Inoculation with Bacillus megaterium CNPMS B119 and Bacillus subtilis CNPMS B2084 improve P-acquisition and maize yield in Brazil.

Phosphorus (P) is a critical nutrient for plant growth, yet its uptake is often hindered by soil factors like clay minerals and metal oxides such as aluminum (Al), iron (Fe), and calcium (Ca), which bind P and limit its availability. Phosphate-solubilizing bacteria (PSB) have the unique ability to convert insoluble P into a soluble form, thereby fostering plant growth. This study aimed to assess the efficacy of inoculation of Bacillus megaterium B119 (rhizospheric) and B. subtilis B2084 (endophytic) via seed treatment in enhancing maize yield, grain P content, and enzyme activities across two distinct soil types in field conditions. Additionally, we investigated various mechanisms contributing to plant growth promotion, compatibility with commercial inoculants, and the maize root adhesion profile of these strains. During five crop seasons in two experimental areas in Brazil, Sete Lagoas-MG and Santo Antônio de Goiás-GO, single inoculations with either B119 or B2084 were implemented in three seasons, while a co-inoculation with both strains was applied in two seasons. All treatments received P fertilizer according to plot recommendations, except for control. Both the Bacillus strains exhibited plant growth-promoting properties relevant to P dynamics, including phosphate solubilization and mineralization, production of indole-3-acetic acid (IAA)-like molecules, siderophores, exopolysaccharides (EPS), biofilms, and phosphatases, with no antagonism observed with Azospirillum and Bradyrizhobium. Strain B2084 displayed superior maize root adhesion compared to B119. In field trials, single inoculations with either B119 or B2084 resulted in increased maize grain yield, with relative average productivities of 22 and 16% in Sete Lagoas and 6 and 3% in Santo Antônio de Goiás, respectively. Co-inoculation proved more effective, with an average yield increase of 24% in Sete Lagoas and 11% in Santo Antônio de Goiás compared to the non-inoculated control. Across all seasons, accumulated grain P content correlated with yield, and soil P availability in the rhizosphere increased after co-inoculation in Santo Antônio de Goiás. These findings complement previous research efforts and have led to the validation and registration of the first Brazilian inoculant formulated with Bacillus strains for maize, effectively enhancing and P grain content.

Plant-associated halotolerant bacteria improving growth of Vicia faba L. Mariout-2 under salinity conditions.

In this comprehensive investigation, we successfully isolated and characterized 40 distinct plant-associated halotolerant bacteria strains obtained from three halophytic plant species: Tamarix nilotica, Suaeda pruinosa, and Arthrocnemum macrostachyum. From this diverse pool of isolates, we meticulously selected five exceptional plant-associated halotolerant bacteria strains through a judiciously designed seed biopriming experiment and then identified molecularly. Bacillus amyloliquefaciens DW6 was isolated from A. macrostachyum. Three bacteria (Providencia rettgeri DW3, Bacillus licheniformis DW4, and Salinicoccus sesuvii DW5) were isolated for the first time from T. nilotica, S. pruinosa and S. pruinosa, respectively. Paenalcaligenes suwonensis DW7 was isolated for the first time from A. macrostachyum. These plant-associated halotolerant bacteria exhibited growth-promoting activities, including phosphate solubilization, nitrogen fixation, and production of bioactive compounds, i.e., ammonia, phytohormones, hydrogen cyanide, siderophores, and exopolysaccharides. A controlled laboratory experiment was conducted to reduce the detrimental impact of soil salinity. Vicia faba seedlings were inoculated individually or in mixtures by the five most effective plant-associated halotolerant bacteria to reduce the impact of salt stress and improve growth parameters. The growth parameters were significantly reduced due to the salinity stress in the control samples, compared to the experimental ones. The unprecedented novelty of our findings is underscored by the demonstrable efficacy of co-inoculation with these five distinct bacterial types as a pioneering bio-approach for countering the deleterious effects of soil salinity on plant growth. This study thus presents a remarkable contribution to the field of plant science and offers a promising avenue for sustainable agriculture in saline environments.

As(III)-oxidizing and plant growth-promoting bacteria increase the starch biosynthesis-related enzyme activity, 2-AP levels, and grain quality of arsenic-stressed rice plants.

BACKGROUND: Grain quality is an important index of rice production, particularly when plants are grown under stress. Arsenic (As) contamination in paddy fields severely affects rice grain yield and quality. Here, the effects of As and combinations of As(III)-oxidizing bacteria (Pseudomonas stutzeri 4.25, 4.27, and 4.44) and plant growth-promoting bacteria (Delftia acidovorans KKU2500-12 and Cupriavidus taiwanensis KKU2500-3) on enzymes related to starch accumulation in grains and the grain quality of Khao Dawk Mali 105 rice cultivated in As-contaminated soil under greenhouse conditions were investigated. RESULTS: Arsenic affected the activities of starch biosynthesis-related enzymes, and decreases of up to 76.27%, 71.53%, 49.74%, 73.39%, and 47.46% in AGPase, SSS, GBSS, SBE, and SDBE activities, respectively, and 9.42-61.07% in starch accumulation in grains were detected after growth in As-contaminated soil. However, the KKU2500-3/4.25 and KKU2500-3/4.44 combinations yielded the greatest enzyme activities in grains, and compared with the results observed in uninoculated seedlings, increases in starch accumulation of up to 51.16% and 23.81% were found in the inoculated seedlings after growth in medium- and high-As-contaminated soils, at 10-17 and 10-24 days after anthesis, respectively. The bacteria increased the 2-AP content in rice under As stress, possibly via the induction of proline, a 2-AP substrate. Bacterium-inoculated rice had significantly greater 2-AP levels than uninoculated rice, and 2.16-9.93% and 26.57-42.04% increases were detected in rice plants grown in medium- and high-As-contaminated soils, respectively. CONCLUSIONS: Arsenic toxicity can be mitigated in rice growing under greenhouse conditions by maintaining starch biosynthesis, accumulating amylose, and increasing 2-AP content. The effectiveness of these bacteria should be validated in paddy fields; hence, safe rice grains with a good starch content and aroma could be produced.

Diverse bacterial consortia: key drivers of rhizosoil fertility modulating microbiome functions, plant physiology, nutrition, and soybean grain yield.

Soybean cultivation in tropical regions relies on symbioses with nitrogen-fixing Bradyrhizobium and plant growth-promoting bacteria (PGPBs), reducing environmental impacts of N fertilizers and pesticides. We evaluate the effects of soybean inoculation with different bacterial consortia combined with PGPBs or microbial secondary metabolites (MSMs) on rhizosoil chemistry, plant physiology, plant nutrition, grain yield, and rhizosphere microbial functions under field conditions over three growing seasons with four treatments: standard inoculation of Bradyrhizobium japonicum and Bradyrhizobium diazoefficiens consortium (SI); SI plus foliar spraying with Bacillus subtilis (SI + Bs); SI plus foliar spraying with Azospirillum brasilense (SI + Az); and SI plus seed application of MSMs enriched in lipo-chitooligosaccharides extracted from B. diazoefficiens and Rhizobium tropici (SI + MSM). Rhizosphere microbial composition, diversity, and function was assessed by metagenomics. The relationships between rhizosoil chemistry, plant nutrition, grain yield, and the abundance of microbial taxa and functions were determined by generalized joint attribute modeling. The bacterial consortia had the most significant impact on rhizosphere soil fertility, which in turn affected the bacterial community, plant physiology, nutrient availability, and production. Cluster analysis identified microbial groups and functions correlated with shifts in rhizosoil chemistry and plant nutrition. Bacterial consortia positively modulated specific genera and functional pathways involved in biosynthesis of plant secondary metabolites, amino acids, lipopolysaccharides, photosynthesis, bacterial secretion systems, and sulfur metabolism. The effects of the bacterial consortia on the soybean holobiont, particularly the rhizomicrobiome and rhizosoil fertility, highlight the importance of selecting appropriate consortia for desired outcomes. These findings have implications for microbial-based agricultural practices that enhance crop productivity, quality, and sustainability.

Invisible Inhabitants of Plants and a Sustainable Planet: Diversity of Bacterial Endophytes and their Potential in Sustainable Agriculture.

Uncontrolled usage of chemical fertilizers, climate change due to global warming, and the ever-increasing demand for food have necessitated sustainable agricultural practices. Removal of ever-increasing environmental pollutants, treatment of life-threatening diseases, and control of drug-resistant pathogens are also the need of the present time to maintain the health and hygiene of nature, as well as human beings. Research on plant-microbe interactions is paving the way to ameliorate all these sustainably. Diverse bacterial endophytes inhabiting the internal tissues of different parts of the plants promote the growth and development of their hosts by different mechanisms, such as through nutrient acquisition, phytohormone production and modulation, protection from biotic or abiotic challenges, assisting in flowering and root development, etc. Notwithstanding, efficient exploitation of endophytes in human welfare is hindered due to scarce knowledge of the molecular aspects of their interactions, community dynamics, in-planta activities, and their actual functional potential. Modern "-omics-based" technologies and genetic manipulation tools have empowered scientists to explore the diversity, dynamics, roles, and functional potential of endophytes, ultimately empowering humans to better use them in sustainable agricultural practices, especially in future harsh environmental conditions. In this review, we have discussed the diversity of bacterial endophytes, factors (biotic as well as abiotic) affecting their diversity, and their various plant growth-promoting activities. Recent developments and technological advancements for future research, such as "-omics-based" technologies, genetic engineering, genome editing, and genome engineering tools, targeting optimal utilization of the endophytes in sustainable agricultural practices, or other purposes, have also been discussed.

Olive Tree Belowground Microbiota: Plant Growth-Promoting Bacteria and Fungi.

The olive tree is one of the most significant crops in the Mediterranean region. Its remarkable adaptability to various environments has facilitated olive cultivation across diverse regions and agricultural scenarios. The rising global demand for olive products, coupled with climate challenges, is driving changes in cultivation methods. These changes are altering the traditional landscape and may potentially reshape the structure and composition of orchard microbial communities, which can impact productivity and stress tolerance. Bacterial and fungal communities naturally associated with plants have long been recognized as crucial for plant growth and health, serving as a vital component of sustainable agriculture. In this review, we aim to highlight the significance of olive cultivation and the impact of abiotic stresses. We update the current knowledge on the profiles of rhizosphere and root fungal and bacterial communities in olive orchards and examine how (a)biotic factors influence these communities. Additionally, we explore the potential of plant growth-promoting bacteria and fungi in enhancing olive physiological performance and stress tolerance. We identify knowledge gaps and emphasize the need for implementing new strategies. A comprehensive understanding of olive-associated microbiota will aid in developing sustainable agronomic practices to address climatic challenges and meet the growing demand for olive products.

Salt-tolerant plant growth-promoting bacteria as a versatile tool for combating salt stress in crop plants.

Soil salinization poses a great threat to global agricultural ecosystems, and finding ways to improve the soils affected by salt and maintain soil health and sustainable productivity has become a major challenge. Various physical, chemical and biological approaches are being evaluated to address this escalating environmental issue. Among them, fully utilizing salt-tolerant plant growth-promoting bacteria (PGPB) has been labeled as a potential strategy to alleviate salt stress, since they can not only adapt well to saline soil environments but also enhance soil fertility and plant development under saline conditions. In the last few years, an increasing number of salt-tolerant PGPB have been excavated from specific ecological niches, and various mechanisms mediated by such bacterial strains, including but not limited to siderophore production, nitrogen fixation, enhanced nutrient availability, and phytohormone modulation, have been intensively studied to develop microbial inoculants in agriculture. This review outlines the positive impacts and growth-promoting mechanisms of a variety of salt-tolerant PGPB and opens up new avenues to commercialize cultivable microbes and reduce the detrimental impacts of salt stress on plant growth. Furthermore, considering the practical limitations of salt-tolerant PGPB in the implementation and potential integration of advanced biological techniques in salt-tolerant PGPB to enhance their effectiveness in promoting sustainable agriculture under salt stress are also accentuated.

Deciphering the enhanced translocation of Pb, Ni and Cd from artificially polluted soil to Chrysopogon zizanioides augmented with Bacillus xiamenensis VITMSJ3.

The translocation of heavy metals (HMs) from the rhizosphere to plant systems constitutes a fundamental mechanism governing HM uptake. Microbial augmentation has emerged as a promising strategy to enhance this process. The study investigates the mechanism of enhanced translocation of heavy metals (HMs) from artificially polluted soil to Chrysopogon zizanioides, facilitated by Bacillus xiamenensis VITMSJ3. Pb, Ni, and Cd translocation to the roots and shoots of C. zizanioides was examined, revealing a significant increase of over 15% in HM uptake upon treatment with Bacillus xiamenensis VITMSJ3 (Accession number MT822866). VITMSJ3 exhibited biofilm formation capabilities, attributed to quorum sensing molecule production, and demonstrated resistance to Pb and Ni upto 4000 ppm and Cd upto 450 ppm, respectively. Moreover, VITMSJ3 displayed plant growth-promoting bacterial (PGPB) traits such as, indole-3-acetic acid (IAA), phosphate, ammonia, siderophore, and hydrogen cyanide (HCN) production. Amplification of candidate genes responsible for HM resistance (pbr for Pb, ncc for Ni, cadA for Cd) corroborated the genetic basis of resistance. SEM-EDAX micrographs confirmed HM uptake and translocation along with the presence of VITMSJ3. Enzymatic analysis revealed the synthesis of superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST), peroxidase (POD), and ascorbate peroxidase (APX), implicating their involvement in ROS detoxification. Overall, the study underscores the efficacy of B. xiamenensis VITMSJ3 in enhancing HM translocation, thereby elucidating its potential for phytoremediation applications. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-024-04001-x.

NaCl Modifies Biochemical Traits in Bacterial Endophytes Isolated from Halophytes: Towards Salinity Stress Mitigation Using Consortia.

Bacterial endophytes (120) were isolated from six halophytes (Distichlis spicata, Cynodon dactylon, Eragrostis obtusiflora, Suaeda torreyana, Kochia scoparia, and Baccharis salicifolia). These halophiles were molecularly identified and characterized with or without NaCl conditions. Characterization was based on tests such as indole acetic acid (IAA), exopolysaccharides (EPS), and siderophores (SID) production; solubilization of phosphate (P), potassium (K), zinc (Zn), and manganese (Mn); mineralization of phytate; enzymatic activity (acid and alkaline phosphatase, phytases, xylanases, and chitinases) and the mineralization/solubilization mechanisms involved (organic acids and sugars). Moreover, compatibility among bacteria was assessed. Eleven halophiles were characterized as highly tolerant to NaCl (2.5 M). The bacteria isolated were all different from each other. Two belonged to Bacillus velezensis and one to B. pumilus while the rest of bacteria were identified up to the genus level as belonging to Bacillus, Halobacillus, Halomonas, Pseudomonas, Nesterenkonia, and three strains of Oceanobacillus. The biochemical responses of nutrient solubilization and enzymatic activity were different between bacteria and were influenced by the presence of NaCl. Organic acids were involved in P mineralization and nutrient solubilization. Tartaric acid was common in the solubilization of P, Zn, and K. Maleic and vanillic acid were only detected in Zn and K solubilization, respectively. Furthermore, sugars appeared to be involved in the solubilization of nutrients; fructose was detected in the solubilization tests. Therefore, these biochemical bacterial characteristics should be corroborated in vivo and tested as a consortium to mitigate saline stress in glycophytes under a global climate change scheme that threatens to exacerbate soil salinity.

The Impact of Nitrogen-Fixing Bacteria-Based Biostimulant Alone or in Combination with Commercial Inoculum on Tomato Native Rhizosphere Microbiota and Production: An Open-Field Trial.

The agricultural sector is currently encountering significant challenges due to the effects of climate change, leading to negative consequences for crop productivity and global food security. In this context, traditional agricultural practices have been inadequate in addressing the fast-evolving challenges while maintaining environmental sustainability. A possible alternative to traditional agricultural management is represented by using beneficial micro-organisms that, once applied as bioinoculants, may enhance crop resilience and adaptability, thereby mitigating the adverse effects of environmental stressors and boosting productivity. Tomato is one of the most important crops worldwide, playing a central role in the human diet. The aim of this study was to evaluate the impact of a nitrogen-fixing bacterial-based biostimulant (Azospirillum sp., Azotobacter sp., and Rhizobium sp.) in combination or not with a commercial inoculum Micomix (Rhizoglomus irregulare, Funnelliformis mosseae, Funnelliformis caledonium, Bacillus licheniformis, and Bacillus mucilaginosus) (MYC) on the native rhizosphere communities and tomato production. Bacterial populations in the different samples were characterized using an environmental metabarcoding approach. The bioinocula effect on the native rhizosphere microbiota resulted in significant variation both in alpha and beta diversity and in a specific signature associated with the presence of biostimulants.

Enhancement of the germination and growth of Panicum miliaceum and Brassica juncea in Cd- and Zn-contaminated soil inoculated with heavy-metal-tolerant Leifsonia sp. ZP3.

The addition of plant-growth-promoting bacteria (PGPB) to heavy-metal-contaminated soils can significantly improve plant growth and productivity. This study isolated heavy-metal-tolerant bacteria with growth-promoting traits and investigated their inoculation effects on the germination rates and growth of millet (Panicum miliaceum) and mustard (Brassica juncea) in Cd- and Zn-contaminated soil. Leifsonia sp. ZP3, which is resistant to Cd (0.5 mM) and Zn (1 mM), was isolated from forest soil. The ZP3 strain exhibited plant-growth-promoting activity, including indole-3-acetic acid production, phosphate solubilization, catalase activity, and 2,2-diphenyl-1-picrylhydrazyl radical scavenging. In soil contaminated with low concentrations of Cd (0.232 ± 0.006 mM) and Zn (6.376 ± 0.256 mM), ZP3 inoculation significantly increased the germination rates of millet and mustard 8.35- and 31.60-fold, respectively, compared to the non-inoculated control group, while the shoot and root lengths of millet increased 1.77- and 4.44-fold (p < 0.05). The chlorophyll content and seedling vigor index were also 4.40 and 18.78 times higher in the ZP3-treated group than in the control group (p < 0.05). The shoot length of mustard increased 1.89-fold, and the seedling vigor index improved 53.11-fold with the addition of ZP3 to the contaminated soil (p < 0.05). In soil contaminated with high concentrations of Cd and Zn (0.327 ± 0.016 and 8.448 ± 0.250 mM, respectively), ZP3 inoculation led to a 1.98-fold increase in the shoot length and a 2.07-fold improvement in the seedling vigor index compared to the control (p < 0.05). The heavy-metal-tolerant bacterium ZP3 isolated in this study thus represents a promising microbial resource for improving the efficiency of phytoremediation in Cd- and Zn-contaminated soil.

Synergy of plant growth promoting rhizobacteria and silicon in regulation of AgNPs induced stress of rice seedlings.

Silver Nanoparticles (AgNPs), as an emerging pollutant, have been receiving significant attention as they deepen the concern regarding the issue of food security. Silicon (Si) and plant growth-promoting rhizobacteria (PGPR) are likely to serve as a sustainable approach to ameliorating abiotic stress and improving plant growth through various mechanisms. The present study aims to evaluate the synergistic effect of Si and PGPRs on growth, physiological, and molecular response in rice seedlings (Oryza sativa) under AgNPs stress. Data suggested that under AgNPs exposure, the root and shoot growth, photosynthetic pigments, antioxidant enzymes (CAT and APX), expression of antioxidant genes (OsAPX and OsGR), silicon transporter (OsLsi2), and auxin hormone-related genes (OsPIN10 and OsYUCCA1) were significantly decreased which accompanied with the overproduction of reactive oxygen species (ROS), nitric oxide (NO) and might be due to higher accumulation of Ag in plant cells. Interestingly, the addition of Si along with the AgNPs enhances the level of ROS generation, thus oxidative stress, which causes severe damage in all the above-tested parameters. On the other hand, application of PGPR alone and along with Si reduced the toxic effect of AgNPs through the improvement of growth, biochemical, and gene regulation (OsAPX and OsGR, OsPIN10 and OsYUCCA1). However, the addition of L-NAME along with PGPR and silicon drastically lowered the AgNPs induced toxicity through lowering the oxidative stress and maintained the overall growth of rice seedlings, which suggests the role of endogenous NO in Si and PGPRs mediated management of AgNPs toxicity in rice seedlings.

Use of plant growth-promoting bacteria to facilitate phytoremediation.

Here, phytoremediation studies of toxic metal and organic compounds using plants augmented with plant growth-promoting bacteria, published in the past few years, were summarized and reviewed. These studies complemented and extended the many earlier studies in this area of research. The studies summarized here employed a wide range of non-agricultural plants including various grasses indigenous to regions of the world. The plant growth-promoting bacteria used a range of different known mechanisms to promote plant growth in the presence of metallic and/or organic toxicants and thereby improve the phytoremediation ability of most plants. Both rhizosphere and endophyte PGPB strains have been found to be effective within various phytoremediation schemes. Consortia consisting of several PGPB were often more effective than individual PGPB in assisting phytoremediation in the presence of metallic and/or organic environmental contaminants.

From trade-off to synergy: microbial insights into enhancing plant growth and immunity.

The reduction in crop yield caused by pathogens and pests presents a significant challenge to global food security. Genetic engineering, which aims to bolster plant defence mechanisms, emerges as a cost-effective solution for disease control. However, this approach often incurs a growth penalty, known as the growth-defence trade-off. The precise molecular mechanisms governing this phenomenon are still not completely understood, but they generally fall under two main hypotheses: a "passive" redistribution of metabolic resources, or an "active" regulatory choice to optimize plant fitness. Despite the knowledge gaps, considerable practical endeavours are in the process of disentangling growth from defence. The plant microbiome, encompassing both above- and below-ground components, plays a pivotal role in fostering plant growth and resilience to stresses. There is increasing evidence which indicates that plants maintain intimate associations with diverse, specifically selected microbial communities. Meta-analyses have unveiled well-coordinated, two-way communications between plant shoots and roots, showcasing the capacity of plants to actively manage their microbiota for balancing growth with immunity, especially in response to pathogen incursions. This review centers on successes in making use of specific root-associated microbes to mitigate the growth-defence trade-off, emphasizing pivotal advancements in unravelling the mechanisms behind plant growth and defence. These findings illuminate promising avenues for future research and practical applications.

Rhizophagus intraradices and Azospirillum brasilense improve growth of herbaceous plants and soil biological activity in revegetation of a recovering coal-mining area.

We assessed, in a field experiment, the effects of arbuscular mycorrhizal fungi (Rhizophagus intraradices) and plant growth-promoting bacteria (Azospirillum brasilense) on the soil biological activity and the growth of key pioneer species used in the revegetation of coal-mining areas undergoing recovery. We applied four inoculation treatments to the pioneer plant species (Lablab purpureus, Paspalum notatum, Crotalaria juncea, Neonotonia wightii, Stylosanthes guianensis, Andropogon gayanus and Trifolium repens) used in the recovery process: NI (Control - Non-inoculated), AZO (A. brasilense), AMF (R. intraradices), and co-inoculation of AZO and AMF. On the 75th and 180th days, we measured plant dry mass, mycorrhizal colonization, N and P concentration, and accumulation in plant tissue. We collected soil to quantify glomalin content and soil enzyme activity. After 180 days, we did a phytosociological characterization of the remaining spontaneous plants.The both microorganisms, singly or co-inoculated, promoted increases in different fractions of soil glomalin, acid phosphatase activity, and fluorescein diacetate activity at 75 and 180 days. The inoculation was linked to higher plant biomass production (62-89%) and increased plant P and N accumulation by 34-75% and 70-85% at 180 days, compared with the non-inoculated treatment. Among the pioneer species sown Crotalaria juncea produced the highest biomass at the 75th and 180th days (67% and 76% of all biomass), followed by Lablab purpureus (3% and 0.5%), while the other species failed to establish. At 180 days, we observed twenty spontaneous plant species growing in the area, primarily from the Poaceae family (74%). That suggests that the pioneer species present in the area do not hinder the ecological succession process. Inoculation of R. intraradices and A. brasilense, isolated or combined, increases soil biological activity, growth, and nutrient accumulation in key pioneer plant species, indicating the potential of that technique for the recovery of lands degraded by coal mining.

Evaluation of commercial importance of endophytes isolated from Argemone mexicana and Papaver rhoeas.

The paper industry is a composite one constituting different types of mills, processes, and products. The paper industries consume large amounts of resources, like wood and water. These industries also create huge amounts of waste that have to be treated. In our study, 23 endophytic bacteria were isolated from Argemone mexicana, and 16 endophytic bacteria were isolated from Papaver rhoeas. Seventeen and 15 bacterial endophytes from A. mexicana and P. rhoeas, respectively, showed cellulose-degrading activity. The biochemical and molecular characterization were done for endophytic bacteria with cellulolytic activity. The consortium of cellulose-degrading endophytic bacteria from A. mexicana showed endoglucanase activity (0.462 IU/ml) and FPCase enzyme activity (0.269 IU/ml) and from P. rhoeas gave endoglucanase activity (0.439 IU/ml) and FPCase enzyme activity (0.253 IU/ml). Degraded carboxy methylcellulose and filter paper were further treated by Saccharomyces cerevisiae and bioethanol was produced. Cellulose-degrading endophytic bacteria were also tested for auxin, siderophore production, and phosphate solubilization activities. Individual cellulose-degrading endophytic bacteria with plant growth-promoting activities were used as biofertilizers, tested for plant growth-promoting activities using Basmati Pusa 1121 rice, and plant growth parameters were recorded. The degraded paper enhances the growth of rice plants. Selected bacterial endophytes and their consortia from A. mexicana and P. rhoeas were powerful cellulose degraders, which can be further employed for ethanol production and as significant biofertilizers in agriculture.

Understanding the dynamic interactions of root-knot nematodes and their host: role of plant growth promoting bacteria and abiotic factors.

Root-knot nematodes (Meloidogyne spp., RKN) are among the most destructive endoparasitic nematodes worldwide, often leading to a reduction of crop growth and yield. Insights into the dynamics of host-RKN interactions, especially in varied biotic and abiotic environments, could be pivotal in devising novel RKN mitigation measures. Plant growth-promoting bacteria (PGPB) involves different plant growth-enhancing activities such as biofertilization, pathogen suppression, and induction of systemic resistance. We summarized the up-to-date knowledge on the role of PGPB and abiotic factors such as soil pH, texture, structure, moisture, etc. in modulating RKN-host interactions. RKN are directly or indirectly affected by different PGPB, abiotic factors interplay in the interactions, and host responses to RKN infection. We highlighted the tripartite (host-RKN-PGPB) phenomenon with respect to (i) PGPB direct and indirect effect on RKN-host interactions; (ii) host influence in the selection and enrichment of PGPB in the rhizosphere; (iii) how soil microbes enhance RKN parasitism; (iv) influence of host in RKN-PGPB interactions, and (v) the role of abiotic factors in modulating the tripartite interactions. Furthermore, we discussed how different agricultural practices alter the interactions. Finally, we emphasized the importance of incorporating the knowledge of tripartite interactions in the integrated RKN management strategies.

Rejuvenating potato growth and yield in challenging semiarid and saline sandy Cholistan: harnessing PGPB-coated N and P application strategies.

BACKGROUND: Potato serves as a major non-cereal food crop and income source for small-scale growers in Punjab, Pakistan. Unfortunately, improper fertilization practices have led to low crop yields, worsened by challenging environmental conditions and poor groundwater quality in the Cholistan region. To address this, we conducted an experiment to assess the impact of two fertilizer application approaches on potato cv. Barna using plant growth-promoting bacteria (PGPB) coated biofertilizers. The first approach, termed conventional fertilizer application (CFA), involved four split applications of PGPB-coated fertilizers at a rate of 100:75 kg acre-1 (N and P). The second, modified fertilizer application (MFA), employed nine split applications at a rate of 80:40 kg acre-1. RESULTS: The MFA approach significantly improved various plant attributes compared to the CFA. This included increased plant height (28%), stem number (45%), leaf count (46%), leaf area index (36%), leaf thickness (three-folds), chlorophyll content (53%), quantum yield of photosystem II (45%), photosynthetically active radiations (56%), electrochromic shift (5.6%), proton flux (24.6%), proton conductivity (71%), linear electron flow (72%), photosynthetic rate (35%), water use efficiency (76%), and substomatal CO2 (two-folds), and lowered non-photochemical quenching (56%), non-regulatory energy dissipation (33%), transpiration rate (59%), and stomatal conductance (70%). Additionally, the MFA approach resulted in higher tuber production per plant (21%), average tuber weight (21.9%), tuber diameter (24.5%), total tuber yield (29.1%), marketable yield (22.7%), seed-grade yield (9%), specific gravity (9.6%), and soluble solids (7.1%). It also reduced undesirable factors like goli and downgrade yields by 57.6% and 98.8%, respectively. Furthermore, plants under the MFA approach exhibited enhanced nitrogen (27.8%) and phosphorus uptake (40.6%), with improved N (26.1%) and P uptake efficiency (43.7%) compared to the CFA approach. CONCLUSION: The use of PGPB-coated N and P fertilizers with a higher number of splits at a lower rate significantly boosts potato production in the alkaline sandy soils of Cholistan.