Arthropod pests cause significant problems in agricultural crops all around the world. As chemical pesticide use becomes less desired, there is a need for alternative methods of pest control.... Show moreArthropod pests cause significant problems in agricultural crops all around the world. As chemical pesticide use becomes less desired, there is a need for alternative methods of pest control. Inspired by the natural adhesiveness of arthropod trapping plants, we examined the effectiveness of adhesive droplets made from oxidised and cross-linked plant-derived oils for control of western flower thrips. Two filter paper droplet adhesiveness assays and three detached chrysanthemum leaf assays were carried out to test efficacy against thrips. Suspensions containing adhesive droplets and other constituents were applied to filter papers and leaves via spraying or dipping. On filter papers, droplets made from oxidised rice germ oil (RGO) of different sizes caught 40–93% of thrips. Droplets made of a mixture of sunflower, olive, and linseed oil (MIX) caught up to 94% of thrips. Likewise, adhesive droplet-treated filter papers showed higher thrips mortality than untreated or control solution-treated filter papers. On chrysanthemum leaves, thrips were caught by both RGO (up to 40%) and MIX droplets (up to 20%) and thrips damage and reproduction were reduced. On MIX-treated leaves, thrips mortality was also increased. Within treatments, droplets of different size classes occurred and larger droplets were more effective at catching thrips in general. Droplets were also robust to rinsing with water, which is of importance for their application in horticulture. In conclusion, adhesive droplets made from edible plant oils show potential for use in control of western flower thrips. Show less
Purpose Insect herbivory affects plant growth, nutrient and secondary metabolite concentrations and litter quality. Changes to litter quality due to insect herbivory can alter decomposition, with... Show morePurpose Insect herbivory affects plant growth, nutrient and secondary metabolite concentrations and litter quality. Changes to litter quality due to insect herbivory can alter decomposition, with knock on effects for plant growth mediated through the plant-litter-soil feedback pathway. Methods Using a multi-phase glasshouse experiment, we tested how changes in shoot and root litter quality of fast- and slow-growing grass caused by insect herbivores affect the performance of response plants in the soil in which the litter decomposed. Results We found that insect herbivory resulted in marginal changes to litter quality and did not affect growth when plants were grown with fast- versus slow-growing litter. Overall, presence of litter resulted in reduced root and shoot growth and this effect was significantly more negative in shoots versus roots. However, this effect was minimal, with a loss of c. 1.4% and 3.1% dry weight biomass in roots versus shoots, respectively. Further, shoot litter exposed to insect herbivory interacted with response plant identity to affect root growth. Conclusions Our results suggest that whether litter originates from plant tissues exposed to insect herbivory or not and its interaction with fast- versus slow-growing grasses is of little importance, but species-specific responses to herbivory-conditioned litter can occur. Taken collectively, the overall role of the plant-litter-soil feedback pathway, as well as its interaction with insect herbivory, is unlikely to affect broader ecosystem processes in this system. Show less
1. Environmental conditions experienced by parent plants can influence offspring performance through parental effects induced by DNA methylation. The offspring can also be influenced by... Show more1. Environmental conditions experienced by parent plants can influence offspring performance through parental effects induced by DNA methylation. The offspring can also be influenced by environmental conditions experienced by their parents via soil legacy effects due to plant-mediated changes in the composition of soil microbes. These two effects are likely to act simultaneously, but empirical evidence for combined effects is limited.2. We conducted a two-phase experiment with five genotypes of a clonal plant Hydrocotyle vulgaris. In the first phase, we grew parent plants of each genotype under two light conditions (ambient vs. shade) and two DNA demethylation treatments (treated with water vs. 5-azacytidine). We then collected soils and clonal offspring for each genotype from each of these four treatments and measured soil (a)biotic properties. In the second phase, we grew the offspring from each of the four treatments in the four different soils, under the two light conditions.3. When grown under ambient light condition and in soil from ambient parents, offspring produced by ambient parents grew larger than offspring produced by shaded parents when the parents were treated with water. This difference was smaller when the parents were treated with 5-azacytidine, and disappeared when the offspring were grown in soil from shaded parents. The growth difference was also observed when the offspring were grown under shaded condition and in soil from shaded parents. However, this difference was greater when the parents were treated with 5-azacytidine, and disappeared when the offspring were grown in soil from ambient parents. Moreover, offspring growth was associated with fungal composition and total phosphorus of the soil in which the parents had grown.4. Our results show, for the first time, that light condition experienced by parents can influence offspring responses to light through both parental effects and soil legacies. The parental effects were mediated by changes in DNA methylation and the soil legacies were due to plant-mediated changes in a combination of soil biotic and abiotic properties. These impacts may eventually influence the ecological and evolutionary trajectories of clonal plant populations. Show less
Agricultural intensification has had long-lasting negative legacies largely because of excessive inputs of agrochemicals (e.g., fertilizers) and simplification of cropping systems (e.g., continuous... Show moreAgricultural intensification has had long-lasting negative legacies largely because of excessive inputs of agrochemicals (e.g., fertilizers) and simplification of cropping systems (e.g., continuous monocropping). Conventional agricultural management focuses on suppressing these negative legacies. However, there is now increasing attention for creating positive above- and belowground legacies through selecting crop species/genotypes, optimizing temporal and spatial crop combinations, improving nutrient inputs, developing intelligent fertilizers, and applying soil or microbiome inoculations. This can lead to enhanced yields and reduced pest and disease pressure in cropping systems, and can also mitigate greenhouse gas emissions and enhance carbon sequestration in soils. Strengthening positive legacies requires a deeper understanding of plant–soil–microbiome interactions and innovative crop, input, and soil management which can help toachieve agricultural sustainability. Show less
AimsSoil biotic communities can strongly impact plant performance. So far, most studies on plant-soil-interactions have estimated the effect of the soil microbial community on plant mass after a... Show moreAimsSoil biotic communities can strongly impact plant performance. So far, most studies on plant-soil-interactions have estimated the effect of the soil microbial community on plant mass after a fixed duration of plant growth. However, these interactions may change over time and several studies have argued that plant-soil interactions are more important for young seedlings than for older plants. In this paper we ask the question: how long-lasting the effect of the soil microbial community on plant growth is. This is important as the growth rate of a plant is not only determined by the growing conditions but also by the size of the plant itself. Therefore, plant with a reduced growth rate early in life, due to negative effects of the soil microbial community, may increase less in biomass for a much longer period even though the relative growth rates do not differ any longer.MethodsWe examined the plant growth rates at three stages: early growth (0-21 days), mid growth (22 to 42 days) and late growth (43 to 63 days). We performed two growth experiments with Jacobaea vulgaris lasting 49 and 63 days. Plants were grown in sterilized soil or in sterilized soil inoculated with natural dune soil. In a third experiment, we examined the effect of the timing of soil inoculation prior to planting on the (relative-) growth rate of J. vulgaris plants with four different timing treatments.Important findingsIn all experiments, differences in biomass of plants grown in sterilized soil and inoculated soil (live soil) increased throughout the experiment. Interestingly, linear regression models with ln transformed dry weight against time for younger plants and for older plants in sterilized soil and live soil, respectively, showed that the relative growth rate of plants in the sterilized soil was only significantly higher than that of plants in the live soil in the first two to three weeks. After that period there was no longer a negative effect of the live soil on the relative growth rate of plants. In the third experiment, plant biomass decreased with increasing time between inoculation and planting. Overall, our results show that plants of J. vulgaris grew less well in live soil than in sterilized soil. The negative effects of soil inoculation on plant mass appeared to extend over the whole growth period but arise from the negative effects on relative growth rates that occurred in the first weeks after planting when plants have only less than 5% of the mass they obtained after 42 days. Our study highlights the importance of examining relative growth rates rather than final biomass to estimate the effects of soil microbial communities on plants. Show less
Kuerban, M.; Cong, W.F.; Jing, J.; Bezemer, T.M. 2022
Background and aimsSoil legacies mediated by abiotic and biotic factors can greatly influence succeeding plants, a phenomenon called plant-soil feedback (PSF). To date, the patterns and mechanisms... Show moreBackground and aimsSoil legacies mediated by abiotic and biotic factors can greatly influence succeeding plants, a phenomenon called plant-soil feedback (PSF). To date, the patterns and mechanisms of PSF remain largely unexplored in agroecosystems, especially how soil microbial legacies of crop species and management practices interact is poorly understood.MethodsWe subjected four common arable crop species (wheat, maize, soybean and rapeseed) to water (sufficient or drought) and nitrogen (high or low) treatments to condition living soil. We analyzed soil nutrient properties and microbiome composition, and then grew the four crops in conspecific and heterospecific soils to examine intra- and inter-specific PSFs.ResultsWe found that crop species, nitrogen and water treatments created differential effects on soil bacteria and fungi diversity and community composition. Wheat grew better in conspecific-conditioned soil than in heterospecific-conditioned soil, whereas maize and soybean performed better in heterospecific-conditioned soils regardless of water and nitrogen treatments. The PSFs of rapeseed depended on the water and nitrogen treatments. The dissimilarity of both soil bacterial and fungal communities showed a consistently positive correlation with the feedback effect for wheat, while it negatively correlated for maize, rapeseed and soybean. Path analysis showed that soil abiotic, bacterial and fungal legacies all impacted the corresponding crop growth.ConclusionsWe show that via selecting crop species and by changing management practices we can create positive legacies that can enhance the growth of the succeeding crop. Hence, this work proposed a new way to capitalize on soil legacies for enhancing agricultural productivity. Show less
1. The importance of plant–soil feedbacks (PSF) for above-ground and below-ground multitrophic interactions is well recognized. However, most studies only condition soil for a short time before... Show more1. The importance of plant–soil feedbacks (PSF) for above-ground and below-ground multitrophic interactions is well recognized. However, most studies only condition soil for a short time before testing the feedback response. Here we investigate the influence of time of conditioning on soil microbiome composition, plant growth and metabolomics, and plant–insect interactions. We used soil collected from large outdoor mesocosms with monocultures of six species and investigated the temporal changes in the soil over a full year.2. Every 2 months, we assessed the legacy effects of the soils on plant growth of one of the species (Jacobaea vulgaris) in a climate-controlled chamber. Each time we used tissue culture plants that were genetically identical. We also measured leaf herbivore performance and leaf metabolomes, as well as the abiotic and biotic soil properties.3. We show that the monoculture soils harboured different microbiomes, but that these varied over time. Growth of the test plants also varied over time and plants grew consistently less well in their own soil. The soil legacy effects on the leaf metabolome were less consistent and varied strongly over time. Networking analysis showed that soil bacteria had stronger effects on the leaf metabolome than fungi early on. However, after 12 months of conditioning, only soil fungal community composition explained the metabolomic profiles of the leaves. Insect herbivory was not affected by soil conditioning, but decreased with increasing time of conditioning.4. Synthesis. Our results show that the biomass response of the test plants to soil conditioning remained consistent throughout the year, even though both the soil microbiome and leaf metabolomic responses to conditioned soil varied greatly over time. These soil-induced changes in the metabolome of plants over time can be an important driver of above-ground multitrophic interactions in nature. Our study demonstrates that the duration of conditioning has a strong impact on plant and soil properties, which highlights that temporal variation is an important aspect to consider in future studies investigating plant–soil interactions. Show less
Composts are commonly used as soil amendments to sustain and improve the functionality of agricultural soil. Compost has abiotic (organic matter [OM], nutrients) and biotic characteristics ... Show moreComposts are commonly used as soil amendments to sustain and improve the functionality of agricultural soil. Compost has abiotic (organic matter [OM], nutrients) and biotic characteristics (microorganisms) and both can influence the soil microbiome. The abiotic and biotic characteristics of compost, in turn, depend on properties of the compost such as maturity. Few studies have investigated the relative effects of abiotic and biotic components of compost on the soil microbial community and crop growth. To bridge this gap, we used a full-factorial design with sterile and live composts that differed in maturity (fresh, intermediate, mature) that were added to sterile and live soil to investigate the separate role of abiotic and biotic characteristics of composts on the resulting soil microbial community and on wheat growth. We found that the changes in the soil microbial community were mainly due to the input of compost with the presence of microorganisms rather than due to the abiotic properties of compost. The majority of the compost-associated microorganisms (more than 70% for bacteria and 90% for fungi) were detected in the soil in the presence of native soil microorganisms. Elimination of native soil microorganisms by sterilization enhanced the prevalence and abundance of compost-associated microorganisms. Adding fresh compost increased wheat biomass production, but the positive effects of compost on plant growth were strongest when sterile composts were used. Hence, our study reports that compost-associated microorganisms are essential to modify soil microbial community but may not benefit crop growth. This highlights the importance of understanding the role of abiotic and biotic properties of composts as common soil amendments on improving the functioning of agricultural soil. Show less
1. Plants leave legacy effects in the soil they grow in, which can drive important vegetation processes, including productivity, community dynamics and species turnover. Plants at the same time... Show more1. Plants leave legacy effects in the soil they grow in, which can drive important vegetation processes, including productivity, community dynamics and species turnover. Plants at the same time also face continuous pressure posed by insect herbivores. Given the intimate interactions between plants and herbivores in ecosystems, plant identity and herbivory are likely to interactively shape soil legacies. However, the mechanisms that drive such legacy effects on future generations of plants and associated herbivores are little known.2. In a greenhouse study, we exposed 10 common grasses and non-leguminous forbs individually to insect herbivory by two closely related noctuid caterpillars, Mamestra brassicae and Trichoplusia ni (Lepidoptera: Noctuidae) or kept them free of herbivores. We then used the soil legacies created by these plant individuals to grow a plant community composed of all 10 plant species in each soil and exposed these plant communities to M. brassicae. We measured conditioning plant biomass, soil respiration and chemistry of the conditioned soils, as well as individual plant, plant community and herbivore biomass responses.3. At the end of the conditioning phase, soils with herbivore legacies had higher soil respiration, but only significantly so for M. brassicae. Herbivore legacies had minimal impacts on community productivity. However, path models reveal that herbivore-induced soil legacies affected responding herbivores through changes in plant community shoot: root ratios. Soil legacy effect patterns differed between functional groups. We found strong plant species and functional group-specific effects on soil respiration parameters, which in turn led to plant community shifts in grass: forb biomass ratios. Soil legacies were negative for the growth of plants of the same functional group.4. Synthesis. We show that insect herbivory, plant species and their functional groups, all incur soil microbial responses that lead to subtle (herbivory) or strong (plants and their functional group) effects in response plant communities and associated polyphagous herbivores. Hence, even though typically ignored, our study emphasizes that legacies of previous insect herbivory in the soil can influence current soil–plant–insect community interactions. Show less
AimsPlants can influence the level of herbivory experienced by neighboring plants. The importance of such belowground associational effects are poorly understood. In this study we examine whether... Show moreAimsPlants can influence the level of herbivory experienced by neighboring plants. The importance of such belowground associational effects are poorly understood. In this study we examine whether Jacobaea vulgaris provides associational resistance against nematodes to neighboring plants.MethodsThirteen species (6 forbs, 3 grasses and 4 legumes) were each grown in mixtures with J. vulgaris and in monocultures. A nematode community was introduced to half of the pots. After 12 weeks, plant dry mass was assessed for each individual plant in each pot, and the number of nematodes in the soil and roots were identified. We then examined for each plant species its performance in mixtures and in monocultures, in presence and absence of nematodes and analyzed the abundance and composition of nematodes.ResultsForbs produced more, grasses similar, and legumes less biomass in mixtures with J. vulgaris than in monocultures. Nematode addition did not influence biomass. There were fewer root-feeding nematodes in the soil in mixtures than in monocultures, but this was only true for plants that were good hosts for nematodes. The community composition of soil nematodes was different in monocultures and mixtures. Densities of migratory endoparasitic nematodes in the roots of neighboring plants were lower in mixtures than in monocultures. Moreover, the presence of nematodes changed the outcome of plant-plant interactions, often in favor of J. vulgaris.ConclusionsJacobaea vulgaris provides belowground associational resistance to other plants against migratory endoparasitic nematodes, and the presence of nematodes can change the outcome of plant-plant interactions. Show less
