1- Agricultural Research, Education and Extension Organization
Abstract: (115 Views)
Introduction and Objective: Water scarcity and drought stress are major constraints on crop production in arid and semi-arid regions worldwide. Climate change, including reduced water resources and rising temperatures, can significantly impact agriculture, particularly affecting the production and quality of cereal grains. In Iran, the issue of drought stress is especially critical due to the specific climatic conditions and the high-water requirements of rice. To address drought stress and improve rice resilience, various methods have been proposed, with seed bio-priming being one of the most effective. Bio-priming involves pre-treating seeds with microorganisms or biological agents to enhance germination and early plant growth. This technique is valuable due to its positive effects on increasing crop yield, improving soil fertility sustainably, and boosting plant resistance to adverse conditions. In this study, probiotic formulations of Trichoderma were utilized for bio-priming rice seeds. Trichoderma, known for its growth-promoting and biocontrol properties, can enhance root architecture and root system development. The aim of this research is to improve rice plants' ability to access water and enhance their resilience to environmental stresses such as drought and water scarcity. Seed bio-priming, particularly through boosting germination rates, strengthening root growth, and improving the plant's capacity to absorb water and nutrients, helps mitigate the adverse effects of drought stress. Therefore, employing probiotic Trichoderma formulations can improve rice performance under stress conditions and enhance overall production efficiency.
Materials and Methods: To assess the impact of seed bio-priming using Trichoderma fungi on improving the root system and morphological traits of the Hashemi rice cultivar (Oryza sativa L.), experiments were designed and carried out under both laboratory and greenhouse conditions. In the initial phase, bio-priming treatments were applied to both coated and uncoated seeds in the laboratory. The effectiveness of these treatments on uncoated seeds was validated through preliminary testing. Following this, bio-priming experiments with 60 Trichoderma isolates were conducted in a factorial design based on randomized complete block design (RCBD) with 15 replications, using coated seeds. The experimental factors included bio-priming rice seeds with 10 selected Trichoderma isolates, applied at two levels: with and without the fungi. The most effective treatments from the laboratory phase were then evaluated separately and in combination for their ability to stimulate root growth and impact morphological traits in greenhouse conditions.The greenhouse cultivation setup was designed to accurately replicate field conditions. Seeds treated in the laboratory were allowed to germinate and then transferred to seedling trays in the greenhouse. Subsequently, the seedlings were moved to pots, and data on morphological traits were collected at one-month intervals, including inoculation of the pots. Once the plants reached the reproductive stage, measurements of root surface area, root length, and number of roots were recorded.
Findings: Analysis of rice seed germination during the early growth stages revealed that treatments M4, (M9+M74+GL89), and (M9+G131+M4+GL89) resulted in 100% seed germination. Statistical analysis indicated that the germination percentage in treated samples was significantly higher than in control samples, with all treatments showing greater germination rates compared to the control under greenhouse conditions. Heat Map analysis, variance analysis, and mean comparisons demonstrated that the use of Trichoderma significantly (68%) increased the number of tillers, root length, and root number compared to the control treatment. Specifically, the M75 treatment, with 50 roots compared to 23 in the control, had the most significant effect on root number increase. Additionally, the KhB2 treatment produced the longest roots at 35.5 cm, and the GL89 treatment yielded the highest number of tillers at 2.14. Furthermore, the M75 treatment achieved the greatest stem length of 82.5 cm. These results indicate that seed biopriming with Trichoderma can effectively enhance seedling characteristics, root systems, and phenological growth stages of rice plants. Three-dimensional root interaction analyses using Image J software and Heat Map analysis confirmed the superiority of the KhB2 and GL89 treatments in all morphological assessments. These analyses provided a comprehensive view of the root morphology of the superior treatments through three-dimensional charts and Z-scores. The three-dimensional charts revealed that the root surface area in the superior treatments GL89 and KhB2 was significantly greater than in the control treatment. The root surface area for KhB2 was three times greater, and for GL89, it was one and a half times greater than the control. These increases clearly indicate a significant enhancement in root cross-sectional area in the probiotic treatments compared to the control. These findings are consistent with mean comparison data and Heat Map results, confirming the positive impact of probiotic treatments on root surface expansion. Furthermore, an assessment of the biocontrol properties of 10 selected Trichoderma isolates showed that these isolates significantly reduced the longitudinal growth and spore germination of 15 pathogenic fungi compared to the control. Among these isolates, KhB2 and GL89 were identified as having the best performance with reductions of 100% and 93%, respectively, compared to the control.
Conclusion: The final analysis of the findings revealed that the use of the superior Trichoderma strains, KhB2 and GL89, which possess excellent biocontrol and growth-promoting properties, had the greatest impact on increasing root length and number in rice plants. Therefore, the application of these selected probiotic formulations can be recommended as an effective option for introduction to rice growers and use in fields.
Materials and Methods: To assess the impact of seed bio-priming using Trichoderma fungi on improving the root system and morphological traits of the Hashemi rice cultivar (Oryza sativa L.), experiments were designed and carried out under both laboratory and greenhouse conditions. In the initial phase, bio-priming treatments were applied to both coated and uncoated seeds in the laboratory. The effectiveness of these treatments on uncoated seeds was validated through preliminary testing. Following this, bio-priming experiments with 60 Trichoderma isolates were conducted in a factorial design based on randomized complete block design (RCBD) with 15 replications, using coated seeds. The experimental factors included bio-priming rice seeds with 10 selected Trichoderma isolates, applied at two levels: with and without the fungi. The most effective treatments from the laboratory phase were then evaluated separately and in combination for their ability to stimulate root growth and impact morphological traits in greenhouse conditions.The greenhouse cultivation setup was designed to accurately replicate field conditions. Seeds treated in the laboratory were allowed to germinate and then transferred to seedling trays in the greenhouse. Subsequently, the seedlings were moved to pots, and data on morphological traits were collected at one-month intervals, including inoculation of the pots. Once the plants reached the reproductive stage, measurements of root surface area, root length, and number of roots were recorded.
Findings: Analysis of rice seed germination during the early growth stages revealed that treatments M4, (M9+M74+GL89), and (M9+G131+M4+GL89) resulted in 100% seed germination. Statistical analysis indicated that the germination percentage in treated samples was significantly higher than in control samples, with all treatments showing greater germination rates compared to the control under greenhouse conditions. Heat Map analysis, variance analysis, and mean comparisons demonstrated that the use of Trichoderma significantly (68%) increased the number of tillers, root length, and root number compared to the control treatment. Specifically, the M75 treatment, with 50 roots compared to 23 in the control, had the most significant effect on root number increase. Additionally, the KhB2 treatment produced the longest roots at 35.5 cm, and the GL89 treatment yielded the highest number of tillers at 2.14. Furthermore, the M75 treatment achieved the greatest stem length of 82.5 cm. These results indicate that seed biopriming with Trichoderma can effectively enhance seedling characteristics, root systems, and phenological growth stages of rice plants. Three-dimensional root interaction analyses using Image J software and Heat Map analysis confirmed the superiority of the KhB2 and GL89 treatments in all morphological assessments. These analyses provided a comprehensive view of the root morphology of the superior treatments through three-dimensional charts and Z-scores. The three-dimensional charts revealed that the root surface area in the superior treatments GL89 and KhB2 was significantly greater than in the control treatment. The root surface area for KhB2 was three times greater, and for GL89, it was one and a half times greater than the control. These increases clearly indicate a significant enhancement in root cross-sectional area in the probiotic treatments compared to the control. These findings are consistent with mean comparison data and Heat Map results, confirming the positive impact of probiotic treatments on root surface expansion. Furthermore, an assessment of the biocontrol properties of 10 selected Trichoderma isolates showed that these isolates significantly reduced the longitudinal growth and spore germination of 15 pathogenic fungi compared to the control. Among these isolates, KhB2 and GL89 were identified as having the best performance with reductions of 100% and 93%, respectively, compared to the control.
Conclusion: The final analysis of the findings revealed that the use of the superior Trichoderma strains, KhB2 and GL89, which possess excellent biocontrol and growth-promoting properties, had the greatest impact on increasing root length and number in rice plants. Therefore, the application of these selected probiotic formulations can be recommended as an effective option for introduction to rice growers and use in fields.
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