Plant Growth Promoting Rhizobacteria (PGPR) induced protection: A plant immunity perspective.

Plant-environment interactions, particularly biotic stress, are increasingly essential for global food security due to crop losses in the dynamic environment. Therefore, understanding plant responses to biotic stress is vital to mitigate damage. Beneficial microorganisms and their association with plants can reduce the damage associated with plant pathogens. One such group is PGPR (Plant growth-promoting rhizobacteria), which influences plant immunity significantly by interacting with biotic stress factors and plant signalling compounds. This review explores the types, metabolism, and mechanisms of action of PGPR, including their enzyme pathways and the signalling compounds secreted by PGPR that modulate gene and protein expression during plant defence. Furthermore, the review will delve into the crosstalk between PGPR and other plant growth regulators and signalling compounds, elucidating the physiological, biochemical, and molecular insights into PGPR's impact on plants under multiple biotic stresses, including interactions with fungi, bacteria, and viruses. Overall, the review comprehensively adds to our knowledge about PGPR's role in plant immunity and its application for agricultural resilience and food security.

Morphological and biochemical responses of Vicia faba (faba beans) grown on fly ash amended soil in the presence of Rhizobium leguminosarum and arbuscular mycorrhizal fungus.

An experiment was conducted in the greenhouse to investigate the feasibility of Vicia faba grown on different fly ash concentrations (0-30%) and dual inoculation with Rhizobium and arbuscular mycorrhizal fungi (AMF). Sampling was done 45 days after sowing to analyse the plant growth parameters, photosynthetic attributes (total chlorophyll and carotenoids content), protein content, nitrogen (N) and phosphorus (P) content, defensive factors (antioxidant activity and proline content) and damage markers (lipid peroxidation, reactive oxygen species and cell viability). The results revealed that the application of fly ash (FA) alone did not result in any significant improvement in growth, biochemical and physiological parameters. However, dual inoculation showed a synergistic impact on legume growth, photosynthetic pigments, protein, proline, and cell viability. Rhizobium, AMF and 10% FA showed maximum enhancement in all attributes mentioned. 20% and 30% fly doses showed a reduction in growth, photosynthesis and antioxidants and caused oxidative stress via lipid peroxidation. The results showed that the synergistic or combined interactions between all three variables of the symbiotic relationship (Rhizobium-legume-AMF) boosted plant productivity.

Exploring the scientific research on coal fly ash and agriculture: knowledge mapping and future research directions.

This paper aims at synthesizing the scientific research on coal fly ash and agriculture using bibliometric analysis. The research on fly ash and agriculture has grown at 6.7% annually during 1973-2022, where much attention has been received after 2007. The number of publications on coal fly ash and agriculture reached above 100 in the year 2010, which further increased to 299 by 2020. The research productivity has been assessed as the most influential countries, journals, and documents in terms of a number of publications and citations on fly ash and agriculture. India is the most productive country in terms of knowledge on coal fly ash and agriculture with 38% of the global publications, while Environmental Science and Pollution Research is the leading journal with 19 publications. The article on assessing the impact of fly ash incorporation in soil systems by Pandey and Singh (2010), having 349 citations with 26.85 citations per year is one of the leading publications globally. Further, science mapping has been conducted to comprehend the current research focus and discover the emerging themes for future research. The finding of the thematic map based on the level of development and importance indicate that FA can be effectively explored as soil-additive for improved physical, chemical and biological properties and enhanced plant nutrients. The findings provide several aspects of fly ash and suggest future research directions to study the potential of using coal fly ash in agriculture to gain an agronomic advantage.

Role of microbial inoculants as bio fertilizers for improving crop productivity: A review.

The world's population is increasing and is anticipated to spread 10 billion by 2050, and the issue of food security is becoming a global concern. To maintain global food security, it is essential to increase crop productivity under changing climatic conditions. Conventional agricultural practices frequently use artificial/chemical fertilizers to enhance crop productivity, but these have numerous negative effects on the environment and people's health. To address these issues, researchers have been concentrating on substitute crop fertilization methods for many years, and biofertilizers as a crucial part of agricultural practices are quickly gaining popularity all over the globe. Biofertilizers are living formulations made of indigenous plant growth-promoting rhizobacteria (PGPR) which are substantial, environment-friendly, and economical biofertilizers for amassing crop productivity by enhancing plant development either directly or indirectly, and are the renewable source of plant nutrients and sustainable agronomy. The review aims to provide a comprehensive overview of the current knowledge on microbial inoculants as biofertilizers, including their types, mechanisms of action, effects on crop productivity, challenges, and limitations associated with the use of microbial inoculants. In this review, we focused on the application of biofertilizers to agricultural fields in plant growth development by performing several activities like nitrogen fixation, siderophore production, phytohormone production, nutrient solubilization, and facilitating easy uptake by crop plants. Further, we discussed the indirect mechanism of PGPRs, in developing induced system resistance against pest and diseases, and as a biocontrol agent for phytopathogens. This review article presents a brief outline of the ideas and uses of microbial inoculants in improving crop productivity as well as a discussion of the challenges and limitations to use microbial inoculants.

Rhizobium induced modulation of growth and photosynthetic efficiency of Lens culinaris Medik. grown on fly ash amended soil by antioxidants regulation.

Rhizobium leguminosarum is a rhizospheres' nitrogen fixing microbe that improves plant growth and productivity by releasing sufficient nutrient sources from the root, by biological nitrogen fixation, solubilization of phosphorous, acquisition of iron, and enhancement of antioxidant activity in plants. On this account, a greenhouse experiment was carried out to assess the feasibility of growing lentil (Lens culinaris Medik.) on fly ash (FA) amended soil (0%, 10%, 20%, and 30%) in combination with R. leguminosarum inoculation. The data was recorded at 45 day after sowing to evaluate the plant growth characteristics, photosynthetic variables (total chlorophyll and carotenoid pigments, carbonic anhydrase activity, nitrate reductase activity), damage markers (ROS, MDA, and cell viability), and defensive factors (proline and antioxidants). Among the FA-proportions tested, 20% proved most favorable in all the mentioned attributes while 30% concentration had negative repercussions on all the variables. Rhizobium inoculation had synergistic effect on all the concentrations being maximum on 20% FA. Thus, Rhizobium and 20% FA caused a significant increase on growth characteristics, photosynthetic pigments; stomatal behavior (aperture shape, size, and frequency of stomata); and activity of CA and NR, and cell viability. Application of Rhizobium on 20% FA was corroborated with decline in MDA and ROS contents and a coordinated enhancement of the activity of SOD, CAT, and POX. Therefore, 20% FA with fly ash-tolerant strain of Rhizobium in Lens culinaris may be utilized as an integrated approach towards sustainable agriculture and an impulse of management of fly-ash.

Impact of bio-fertilizers and different levels of cadmium on the growth, biochemical contents and lipid peroxidation of Plantago ovata Forsk.

Plantago ovata Forsk. (isabgol) is a valuable medicinal plant; its seeds and shell have a significant role in pharmacy as a laxative compound. Increasing soil contamination with cadmium (Cd) is one of the major concerns and is responsible for toxic effects in plants. This investigation was aimed to analyze the role of biofertilizers in alleviation of cadmium stress, given at the rate of 0, 50, and 100 mg kg(-1) of soil. The plants of isabgol, were grown in pots with and without application of AM fungi and Azotobacter (alone and combination). Cadmium showed negative effect on growth and biochemical component whereas proline and MDA content increase with increasing cadmium concentration. Addition of bio-fertilizer showed better growth and higher pigment concentration under cadmium stress as compared to the control. The dual inoculation of AM fungi and Azotobacter was found to be the best in reduction of cadmium stress and promotion of growth parameters.

Influence of wastewater application and fertilizer use on growth, photosynthesis, nutrient homeostatis, yield and heavy metal accumulation in okra (Abelmoschus esculentus L. Moench).

The scarceness of freshwater assets is a serious problem in semi-arid zones and marginal quality water is increasingly being used in agriculture. This study aimed at evaluating the physico-chemical and biological risks on irrigated soils of treated wastewater, the nutrient supply and the effect on okra plant. A pot experiment based on completely randomized block design was conducted with Treated Wastewater (TW) and inorganic fertilizers to observe a comparative effect on biochemical characters using Okra var. Nidhi. The physico-chemical analysis of the TW showed that it was rich in total suspended and dissolved solids with large amount of BOD and COD. The higher amount of Cl-, Ca++, Mg++ and K+ were also present in the effluent. The heavy metal (Cd, Cr, Ni and Pb) content in TW is comparatively more than groundwater (GW). The values of these heavy metals were slightly higher in the soil irrigated with TW. The effluent severely affects crop plants and soil properties when used for irrigation. The growth parameters, photosynthetic characteristics, chlorophyll content, yield and nutrient homeostatis were analyzed during different growth periods in all treatments. All the parameters were found to increase due to wastewater application. Among the fertilizer treatments, N120 proved optimum, N90 deficient and N150 proved as luxury dose. The seeds accumulated Cd and Ni but their level was under permissible limits. Thus, it may be concluded that wastewater may be used profitably for the cultivation of okra.

Variation in growth, physiology and yield of four chickpea cultivars exposed to cadmium chloride.

Cadmium is a highly toxic metallic pollutant which adversely affects plant growth. A green house experiment was conducted to study the variation in growth, yield and proline content of four chickpea (Cicer arietinum L.) cultivars namely ICC1069, ICC12422, ICC7589 and ICC4969 at two plant growth stages (30 and 60 days after sowing), treated with 0, 25, 50 and 100 mg Cd kg(-1) soil. Plant growth, plant fresh weight, plant biomass, leaf area, total photosynthetic area, carbonic anhydrase activity, yield and proline content exhibited a dose-dependent response to Cd on four cultivars of Cicer arietinum L. The shoot and root length showed a reduction of 10.02, 10.63, 12.97, 7.93 and 4.95, 6.09, 7.85, 9.23% in all the four cultivars respectively, whereas shoot and root dry weight showed a reduction of 18.82, 27.61, 11.27, 44.59 and 10.63, 4.89, 3, 11.94% in all the cultivars respectively at 50 mg Cd kg(-1) soil at 30 days of growth stage. It was a general observation from the results that all the parameters of plants were reduced in a concentration-duration dependent manner. However, the proline content of leaf is increased with the increase in Cd concentration. It showed an increase of 15.66, 17.5, 18.42 and 23.61% at 100 mg Cd kg(-1) soil at 30 days of growth stage. Maximal significant reductions in the growth characteristics were observed with 100 mg Cd kg(-1) soil in all the cultivars in both the samplings. Among cultivars, ICC1069 proved tolerant and showed lesser decrease in the growth characteristics, whereas ICC4969 proved as non-tolerant and showed maximum decrease in the growth characteristics.