The significance of mycorrhizal fungi for crop productivity and ecosystem sustainability in organic farming systems

Mycorrhizal fungi are widespread in agricultural systems and are especially relevant for organic agriculture because they can act as natural fertilisers, enhancing plant yield. Here we explore the various roles that mycorrhizal fungi play in sustainable farming systems with special emphasis on their contribution to crop productivity and ecosystem functioning. We review the literature and provide a number of mechanisms and processes by which mycorrhizal fungi can contribute to crop productivity and ecosystem sustainability. We then present novel results, showing that mycorrhizal fungi can be used to suppress several problematic agricultural weeds. Our results highlight the significance of mycorrhizal fungi for sustainable farming systems and point to the need to develop farming systems in which the positive effect of these beneficial soil fungi is optimally being utilized

Natural biofertilizers for organic agriculture: productivity and nutrient uptake of Medicago sativa inoculated with different arbuscular mycorrhizal fungi

Arbuscular mycorrhizas are symbiotic associations that play a key role in plant nutrition by absorbing and translocating mineral nutrients from soil to host plants. Arbuscular mycorrhizal fungi, which are considered natural biofertilizers, show diverse levels of performance, depending on the ability of different isolates to promote plant growth and health. Here we investigated the performance of geographically different isolates of two fungal species, Glomus mosseae and G. intraradices, by assessing plant growth responses and P and N uptake in Medicago sativa, in order to select the most efficient fungi for this host plant. The four selected Glomus isolates significantly increased shoot dry weights and shoot N and P content of mycorrhizal plants, but their performances were different. In particular, G. intraradices IMA6 significantly differed from G. mosseae IMA1 in inducing larger growth responses relative to all parameters measured

Experimental systems to monitor the impact of transgenic corn on keystone soil microorganisms

Risks and benefits of transgenic crop plants should be evaluated not only by assessing pollen flow, but also by considering soil persistence of transgenic products, such as Bt toxins, which can accumulate in the soil and remain active for a long time. Moreover, transgenic plants are often ploughed under as crop residues, representing a potential hazard for non-target arbuscular mycorrhizal (AM) fungi, a group of beneficial plant symbionts fundamental for soil fertility. In this study we monitored the effects of transgenic corn plants (Bt 11 and Bt 176) and their residues on AM fungal growth and root colonization ability. Both transgenic plants decreased mycorrhizal colonization and Bt 11 plant residues negatively affected mycorrhizal establishment by indigenous endophytes, four months after their incorporation into soil

Influence of organic farming on arbuscular mycorrhizal fungal populations in a Mediterranean agro-ecosystem.

Arbuscular mycorrhizal fungi (AMF) are key components of the soil microbiota, fundamental for soil fertility, plant nutrition and functioning of agroecosystems. Data on the interactions between organic practices and AMF populations are limited and inconsistent. Here we compared AM fungal communities and glomalin-related soil protein (GRSP) content occurring in a recently converted organically farmed soil with those occurring in a conventionally managed soil. The results show that the two farming systems did not significantly differ in AM fungal spore populations and glomalin-related soil protein. We hypothesize that in our experimental system, which was converted from conventional to organic farming only recently (5 years), there may not have been enough time to allow the establishment of differentiated AM fungal populations