Indole Acetic Acid Production Research Articles

Avaliação in vitro de bactérias promotoras de crescimento vegetal isoladas da orquídea cimbídio

Abstract The diversity of Cymbidium hybrids, and the growing commercialization of orchids, reinforces the need for sustainable production, and the bioprospecting of diazotrophic bacteria can demonstrate potential for agricultural use. The objective of this study was to evaluate in vitro diazotrophic bacteria, isolated from rhizospheric soil and tissues of the Cymbidium orchid, and to analyze the solubilization capacity of phosphorus, potassium and phytohormones production. Leaves, pseudobulbs and rhizospheric soil were isolated in five different semi-solid and semi-selective mediums, NFb, JNFb, LGI, JMV and FAM, in order to verify the biological nitrogen fixation capacity, through the indicative movie on the surface of the medium. The bacteria were grouped, according to their morphological characteristics, in a dendrogram, and selected at 75% similarity, testing them for the production of indoleacetic acid (IAA). The isolates that stood out in terms of the production of the aforementioned phytohormone were tested for their ability to solubilize phosphorus and potassium, usage phosphate rock powder, AO-15, and potassium, phonolite, as a source, respectively. The 66 isolated strains fixed nitrogen, and the 18 strains with 75% similarity produced AIA. The 8 strains that stood out in the production of indoleacetic acid, in the absence and presence of tryptophan, did does not solubilize phosphorus, with the strains UNIFENAS 100-589, UNIFENAS 100-591, UNIFENAS 100-600, UNIFENAS 100-604, being able to solubilize potassium, demonstrating the potential agricultural use of growth -promoting bacteria in the cultivation of the Cymbidium orchid.

Heavy Metal Co-Resistance with Antibiotics amongst Plant Growth Promoting Bacteria Isolates from Rhizosphere of Nypa Fruticans

Heavy metal co-resistance with antibiotics has the potential to amplify antimicrobial resistance genes in the environment, and this could have an impact on clinical settings. This study aimed to investigate the presence of heavy metal co-resistance with antibiotics among plant growth promoting bacterial isolates from the rhizosphere of Nypa fruticans. The heavy metals content of the water habouring the Nypa fruticans including copper(0.07mg/L), chromium (2.3 mg/L), lead (4.22 mg/L), iron (12.4 mg/L), cadmium (0.45 mg/L), nickel (3.12 mg/L), arsenic (0.47 mg/L) and zinc (5.37 mg/L) were above acceptable limits of WHO. A total of 10 bacteria including Bacillus subtilis, Bacillus cereus, Pseudomonas fluorescens, Klebsiella oxytoca, Serratia marcescens, Achromobacter denitrificans, Bulkholderia vietnamiensis and Azospirrilum brasilense, Azobacter vinelandii and Enterobacter aerogenes were isolated and identified to specie level using 16s RNA gene sequences, which showed above 95 % similarity with reference sequences from GenBank. The isolates showed high resistance to lead, chromium and zinc. Most of the isolates were resistant to streptomycin, ciprofloxacin and augmentin. Also, most of the isolates demonstrated positive growth promoting activities of indole acetic acid production, nitrogen fixation, siderophore production and phosphate solubilization. Pot trials on the effect of heavy metal and antibiotic tolerant bacteria on growth of beans (Phaseolus vulgaris l.) in heavy metal polluted soil revealed that beans treated with consortiumof all the isolates recorded high shoot and root length. Hence these isolates can be used for bioremediation of metal polluted site and as well act as plant growth promoting bacterial in agricultural system.

The potential of local orange peel-derived eco-enzymes in producing indole acetic acid

Background: Ecoenzymes, created from the fermentation of organic citrus waste, offer a sustainable method to produce Indole Acetic Acid (IAA), a phytohormone vital for plant growth. This study investigates the potential of these ecoenzymes in promoting sustainable agriculture. Objective: This study aims to evaluate the capacity of ecoenzymes derived from local citrus organic waste to synthesize IAA hormones. Methods: The ecoenzyme was extracted from fruit powders and centrifuged to separate the supernatant. One ml of ecoenzyme supernatant was then mixed with 2 ml of Salkowski reagent and incubated for 12 hours at room temperature in the dark to facilitate reaction. The presence and concentration of IAA were determined using spectrophotometry at a wavelength of 530 nm, while total protein levels were measured using the Warburg-Christian method. Results: ecoenzymes from local citrus sources contain IAA, with the highest concentration observed in sample 7A (30.26 µg/ml). The ecoenzyme exhibited favorable characteristics, including an average degree of acidity of 3.55, and the highest total protein content was found in sample 2A (144.277 mg/mL). Conclusion: Ecoenzymes from local orange peels successfully produce IAA, supported by fermentation-induced microbial activity and acidic conditions. This highlights their potential in sustainable agriculture.

The potential of local orange peel-derived eco-enzymes in producing indole acetic acid

Background: Ecoenzymes, created from the fermentation of organic citrus waste, offer a sustainable method to produce Indole Acetic Acid (IAA), a phytohormone vital for plant growth. This study investigates the potential of these ecoenzymes in promoting sustainable agriculture. Objective: This study aims to evaluate the capacity of ecoenzymes derived from local citrus organic waste to synthesize IAA hormones. Methods: The ecoenzyme was extracted from fruit powders and centrifuged to separate the supernatant. One ml of ecoenzyme supernatant was then mixed with 2 ml of Salkowski reagent and incubated for 12 hours at room temperature in the dark to facilitate reaction. The presence and concentration of IAA were determined using spectrophotometry at a wavelength of 530 nm, while total protein levels were measured using the Warburg-Christian method. Results: ecoenzymes from local citrus sources contain IAA, with the highest concentration observed in sample 7A (30.26 µg/ml). The ecoenzyme exhibited favorable characteristics, including an average degree of acidity of 3.55, and the highest total protein content was found in sample 2A (144.277 mg/mL). Conclusion: Ecoenzymes from local orange peels successfully produce IAA, supported by fermentation-induced microbial activity and acidic conditions. This highlights their potential in sustainable agriculture.

Inoculation of Endophytic Bacteria for Increasing Plant Height and Number of Rice Roots (Oryza sativa)

Four endophytic bacteria have been isolated from banana kluthuk plants and banana ambon. Previous study showed that they produce Indole Acetic Acid (IAA). This study aimed to analyze the effect of endophytic bacterial inoculation on plant height and the number of rice root. For this reason, two endophytic bacteria of each klutuk banana and ambon banana plants were cultured and examined for growth rate using a 600 nm spectrophotometer. Isolate growth was calculated every two hours for 16 hours of bacterial growth in NB media. Bacterial inoculation experiments on rice plants were carried out with five replications. This inoculation begun with germination of rice seeds until the radicle was observed. Then germinated rice seedlings were soaked in a bacterial suspension for 1 hour at room temperature. The results showed the exponential phase of all isolates was observed at 6 hours with shaking. Inoculation using A22 and A51 isolates significantly increases plant height, number of leaves. While, A22 isolate significantly increased the number of roots compared to the uninoculated plants (control). It supports the potential of endophytic bacteria from banana kluthuk and ambon plants.

Fungal endophytic species Fusariumannulatum and Fusariumsolani: identification, molecular characterization, and study of plant growth promotion properties

Research on endophytic fungi has gained significant interest due to their potential to enhance plant growth directly by producingphytohormones, solubilizing macronutrients, fixing nitrogen, or indirectly inhibiting phytopathogens growth by producing ammonia, siderophore, hydrogen cyanide, or extracellular enzymes, thereby acting as biocontrol agents. The present study aimed to isolate fungal endophytes from Alternantheraphiloxeroidesand evaluate their plant growth promotion and antimicrobial activity. In total, nine fungal endophytic strains were isolated from different parts of A. philoxeroides such as leaves, roots, and stems. The results demonstrate that the strains MEFAphS1 and MEFAphR3 exhibited positive plant growth promotion properties,including phosphate solubilization, and IAA (Indoleacetic acid) production, and ammonia production. The IAA production was highest for MEFAphS1, with a concentration of 46.635±1.04 µg/mL, while MEFAphR3 displayed the highest ammonia production (0.903±0.01 µg/mL). The phosphate solubilization index (PSI) is the maximum for MEFAphS1 (1.5±0.10). MEFAphS1 also exhibited antibacterial activity against Vibrio vulnificus, Streptococcus pneumoniae, and V.parahaemolyticus,with the most substantial inhibition zone observed against V.vulnificus(28±1 mm). In contrast, MEFAphR3 showed an inhibition zone of 8±1.53 mm against V. parahaemolyticus. Molecular identification revealed the identity of the isolates MEFAphS1 and MEFAphR3 as Fusariumsolaniand F.annulatum. These results thus confirm the possible applications of the fungal endophytes as plant biofertilizers and bio-enhancers to increase crop productivity.

Determination of Bioremediation Potentials and Plant Growth-Promoting Properties of Bacillus Species Isolated from The Rhizosphere of Dactylorhiza urvilleana

Industrial activities have been one of the biggest factors of environmental destruction by affecting natural resources for decades. Heavy metals, which are one of the greatest dangers especially for the biosphere, can be found in industrial waste. Heavy metals that enter agricultural areas through industrial wastewater cause heavy metals to accumulate in the soil after a certain period. These accumulated heavy metals become an important environmental problem, threatening the life of living beings due to their toxic properties. In soils contaminated with wastewater containing heavy metals, microorganism populations are severely damaged in terms of both number and diversity. This heavy metal accumulation in water and soil has become a global health threat. Alternative processes are needed in the fight against heavy metal pollution. Bioremediation activity, defined as the removal process of environmental pollutants through microorganisms and plants, has gained significant importance in recent years. In our study, the tolerance potentials of Bacillus species isolated from the rhizosphere of Dactylorhiza urvilleana (Steudel) Bauman in the Ovit plateau of Rize province to metals (such as copper, lead, zinc, iron and silver) were investigated. In addition, plant growth promoting Indole Acetic Acid (IAA) production, phosphate dissolution, and ACC (1-Aminocyclopropane-1-Carboxylic acid) deaminase production were determined. It was determined that the isolated Bacillus species had a wide pH growth range and some Bacillus species were salt tolerant. The results showed that Bacillus species have bioremediation potential and plant growth promoting properties. It is thought that the bacteria isolated from the study can be used to make areas with heavy metal pollution suitable for plant cultivation and act as plant growth promoters in these areas. These bacteria strains are planned to be used as cheaper and more effective methods in studies in agriculture or areas with heavy metal pollution.

Microbiolization with Bacillus sp. in irrigated rice seed positively impacts physiological and phytosanitary quality

Seed treatment is an important practice for reducing pathogens. The microbiolization technique has been used to provide economic and environmental benefits, starting with the selection of microorganisms and the identification of their mechanisms of action. In this sense, Bacillus sp. has stood out, having the capacity to promote growth and phytopathogenic control of several important crops such as rice. This study was conducted aiming to evaluate the protective effects of inoculation with six isolates of Bacillus sp. in rice seeds. Germination, germination speed index, shoot fresh weight, root fresh weight, seeding size, indoleacetic acid production, cellulase production, and antagonist phytosanitary analysis were evaluated. Our results revealed the best efficacy of isolate 47b in the tests of rice seed germination, root fresh weight, shoot fresh weight, seedling size, indoleacetic acid, and cellulase index. The 47b isolate, as it expressed better results in the previous tests, was subjected to different pHs, with pH 4, pH 6, and pH 8 being more efficient as a control measure (in the antagonism test) against Curvularia sp. This 47b isolate also performed very efficiently against Colletotrichum sp. at the pH4 and Macrophomina sp. at the pH 6. Our findings revealed the potential of the isolate 47b as a plant protectant against relevant phytopathogens and demonstrated its potential as a plant growth promoter.

NIT24 and NIT29-mediated IAA synthesis of Xanthomonas oryzae pv. oryzicola suppresses immunity and boosts growth in rice.

Auxin plays a pivotal role in the co-evolution of plants and microorganisms. Xanthomonas oryzae pv. oryzicola (Xoc) stands as a significant factor that affects rice yield and quality. However, the current understanding of Xoc's capability for indole 3-acetic acid (IAA) synthesis and its mechanistic implications remains elusive. In this study, we performed a comprehensive genomic analysis of Xoc strain RS105, leading to the identification of two nitrilase enzyme family (NIT) genes, designated as AKO15524.1 and AKO15829.1, subsequently named NIT24 and NIT29, respectively. Our investigation unveiled that the deletion of NIT24 and NIT29 resulted in a notable reduction in IAA synthesis capacity within RS105, thereby impacting extracellular polysaccharide production. This deficiency was partially ameliorated through exogenous IAA supplementation. The study further substantiated that NIT24 and NIT29 have nitrilase activity and the ability to catalyse IAA production invitro. The lesion length and bacterial population statistics experiments confirmed that NIT24 and NIT29 positively regulated the pathogenicity of RS105, suggesting that NIT24 and NIT29 may regulate Xoc invasion by affecting IAA synthesis. Furthermore, our analysis corroborated mutant strains, RS105_ΔNIT24 and RS105_ΔNIT29, which elicited the outbreak of reactive oxygen species, the deposition of callose and the upregulation of defence-related gene expression in rice. IAA exerted a significant dampening effect on the immune responses incited by these mutant strains in rice. In addition, the absence of NIT24 and NIT29 affected the growth-promoting effect of Xoc on rice. This implies that Xoc may promote rice growth by secreting IAA, thus providing a more suitable microenvironment for its own colonization. In summary, our study provides compelling evidence for the existence of a nitrilase-dependent IAA biosynthesis pathway in Xoc. IAA synthesis-related genes promote Xoc colonization by inhibiting rice immune defence response and affecting rice growth by increasing IAA content in Xoc.

Analyzing Single and Combined Cultures of Plant Growth-Promoting Rhizobacteria Isolates from Afghanistan as a Potential Biofertilizer for Rice Growth and Development

Developing multi-functional, environmentally friendly biofertilizers can help reduce chemical fertilizer usage. This study examined single and combined application effects of four plant growth-promoting rhizobacteria (PGPR) strains: AF124 (Rhizobium daejeonense), AF74 (Enterobacter cloacae), AF96 (Pseudomonas putida), and AF42 (Enterobacter cloacae), isolated from alkaline salt-stressed soils from Afghanistan. Physiological features such as nitrogen (N2) fixation, indole-3-acetic acid (IAA), organic acid production, and P and K solubilization of bacteria in single or combined cultures in vitro were examined. A single application of AF124 and AF74 showed significantly higher IAA production than the combined application of dual, triple, and quadruple PGPR treatments. Regarding acetylene reduction activity, an N2-fixation activity indicator, a single application of AF124 showed the highest value, followed by a triple application of AF124 + AF96 + AF42. The P-solubilization activity and organic acid production were lower in the single application of AF124 but higher with other strains in the combined applications, which resulted in the secretion of multiple organic acids into the medium. The highest solubilized K value was obtained from the quadruple application compared to other treatments. In the rice inoculation test, all single and combined PGPR treatments increased its growth parameters, such as root length and root and shoot dry biomass. The present results indicate that these four PGPR strains can potentially contribute to developing multi-functional bio-fertilizer formulations.

Bio-management of Fusarium wilt of tomato (Fusarium oxysporum f.sp. lycopersici) with multifacial Trichoderma species

Fusarium oxysporum f.sp. lycopersici (FOL), the incitant of the Fusarium wilt of tomato, is a highly damaging and prevalent disease in the majority of tomato growing areas. Keeping into consideration of high disease occurrence and incidence of FOL in tomato crop, the present investigation was undertaken to develop an effective bio-management approach to combat this disease. Initially, the studies were conducted to evaluate six multi-facial biocontrol isolates of Trichoderma species viz., Trichoderma harzianum AMUTH-1, T. harzianum AMUTH-2, T. harzianum AMUTH-3, T. asperellum (= T. viride) AMUTV-1, T. asperellum AMUTV-3 and T. virens (= Gliocladium virens) AMUTS-1 against FOL in vitro. Among these antagonists, T. harzianum AMUTH-1 and T. asperellum AMUTV-3 exhibited the maximum inhibitory effect while T. virens AMUTS-1 was recorded as the least effective Trichoderma isolate against FOL in vitro. Interestingly, T. harzianum AMUTH-1 and T. asperellum AMUTV-3 were found to produce indole acetic acid, siderophore and possess high enzymatic activities (cellulase, chitinase, ligninase and protease) in vitro. Further, pot trials were conducted and the chemical fungicide, carbendazim was used to compare the effectiveness of Trichoderma isolates. Pot trials also verified the efficacy of T. harzianum AMUTH-1 with 9–28% enhancement in the plant-growth parameters and 15–21% biomass production, and 88% decrease in the soil population of FOL. The effect of T. harzianum AMUTH-1 was also at par with fungicides, carbendazim.

Probing the potential of salinity-tolerant endophytic bacteria to improve the growth of mungbean [Vigna radiata (L.) Wilczek

Soil salinity is one of the major limiting factors in plant growth regulation. Salinity-tolerant endophytic bacteria (STEB) can be used to alleviate the negative effects of salinity and promote plant growth. In this study, thirteen endophytic bacteria were isolated from mungbean roots and tested for NaCl salt-tolerance up to 4%. Six bacterial isolates, TMB2, TMB3, TMB5, TMB6, TMB7 and TMB9, demonstrated the ability to tolerate salt. Plant growth-promoting properties such as phosphate solubilization, indole-3-acetic acid (IAA) production, nitrogen fixation, zinc solubilization, biofilm formation and hydrolytic enzyme production were tested in vitro under saline conditions. Eight bacterial isolates indicated phosphate solubilization potential ranging from 5.8-17.7 μg mL-1, wherein TMB6 was found most efficient. Ten bacterial isolates exhibited IAA production ranging from 0.3-2.1 μg mL-1, where TMB7 indicated the highest potential. All the bacterial isolates except TMB13 exhibited nitrogenase activity. Three isolates, TMB6, TMB7 and TMB9, were able to solubilize zinc on tris-minimal media. All isolates were capable of forming biofilm except TMB12 and TMB13. Only TMB2, TMB6 and TMB7 exhibited cellulase activity, while TMB2 and TMB7 exhibited pectinase production. Based on in vitro testing, six efficient STEB were selected and subjected to the further studies. 16S rRNA gene sequencing of efficient STEB revealed the maximum similarity between TMB2 and Rhizobium pusense, TMB3 and Agrobacterium leguminum, TMB5 and Achromobacter denitrificans, TMB6 and Pseudomonas extremorientalis, TMB7 and Bradyrhizobium japonicum and TMB9 and Serratia quinivorans. This is the first international report on the existence of A. leguminum, A. denitrificans, P. extremorientalis and S. quinivorans inside the roots of mungbean. Under controlled-conditions, inoculation of P. extremorientalis TMB6, B. japonicum TMB7 and S. quinivorans TMB9 exhibited maximum potential to increase plant growth parameters; specifically plant dry weight was increased by up to 52%, 61% and 45%, respectively. Inoculation of B. japonicum TMB7 displayed the highest potential to increase plant proline, glycine betaine and total soluble proteins contents by 77%, 78% and 64%, respectively, compared to control under saline conditions. It is suggested that the efficient STEB could be used as biofertilizers for mungbean crop productivity under saline conditions after field-testing.

Endophytic Bacterium Flexivirga meconopsidis sp. nov. with Plant Growth-Promoting Function, Isolated from the Seeds of Meconopsis integrifolia.

Strain Q11T of an irregular coccoid Gram-positive bacterium, aerobic and non-motile, was isolated from Meconopsis integrifolia seeds. Strain Q11T grew optimally in 1% (w/v) NaCl, pH 7, at 30 °C. Strain Q11T is most closely related to Flexivirga, as evidenced by 16S rRNA gene analysis, and shares the highest similarity with Flexivirga aerilata ID2601ST (99.24%). Based on genome sequence analysis, the average nucleotide identity and digital DNA-DNA hybridization values of strains Q11T and D2601ST were 88.82% and 36.20%, respectively. Additionally, strain Q11T showed the abilities of nitrogen fixation and indole acetic acid production and was shown to promote maize growth under laboratory conditions. Its genome contains antibiotic resistance genes (the vanY gene in the vanB cluster and the vanW gene in the vanI cluster) and extreme environment tolerance genes (ectoine biosynthetic gene cluster). Shotgun proteomics also detected antibiotic resistance proteins (class A beta-lactamases, D-alanine ligase family proteins) and proteins that improve plant cold tolerance (multispecies cold shock proteins). Strain Q11T was determined to be a novel species of the genus Flexivirga, for which the name Flexivirga meconopsidis sp. nov. is proposed. The strain type is Q11T (GDMCC 1.3002T = JCM 36020 T).

Endophytic bacteria Klebsiella spp. and Bacillus spp. from Alternanthera philoxeroides in Madiwala Lake exhibit additive plant growth-promoting and biocontrol activities

BackgroundThe worldwide increase in human population and environmental damage has put immense pressure on the overall global crop production making it inadequate to feed the entire population. Therefore, the need for sustainable and environment-friendly practices to enhance agricultural productivity is a pressing priority. Endophytic bacteria with plant growth-promoting ability and biocontrol activity can strongly enhance plant growth under changing environmental biotic and abiotic conditions. Herein, we isolated halotolerant endophytic bacteria from an aquatic plant, Alternanthera philoxeroides, from the polluted waters of Madiwala Lake in Bangalore and studied their plant growth promotion (PGP) and biocontrol ability for use as bioinoculant. ResultsThe isolated bacterial endophytes were screened for salt tolerance ranging from 5 to 15% NaCl concentration. Klebsiella pneumoniae showed halotolerant up to 10% NaCl and Bacillus amyloliquefaciens and Bacillus subtilis showed up to 15%. All three strains demonstrated good PGP abilities such as aminocyclopropane-1-carboxylic acid (ACC) deaminase activity, phosphate solubilization, ammonia production, and nitrogen fixation. In addition, K. pneumoniae also exhibited high indoleacetic acid (IAA) production (195.66 ± 2.51 µg/ml) and potassium solubilization (2.13 ± 0.07 ppm). B. amyloliquefaciens and B. subtilis showed good extracellular enzyme production against cellulase, lipase, protease, and amylase. Both the isolates showed a broad spectrum of antimicrobial activity against the tested organisms. The optimization of IAA production by K. pneumoniae was done by the response surface methodology (RSM) tool. Characterization of IAA produced by the isolate was done by gas chromatography-mass spectrometry (GCMS) analysis. The enhanced plant growth-promoting ability of K. pneumoniae was also demonstrated using various growth parameters in a pot trial experiment using the seeds of Vigna unguiculata. ConclusionThe isolated bacterial endophytes reported in this study can be utilized as PGP promotion and biocontrol agents in agricultural applications, to enhance crop yield under salinity stress. The isolate K. pneumoniae may be used as a biofertilizer in sustainable agriculture and more work can be done to optimize the best formulations for its application as a microbial inoculant for crops.

Assembly of Tomato Rhizobacteria from Different Functional Groups Improves Seedling Photosynthesis and Growth

The rhizosphere harbors abundant plant growth-promoting rhizobacteria (PGPR) that are vital for plant health. In this study, we screened growth-promoting bacteria from tomato rhizosphere soil, verified their functions, and constructed the optimal combination of growth-promoting bacteria for promoting tomato growth. Furthermore, the effects of these bacteria on various physiological and biochemical parameters of tomato plants were evaluated. A total of 36 strains of rhizobacteria were isolated from tomato rhizosphere soil and their abilities to produce indole-3-acetic acid (IAA), solubilize phosphate and iron carriers were assessed. The bacterial strains with the highest capacities for IAA production (R62, R317), phosphate solubilization (R41, R219), and siderophore production (R25, R325) were selected to form three bacterial combinations: R62 + R219 + R317 + R325 (T1), R62 + R325 (T5), and R317 + R325 (T8). Fifteen days after inoculation, all three combinations showed a stimulatory effect on seedling growth compared to the un-inoculated control. Inoculation with T1, T5 and T8 increased the seedling vigor index by 173.7%, 204.1%, and 168.7%, respectively. Compared to the un-inoculated control, the T1 combination increased the activities of polyphenol oxidase, peroxidase, and the net photosynthetic rate by 132.7%, 18.7%, 58.5%, and upregulated the relative expression levels of the photosynthetic assimilation-related genes RbcL, RbcS, FBPase and FDA by 22.2-, 6.6-, 1.95-, and 2.0-fold, respectively. Our findings provide a potential for constructing rhizobacterial combinations of different functional groups for improving crop growth.

Identification of plant growth promoting antagonistic bacteria against blast disease of rice

This study aimed to isolate and identify plant growth-promoting bacteria from rhizosphere of rice plants that exhibit antagonistic properties against Magnaporthe oryzae, the causal agent of blast disease. Bacteria were isolated from the surface of rice leaves, stems, and soil attached to the roots. The antagonistic activity of the isolated bacteria was assessed using a dual culture method, and identities were determined through 16S rDNA sequencing. To evaluate their growth-promoting abilities, assays were conducted to measure indole acetic acid (IAA) production, siderophore secretion, hydrogen cyanide (HCN) production, and phosphate solubilization. The results revealed that Bacillus subtilis, identified as BDISO_01R, exhibited antagonistic behavior and the maximum inhibition of M. oryzae (81.00%) was obtained by bacterial isolate BDISO-01R. Additionally, eight bacterial isolates demonstrated IAA production, sixteen isolates produced siderophores, and nine isolates displayed phosphate solubilization capability. This research sheds light on the diverse microbial arsenal that can potentially promote rice growth while combating blast disease. Bangladesh J. Nuclear Agric, 37(1): 63-79, 2023

Functional Characterization of Rhizobia for Multiple Plant Growth Promoting Activities

This research focuses on the functional characterization of 19 rhizobia strains isolated from Southern Rajasthan's Udaipur and Dungarpur districts, with an emphasis on their multiple Plant Growth Promoting (PGP) activities. Through a series of tests encompassing Indole-3-Acetic Acid (IAA) production, siderophore production, phosphate solubilization, ammonia production, and hydrogen cyanide (HCN) production, this study elucidates the diverse PGP potential of these rhizobia strains. The results showcase variations in IAA production, highlighting their ability to enhance root development and overall plant growth, while also revealing strains capable of siderophore production, indicating potential iron uptake facilitation. Furthermore, some strains exhibit phosphate solubilization, ammonia production, and HCN production capabilities, signifying their potential to improve nutrient availability and protect plants from pathogens. These findings underscore the promise of harnessing the PGP activities of these rhizobia strains for sustainable agricultural practices in Southern Rajasthan and similar agroecological regions, with implications for enhanced crop yields and soil health.

Potential of a novel endophytic diazotrophic Serratia sp. Wed4 for pyrene biodegradation

Endophytic diazotrophic Serratia sp. Wed4 with high nitrogenase activity (1260.9 ± 8.3 nmol C2H4 mL−1h−1) was isolated from Glycine max Linn growing in PAH contaminated soil for improving PAH removal and crop growth. Strain Wed4 biodegraded 37.0% of pyrene within 14 d via phthalate pathway in vitro and could biodegraded other PAHs with 2–5 rings effectively. Its capabilities on promoting crop growth included indole acetic acid (IAA) production (30.8 ± 3.3 μg mL−1), iron carrier production (A/Ar = 0.841 ± 0.002), inorganic phosphate dissolution (D/d = 1.184 ± 0.032) and organic phosphate dissolution (D/d = 1.154 ± 0.025). Strain Wed4 successfully colonized in barley tissues (>104 CFU g−1 FW), significantly promoted barley growth and nitrogen nutrition, reduced pyrene residues especially in shoots. Under sufficient nitrogen condition, strain Wed4 significantly promoted the dry weight of barley by 18.9%–33.9%, and decreased the pyrene residues by 46.4% in shoots and by 32.1% in roots. Meanwhile, under the deficient nitrogen condition, strain Wed4 significantly promoted the dry weight of barley by 40.1%–63.3% and decreased the pyrene residues by 39.0% in shoots and by 28.0% in roots. The pyrene contents were significantly negatively correlated with the total nitrogen contents in barley tissues, suggesting that nitrogen fixation of strain Wed4 also stimulated the pyrene removal. Based on its performance, Serratia sp. Wed4 provided a great potential to increasing crop yield and reducing PAH pollution in nitrogen deficient soils.

Temporal and spatial dynamics and functional metabolism of dark septate endophytes of Gymnocarpos przewalskii Maxim. in Northwest Desert, China

In extreme habitats, plants can survive mutually with their beneficial colony partners. How dark septate endophytes (DSE) assist the relict plant Gymnocarpos przewalskii survive in extremely desert environment and maintain the stability of the ecosystem remains unclear. Studying distribution, seasonal changes and functional physiological responses of DSE colonized in roots of G. przewalskii can help understand symbiosis mechanism of these endophytes associated to relict plants in extremely arid desert environments. DSE colonization, species diversity and soil properties of G. przewalskii were measured in Anxi and Minqin sites, Northwest China in July, September and December 2019. Subsequently, the functional metabolism of DSE strain was measured, and the response of DSE strain to drought stress was performed in vitro. DSE hyphal colonization (23.3 % - 39.2 %) and DSE isolation frequency (6.0 % - 27.6 %) varied sharply among seasons and sites. Soil alkaline phosphatase, nitrate nitrogen and total phosphorus were main factors affecting the DSE composition. Twenty-six DSE isolates produced indole-3-acetic acid (IAA) in the medium, while 50 % of DSE showed a potential for IAA production in L-tryptophan-dependent. Additionally, the composition of functional metabolites of DSE strains varied greatly with different drought levels and DSE isolates, which may indirectly reflect the complementarity between different strains in helping hosts cope with drought stress. This study confirmed the temporal and spatial dynamics and growth-promoting and drought-tolerant potential of DSE community in desert environment, and provided a new perspective for exploring the survival strategy and vegetation protection of desert relict plants.

Isolation and Molecular Identification of Indole Acetic Acid-Producing Endophytic Bacteria from Daun Dewa Plant (Gynura divaricata (L.) DC)

Indole acetic acid (IAA) is an auxin hormone that can regulate plant growth and development. Bacteria produce IAA through L-tryptophan metabolism. The purpose of this study was to determine the ability of endophytic bacteria isolated from Daun Dewa plants to produce IAA to increase the germination and growth of tomato seedlings. Isolation of endophytic bacteria was carried out by sterilizing plant surfaces. The production of IAA is done by adding L-tryptophan precursors. The results showed that there were six endophytic bacteria, and three isolates of them have the potential to produce IAA, namely: AD1.1, UD1.1, and UD2.1. The highest IAA concentration was produced by isolate AD1.1. Growth in sprouts is significantly influenced by the concentration of IAA; the higher the concentration of IAA, the longer the shoots and the roots. Based on the 16S rRNA gene sequence, these isolates belong to the genus Klebsiella.