Extraradical development and contribution to plant performance of an arbuscular mycorrhizal symbiosis exposed to complete or partial rootzone drying

Abstract

Sweet potato plants were grown with or without Glomus intraradices in split-root pots with adjacent root compartments containing a soil with a low availability of phosphate. One fungal tube, from which root growth was excluded, was inserted into each root compartment. During 4 weeks before harvest, the soil moisture level in either both or only one of the two root-compartments of each pot was decreased. Controls remained well watered. Low soil moisture generally had a negative effect on the amount of extraradical mycelium of G. intraradices extracted from the fungal tubes. Sporulation in the fungal tubes was much higher compared with the soil in the root compartment, but remained unaffected by the soil moisture regime. Concentrations of P in extraradical mycelium were much lower than usually found in plants and fungi, while P concentrations in associated mycorrhizal host plant tissues were in an optimum range. This suggests efficient transfer of P from the extraradical mycelium to the host plant. Despite the negative effect of a low soil moisture regime on extraradical G. intraradices development, the symbiosis indeed contributed significantly to P uptake of plants exposed to partial rootzone drying. The possibility that extraradical arbuscular mycorrhizal fungal development was limited by P availability under dry soil conditions is discussed.

Constitutive overexpression of the sucrose transporter SoSUT1 in potato plants increases arbuscular mycorrhiza fungal root colonization under high, but not under low, soil phosphorus availability

“…Particularly when the soil nutrient availability is low, AM fungal contribution to plant nutrient uptake and growth can be significant (Neumann and George, 2004;Neumann et al, 2009). In return, the host plant supplies the AM fungus with photoassimilates in the form of hexose.…”

Water availability and formation of propagules of arbuscular mycorrhizal fungi associated with sorghum

“…As mycorrhizal colonization precedes the sporulation of AMF, the reduction in water availability can affect first this step, and works such as that of Neumann et al (2009) demonstrated that plants of Ipomoea batatas L. subjected to water stress for seven days had reduction in root colonization produced by G. intraradices Schenck & Smith. Conversely, Schellenbaum et al (1998) found no reduction in mycorrhizal colonization by an isolate of G. mosseae (T. H. Nicolson Gerd.)…”

“…Under experimental conditions, a gradual reduction of soil moisture over four weeks resulted in increased production of external mycelium and sporulation of Glomus intraradices Schenck & Smith (Neumann et al, 2009). However, in extreme drought conditions a reduction of AMF sporulation occurs, but an increase in the formation of propagules can additionally occur depending on the form and duration of water stress, which is influenced also by the host and fungal species (Augé, 2001).…”

Potential role of D-myo-inositol-3-phosphate synthase and 14-3-3 genes in the crosstalk between Zea mays and Rhizophagus intraradices under drought stress

“…The water loss from the split-root systems with nonuniform water treatments was estimated based on the water replacement needs of the containers with uniform water treatments. Considering lower estimated SWC in the W compartments whose counterpart compartments were subjected to D instead of W (Neumann et al 2009), c. 10 % of daily water depletion from those W compartments was supplemented additionally. Estimation of daily water needs for each compartment is shown in Supplementary Table 1.…”