Role of arbuscular mycorrhizal symbiosis in phosphorus-uptake efficiency and aluminium tolerance in barley growing in acid soils

Abstract

Arbuscular mycorrhizal fungi (AMF) play an important role in protecting plant growth against such stresses as phytotoxic aluminium (Al) in soil. To understand some of the AMF interactions that relate to amelioration of Al phytotoxicity and phosphorus (P)-uptake efficiency in barley (Hordeum vulgare L.), this study examined the effect of soil Al levels and mycorrhizal symbiosis on plant response, including root colonisation, AMF propagules and glomalin production. A greenhouse experiment was conducted using two native barley cultivars, Sebastián and Aurora, grown in an acidic soil at two Al-saturation levels (80% Al-sat, unlimed soil; 7% Al-sat, limed soil) with and without AMF propagules. Root dry weight, total and colonised root lengths, and root P and Al contents were determined at 60 and 150 days after sowing. AMF spore density, total hyphal length, glomalin-related soil protein (GRSP) and Al bound to GRSP (Al-GRSP) were analysed at final harvest. AM root colonisation was not inhibited in limed soil, mycorrhizal propagule numbers increased at high Al levels, and Al-GRSP ranged from 5.6% to 8.3% of the total GRSP weight. These values also increased in unlimed soil, particularly those associated with cv. Aurora. Root Al concentration correlated inversely with AMF spores (r = –0.85, P < 0.001) and Al-GRSP (r = –0.72, P < 0.01), but only in plants growing in limed soil. Conversely, the AMF treatments in which Al was present showed a greater relationship between total root length and both root Al (r = –0.72, P < 0.01) and root P (r = 0.66, P < 0.01) concentrations. Sebastián showed a greater response to lime, whereas Aurora responded better to mycorrhizal presence. The relative growth rate of roots, P uptake efficiency and mycorrhizal parameters such as root colonisation, spores, hyphae and GRSP showed Aurora to be more Al-tolerant than Sebastián. In conclusion, the greater rate of increase of AM propagules, GRSP and Al-GRSP associated with cv. Aurora supports the hypothesis that AMF play an important role in the Al-tolerance capacity and P-uptake efficiency of H. vulgare growing in soils with high Al levels.

Arbuscular Mycorrhizal symbiosis in four Al-tolerant wheat genotypes grown in an acidic Andisol

“…These variations can do the difference in the Al tolerance of different wheat genotypes grown under these conditions. Across many studies of AM development in plants exposed to Al, there is a tendency for fungal colonization to be unaffected or increase of host roots, although some fungal species/isolates do exhibit reductions in colonization in response to Al in the environment (Seguel et al, 2015). Therefore, there is not a consensus of the degree of Al tolerance in host plants in relation to levels of root colonization in the long term.…”

“…In addition to direct effects of AM fungi in conferring Al tolerance by increased number of AM propagules or an improved nutritional status of host plant, the AM fungi play important roles through Al-P interactions (Marschner, 1995;Seguel et al, 2015). In this sense, the exudation of organic acids (as malate/ citrate) or enzymes (as acid phosphatases) into the rhizosphere are key factors (Ciereszko et al, 2011).…”

Linking lipid transfer with reduced arbuscule formation in tomato roots colonized by arbuscular mycorrhizal fungus under low pH stress

“…Acidic soil is widely distributed in tropical and subtropical regions around the world, where low pH in combination with high levels of activated Al 3+ severely restricts root growth and nutrient uptake by plants (Mariano et al, 2015;Kichigina et al, 2017;Singh et al, 2017). In response to this stress, plants develop many strategies to cope with it, e.g., the establishment of symbiosis with AM fungi (Seguel et al, 2013;Seguel et al, 2015;Aguilera et al, 2018). Clark et al (1999a) demonstrated that inoculation with AM fungi significantly increased nutrient uptake by maize and thus the plant biomass in acidic soil with pH 4.0.…”

Lime movement through highly weathered soil profiles

“…Thus, improving soil fertility and correcting soil pH are two of the greatest tropical soil fertility needs. Application of lime and fertilizer can increase nutrient concentrations and their availability for plants, and reduce concentrations of dissolved Al in soil solution which can restrict crop growth by competing with plant nutrients (Correia et al 2004, Seguel et al 2015. With conventional tillage (CT), lime and fertilizers are incorporated into the topsoil (i.e., 0 to 20 cm) by plowing and harrowing, but with no-tillage (NT) soil disturbance is restricted to the seeding row and lime is generally applied without incorporation on the soil surface.…”