| چکیده انگلیسی مقاله |
Introduction: Ectomycorrhizal truffle fungi (Tuber spp.) can establish a strong symbiotic relationship with trees in the beech family (Fagaceae), which enhances the trees growth and resilience against both biotic and abiotic stresses. Moreover, truffle fungi are economically valuable. This study aimed to assess the ectomycorrhizal colonization between Persian oak (Quercus brantii) and the summer truffle fungus (Tuber aestivum), as well as to evaluate the drought tolerance of Persian oak seedlings by measuring their morpho-physiological parameters. Materials and Methods: Summer truffle samples were collected from a planted area of Quercus castaneifolia C.A.Mey., Crataegus monogyna Jacq., and Pinus nigra J.F.Arnold. in Mazandaran Province. Morphological, microscopic, and molecular assessments were conducted to confirm the species. Truffle inoculum was prepared and 10 mL of inoculum was injected into the roots of two-month-old Persian oak seedlings. After one year, during which mycorrhizae had formed, drought stress (25%, 50%, and 75% of field capacity) was applied for three months. Random sampling was performed by selecting five control seedlings and five inoculated with the summer truffle (T. aestivum). After washing the roots, they were examined under a stereomicroscope, and the percentage of colonization was recorded. DNA was extracted from the seedlings’ roots using the CTAB method, and the success of the inoculation was confirmed by polymerase chain reaction (PCR). Finally, various growth and biochemical parameters of the seedlings were measured to assess plant health and development. These parameters included seedling height, collar diameter, shoot and root biomass, number of leaves, relative water content (RWC), and chlorophyll content. Additionally, oxidative stress indices such as hydrogen peroxide (H₂O₂), malondialdehyde (MDA), and proline (as an index of stress tolerance) were determined. The activities of antioxidant enzymes, including catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD), were also measured to evaluate the plant’s defense mechanisms against oxidative stress. Results: Inoculating Persian oak seedlings with the summer truffle improved all growth traits compared to the control under all levels of drought stress, though the effect was less pronounced at 25% field capacity than at 50% field capacity. Inoculation with the summer truffle resulted in a 2.3-fold increase in shoot dry weight and a 1.8-fold increase in root dry weight under 50% field capacity drought stress, showing the most significant effect. Root inoculation with the summer truffle increased chlorophyll a, chlorophyll b, and total chlorophyll content by 17 mg, 11 mg, and 15 mg, respectively, compared to the control. Inoculation of Persian oak with the summer truffle increased CAT, POD, and SOD activities by 30%, 23%, and 13%, respectively, compared to the control. Additionally, inoculation with the summer truffle reduced MDA and H₂O₂ levels by 19% and 10%, respectively, under severe drought stress (25% field capacity). Conclusion: The summer truffle (Tuber aestivum) appears to have alleviated the detrimental effects of water deficit on the physiological traits of Persian oak seedlings, even under moderate to severe drought stress. The positive response of Persian oak seedlings to ectomycorrhizal inoculation with the summer truffle and their enhanced drought tolerance, this fungus can be used for planting mycorrhizal seedlings. The positive effects of this experiment could benefit local communities economically and encourage public participation in the conservation and development of these seedlings. |