Macroevolutionary decline in mycorrhizal colonization and chemical defense responsiveness to mycorrhization

Potential to take root in viticulture? An evaluation of mycorrhizal inoculants on the growth and nutrient uptake of young wine grapes planted in live field soil

AIMS

Incorporating biofertilizers, such as arbuscular mycorrhizal fungal (AM) fungal inoculants, into vineyard management practices may enhance vine growth and reduce environmental impact. Here, we evaluate the effects of commercially available and local AM fungal inoculants on the growth, root colonization, and nutrient uptake of wine grapes (Vitis vinifera) when planted in a field soil substrate.

METHODS AND RESULTS

In a greenhouse experiment, young wine grapes were planted in a field soil substrate and inoculated with one of three commercially available mycorrhizal inoculant products, or one of two locally collected whole soil inoculants. After 4 months of growth, inoculated vines showed no differences in plant biomass, colonization of roots by AM fungi, or foliar macronutrient concentrations compared to uninoculated field soil substrate. However, vines grown with local inoculants had greater shoot biomass than vines grown with mycorrhizal inoculant products.

CONCLUSIONS

Although effects from inoculations with AM fungi varied by inoculant type and source, inoculations may not improve young vine performance in field soils with a resident microbial community.

Bacteria Associated with Spores of Arbuscular Mycorrhizal Fungi Improve the Effectiveness of Fungal Inocula for Red Raspberry Biotization

Intensive crop production leads to the disruption of the symbiosis between plants and their associated microorganisms, resulting in suboptimal plant productivity and lower yield quality. Therefore, it is necessary to improve existing methods and explore modern, environmentally friendly approaches to crop production. One of these methods is biotization, which involves the inoculation of plants with appropriately selected symbiotic microorganisms which play a beneficial role in plant adaptation to the environment. In this study, we tested the possibility of using a multi-microorganismal inoculum composed of arbuscular mycorrhizal fungi (AMF) and AMF spore-associated bacteria for biotization of the red raspberry. Bacteria were isolated from the spores of AMF, and their plant growth-promoting properties were tested. AMF inocula were supplemented with selected bacterial strains to investigate their effect on the growth and vitality of the raspberry. The investigations were carried out in the laboratory and on a semi-industrial scale in a polytunnel where commercial production of seedlings is carried out. In the semi-industrial experiment, we tested the growth parameters of plants and physiological response of the plant to temporary water shortage. We isolated over fifty strains of bacteria associated with spores of AMF. Only part of them showed plant growth-promoting properties, and six of these (belonging to the Paenibacillus genus) were used for the inoculum. AMF inoculation and co-inoculation of AMF and bacteria isolated from AMF spores improved plant growth and vitality in both experimental setups. Plant dry weight was improved by 70%, and selected chlorophyll fluorescence parameters (the contribution of light to primary photochemistry and fraction of reaction centre chlorophyll per chlorophyll of the antennae) were increased. The inoculum improved carbon assimilation, photosynthetic rate, stomatal conductance and transpiration after temporary water shortage. Raspberry biotization with AMF and bacteria associated with spores has potential applications in horticulture where ecological methods based on plant microorganism interaction are in demand.

Symbiont plasticity as a driver of plant success

We discuss which plant species are likely to become winners, that is achieve the highest global abundance, in changing landscapes, and whether plant-associated microbes play a determining role. Reduction and fragmentation of natural habitats in historic landscapes have led to the emergence of patchy, hybrid landscapes, and novel landscapes where anthropogenic ecosystems prevail. In patchy landscapes, species with broad niches are favoured. Plasticity in the degree of association with symbiotic microbes may contribute to broader plant niches and optimization of symbiosis costs and benefits, by downregulating symbiosis when it is unnecessary and upregulating it when it is beneficial. Plasticity can also be expressed as the switch from one type of mutualism to another, for example from nutritive to defensive mutualism with increasing soil fertility and the associated increase in parasite load. Upon dispersal, wide mutualistic partner receptivity is another facet of symbiont plasticity that becomes beneficial, because plants are not limited by the availability of specialist partners when arriving at new locations. Thus, under conditions of global change, symbiont plasticity allows plants to optimize the activity of mutualistic relationships, potentially allowing them to become winners by maximizing geographic occupancy and local abundance.