Inoculation of drought-stressed strawberry with a mixed inoculum of two arbuscular mycorrhizal fungi: effects on population dynamics of fungal species in roots and consequential plant tolerance to water deficiency

Abstract

The effect of inoculation with two arbuscular mycorrhizal fungi (AMF) on growth and drought tolerance of cultivated strawberry (Fragaria × ananassa) was studied. Three treatments (a single treatment either of Funneliformis mosseae BEG25, Funneliformis geosporus BEG11 or a 50:50 mixed inoculation treatment of both species) were compared to uninoculated plants. Species-specific primers for qPCR quantification of F. geosporus and F. mosseae DNA were developed to quantify the relative abundance of each fungus in roots of strawberry under different conditions of water stress. Co-occupation of the same root by both species was shown to commonly occur, but their relative abundance varied with water stress (reduced irrigation of up to 40%). Greater root colonisation was observed microscopically under water stress, but this increased colonisation was often accompanied with decreased amounts of fungal DNA in the root. F. mosseae tended to become more abundant under water stress relative to F. geosporus. There was significant correlation in the fungal colonisation measurements from the microscopic and qPCR methods under some conditions, but the nature of this relationship varied greatly with AMF inoculum and abiotic conditions. Single-species inoculation treatments gave similar benefits to the host to the mixed inoculation treatment regardless of irrigation regime; here, amount of colonisation was of greater importance than functional diversity. The addition of AMF inocula to plants subjected to reduced irrigation restored plant growth to the same or higher values as the non-mycorrhizal, fully-watered plants. The water use efficiency of plants was greater under the regulated deficit irrigation (RDI) regime and in AMF-inoculated plants, but there were no significant differences between plants inoculated with the single or combined inoculum. This study demonstrated that the increase in plant growth was directly influenced by an increase in root colonisation by AMF when individual plants were examined.

Fungal inoculants in the field: Is the reward greater than the risk?

“…Erroneous comparisons can result when inoculated plants are compared to non-inoculated controls (Boyer, Brain, Xu, & Jeffries, 2015;Burkle & Belote, 2015). For example, where plants must first be propagated in nurseries prior field transplantation, uninoculated "controls" typically perform more poorly than inoculated plants (e.g.…”

“…For AMF, there is evidence for reduced competition among closely related species (Engelmoer, Behm, & Toby, 2014;Thonar, Frossard, Šmilauer, & Jansa, 2014) and isolates (Roger, Colard, Angelard, & Sanders, 2013) but others show increased competition (Hart et al, 2013;Maherali & Klironomos, 2012). Other studies indicate a range of factors determine competition outcomes, including infectivity of the inoculum (Abbott & Robson, 1984;Janoušková et al, 2013), fungal life history (Abbott et al, 1983), carbon limitation (Knegt et al, 2014), drought stress (Boyer et al, 2015) and time (Wilson & Trinick, 1983). 2.…”

Genetic and phenotypic associations between root architecture, arbuscular mycorrhizal fungi colonisation and low phosphate tolerance in strawberry (Fragaria × ananassa)

“…AMF symbiotic association has been shown to affect multiple strawberry traits alongside enhanced phosphate uptake under deficit conditions [16]. AMF have been found to restore and even enhance strawberry plant biomass under drought stress [17], increase vegetative reproduction [18,19], increase fruit yield and number [20] and enhance anthocyanins and phenolic production in strawberry fruit [21,22]. Furthermore, AMF colonisation was found to induce strawberry root architecture changes (through an increase in root branching) which was associated with greater resistance to Phytophthora fragariae [23].…”

Fungal Endophytes Enhance Agronomically Important Traits in Severely Drought‐Stressed Barley

“…Several types of fungal functional groups have been shown to enhance drought tolerance in a variety of crop hosts, including mycorrhizal (Boyer et al. ) and endophytic fungi (Hubbard et al. , Oberhofer et al.…”