The contribution of foliar endophytes to quantitative resistance to <i>Melampsora</i> rust

Raghavendra, Anil; Newcombe, George

doi:10.1111/nph.12066

Cited by 73 publications

(75 citation statements)

References 30 publications

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“…Quantitative resistance does not completely prevent infection, but rather involves many genes working together to reduce pathogen latent period, infection efficiency and/or spore production (Geiger and Heun 1989). Raghavendra and Newcombe (2013) found that different endophytes reduced rust locally (i.e., not systemically) by varying degrees (0.6 to 16 times). Overall, variation among endophyteinoculated and control leaves explained 54% of the observed variation in rust symptom severity, whereas host genotype explained only 5.0%, and host genotype-by-endophyte interaction only 1% (i.e., the endophytes were consistently ranked in the magnitude of their effects across genotypes).…”

Section: Introductionmentioning

confidence: 99%

“…In fact, endophyte effects almost completely swamped plant genotypic effects on pathogens, leading to the hypothesis that endophytes are a second line of pathogen defense in plants-after major genes for resistance (Flor 1955), but before quantitative genetic resistance (Raghavendra and Newcombe 2013).…”

Section: Introductionmentioning

confidence: 99%

“…Controlled inoculation studies have shown that particular fungal leaf endophyte species can reduce disease in their plant hosts (Arnold et al 2003, Ganley et al 2008, Raghavendra and Newcombe 2013. Variation in host plant genotype is also well known to influence disease: genetic resistance, which can vary among plant genotypes, strongly determines pathogen symptom severity (Jones and Dangl 2006).…”

Section: Introductionmentioning

confidence: 99%

“…One such recent study evaluated how four different fungal leaf endophytes influenced resistance to the biotrophic rust pathogen Melampsora x columbiana in six different Populus host genotypes differing in quantitative resistance to the rust (Raghavendra and Newcombe 2013). Quantitative resistance does not completely prevent infection, but rather involves many genes working together to reduce pathogen latent period, infection efficiency and/or spore production (Geiger and Heun 1989).…”

Section: Introductionmentioning

confidence: 99%

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Leaf endophytes and Populus genotype affect severity of damage from the necrotrophic leaf pathogen, Drepanopeziza populi

et al. 2013

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Abstract. Fungal leaf endophytes-nonpathogenic microfungi that live within plant leaves-are ubiquitous in land plants. Leaf endophytes and host plant genotypes may interact to determine plant disease severity. In a greenhouse inoculation experiment, we found that leaf endophyte species and Populus angustifolia genotypes both affected disease outcomes in plants inoculated with the necrotrophic leaf pathogen Drepanopeziza populi. Contrary to many studies showing endophytes conferring defense, all plant genotypes inoculated with the endophyte Penicillium sp. prior to inoculation with the pathogen D. populi were characterized by greater pathogen symptom severity than plants inoculated with the pathogen only. We quantified defense gene expression via qRT-PCR, but found no evidence that increased pathogen damage was related to differential expression of the assayed genes. A second endophyte, Truncatella angustata, which was previously found to reduce symptom severity of the biotrophic pathogen Melampsora in Populus trichocarpa, did not affect symptom severity of the necrotrophic pathogen D. populi or defense gene expression. Overall, our study highlights the variable effects of endophytes on pathogen symptom severity, and illustrates that plant genotypic variation can remain important for disease outcomes even in the presence of endophytes altering disease. Additional work is needed to elucidate the mechanism by which fungal leaf endophytes alter disease in their host plants.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Leaf endophytes and Populus genotype affect severity of damage from the necrotrophic leaf pathogen, Drepanopeziza populi

et al. 2013

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“…Likewise, neither nematode species has been reported to cause damage to plants. The presence of fungal-feeding nematodes undoubtedly affects the balance of endophytic fungi within a leaf community, and incidence of disease can depend as much or more on composition of endophyte species than on plant genotype (Raghavendra and Newcombe, 2013). Furthermore, the ability of an Aphelenchoides species to cause plant disease may depend on the composition of different endophytic fungi within a given host.…”

Section: Discussionmentioning

confidence: 99%

Morphological and Molecular Characterization of Two Aphelenchoides Endophytic in Poplar Leaves

Carta

Skantar

et al. 2016

Journal of Nematology

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During a long-term, large network study of the ecology of plant endophytes in native habitats, various nematodes have been found. Two poplar species, Populus angustifolia (narrowleaf cottonwood) and Populus trichocarpa (black cottonwood), are important ecological and genomic models now used in ongoing plant-pathogen-endophyte interaction studies. In this study, two different aphelenchid nematodes within surface-sterilized healthy leaves of these two Populus spp. in northwestern North America were discovered. Nematodes were identified and characterized microscopically and molecularly with 28S ribosomal RNA (rRNA) and 18S rRNA molecular markers. From P. angustifolia, Aphelenchoides saprophilus was inferred to be closest to another population of A. saprophilus among sequenced taxa in the 18S tree. From P. trichocarpa, Laimaphelenchus heidelbergi had a 28S sequence only 1 bp different from that of a Portuguese population, and 1 bp different from the original Australian type population. The 28S and 18S rRNA trees of Aphelenchoides and Laimaphelenchus species indicated L. heidelbergi failed to cluster with three other Laimaphelenchus species, including the type species of the genus. Therefore, we support a conservative definition of the genus Laimaphelenchus, and consider these populations to belong to Aphelenchoides, amended as Aphelenchoides heidelbergi n. comb. This is the first report of these nematode species from within aboveground leaves. The presence of these fungal-feeding nematodes can affect the balance of endophytic fungi, which are important determinants of plant health.

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The Microbe‐Free Plant: Fact or Artifact

Heil¹

2015

Biological Nitrogen Fixation

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Plant-microbe interactions are ubiquitous. Plants are threatened by pathogens, but they are even more commonly engaged in neutral or mutualistic interactions with microbes: belowground microbial plant associates are mycorrhizal fungi, Rhizobia, and plant-growth promoting rhizosphere bacteria, aboveground plant parts are colonized by internally living bacteria and fungi (endophytes) and by microbes in the phyllosphere (epiphytes). We emphasize here that a completely microbe-free plant is an exotic exception rather than the biologically relevant rule. The complex interplay of such microbial communities with the host-plant affects multiple vital parameters such as plant nutrition, growth rate, resistance to biotic and abiotic stressors, and plant survival and distribution.The mechanisms involved reach from direct ones such as nutrient acquisition, the production of plant hormones, or direct antibiosis, to indirect ones that are mediated by effects on host resistance genes or via interactions at higher trophic levels. Plant-associated microbes are heterotrophic and cause costs to their host plant, whereas the benefits depend on the current environment. Thus, the outcome of the interaction for the plant host is highly context dependent. We argue that considering the microbe-free plant as the "normal" or control stage significantly impairs research into important phenomena such as (1) phenotypic and epigenetic plasticity, (2) the "normal" ecological outcome of a given interaction, and (3) the evolution of plants. For the future, we suggest cultivation-independent screening methods using direct PCR from plant tissue of more than one fungal and bacterial gene to collect data on the true microbial diversity in wild plants. The patterns found could be correlated to host species and environmental conditions, in order to formulate testable hypotheses on the biological roles of plant endophytes in nature. Experimental approaches should compare different host-endophyte combinations under various relevant environmental conditions and study at the genetic, epigenetic, transcriptional, and physiological level the parameters that cause the interaction to shift along the mutualism-parasitism continuum.

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The contribution of foliar endophytes to quantitative resistance to Melampsora rust

Cited by 73 publications

References 30 publications

Leaf endophytes and Populus genotype affect severity of damage from the necrotrophic leaf pathogen, Drepanopeziza populi

Leaf endophytes and Populus genotype affect severity of damage from the necrotrophic leaf pathogen, Drepanopeziza populi

Morphological and Molecular Characterization of Two Aphelenchoides Endophytic in Poplar Leaves

The Microbe‐Free Plant: Fact or Artifact

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