Mycorrhizal responsiveness of aerobic rice genotypes is negatively correlated with their zinc uptake when nonmycorrhizal

Abstract

Plant Zn uptake from low Zn soils can be increased by Zn-mobilizing chemical rhizosphere processes. We studied whether inoculation with arbuscular mycorrhizal fungi (AMF) can be an additional or an alternative strategy. We determined the effect of AMF inoculation on growth performance and Zn uptake by rice genotypes varying in Zn uptake when nonmycorrhizal. A pot experiment was conducted with six aerobic rice genotypes inoculated with Glomus mosseae or G. etunicatum or without AMF on a low Zn soil. Plant growth, Zn uptake and mycorrhizal responsiveness were determined. AMFinoculated plants produced more biomass and took up more Zn than nonmycorrhizal controls. Mycorrhizal inoculation, however, significantly increased Zn uptake only in genotypes that had a low Zn uptake in the nonmycorrhizal condition. We conclude that genotypes that are less efficient in Zn uptake when nonmycorrhizal are more responsive to AMF inoculation. We provide examples from literature allowing generalization of this conclusion on a trade off between mycorrhizal responsiveness and nutrient uptake efficiency.

Influence of arbuscular mycorrhizal fungi on uptake of Zn and P by two contrasting rice genotypes

“…Mycorrhizal responsiveness (MR) was calculated as: MR = [(Plant dw +AMF -Plant dw -AMF )/Plant dw -AMF ] × 100 (Hetrick et al 1992). Mycorrhizal nutrients responsiveness (MNR) was calculated similarly: MNR = [(Nutrients uptake +AMF -Nutrients uptake -AMF )/Nutrients uptake -AMF ] × 100 (Gao et al 2007). …”

“…Root colonization by AMF improves P (Smith et al 2003) and Zn (Gao et al 2007) uptake per unit of root length due to the enhancement of root surface area by hyphal growth and providing an extra route for P uptake as mycorrhizal pathway. In this work, growth response of root to AMF is possibly another important cause of increased P and Zn uptake by inoculation as well as genotypic differences.…”

Characterization of 68Zn uptake, translocation, and accumulation into developing grains and young leaves of high Zn-density rice genotype

“…To increase Zn uptake by roots, the Zn availability in the rhizosphere must be increased (Welch, 1995), which can be performed by enhanced release rates of root-cell H + , metal chelating compounds and/or reductants, by increasing root absorptive surface area (fine roots and root hairs), and by association with mycorrhizal fungi (Liu et al, 2000;Ryan and Angus, 2003;Gao et al, 2007). However, knowledge on Zn transport in rice plant is scant (Grusak et al, 1999;Rengel, 1999).…”

Variation in phosphorus acquisition efficiency among maize varieties as related to mycorrhizal functioning

“…This variation has been linked to root traits: plants with thin roots with abundant and long root hairs are generally little responsive to AMF, whereas plants with thick, unbranched roots with sparse and short root hairs show large responsiveness (Baylis 1975). Next to interspecific variation in responsiveness, intraspecific variation in responsiveness has also been demonstrated for wild plants and (especially) for major crops, such as the main cereals (wheat, barley, maize, rice), legumes, tomato, onion and cassava (Baon et al 1993;Galvá n et al 2011;Gao et al 2007;Hajiboland et al 2010;Hetrick et al 1996;Kaeppler et al 2000;Sieverding and Toro 1988;Wilson and Hartnett 1998).…”

“…Within plant species, there is genetic variation in dependency on and responsiveness to AMF Galvá n et al 2011;Gao et al 2007;Kaeppler et al 2000). This variation may be used to breed varieties that derive more benefit from the mycorrhizal symbiosis.…”