Natural selection

Paul Nurse

Application of microbial inoculants significantly  enhances crop productivity: A meta-analysis of studies from 2010 to 2020

Li et al, 2022

Abstract

Introduction

With the rapid development of microbial technology, microbial inoculant is considered as a promising tool in sustainable agricultural systems. Mechanisms by which microbial inoculants improve crop yield include improving plant nutrient availability and alleviating abiotic/biotic stresses (e.g., drought, salt and disease). However, the field efficacy of microbial inoculants remains inconsistent, which constrains large-scale adoptions. Identity of dominant mechanisms that underpin the positive impacts of different microbial inoculants is limited. Thus, a comprehensive quantitative assessment of known inoculants on crop performance is needed to provide guidance for the development of effective microbial tools from both research and commercial perspectives.

Materials and Methods

Based on 97 peer-reviewed publications, we conducted a meta-analysis to quantify the benefits of different microbial inoculants on crop yield, and to identify the key mechanisms that underpin enhanced crop yield.

Results

Result showed that (i) alleviation of stresses was the major mechanism (53.95%, n = 53) by which microbial inoculants enhance crop yield, while improving plant nutrient availability accounted for 22.25% (n = 58) of crop yield enhancement. (ii) Pseudomonas was the most effective microbial inoculant in enhancing crop yield through alleviating stresses (63.91%, n = 15), whereas Enterobacter was the most effective in improving plant nutrient availability (27.12%, n = 5). (iii) Considering both mechanisms together, Pseudomonas (49.94%, n = 21), Enterobacter (27.55%, n = 13) and Bacillus (25.66%, n = 32) were the largest sources of microbial inoculants to enhance crop yield, and the combination of diazotroph Burkholderia with its legume host had the highest effect on improving the yield (by 196.38%). Microbial inoculants also improve nutritional quality by enhancing mineral contents in the produce.

Conclusion

Our analysis provides evidence that microbial inoculants can enhance agricultural productivity and nutritional quality and can be used either alone or in combination with reduced amount of agrochemicals to promote sustainable agriculture.

https://onlinelibrary.wiley.com/doi/full/10.1002/sae2.12028

Revisiting the cry-for-help hypothesis in plant–microbe interactions

Tharp et al., 2025

The ‘cry-for-help hypothesis’ (CHH) is broadly used to study how root exudate modulation under stress influences recruitment of beneficial microbes in the rhizosphere. Here, we explored common misconceptions and limitations of the CHH and advocate for the reassessment of this prevalent hypothesis to unfold the ecological complexities of plant–microbe interactions.

https://www.cell.com/trends/plant-science/abstract/S1360-1385(25)00223-7

Linalool-triggered plant-soil feedback drives defense adaptation in dense maize plantings

Guo et al., 2025

Structured Abstract

INTRODUCTION

Planting crops more densely increases overall yields, but it also raises the risk of pest and pathogen outbreaks. Although plants can modify their architecture to adapt to crowded conditions, how they adjust their immune responses remains largely unknown. Understanding how plants manage these trade-offs is critical for sustainable agriculture, especially in the context of increasing global food demands.

RATIONALE

Plants release chemical cues, such as volatiles, that inform neighbors of environmental conditions. One such compound, linalool, is a constitutively emitted leaf volatile in maize and other grasses. We hypothesized that linalool could act as a signal in densely planted fields, triggering plant-soil feedback that prepares neighboring plants for potential biotic stress. We explored how linalool shapes root signaling, soil microbiota, and ultimately plant defense and growth.

RESULTS

Field surveys revealed that maize plants in the inner rows of densely planted fields suffered less herbivore damage than those at the edges but that they also had reduced growth. Laboratory soil–transplantation experiments confirmed that soils conditioned by high-density plantings decreased plant biomass while enhancing resistance to insects, nematodes, and pathogens. These effects extended across genotypes and species.

Volatile profiling identified linalool as a key compound increasing with planting density. Exposure of maize to synthetic linalool reproduced the feedback effects, which required the presence of a living plant. Mechanistically, linalool activated jasmonate signaling in roots and up-regulated genes that drive the biosynthesis and exudation of the specialized metabolite HDMBOA-Glc. This exudate reshaped the rhizosphere microbiome, selectively enriching bacteria that suppressed plant growth but increased resistance in subsequently grown plants. Soil sterilization and microbial inoculation confirmed that these microbes were essential for the feedback loop.

In plants grown in linalool-conditioned soil, defense-related signaling, particularly salicylic acid signaling, was up-regulated, whereas growth-promoting metabolic pathways were down-regulated. Plants lacking salicylic acid signaling did not show growth-defense trade-offs, confirming salicylic acid’s role in expressing the feedback-triggered defense.

CONCLUSION

This study uncovers a volatile-triggered feedback mechanism through which maize adapts its defense in crowded environments. The constitutive emission of linalool primes neighboring plants by activating root jasmonate signaling, promoting HDMBOA-Glc exudation, and altering the rhizosphere microbiome. This, in turn, leads to elevated defense and suppressed growth in subsequent plants through salicylic acid signaling. These findings shed light on how plants integrate aboveground cues and belowground processes to optimize defense in high-density settings. Harnessing this natural defense pathway through breeding, microbial inoculants, or synthetic biology could enable the development of crops that are more resilient and require fewer chemical inputs.

https://www.science.org/doi/10.1126/science.adv6675

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Cornell Lab of Ornithology

Law of complexity  

Robert Hazen and Michael Wong

Plant sap analysis

Joel Williams

Maximum Entropy is a Foundation for Complexity Science

John Harte

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