Carvacrol, a plant-derived volatile small molecule, is effective against various agents that can cause damage to humans, the food processing industry, and plants, and is considered a safe substance ...for human consumption. In this short communication, previous studies on the effectiveness of carvacrol against various agents, particularly plant pathogens and their associated mechanisms are described. In our study, carvacrol was found to be effective on media against several soilborne pathogens and in planta against three foliar pathogens (
,
, and
) of important vegetable crops in south Florida of the United States. Current research findings indicated that the effectiveness of carvacrol against various plant pathogens tested was associated with its direct bactericidal/fungicidal effect, which was affected greatly by its volatility. Development of new formulations to overcome the volatility and to prolong the effectiveness of carvacrol was also presented. Our studies on carvacrol suggested that, with advanced development of new formulations, carvacrol could be used as a promising tool in the integrated pest management for bacterial, fungal, and viral pathogens of important vegetable crops in Florida, the USA, and the world.
Introducing specific microorganisms into the soil ecological system is an important strategy for improving nutrient use efficiency.Two pot experiments were conducted in the greenhouse from December ...3, 2012 to January 25, 2013（Experiment 1） and March 11 to April 23, 2013（Experiment 2） to evaluate the effect of nitrogen（N） source and inoculation with plant growth-promoting rhizobacteria（PGPR） on plant growth and N and phosphorus（P） uptake in tomato（Lycopersicon esculentum Mill.） grown on calcareous soils from South Florida, USA.Treatments included urea, controlled release urea（a controlled release fertilizer, CRF） each at low and high N rates and with or without inoculation of PGPR.A mixture of PGPR strains Bacillus amyloliquefaciens IN937 a and Bacillus pumilus T4 was applied to the soil during growing periods of tomato.Treatments with PGPR inoculation increased plant height compared to treatments without PGPR in both experiments.Inoculation with PGPR increased shoot dry weight and shoot N uptake for the same N rate and N source.In both experiments, only at high N rate, CRF and urea treatments with PGPR had significantly（P 〈 0.05）greater shoot biomass than those without PGPR.Only at high N rate, CRF treatment with PGPR significantly increased shoot N uptake by 39.0% and 10.3% compared to that without PGPR in Experiments 1 and 2, respectively.Meanwhile, presence of PGPR in the soil increased shoot P uptake for all treatments in Experiment 1 and for most treatments in Experiment 2.In Experiment 1, only at low N rate, CRF treatment with PGPR significantly increased shoot P uptake compared with that without PGPR.In Experiment2, a significant increase in shoot P uptake by inoculation of PGPR was only observed in CRF treatment at high N rate.Results from this study indicate that inoculation with PGPR may increase plant growth and N and P uptake by tomato grown on calcareous soils.However, the effect of PGPR varied and was influenced by many factors such as N source, N rate, and soil fertility.Further investigations are warranted to confirm the effect of PGPR under different soil conditions.
Fluopyram, a SDH inhibitor fungicide, is widely used in agriculture to control fungi and nematodes. However, fluopyram has been proved toxic that caused damage to organs through oxidative stress. The ...development of natural extracts that can reduce oxidative damage is a promising method. Lentinan is isolated from Lentinus edodes and has been verified its antioxidant activity. In this study, Caenorhabditis elegans was used to evaluate the protective effects of lentinan against fluopyram-induced toxicity and the possible mechanisms. Results showed that lentinan pretreatment notably increased the survival rate of N2 nematodes by 15.0 % and extended the lifespan by 91.5 %, compared with the fluopyram treatment. Lentinan pretreatment reverted the inhibition of the locomotion and reproduction of C. elegans under the fluopyram stress. In addition, lentinan pretreatment significantly decreased the contents of ROS and MDA in N2 nematodes. Moreover, pretreated with lentinan significantly recovered the decreased activities of CAT, SOD, GST and SDH induced by fluopyram. Lentinan pretreatment enhanced the mRNA levels of daf-16 and skn-1 and their downstream genes in the nematodes compared with the fluopyram group. In daf-16 and skn-1 mutants, the lifespan, ROS and related genes expression were not significantly changed in lentinan pretreatment. Pretreated with lentinan significantly enhanced the fluorescence intensity of SOD-3::GFP and GST-4::GFP, and promoted the nuclear translocation of DAF-16 and SKN-1 under the fluopyram stress. In summary, these findings indicated that lentinan protected C. elegans from fluopyram-induced toxicity via DAF-16 and SKN-1.
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•First report of lentinan protected C. elegans from fluopyram-induced toxicity.•The protective effect of lentinan on oxidative stress induced by fluopyram was determined.•DAF-16 and SKN-1 pathways were involved in the protection of C. elegans by lentinan.
Abstract
The fungus Magnaporthe oryzae causes devastating diseases of crops, including rice and wheat, and in various grasses. Strains from ryegrasses have highly unstable chromosome ends that ...undergo frequent rearrangements, and this has been associated with the presence of retrotransposons (Magnaporthe oryzae Telomeric Retrotransposons—MoTeRs) inserted in the telomeres. The objective of the present study was to determine the mechanisms by which MoTeRs promote telomere instability. Targeted cloning, mapping, and sequencing of parental and novel telomeric restriction fragments (TRFs), along with MinION sequencing of genomic DNA allowed us to document the precise molecular alterations underlying 109 newly-formed TRFs. These included truncations of subterminal rDNA sequences; acquisition of MoTeR insertions by ‘plain’ telomeres; insertion of the MAGGY retrotransposons into MoTeR arrays; MoTeR-independent expansion and contraction of subtelomeric tandem repeats; and a variety of rearrangements initiated through breaks in interstitial telomere tracts that are generated during MoTeR integration. Overall, we estimate that alterations occurred in approximately sixty percent of chromosomes (one in three telomeres) analyzed. Most importantly, we describe an entirely new mechanism by which transposons can promote genomic alterations at exceptionally high frequencies, and in a manner that can promote genome evolution while minimizing collateral damage to overall chromosome architecture and function.
Bacillus velezensis
strain GB03 is a Gram-positive rhizosphere bacterium known for its ability to promote plant growth and immunity. This review provides a comprehensive overview of the research on ...GB03 from its initial discovery in Australian wheat fields in 1971 to its current applications. Recognized as a model plant growth-promoting rhizobacterium (PGPR), GB03 has exhibited outstanding performance in enhancing the growth and protection of many crop plants including cucumber, pepper, wheat, barley, soybean, and cotton. Notably, GB03 has been reported to elicit plant immune response, referred to as induced systemic resistance (ISR), against above-ground pathogens and insect pests. Moreover, a pivotal finding in GB03 was the first-ever identification of its bacterial volatile compounds, which are known to boost plant growth and activate ISR. Research conducted over the past five decades has clearly demonstrated the potential of GB03 as an eco-friendly substitute for conventional pesticides and fertilizers. Validating its safety, the U.S. Environmental Protection Agency endorsed GB03 for commercial use as Kodiak
®
in 1998. Subsequently, other compounds, such as BioYield™, were released as a biological control agent against soil-borne pathogens and as a biofertilizer, utilizing a durable spore formulation. More recently, GB03 has been utilized as a keystone modulator for engineering the rhizosphere microbiome and for eliciting microbe-induced plant volatiles. These extensive studies on GB03 underscore its significant role in sustainable agriculture, positioning it as a safe and environmentally-friendly solution for crop protection.
Huanglongbing (HLB) is one of the most destructive diseases of citrus worldwide. The three known causal agents of HLB are species of α-proteobacteria: 'Candidatus Liberibacter asiaticus', 'Ca. L. ...africanus', and 'Ca. L. americanus'. Previous studies have found distinct variations in temperature sensitivity and tolerance among these species. Here, we describe the use of controlled heat treatments to cure HLB caused by 'Ca. L. asiaticus', the most prevalent and heat-tolerant species. Using temperature-controlled growth chambers, we evaluated the time duration and temperature required to suppress or eliminate the 'Ca. L. asiaticus' bacterium in citrus, using various temperature treatments for time periods ranging from 2 days to 4 months. Results of quantitative polymerase chain reaction (qPCR) after treatment illustrate significant decreases in the 'Ca. L. asiaticus' bacterial titer, combined with healthy vigorous growth by all surviving trees. Repeated qPCR testing confirmed that previously infected, heat-treated plants showed no detectable levels of 'Ca. L. asiaticus', while untreated control plants remained highly infected. Continuous thermal exposure to 40 to 42°C for a minimum of 48 h was sufficient to significantly reduce titer or eliminate 'Ca. L. asiaticus' bacteria entirely in HLB-affected citrus seedlings. This method may be useful for the control of 'Ca. Liberibacter'-infected plants in nursery and greenhouse settings.
Bacterial spot of tomato continues to pose a significant problem to tomato production worldwide. In Florida, bacterial spot of tomato caused by Xanthomonas perforans is one of the most important ...diseases responsible for tomato yield loss. This disease is difficult to control, and new strategies are continually being investigated to combat the devastating effect of this disease. Recent efforts focusing on essential oils based on small molecules have spurred interests in the utilization of this class of chemicals for disease management. In this study, we evaluated the efficacy of eugenol for the management of bacterial spot of tomato caused by X. perforans. In the greenhouse experiments, eugenol applied as a foliar spray significantly (p < 0.5) reduced bacterial spot disease compared to the untreated control. In the field experiments, the area under the disease progress curve (AUDPC) was significantly (p < 0.5) lower in the plots treated with eugenol or eugenol combined with the surfactant Cohere than in the untreated control plots, and it was comparable to the copper-based treatments. To provide additional insights into the possible pathways of eugenol activities, we applied a liquid chromatography mass spectrometry (LC-MS)-based metabolomic study using a thermo Q-Exactive orbitrap mass spectrometer with Dionex ultra high-performance liquid chromatography (UHPLC) on X. perforans strain 91−118 treated with eugenol. Our results showed that eugenol affected metabolite production in multiple pathways critical to bacterial survival. For example, treatment of cells with eugenol resulted in the downregulation of the glutathione metabolism pathway and associated metabolites, except for 5-oxoproline, which accumulation is known to be toxic to living cells. While the peaks corresponding to the putatively identified sarmentosin showed the most significant impact and reduced in response to eugenol treatment, branched-chain amino acids, such as L-isoleucine, increased in production, suggesting that eugenol may not negatively affect the protein biosynthesis pathways. The results from our study demonstrated the efficacy of eugenol in the management of bacterial spot of tomato under greenhouse and field conditions and identified multiple pathways that are targeted.
A natural extract from Paecilomyces variotii (P. variotii extract, PVE), an endophytic fungus, has been used widely to improve agricultural crop performance and control multiple plant pathogens. Most ...recent studies focused on its application as a plant growth promoter, while relatively few studies have been reported on the antioxidant potential in vivo and the underlying mechanism. The present study was designed to determine the antioxidant activities of PVE and its mechanisms using Caenorhabditis elegans. Results showed that, compared to the solvent control, PVE at 1.0, 10 and 100 ng/mL significantly extended the lifespan of C. elegans by 36.60%, 59.80% and 53.30%, respectively. PVE at 10 ng/mL consistently promoted nematodes growth, but all treatments did not influence nematode fecundity, locomotion behavior, and pharyngeal pumping. Furthermore, PVE at the three tested concentrations significantly reduced accumulation of reactive oxygen species (ROS), lipofuscin, lipid and malondialdehyde (MDA) content, meanwhile significantly promoted activities of superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST) in the nematodes. Compared with the solvent control, PVE up-regulated gene expression of skn-1, mev-1, sod-3, and daf-2, but significantly down-regulated the expression of nhr-49 and daf-16. Further evidence revealed that PVE at the three concentrations significantly promoted nuclear localization of SKN-1, but not affected that of DAF-16, indicating the complex roles of DAF-16 and SKN-1 in stress resistance and longevity regulation. Overall, our results demonstrated that SKN-1 played a critical role in increasing lifespan of C. elegans and protecting the nematodes from oxidative stress, independent of DAF-16.
Fluopimomide is a new pesticide that is widely applied in agriculture; however, the effects and molecular mechanisms of fluopimomide in inhibiting nematode reproduction remain unknown. In this study, ...the effects of fluopimomide on the development and infection of Meloidogyne incognita and the reproductive toxicity in Caenorhabditis elegans were evaluated. Results showed that, in comparison to inoculated control, fluopimomide at 0.33, 0.67, and 1.0 mg/kg soil significantly (p < 0.05) delayed M. incognita development and decreased the reproduction in pot experiments. Fluopimomide notably reduced the galls index with a control effect of 78.6%, 67.9%, and 50.0%, respectively. In addition, a dose–response relationship existed between the brood size and germ cell number of C. elegans and fluopimomide concentrations. Compared with the control group, fluopimomide at 1.0 and 5.0 mg/L notably (p < 0.001) increased the number of cell corpses per gonad in the N2 strain of C. elegans by 8.8- and 14.4-fold, respectively. The number of cell corpses per gonad was similar between the fluopimomide treated worms and the control group in mutants of ced-3, ced-4, and ced-9. Further evidence revealed fluopimomide significantly enhanced the expression of cep-1, egl-1, and clk-2, while no obvious effects were observed in their mutants. Taken together, these results indicated that fluopimomide inflicted DNA damage and induced the core apoptosis pathway caused by germ-cell apoptosis, leading to the reduction of the brood size of C. elegans.
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