Ayesha Shafqat

Salinity is a major abiotic stress that severely limits crop productivity worldwide by disrupting plant physiological and metabolic processes. Maize ( Zea mays L.) is considered a moderately salt-tolerant crop; however, high salinity can substantially impair its growth and productivity. This study evaluated the potential of rhizosphere-derived plant growth-promoting rhizobacteria (PGPR) to mitigate salt stress in maize through a bio-priming approach integrated with phenotypic and metabolomic analyses. Soil samples were collected from two maize fields, and 15 bacterial strains were isolated. Based on plant growth-promoting traits and salt tolerance, four promising PGPR strains were selected and evaluated under 250 mM NaCl stress. Bio-priming treatments consisted of UC (untreated control), SU (salt stress only), SB1 (PPB1 + salt stress), SB2 (PPB4 + salt stress), SB3 (PPB8 + salt stress), and SB4 (PPB12 + salt stress). Under salinity stress, PGPR inoculation produced strain-specific improvements in maize growth. Compared with the salinity-stressed treatment (SU), SB3 showed the strongest overall growth-promoting response, significantly increasing shoot and root length by approximately 20% and 45%, shoot and root fresh weight by approximately 95% and 50%, and shoot and root dry weight by approximately 20% and 133%, respectively ( P ≤ 0.05). SB2 also significantly improved shoot and root fresh weight and root dry weight relative to SU. Physiological and biochemical responses were likewise strain dependent. Compared with SU, SB1 significantly enhanced total chlorophyll content, whereas SB1 and SB2 significantly increased carotenoid content. SB2 produced the strongest antioxidant response, significantly enhancing POD, CAT, and APX activities relative to SU ( P ≤ 0.05). For LC–MS-based metabolomic profiling, four treatments were selected: UC, SU, SB2 (SU + PPB4; Bacillus aerius ), and SB3 (SU + PPB8; provisionally identified as a member of the Bacillus cereus group based on 16 S rRNA analysis). Metabolomic profiling revealed treatment-specific changes following PGPR inoculation. Relative to SU, L-citrulline and UDP-N-acetyl-α-D-glucosamine showed approximately 1.54- and 7.70-fold higher abundance, respectively, in SB2, whereas L-methionine showed approximately 5.11-fold higher abundance in SB3. These changes, together with alterations in other plant-related metabolites, indicated metabolic reprogramming associated with improved salinity adaptation. However, because PPB8 was identified only by 16 S rRNA sequencing, genome-based taxonomic confirmation and screening for toxin- and virulence-associated genes are required before considering this strain for agricultural application.

Various fungicides are widely available in local markets, these products are costly and causing environmental pollution. Furthermore, these chemicals are entering into food chain and resulting into bio magnification. Whereas, bio-agents can be used alternative to these non-biodegradable chemical compounds. The present study has been undertaken to eradicate the fungal growth of M. phaseolina by using methanolic leaf extracts of Cassia fistula and Aloe vera. Results indicated that growth of M. phaseolina was significantly reduced by 43% to 90% at 1% to 4% of methanolic leaf extract of C. fistula as compared to control. Furthermore, the application of Alovera gel at 1% to 4% significantly reduced the fresh weight of fungus by 29% to 94% in comparison with control. It was noticed that the total protein content, Catalase and Peroxidase activities of M. phaseolina were significantly enhanced by 3, 1 and 2-fold, respectively as compared to negative control with the application of methanlic leaf extract of C. fistula (1 to 4%). Moreover, the total protein content and said enzymes activities in tested pathogenic fungi were significantly more profound by 3 folds when grown under the stress of Aloevra gel. Findings provide a significant reduction in the growth of fungal mycelium more studies need to be under taken to find the internal mechanism that render the development of pathogen.

Industrial discharge of chromium (Cr) into water bodies poses serious environmental and health risks due to its toxicity, particularly in the hexavalent form (Cr(VI)). This study investigated the biosorption potential of citrus fruit peels orange (Citrus sinensis), lemon (Citrus limon), and musami (Citrus limetta) as low-cost biosorbents for the removal of Cr(VI) from aqueous solutions. Dried and powdered peels were used in batch experiments at initial chromium concentrations of 75 and 100 ppm with contact times of 15, 30, and 60 minutes. Chromium removal was quantified using Atomic Absorption Spectroscopy (AAS). All biosorbents showed effective chromium uptake, with biosorption increasing with contact time and metal concentration. Musami peel exhibited the highest removal efficiency, followed by lemon and orange peels. The results demonstrate that citrus peel waste is an economical and environmentally friendly option for chromium remediation in contaminated water.

The intensified concerns related to agrochemicals’ ecological and health risks have encouraged the exploration of microbial agents as eco-friendly alternatives. Some members of Bacillus spp. are potential plant-growth-promoting agents and benefit numerous crop plants globally. This study aimed to explore the beneficial effects of two Bacillus strains (B. subtilis strain IS1 and B. amyloliquificiens strain IS6) capable of alleviating the growth of tomato plants against salinity stress and Fusarium wilt disease. These strains were able to significantly promote the growth of tomato plants and biomass accumulation in pot trials in the absence of any stress. Under salinity stress conditions (150 mM NaCl), B. subtilis strain IS1 demonstrated superior performance and significantly increased shoot length (45.74%), root length (101.39%), fresh biomass (62.17%), and dry biomass (49.69%) contents compared to control plants. Similarly, B. subtilis strain IS1 (63.7%) and B. amyloliquificiens strain IS6 (32.1%) effectively suppressed Fusarium wilt disease and significantly increased plant growth indices compared to the pathogen control. Furthermore, these strains increased the production of chlorophyll, carotenoid, and total phenolic contents. They significantly affected the activities of enzymes involved in antioxidant machinery and the phenylpropanoid pathway. Hence, this study effectively demonstrates that these Bacillus strains can effectively alleviate the growth of tomato plants under multiple stress conditions and can be used to develop bio-based formulations for use in the fields.