Addition of high C:N crop residues to a P-limited substrate constrains the benefits of arbuscular mycorrhizal symbiosis for wheat P and N nutrition

Mycorrhizal inoculation enhanced tillering in field grown wheat, nutritional enrichment and soil properties

To meet food security, commercial fertilizers are available to boost wheat yield, but there are serious ill effects associated with these fertilizers. Amongst various organic alternatives, inoculating crop fields with mycorrhizal species is the most promising option. Although, mycorrhizae are known to enhance wheat yield, but how the mycorrhizae influence different yield and quality parameters of wheat, is not clear. Therefore, this study was undertaken to investigate the influence of indigenous mycorrhizal species on the growth of wheat, its nutritional status and soil properties, in repeated set of field experiments. In total 11 species of mycorrhizae were isolated from the experimental sites with Claroideoglomus, being the most dominant one. Five different treatments were employed during the present study, keeping plot size for each replicate as 6 × 2 m. Introduction of consortia of mycorrhizae displayed a significant increase in number of tillers/plant (49.5%), dry biomass (17.4%), grain yield (21.2%) and hay weight (16.7%). However, there was non-significant effect of mycorrhizal inoculation on 1,000 grains weight. Moreover, protein contents were increased to 24.2%. Zinc, iron, phosphorus and potassium concentrations were also increased to 24%, 21%, 30.9% and 14.8%, respectively, in wheat grains. Enhancement effects were also noted on soil fertility such as soil organic carbon % age, available phosphorus and potassium were increased up to 64.7%, 35.8% and 23.9%, respectively. Herein, we concluded that mycorrhizal introduction in wheat fields significantly increased tillering in wheat and this increased tillering resulted in overall increase in wheat biomass/yield. Mycorrhizae also enhanced nutritional attributes of wheat grains as well as soil fertility. The use of mycorrhizae will help to reduce our dependance on synthetic fertilizers in sustainable agriculture.

Cooperation With Arbuscular Mycorrhizal Fungi Increases Plant Nutrient Uptake and Improves Defenses Against Insects

Plants have evolved various defense mechanisms to cope with biotic and abiotic stresses. Cooperation with microorganisms, especially arbuscular mycorrhizal fungi (AMF), strengthens the defense capabilities of host plants. To explore the effect of AMF on the growth of Elymus and the defenses against locust feeding, we designed a two-compartment device to connect or cut the mycelia and roots. We used this to investigate communication cues and pathways between donor and receiver plants. We found that AMF significantly increased the nitrogen content and decreased the carbon to nitrogen (C:N) ratio of donor plants and receiver plants and the carbon content of both. After the establishment of the common mycorrhizal network (CMN) with AMF between the two chambers, inoculations of donor plants challenged by locusts caused enhancement in four defense-related enzymes, namely, lipoxygenase, polyphenol oxidase, phenylalanine ammonia lyase, and β-1,3-glucanase, in the receiver plants. The main components of volatile organic compounds emitted by receiver plants were terpenoids. The findings indicated that AMF could not only improve plant growth but also activate the defense response of plants to insect feeding. Four defense enzymes, volatile organic compounds, and carbon and nitrogen content were involved in the defense response, and the mycelial network could act as a conduit to deliver communication signals.