Evaluation of symbiosis of some poplar species with arbuscular fungi and mycorrhizal inoculation effects on one-year-old Populus nigra plants

Background and objectives: Poplars are important tree species in poplar plantations and agroforestry programs due to their fast growth, high biomass production, and ecological adaptation. On the other hand, arbuscular mycorrhizal fungi can have a good symbiosis with different poplar species. With this symbiosis, growth parameters, biomass production, absorption of water and nutrients, as well as the resistance of poplars to environmental stress, will be increased. Understanding the relationship between mycorrhizas and poplars and how mycorrhizas affect the growth and nutrition of such species may contribute to producing stronger and healthier plants and more sustainable practices in the future.
Methodology: In this study, first of all, the root mycorrhizal colonization percentage of some poplar species (available in the poplar research collection of Alborz Research Center) with arbuscular mycorrhizal fungi was investigated. Then, considering the high percentage of mycorrhizal symbiosis of Populus nigra “62/154” trees and the importance of this clone as a high-yielding poplar clone, widely used in poplar plantations in different parts of the country, symbiotic fungi with this clone were identified through the morphological properties of spores in the rhizosphere soil, and then the identified mycorrhizal fungi were used to produce mycorrhizal plants. Then, poplar cuttings were collected from the Alborz Research Center and planted in pots filled with clay-loam soil. The pots were kept outdoors during the experiment. At the time of planting, mycorrhizal inoculum was applied around each cutting. After that, under an experimental layout consisting of a completely randomized design, some morphophysiological (growth parameters, biomass production, and physiological parameters of leaves) and biochemical (macro and micro nutrients of root, stem, and leaf) responses of one-year-old mycorrhizal and non-mycorrhizal poplar plants were investigated.
Results: The results showed that the percentage of root mycorrhizal colonization of different poplar species was different. The highest percentage of root mycorrhizal colonization was observed in P. nigra “62/154” and P. euphratica, and the lowest percentage in P. deltoides “69/55”. In the soil samples collected from the rhizosphere of P. nigra “62/154”, five species of arbuscular mycorrhizal fungi, including Claroideoglomus luteum, Diversispora tortuosa, Glomus aggregatum, Septoglomus constrictum, and Scutellospora heterogama, were identified. The results demonstrated that mycorrhizal treatment had a significant positive effect (P < 0.01) on growth parameters (diameter and stem length), biomass production (root and shoot dry weight and total dry weight), relative water content of leaves, and nutrient concentrations (nitrogen, phosphorus, potassium, calcium, iron, zinc, and copper) of some plant tissues. Likewise, the content of proline and soluble sugars and the activity of antioxidant enzymes in leaves of mycorrhizal plants increased compared to non-mycorrhizal plants.
Conclusion: The high symbiosis percentage of different poplar species with arbuscular mycorrhizal fungi in natural conditions and the positive effect of mycorrhizal symbiosis on one-year-old poplar plants show that, considering the importance of the role of soil microbial communities in plant nutrition, growth, and protection against environmental stresses, investigating the biological interactions between soil microorganisms and poplars, especially in the early stages of growth, can be used to produce healthy and strong plants for poplar plantations.