and Pf-5 were the most closely related strains, consistent with the genome alignment results. Comparisons of predicted coding sequences (CDSs) between GP72 and Pf-5 revealed 3544 conserved genes. There were fewer conserved genes when GP72 CDSs were compared with those of A1501 and M18. Comparisons among the four Pseudomonas species revealed 603 conserved genes in GP72, illustrating common plant growth-promoting traits shared among these PGPR. Conserved genes were related to catabolism, transport of plant-derived compounds, stress resistance, and rhizosphere colonization. Some strain-specific CDSs were related to different kinds of biocontrol activities or plant growth promotion. The GP72 genome contained the cus operon (related to heavy metal resistance) and a gene cluster involved in type IV pilus biosynthesis, which confers adhesion ability.
Comparative genomic analysis of four representative PGPR revealed some conserved regions, indicating common characteristics (metabolism of plant-derived compounds, heavy metal resistance, and rhizosphere colonization) among these pseudomonad PGPR. Genomic regions specific to each strain provide clues to its lifestyle, ecological adaptation, and physiological role in the rhizosphere.
The gram‐positive bacterium Bacillus velezensis strain DMW1 produces a high level of antimicrobial metabolites that can suppress the growth of phytopathogens. We investigated the mechanism used by ...degQ and the degS/degU two‐component system to regulate the biocontrol characteristics of DMW1. When degQ and degU were deleted, the biofilm formation, cell motility, colonization activities, and antifungal abilities of ΔdegQ and ΔdegU were significantly reduced compared to wild‐type DMW1. The expression levels of biofilm‐related genes (epsA, epsB, epsC, and tasA) and swarming‐related genes (swrA and swrB) were all down‐regulated. We also evaluated the impact on secondary metabolites of these two genes. The degQ and degU genes reduced surfactin and macrolactin production and up‐regulated the production of fengycin, iturin, bacillaene, and difficidin metabolites. The reverse transcription‐quantitative PCR results were consistent with these observations. Electrophoretic mobility shift assay and microscale thermophoresis revealed that DegU can bind to the promoter regions of these six antimicrobial metabolite genes and regulate their synthesis. In conclusion, we provided systematic evidence to demonstrate that the degQ and degU genes are important regulators of multicellular behaviour and antimicrobial metabolic processes in B. velezensis DMW1 and suggested novel amenable strains to be used for the industrial production of antimicrobial metabolites.
degQ and degU are important for the biocontrol activity of Bacillus velezensis DMW1, and DegU can regulate the production of secondary metabolites by targeting their promoter regions.
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