Feremycorrhizal symbiosis confers growth and nutritional benefits to mycorrhizal and non-mycorrhizal crops

Synergism between feremycorrhizal symbiosis and free-living diazotrophs leads to improved growth and nutrition of wheat under nitrogen deficiency conditions

“…Root fungal symbionts such as AM and ECM fungi have been shown to synergistically interact with both free-living and symbiotic diazotrophs in soil, providing additional N benefits to host plants (Paul et al 2007;Sabannavar and Lakshman 2008). Biological N 2 fixation has been reported exclusively in the prokaryotes (Mus et al 2016); we accordingly hypothesize that the improved N nutrition of Australian native plants (Kariman et al 2014) and agricultural crops (Kariman et al 2020) in symbiosis with the FM fungus A. occidentalis in sandy soils low in organic matter (Kariman et al 2014(Kariman et al , 2020 was due to the stimulation of the activity of rhizosphere microbial communities, including free-living diazotrophs.…”

“…It is known that all currently documented Austroboletus species (except A. occidentalis) form ectomycorrhizal (ECM) symbiosis with plants (Orlovich and Cairney 2004;Smith et al 2013;Vasco Palacios 2016), suggesting that the FM symbiosis has evolved from the ECM symbiosis as manifested in an Austroboletus species native to Australia within the harsh, nutrient-poor jarrah forest ecosystem. In contrast to all known mycorrhizal/endophytic associations, in FM symbiosis, fungal hyphae do not colonize plant roots (Kariman et al 2014(Kariman et al , 2018(Kariman et al , 2020. Hence, functional pathways in the FM symbiosis are different from those in conventional arbuscular mycorrhizal (AM) and (to some extent) ECM symbioses.…”

“…The Australian native fungus Austroboletus occidentalis (Boletaceae, Basidiomycota) establishes feremycorrhizal (FM) symbiosis, conferring significant growth and nutritional benefits to diverse host plants, including the Australian native plant jarrah (Eucalyptus marginata) (Kariman et al 2012(Kariman et al , 2014, mycorrhizal crops such as wheat (Triticum aestivum) and barley (Hordeum vulgare), as well as the non-mycorrhizal crop canola (Brassica napus) (Kariman et al 2020). It is known that all currently documented Austroboletus species (except A. occidentalis) form ectomycorrhizal (ECM) symbiosis with plants (Orlovich and Cairney 2004;Smith et al 2013;Vasco Palacios 2016), suggesting that the FM symbiosis has evolved from the ECM symbiosis as manifested in an Austroboletus species native to Australia within the harsh, nutrient-poor jarrah forest ecosystem.…”

“…Hence, functional pathways in the FM symbiosis are different from those in conventional arbuscular mycorrhizal (AM) and (to some extent) ECM symbioses. A direct intraradical nutrient exchange between host plants and fungal partners occurs in AM/ECM symbioses, but not in the FM symbiosis due to lack of root colonization; however, both FM and ECM symbioses exhibit organic acid anion-mediated nutrient solubilization (Kariman et al 2014(Kariman et al , 2020. Therefore, the nutritional benefits of the FM symbiosis are attributed primarily to the fungal role in rhizosphere modification and nutrient solubilization/ mobilization (Kariman et al 2014(Kariman et al , 2020.…”

“…The FM fungus establishes symbiosis with AM, ECM, and non-mycorrhizal plants (Kariman et al 2014(Kariman et al , 2020 and the inoculum of this fungus is inexpensive to mass-produce (Kariman et al unpublished); hence, it is imperative to explore and possibly exploit the fungus-mediated nutritional benefits (e.g., N, P, Zn) in crop production systems. The present study was conducted to (i) explore the potential of the FM fungus A. occidentalis, alone or in combination with free-living diazotrophs consortium, to improve growth and N nutrition of wheat plants grown under N deficiency conditions, (ii) characterize soil chemical/microbial factors linked with symbiotic N nutritional benefits to host plants via assessing soil N forms (NO 3 − -N, NH 4 + -N, and total N) and changes in soil microbial composition, and (iii) determine the capacity of A. occidentalis to utilize different sugars and lignocellulosic substrates as a food source in vitro.…”