Growth responses of Sorghum bicolor (L.) Moench to arbuscular mycorrhizal fungi under simulated nitrogen deposition

Anthropogenic nitrogen (N) deposition leads to a dramatically increase in biologically available N in many ecosystems, which can change the symbiotic relationship between AMF and host plants. However, how and to what extent exogenous N-induced AMF could affect plants remains poorly understood. In this work, mycorrhizal growth responses of Sorghum bicolor to AMF under simulated N deposition were conducted in a glasshouse experiment. Results demonstrated that AMF elevated the growth performance and nutrient uptake (N, P) of S. bicolor at almost all treatments, although mycorrhizal colonization decreased with N addition. In addition, mycorrhizal response (MR) showed identical trend of first fall and then increase, and the lowest value was at the N1 treatment. The present study provided the first pot-based evidence that AMF can alleviate the mischief induced by high N addition, implying that AMF has a considerable significance in the farmland ecosystem under anthropogenic N deposition. Bangladesh J. Bot. 50(3): 933-938, 2021 (September) Special

Mycorrhizal response in crop versus wild plants

We proposed a theoretical framework predicting mutualistic outcomes for the arbuscular mycorrhizal (AM) symbiosis based on host identity (crop versus wild). To test the framework, we grew two isolates of Rhizoglomus irregulare (commercial versus an isolate locally sourced from a site in Saskatchewan), with five crop plants and five wild plants that are endemic to the region and co-occur with the locally sourced fungus. While inoculation had no effect on plant biomass, it decreased leaf P content, particularly for wild plants. All plants associating with the commercial fungus had lower leaf P. Overall, our data shows that wild plants may be more sensitive to differences in mutualistic quality among commercial biofertilizers.

Mycorrhizal response in crop versus wild plants

We proposed a theoretical framework predicting mutualistic outcomes for the arbuscular mycorrhizal (AM) symbiosis based on host identity (crop versus wild). To test the framework, we grew two isolates of Rhizoglomus irregulare (commercial versus an isolate locally sourced from a site in Saskatchewan), with five crop plants and five wild plants that are endemic to the region and co-occur with the locally sourced fungus. While inoculation had no effect on plant biomass, it decreased leaf P content, particularly for wild plants. All plants associating with the commercial fungus had lower leaf P. Overall, our data shows that wild plants may be more sensitive to differences in mutualistic quality among commercial biofertilizers.

Mutualism breakdown in breadfruit domestication

During the process of plant domestication, below-ground communities are rarely considered. Some studies have attempted to understand the changes in root symbionts owing to domestication, but little is known about how it influences mycorrhizal response in domesticated crops. We hypothesized that selection for above-ground traits may also result in decreased mycorrhizal abundance in roots. Breadfruit ( Artocarpus sp.) has a long domestication history, with a strong geographical movement of cultivars from west to east across the Melanesian and Polynesian islands. Our results clearly show a decrease in arbuscular mycorrhizas (AMs) along a domestication gradient from wild to recently derived cultivars. We showed that the vesicular and arbuscular colonization rate decreased significantly in more recently derived breadfruit cultivars. In addition, molecular analyses of breadfruit roots indicated that AM fungal species richness also responded along the domestication gradient. These results suggest that human-driven selection for plant cultivars can have unintended effects on below-ground mutualists, with potential impacts on the stress tolerance of crops and long-term food security.

Relationships among arbuscular mycorrhizas, root morphology and seedling growth of tropical native woody species in southern Brazil

The relationships between arbuscular mycorrhizal fungi and root morphological characteristics were studied under greenhouse conditions of 78 tropical native woody species and 47 seedling species collected in the field. Seedlings of native woody pioneer and early secondary species that generally exhibited fine roots with a dense cover of long root hairs showed higher mycorrhizal response and root mycorrhizal colonization than late-secondary and climax species with coarse roots with a sparse cover of short root hairs. Root-hair length and incidence decreased with the progression among the successional groups while fine-root diameter increased, both in the greenhouse and in the field. The mycorrhizal response was highly correlated to root mycorrhizal colonization in the greenhouse and in the field. These parameters were inversely correlated with the seed mass and fine-root diameter, but directly correlated with root-hair incidence, both in the greenhouse and in the field. Mycorrhizal response and root mycorrhizal colonization were also directly correlated with the root-hair length and root/shoot ratio of uninoculated plants. The seedling mycorrhizal status of the early successional woody species suggests that the root traits of these fast-growing species can be more receptive to attraction, infection and colonization by arbuscular mycorrhizas than root traits of late-successional species.