Context‐dependent interactions between pathogens and a mutualist affect pathogen fitness and mutualist benefits to hosts

Marchetto, Katherine M.; Power, Alison G.

doi:10.1002/ecy.2531

Cited by 11 publications

(14 citation statements)

References 51 publications

(77 reference statements)

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“…It is also worth investigating whether other types of pathogens have similar effects on plant NDFA. There are data that suggest the reduction in NDFA in virus‐infected plants is related to changes in the concentration of an immune hormone, salicylic acid (Marchetto and Power 2018). Plants infected with viruses and other biotrophic pathogens tend to have higher concentrations of salicylic acid (SA) than healthy plants (Abdullah et al 2017).…”

Section: Discussionmentioning

confidence: 99%

“… Data sources: a, Kandel (2014); b, Marchetto and Power (2018); c, Clark and Carpenter (2000); d, Ross et al (2009); e, Khadhair et al (1984); f, Smith and Maxwell (1971); g, Sofy et al (2014); h, Bohl (1981); i, Ohki et al (1986); j, Justes et al (2002); k, Goins and Russelle (1996); l, Lemaire et al (1992); m, Robbins and Carter (1980); n, Chen et al (2004). …”

Section: Methodsmentioning

confidence: 99%

“…N out is the summation over all disease classes of the amount of soil nitrogen removed from the system with the seed harvest, where s i is seed mass per plant and N seed is the percentage of nitrogen in seeds. While the model assumes that pod tissue is left in the field with the vegetative crop residue after in‐field combining, the nitrogen content of the pods is so low (Marchetto and Power 2018) that it doesn't make much difference if a farmer instead threshes the beans at a separate location

N_{in} = \underset{i}{false\sum} π_{i} d f_{i} (v_{i} N_{i}^{veg} + p_{i} N^{pod})

N_{out} = \underset{i}{false\sum} π_{i} d s_{i} N^{seed} (1 ‐ f_{i})

{NNI}_{bean} = N_{in} ‐ N_{out} .

…”

Section: Methodsmentioning

confidence: 99%

“…Nodulation of (A) healthy common bean; (B) common bean infected with one virus: Bean common mosaic virus, (C) common beans infected with two viruses: Bean common mosaic virus and Clover yellow vein virus. Nodulation and the percentage of nitrogen in plant tissues derived from the atmosphere (NDFA) decline as the number of viral species infecting a plant increases from zero to two (Marchetto and Power 2018). and reproductive biomass were collected, dried, and weighed.…”

Section: Methodsmentioning

confidence: 99%

“…1). For instance, nitrogen fixation significantly decreases when a legume is infected by a virus (Khadhair et al 1984, Ohki et al 1986, Marchetto and Power 2018). This will decrease the NNI of virus‐infected legume fields, but NFRVs recommended to farmers do not account for damage due to plant viruses.…”

Section: Introductionmentioning

confidence: 99%

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Viral infection can reduce the net nitrogen inputs of legume break crops and cover crops

Marchetto

Power

2020

Ecological Applications

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Legumes are used in crop rotations by both large‐scale and smallholder farmers alike to increase soil fertility, especially before high‐nitrogen‐demanding crops such as corn (maize). Legume crop residues and green manures are rich in nitrogen due to mutualistic rhizobia, bacteria that live in their roots and convert atmospheric nitrogen into a biologically available form. Growers can obtain recommendations from local extension offices about how much less inorganic nitrogen fertilizer needs to be added to a subsequent crop following different legume break crops for the predominant soil type (the nitrogen fertilizer replacement value, or NFRV). Due to the intimate relationship between legumes and rhizobia, conditions that affect plant health can also affect the rhizobia and how much nitrogen they provide. We use a combination of empirical data and previously published values to estimate reductions in nitrogen inputs under outbreaks of plant viruses of varying severity. We also use historical fertilizer prices to examine the economic impacts of this lost fertilizer for farmers. We find that fertilizer losses are greatest for crops that fix large amounts of nitrogen, such as clover and alfalfa as opposed to common bean. The economic impact on farmers is controlled by the proportion of plants with viral infections and the price of synthetic fertilizer. In a year of high disease prevalence, attention is normally focused on the yield of the diseased crops. We suggest that farmers growing legumes as break crops should be concerned about yields of subsequent crops as well. Viral diseases can be difficult to diagnose in the field, so the easiest way for farmers to prevent unexpected yield losses in subsequent crops is to test their soil when it is feasible to do so.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

N_{in} = \underset{i}{false\sum} π_{i} d f_{i} (v_{i} N_{i}^{veg} + p_{i} N^{pod})

N_{out} = \underset{i}{false\sum} π_{i} d s_{i} N^{seed} (1 ‐ f_{i})

{NNI}_{bean} = N_{in} ‐ N_{out} .

…”

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Viral infection can reduce the net nitrogen inputs of legume break crops and cover crops

Marchetto

Power

2020

Ecological Applications

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Competition mode and soil nutrient status shape the role of soil microbes in the diversity–invasibility relationship

Li,

Hu,

Geng

et al. 2024

Ecology and Evolution

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Understanding the relationship between plant diversity and invasibility is essential in invasion ecology. Species‐rich communities are hypothesized to be more resistant to invasions than species‐poor communities. However, while soil microorganisms play a crucial role in regulating this diversity–invasibility relationship, the effects of plant competition mode and soil nutrient status on their role remain unclear. To address this, we conducted a two‐stage greenhouse experiment. Soils were first conditioned by growing nine native species separately in them for 1 year, then mixed in various configurations with soils conditioned using one, three, or six species, respectively. Next, we inoculated the mixed soil into sterilized substrate soil and planted the alien species Rhus typhina and native species Ailanthus altissima as test plants. We set up two competition modes (intraspecific and interspecific) and two nutrient levels (fertilization using slow‐release fertilizer and nonfertilization). Under intraspecific competition, regardless of fertilization, the biomass of the alien species was higher in soil conditioned by six native species. By contrast, under interspecific competition, the biomass increased without fertilization but remained stable with fertilization in soil conditioned by six native species. Analysis of soil microbes suggests that pathogens and symbiotic fungi in diverse plant communities influenced R. typhina growth, which varied with competition mode and nutrient status. Our findings suggest that the soil microbiome is pivotal in mediating the diversity–invasibility relationship, and this influence varies according to competition mode and nutrient status.

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Parasites disrupt a keystone mutualism that underpins the structure, functioning, and resilience of a coastal ecosystem

Morton,

Davis,

Walker

et al. 2024

Ecological Monographs

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Parasites can alter the traits or densities of mutualistic partners, potentially destabilizing mutualistic associations that underpin the structure, functioning, and stability of entire ecosystems. Despite the potentially wide‐ranging consequences of such disruptions, no studies have directly manipulated parasite prevalence and/or intensity in a mutualistic partner, nor quantified the resulting community‐level effects. Here, we investigated the effects of a common trematode parasite (Cercaria opaca) on the strength of a keystone facultative mutualism in western Atlantic salt marshes between the foundational marsh cordgrass, Spartina alterniflora, and the ribbed mussel, Geukensia demissa. Cordgrass increases mussel survivorship and growth through shading, while mussels enhance cordgrass growth by producing nutrient‐rich biodeposits. This mutualistic association also creates conditions that enhance biodiversity and ecosystem functioning, and mediates the ability of foundational plants to resist and recover from extreme drought. We used lab and field assays to show how increasing infection with trematode metacercariae negatively influenced mussel biodeposit production, as well as the strength of mussel shells and byssal attachments. By conducting a field manipulation using experimentally infected mussels, we demonstrated that the mutualistic benefits of mussels to cordgrass growth decreased with increasing trematode infection intensity—a pattern likely generated by reduced mussel biodeposition and enhanced mortality. Additionally, increasing parasite loads in mussels led to predictable decreases in the abundances of benthic invertebrates, as well as in key ecosystem characteristics and process rates (i.e., redox potential and sediment accretion). Finally, a survey of five North Carolina salt marshes demonstrated that infection with C. opaca was most common in mussels in areas experiencing cordgrass die‐off due to drought, and that infection intensity decreased with distance from die‐off areas. Because the mussel–cordgrass mutualism underpins marsh ecosystem resilience to drought‐associated die‐off, our results suggest that parasitism may depress recovery from these disturbances. Although this is the first experimental demonstration of parasites indirectly altering community structure and functioning by undermining an ecologically influential mutualism, this type of relationship could be common in nature, given that parasites frequently infect influential mutualists.

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Context‐dependent interactions between pathogens and a mutualist affect pathogen fitness and mutualist benefits to hosts

Cited by 11 publications

References 51 publications

Viral infection can reduce the net nitrogen inputs of legume break crops and cover crops

Viral infection can reduce the net nitrogen inputs of legume break crops and cover crops

Competition mode and soil nutrient status shape the role of soil microbes in the diversity–invasibility relationship

Parasites disrupt a keystone mutualism that underpins the structure, functioning, and resilience of a coastal ecosystem

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