Plant growth-promoting rhizobacteria (PGPR) applications have emerged as an ideal substitute for synthetic chemicals by their ability to improve plant nutrition and resistance against pathogens. In ...this study, we isolated fourteen root endophytes from healthy wheat roots cultivated in Tunisia. The isolates were identified based from their 16S rRNA gene sequences. They belonged to Bacillota and Pseudomonadota taxa. Fourteen strains were tested for their growth-promoting and defense-eliciting potentials on durum wheat under greenhouse conditions, and for their in vitro biocontrol power against Fusarium culmorum, an ascomycete responsible for seedling blight, foot and root rot, and head blight diseases of wheat. We found that all the strains improved shoot and/or root biomass accumulation, with Bacillus mojavensis, Paenibacillus peoriae and Variovorax paradoxus showing the strongest promoting effects. These physiological effects were correlated with the plant growth-promoting traits of the bacterial endophytes, which produced indole-related compounds, ammonia, and hydrogen cyanide (HCN), and solubilized phosphate and zinc. Likewise, plant defense accumulations were modulated lastingly and systematically in roots and leaves by all the strains. Testing in vitro antagonism against F. culmorum revealed an inhibition activity exceeding 40% for five strains: Bacillus cereus, Paenibacillus peoriae, Paenibacillus polymyxa, Pantoae agglomerans, and Pseudomonas aeruginosa. These strains exhibited significant inhibitory effects on F. culmorum mycelia growth, sporulation, and/or macroconidia germination. P. peoriae performed best, with total inhibition of sporulation and macroconidia germination. These finding highlight the effectiveness of root bacterial endophytes in promoting plant growth and resistance, and in controlling phytopathogens such as F. culmorum. This is the first report identifying 14 bacterial candidates as potential agents for the control of F. culmorum, of which Paenibacillus peoriae and/or its intracellular metabolites have potential for development as biopesticides.
The wild cochineal
, Dactylopius opuntiae
(Cockerell), has become the main pest of the prickly pear (
Opuntia ficus-indica
(L.) Miller cactus crop in most of the Mediterranean countries, including ...Morocco since 2014. The use of
D. opuntiae
-resistant cactus ecotypes seems to be one of the most practical management option for the control of this pest. The objectives of this study were to identify the resistant genotypes and to determine the mechanism of resistance in 10
D. opuntiae
-resistant cactus genotypes. From
O. ficus-indica
cochineal resistance screening experiments conducted in the laboratory and in mesh cages, 10 cactus genotypes that had fewer nymphs attached with no further developmental changes in the insect were identified. Studies on resistance mechanism showed that resistant genotypes of
O. ficus-indica
had significantly fewer
D. opuntiae
nymphs compared with susceptible genotypes. Genotypes 311 and 322 were the least preferred by
D. opuntiae
with 24.66 and 30 nymphs found after 72 h of infestation. All resistant genotypes have higher levels of dead nymphs compared with the susceptible control. The difference in the mean number of dead nymphs among the different genotypes tested and the control was highly significant. All nymphs produced on resistant genotypes died at first instar stage, indicating that these genotypes possess antibiosis as a mechanism of resistance. Genotype 295 had the highest number of dead nymphs, indicating a strong effect of antibiosis to
D. opuntiae.
Our study showed that both categories (antibiosis, antixenosis) play a role in resistance of the Moroccan cactus ecotypes.
The effect of extracts of the brown algae
Cystoseira myriophylloides
,
Laminaria digitata
, and
Fucus spiralis
against the tomato pathogens
Verticillium dahliae
and
Agrobacterium tumefaciens
was ...evaluated in vitro and in the greenhouse. A significant inhibition of growth was observed only with methanolic seaweed extracts (MSE). Disease resistance was assessed in the greenhouse against
Verticillium
wilt using spray application of aqueous seaweed extracts (ASE) on the whole plant or using seed imbibition. Both methods significantly reduced disease severity whatever the algal species, though protection observed after seed treatments was higher than that observed after spray treatment. Spray application of ASE from
C
.
myriophylloides
and
F
.
spiralis
also resulted in significant reduction of Crown gall disease caused by the bacterial pathogen
A
.
tumefaciens.
ASE-treated plants had significantly higher levels of activity of defense enzymes polyphenol oxidase and peroxidase compared to the control. ASE did not inhibit mycelium growth of
V
.
dahliae
or development of
A
.
tumefaciens
in vitro; it is therefore suggested that induced resistance is probably the main mechanism of protection afforded by ASE.
The purpose of this study is to evaluate and compare the antioxidant and antibacterial activities of essential oil isolated from Tetraclinis articulata (Vahl) leaves, Masters originating in Morocco ...(Benslimane Region, Atlantic-influenced plain). The analysis of the major compounds of essential oil was performed by gas chromatography and mass spectrometry, and this oil is dominated by bornyl acetate (35.05%), camphor (11.17%), and α-pinene (10.84%). The antioxidant properties were evaluated by the test of the radical trap 2,2-diphényl-1-picrylhydrazyl (DPPH), and the antimicrobial activity of T. articulata essential oil was tested against clinical isolates of Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli which have been inhibited from the 25 μg/mL.
Pepino mosaic virus (PepMV) is a highly infectious potexvirus, which has presently become a major pathogen for tomato crops worldwide. Since there is no effective method control for PepMV, strict ...preventive hygienic measures and cross‐protection have been established. However, the use of mild isolates to protect against aggressive isolates provides opportunities for interaction with other microorganisms, which under certain conditions may worsen disease symptoms. Thus, alternative control methods are needed. In this study we aimed at the development of chemical control against PepMV based on the use of heterocyclic compounds including symmetrical 2,5‐disubstituted 1,3,4‐oxadiazoles, symmetrical 2,5‐disubstituted 1,3,4‐thiadiazole and dihydrotetrazine derivatives. Results showed that spray application of three 1,3,4‐oxadiazole derivatives (OH‐Oxa, CH3‐Oxa, NO2‐Oxa) and of the derivative of 1,3,4‐thiadiazole (OH‐Thia) resulted in reducing the main symptoms of PepMV in tomato leaves, conversely to the dihydrotetrazine carboxylic acid. Double‐antibody sandwich enzyme‐linked immunosorbent assay (DAS‐ELISA) revealed that PepMV was not detected from tomato plants pre‐treated with the derivatives conferring elevated protection. Moreover, the protective ability of OH‐Oxa, CH3‐Oxa, NO2‐Oxa and OH‐Thia was closely related to the enhancement of the activity of antioxidant enzymes upon infection with PepMV.
Among the abiotic stresses, drought is the first environmental stress responsible for a decrease in agricultural production worldwide; it affects plants in various ways, including slowing down plant ...growth and disrupting its general physiology. Arbuscular mycorrhizal symbiosis and plant growth-promoting rhizobacteria (PGPR) are considered to be the bioameliorators of the plant’s resistance to water stress. The present study investigated the effects of inoculation with arbuscular mycorrhizal fungi (AMF) and PGPR on the water status and antioxidant enzyme activities of date palm seedlings grown under water stress conditions. The parameters related to the plant’s water status were significantly (p<0.05) higher in the plants treated with mycorrhizae and mycorrhizae + bacteria compared with their respective controls, especially under water stress conditions. The maximum proline content was obtained in plants inoculated with the AMF species and PGPR (combined) under severe water stress conditions reaching a value of 2.588 ± 0.034 in 25% field capacity, compared with 0.978 ± 0.024 for the control. In addition, the inoculated seedlings showed notably lower activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), and glutathione S-transferase (GST) in response to severe water stress compared with nonmycorrhizal seedling. Overall, the arbuscular mycorrhizal symbiosis and PGPR bacteria inoculation could be promising methods to enhance date palm resistance against oxidative stress.
Soilborne diseases are an increasing threat to agriculture and natural ecosystems. Olive root and crown rot (ORCR) caused by pathogenic oomycete species has recently been reported in several ...olive-growing countries as an emerging phytopathological problem causing leaf yellowing, defoliation, twig dieback, and the development of wilting followed by decline of olive trees. Within the oomycetes, several
Phytophthora
and
Pythium
species have been reported to cause root and crown rot of cultivated and wild olive trees. Studies have shown that the disease is particularly severe in young olive groves located on poorly drained, occasionally waterlogged clay soils. Modernization of olive orchards induced by the introduction of irrigation, planting on more favourable and heavier soils, and intensification may increase the risk to cultivated olive trees. In addition, the potential for the spread of these oomycetes, as well as changes in precipitation patterns with more frequent heavy rains, would facilitate the development of infections in wild olive forests and olive groves. Therefore, this review summarizes the latest findings and advances regarding the causative agents of ORCR, detection and diagnosis tools, symptoms, disease cycle, epidemiology, and potential management strategies.
In the realm of sustainable agriculture, biocontrol is gaining considerable attention for its focus on the development of safe, biodegradable, and environmentally friendly alternatives to traditional ...biocides. This study explored the potential use of essential oils as alternative biocontrol products for managing Verticillium dahliae, the causal agent of Verticillium wilt in olive trees. Essential oils (EOs) were obtained through hydrodistillation from six Moroccan aromatic and medicinal plants (Ammodaucus leucotrichus, Mentha spicata, Origanum majorana, Rosmarinus officinalis, Salvia officinalis, and Thymus satureioides). These EOs were then subjected to chemical analysis by gas chromatography-mass spectrometry (GC-MS) and evaluated in vitro for their antifungal properties against V. dahliae. The bioassays revealed that all tested EOs reduced mycelial growth of the studied strain, and tended to have dose-dependent effects. Compared with the various essential oils evaluated in this study, A. leucotrichus essential oils showed the most pronounced antifungal efficacy at low and moderate concentrations. These EOs stand out for their high content of two monoterpenes, perillia aldehyde (84.19 %) and limonene (14.15 %), which were not found in the other essential oils examined. Therefore, our results open up new possibilities for exploiting these plants and their chemical constituents to develop a natural biofungicide as a component of integrated management strategies for Verticillium wilt of olive and other crops.
•Two plant growth promoting rhizobacteria isolated from the rhizosphere of P. domestica were identified as Pseudomonas stutzeri and Bacillus toyonensis.•They promoted tomato growth under normal and ...salt stress conditions.•They protected tomato plant from Verticillium wilt disease.•They enhanced acclimatation of Vitis vinifera and peach root stock GF305 from in vitro to the greenhouse.
Plants interact with a great variety of microorganisms that inhabit the rhizosphere playing critical roles in several aspects of plant growth and protection against abiotic and biotic diseases. In this study, we performed a screening of bacteria associated with the rhizosphere of Prunus domestica trees to identify bacterial strains with plant growth-promoting activity. Ten strains isolated from the rhizosphere of P. domestica showed multiple in vitro plant growth promoting rhizobacteria (PGPR) activity such as the production of indole acetic acid, hydrogen cyanide, ammonia, solubilization of phosphates and antifungal activity against Verticillium dalhiae and Fusarium oxysporum f.sp. melonis. In planta, they significantly increased the growth (stem length, number of leaflets, leaf area and root weight) and biochemical (nitrate reductase activity, proline and chlorophyll content) parameters of tomato, as well as the rate of seed germination. Two selected strains (Pr7 and Pr8) with higher antagonistic activity against V. dalhiae and F. oxysporum f.sp. melonis protected tomato plants against Verticillium wilt and salt stress. In addition, they enhanced acclimatization of Vitis vinifera cv. Pinot noir and the peach root stock GF305 from in vitro to the greenhouse. 16S rRNA sequencing identified strains Pr7 and Pr8 as Pseudomonas stutzeri and Bacillus toyonensis, respectively. Since these two PGPR inoculants exhibited multiple traits beneficial to the examined host plants, they may be applied in the development of safe, and effective seed treatments as an alternative to chemical fungicides and fertilization but also for successful acclimatization of micropropagated plants.
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