Search Results (4)

Many studies describe the positive effect of mycorrhiza, but few report on negative effects. Furthermore, there is a research gap on the mechanisms under which conditions the symbiotic mycorrhizal plant interaction or a parasitic one predominates. The study was conducted as a field experiment over three years to investigate the effect of mycorrhiza (Rhizoglomus intraradices) and soil bacteria applications on fertile soil. A standard fertilizer (diammonium phosphate) and two microgranular fertilizers (mineral and organomineral) were applied alone or in combination with the biostimulants mycorrhiza and/or soil bacteria (Bacillus velezensis). The application of the mycorrhiza as the only biostimulant resulted in lower yields compared to all fertilizer variants without the mycorrhiza or with mycorrhiza in combination with soil bacteria in the dry years 2015 (p = 0.0241) and 2016 (p = 0.0003). The usage of soil bacteria alone, or soil bacteria with fertilizer, resulted in few occasional significant differences. The combination with soil bacteria raised the yield of mycorrhiza-treated fertilizer variants to a significant extent in 2015 (p = 0.0007) and 2016 (p = 0.0019). The negative effects of mycorrhiza application in this study were alleviated by the simultaneous use of soil bacteria. Treatments with organomineral microgranular fertilizer, which were expected to promote the naturally occurring soil microbiome more than the mineral fertilizer variants, were most negatively affected by the mycorrhiza. We hypothesize that the naturally occurring microbiome of the study site was already optimal for maize plants, and thus the successful introduction of other microorganisms through the application of the mycorrhiza and soil bacteria tended not to be beneficial. The present study is the first report on the negative influence of arbuscular mycorrhiza on maize yields gained with a standard fertilizer (diammonium phosphate) and two microgranular fertilizer, and the alleviation of that impact by combined application of soil bacteria. We conclude that the application of the used biostimulants may have negative impacts on maize yield if the soil is already rich in nutrients and water is the limiting factor. Full article

Arbuscular mycorrhizal fungi (AMF) confer positive and negative effects on many plants, but it is unclear whether AMF has an effect on soil fertility, aggregate distribution, and stability. The aim of this study was to analyze the effects of Rhizoglomus intraradices on plant growth, root morphology, leaf chlorophyll and gas exchange, sugar concentrations, and soil nutrients, aggregate distribution, and stability in marigold (Tagetes erecta L.), maize (Zea mays L.), white clover (Trifolium repens L.), and vetch (Vicia villosa Roth.) plants. Twelve weeks after R. intraradices inoculation, maize presented the highest mycorrhizal development, while mycorrhizal dependence was shown to be the decreasing trend in marigold > white clover > vetch > maize. AMF inoculation significantly increased the chlorophyll index of marigold and white clover, the net photosynthetic rate of white clover, the stomatal conductance of maize and white clover, and the transpiration rate of maize. Fructose, glucose, and sucrose in the four plants were differentially affected by R. intraradices. R. intraradices significantly increased the soil organic carbon (SOC) of marigold, maize, and white clover, the Olsen-P of white clover, the available K content of marigold, the easily extractable glomalin-related soil protein (GRSP) of maize, and the difficultly extractable and total GRSP levels of marigold and vetch. In addition, R. intraradices significantly increased the stability of soil water-stable aggregates (WSAs) in all four plants, plus it increased WSA at 0.5–4 mm sizes. Root AMF colonization was significantly positively correlated with WSA stability, SOC, difficultly extractable GRSP, and total GRSP. It is concluded that AMF-triggered changes in plant growth, physiological activities, and soil fertility depended on plant species, but AMF-improved WSA distribution and stability were not dependent on plant species. Full article

Symbiotic associations with arbuscular mycorrhizal fungi (AMF) offer an effective indirect mechanism to reduce heavy metal (HM) stress; however, it is still not clear which AMF species are more efficient as bioremediating agents. We selected different species of AMF: Rhizoglomus custos (Custos); Rhizoglomus sp. (Aznalcollar); and Rhizophagus irregularis (Intraradices), in order to study their inoculation in wheat grown in two soils contaminated with two levels of HMs; we tested the phytoprotection potential of the different AMF symbioses, as well as the physiological responses of the plants to HM stress. Plants inoculated with indigenous Aznalcollar fungus exhibited higher levels of accumulation, mainly in the shoots of most of the HM analyzed in heavily contaminated soil. However, the plants inoculated with the non-indigenous Custos and Intraradices showed depletion of some of the HM. In the less-contaminated soil, the Custos and Intraradices fungi exhibited the greatest bioaccumulation capacity. Interestingly, soil enzymatic activity and the enzymatic antioxidant systems of the plant increased in all AMF treatments tested in the soils with both degrees of contamination. Our results highlight the different AMF strategies with similar effectiveness, whereby Aznalcollar improves phytoremediation, while both Custos and Intraradices enhance the bioprotection of wheat in HM-contaminated environments. Full article

The agricultural use of arbuscular mycorrhizal fungi, such as Rhizoglomus intraradices, can increase the efficiency of phosphate fertilization for the benefit of the corn plant and grain nutrition. In this study, a field experiment was conducted in an area of Selvíria/MS, Brazil, in the years 2019 and 2020, to verify the effects of reduced doses of phosphorus combined with the inoculation of corn seed with R. intraradices on corn plant growth and grain nutrient contents. The experiment was laid in a randomized block design in subdivided plots with four repetitions and twenty treatments resulting from combining five doses of P₂O₅ (0%, 25%, 50%, 75%, and 100% of the recommended dose) with four doses (0, 60, 120, and 180 g ha⁻¹) of an inoculant containing R. intraradices. Leaf and kernel macro- and micronutrient contents were evaluated. The foliar P content in 2020 was a function of the interaction between phosphate fertilization and AMF inoculation, with the highest leaf P content observed at the 100% of P₂O₅ combined with AMF inoculation between 120 and 140 g ha⁻¹. In the grains Mg content, an interaction was observed between the two factors in 2020 and the response surface, showing that the highest Mg content was obtained when maximum doses of P₂O₅ and maximum doses of inoculant were combined. A response surface showed that, in 2020, the highest leaf Zn content occurred when 35–55% P₂O₅ is applied with no inoculation and when P₂O₅ is limited to 20–30%, and there is inoculation with doses between 90 and 150 g ha⁻¹. Phosphate fertilization increased foliar K (2019) and Mg (2020) contents, with maximum points at doses of 76.57% and 88.80%, respectively. Full article