Abstract Arbuscular Mycorrhizal Fungi Colonization Research Articles

Low indigenous AM fungal activity would be a necessary but not sufficient condition for effective utilization of exogenous AM fungal inoculum to forage corn

ABSTRACT Arbuscular mycorrhizal (AM) fungi is expected to be utilized in low input agriculture for their function to supply nutrients and water to host plants. AM fungal inoculum has been provided, but it has been known that their effect is context dependent. To clarify the factors that determine the effect of AM fungal inoculation to forage corn, a pot experiment was conducted using different indigenous AM fungal infection potential that evaluated with a modified infection unit method. Because we hypothesized that low indigenous AM fungal infection potential would be required to obtain significant inoculation effect, we prepared soils with different indigenous AM fungal infection potential by mixing sterile and non-sterile soils with different ratio. AM fungal colonization of non-inoculated series were increased with increase of indigenous AM fungal infection potential. Inoculation effect to increase of AM fungal colonization to corn root was generally larger in soils with low indigenous AM fungal infection potential and with low phosphorus (P) level, however, the effect was not very prominent in the soil with moderate P levels. Plant growth and plant P uptake showed similar trend with AM fungal colonization, i.e., enhanced P uptake and increase in plant dry matter were obtained when change in AM fungal colonization was larger. Therefore, low indigenous AM fungal infection potential would be required but not a sufficient condition to obtain AM fungal inoculation effect to forage corn.

Mycorrhizal colonization in bread wheat varieties differing in their response to phosphorus

Arbuscular mycorrhizal fungi (AMF) play an important role in phosphorus (P) nutrition of plants. Varietal differences in AMF infection occur but there is limited information on the importance of these differences to P efficiency in wheat. This work was conducted to determine whether variation in AMF infection could help explain genetic differences in responses to P. Ten wheat varieties that vary in their grain yield response to P were compared at different rates of P in two controlled environment experiments. Plant samples were also collected from a field experiment with two P rates. Significant genetic variation was observed for AMF colonization in all experiments, but these differences were not consistently related to the yield responsiveness to P among the ten varieties. Two varieties, Carazinho and RAC875 that have a low yield response to P, had consistently high root colonization while a P-responsive variety, Wyalkatchem, had low root colonization. Adding P fertilizer reduced AMF colonization and at high P rates negative associations between AMF colonization and seedling growth and P uptake were observed among the varieties. Among some varieties, their grain yield response to P and P efficiency were consistent with their AMF colonization. However, the negative effect of mycorrhizal infection on seedling growth at high soil P suggests AMF colonization may only be a suitable trait for improved P efficiency in farming systems where available P is consistently low.

Arbuscular mycorrhizal colonization of selected herbaceous plants under arid protected area in Tunisia

ABSTRACT Arbuscular mycorrhizal fungi (AMF) play an important role in plants growth and soils dynamic in all most ecosystems. The main objective of the present study was to evaluate the plant-AMF interactions on soil functions under arid protected area ‘Zarat-Gabès’ in Tunisia. AMF colonization was evaluated by visual observation of AMF in fine roots of eight herbaceous plants. The level of mycorrhizal colonization varied between plants. Astragalus corrugatus and Hippocrepis areolata showed the highest mycorrhizal performance. The relative spore number was significantly different across rhizosphere soils. Statistical analysis showed a clearly positive correlation between the number of spores and plant-mycorrhizal intensity. For microbiological parameters, our results showed that mycorrhizal plants improved significantly the various microbiological parameters. Rhizosphere soils of Astragalus corrugatus and Hippocrepis areolata presented the necessary microbial densities and microorganisms more stable compared to unplanted soil. This study allowed obtaining a new result that challenges us about the need for efficient management of natural resources in the objective of nature conservation.

Arbuscular mycorrhizal fungal communities associated with two dominant species differ in their responses to long‐term nitrogen addition in temperate grasslands

Abstract Arbuscular mycorrhizal (AM) fungi are important components of grassland ecosystems and are sensitive to enhanced atmospheric nitrogen (N) deposition. Enhanced N deposition has been widely reported to reduce species richness and alter species composition across different types of grasslands world‐wide. Despite extensive studies on effects of N deposition on AM fungal communities of grasslands, few studies have specifically focused on effects of N deposition on AM fungi associated with dominant species in grasslands. We investigated long‐term (12‐year) effects of N addition (80 kg ha−1 year−1) on AM fungal community richness in roots and rhizosphere biomass of two dominant plant species (forb Artemisia frigida and grass Stipa krylovii) in temperate steppes of northern China. We found that AM fungi associated with the two dominant plant species differed in their responses to N addition. Nitrogen addition led to a significant reduction in AM fungal richness colonized in roots, and biomass in the rhizosphere of A. frigida, while N addition had little impacts on AM fungi colonized in roots and rhizosphere of S. krylovii. Nitrogen addition significantly reduced AM fungal colonization in roots and AM fungal spore density in the rhizosphere soils of A. frigida. In contrast, N addition had no effect on AM fungal colonization in roots and spore density in the rhizosphere of S. krylovii. Nitrogen addition markedly suppressed photosynthetic rates in A. frigida due to excessive foliar accumulation of manganese. The N‐induced reduction in photosynthetic rates reduced allocation of C into roots in A. frigida, leading to a lower root/shoot ratio, and suppression of AM fungal community associated with A. frigida. The inhibition of AM fungi would render A. frigida less competitive in terms of acquisition of mineral nutrients in soils, thus contributing to its loss in the steppe community under conditions of elevated N deposition. These findings provide a mechanistic explanation for N‐evoked differential responses of AM fungal communities associated with A. frigida and S. krylovii by linking soil properties and host plants to AM fungal communities. A plain language summary is available for this article.

In Winter Wheat, No-Till Increases Mycorrhizal Colonization thus Reducing the Need for Nitrogen Fertilization

Arbuscular mycorrhizal fungi (AMF) play a major role in the uptake of nutrients by agricultural plants. Nevertheless, some agricultural practices can interrupt fungal-plant signaling and thus impede the establishment of the mycorrhizal symbiosis. A field experiment performed over a 5-year period demonstrated that both the absence of tillage and of nitrogen (N) fertilization improved AMF colonization of wheat roots. Moreover, under no-till conditions, N uptake and aboveground biomass production did not vary significantly between N-fertilized and N-unfertilized plots. In contrast, both N uptake and above ground biomass were much lower when N fertilizer was not added during conventional tillage. This finding strongly suggests that for wheat, no-till farming is a sustainable agricultural system that allows a gradual reduction in N fertilizer use by promoting AMF functionality and at the same time increasing N uptake.

The effects of arbuscular mycorrhizal fungal inoculation at a roadside prairie restoration site

Arbuscular mycorrhizal fungi (AMF) may play an important role in ecological succession, but few studies have documented the effectiveness of mycorrhizal inoculation at restoration/reclamation sites. At a roadside prairie restoration in Shakopee, Minnesota, we compared AMF root colonization and resulting vegetative cover among four inoculation treatments. After 15 mo of growth, we found that AMF colonization was high in all treatments but was significantly higher in treatments that received AMF inoculum propagated from a local prairie site or commercially available inoculum than the uninoculated control. For the prairie inoculum, this increase in colonization occurred whether the inoculum was applied with seeds in furrows or broadcast with seeds on the soil surface. However, increased colonization did not discernibly affect the restored vegetation; neither total vegetative cover nor the proportion “desired” prairie vegetation differed among inoculation treatments. By the end of the third growing season (27 mo after planting) there were no longer differences in AMF colonization among the inoculation treatments nor were there differences in vegetative cover. It is likely that natural recolonization of the plots by remnant AMF populations at the site limited the duration of the inoculation effect. This natural recolonization, in combination with relatively high soil phosphorus levels, likely rendered inoculation unnecessary. In contrast to previous published studies of AMF inoculation in landscape restorations, this study shows that AMF inoculation may not be warranted under some circumstances.