Soil microorganisms and their role in the interactions between weeds and crops (original) (raw)
Related papers
Arbuscular mycorrhizal fungi shift competitive relationships among crop and weed species
Plant and Soil, 2011
Aims Arbuscular mycorrhizal (AM) symbioses affect plant competitive relationships within and among species and may be involved in the interactions among agricultural weed species and crops, depending on their mycorrhizal status. In this work, the impact of native AM fungi (AMF) on maize-weed(s) and weed-weed competitive relationships was assessed, using Solanum nigrum and Chenopodium album as model host and non-host weeds, respectively. Methods Growth performance, nutrient use and competitive ability of crop and weed species were assessed in the pure stand and in different model plant communities of host and non-host species. Results Results showed that maize performance decrease was more severe when grown with C. album than with S. nigrum. Differential responses to AMF occurred in the two weed species tested: mycorrhizal S. nigrum showed reduced biomass and N uptake when grown in competition with C. album. The negative performances observed when mycorrhizal S. nigrum grew in competition with C. album corresponded to C. album larger biomass production and N uptake. Conclusions Results showed that AMF are able to alter the competitive relationships between cooccurring plant species differing in their mycorrhizal status (host/non-host), thus representing key soil organisms to be taken into account in sustainable weed management strategies.
Mycorrhizal fungi suppress aggressive agricultural weeds
Plant and soil, 2010
Plant growth responses to arbuscular mycorrhizal fungi (AMF) are highly variable, ranging from mutualism in a wide range of plants, to antagonism in some non-mycorrhizal plant species and plants characteristic of disturbed environments. Many agricultural weeds are non mycorrhizal or originate from ruderal environments where AMF are rare or absent. This led us to hypothesize that AMF may suppress weed growth, a mycorrhizal attribute which has hardly been considered. We investigated the impact of AMF and AMF diversity (three versus one AMF taxon) on weed growth in experimental microcosms where a crop (sunflower) was grown together with six widespread weed species. The presence of AMF reduced total weed biomass with 47% in microcosms where weeds were grown together with sunflower and with 25% in microcosms where weeds were grown alone. The biomass of two out of six weed species was significantly reduced by AMF (−66% & −59%) while the biomass of the four remaining weed species was only slightly reduced (−20% to −37%). Sunflower productivity was not influenced by AMF or AMF diversity. However, sunflower benefitted from AMF via enhanced phosphorus nutrition. The results indicate that the stimulation of arbuscular mycorrhizal fungi in agro-ecosystems may suppress some aggressive weeds.
Applied Soil Ecology, 2000
Arbuscular mycorrhizal fungi (AMF) and rhizobacteria (Pseudomonas fluorescens) have been targeted for plant growth promotion in order to reduce agrochemical inputs. However, the effects of their interaction on root morphology under different nutrient levels are unknown. Moreover, both soil microorganisms can alter the levels of plant hormonal regulators but no in vivo evidence is available for their interplay with cytokinin (CK) on root morphology. In a full-factorial greenhouse experiment we investigated the effects of interaction between Rhizophagus intraradices, P. fluorescens 8569r, phosphorus (P) amendment and plant CK deficiency on tobacco root morphology, shoot yield and quality. Our results suggest that reduced CK levels may be involved in plant signaling to stimulate AMF hyphal growth in the roots. In addition, we document that a bacteria isolated from the rhizosphere of a non-mycorrhizal plant can function as mycorrhizal helper bacteria, most likely via interplay with phytohormones. The two soil microorganisms, depending on the inoculum combination, P amendment and plant CK levels, modified tobacco root morphology. Our results suggest that the positive interactions between P. fluorescens and AMF depend on soil nutrient status and root hormonal balance. Both microorganism modified shoot yield and these effects seem to result from altered root morphology. Overall, our study support early conclusions that the classification of a soil microorganism as detrimental or beneficial should be based upon their net effects on the plant growth according to circumstances. We suggest this consideration to be extended to the effects of interaction between soil microorganisms on root morphology.
Can Arbuscular Mycorrhizal Fungi Reduce the Growth of Agricultural Weeds?
PLoS ONE, 2011
Background: Arbuscular mycorrhizal fungi (AMF) are known for their beneficial effects on plants. However, there is increasing evidence that some ruderal plants, including several agricultural weeds, respond negatively to AMF colonization. Here, we investigated the effect of AMF on the growth of individual weed species and on weed-crop interactions.
Effect of soil tillage on arbuscular mycorrhizal fungi and on their role in nutrient uptake by crops
2002
Zusammenfassung Résumé 1. General introduction 2. Literature review 3. Objective, hypotheses and approaches 4. Effect of soil tillage on plant growth, nutrient acquisition and root colonisation by AMF 5. Effect of soil tillage on the community of AMF within maize roots 6. Effects of AMF from differently tilled soils on plant growth and nutrient acquisition in pots with a single compartment 7. Strategies of soil exploration by AMF from genus Glomus 8. Uptake and transport of P and Zn by Glomus intraradices Schenck & Smith growing in symbiosis with maize 9. General discussion and conclusions 10. Future perspectives 11. References 2.1.2. AMF diversity About 130-160 species of AMF have been described based on the morphology of their spores so far (Walker and Trappe 1993, Giovannetti and Gianinazzi-Pearson 1994, Morton and Bentivenga 1994). The other AMF structures (mycelium, arbuscules, and vesicles) are morphologically very conserved and provide very limited number of characters useful for taxonomy (Morton and Bentivenga 1994). Some AMF species might preferentially establish symbiotic relationships with certain plant species (such as Acaulospora sp. preferentially establishing symbiosis with Allium sp. or Glomus sp. with Plantago sp.) (Bever et al. 1996). No clear evidence for absolute (species to species) specificity has been yet recognised (Vanderplank 1978, Smith and Read 1997). However, the processes controlling the recognition between the plant and the AMF partner in the arbuscular mycorrhizal symbiosis and the factors involved in this interaction are still poorly known (
AMF has considerable influence on plant nutrition uptake, competition between the legume (Trifolium incarnatum) and a grass (Anthoxanthum odoratum) is influenced by the presence of Arbuscular Mycorrhizal Fungi (AMF) in this study. AMF has the ability to change the nutrient distribution between plants which may lead to changes in competitive relationships in plant communities. Pot experiments with a replacement design were conducted to test the influence of AMF isolates and a non AMF control on the competitive relationships of those plant pairs. Key consideration for the study was AMF influence on growth of legume and grass plants when grown individually or in combination of two plants and measured by the dry weight of biomass. Results revealed that AMF stimulates the plant growth of legume and negative effect on grass plant; number of root nodules of legume plant has positive effect in monoculture & mixture. While in competition, legume plant increased biomass in absence of AMF but the relative yield of the grass plant decreased or remains equal and AMF affects the competitive relationship between legume and grass plant.
Soil Microbes and their interaction with plants
This chapter will look forward at different types of microorganism’s interaction with Plants. It will also discuss the effects which will arise after the interaction of microbes with plants. Plant-Microbe Interactions Encounters between plant cells and both ‘friendly’ and ‘hostile’ microbes (such as those in symbiotic and pathogenic interactions, respectively) trigger a range of highly dynamic plant cellular responses. Densely colonized soil contains beneficial mycorrhizal fungi and rhizobia, which associate with roots and provide plants with mineral nutrients and fixed nitrogen, respectively, in exchange for carbon. By contrast, plants are constantly exposed to a range of fungal, bacterial and viral pathogens, and have evolved unique defense mechanisms to fight these infections. These include reorganization of the cytoskeleton, organelle translocation, vesicle trafficking, and alterations in subcellular protein localization. Recent progress in this border-land that bridges the fields of plant–microbe interactions and cell biology heralds the transition from descriptive phenomenology to the identification and characterization of key molecules that are involved in these processes. Intriguingly, molecular events that occur in plant cells in response to microbes also take place upon abiotic wounding and during fundamental plant developmental processes, such as the tip growth of pollen, root hairs and trichomes. Thus, elementary ‘activity modules’ that are required for the generation of cell polarity in plant morphogenesis appear to be re-used in both abiotic and biotic stress response pathways.
Mycorrhizal fungal identity and diversity relaxes plant–plant competition
Ecology, 2011
There is a great interest in ecology in understanding the role of soil microbial diversity for plant productivity and coexistence. Recent research has shown increases in species richness of mutualistic soil fungi, the arbuscular mycorrhizal fungi (AMF), to be related to increases in aboveground productivity of plant communities. However, the impact of AMF richness on plant-plant interactions has not been determined. Moreover, it is unknown whether species-rich AMF communities can act as insurance to maintain productivity in a fluctuating environment (e.g., upon changing soil conditions).
Soil microorganisms commonly named biofertilizers can be used to decrease input of fertilizers, pesticides and other chemicals in Agriculture. Among soil microorganisms, arbuscular mycorrhizal (AM) fungi and Rhizobium spp. can promote plant growth and control plant fungal diseases. However these microorganisms are not yet used in commercial biocontrol products. Integration of Arbuscular Mycorrhizal Fungi with Rhizobium sp. thus appears to be a promising approach for sustainable agriculture especially in legume crops where the net influence of this combination is supposed to be very high compare to other types of crop families. Arbuscular Mycorrhizal fungi and root-nodule bacterium Rhizobium are two root symbionts. Arbuscular mycorrhizal fungi increases soil nutrients and water absorption, while root-nodule bacteria fix atmospheric nitrogen and produce antibiotics and phytoalexins. These microbes modify the quality and abundance of rhizosphere microflora and alter overall microbial activity of the rhizosphere. They induce changes in the host root exudation pattern. A procedure for successful development of these microorganisms is required by selection and screening of efficient isolates. Knowledge of culture systems that are adapted to their establishment and multiplication is needed. Arbuscular mycorrhizal fungi provide specific niches for bacteria. Arbuscular mycorrhizal bacteria improve nutrient acquisition in plants and subsequently, growth of the particular crops is advantaged indeed. Arbuscular mycorrhizal bacteria may contribute to ability of arbuscular mycorrhizal fungi to inhibit pathogens acquire mineral nutrients and modify plant root growth. Combined use of these microorganisms is more beneficial than their use alone. Together, they Influence plant root morphology changes and chemical properties of Rhizospheric soils of high plants with the significant extent. These symbionts also interact with other beneficial microorganisms synergistically and can be exploited for sustainable agriculture. The sound influence of these symbionts on root morphology and growth of the whole crop as well as on soil properties interested many researchers in agriculture domain.