Bacterial seed endophyte shapes disease resistance in rice      

Matsumoto et al., 2021

Cereal crop production is severely affected by seed-borne bacterial diseases across the world. Locally occurring disease resistance in various crops remains elusive. Here, we have observed that rice plants of the same cultivar can be differentiated into disease-resistant and susceptible phenotypes under the same pathogen pressure. Following the identification of a seed-endophytic bacterium as the resistance-conferring agent, integration of high-throughput data, gene mutagenesis and molecular interaction assays facilitated the discovery of the underlying mode of action. Sphingomonas melonis that is accumulated and transmitted across generations in disease-resistant rice seeds confers resistance to disease-susceptible phenotypes by producing anthranilic acid. Without affecting cell growth, anthranilic acid interferes with the sigma factor RpoS of the seed-borne pathogen Burkholderia plantarii, probably leading to impairment of upstream cascades that are required for virulence factor biosynthesis. The overall findings highlight the hidden role of seed endophytes in the phytopathology paradigm of ‘disease triangles’, which encompass the plant, pathogens and environmental conditions. These insights are potentially exploitable for modern crop cultivation threatened by globally widespread bacterial diseases.

 

 https://www.nature.com/articles/s41477-020-00826-5

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Finally out of reach-
No bondage, no dependency.
How calm the ocean, 
Towering the void.
       
                                   Tessho

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Synchronization in nature 

Steven Strogatz 

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The clearest way into the Universe is through a forest wilderness. 

John Muir.  

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Can common mycorrhizal fungal networks be managed to enhance ecosystem functionality? 

Alaux et al, 2021

Mycorrhizal fungi are key components of soil biodiversity that offer potential to provide sustainable solutions for land management, notably in agriculture and forestry. Several studies conducted in controlled environments show that key functional attributes of common mycorrhizal networks (CMNs), which inter‐link different plants, are influenced by management practices. Here, we highlight the need to consider how land management affects the ubiquity and function of CMNs in nature to maximize the role of mycorrhizal fungi in enhancing ecosystem services. We emphasize that CMNs can sometimes negatively affect aspects of plant performance, but there remain major gaps in understanding before explicit consideration of CMN management can be delivered.

Most mycorrhizal fungi have the capacity to develop extensive extraradical mycelium, and thus have the potential to connect multiple plants and form a ‘common mycorrhizal network’. Several studies have shown that these networks can influence plant establishment, nutrition, productivity and defense, nutrient distribution and storage, and multitrophic interactions. However, many of these studies have focused on the importance of common mycorrhizal networks in ecological contexts and there has been less emphasis in managed systems, including croplands, grassland, agroforestry and forestry, on which humankind relies. Here we review the evidence of the potential importance of common mycorrhizal networks in managed systems, and provide insight into how these networks could be managed effectively to maximize the functions and outputs from managed systems. We also emphasize possible negative effects of common mycorrhizal networks on plant performance and question popular views that mycorrhizal networks may offer a panacea for enhancing ecosystem services. We highlight the need to gain greater insight into the ubiquity, functioning, and response to management interventions of common mycorrhizal networks and, critically, the need to determine the extent to which these networks can add value to the promotion of mycorrhizal colonization.

 

Impacts of mycorrhizal colonization and integration of plants into common mycorrhizal networks. The arrows indicate a hypothetical virtuous circle in which promotion of colonization may lead to more abundance CMNs, which leads to more effective colonization of seedlings. Green shading highlights those interventions and services that have greatest potential to be implemented in specific ecosystem.

https://nph.onlinelibrary.wiley.com/doi/10.1002/ppp3.10178

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Fundamentos Teóricos del Manejo Ecológico de Plagas y Enfermedades  

(una aproximación biomatemática) 

 

 

 

Curso libre: https://bit.ly/2IYmDVT

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Enhancing ecosystem services in apple orchards: Nest boxes increase pest control by insectivorous birds

García et al., 2020

1. Ecological intensification in croplands aims to enhance biodiversity‐based ecosystem services, helping to increase yield while reducing agricultural environmental impacts. Identifying ecological intensification tools of wide applicability and easily implemented by farmers is, therefore, an imperative. Here, we verify the efficiency of provisioning artificial nest boxes for insectivorous birds to reinforce pest biological control in apple orchards.
2. The study was conducted in 24 cider‐apple orchards in Asturias (NW Spain) over 3 years. We compared the effect of insectivorous birds between orchards with and without nest boxes occupied by different bird species, through insectivory estimates based on attack on a sentinel pest and measurements of arthropod abundance in apple trees. We also identified preys that birds of different species captured to feed nestlings.
3. Bird occupancy of nest boxes was widespread, ranging 25.0%–33.3% each year. Great tit was the dominant species, followed by blue tit and, occasionally, common redstart.
4. Predation pressure on apple pests increased in orchards with nest boxes, as judged by the increased proportion of sentinel models attacked by birds (34.9% increase in 2018 and 41.1% in 2019), decreased biomass of tree‐dwelling arthropods (−51.7%) and reduced probability of apple pest occurrence (from 57% to 40%), compared to orchards without nest boxes.
5. Nesting species showed different predatory roles in apple orchards. Fewer attacks on sentinel pests but lower arthropod biomass was associated with blue tit rather than great tit. Besides, blue tit fed nestlings at a faster rate and included in their diet a higher proportion of apple pests than great tit, which preyed mostly on other herbivorous insects.
6. Synthesis and applications. We demonstrated the usefulness of nest boxes for insectivorous birds in enhancing biological control of apple pests at a regional scale, identifying tit species as complementary predators of apple pests and herbivores. From the farmers' perspective, providing nest boxes in orchards may represent an efficient, easy to implement, cheap and attractive measure of ecological intensification, compatible with other actions fostering biodiversity in croplands. 

 

Schematic representation of the sampling design. In nest box orchard (a), 10 boxes were positioned in different apple trees at 15 m from the orchard edge and separated 20 m from each other. Each nest box occupied by birds for breeding was considered a sampling station, which, in turn, had three sampling points –single apple trees at 5, 15 and 50 m from the occupied nest box, in a line perpendicular to the edge and extending into the interior of the orchard. Every sampling station in the nest box orchards had a replicate in the paired control orchards (b), which was established in a tree at 15 m from the edge and had associated three sampling points on trees at 5, 15 and 50 m.

Boxplots representing the proportion of attacked caterpillar models (a) and arthropod biomass (mg) (log + 1 transformed) (b) in control (yellow) and nest box (green) orchards. Asterisks indicate significant differences (*p ≤ 0.05; ***p ≤ 0.001) between treatments.

https://bit.ly/3iUPPuJ

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The greatest delight which the fields and woods minister, is the suggestion of an occult relation between man and the vegetable. I am not alone and unacknowledged. They nod to me, and I to them.

 

Ralph Waldo Emerson

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Directionality and community‐level selection 

Guy Bunin, 2021.

Many ecological community dynamics display some degree of directionality, known as succession patterns. But complex interaction networks frequently tend to non‐directional dynamics such as chaos, unless additional structures or mechanisms impose some form of, often fragile or shot‐lived, directionality. We exhibit here a novel property of emergent long‐lasting directionality in competitive communities, which relies on very minimal assumptions.

We model communities where each species has a few strong competitive interactions, and many weak ones. We find that, at high enough diversity, the dynamics become directional, meaning that the community state can be characterized by a function that increases in time, which we call ‘maturity'. In the presence of noise, the community composition changes toward increasingly stable and productive states. This scenario occupies a middle ground between deterministic succession and purely random species associations: there are many overlapping stable states, with stochastic transitions, that are nevertheless biased in a particular direction. When a spatial dimension is added in the form of a meta‐community, higher‐maturity community states are able to expand in space, replacing others by (exact or approximate) copies of themselves. This leads to community‐level selection, with the same maturity function acting as fitness. Classic concepts from evolutionary dynamics provide a powerful analogy to understand this strictly ecological, community‐level phenomenon of emergent directionality.

https://onlinelibrary.wiley.com/doi/10.1111/oik.07214

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