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1.
Sci Rep ; 10(1): 15536, 2020 09 23.
Artigo em Inglês | MEDLINE | ID: mdl-32968101

RESUMO

A total of 120 rhizobacteria were isolated from seven different tea estates of Darjeeling, West Bengal, India. Based on a functional screening of in vitro plant growth-promoting (PGP) activities, thirty potential rhizobacterial isolates were selected for in-planta evaluation of PGP activities in rice and maize crops. All the thirty rhizobacterial isolates were identified using partial 16S rRNA gene sequencing. Out of thirty rhizobacteria, sixteen (53.3%) isolates belong to genus Bacillus, five (16.6%) represent genus Staphylococcus, three (10%) represent genus Ochrobactrum, and one (3.3%) isolate each belongs to genera Pseudomonas, Lysinibacillus, Micrococcus, Leifsonia, Exiguobacterium, and Arthrobacter. Treatment of rice and maize seedlings with these thirty rhizobacterial isolates resulted in growth promotion. Besides, rhizobacterial treatment in rice triggered enzymatic [ascorbate peroxidase (APX), catalase (CAT), chitinase, and phenylalanine ammonia-lyase (PAL)], and non-enzymatic [proline and polyphenolics] antioxidative defense reactions indicating their possible role in the reduction of reactive oxygen species (ROS) burden and thereby priming of plants towards stress mitigation. To understand such a possibility, we tested the effect of rhizobacterial consortia on biotic stress tolerance of rice against necrotrophic fungi, Rhizoctonia solani AG1-IA. Our results indicated that the pretreatment with rhizobacterial consortia increased resistance of the rice plants towards the common foliar pathogen like R. solani AG1-IA. This study supports the idea of the application of plant growth-promoting rhizobacterial consortia in sustainable crop practice through the management of biotic stress under field conditions.


Assuntos
Antioxidantes/metabolismo , Camellia sinensis/microbiologia , Raízes de Plantas/microbiologia , Basidiomycota/genética , Basidiomycota/fisiologia , Camellia sinensis/crescimento & desenvolvimento , Camellia sinensis/imunologia , Camellia sinensis/metabolismo , Clorofila/metabolismo , Índia , Oryza/crescimento & desenvolvimento , Oryza/microbiologia , Prolina/metabolismo , RNA Ribossômico 16S/genética , Rhizoctonia/genética , Rhizoctonia/fisiologia , Rizosfera , Plântula/crescimento & desenvolvimento , Plântula/imunologia , Plântula/metabolismo , Plântula/microbiologia , Microbiologia do Solo , Zea mays/crescimento & desenvolvimento , Zea mays/microbiologia
2.
Sci Rep ; 10(1): 15621, 2020 09 24.
Artigo em Inglês | MEDLINE | ID: mdl-32973199

RESUMO

Pseudomonas aeruginosa developed its biocontrol agent property through the production of antifungal derivatives, with the phenazine among them. In this study, the applications of crude phenazine synthesized by Pseudomonas aeruginosa UPMP3 and hexaconazole were comparatively evaluated for their effectiveness to suppress basal stem rot infection in artificially G. boninense-challenged oil palm seedlings. A glasshouse experiment under the randomized completely block design was set with the following treatments: non-inoculated seedlings, G. boninense inoculated seedlings, G. boninense inoculated seedlings with 1 mg/ml phenazine application, G. boninense inoculated seedlings with 2 mg/ml phenazine application and G. boninense inoculated seedlings with 0.048 mg/ml hexaconazole application. Seedlings were screened for disease parameters and plant vigour traits (plant height, plant fresh weight, root fresh, and dry weight, stem diameter, and total chlorophyll) at 1-to-4 month post-inoculation (mpi). The application of 2 mg/ml phenazine significantly reduced disease severity (DS) at 44% in comparison to fungicide application (DS = 67%). Plant vigour improved from 1 to 4 mpi and the rate of disease reduction in seedlings with phenazine application (2 mg/ml) was twofold greater than hexaconazole. At 4, 6 and 8 wpi, an up-regulation of chitinase and ß-1,3 glucanase genes in seedlings treated with phenazine suggests the involvement of induced resistance in G. boninense-oil palm pathosystem.


Assuntos
Arecaceae/crescimento & desenvolvimento , Ganoderma/patogenicidade , Fenazinas/farmacologia , Doenças das Plantas/imunologia , Raízes de Plantas/crescimento & desenvolvimento , Pseudomonas aeruginosa/química , Plântula/crescimento & desenvolvimento , Arecaceae/efeitos dos fármacos , Arecaceae/microbiologia , Doenças das Plantas/microbiologia , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/microbiologia , Plântula/efeitos dos fármacos , Plântula/microbiologia
3.
Am Nat ; 196(4): 472-486, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-32970465

RESUMO

AbstractSpecialized pathogens are thought to maintain plant community diversity; however, most ecological studies treat pathogens as a black box. Here we develop a theoretical model to test how the impact of specialized pathogens changes when plant resistance genes (R-genes) mediate susceptibility. This work synthesizes two major hypotheses: the gene-for-gene model of pathogen resistance and the Janzen-Connell hypothesis of pathogen-mediated coexistence. We examine three scenarios. First, R-genes do not affect seedling survival; in this case, pathogens promote diversity. Second, seedlings are protected from pathogens when their R-gene alleles and susceptibility differ from those of nearby conspecific adults, thereby reducing transmission. If resistance is not costly, pathogens are less able to promote diversity because populations with low R-gene diversity suffer higher mortality, putting those populations at a disadvantage and potentially causing their exclusion. R-gene diversity may also be reduced during population bottlenecks, creating a priority effect. Third, when R-genes affect survival but resistance is costly, populations can avoid extinction by losing resistance alleles, as they cease paying a cost that is unneeded. Thus, the impact pathogens can have on tree diversity depends on the mechanism of plant-pathogen interactions. Future empirical studies should examine which of these scenarios most closely reflects the real world.


Assuntos
Resistência à Doença/genética , Doenças das Plantas/genética , Plantas/genética , Biodiversidade , Desenvolvimento Vegetal , Doenças das Plantas/microbiologia , Plantas/microbiologia , Plântula/genética , Plântula/microbiologia
4.
PLoS One ; 15(8): e0238055, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32845898

RESUMO

Lodgepole pine, a prominent Pinaceae tree species native to western North America, is well-known for its ability to thrive in highly disturbed and degraded areas. One such area is the Sub-Boreal Pine-Spruce xeric-cold (SBPSxc) region in British Columbia, Canada, which is characterized by weakly-developed, parched soils that lack an organic forest floor and essential plant-available nutrients. We hypothesized that plant growth-promoting bacteria could play a significant role in sustaining the growth of lodgepole pine trees in the SBPSxc region. Testing this hypothesis, we evaluated plant growth-promoting abilities of six endophytic bacterial strains previously isolated from lodgepole pine trees growing in this region. These bacterial strains significantly enhanced the length and biomass of their natural host (lodgepole pine) as well as a foreign host (hybrid white spruce) in a 540-day long greenhouse trial. This growth stimulation could be linked to the diverse plant growth-promoting (PGP) abilities detected in these strains using in vitro assays for inorganic/organic phosphate-solubilization, siderophore production IAA production, ACC deaminase activity, lytic enzymes (chitinase, ß-1,3-glucanase, protease, and cellulase) activity, ammonia production and catalase activity. ACC deaminase activity was also detected in vivo for all strains using ethylene-sensitive plants-canola and tomato. Notably, strains belonging to the Burkholderiaceae family (HP-S1r, LP-R1r and LP-R2r) showed the greatest potential in all PGP assays and enhanced pine and spruce seedling length and biomass by up to 1.5-fold and 4-fold, respectively. Therefore, such bacterial strains with multifarious PGP abilities could be crucial for survival and growth of lodgepole pine trees in the SBPSxc region and could potentially be utilized as bioinoculant for Pinaceae trees in highly disturbed and nutrient-poor ecosystems.


Assuntos
Bactérias/isolamento & purificação , Pinaceae/crescimento & desenvolvimento , Biomassa , Fosfatos de Cálcio/química , Fosfatos de Cálcio/metabolismo , Carbono-Carbono Liases/genética , Carbono-Carbono Liases/metabolismo , Ecossistema , Etilenos/metabolismo , Ácidos Indolacéticos/metabolismo , Picea/crescimento & desenvolvimento , Picea/metabolismo , Picea/microbiologia , Pinaceae/metabolismo , Pinaceae/microbiologia , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/metabolismo , Plântula/microbiologia , Plântula/fisiologia , Sideróforos/metabolismo
5.
Plant Physiol Biochem ; 155: 406-415, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32814277

RESUMO

Due to insoluble iron (Fe) sources in soil, limited Fe availability leads to the disruption of the photosynthetic apparatus; this affects the growth and productivity of plants such as quince (Cydonia oblonga) that are very sensitive to low Fe content. Plant growth-promoting rhizobacteria (PGPR) play an important role in the regulation of Fe uptake under its limited availability. Therefore, in this research, two PGPR (Pseudomonas fluorescens and Microccucuce yunnanensis), at two Fe levels [50 µM (Fe-sufficiency) or 5 µM (Fe-deficiency)], were used to investigate the impact of the given bacteria on improving the acquisition of Fe in quince seedlings. Upon Fe-deficiency, the highest shoot and root biomass (7.14 and 6.04 g plant-1 respectively), the greatest chlorophyll concentration (0.89 mg g-1FW), and the largest Fe concentrations in roots and shoots (30% and 48.7%, respectively) were shown in the quince treated with M. yunnanensis. Both PGPR increased the root citric acid and the phenolic compound concentration. Two days after Fe-deficiency and PGPR treatments, a 1.5- fold increase, was observed in the expression of HA7. The highest PAL1 gene expression and the greatest PAL activity (95.76 µmol cinnamic acid g-1FW) were obtained from the M. yunnanensis treatment. The expression of the FRO2 gene was also affected by Fe-deficiency and PGPR treatments, resulting in an increase in the FCR activity and a surge in the Fe concentrations of leaves and roots. It could, therefore, be concluded that the PGPR modulated Fe acquisition in the quince seedlings upon Fe-deficiency by influencing the physico-chemical and molecular responses.


Assuntos
Ferro/metabolismo , Micrococcus/fisiologia , Pseudomonas fluorescens/fisiologia , Rosaceae/crescimento & desenvolvimento , Rosaceae/microbiologia , Raízes de Plantas/microbiologia , Plântula/crescimento & desenvolvimento , Plântula/microbiologia
6.
PLoS One ; 15(8): e0234099, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32810132

RESUMO

Two common ecological assumptions are that host generalist and rare species are poorer competitors relative to host specialist and more abundant counterparts. While these assumptions have received considerable study in both plant and animals, how they apply to ectomycorrhizal fungi remains largely unknown. To investigate how interspecific competition may influence the anomalous host associations of the rare ectomycorrhizal generalist fungus, Suillus subaureus, we conducted a seedling bioassay. Pinus strobus seedlings were inoculated in single- or two-species treatments of three Suillus species: S. subaureus, S. americanus, and S. spraguei. After 4 and 8 months of growth, seedlings were harvested and scored for mycorrhizal colonization as well as dry biomass. At both time points, we found a clear competitive hierarchy among the three ectomycorrhizal fungal species: S. americanus > S. subaureus > S. spraguei, with the competitive inferior, S. spraguei, having significantly delayed colonization relative to S. americanus and S. subaureus. In the single-species treatments, we found no significant differences in the dry biomasses of P. strobus seedlings colonized by each Suillus species, suggesting none was a more effective plant symbiont. Taken together, these results indicate that the rarity and anomalous host associations exhibited by S. subaureus in natural settings are not driven by inherently poor competitive ability or host growth promotion, but that the timing of colonization is a key factor determining the outcome of ectomycorrhizal fungal competitive interactions.


Assuntos
Micorrizas/crescimento & desenvolvimento , Pinus/microbiologia , Simbiose/fisiologia , Basidiomycota/classificação , Basidiomycota/genética , Basidiomycota/crescimento & desenvolvimento , Biomassa , Interações entre Hospedeiro e Microrganismos/fisiologia , Especificidade de Hospedeiro/genética , Especificidade de Hospedeiro/fisiologia , Pinus/crescimento & desenvolvimento , Raízes de Plantas/microbiologia , Plântula/crescimento & desenvolvimento , Plântula/microbiologia
7.
Sheng Wu Gong Cheng Xue Bao ; 36(7): 1356-1364, 2020 Jul 25.
Artigo em Chinês | MEDLINE | ID: mdl-32748593

RESUMO

Salinity is the most important factor for the growth of crops. It is an effective method to alleviate the toxic effect caused by salt stress using saline-alkali-tolerant and growth-promoting bacteria in agriculture. Seven salt-tolerant bacteria were screened from saline-alkali soil, and the abilities of EPS production, alkalinity reduction and IAA production of the selected strains were investigated. A dominant strain DB01 was evaluated. The abilities of EPS production, alkalinity reduction and IAA production of strain DB01 were 0.21 g/g, 8.7% and 8.97 mg/L, respectively. The isolate was identified as Halomonas aquamarina by partial sequencing analysis of its 16S rRNA genes, and had the ability to inhibit the growth of Fusarium oxysporum f. sp., Alternaria solani, Phytophthora sojae and Rhizoctonia cerealis. It also could promote root length and germination rate of wheat seedlings under salt stress. Halomonas aquamarina can provide theoretical basis for the development of soil microbial resources and the application in saline-alkali soil improvement.


Assuntos
Álcalis , Raízes de Plantas , Tolerância ao Sal , Microbiologia do Solo , Álcalis/metabolismo , Bactérias/efeitos dos fármacos , Bactérias/genética , Halomonas/genética , Raízes de Plantas/microbiologia , RNA Ribossômico 16S/genética , Tolerância ao Sal/genética , Plântula/crescimento & desenvolvimento , Plântula/microbiologia , Solo/química , Triticum/microbiologia
8.
Sci Rep ; 10(1): 10908, 2020 07 02.
Artigo em Inglês | MEDLINE | ID: mdl-32616836

RESUMO

Stripe or yellow rust (YR) caused by Puccinia striiformis Westend. f. sp. tritici Erikss. is a persistent biotic-stress threatening global wheat production. To broaden our understanding of the shared genetic basis of YR resistance across multi-site and multi-year evaluations, we performed a large genome-wide association study using 43,706 YR observations on 23,346 wheat lines from the International Maize and Wheat Improvement Center evaluated between 2013 and 2019 at sites in India, Kenya and Mexico, against predominant races prevalent in the countries. We identified 114 repeatable markers tagging 20 quantitative trait loci (QTL) associated with YR on ten chromosomes including 1D, 2A, 2B, 2D, 3A, 4A, 4D, 5A, 5B and 6B, among which four QTL, QYr.cim-2DL.2, QYr.cim-2AS.1, QYr.cim-2BS.2 and QYr.cim-2BS.3 were significant in more than ten datasets. Furthermore, we report YR-associated allelic fingerprints for the largest panel of wheat breeding lines (52,067 lines) till date, creating substantial opportunities for YR favorable allele enrichment using molecular markers. Overall, the markers and fingerprints reported in this study provide excellent insights into the genetic architecture of YR resistance in different geographical regions, time-periods and wheat germplasm and are a huge resource to the global wheat breeding community for accelerating YR resistance breeding efforts.


Assuntos
Genoma de Planta , Doenças das Plantas/genética , Triticum/genética , Alelos , Cromossomos de Plantas/genética , Resistência à Doença/genética , Marcadores Genéticos , Genoma de Planta/genética , Estudo de Associação Genômica Ampla , Quênia , Desequilíbrio de Ligação , México , Melhoramento Vegetal , Doenças das Plantas/microbiologia , Análise de Componente Principal , Locos de Características Quantitativas , Plântula/microbiologia , Triticum/microbiologia
9.
PLoS One ; 15(7): e0235932, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32645087

RESUMO

We tested whether post-fire seedling establishment of common boreal tree and expanding shrub species at treeline and in Arctic tundra is facilitated by co-migration of boreal forest mycorrhizal fungi. Wildfires are anticipated to facilitate biome shifts at the forest-tundra ecotone by improving seedbed conditions for recruiting boreal species; at the same time fire alters the composition and availability of mycorrhizal fungi critical to seedling performance. To determine the role of root-associated fungi (RAF) in post-fire seedling recruitment and future biome shifts, we outplanted four dominant boreal tree and shrub species inoculated with one of three treatments at treeline and in tundra: burned boreal forest, unburned boreal forest, or a control treatment of sterilized inoculum. We compared survivorship, growth, and physiological performance of the seedlings in relation to mycorrhizal inoculum treatment and among host species, characterized the RAF communities based on ITS-rDNA sequencing of individual root tips sampled from surviving seedlings, and tested for correlations between RAF composition and the inoculation treatments, host species, and duration of the experiment. We explored correlations between RAF composition and seedling metrics. Both live and sterile autoclaved inoculation treatments had similar effects on seedling survivorship and growth for all species. RAF composition did not vary by treatment, suggesting that most colonization was due to local fungi. However, seedling traits and growth were correlated with RAF species composition, colonization, and the relative abundance of specific RAF taxa. Picea sp. performance in particular showed strong co-variation with RAF metrics. Our results suggest that mycorrhizal co-migration is not a primary limiting factor to boreal seedling recruitment because the experimental provision of inoculum did not affect seedling recruitment; yet, RAF did influence seedling performance, particularly resident RAF at treeline and in tundra, suggesting that mycorrhizal fungi are important to vegetation processes at the treeline-tundra ecotone.


Assuntos
Micorrizas/fisiologia , Árvores/microbiologia , Incêndios Florestais , Basidiomycota/fisiologia , Picea/crescimento & desenvolvimento , Picea/microbiologia , Raízes de Plantas/microbiologia , Populus/crescimento & desenvolvimento , Populus/microbiologia , Plântula/crescimento & desenvolvimento , Plântula/microbiologia , Especificidade da Espécie , Taiga , Árvores/crescimento & desenvolvimento , Tundra
10.
PLoS One ; 15(6): e0229807, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32502167

RESUMO

The success of tree recruitment in Mediterranean holm oak (Quercus ilex) forests is threatened by the increasing intensity, duration and frequency of drought periods. Seedling germination and growth are modulated by complex interactions between abiotic (microhabitat conditions) and biotic factors (mycorrhiza association) that may mitigate the impacts of climate change on tree recruitment. To better understand and anticipate these effects, we conducted a germination experiment in a long-term precipitation reduction (PR) field experiment where we monitored seedling establishment and survival, micro-habitat conditions and ectomycorrhizal (ECM) colonization by different mycelia exploration types during the first year of seedling growth. We hypothesized that (i) the PR treatment decreases seedling survival relative to the control with ambient conditions, (ii) microhabitat conditions of water and light availability are better predictors of seedling survival than the PR treatment, (iii) the PR treatment will favour the development of ECM exploration types with drought-resistance traits such as differentiated rhizomorphs. Contrary to our first hypothesis, seedling survival was lower in control plots with overall higher soil moisture. Micro-habitat light and soil moisture conditions were better predictors of seedling survival and growth than the plot-level PR treatment, confirming our second hypothesis. Furthermore, in line with our third hypothesis, we found that ECM with longer extramatrical mycelia were more abundant in the PR treatment plots and were positively correlated to survival, which suggests a potential role of this ECM exploration type in seedling survival and recruitment. Although summer drought was the main cause of seedling mortality, our study indicates that drier conditions in spring can increase seedling survival, presumably through a synergistic effect of drought adapted ECM species and less favourable conditions for root pathogens.


Assuntos
Secas , Ecossistema , Micorrizas/fisiologia , Quercus/crescimento & desenvolvimento , Quercus/microbiologia , Plântula/microbiologia , Plântula/fisiologia , Germinação , Análise de Sobrevida
11.
Appl Environ Microbiol ; 86(16)2020 08 03.
Artigo em Inglês | MEDLINE | ID: mdl-32561579

RESUMO

Streptomyces bacteria are ubiquitous in soils and are well known for producing secondary metabolites, including antimicrobials. Increasingly, they are being isolated from plant roots, and several studies have shown they are specifically recruited to the rhizosphere and the endosphere of the model plant Arabidopsis thaliana Here, we test the hypothesis that Streptomyces bacteria have a beneficial effect on A. thaliana growth and could potentially be used as plant probiotics. To do this, we selectively isolated streptomycetes from surface-washed A. thaliana roots and generated high-quality genome sequences for five strains, which we named L2, M2, M3, N1, and N2. Reinfection of A. thaliana plants with L2, M2, and M3 significantly increased plant biomass individually and in combination, whereas N1 and N2 had a negative effect on plant growth, likely due to their production of polyene natural products which can bind to phytosterols and reduce plant growth. N2 exhibits broad-spectrum antimicrobial activity and makes filipin-like polyenes, including 14-hydroxyisochainin which inhibits the take-all fungus, Gaeumannomyces graminis var. tritici N2 antifungal activity as a whole was upregulated ∼2-fold in response to indole-3-acetic acid (IAA), suggesting a possible role during competition in the rhizosphere. Furthermore, coating wheat seeds with N2 spores protected wheat seedlings against take-all disease. We conclude that at least some soil-dwelling streptomycetes confer growth-promoting benefits on A. thaliana, while others might be exploited to protect crops against disease.IMPORTANCE We must reduce reliance on agrochemicals, and there is increasing interest in using bacterial strains to promote plant growth and protect against disease. Our study follows up reports that Arabidopsis thaliana specifically recruits Streptomyces bacteria to its roots. We test the hypotheses that they offer benefits to their A. thaliana hosts and that strains isolated from these plants might be used as probiotics. We isolated Streptomyces strains from A. thaliana roots and genome sequenced five phylogenetically distinct strains. Genome mining and bioassays indicated that all five have plant growth-promoting properties, including production of indole-3-acetic acid (IAA), siderophores, and aminocyclopropane-1-carboxylate (ACC) deaminase. Three strains significantly increased A. thaliana growth in vitro and in combination in soil. Another produces potent filipin-like antifungals and protected germinating wheat seeds against the fungal pathogen Gaeumannomyces graminis var. tritici (wheat take-all fungus). We conclude that introducing Streptomyces strains into the root microbiome provides significant benefits to plants.


Assuntos
Arabidopsis/fisiologia , Endófitos/fisiologia , Interações entre Hospedeiro e Microrganismos , Streptomyces/fisiologia , Triticum/fisiologia , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/microbiologia , Plântula/crescimento & desenvolvimento , Plântula/microbiologia , Microbiologia do Solo , Triticum/crescimento & desenvolvimento , Triticum/microbiologia
12.
Arch Microbiol ; 202(8): 2169-2179, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32519022

RESUMO

Bacillus methylotrophicus has been demonstrated to promote growth of various plants, whereas the promoting effect of B. methylotrophicus on rice growth has been rarely reported. In this study, B. methylotrophicus DD-1, capable of efficiently promoting the growth of rice, was isolated from the root soil of rice plants. The isolate exhibited potassium-solubilizing (1.18 mg/L), Indole-3-acetic acid (IAA) (87.26 mg/L), Gibberellic acid (GA) (25.91 mg/L) and Siderophore production activity (52.32%). As indicated from the result, plant growth parameters (e.g., dry weight, tiller number, root and shoot length) of rice seedlings treated with the isolate DD-1 were more effective than those of the control group in pot and soilless culture experiments. Moreover, the adsorption capacity of rice roots which were soaked in the bacterial suspension of isolate increased with the increase in concentration and absorption time. In sterilized and unsterilized soil, conformation of root colonization activity by bacterial isolate established by its nearer existence to the rice root. Thus, the B. methylotrophicus DD-1 enhances plant growth promotion by multifarious growth promoting and root colonization traits, thereby augmenting potassium level in soil. Henceforth, the potential bacterium could be exploited for the development of biological fertilizer, leading towards sustainable agronomy.


Assuntos
Bacillus/fisiologia , Oryza/microbiologia , Raízes de Plantas/microbiologia , Plântula/microbiologia , Microbiologia do Solo , Bacillus/isolamento & purificação , Giberelinas/metabolismo , Ácidos Indolacéticos/metabolismo , Oryza/crescimento & desenvolvimento , Desenvolvimento Vegetal , Plântula/crescimento & desenvolvimento , Sideróforos/metabolismo
13.
PLoS One ; 15(5): e0233807, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32470009

RESUMO

Benzoxazinoids (BXs) are secondary metabolites with diverse functions, but are primarily involved in protecting plants, mainly from the family Poaceae, against insects and fungal pathogens. Rye is a cereal crop that is highly resistant to biotic stresses. However, its susceptibility to brown rust caused by Puccinia recondita f. sp. secalis (Prs) is still a major problem affecting its commercial production. Additionally, the genetic and metabolic factors related to this disease remain poorly characterized. In this study, we investigated whether and to what extent the brown rust infection and the inoculation procedure affect the contents of specific BXs (HBOA, GDIBOA, DIBOA, GDIMBOA, DIMBOA, and MBOA) and the expression of genes related to BX (ScBx1-5, ScIgl, and Scglu). We revealed that treatments with water and a urediniospore suspension usually downregulate gene expression levels. Moreover, HBOA and DIBOA contents decreased, whereas the contents of the remaining metabolites increased. Specifically, the MBOA content increased more after the mock treatment than after the Prs treatment, whereas the increase in GDIBOA and GDIMBOA levels was usually due to the Prs infection, especially at two of the most critical time-points, 17 and 24 h post-treatment. Therefore, GDIBOA and GDIMBOA are glucosides that are important components of rye defence responses to brown rust. Furthermore, along with MBOA, they protect rye against the stress associated with the inoculation procedure used in this study.


Assuntos
Basidiomycota/fisiologia , Benzoxazinas/metabolismo , Regulação da Expressão Gênica de Plantas , Genes de Plantas , Doenças das Plantas/genética , Doenças das Plantas/microbiologia , Secale/genética , Interações Hospedeiro-Patógeno/genética , Plântula/genética , Plântula/microbiologia , Água
14.
Appl Environ Microbiol ; 86(15)2020 07 20.
Artigo em Inglês | MEDLINE | ID: mdl-32471917

RESUMO

Plant roots shape the rhizosphere community by secreting compounds that recruit diverse bacteria. Colonization of various plant roots by the motile alphaproteobacterium Azospirillum brasilens e causes increased plant growth, root volume, and crop yield. Bacterial chemotaxis in this and other motile soil bacteria is critical for competitive colonization of the root surfaces. The role of chemotaxis in root surface colonization has previously been established by endpoint analyses of bacterial colonization levels detected a few hours to days after inoculation. More recently, microfluidic devices have been used to study plant-microbe interactions, but these devices are size limited. Here, we use a novel slide-in chamber that allows real-time monitoring of plant-microbe interactions using agriculturally relevant seedlings to characterize how bacterial chemotaxis mediates plant root surface colonization during the association of A. brasilens e with Triticum aestivum (wheat) and Medicago sativa (alfalfa) seedlings. We track A. brasilense accumulation in the rhizosphere and on the root surfaces of wheat and alfalfa. A. brasilense motile cells display distinct chemotaxis behaviors in different regions of the roots, including attractant and repellent responses that ultimately drive surface colonization patterns. We also combine these observations with real-time analyses of behaviors of wild-type and mutant strains to link chemotaxis responses to distinct chemicals identified in root exudates to specific chemoreceptors that together explain the chemotactic response of motile cells in different regions of the roots. Furthermore, the bacterial second messenger c-di-GMP modulates these chemotaxis responses. Together, these findings illustrate dynamic bacterial chemotaxis responses to rhizosphere gradients that guide root surface colonization.IMPORTANCE Plant root exudates play critical roles in shaping rhizosphere microbial communities, and the ability of motile bacteria to respond to these gradients mediates competitive colonization of root surfaces. Root exudates are complex chemical mixtures that are spatially and temporally dynamic. Identifying the exact chemical(s) that mediates the recruitment of soil bacteria to specific regions of the roots is thus challenging. Here, we connect patterns of bacterial chemotaxis responses and sensing by chemoreceptors to chemicals found in root exudate gradients and identify key chemical signals that shape root surface colonization in different plants and regions of the roots.


Assuntos
Azospirillum brasilense/fisiologia , Medicago sativa/metabolismo , Raízes de Plantas/metabolismo , Rizosfera , Plântula/metabolismo , Triticum/metabolismo , Quimiotaxia , Medicago sativa/microbiologia , Plântula/microbiologia , Triticum/microbiologia
15.
Nat Commun ; 11(1): 2636, 2020 05 26.
Artigo em Inglês | MEDLINE | ID: mdl-32457288

RESUMO

The mechanisms regulating community composition and local dominance of trees in species-rich forests are poorly resolved, but the importance of interactions with soil microbes is increasingly acknowledged. Here, we show that tree seedlings that interact via root-associated fungal hyphae with soils beneath neighbouring adult trees grow faster and have greater survival than seedlings that are isolated from external fungal mycelia, but these effects are observed for species possessing ectomycorrhizas (ECM) and not arbuscular mycorrhizal (AM) fungi. Moreover, survival of naturally-regenerating AM seedlings over ten years is negatively related to the density of surrounding conspecific plants, while survival of ECM tree seedlings displays positive density dependence over this interval, and AM seedling roots contain greater abundance of pathogenic fungi than roots of ECM seedlings. Our findings show that neighbourhood interactions mediated by beneficial and pathogenic soil fungi regulate plant demography and community structure in hyperdiverse forests.


Assuntos
Micorrizas/fisiologia , Microbiologia do Solo , Árvores/microbiologia , China , Florestas , Fungos/genética , Fungos/patogenicidade , Fungos/fisiologia , Interações entre Hospedeiro e Microrganismos/genética , Interações entre Hospedeiro e Microrganismos/fisiologia , Modelos Biológicos , Biologia Molecular , Micorrizas/genética , Micorrizas/patogenicidade , Plântula/crescimento & desenvolvimento , Plântula/microbiologia , Simbiose , Árvores/crescimento & desenvolvimento
16.
PLoS One ; 15(4): e0230801, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32275719

RESUMO

Downy mildew of opium poppy is the single biggest disease constraint afflicting the Australian poppy industry. Within the pathosystem, the transmission of infections via infested seed is of major concern. Both downy mildew pathogens of poppy; Peronospora meconopsidis and P. somniferi, are known contaminants of commercial seed stocks. Using seed naturally infested with these pathogens, the effect of physio-chemical seed treatments on seedling health and disease transmission were evaluated. Individual seed treatments were tested to determine optimal treatment parameters for each; including incubation time, temperature and treatment concentration. Optimised physiochemical treatments were then compared. The most effective treatment methods were seed washes in acidified electrolytic water (400 ppm hypochlorous acid for 5 min) and hypochlorite solution (2% NaOCI for 5 min). In seed to seedling transmission assays, these two treatments reduced transmission of P. somniferi by 88.8% and 74.61%, and P. meconopsidis by 93.3% and 100%, respectively. These methods are recommended for seed treatment of commercial opium poppy seed to assist in the control of the downy mildew diseases.


Assuntos
Papaver/microbiologia , Peronospora/patogenicidade , Doenças das Plantas/prevenção & controle , Sementes/microbiologia , Austrália , Eletrólitos/farmacologia , Ácido Hipocloroso/farmacologia , Peronospora/efeitos dos fármacos , Filogenia , Doenças das Plantas/microbiologia , Plântula/efeitos dos fármacos , Plântula/microbiologia , Sementes/efeitos dos fármacos
17.
J Vis Exp ; (157)2020 03 10.
Artigo em Inglês | MEDLINE | ID: mdl-32225144

RESUMO

Tomato is an agronomically important crop that can be infected by Pseudomonas syringae, a Gram-negative bacterium, resulting in bacterial speck disease. The tomato-P. syringae pv. tomato pathosystem is widely used to dissect the genetic basis of plant innate responses and disease resistance. While disease was successfully managed for many decades through the introduction of the Pto/Prf gene cluster from Solanum pimpinellifolium into cultivated tomato, race 1 strains of P. syringae have evolved to overcome resistance conferred by the Pto/Prf gene cluster and occur worldwide. Wild tomato species are important reservoirs of natural diversity in pathogen recognition, because they evolved in diverse environments with different pathogen pressures. In typical screens for disease resistance in wild tomato, adult plants are used, which can limit the number of plants that can be screened due to their extended growth time and greater growth space requirements. We developed a method to screen 10-day-old tomato seedlings for resistance, which minimizes plant growth time and growth chamber space, allows a rapid turnover of plants, and allows large sample sizes to be tested. Seedling outcomes of survival or death can be treated as discrete phenotypes or on a resistance scale defined by amount of new growth in surviving seedlings after flooding. This method has been optimized to screen 10-day-old tomato seedlings for resistance to two P. syringae strains and can easily be adapted to other P. syringae strains.


Assuntos
Bioensaio/métodos , Resistência à Doença , Lycopersicon esculentum/microbiologia , Doenças das Plantas/microbiologia , Pseudomonas syringae/fisiologia , Plântula/microbiologia , Cotilédone/fisiologia , Meios de Cultura , Ecótipo , Lycopersicon esculentum/genética , Lycopersicon esculentum/crescimento & desenvolvimento , Fenótipo , Esterilização
18.
J Appl Microbiol ; 129(4): 958-970, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32329126

RESUMO

AIMS: Pinus massoniana is one of the most widely distributed forest plants in China. In this study, we isolated a bacterial endophyte (designated FBS135) from apical buds and needles of P. massoniana. Investigations were performed to understand the effects of the strain on pine growth, its genomic features and the functions of the plasmids it carries. METHODS AND RESULTS: Based on its morphological features and 16S rRNA sequence, strain FBS135 was primarily identified as Pantoea eucalypti. We found that FBS135 not only promoted the growth of P. massoniana seedlings, but also significantly increased the survival rate of pine seedlings. The whole genome of FBS135 was sequenced, which revealed that the bacterium carries one chromosome and four plasmids. Its chromosome is 4 023 751 bp in size and contains dozens of genes involved in plant symbiosis. Curing one of the four plasmids, pPant1, resulted in a decrease in the size of the FBS135 colonies and the loss of the ability to synthesize yellow pigment, indicating that this plasmid may be very important for FBS135. CONCLUSIONS: Pantoea eucalypti FBS135 has a genomic basis to be implicated in plant-associated lifestyle and was established to have the capability to promote pine growth. SIGNIFICANCE AND IMPACT OF THE STUDY: To the best of our knowledge, this is the first report that such a bacterial species, P. eucalypti, was isolated from pine trees and evidenced to have pine beneficial activities. Our results elucidate the ecological effects of endophytes on forest plants as well as endophyte-plant interaction mechanisms.


Assuntos
Genoma Bacteriano/genética , Pantoea/fisiologia , Pinus/crescimento & desenvolvimento , Pinus/microbiologia , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , China , Endófitos/classificação , Endófitos/genética , Endófitos/fisiologia , Pantoea/classificação , Pantoea/genética , Plasmídeos/genética , Plasmídeos/metabolismo , RNA Ribossômico 16S/genética , Plântula/crescimento & desenvolvimento , Plântula/microbiologia , Simbiose
19.
Microbiome ; 8(1): 49, 2020 04 06.
Artigo em Inglês | MEDLINE | ID: mdl-32252828

RESUMO

BACKGROUND: Myxobacteria are micropredators in the soil ecosystem with the capacity to move and feed cooperatively. Some myxobacterial strains have been used to control soil-borne fungal phytopathogens. However, interactions among myxobacteria, plant pathogens, and the soil microbiome are largely unexplored. In this study, we aimed to investigate the behaviors of the myxobacterium Corallococcus sp. strain EGB in the soil and its effect on the soil microbiome after inoculation for controlling cucumber Fusarium wilt caused by Fusarium oxysporum f. sp. cucumerinum (FOC). RESULTS: A greenhouse and a 2-year field experiment demonstrated that the solid-state fermented strain EGB significantly reduced the cucumber Fusarium wilt by 79.6% (greenhouse), 66.0% (2015, field), and 53.9% (2016, field). Strain EGB adapted to the soil environment well and decreased the abundance of soil-borne FOC efficiently. Spatiotemporal analysis of the soil microbial community showed that strain EGB migrated towards the roots and root exudates of the cucumber plants via chemotaxis. Cooccurrence network analysis of the soil microbiome indicated a decreased modularity and community number but an increased connection number per node after the application of strain EGB. Several predatory bacteria, such as Lysobacter, Microvirga, and Cupriavidus, appearing as hubs or indicators, showed intensive connections with other bacteria. CONCLUSION: The predatory myxobacterium Corallococcus sp. strain EGB controlled cucumber Fusarium wilt by migrating to the plant root and regulating the soil microbial community. This strain has the potential to be developed as a novel biological control agent of soil-borne Fusarium wilt. Video abstract.


Assuntos
Agentes de Controle Biológico , Cucumis sativus/microbiologia , Fusarium/patogenicidade , Myxococcales/fisiologia , Doenças das Plantas/microbiologia , Microbiologia do Solo , Antibiose , Microbiota , Myxococcales/genética , Doenças das Plantas/prevenção & controle , Raízes de Plantas/microbiologia , Plântula/microbiologia
20.
J Appl Microbiol ; 129(3): 637-651, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32181551

RESUMO

AIMS: The objective of this work was to identify a fungal strain showing potential biocontrol abilities against two Fusarium damping-off agents and to test it as a Biological Control Agent (BCA) in maize seed coating under field conditions. METHODS AND RESULTS: A collection of native fungal strains associated with maize in Belgium was screened for antagonistic potential against Fusarium avenaceum and Fusarium culmorum. The strain with highest biocontrol potential was identified as an endophytic Trichoderma atroviride BC0584. In greenhouse, it significantly improves the emergence of seedlings infected by F. avenaceum or F. culmorum pathogens. In most field trials carried out during the season 2017, it significantly increased the emergence rate of infected seedlings compared to untreated seeds. One slurriable powder formulation allows BCA conidia to survive over a 6-month storage period at 4°C. CONCLUSIONS: The fungal BC0584 strain is a promising BCA that could be an alternative to synthetic fungicides. It is adapted to local environmental conditions, is easily and cheaply produced and can be stored in a low-cost formulation. SIGNIFICANCE AND IMPACT OF THE STUDY: In Belgium, this is the first study to use a T. atroviride native strain against Fusarium damping-off on maize crop. Modes of action and required conditions for ensuring high biocontrol activity in the field have still to be investigated.


Assuntos
Fusarium/patogenicidade , Controle Biológico de Vetores/métodos , Doenças das Plantas/prevenção & controle , Trichoderma/fisiologia , Zea mays/microbiologia , Bélgica , Doenças das Plantas/microbiologia , Plântula/crescimento & desenvolvimento , Plântula/microbiologia , Sementes/microbiologia , Esporos Fúngicos/fisiologia , Zea mays/genética
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