The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Qirong Shen - One of the best experts on this subject based on the ideXlab platform.
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seasonal variation in the Biocontrol efficiency of bacterial wilt is driven by temperature mediated changes in bacterial competitive interactions
Journal of Applied Ecology, 2017Co-Authors: Zhong Wei, Qirong Shen, Jianfeng Huang, Tianjie Yang, Alexandre Jousset, Villepetri FrimanAbstract:Summary Microbe-based Biocontrol applications hold the potential to become an efficient way to control plant pathogen disease outbreaks in the future. However, their efficiency is still very variable, which could be due to their sensitivity to the abiotic environmental conditions. Here, we assessed how environmental temperature variation correlates with ability of Ralstonia pickettii, an endophytic bacterial Biocontrol agent, to suppress the Ralstonia solanacearum pathogen during different tomato crop seasons in China. We found that suppression of the pathogen was highest when the seasonal mean temperatures were around 20 °C and rapidly decreased with increasing mean crop season temperatures. Interestingly, low levels of disease incidence did not correlate with low pathogen or high Biocontrol agent absolute densities. Instead, the Biocontrol to pathogen density ratio was a more important predictor of disease incidence levels between different crop seasons. To understand this mechanistically, we measured the growth and strength of competition between the Biocontrol agent and the pathogen over a naturally occurring temperature gradient in vitro. We found that the Biocontrol strain grew relatively faster at low temperature ranges, and the pathogen at high temperature ranges, and that similar to field experiments, pathogen suppression peaked at 20 °C. Together, our results suggest that temperature-mediated changes in the strength of bacterial competition could potentially explain the variable R. solanacearum Biocontrol outcomes between different crop seasons in China. Synthesis and applications. Our results suggest that abiotic environmental conditions, such as temperature, can affect the efficacy of Biocontrol applications. Thus, in order to develop more consistent Biocontrol applications in the future, we might need to find and isolate bacterial strains that can retain their functionality regardless of the changing environmental conditions.
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enhanced root colonization and Biocontrol activity of bacillus amyloliquefaciens sqr9 by abrb gene disruption
Applied Microbiology and Biotechnology, 2013Co-Authors: Jun Weng, Juan Li, Yang Wang, Qirong Shen, Ruifu ZhangAbstract:Root colonization by antagonistic bacteria is a prerequisite for successful biological control, and the instability of colonization under varying environmental conditions has accentuated the need to improve the colonization activity. Root colonization by Bacillus spp. is mainly determined by chemotaxis and biofilm formation, and both functions are negatively controlled by the global transcription regulator AbrB. Here, we disrupted the gene abrB in Bacillus amyloliquefaciens SQR9, which has been proven to be a promising Biocontrol agent of cucumber and watermelon wilt disease. Chemotaxis, biofilm formation, and colonization activities as well as Biocontrol efficiency were measured and compared between the wild-type strain of SQR9 and the abrB mutant. The data presented in this article demonstrate that the colonization and Biocontrol activity of B. amyloliquefaciens SQR9 could be significantly improved by abrB gene disruption. The results offer a new strategy to enhance the Biocontrol efficacy of B. amyloliquefaciens SQR9.
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two bacillus amyloliquefaciens strains isolated using the competitive tomato root enrichment method and their effects on suppressing ralstonia solanacearum and promoting tomato plant growth
Crop Protection, 2013Co-Authors: Shiyong Tan, Jianfeng Huang, Ning Ling, Yi Jiang, Song Song, Qirong ShenAbstract:Two tomato root colonizing strains, Bacillus amyloliquefacien CM-2 and T-5, were isolated after the enrichment procedure on the roots of tomato seedlings, and evaluated for their antagonistic activities against pathogenic Ralstonia solanacearum (RS) in vitro. Three inoculation methods were used to test their Biocontrol efficacy and growth promotion effects in greenhouse based on their colonization ability in rhizosphere soil. Both CM-2 and T-5 strains showed strong Biocontrol and growth promotion effects on tomato seedlings. The best Biocontrol efficacy was obtained by treating both seedlings and soils with the Biocontrol agents. In comparison to the control, the disease incidence was reduced by 70.1 and 79.4% for CM-2 and T-5, respectively. The numbers of colony-forming units of RS in rhizosphere soil were significantly (P < 0.05) decreased as compared to the control. The density of both strains in the rhizosphere soils remained at a high level (≥107 CFU/g) during a five-week period. Both strains were recovered from the interior of the stems and roots of plants. They showed positive reactions for ammoina, indole acetic acid and siderophores production, and phosphate solubilizing activity. Our data proved the potential of isolated strains for the Biocontrol of tomato bacterial wilt.
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development of a mode of application of bioorganic fertilizer for improving the Biocontrol efficacy to fusarium wilt
Biocontrol, 2010Co-Authors: Ning Ling, Qiwei Huang, Xingming Yang, Yangchun Xu, Qirong ShenAbstract:More effective ways of applying Biocontrol products should be developed based both on the characteristics of the Biocontrol agents and the normal practices of the agricultural producer. A new system was developed to improve the Biocontrol efficacy of Fusarium wilt for watermelon production, and this system was tested in pot and field experiments. Biocontrol was achieved by applying a novel bioorganic fertilizer product (BIO) to Fusarium-infested soil. The best Biocontrol was obtained by application of a bioorganic fertilizer, BIO, into soil during the nursery phase of watermelon seedling followed by a second application to Fusarium-infested soil when watermelon seedlings were transplanted. In comparison with the controls, the incidence of the disease was reduced by 60–100% in the pot experiment and by 59–73% in the field experiment when the BIO was applied during the nursery stage. After application of BIO during the nursery stage, the number of colony-forming units of Fusarium oxysporum in rhizospheric soil was significantly (P < 0.05) inhibited compared to the controls. An in vitro experiment showed that the antagonist Paenibacillus polymyxa in the BIO could effectively colonize the rhizosphere of watermelon and proliferate along the extending plant roots. This inhibited growth of Fusarium oxysporum in the rhizosphere of watermelon and protected the watermelon roots from attack by the pathogens. The method used for Biocontrol Fusarium wilt disease in watermelon should be a useful strategy to improve field efficacy of other Biocontrol agents.
I Garciaacha - One of the best experts on this subject based on the ideXlab platform.
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molecular characterization and identification of Biocontrol isolates of trichoderma spp
Applied and Environmental Microbiology, 2000Co-Authors: M R Hermosa, I Grondona, Enrique A Iturriaga, Jose Maria Diazminguez, C Castro, Enrique Monte, I GarciaachaAbstract:The most common biological control agents (BCAs) of the genus Trichoderma have been reported to be strains of Trichoderma virens, T. harzianum, and T. viride. Since Trichoderma BCAs use different mechanisms of Biocontrol, it is very important to explore the synergistic effects expressed by different genotypes for their practical use in agriculture. Characterization of 16 Biocontrol strains, previously identified as “Trichoderma harzianum” Rifai and one Biocontrol strain recognized as T. viride, was carried out using several molecular techniques. A certain degree of polymorphism was detected in hybridizations using a probe of mitochondrial DNA. Sequencing of internal transcribed spacers 1 and 2 (ITS1 and ITS2) revealed three different ITS lengths and four different sequence types. Phylogenetic analysis based on ITS1 sequences, including type strains of different species, clustered the 17 Biocontrol strains into four groups: T. harzianum-T. inhamatum complex, T. longibrachiatum, T. asperellum, and T. atroviride-T. koningii complex. ITS2 sequences were also useful for locating the Biocontrol strains in T. atroviride within the complex T. atroviride-T. koningii. None of the Biocontrol strains studied corresponded to biotypes Th2 or Th4 of T. harzianum, which cause mushroom green mold. Correlation between different genotypes and potential Biocontrol activity was studied under dual culturing of 17 BCAs in the presence of the phytopathogenic fungi Phoma betae, Rosellinia necatrix, Botrytis cinerea, and Fusarium oxysporum f. sp. dianthi in three different media.
Ragan M Callaway - One of the best experts on this subject based on the ideXlab platform.
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insect herbivory stimulates allelopathic exudation by an invasive plant and the suppression of natives
Ecology Letters, 2005Co-Authors: Giles C Thelen, Jorge M Vivanco, Beth A Newingham, William Good, Harsh P Bais, Peter Landres, A J Caesar, Ragan M CallawayAbstract:Exotic invasive plants are often subjected to attack from imported insects as a method of biological control. A fundamental, but rarely explicitly tested, assumption of biological control is that damaged plants are less fit and compete poorly. In contrast, we find that one of the most destructive invasive plants in North America, Centaurea maculosa, exudes far higher amounts of (±)-catechin, an allelopathic chemical known to have deleterious effects on native plants, when attacked by larvae of two different root boring Biocontrol insects and a parasitic fungus. We also demonstrate that C. maculosa plants experimentally attacked by one of these Biocontrols exhibit more intense negative effects on natives.
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indirect effects of host specific biological control agents
Trends in Ecology and Evolution, 2003Co-Authors: Dean E Pearson, Ragan M CallawayAbstract:Biological control is a crucial tool in the battle against biological invasions, but Biocontrol agents can have a deleterious impact on native species. Recognition of risks associated with host shifting has increased the emphasis on host specificity of Biocontrol agents for invasive weeds. However, recent studies indicate host-specific Biocontrol agents can also exhibit substantial nontarget effects through indirect interactions and food-web subsidies. Based on an evaluation of these studies, we conclude that the interaction strength between Biocontrol agents and their hosts is at least as important as host specificity for determining the outcome of Biocontrol introductions. Host-specific Biocontrol agents that establish, but fail to reduce the densities of their hosts can facilitate bottom-up effects that link the target weed to other native organisms through food webs, thereby expanding the impacts of the invasive weed. We believe that indirect nontarget effects of host-specific Biocontrol agents arising from food-web subsidies could prove more deleterious to native species than are the direct nontarget effects currently recognized from host shifting.
M R Hermosa - One of the best experts on this subject based on the ideXlab platform.
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molecular characterization and identification of Biocontrol isolates of trichoderma spp
Applied and Environmental Microbiology, 2000Co-Authors: M R Hermosa, I Grondona, Enrique A Iturriaga, Jose Maria Diazminguez, C Castro, Enrique Monte, I GarciaachaAbstract:The most common biological control agents (BCAs) of the genus Trichoderma have been reported to be strains of Trichoderma virens, T. harzianum, and T. viride. Since Trichoderma BCAs use different mechanisms of Biocontrol, it is very important to explore the synergistic effects expressed by different genotypes for their practical use in agriculture. Characterization of 16 Biocontrol strains, previously identified as “Trichoderma harzianum” Rifai and one Biocontrol strain recognized as T. viride, was carried out using several molecular techniques. A certain degree of polymorphism was detected in hybridizations using a probe of mitochondrial DNA. Sequencing of internal transcribed spacers 1 and 2 (ITS1 and ITS2) revealed three different ITS lengths and four different sequence types. Phylogenetic analysis based on ITS1 sequences, including type strains of different species, clustered the 17 Biocontrol strains into four groups: T. harzianum-T. inhamatum complex, T. longibrachiatum, T. asperellum, and T. atroviride-T. koningii complex. ITS2 sequences were also useful for locating the Biocontrol strains in T. atroviride within the complex T. atroviride-T. koningii. None of the Biocontrol strains studied corresponded to biotypes Th2 or Th4 of T. harzianum, which cause mushroom green mold. Correlation between different genotypes and potential Biocontrol activity was studied under dual culturing of 17 BCAs in the presence of the phytopathogenic fungi Phoma betae, Rosellinia necatrix, Botrytis cinerea, and Fusarium oxysporum f. sp. dianthi in three different media.
Villepetri Friman - One of the best experts on this subject based on the ideXlab platform.
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seasonal variation in the Biocontrol efficiency of bacterial wilt is driven by temperature mediated changes in bacterial competitive interactions
Journal of Applied Ecology, 2017Co-Authors: Zhong Wei, Qirong Shen, Jianfeng Huang, Tianjie Yang, Alexandre Jousset, Villepetri FrimanAbstract:Summary Microbe-based Biocontrol applications hold the potential to become an efficient way to control plant pathogen disease outbreaks in the future. However, their efficiency is still very variable, which could be due to their sensitivity to the abiotic environmental conditions. Here, we assessed how environmental temperature variation correlates with ability of Ralstonia pickettii, an endophytic bacterial Biocontrol agent, to suppress the Ralstonia solanacearum pathogen during different tomato crop seasons in China. We found that suppression of the pathogen was highest when the seasonal mean temperatures were around 20 °C and rapidly decreased with increasing mean crop season temperatures. Interestingly, low levels of disease incidence did not correlate with low pathogen or high Biocontrol agent absolute densities. Instead, the Biocontrol to pathogen density ratio was a more important predictor of disease incidence levels between different crop seasons. To understand this mechanistically, we measured the growth and strength of competition between the Biocontrol agent and the pathogen over a naturally occurring temperature gradient in vitro. We found that the Biocontrol strain grew relatively faster at low temperature ranges, and the pathogen at high temperature ranges, and that similar to field experiments, pathogen suppression peaked at 20 °C. Together, our results suggest that temperature-mediated changes in the strength of bacterial competition could potentially explain the variable R. solanacearum Biocontrol outcomes between different crop seasons in China. Synthesis and applications. Our results suggest that abiotic environmental conditions, such as temperature, can affect the efficacy of Biocontrol applications. Thus, in order to develop more consistent Biocontrol applications in the future, we might need to find and isolate bacterial strains that can retain their functionality regardless of the changing environmental conditions.