Molecular Pathogens, 2025, Vol.16, No.5, 217-225 http://microbescipublisher.com/index.php/mp 221 function because they will be affected by competition from indigenous flora and environmental factors. To this end, it is necessary to screen for efficient strains adapted to the local environment and improve the preparation formula (such as adding protective agents, sustained-release carriers) to improve the stability of the bacterial agent. The impact of long-term application of fungicides on soil microbial communities should also be evaluated to ensure that the original ecological balance will not be destroyed. Figure 2 The scheme of bioassay of the different types of resistance to aphids-antibiosis (A) and endurance (B) (Adopted from Rumyantsev et al., 2023) 6 Interaction between Wheat Roots and Growth-Promoting Microorganisms (PGPR) 6.1 Main PGPR categories and functions Plant growth-promoting rhizobacteria (PGPR) are beneficial bacterial groups that colonize the rhizosphere and promote plant growth, including various genera such as Bacillus, Pseudomonas, and Azospirillum. They enhance wheat growth through multiple mechanisms. First, nutrient supply: nitrogen-fixing bacteria provide nitrogen sources for plants, while phosphate- and potassium-solubilizing bacteria release otherwise unavailable phosphorus and potassium in the soil, improving nutrient availability (Bhattacharyya and Jha, 2012). Second, direct growth promotion: PGPR synthesize plant hormones such as indole-3-acetic acid (IAA) and cytokinins to stimulate root growth, and produce ACC deaminase to alleviate ethylene-induced growth inhibition under stress. Third, disease suppression and plant protection: they secrete antibiotics and degrading enzymes to inhibit pathogens and induce systemic resistance in plants, thereby enhancing disease and pest resistance (Dahiya et al., 2020). Different PGPR strains have distinct functional emphases and are often used in combination to achieve synergistic effects. 6.2 Physiological mechanisms that promote wheat growth The main mechanisms by which PGPR bacteria promote wheat growth include improving root structure, increasing nutrient absorption efficiency and enhancing metabolic activity. After inoculation with PGPR, the wheat root system is more developed: the main root is longer, lateral roots and root hairs increase, and the water and fertilizer absorption area expands (Wang et al., 2020). PGPR improves the nutrient utilization efficiency of plants. For example, nitrogen-fixing bacteria provide ammonium nitrogen to reduce wheat's dependence on chemical fertilizer nitrogen, and phosphorus-solubilizing bacteria increase the available phosphorus concentration
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