Phosphate Solubilization Activity Research Articles

IAA-producing plant growth promoting rhizobacteria from Ceanothus velutinus enhance cutting propagation efficiency and Arabidopsis biomass.

Climate-induced drought impacts plant growth and development. Recurring droughts increase the demand for water for food production and landscaping. Native plants in the Intermountain West region of the US are of keen interest in low water use landscaping as they are acclimatized to dry and cold environments. These native plants do very well at their native locations but are difficult to propagate in landscape. One of the possible reasons is the lack of associated microbiome in the landscaping. Microbiome in the soil contributes to soil health and impacts plant growth and development. Here, we used the bulk soil from the native plant Ceanothus velutinus (snowbrush ceanothus) as inoculant to enhance its propagation. Snowbrush ceanothus is an ornamental plant for low-water landscaping that is hard to propagate asexually. Using 50% native bulk soil as inoculant in the potting mix significantly improved the survival rate of the cuttings compared to no-treated cuttings. Twenty-four plant growth-promoting rhizobacteria (PGPR) producing indole acetic acid (IAA) were isolated from the rhizosphere and roots of the survived snowbrush. Seventeen isolates had more than 10µg/mL of IAA were shortlisted and tested for seven different plant growth-promoting (PGP) traits; 76% showed nitrogen-fixing ability on Norris Glucose Nitrogen free media,70% showed phosphate solubilization activity, 76% showed siderophore production, 36% showed protease activity, 94% showed ACC deaminase activity on DF-ACC media, 76% produced catalase and all of isolates produced ammonia. Eight of seventeen isolates, CK-6, CK-22, CK-41, CK-44, CK-47, CK-50, CK-53, and CK-55, showed an increase in shoot biomass in Arabidopsis thaliana. Seven out of eight isolates were identified as Pseudomonas, except CK-55, identified as Sphingobium based on 16S rRNA gene sequencing. The shortlisted isolates are being tested on different grain and vegetable crops to mitigate drought stress and promote plant growth.

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 (0.462IU/ml) and FPCase enzyme activity (0.269IU/ml) and from P. rhoeas gave endoglucanase activity (0.439IU/ml) and FPCase enzyme activity (0.253IU/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.

Paraburkholderia translucens sp. nov. and Paraburkholderia sejongensis sp. nov., isolated from grassland soil and showing plant growth promoting potential.

Two Gram-negative bacterial strains designated MMS20-SJTN17T and MMS20-SJTR3T were isolated from a grassland soil sample, and taxonomically characterized using a polyphasic approach. The 16S rRNA gene sequence analysis indicates that both strains belong to the genus Paraburkholderia of the class Betaproteobacteria, with strain MMS20-SJTN17T being mostly related to Paraburkholderia sprentiae WSM5005T (96.45 % sequence similarity) and strain MMS20-SJTR3T to Paraburkholderia tuberum STM678T (98.59 % sequence similarity). MMS20-SJTN17T could grow at 15-40 °C (optimum, 25-30 °C) and at pH 6.0-8.0 (optimum, pH 6.0-7.0), whereas MMS20-SJTR3T could grow at 10-40 °C (optimum, 30-37 °C) and at pH 6.0-8.0 (optimum, pH 6.0). Both strains tolerated up to 1 % (w/v) NaCl (optimum, 0 %). The major fatty acids of MMS20-SJTN17T were C16 : 0 and C19 : 0 cyclo ω8c, and those of MMS20-SJTR3T were C17 : 0 cyclo and a summed feature comprising C18 : 1 ω7c and/or C18 : 1 ω6c. The major isoprenoid quinone of both strains was ubiquinone-8 and the diagnostic polar lipids were diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine. Regarding plant growth promoting potential, both strains were capable of producing indole acetic acid, siderophore and 1-aminocyclopropane-1-carboxylic acid deaminase, and also showed phosphate-solubilizing activity. A genome-based comparison using orthologous average nucleotide identity and digital DNA-DNA hybridization values indicates that strain MMS20-SJTN17T shares highest relatedness with Paraburkholderia monticola JC2948T and MMS20-SJTR3T with Paraburkholderia antibiotica G-4-1-8T, with values clearly below the cutoffs for species distinction. Examination of biosynthetic gene clusters responsible for secondary metabolite production reveals unique characteristics distinguishing each strain from closely related Paraburkholderia species. On the basis of genotypic, phenotypic, chemotaxonomic and phylogenomic data, each strain should be classified as a novel species of the genus Paraburkholderia, for which the names Paraburkholderia translucens sp. nov. (=MMS20-SJTN17T=LMG 32366T=KCTC 82783T) and Paraburkholderia sejongensis sp. nov. (=MMS20-SJTR3T=LMG 32367T=KCTC 82784T) are proposed.

Antifungal Potential of Bacillus subtilis subsp. inaquosorum RLS76 for Management of Fusarium Wilt Disease of Bt- Cotton

Fusarium wilt is a destructive disease affecting Bt cotton that is caused by Fusarium oxysporum f. sp. vasinfectum. This seed and soilborne disease pose a significant risk to Bt cotton production worldwide, including India. Therefore, to cope with this problem in an eco-friendly manner, we explored the potentiality of the rhizobacterial isolate possessing antifungal activity as a natural arsenal against the fungal pathogen fusarium wilt of Bt cotton. The rhizobacterial isolate RLS76 inhibited 85.39% of the fungal phytopathogen in the dual culture method. The RLS76 isolate's 16S rRNA partial gene sequence was determined to be Bacillus subtilis subsp. inaquosorum RLS76, with a closest phylogenetic affiliation of 99.53%. The crude extract of Bacillus subtilis subsp. inaquosorum RLS76 demonstrated 34.38% inhibition of the growth of the pathogen after a week of incubation by using an agar well diffusion method. Bacillus subtilis subsp. inaquosorum RLS76 produced volatile organic compounds that inhibited the fungal growth of phytopathogens by 54.84% in a closed environment. Also, GCMS analysis of the crude extract of Bacillus subtilis subsp. inaquosorum RLS76 identified four compounds, namely Pyrrolo[1,2-a]pyrazine-1,4-dione, hexahydro-; Pyrrolo[1,2-a]pyrazine-1,4-dione, hexahydro-3-(2-methylpropyl); 2,5-cyclohexadiene-1,4-dione, 2,5-Dihydroxy-3-methoxy-6-methyl-; 9,12-Octadecadienoic acid (Z,Z)-,phenylmethyl ester. Out of four compounds, three exhibit antimicrobial activity except 2,5-Dihydroxy-3-methoxy-6-methyl. The RLS76 strain of Bacillus subtilis subsp. inaquosorum displayed a transition in hue, shifting from blue to orange, surrounding the colony on CAS medium by producing siderophore qualitatively. The quantitative siderophore produced in the crude extract was 86.06 SU after 60-72 h of incubation. The RLS76 strain of Bacillus subtilis subsp. inaquosorum also showed the ability to produce a proteolytic enzyme outside the cell. This enzyme caused a noticeable clear zone around the colony when the bacteria were grown on a skim-milk agar plate. The Bacillus subtilis subsp. inaquosorum RLS76 also exhibited phosphate solubilization activity with the clear halo around the colonies on NBRIP medium. All these results suggest that Bacillus subtilis subsp. inaquosorum RLS76 exhibits good biocontrol as well as a plant growth promoting candidate against the phytopathogen of Fusarium wilt of Bt cotton.

Uncovering the secret weapons of an invasive plant: The endophytic microbes of Anthemis cotula

Understanding plant-microbe interaction can be useful in identifying the microbial drivers of plant invasions. It is in this context that we explored the diversity of endophytic microbes from leaves of Anthemis cotula, an annual plant that is highly invasive in Kashmir Himalaya. We also tried to establish the role of endophytes in the invasiveness of this alien species. We collected and processed leaf samples from three populations at three different sites. A total of 902 endophytic isolates belonging to 4 bacterial and 2 fungal phyla were recovered that belonged to 27 bacterial and 14 fungal genera. Firmicutes (29.1%), Proteobacteria (24.1%), Ascomycota (22.8%) and Actinobacteria (19%) were dominant across all samples. Plant growth promoting traits, such as Ammonia production, Indole Acetic Acid (IAA) production, Phosphate solubilization and biocontrol activity of these endophytes were also studied and most of the isolates (74.68%) were positive for ammonia production. IAA production, phosphate solubilization and biocontrol activity was present in 39.24%, 36.70% and 20.26% isolates, respectively. Furthermore, Botrytis cinerea, a pathogen of A. cotula in its native range, though present in Kashmir Himalaya does not affect A. cotula probably due to the presence of leaf endophytic microbial antagonists. Our results highlight that the beneficial plant growth promoting interactions and enemy suppression by leaf endophytes of A. cotula, may be contributing to its survival and invasion in the Kashmir Himalaya.

Plant-growth stimulating bacteria × environments/bio-formulations interactions on the growth-promoting activities of Serratia marcescens and Pseudomonas fluorescens on chili

Chile has been used as a spice because of its flavor and zest, which complement the minerals, vitamins, and other elements it contains when cooked. The objective of the current study was to determine how P. fluorescens and S. marcescens promote plant growth in Chili plants. The PGPR's phosphate solubilizing, IAA, NH3, HCN production, and antifungal activities were ascertained using in vitro experiments. During the study period 2020–2022, the experiment was conducted using a completely randomized block design, with three replications of the three treatments for each microorganism, as follows: 1) P. fluorescens: T0 (control, unsterile soil), T1 (P. fluorescens in rice husk), and T2 (P. fluorescens in sawdust); 2) S. marcescens: T0 (control, unsterile soil), T1 (S. marcescens in rice husk), and T2 (S. marcescens in sawdust) with no fertilizer. After seeding, the chili plant's parameters were measured at 15, 30, 45, 60, and 75 days and compared to the control using four traits: plant height, root length, shoot length, and the number of leaves per plant. The following bio-formulation, employing T0, enhanced plant height growth after seeding: In rice husk, Days 75 (B2 × D5 × T2) = 21.20 for S. marcescens > Days 75 (B1 × D5 × T2) = 20.83 for P. fluorescens > Days 60 (B1 × D4 × T2) = 19.17 for P. fluorescens Days 75 (B2 × D5 × T0) for S. marcescens in control, days 60 (B1 × D4 × T1 (16.43 cm) for P. fluorescens in sawdust, and days 75 (B1 × D5 × T0) for P. fluorescens in control. The root length (cm) for P. fluorescens in sawdust is 7.23 days (B1 × D5 × T2), which is more than P. marcescens in sawdust (days 60 B1 × D4 × T2), P. fluorescens in control (days 75 (B1 × D5 × T0) = 6.60 cm), and S. marcescens in control (days 75 (B2 × D5 × T0) = 6.60 cm), etc. Rice husk and sawdust were used to create the bio-formulations. The maximum plant growth was achieved at 75 days when S. marcescens was grown in a sawdust medium, including sawdust as a carbon source and carboxymethyl cellulose as a carrier source. When the different compositions of the bio-formulation were tested on chili plants, it was found that P. fluorescens and S. marcescens in sawdust bio-formulation were more effective.

Assessment of root colonization, identification, and phosphate solubilization activity of root endophytic fungi obtained from hybrid tomato Lycopersicon esculentum Mill. var. TNAU CO3

Assessment of root colonization, identification, and phosphate solubilization activity of root endophytic fungi obtained from hybrid tomato Lycopersicon esculentum Mill. var. TNAU CO3

Isolation and screening of stress tolerant and plant growth promoting root nodulating rhizobial bacteria from some wild legumes of Nagaland, India

Wild legumes are widely distributed and better adapted to extreme agro-climatic conditions because of their soil microbiota. In the present study, Root Nodulating Bacteria (RNB) were isolated from wild legumes and analysed for their abiotic stress tolerant and Plant Growth Promoting Traits (PGPT). Rhizobial strains were identified based on their 16S rRNA sequences. A total of 14 rhizobial species were characterized based, of which six were Rhizobium (AIS3, AIS9, AIR14, LUMCR3, LUMVRW4, LUMVRW8), four belongs to Burkholderia (AIS12, MOLKCS15, CHMP9, CHMP10) and one each of genera Cupriavidus (LUMMD12), Herbaspirillum (LUMVRW4), Paraburkholderia (CHMP1) and Ralstonia (LUMDes9). Stress tolerance analysis found most of the strains are to be tolerant to alkaline pH (9–11) where highest tolerance exhibited by Rhizobium sp. (strain AIS9) and Burkholderia territorii (strain MOKCS15). Seven Rhizobial strains were able to thrive at lower temperature stress (10 and 20 °C); while, strains AIS9, CHMP1 and LUMMD21 were able to grow at higher temperature (40 and 50 °C). Most of the isolate could tolerate salinity stress up to 1.5 %; but, only isolates AIS9, AIS12 and LUMMD12 could tolerate 2 and 2.5 % salt concentrations. The PGPT analyses found LUMCR3 having the highest IAA production potentiality (102.5 µg/ml); while, isolate MOKCS15 exhibited highest phosphate solubilizing activity (4.1 Phosphate Solubilization Index). The RNB isolates in the present study exhibited both stress tolerance and PGP traits indicating their potential use as biofertilizer under extreme agronomic conditions to improve productivity.

Plant growth-promoting activities of Serratia marcescens and Pseudomonas fluorescens on Capsicum annuum L. plants

India employs the Solanaceae family plant chili, Capsicum annuum L., for its pungency and flavor. It has been used as a spice because of its delicious flavor and zest, which contribute to the minerals, vitamins, and other culinary ingredients it contains. The objectives of the present study were to determine the plant growth-promoting activities of Serratia marcescens and Pseudomonas fluorescens on the chili plant. The PGPR characteristics, i.e., phosphate solubilizing, IAA, NH3, HCN production, and antifungal activity, were determined in vitro. The bio-formulations were prepared using sawdust and rice husk. The highest plant growth of Serratia marcescens in sawdust was obtained at 75 days in media containing sawdust as a carbon source and carboxymethyl cellulose as a carrier source. The effect of different compositions of bio-formulation on chili plants demonstrated the potential of Serratia marcescens in sawdust bio-formulation, followed by Pseudomonas fluorescens in sawdust.

Diversity, Characterization, and Potential Applications of Bacterial Endophytes Isolated from the Halophyte Limonium axillare

Recently, there has been a worldwide call to explore nature-friendly compounds, which could enhance plant growth and substitute for chemically synthesized products. Endophytes are a group of microorganisms that lives in the plants and algae symbiotically. In this research, endophytes were isolated from leaves of the halophyte, Limonium axillare. A total of 280 bacterial isolates were obtained from the leaves of L. axillare. Strains displaying similarities in terms of morphology and biochemical reactions were categorized into 48 groups. One representative from each group was identified and subjected to enzymatic and plant growth-promoting tests. Forty-eight isolates were identified using a sequence similarity-based method based on the 16S rDNA gene. The identified strains were categorized into two genera: Bacillus and Staphylococcus. Our investigation uncovered 44 isolates from the Bacillus genus, representing 10 different species, including Bacillus sp., B. pseudomycoides, B. cereus, B. paramycoides, B. velezensis, B. subtilis, B. thuringiensis, B. wiedmannii, B. anthracis, and B. bacterium. Furthermore, we observed that only 4 isolates belonged to the Staphylococcus genus, encompassing 3 distinct species: S. bacterium, S. succinus, and S. saprophyticus. The isolated bacteria were screened for extracellular enzymes, plant growth promoting traits, antifungal activity, and salinity tolerance. From the previous screening, diverse responses were obtained. Most of the isolates were secreted at least one of the hydrolysis enzymes (protease, lipase and amylase). (93.8%) of the strains showed phosphate solubilization activity. (33.3%) produce (IAA). Siderophore production potential was present in 91.7% of isolates, while ACC deaminase and HCN production activities were identified in 52.1 and 41.7% of strains, respectively. Additionally, DNase activity was evident in 27.1%, and ammonia production was observed in 31.3% of the isolates. The isolates Bacillus velezensis (AL4QUA) strain showed positive effect in the greenhouse experiment in terms of plant growth promoter agent and biocontrol agent against Fusarium oxysporum pathogen of tomato seedling. Thus, endophytes have the potential to reduce chemical inputs in conventional agricultural practices, increase nutrient uptake and improve plant stress resilience.

Isolation and Characterization of Phosphorus Solubilizing Bacteria from Millet Rhizosphere in Lafia metropolis

Phosphorus is an essential, but often unavailable nutrient for plant growth in the soil due to its low solubility. Phosphorus solubilizing bacteria (PSB) convert insoluble forms of phosphorus into soluble forms that can be taken up by plants. The study aimed to isolate and characterize PSB from the rhizosphere of millet plants in Lafia, and to evaluate their potential for improving soil fertility and crop productivity. Soil samples were collected from four different locations and plated on Pikovskaya's agar medium. PSB colonies were identified based on their ability to produce clear zones around them. The PSB isolates were further characterized by morphological, biochemical, and molecular methods. The phosphate solubilizing activity and plant growth-promoting traits of the PSB isolates were also assessed. The PSB isolates were tested for their effect on the growth of millet seedlings in pots. The results showed that 16 PSB isolates belonging to four genera (Bacillus, Pseudomonas, Enterobacter, and Klebsiella) were obtained from the soil samples. The PSB isolates exhibited varying degrees of phosphate solubilizing activity, ranging from 11.2 to 81.6 mg/L. The PSB isolates also showed positive results for the production of indole acetic acid, ammonia, hydrogen-cyanide, and siderophore. The PSB inoculation significantly increased the shoot and root lengths, and fresh and dry weight of the millet seedlings. The study concluded that the PSB isolates from the millet rhizosphere in Lafia could enhance soil phosphorus availability and millet growth. The study recommended further research on the field application and optimization of the PSB inoculation.

The genome, pangenome, and physiological analysis of Leclercia adecarboxylata (kcgeb_e1), a plant growth-promoting bacterium

Plant growth-promoting bacteria (PGPB) as biofertilizer plays an important role in agriculture practices. In this study, we isolated and identified plant-associated bacteria Leclercia adecarboxylata (kcgeb_e1) from the root region of the halophytic plant Sesuvium verrucosum. We tested its physiological activity and the effect of inoculation, with and without salt, on photosynthesis using Cajanus cajan. Further, we sequenced the whole genome of L. adecarboxylata (kcgeb_e1) and carried out pangenome analysis with 12 other genomes of the same species, which highlights unique genes enriched for pathways involved in abiotic stress tolerance (salinity, drought and heat) and carbohydrate transport. Moreover, gene families involved in abiotic stress tolerance, host adhesion, and transport were under positive selection (e.g., Aldo/keto reductase family, Hemagglutinin, Porin, and sugar transport). We observed a loss of ACC deaminase gene in this pangenome; however, this strain can still produce 1-aminocyclopropane-1-carboxylate (ACC), an enhancer of abiotic stress, which suggests that its homologue, d-cysteine sulfatase, has a bifunctional activity. In addition, this strain has Indole acetic acid (IAA) and phosphate solubilization activity. Combining these findings with the efficiency of colonizing the root surface of Solanum lycopersicum, this strain showed remarkable enhancement of photosynthesis, comparing control to inoculated plants. This increase in photosynthesis is consistent with an increase in sucrose under salt treatment, but not in glucose and fructose, which acts as a sensor in opposing the negative effect of salinity and promoting sustainable growth. Given all this, our study suggests that this PGPB can act as a biofertilizer for sustainable agriculture.

Cultural techniques capture diverse phosphate-solubilizing bacteria in rock phosphate-enriched habitats.

Phosphorus (P) deficiency is a common problem in croplands where phosphate-based fertilizers are regularly used to maintain bioavailable P for plants. However, due to their limited mobility in the soil, there has been an increased interest in microorganisms that can convert insoluble P into a bioavailable form, and their use to develop phosphate-solubilizing bioinoculants as an alternative to the conventional use of P fertilizers. In this study, we proposed two independent experiments and explored two entirely different habitats to trap phosphate-solubilizing bacteria (PSBs). In the first experiment, PSBs were isolated from the rhizoplane of native plant species grown in a rock-phosphate (RP) mining area. A subset of 24 bacterial isolates from 210 rhizoplane morphotypes was selected for the inorganic phosphate solubilizing activities using tricalcium phosphate (TCP) as the sole P source. In the second experiment, we proposed an innovative experimental setup to select mycohyphospheric bacteria associated to arbuscular mycorrhizal fungal hyphae, indigenous of soils where agronomic plant have been grown and trapped in membrane bag filled with RP. A subset of 25 bacterial isolates from 44 mycohyphospheric morphotypes was tested for P solubilizing activities. These two bacterial subsets were then screened for additional plant growth-promoting (PGP) traits, and 16S rDNA sequencing was performed for their identification. Overall, the two isolation experiments resulted in diverse phylogenetic affiliations of the PSB collection, showing only 4 genera (24%) and 5 species (17%) shared between the two communities, thus underlining the value of the two protocols, including the innovative mycohyphospheric isolate selection method, for selecting a greater biodiversity of cultivable PSB. All the rhizoplane and mycohyphospheric PSB were positive for ammonia production. Indol-3-acetic acid (IAA) production was observed for 13 and 20 isolates, respectively among rhizoplane and mycohyphospheric PSB, ranging, respectively, from 32.52 to 330.27 μg mL-1 and from 41.4 to 963.9 μg mL-1. Only five rhizoplane and 12 mycohyphospheric isolates were positively screened for N2 fixation. Four rhizoplane PSB were identified as siderophore producers, while none of the mycohyphospheric isolates were. The phenotype of one PSB rhizoplane isolate, assigned to Pseudomonas, showed four additive PGP activities. Some bacterial strains belonging to the dominant genera Bacillus and Pseudomonas could be considered potential candidates for further formulation of biofertilizer in order to develop bioinoculant consortia that promote plant P nutrition and growth in RP-enriched soils.

Isolation of a potential rock phosphate solubilizing Aspergillus sp. towards development of biofertilizer

Phosphorus (P) is one of the key bio elements that limits agricultural production. Although Sri Lanka is endowed with rock phosphate deposits, practical means to utilize this resource are limited. Phosphate-solubilizing fungi (PSF) play an important role in enhancing the bioavailability of soil phosphorus to plants. In this study, fungi from eight soil samples in Kaikawala, Sri Lanka, were isolated using spread plate method and analyzed for its phosphate solubility capacity. One fungal isolate with significant halo zones on Pikovskaya’s agar (PVK) plates, containing 0.5% tricalcium phosphate, was identified. After purification, the isolate was transferred to three media setups: PVK with 0.5% apatite (ERP) as the phosphate source, PVK with 0.5% tricalcium phosphate as a positive control, and PVK without P source as a negative control and analyzed for the solubilization index (SI). DNA sequences of the internal transcribed spacers with 5.8S region of ribosomal DNA (ITS1-5.8S-ITS2) was analyzed with universal primer pair ITS4-F/ITS5-R to determine the identity of the species. Fungal isolate PSF01 showed a phosphate solubilizing activity on both PVK media, ERP (1.07 ± 0.03 cm SI) and tricalcium phosphate (1.07 ± 0.01 cm), with similar effects (p > 0.05). However, the SI in the negative control was 1.00 ± 0.00 cm without halo zone (p < 0.05). The fungal strain is fast growing with initially white but quickly changing to black colonies after producing conidial spores on potato dextrose agar with distinctive conidial heads and pale-yellow lower surface characterized as Aspergillus. Sanger DNA sequencing identified the fungus as Aspergillus niger (99%) and a phylogenetic tree was constructed using MEGA11 software using reference data obtained from NCBI GenBank data to identify the isolated PSF01. Consequently, our preliminary studies demonstrate the importance of examining more soil samples to identify PSF for sustainable agricultural applications in the future.

Screening and characterization of endophytic bacteria isolated from celery with the potential to promote plant growth

Abstract. Nuriyanah, Widowati T, Masnang A, Nurjanah L, Novilasari D, Lekatompessy SJR, Simarmata R. 2023. Screening and characterization of endophytic bacteria isolated from celery with the potential to promote plant growth. Biodiversitas 24: 6897-6904. Endophytic bacteria that inhabit plant tissue contribute to the enhancement of host plant growth by producing secondary metabolites. They can improve plant growth by phytohormone modulation and nutrient uptake. In addition, endophytic bacteria can increase plant health and tolerance by antibiotic and hydrolytic enzyme production. This study aims to screen and characterize endophytic bacteria of celery as plant growth promoter agents. Thirty endophytic bacteria were isolated successfully from part of the celery plant using the spread plate and plant piece method which grew at Nutrient Agar media. Based on the characterization assay, 30 isolates may produce IAA with various concentrations of 0.21-7.18 mg/L. In addition, 3 of 30 isolates had phosphate solubilizing activity, in different indexes ranging from 0.71-1.43. Twenty-one isolates were able to grow in an N-free medium, indicating the capability of isolates to fix nitrogen qualitatively. The hydrolytic enzymes assay resulted in 14 amylolytic, 17 proteolytic, and 12 cellulolytic activities. In addition, nine of 30 isolates show multi-activity in amylase, protease, and cellulase enzyme production. Based on the screening results, there are four potential isolates (SLBg 1.2; SLBg 1.5; SLAg 1.1, and SLAg 1.5) as promising plant-growth promoters and were molecularly identified as members of the Bacillus genus. These isolates can be developed as biofertilizers for supporting the cultivation of celery plants.

Newly isolated Brevundimonas naejangsanensis as a biocontrol agent againstFusarium redolens the causal of Fusarium yellows ofchickpea.

Three endophytic bacteria, namely BvV, BvP and BvL, were newly isolated from the root nodules of bean, pea and lentil plants respectively cultivated in Mascara the northwest of Algeria, and identified by 16S ribosomal RNA gene sequencing as Brevundimonas naejangsanensis. These strains were able to produce hydrolytic enzymes and hydrogen cyanide. All strains produced a growth-promoting hormone, indole acetic acid, varying in concentration from 83.2 to 171.7 µg/mL. The phosphate solubilizing activity of BvV, BvP and BvL varied from 25.5 to 42.02 µg/mL for tricalcium phosphate. The three antagonistic Brevundimonas spp. showed in vitro the most inhibitory effect on mycelial growth of Fusarium redolens FRC (from 78.33 to 85.55%). Strain BvV, BvP and BvL produced also volatile metabolites which inhibited mycelial FRC growth up to 39.2%. All strains showed significant disease reduction in pot experiments. Chickpea Fusarium yellows severity caused by FRC was reduced significantly from 89.3 to 96.6% in the susceptible cultivar ILC 482 treated with antagonistic B. naejangsanensis. The maximum stimulatory effect on chickpea plants growth was observed by inoculation of strain BvV. This treatment resulted in a 7.40-26.21% increase in shoot height as compared to the control plants. It is concluded that the endophytic bacterial strains of B. naejangsanensis having different plant growth promoting (PGP) activities can be considered as beneficial microbes for sustainable agriculture. To our knowledge, this is the first report to use B. naejangsanensis strains as a new biocontrol agent against F. redolens, a new pathogen of chickpea plants causing Fusarium yellows disease in Algeria.

Divulgence into Mung Bean Growth Promotion Potential of Endophytes Isolated Across Different Geographical Regions of India

Background: Endophytic fungi in symbiotic association with their host plant are well known to improve plant growth and reduce the adverse effects of abiotic stresses. Therefore, fungal endophytes are beginning to receive increased attention in an effort to find growth-promoting strains that could be applied to enhance crop yield and quality. Methods: In our study, the plant growth promoting activities of endophytic fungi isolated from various parts of India have been revealed and investigated. Fungal isolates were identified using molecular taxonomical methods, while their plant growth promoting abilities were evaluated in plate assays and in vitro studies. Altogether, seven strains were selected, representing the genera Fusarium, Chaetomium and Ulocladium. Result: Six of the isolates possessed phosphate solubilization activities, four secreted siderophores and four showed amylase activity, while all of them were able to produce indoleacetic acid (IAA). In order to investigate the effect of endophytes on plant growth, all seven fungi were selected concerning their potential ability to promote growth in mung bean. The results indicated that microbial endophytes selected from different geographical regions living originally in the plant host are able to influence the growth and fitness parameters of other plants through their promotion effects and could be used as inoculants to establish a sustainable crop production system.

Enhancing rice growth and yield with weed endophytic bacteria Alcaligenes faecalis and Metabacillus indicus under reduced chemical fertilization.

Endophytic bacteria, recognized as eco-friendly biofertilizers, have demonstrated the potential to enhance crop growth and yield. While the plant growth-promoting effects of endophytic bacteria have been extensively studied, the impact of weed endophytes remains less explored. In this study, we aimed to isolate endophytic bacteria from native weeds and assess their plant growth-promoting abilities in rice under varying chemical fertilization. The evaluation encompassed measurements of mineral phosphate and potash solubilization, as well as indole-3-acetic acid (IAA) production activity by the selected isolates. Two promising strains, tentatively identified as Alcaligenes faecalis (BTCP01) from Eleusine indica (Goose grass) and Metabacillus indicus (BTDR03) from Cynodon dactylon (Bermuda grass) based on 16S rRNA gene phylogeny, exhibited noteworthy phosphate and potassium solubilization activity, respectively. BTCP01 demonstrated superior phosphate solubilizing activity, while BTDR03 exhibited the highest potassium (K) solubilizing activity. Both isolates synthesized IAA in the presence of L-tryptophan, with the detection of nifH and ipdC genes in their genomes. Application of isolates BTCP01 and BTDR03 through root dipping and spraying at the flowering stage significantly enhanced the agronomic performance of rice variety CV. BRRI dhan29. Notably, combining both strains with 50% of recommended N, P, and K fertilizer doses led to a substantial increase in rice grain yields compared to control plants receiving 100% of recommended doses. Taken together, our results indicate that weed endophytic bacterial strains BTCP01 and BTDR03 hold promise as biofertilizers, potentially reducing the dependency on chemical fertilizers by up to 50%, thereby fostering sustainable rice production.

Isolation and Screening of Plant growth promoting rhizobacteria from agricultural soils of semi-arid Kachchh district, Gujarat, Western India

This study aimed to identify Plant Growth Promoting Rhizobacteria (PGPR) from the rhizospheric region of crops in the Kachchh district. Bacterial isolation was performed through serial dilution techniques using different media (Himedia), and 130 bacterial cultures were isolated, with 61 morphologically distinct strains selected for further screened for PGPR traits such as Phosphate solubilization, IAA, Ammonia, Exopolysaccharide production, HCN Production, and Antifungal activity. Among these, three strains (D6, E11, and G14) exhibited the highest number of Plant Growth-Promoting Rhizobacteria traits, showed nonpathogenic characteristics in Hemolysis test, and growth rate were also estimated at a different time interval. The selected strains can further significantly contribute to the development of sustainable and eco-friendly agricultural practices by employing beneficial bacteria for plant growth, and soil fertility and it can be an alternative to chemical fertilizers for a sustainable agriculture practice.

Biological Control of White Rot in Apple Using Bacillus spp.

Apple white rot, caused by <i>Botryosphaeria dothidea</i>, is one of the important diseases in Korea. <i>B. dothidea</i> can cause pre- and postharvest decay on apple fruit as well as canker and dieback of apple trees. In this study, we isolated bacteria from the trunk of apple trees and tested their antagonistic activity against <i>B. dothidea</i>. Five bacterial isolates (23-168, 23-169, 23-170, 23-172, and 23-173) were selected that were most effective at inhibiting the mycelial growth of the pathogens. The isolate 23-172 was identified as <i>Bacillus amyloliquefaciens</i> and four isolates 23-168, 23-169, 23-170, and 23-173 were identified as <i>Bacillus velezensis</i> by RNA polymerase beta subunit (<i>rpoB</i>) and DNA gyraseA subunit (<i>gyrA</i>) gene sequencing. All isolates showed strong antagonistic activity against <i>B. dothidea</i> as well as <i>Colletotrichum fructicola</i> and <i>Diaporthe eres</i>. All isolates exhibited cellulolytic, proteolytic and phosphate solubilizing activities. In particular, two isolates 23-168, 23-169 were shown to significantly reduce the size of white rot lesions in pretreated apple fruits. These results will provide the basis for the development of a fungicide alternative for the control of white rot of apple.