Plant growth–promoting rhizobacteria (PGPR) are beneficial soil bacteria that colonize the rhizosphere and enhance plant growth through direct and indirect mechanisms, including nutrient solubilization, phytohormone production, suppression of phytopathogens, and activation of plant defense mechanisms. PGPR‐based techniques are gaining popularity in sustainable agriculture as environmentally friendly alternatives to chemical fertilizers and insecticides. Although PGPR have been extensively studied, the molecular mechanisms behind these beneficial interactions are still dispersed throughout the literature. Recent advances in molecular biology and high‐throughput omics technology have rapidly expanded the identification of genes, pathways, and regulatory networks associated with PGPR activities. However, these findings are often reported in isolation, and a consolidated and integrative synthesis of molecular mechanistic insights is lacking, restricting a system‐level knowledge of PGPR–plant interactions and impeding the rational development of effective bioinoculant formulations. Therefore, a comprehensive review is required to consolidate current understanding and elucidate how molecular pathways support PGPR‐mediated plant growth promotion and biocontrol. This review aims to provide an updated synthesis of molecular mechanisms governing PGPR‐mediated biofertilization and biocontrol. The main mechanisms discussed are microbial‐driven nutrient solubilization and mobilization, phytohormone biosynthesis and signaling, secretion of antimicrobial metabolites and lytic enzymes, and induction of plant systemic resistance pathways. The emphasis is on how these molecular mechanisms combine and work together to promote plant growth, stress tolerance, and disease resistance. This review emphasizes the functional diversity of PGPR and their potential application in next‐generation biofertilizers and biopesticides by incorporating new genomic and molecular findings. A clearer mechanistic framework will help to build more consistent and efficient PGPR‐based technologies, reducing reliance on synthetic agrochemicals and improving soil health and crop production systems.

Aside from being a significant source of highly nutritious and medicinally valuable mushrooms, mushroom cultivation is an important means of environmental remediation. Oyster mushroom (Pleurotus ostreatus) is a versatile mushroom that can be grown in various environmental conditions and non-composted lignocellulosic wastes. The present study was conducted to assess the growth response of oyster mushroom on sesame stalk. Spawn was prepared from a mycelium culture grown on potato dextrose agar. The spawn was inoculated onto sesame stalk and wheat straw substrates and incubated at room temperature in the dark for 21 days. A Completely Randomized Design (CRD) was used with five treatments, including the control (100% wheat straw), which were triplicated. Data was analyzed using Minitab version 19. Significant (P < 0.05) differences in days taken for mycelial colonization, primordial appearance, maturity and yield was observed between the substrate formulations. 100% SS (100% sesame stalk) was fastest (19.00 days) in mycelial colonization period but statistically parity with 75% SS + 25% WS (75% sesame stalk + 25% wheat straw). 75% SS + 25% WS (75% sesame stalk + 25% wheat straw) was faster (3.33 days) for primordial appearance while 100% SS(100% sesame stalk) was faster (6.67 days) in maturity. The highest yield (1850 g) and biological efficiency (185%) was recorded by 100% SS (100% sesame stalk). Pearson’s correlation showed that cap diameter and stipe length directly correlate yield and biological efficiency and faster substrate colonization leads to quicker maturation. The current study suggests that sesame stalk can be an alternative substrate for cultivation of oyster mushrooms.

Nowadays, the inoculation of plant growth-promoting rhizobia in leguminous and nonleguminous crops is given great emphasis as it improves germination and seedling vigor, resulting in increased yields. In this study, 32 rhizobia isolates were obtained from five different sampling sites in Tigray, Ethiopia. Based on morphological, biochemical, and confirmatory tests, including sugar fermentation, the isolates were identified as belonging to the rhizobia genera. In vitro assessment of plant growth-promoting properties revealed that all isolates produced indole-acetic-acid, ammonia, and solubilized phosphate, except TA8, which did not solubilize phosphate. Only 3 isolates (TA1, TA2, and TA8) produced hydrogen cyanide, so they can be used as biocontrol agents. Nineteen isolates showed a growth reduction activity against Fusarium oxysporum, with a percent inhibition range of 34.2%–65.8%. All isolates tolerated a pH range of 4.0–9.0. The isolates showed growth variations in various temperatures and salt concentrations. A few isolates were tolerant up to 45°C temperature and 6% (w/v) CaCl₂ and NaCl concentrations. Inoculation of the isolates to wheat seeds increased seed germination, seedling shoot/root length, and seedling vigor index compared to the positive and negative controls. Isolates KO3, KO4, ME3, and TA5 increased seed germination by 4%. KO1 (11.60 cm) and TA7 (11.70 cm) showed a significantly enhanced shoot length, and ME3 showed a maximum root length (13.90 cm). SH1, KO2, and the positive control showed a significant ( ) increase in pea seed germination (by 20%) compared to the negative control. The positive control had the longest field pea shoot (5.70 cm), and isolate TA9 had the longest field pea root (5.32 cm) compared to the negative control. Generally, the wheat and field pea seedlings responded differently to the inoculation of different isolates. This study shows that Tigray soils harbor a variety of rhizobia species, which can be used as plant growth-promoting and biocontrol agents.

Native rhizobia are a sustainable alternative to exotic inoculants and excessive agrochemicals in agricultural practices, as they avoid adaptability issues and undesirable effects. This study aimed to identify and characterize native rhizobia from faba bean roots, evaluate their plant growth-promoting properties, and assess plant inoculation effects. Rhizobia were isolated using Yeast Mannitol agar medium and confirmed through biochemical and presumptive tests. Plant growth-promoting features were assessed in vitro, while nodulation and nitrogen fixation were evaluated at molecular level. The effects of the isolates were tested on faba bean seedlings using pot experiment. Totally, 61 faba bean nodule isolates were obtained, categorized into 8 based on morpho-cultural and biochemical features, and 16 isolates selected for further experiments.. All 16 rhizobia isolates (100%) showed positive results in the production of indole-3-acetic acid, ammonia, and exo-polysaccharide, despite varying production capacity among them. Of 16 isolates, 11 (68.75%) formed clear halo zones, with solubilization indices ranging from 0.60 to 2.75. Isolate MR24 showed an expected nifH replicon of approximately 360 bp, while MR1, MR2, and MR48 showed approximately 781 bp unpredicted nifH gene fragment. In addition, MR2, MR6, MR24, and MR26 produced approximately 850 bp unpredicted nodA gene replicon. Inoculation with these isolates significantly (P ≤ 0.05) increased the shoot /root length, shoot fresh/dry weight, and number of nodules compared to the control. Whereas, the exotic inoculant showed better root/ shoot length and shoot dry weight. The isolates can be used as bioinoculants for faba bean growing.

The excessive use of chemical fertilizers has led to soil depletion of essential minerals, causing microorganisms to be distracted and reducing the distribution of soil fauna and flora. The field experiment examined the impact of biofertilizer (Rhizobium and Phosphorus Solubilizing Bacteria) and blended fertilizer (NPKSZn) on the growth, yield, and yield-attributing characteristics of faba bean. The experiment was laid out in RCBD with eight treatments. The result revealed that the application of biofertilizer significantly (P < 0.05) affected the growth and yield characteristics of faba bean. The longest grain filling period (51.42 days), tallest plant height (148.2 cm), Maximum nodulation (79.58), number of branches (6.42), pod per plant (34.08), highest thousand seed weight (699.9 g), grain (2369 kg ha⁻¹), and biological yield (3942 kg ha⁻¹), and the lowest chocolate spot disease severity index (13.33%) was noticed in dual inoculation of Rhizobium and PSB along with recommended dose of NPKSZn in both growing seasons. The highest net benefit (48,174.9 Ethiopian Birr (ETB) per ha) with an acceptable maximum marginal rate of return (789.26%) was recorded in dual inoculation of seed with Rhizobium and PSB. Therefore inoculations of Rhizobium and PSB enhance the production and productivity and reduce the chocolate spot infestation level. Hence the seed must be inoculated with a dual culture of Rhizobium and PSB along with another package of practices for the crop.

Using commonly used agricultural byproducts as a substrate for cultivating mushrooms is challenging due to their high cost. Finding economically viable alternative substrates with a high biomass return, particularly for mushroom production like P. ostreatus, is essential. The aim of this study was to determine the feasibility of the weed (Black-jack straw) for oyster mushroom cultivation. Oyster fruiting bodies were obtained from mushroom growers in Mekelle city, Ethiopia. Mycelial culture was secreted via tissue culture and it was used as inoculum for spawn development. The substrates were chopped, weighed (500 g dry weight of substrate), and sterilized. The substrates were packed in polyethylene bags, inoculated with 4% (w/w) spawn. The five treatments, consisting of various blends of Black-jack and wheat straws, were arranged in completely randomized design with triplicates. The highest average total yield (351 g/bag) and biological efficiency (70.20%) were obtained from 100% Black-jack straw. However, lower yield (199 g/bag) and biological efficiency (39.80%) were obtained from 100% wheat straw. Higher (8.78 cm) mean cap diameter and higher (3.48 cm) mean stipe length were recorded from 75% wheat straw + 25% Black-jack straw and 50% wheat straw + 50% Black-jack straw. This study revealed that the best substrate for overall mushroom yield and biological efficiency was 100% Black-jack. Therefore, the Black-jack straw can be considered as low-cost substrate to effectively substitute wheat straw for the cultivation of oyster (Pleurotus ostreatus) mushroom in the studied area.