| چکیده انگلیسی مقاله |
Extended Abstract
Background and Objectives
Drought stress is one of the most important abiotic factors that can harm plant growth, development, and performance. One type of microbe that lives symbiotically with plants is the fungal endophyte, which is crucial for improving the growth and performance of their host plants. Fungal endophytes can improve a plant's ability to survive and resist abiotic stressors, such as drought. Given the growing water scarcity in Iran, there is an urgent need to identify biological treatments that can regulate and improve plant tolerance to drought stress. This study aimed to investigate the effect of the fungal endophyte Aspergillus niger (A. niger), isolated from Teucrium polium L., on improving the growth of garden thyme (Thymus vulgaris L.) under drought-stress conditions.
Methodology
In this experiment, sterilized T. vulgaris seeds were cultivated in trays containing autoclaved peat moss, and the seedlings were transferred to pots after two months. Six months after the transfer of the seedlings to pots, a solution was prepared using the endophytic fungus A. niger, and inoculations were performed on T. vulgaris plants. The spore count of A. niger in each Petri dish was determined using a Neubauer hemocytometer, with a concentration of approximately 106 spores per milliliter (CFU/ml). The solution was then applied as a foliar spray to the aerial parts of the plants (10 ml) and injected into the soil around the roots (5 ml). After one month, a verification test was conducted to ensure the presence of, the endophyte A. niger in the plants. Drought stress was applied using the weight method for three months. Morphological, physiological, and biochemical characteristics of T. vulgaris were evaluated. A factorial experiment was designed using a completely randomized design (CRD) with three replications. The drought treatments included four levels of drought stress (100%, 75%, 50%, and 25% of field capacity) and fungal endophyte inoculation at two levels (control and inoculated with A. niger).
Results
Drought stress caused a significant reduction in plant height, shoot fresh weight, shoot dry weight, root fresh weight, root dry weight, chlorophyll a, chlorophyll b, carotenoids, and relative water content of leaves. However, under severe drought conditions (25%FC), inoculation with the fungal endophyte A. niger led to a notable increase in plant height (39.18%), shoot fresh weight (78.92%), shoot dry weight (58.27%), root fresh weight (74.25%), root dry weight (74.56%), chlorophyll a (8.40%), chlorophyll b (16%), and carotenoids (32.12%). Additionally, the presence of A. niger resulted in elevated levels of proline (13.72%) and soluble sugar (16.43%), along with a decrease in malondialdehyde content (45%), compared to non-inoculated plants under drought stress conditions.
Conclusion
This study demonstrates the positive effect of inoculating T. vulgaris plants with the fungal endophyte A. niger on the quantitative and qualitative characteristics of plant height, shoot fresh weight, shoot dry weight, root fresh weight, root dry weight, relative leaf water content, chlorophyll a, chlorophyll b, carotenoids, proline, soluble sugar, and malondialdehyde in T. vulgaris. Drought stress decreased the studied characteristics, except for the proline content, soluble sugar, and Malondialdehyde. Overall, this study suggests that the use of A. niger fungal endophyte can significantly improve plant growth and reduce the adverse effects of drought stress. Therefore, it is recommended to spray A. niger fungal endophyte during the vegetative growth stage for three weeks and three times under severe stress conditions, as it provides biological compounds from a natural source. |