Systemic resistance induced by localized virus infections: Extent of changes in uninfected plant parts

Most Pseudomonas biocontrol strains are associated with the rhizosphere of plants, where they control soil pathogens by antibiosis or competition, and leaf pathogens via induced systemic resistance. Genome mining and the division of the vastly heterogeneous genus Pseudomonas in phylogenomic (sub)groups has clarified the relation between biocontrol characteristics and phylogeny. Based on their activity, Pseudomonas biocontrol strains come in three types. A first type, represented by P. chlororaphis, P. protegens, P. corrugata and P. aeruginosa (sub)group strains, produces an arsenal of secondary metabolites with broad antimicrobial activity. The second type is found in the P. putida, P. fluorescens, P. koreensis, P. mandelii, and P. gessardii (sub)group. The spectrum of biocontrol properties of these strains is less diverse and involves siderophores and cyclic lipopeptides. The third type colonizes above-ground plant parts. Strains from this type mainly belong to the P. syringae group and are used to control postharvest pathogens. This chapter starts with recent advances in Pseudomonas taxonomy and a summary of its most important biocontrol traits. It then provides an overview of the most important Pseudomonas groups and subgroups harboring biocontrol strains. Examples of well-characterized and representative biocontrol strains show the links between phylogeny, ecology and biocontrol traits. The chapter concludes by reviewing commercially-available biocontrol strains.

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Pseudomonas fluorescens PTA-CT2 Triggers Local and Systemic Immune Response Against Botrytis cinerea in Grapevine

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-04-15-0092-r ◽

2015 ◽

Vol 28 (10) ◽

pp. 1117-1129 ◽

Cited By ~ 33

Author(s):

Charlotte Gruau ◽

Patricia Trotel-Aziz ◽

Sandra Villaume ◽

Fanja Rabenoelina ◽

Christophe Clément ◽

...

Keyword(s):

Immune Response ◽

Cell Death ◽

Pseudomonas Fluorescens ◽

Botrytis Cinerea ◽

Defense Responses ◽

Systemic Resistance ◽

Related Gene ◽

Plant Parts ◽

Defense Related Gene ◽

Below Ground

Although induced systemic resistance (ISR) is well-documented in the context of plant–beneficial bacteria interactions, knowledge about the local and systemic molecular and biochemical defense responses before or upon pathogen infection in grapevine is very scarce. In this study, we first investigated the capacity of grapevine plants to express immune responses at both above- and below-ground levels upon interaction with a beneficial bacterium, Pseudomonas fluorescens PTA-CT2. We then explored whether the extent of priming state could contribute to the PTA-CT2-induced ISR in Botrytis cinerea–infected leaves. Our data provide evidence that this bacterium colonized grapevine roots but not the above-ground plant parts and altered the plant phenotype that displayed multiple defense responses both locally and systemically. The grapevine roots and leaves exhibited distinct patterns of defense-related gene expression during root colonization by PTA-CT2. Roots responded faster than leaves and some responses were more strongly upregulated in roots than in leaves and vice versa for other genes. These responses appear to be associated with some induction of cell death in roots and a transient expression of HSR, a hypersensitive response-related gene in both local (roots) and systemic (leaves) tissues. However, stilbenic phytoalexin patterns followed opposite trends in roots compared with leaves but no phytoalexin was exuded during plant-bacterium interaction, suggesting that roots could play an important role in the transfer of metabolites contributing to immune response at the systemic level. Unexpectedly, in B. cinerea–infected leaves PTA-CT2-mediated ISR was accompanied in large part by a downregulation of different defense-related genes, including HSR. Only phytoalexins and glutathion-S-transferase 1 transcripts were upregulated, while the expression of anthocyanin biosynthetic genes was maintained at a higher level than the control. This suggests that decreased expression of HSR, as a marker of cell death, and activation of secondary metabolism pathways could be responsible for a reduced B. cinerea colonization capacity in bacterized plants.

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Biological Control of Plant Diseases with Composts

HortScience ◽

10.21273/hortsci.31.4.698b ◽

1996 ◽

Vol 31 (4) ◽

pp. 698b-698

Author(s):

Harry A.J. Hoitink ◽

Alex G. Stone ◽

David Y. Han ◽

Weidzheng Zhang ◽

Warren A. Dick

Keyword(s):

Plant Pathogens ◽

Plant Diseases ◽

Plant Roots ◽

Systemic Resistance ◽

Decomposition Level ◽

Loading Rates ◽

Plant Parts ◽

Root Rots ◽

Compost Plant ◽

Degree Of Control

Compost offers the potential to suppress root rots and vascular wilts caused by soilborne plant pathogens, as well as plant diseases affecting aerial plant parts. Many factors affect the degree of control obtained. They include the decomposition level (stability) of the compost, the types of microorganisms colonizing the organic matter after peak heating of the compost, plant nutrients released by the compost (fertility), its salinity, loading rates, and other factors. Biocontrol agents in composts induce suppression through various mechanisms, including competition, antibiosis, hyperparasitism, and the induction of systemic resistance in the plant (roots as well as foliage) to pathogens. Examples of each of the effects are reviewed.

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Robust RNAi-Based Resistance to Mixed Infection of Three Viruses in Soybean Plants Expressing Separate Short Hairpins from a Single Transgene

Phytopathology ◽

10.1094/phyto-02-11-0056 ◽

2011 ◽

Vol 101 (11) ◽

pp. 1264-1269 ◽

Cited By ~ 33

Author(s):

Xiuchun Zhang ◽

Shirley Sato ◽

Xiaohong Ye ◽

Anne E. Dorrance ◽

T. Jack Morris ◽

...

Keyword(s):

Mosaic Virus ◽

Virus Resistance ◽

Soybean Mosaic Virus ◽

Alfalfa Mosaic Virus ◽

Cauliflower Mosaic Virus ◽

Systemic Resistance ◽

35S Promoter ◽

Virus Infections ◽

Bean Pod Mottle Virus ◽

Soybean Plants

Transgenic plants expressing double-stranded RNA (dsRNA) of virus origin have been previously shown to confer resistance to virus infections through the highly conserved RNA-targeting process termed RNA silencing or RNA interference (RNAi). In this study we applied this strategy to soybean plants and achieved robust resistance to multiple viruses with a single dsRNA-expressing transgene. Unlike previous reports that relied on the expression of one long inverted repeat (IR) combining sequences of several viruses, our improved strategy utilized a transgene designed to express several shorter IRs. Each of these short IRs contains highly conserved sequences of one virus, forming dsRNA of less than 150 bp. These short dsRNA stems were interspersed with single-stranded sequences to prevent homologous recombination during the transgene assembly process. Three such short IRs with sequences of unrelated soybean-infecting viruses (Alfalfa mosaic virus, Bean pod mottle virus, and Soybean mosaic virus) were assembled into a single transgene under control of the 35S promoter and terminator of Cauliflower mosaic virus. Three independent transgenic lines were obtained and all of them exhibited strong systemic resistance to the simultaneous infection of the three viruses. These results demonstrate the effectiveness of this very straight forward strategy for engineering RNAi-based virus resistance in a major crop plant. More importantly, our strategy of construct assembly makes it easy to incorporate additional short IRs in the transgene, thus expanding the spectrum of virus resistance. Finally, this strategy could be easily adapted to control virus problems of other crop plants.

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Practical application of induced resistance to plant diseases: an appraisal of effectiveness under field conditions

The Journal of Agricultural Science ◽

10.1017/s0021859609008806 ◽

2009 ◽

Vol 147 (5) ◽

pp. 523-535 ◽

Cited By ~ 86

Author(s):

D. R. WALTERS ◽

J. M. FOUNTAINE

Keyword(s):

Induced Resistance ◽

Systemic Acquired Resistance ◽

Regulatory Protein ◽

Acquired Resistance ◽

Crop Protection ◽

Plant Growth Promoting Rhizobacteria ◽

Plant Diseases ◽

Systemic Resistance ◽

Plant Parts ◽

The Impact

SUMMARYPlants resist pathogen attack through a combination of constitutive and inducible defences. Different types of induced resistance have been defined based on differences in signalling pathways and spectra of effectiveness. Systemic acquired resistance (SAR) occurs in distal plant parts following localized infection by a necrotizing pathogen. It is controlled by a signalling pathway that depends upon the accumulation of salicylic acid (SA) and the regulatory protein NPR1. In contrast, induced systemic resistance (ISR) is promoted by selected strains of non-pathogenic plant growth-promoting rhizobacteria (PGPR). ISR functions independently of SA, but requires NPR1 and is regulated by jasmonic acid (JA) and ethylene (ET).Resistance can be induced by treatment with a variety of biotic and abiotic inducers. The resistance induced is broad spectrum and can be long-lasting, but is rarely complete, with most inducing agents providing between 0·20 and 0·85 disease control. In the field, expression of induced resistance is likely to be influenced by the environment, genotype, crop nutrition and the extent to which plants are already induced. Unfortunately, understanding of the impact of these influences on the expression of induced resistance is rudimentary. So too is understanding of how best to use induced resistance in practical crop protection. This situation will need to change if induced resistance is to fulfil its potential in crop protection.

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Systemic Resistance Induced by Trichoderma hamatum 382 in Cucumber Against Phytophthora Crown Rot and Leaf Blight

Plant Disease ◽

10.1094/pdis.2004.88.3.280 ◽

2004 ◽

Vol 88 (3) ◽

pp. 280-286 ◽

Cited By ~ 66

Author(s):

J. Khan ◽

J. J. Ooka ◽

S. A. Miller ◽

L. V. Madden ◽

H. A. J. Hoitink

Keyword(s):

Phytophthora Capsici ◽

Leaf Blight ◽

Crown Rot ◽

Fruit Rot ◽

Systemic Resistance ◽

Phytophthora Root Rot ◽

Plant Parts ◽

Trichoderma Hamatum ◽

Split Root ◽

Root And Crown Rot

Phytophthora root rot, crown rot, leaf and stem blight, and fruit rot of cucumber can cause serious losses, and are difficult to control. Although composts can be used successfully for control of Phytophthora root rots, little is known about their effects on Phytophthora diseases of aboveground plant parts. This research shows that the severity of Phytophthora root and crown rot of cucumber caused by Phytophthora capsici was suppressed significantly in cucumber transplants produced in a composted cow manure-amended mix compared with those in a dark sphagnum peat mix. In split root bioassays, Trichoderma hamatum 382 (T382) inoculated into the compost-amended potting mix significantly reduced the severity of Phytophthora root and crown rot on paired roots in the peat mix. This effect did not differ significantly from that provided by a drench with benzothiadiazole (BTH) or mefenoxam (Subdue MAXX). Based on area under disease progress curves, T382 also significantly reduced the severity of Phytophthora leaf blight in transplants produced in the compost mix compared with controls not inoculated with T382. Efficacy of T382 did not differ significantly from that provided by a drench with BTH. T382 re-mained spatially separated from the pathogen in plants in both the split root and leaf blight bioassays, suggesting that these effects were systemic in nature.

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