1
|
Fuchs B, Helander M, Saikkonen K, Dobrev PI, Vankova R, Blande JD, Salminen JP, Luntamo N, Muola A. Plant metabolic responses to soil herbicide residues differ under herbivory in two woodland strawberry genotypes. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 946:174198. [PMID: 38914330 DOI: 10.1016/j.scitotenv.2024.174198] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2024] [Revised: 06/18/2024] [Accepted: 06/20/2024] [Indexed: 06/26/2024]
Abstract
The use of glyphosate-based herbicides (GBHs) to control weeds has increased exponentially in recent decades, and their residues and degradation products have been found in soils across the globe. GBH residues in soil have been shown to affect plant physiology and specialised metabolite biosynthesis, which, in turn, may impact plant resistance to biotic stressors. In a greenhouse study, we investigated the interactive effects between soil GBH residues and herbivory on the performance, phytohormone concentrations, phenolic compound concentrations and volatile organic compound (VOC) emissions of two woodland strawberry (Fragaria vesca) genotypes, which were classified as herbivore resistant and herbivore susceptible. Plants were subjected to herbivory by strawberry leaf beetle (Galerucella tenella) larvae, and to GBH residues by growing in soil collected from a field site with GBH treatments twice a year over the past eight years. Soil GBH residues reduced the belowground biomass of the susceptible genotype and the aboveground biomass of both woodland strawberry genotypes. Herbivory increased the belowground biomass of the resistant genotype and the root-shoot ratio of both genotypes. At the metabolite level, herbivory induced the emission of several VOCs. Jasmonic acid, abscisic acid and auxin concentrations were induced by herbivory, in contrast to salicylic acid, which was only induced by herbivory in combination with soil GBH residues in the resistant genotype. The concentrations of phenolic compounds were higher in the resistant genotype compared to the susceptible genotype and were induced by soil GBH residues in the resistant genotype. Our results indicate that soil GBH residues can differentially affect plant performance, phytohormone concentrations and phenolic compound concentrations under herbivore attack, in a genotype-dependent manner. Soil GBH altered plant responses to herbivory, which may impact plant resistance traits and species interactions. With ongoing agrochemical pollution, we need to consider plant cultivars with better resistance to polluted soils while maintaining plant resilience under challenging environmental conditions.
Collapse
Affiliation(s)
- Benjamin Fuchs
- Biodiversity Unit, University of Turku, 20014 Turku, Finland.
| | - Marjo Helander
- Department of Biology, University of Turku, 20014 Turku, Finland
| | - Kari Saikkonen
- Biodiversity Unit, University of Turku, 20014 Turku, Finland
| | - Petre I Dobrev
- Laboratory of Hormonal Regulations in Plants, Institute of Experimental Botany of the Czech Academy of Sciences, Rozvojova 263, 16502 Prague, Czech Republic
| | - Radomira Vankova
- Laboratory of Hormonal Regulations in Plants, Institute of Experimental Botany of the Czech Academy of Sciences, Rozvojova 263, 16502 Prague, Czech Republic
| | - James D Blande
- Department of Environmental and Biological Sciences, University of Eastern Finland, P.O. Box 1627, 70211 Kuopio, Finland
| | - Juha-Pekka Salminen
- Natural Chemistry Research Group, Department of Chemistry, FI-20014, University of Turku, Finland
| | - Niko Luntamo
- Natural Chemistry Research Group, Department of Chemistry, FI-20014, University of Turku, Finland
| | - Anne Muola
- Biodiversity Unit, University of Turku, 20014 Turku, Finland; Division of Biotechnology and Plant Health, Norwegian Institute of Bioeconomy Research, Ås, Norway
| |
Collapse
|
2
|
Liu H, Li R, Hu W, Jian L, Huang B, Fan Y, Zhao Y, Zhang H, Khan KS. Multi-medium residues and ecological risk of herbicides in a typical agricultural watershed of the Mollisols region, Northeast China. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 937:173507. [PMID: 38797413 DOI: 10.1016/j.scitotenv.2024.173507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2024] [Revised: 05/18/2024] [Accepted: 05/23/2024] [Indexed: 05/29/2024]
Abstract
The widespread use of herbicides impacts non-target organisms, promotes weed resistance, posing a serious threat to the global goal of green production in agriculture. Although the herbicide residues have been widely reported in individual environmental medium, their presence across different media has received scant attention, particularly in Mollisols regions with intensive agricultural application of herbicides. A systematic investigation was conducted in this study to clarify the occurrence of herbicide residues in soil, surface water, sediments, and grains from a typical agricultural watershed in the Mollisols region of Northeast China. Concentrations of studied herbicides ranged from 0.30 to 463.49 μg/kg in soil, 0.31-29.73 μg/kg in sediments, 0.006-1.157 μg/L in water, and 0.32-2.83 μg/kg in grains. Among these, Clomazone was the most priority herbicide detected in soil, sediments, and water, and Pendimethalin in grains. Crop types significantly affected the residue levels of herbicides in grains. Clomazone posed high ecological risks in soil and water, with 86.4 % of water samples showing high risks from herbicide mixtures (RQ > 1). These findings aid in enhancing our comprehension of the pervasive occurrence and potential ecological risks of herbicides in different media within typical agricultural watersheds, providing detailed data to inform the development of targeted mitigation strategies.
Collapse
Affiliation(s)
- Hanqiang Liu
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Rui Li
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Wenyou Hu
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China; University of Chinese Academy of Sciences, Beijing 100049, China.
| | - Le Jian
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China; Sino-Danish College, University of Chinese Academy of Sciences, Beijing 101408, China
| | - Biao Huang
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China
| | - Ya'nan Fan
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China
| | - Yongcun Zhao
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Hongyan Zhang
- Innovation Center of Pesticide Research, Department of Applied Chemistry, College of Science, China Agricultural University, Beijing 100193, China
| | - Khalid Saifullah Khan
- Institute of Soil and Environmental Sciences, PMAS Arid Agriculture University, Rawalpindi 46300, Pakistan
| |
Collapse
|
3
|
Xie J, Yang J, Zhu S, Hou X, Chen H, Bai X, Zhang Z. Study on seed-borne cultivable bacterial diversity and antibiotic resistance of Poa pratensis L. Front Microbiol 2024; 15:1347760. [PMID: 38351918 PMCID: PMC10864108 DOI: 10.3389/fmicb.2024.1347760] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Accepted: 01/17/2024] [Indexed: 02/16/2024] Open
Abstract
In order to study the difference of cultivable seed-borne bacterial diversity between commercial varieties and wild species of Poa pratensis L., and their antibiotic resistance to sulfadiazine, tetracycline, oxytetracycline, ciprofloxacin, gentamicin, oxytetracycline and rifampin. In this study, 60 bacterium isolates were isolated by dilution-coated plate method. Through 16S rRNA sequence analysis, 40 representative isolates with different morphological characteristics were identified and phylogenetic tree was constructed. The results of diversity analysis showed that the seed-borne bacterial diversity of commercial varieties was richer than that of wild species. The antibiotic resistance of the isolated bacterial strains was studied by agar dilution method, and it was concluded that the antibiotic resistance of the seed-borne bacteria carried by commercial varieties was stronger than that of the wild species. Finally, the biofilm formation ability and swimming motility of the bacterial strain were measured, and the correlation between the two and the antibiotic resistance of the bacterial strain was analyzed. The analysis showed that the antibiotic resistance of bacterial strains in Poa pratensis L. was significantly correlated with their swimming motility. In addition, the swimming motility of the bacterial strains was significantly correlated with the biofilm formation ability. It is worth mentioning that this is the first time to study the drug-resistant bacteria distributed in the seed-borne bacteria of Poa pratensis L.
Collapse
Affiliation(s)
| | | | | | | | | | | | - Zhenfen Zhang
- Key Laboratory of Grassland Ecosystem, Ministry of Education, Ministry of Science and Technology, Pratacultural College, Gansu Agricultural University, Lanzhou, China
| |
Collapse
|
4
|
Fuchs B, Saikkonen K, Damerau A, Yang B, Helander M. Herbicide residues in soil decrease microbe-mediated plant protection. PLANT BIOLOGY (STUTTGART, GERMANY) 2023; 25:571-578. [PMID: 36920172 DOI: 10.1111/plb.13517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2022] [Accepted: 03/10/2023] [Indexed: 05/17/2023]
Abstract
The residues of glyphosate are found to remain in soils longer than previously reported, affecting rhizosphere microbes. This may adversely affect crop and other non-target plants because the plant's resilience and resistance largely rely on plant-associated microbes. Ubiquitous glyphosate residues in soil and how they impact mutualistic microbes inhabiting the aboveground plant parts are largely unexplored. We studied the effects of herbicide residues in soil on Epichloë sp., which are common endophytic symbionts inhabiting aerial parts of cool-season grasses. In this symbiosis, the obligate symbiont subsists entirely on its host plant, and in exchange, it provides alkaloids conferring resistance to herbivores for the host grass that invests little in its own chemical defence. We first show decreased growth of Epichloë endophytes in vitro when directly exposed to two concentrations of glyphosate or glyphosate-based herbicides. Second, we provide evidence for a reduction of Epichloë-derived, insect-toxic loline alkaloids in endophyte-symbiotic meadow fescue (F. pratensis) plants growing in soil with a glyphosate history. Plants were grown for 2 years in an open field site, and natural herbivore infestation was correlated with the glyphosate-mediated reduction of loline alkaloid concentrations. Our findings indicate that herbicides residing in soil not only affect rhizosphere microbiota but also aerial plant endophyte functionality, which emphasizes the destructive effects of glyphosate on plant symbiotic microbes, here with cascading effects on plant-pest insect interactions.
Collapse
Affiliation(s)
- B Fuchs
- Biodiversity Unit, University of Turku, Turku, Finland
| | - K Saikkonen
- Biodiversity Unit, University of Turku, Turku, Finland
| | - A Damerau
- Food Chemistry and Food Development, Department of Life Technologies, University of Turku, Turku, Finland
| | - B Yang
- Food Chemistry and Food Development, Department of Life Technologies, University of Turku, Turku, Finland
| | - M Helander
- Department of Biology, University of Turku, Turku, Finland
| |
Collapse
|
5
|
Mathew SA, Fuchs B, Nissinen R, Helander M, Puigbò P, Saikkonen K, Muola A. Glyphosate-based herbicide use affects individual microbial taxa in strawberry endosphere but not the microbial community composition. J Appl Microbiol 2023; 134:6987274. [PMID: 36639128 DOI: 10.1093/jambio/lxad006] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Revised: 11/30/2022] [Accepted: 01/12/2023] [Indexed: 01/15/2023]
Abstract
AIMS In a field study, the effects of treatments of glyphosate-based herbicides (GBHs) in soil, alone and in combination with phosphate fertilizer, were examined on the performance and endophytic microbiota of garden strawberry. METHODS AND RESULTS The root and leaf endophytic microbiota of garden strawberries grown in GBH-treated and untreated soil, with and without phosphate fertilizer, were analyzed. Next, bioinformatics analysis on the type of 5-enolpyruvylshikimate-3-phosphate synthase enzyme was conducted to assess the potential sensitivity of strawberry-associated bacteria and fungi to glyphosate, and to compare the results with field observations. GBH treatments altered the abundance and/or frequency of several operational taxonomic units (OTUs), especially those of root-associated fungi and bacteria. These changes were partly related to their sensitivity to glyphosate. Still, GBH treatments did not shape the overall community structure of strawberry microbiota or affect plant performance. Phosphate fertilizer increased the abundance of both glyphosate-resistant and glyphosate-sensitive bacterial OTUs, regardless of the GBH treatments. CONCLUSIONS These findings demonstrate that although the overall community structure of strawberry endophytic microbes is not affected by GBH use, some individual taxa are.
Collapse
Affiliation(s)
- Suni Anie Mathew
- Department of Biology, University of Turku, 20014 Turku, Finland
| | - Benjamin Fuchs
- Biodiversity Unit, University of Turku, 20014 Turku, Finland
| | - Riitta Nissinen
- Department of Biological and Environmental Science, University of Jyväskylä, 40014 Jyväskylä, Finland
| | - Marjo Helander
- Department of Biology, University of Turku, 20014 Turku, Finland
| | - Pere Puigbò
- Department of Biology, University of Turku, 20014 Turku, Finland.,Nutrition and Health Unit, Eurecat Technology Centre of Catalonia, 43204 Reus, Catalonia.,Department of Biochemistry and Biotechnology, Rovira i Virgili University, 43007 Tarragona, Catalonia
| | - Kari Saikkonen
- Biodiversity Unit, University of Turku, 20014 Turku, Finland
| | - Anne Muola
- Biodiversity Unit, University of Turku, 20014 Turku, Finland.,Division of Biotechnology and Plant Health, Norwegian Institute of Bioeconomy Research, 9016 Tromsø, Norway
| |
Collapse
|
6
|
Epichloë Endophytes Shape the Foliar Endophytic Fungal Microbiome and Alter the Auxin and Salicylic Acid Phytohormone Levels in Two Meadow Fescue Cultivars. J Fungi (Basel) 2023; 9:jof9010090. [PMID: 36675911 PMCID: PMC9861471 DOI: 10.3390/jof9010090] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Revised: 12/31/2022] [Accepted: 01/02/2023] [Indexed: 01/11/2023] Open
Abstract
Plants harbor a large diversity of endophytic microbes. Meadow fescue (Festuca pratensis) is a cool-season grass known for its symbiotic relationship with the systemic and vertically-via seeds-transmitted fungal endophyte Epichloë uncinata, yet its effects on plant hormones and the microbial community is largely unexplored. Here, we sequenced the endophytic bacterial and fungal communities in the leaves and roots, analyzing phytohormone concentrations and plant performance parameters in Epichloë-symbiotic (E+) and Epichloë-free (E-) individuals of two meadow fescue cultivars. The endophytic microbial community differed between leaf and root tissues independent of Epichloë symbiosis, while the fungal community was different in the leaves of Epichloë-symbiotic and Epichloë-free plants in both cultivars. At the same time, Epichloë symbiosis decreased salicylic acid and increased auxin concentrations in leaves. Epichloë-symbiotic plants showed higher biomass and higher seed mass at the end of the season. Our results demonstrate that Epichloë symbiosis alters the leaf fungal microbiota, which coincides with changes in phytohormone concentrations, indicating that Epichloë endophytes affect both plant immune responses and other fungal endophytes. Whether the effect of Epichloë endophytes on other fungal endophytes is connected to changes in phytohormone concentrations remains to be elucidated.
Collapse
|
7
|
Ruuskanen S, Fuchs B, Nissinen R, Puigbò P, Rainio M, Saikkonen K, Helander M. Ecosystem consequences of herbicides: the role of microbiome. Trends Ecol Evol 2023; 38:35-43. [PMID: 36243622 DOI: 10.1016/j.tree.2022.09.009] [Citation(s) in RCA: 25] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 09/13/2022] [Accepted: 09/16/2022] [Indexed: 12/14/2022]
Abstract
Non-target organisms are globally exposed to herbicides. While many herbicides - for example, glyphosate - were initially considered safe, increasing evidence demonstrates that they have profound effects on ecosystem functions via altered microbial communities. We provide a comprehensive framework on how herbicide residues may modulate ecosystem-level outcomes via alteration of microbiomes. The changes in soil microbiome are likely to influence key nutrient cycling and plant-soil processes. Herbicide-altered microbiome affects plant and animal performance and can influence trophic interactions such as herbivory and pollination. These changes are expected to lead to ecosystem and even evolutionary consequences for both microbes and hosts. Tackling the threats caused by agrochemicals to ecosystem functions and services requires tools and solutions based on a comprehensive understanding of microbe-mediated risks.
Collapse
Affiliation(s)
- Suvi Ruuskanen
- Department of Biological and Environmental Science, University of Jyväskylä, FI-40014 Jyväskylä, Finland; Department of Biology, University of Turku, FI-20014 Turku, Finland.
| | - Benjamin Fuchs
- Biodiversity Unit, University of Turku, FI-20014 Turku, Finland
| | - Riitta Nissinen
- Department of Biological and Environmental Science, University of Jyväskylä, FI-40014 Jyväskylä, Finland
| | - Pere Puigbò
- Department of Biology, University of Turku, FI-20014 Turku, Finland; Nutrition and Health Unit, Eurecat Technology Centre of Catalonia, Reus, Catalonia, Spain; Department of Biochemistry and Biotechnology, Rovira I Virgili University, Tarragona, Catalonia, Spain
| | - Miia Rainio
- Department of Biology, University of Turku, FI-20014 Turku, Finland
| | - Kari Saikkonen
- Biodiversity Unit, University of Turku, FI-20014 Turku, Finland
| | - Marjo Helander
- Department of Biology, University of Turku, FI-20014 Turku, Finland
| |
Collapse
|
8
|
Root biomass and cumulative yield increase with mowing height in Festuca pratensis irrespective of Epichloë symbiosis. Sci Rep 2022; 12:21556. [PMID: 36513732 PMCID: PMC9748035 DOI: 10.1038/s41598-022-25972-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Accepted: 12/07/2022] [Indexed: 12/15/2022] Open
Abstract
Increasing agricultural soil carbon sequestration without compromising the productivity of the land is a key challenge in global climate change mitigation. The carbon mitigation potential of grass-based agriculture is particularly high because grasslands represent 70% of the world's agricultural area. The root systems of grasses transfer large amounts of carbon to below-ground storage, and the carbon allocation to the roots is dependent on the grasses' photosynthesizing shoot biomass. In a common-garden experiment, Festuca pratensis was used as a model species to study how mowing and weed control practices of perennial cool-season fodder grasses affect total yield and root biomass. Additionally, grass-associated Epichloë endophytes and soil residual glyphosate were tested for their effect on the total yield and root biomass alone or in interaction with mowing. The results demonstrate that elevating the cutting height increases both cumulative yield and root biomass in F. pratensis. Endophyte symbiosis increased the total yield, while glyphosate-based herbicide residues in the soil decreased the root biomass, which indicates a reduction of soil bound carbon sequestration. The findings demonstrate that carbon sequestration and yield quantities on farmed grasslands may significantly be improved by optimizing strategies for the use of plant protection products and adjustment of mowing intensity.
Collapse
|
9
|
Fuchs B, Saikkonen K, Helander M, Tian Y, Yang B, Engström MT, Salminen JP, Muola A. Legacy of agrochemicals in the circular food economy: Glyphosate-based herbicides introduced via manure fertilizer affect the yield and biochemistry of perennial crop plants during the following year. CHEMOSPHERE 2022; 308:136366. [PMID: 36113650 DOI: 10.1016/j.chemosphere.2022.136366] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2022] [Revised: 08/23/2022] [Accepted: 09/04/2022] [Indexed: 06/15/2023]
Abstract
Conventional agricultural practices favoring the use of glyphosate-based herbicides (GBHs) increase the risk of GBH residues ending up in animal feed, feces, and, eventually, manure. The use of poultry manure as organic fertilizer in the circular food economy increases the unintentional introduction of GBH residues into horticultural and agricultural systems, with reportedly negative effects on the growth and reproduction of crop plants. To understand the potential lasting effects of exposure to GBH residues via organic manure fertilizers, we studied strawberry (Fragaria x vescana) plant performance, yield quantity, biochemistry, folivory, phytochemistry, and soil elemental composition the year after exposure to GBH. Although plants exposed to GBH residues via manure fertilizer were, on average, 23% smaller in the year of exposure, they were able to compensate for their growth during the following growing season. Interestingly, GBH residue exposure in the previous growing season led to a trend in altered plant size preferences of folivores during the following growing season. Furthermore, the plants that had been exposed to GBH residues in the previous growing season produced 20% heavier fruits with an altered composition of phenolic compounds compared to non-exposed plants. Our results indicate that GBHs introduced via manure fertilizer following circular economy practices in one year can have effects on perennial crop plants in the following year, although GBH residues in soil have largely vanished.
Collapse
Affiliation(s)
- Benjamin Fuchs
- Biodiversity Unit, University of Turku, FI-20014, Turku, Finland.
| | - Kari Saikkonen
- Biodiversity Unit, University of Turku, FI-20014, Turku, Finland
| | - Marjo Helander
- Department of Biology, University of Turku, FI-20014, Turku, Finland
| | - Ye Tian
- Food Sciences, Department of Life Technologies, University of Turku, FI-20014, Turku, Finland
| | - Baoru Yang
- Food Sciences, Department of Life Technologies, University of Turku, FI-20014, Turku, Finland
| | - Marica T Engström
- Natural Chemistry Research Group, Department of Chemistry, FI-20014, University of Turku, Finland
| | - Juha-Pekka Salminen
- Natural Chemistry Research Group, Department of Chemistry, FI-20014, University of Turku, Finland
| | - Anne Muola
- Biodiversity Unit, University of Turku, FI-20014, Turku, Finland; Division of Biotechnology and Plant Health, Norwegian Institute of Bioeconomy Research, Ås, Norway
| |
Collapse
|
10
|
Ramula S, Kalske A, Saikkonen K, Helander M. Glyphosate residues in soil can modify plant resistance to herbivores through changes in leaf quality. PLANT BIOLOGY (STUTTGART, GERMANY) 2022; 24:979-986. [PMID: 35793169 PMCID: PMC9796381 DOI: 10.1111/plb.13453] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Accepted: 06/27/2022] [Indexed: 05/28/2023]
Abstract
Glyphosate is the most widely used non-selective herbicide in the world. Glyphosate residues in soil can affect plant quality by modifying plant physiology, hormonal pathways and traits, with potential consequences for plants' interactions with herbivores. We explored these indirect effects in the context of plant-herbivore interactions in a perennial, nitrogen-fixing herb. We quantified leaf herbivory for glyphosate-exposed and control plants grown in phosphorus-fertilized and non-fertilized soils, and assessed the impacts of glyphosate treatment on traits related to plant resistance against herbivores (leaf trichome density, leaf mass per area) and performance (aboveground biomass, root:shoot ratio, nodule number, nodule activity). Moreover, we conducted a laboratory feeding experiment to compare the palatability of leaves from glyphosate-exposed and control plants to a generalist mollusc herbivore. Herbivore damage and intensity in situ increased during the growing season regardless of glyphosate or phosphorus treatment. Glyphosate treatment reduced leaf trichome density but had no effect on the other plant traits considered. Herbivore damage was negatively associated with leaf trichome density. The feeding experiment revealed no difference in the feeding probability of mollusc herbivores between glyphosate-exposed and control plants. However, there was an interaction between glyphosate treatment and initial leaf area for leaf consumption by herbivores: leaf consumption increased with increasing leaf area in both groups, but at a lower rate for glyphosate-exposed plants than for control plants. Our results show that glyphosate residues in soil have the potential to indirectly affect aboveground herbivores through changes in leaf quality, which may have mixed consequences for folivore damage.
Collapse
Affiliation(s)
- S. Ramula
- Department of BiologyUniversity of TurkuTurkuFinland
| | - A. Kalske
- Department of BiologyUniversity of TurkuTurkuFinland
| | - K. Saikkonen
- Biodiversity UnitUniversity of TurkuTurkuFinland
| | - M. Helander
- Department of BiologyUniversity of TurkuTurkuFinland
| |
Collapse
|