IAA Production Research Articles

Characterization and application of nitrogen-fixing and indole-3-acetic acid producing bacteria A13 in Oil Palm (Elaeisguineensis Jacq.) seedling

Oil palm plantations have a good prospect in Indonesia. One of the efforts to improve the productivity of oil palm plantation is the application of bacteria as biological fertilizer. The research was conducted to characterize and apply the nitrogen-fixing and indole-3-acetic acid producing bacteria in oil palm seedlings. The bacteria was isolated from soil samples which taken from Taman Nasional Bukit Dua Belas (TNBD) Jambi. Nitrogen free bromthymol blue (NFB) is used as media for nitrogen-fixing bacterial isolation. Selected isolate named A13 had an ability to form white pellicle on the surface of the semisolid medium, increased the pH, and changed the color of medium from green to blue Isolate A13 was identified as Gram-negative bacteria and had a rods shape. Analysis of 16S rRNA gene sequence showed that isolate A13 had a similarity with Pseudochrobactrum assacharolyticum. Hypersensitivity assay on tobacco leaves showed that isolate A13 was not a pathogen. During 48 hours of incubation, isolate A13 produced a maximum of IAA at the 24th hour of incubation. Isolate A13 produced 0.675 ppm of ethylene/hour in Acetylene Reduction Assay and 69,839 ppm of IAA in HPLC methods. This was the first report on nitrogen fixation and IAA production by Pseudochrobactrum assacharolyticum and its application in the soil of oil palm seedlings. Application of isolate A13 in oil palm seedling increased significantly the number of lateral roots, stem diameter, and height of plants

Genetic and physiological diversity of white Spanish broom (Chamaecytisus albus) endophytes.

Chamaecytisus albus (Spanish broom) is a legume shrub that can be found in only one natural locality in Poland. This specimen is critically endangered; therefore, different actions focusing on protection of this plant in the natural habitat are undertaken, and one of them involves studies of the population of Chamaecytisus albus bacterial endophytes, which in the future could be used as bioprotectants and/or biofertilizers. A collection of 94 isolates was obtained from Spanish broom nodules, and the physiological and genetic diversity of these strains was studied. A few potentially beneficial traits were detected, i.e. secretion of cellulases (66 isolates), production of siderophores (60 isolates), phosphate solubilization (25 isolates), and production of IAA (58 isolates), indole (16 isolates), or HCN (3 isolates). Twenty-nine of the 94 tested isolates were able to induce the development of root nodules in plants grown in vitro and can therefore be assumed as Chamaecytisus albus symbionts. Genome fingerprinting by BOX-PCR, as well as gyrB and nodZ gene sequencing revealed a great genetic diversity of specimens in the collection. The symbiotic isolates were classified in different clades, suggesting they could belong to different species, however, most of them revealed sequence similarity to Bradyrhizobium genus.

Coastal Ecosystems as Sources of Biofertilizers in Agriculture: From Genomics to Application in an Urban Orchard

Pantoea agglomerans RSO7, a rhizobacterium previously isolated from Spartina maritima grown on metal polluted saltmarshes, had demonstrated good plant growth promoting activity for its host halophyte, but was never tested in crops. The aims of this study were: (1) testing PGP activity on a model plant (alfalfa) in vitro; (2) testing a bacterial consortium including RSO7 as biofertilizer in a pilot experiment in urban orchard; and (3) identifying the traits related to PGP activities. RSO7 was able to enhance alfalfa growth in vitro, particularly the root system, besides improving plant survival and protecting plants against fungal contamination. In addition, in a pilot experiment in urban orchard, a consortium of three bacteria including RSO7 was able to foster the growth and yield of several winter crops between 1.5 and 10 fold, depending on species. Moreover, the analysis of chlorophyll fluorescence revealed that photosynthesis was highly ameliorated. Genome analysis of RSO7 depicted the robustness of this bacterial strain which showed resilience to multiple stresses (heat, cold, UV radiation, several xenobiotics). Together with wide metabolic versatility, genes conferring resistance to oxidative stress were identified. Many genes involved in metal resistance (As, Cu, Ni, Co, Zn, Se, Te) and in tolerance toward high osmolality (production of a battery of osmoprotectans) were also found. Regarding plant growth promoting properties, traits for phosphate solubilization, synthesis of a battery of siderophores and production of IAA were detected. In addition, the bacterium has genes related to key processes in the rhizosphere including flagellar motility, chemotaxis, quorum sensing, biofilm formation, plant-bacteria dialog, and high competitiveness in the rhizosphere. Our results suggest the high potential of this bacterium as bioinoculant for an array of crops. However, the classification in biosecurity group 2 prevents its use according to current European regulation. Alternative formulations for the application of the bioinoculant are discussed.

ISOLATION AND IDENTIFICATION OF BIOFLOCCULANT-PRODUCING BACTERIA FROM CASSAVA CULTIVATED SOIL OF VIET NAM

Microorganisms are found everywhere in the environment and play a leading role in countless natural processes, and amongst them, soil microorganisms play important roles in plant performance by improving mineral nutrition. Soil bacteria possess different biological activities; for example, producing bioactive compounds such as bioflocculant which makes soil smoother and more breathable, as plant growth stimulants or compounds with antibiotic activity. Beside this, the same soil bacteria could also be able to fix atmospheric nitrogen, converting it into the form that plants can use. In order to make a microbial formula from local bacteria capable of producing bioflocculant as well as IAA and fixing nitrogen towards microbial organic fertilizer production for application in cassava cultivation, the bacteria were isolated from cassava cultivated soils and screened for above mention activities. From 37 cassava root and cassava cultivated soil samples collected at different provinces in the North, Central and South regions of Vietnam, 80 strains of bacteria with bioflocculant activity over 50% were screened. In which 3 strains (ĐQT1 Po6, ĐTAN6 Po2 and ĐSBV Po1) possess not only high bioflocculant and IAA producing capacities, but also the ability to fix atmospheric nitrogen. The flocculant rate of these strains was 80÷90% and can produce 6÷11 µg/mL IAA. The selective strains were identified by having an analysis of 16S rRNA gene sequence. The obtained results showed that the 16S rRNA sequence of ĐQT1 Po6 was 100% identifiable to corresponding sequence of Bacillus aryabhattai FORT 21 (Ass.No MG561348.1); and the 16S rRNA sequences of ĐTAN6 Po2 and ĐSBV Po1 had 100% homology with those of Enterobacter sp. (Ass.No KJ184880.1) and Bacillus subtilis SAN1.5 (Ass.No KX098457.1), respectively. These strains are potential candidates as perfect inoculant for biofertilizer.

Identification of Sago-Pulp Amylolytic Bacteria and Its Utilization for Granulated Fertilizer

Previous research stated that bacteria isolated from sago waste from the traditional sago industry in Palopo had the potency to produce amylase. This study aims to confirm the ability of bacteria isolated from sago pulp waste to produce amylase, evaluate the ability of these amylolytic bacteria to produce IAA fix nitrogen, identify selected bacteria, and apply selected bacteria into granules biofertilizers. Bacteria were isolated from sago pulp waste and grown on a 1% starch agar medium. The amylolytic activity was analyzed qualitatively using iodine and quantitatively using the 3,5-Dinitrosalicylic Acid (DNS) method at pH 6. Amylolytic bacteria were analyzed for IAA production using Salkowsky reagent and nitrogen fixation ability through the Serra Kit method. Potential bacteria were identified based on the similarity of the 16S rDNA sequence. The selected bacteria were grown in a 10mL NB medium, and then bacteria were inoculated and air-dried to obtain the granules. The selected bacteria were put into granules and re-isolated using the total plate count (TPC) method. Eight amylolytic bacteria were obtained from sago pulp waste. L1E isolate had the highest amylolytic activity of 1.228 U.mL-1, and L1D isolate had the highest IAA production of 69.8 g.mL-1. Isolate L1E was identified as Alcaligenes faecalis with a 99.45% similarity index, and L1D was identified as Serratia surfactantfaciens with a 99.09% similarity index. Isolate L2G was identified as Alcaligenes aquatilis with a similarity index of 99.8% of the 16S rDNA sequence. The viability of bacteria from granules was 1.41 x 108 CFU.g-1. Keywords: Amylase enzyme, amylolytic bacteria, granulated fertilizer.

Screening of cadmium resistant bacteria and their effects on plant growth promotion and remediation in soil

In order to investigate the remediation effect of the microbial-plant joint system on soil heavy metal Cd pollution, we carry out strain screening and pot experiment to explore the effects of plant growth-promoting bacteria on the accumulation capacity of ryegrass, soil physical and chemical properties and heavy metal speciation. The results show that the microscopic morphology of Burkholderia sp.YXL1 is pale yellow, rod-shaped and smooth edge with an average length of 5 μm, and it possesses strong growth-promoting ability and can tolerate cadmium content about 250 mg/L. The capacity of IAA production, siderophore and phosphate-solubilizing substances are 31.56 mg/L, 0.89 and 46.18 mg/L, respectively. In the <italic>YXL</italic>1-ryegrass joint remediation system, the organic matter and available phosphorus content in the soil are significantly increased by 4.08 g/kg and 2.54 mg/kg, respectively. The contents of weak acid extractable Cd and reducible Cd in the soil reach 16.25% and 12.53%, respectively. Compared with the control group, the ability of ryegrass to extract Cd from the soil is 2.76 times higher than that of the ryegrass treatment. The results also show that the Cd content of the cultivated layer soil is below the risk screening value (<0.3 mg/kg) in the Soil Environmental Quality Agricultural Land Soil Pollution Risk Control Standard (GB 15618—2018) to realize the safe use of agricultural land in the <italic>YXL</italic>1- ryegrass joint remediation system after 4 years.

Isolation and characterization of plant growth-promoting endophytic bacteria of wild legumes growing on sandy soils of Binh Thuan province, Vietnam

The roots of two legume species (Tephrosia purpurea and Tephrosia villosa) that grew wild on dry sandy soils of Binh Thuan province were sources for isolating plant growth-promoting endophytic bacteria. Semi-solid LGI medium was used for the isolation of nitrogen-fixing bacteria from root extracts. All bacterial isolates isolates were evaluated for their ability to solubilize calcium orthophosphate on solid NBRIP medium and their ability to produce IAA in Burk's liquid medium supplemented with 100 mg/L tryptophan. The possibilities of nitrogen fixation, phosphate solubilization and IAA synthesis were all quantitative examined by colorimetric method. Twenty-two bacterial isolates of T. purpurea and 18 isolates of T. villosa were capable of nitrogen fixation in the range of 1.94 to 2.81 mg/L NH4+, whereas only 18 isolates of T. purpurea and 16 isolates of T. villosa showed phosphate solubilization in the range of 12.30 – 48.90 mg/L P2O5, and IAA production in the range of 0.38 – 12.72 mg/L. Sixteen outstanding bacterial isolates of the two legume species were identified by MALDI-TOF technique. The results showed that 13 isolates had high similarity with five bacterial genera including Klebsiella, Cronobacter, Enterobacter, Burkholderia, and Bacillus with score values in the range of 2.070 – 2.411.

Isolation and Screening of Multifunctional Plant Growth Promoting Rhizobacteria from Rhizopshere of Different Crop Fields

Rhizospheric bacteria are naturally occurring soil microbes that are aggressively found in the plant rhizosphere, at root surface and in association with roots. They give satisfactory benefit plants by several mechanisms such as nitrogen fixation, phosphate solubilization, potassium decomposition, IAA production, antagonism against phytopathogenic microorganisms by production of siderophore, antibiotics and cell wall degrading enzymes. The total number of beneficial bacteria were isolated from different rhizospheric soil in agricultural lands. The isolated bacterial strains were screened for their plant growth promoting factors such as production of ammonia, siderophore, cellulase, chitinase, and pectinase enzyme. All of the isolates produced ammonia and 79% of the isolates produced siderophore on chrome azurole S agar plates. Furthermore, the bacterial isolates produced cell wall degrading enzyme; pectinase (69%), cellulase (94%), chitinase (51%), amylase (61%) and glucanase enzyme (59%) on agar plate method. The isolates also produced auxin type plant hormone (IAA), all the isolates produced IAA and the highest IAA producing strain is W1 and the produce amount was 21.91mg/L. Among the isolated bacteria, only two strains could produce HCN with the use of Feigl-Anger paper method. The recent study suggests that the use of these PGPR isolates as inoculants might be a promising source for sustainable agricultural use.

Plant growth promoting actinobacteria from rhizosphere soils of black pepper in Wayanad

Actinobacteria isolated from the rhizosphere soils of black pepper comprising both flood affected and non-flood affected areas of Wayanad district. Among different soil samples analysed, Puttad (Ptd) recorded significantly superior actinobacterial population on starch casein aga, Kenknight &amp; Munaier’s agar and actinomycetes isolation agar. Actinobacterial colonies could not be detected in any of the flooded soil samples on any medium, even at a dilution of 10-1, except in Meppadi soil, which recorded a low population of 0.3x101cfu g-1 soil. Starch casein agar is best media to isolate actinobacteria from soil samples compared to other two media. The cultural, morphological and biochemical characterization of thirty-five isolates was carried out. Further the isolates were evaluated for their plant growth promoting traits such as IAA production, nitrogen fixation, P, K and Zn solubilization. The isolates Ptd-A and Amb-C were found to be significantly superior to all other isolates, with IAA production of 15.9 g ml-1 and 15.38 g ml-1 respectively. The four isolates viz. Ptd-A, Ptd-E, Ptd-B and Ptr-A recorded significantly superior nitrogen fixation and the phosphate solubilized was significantly higher in Ptd-E, Ptd-D, Ptr-E, Ptd-A and Ptr-A, as compared to other isolates. All isolates were negative to K and Zn solubilization. Based on in vitro evaluations, three isolates were shortlisted (Ptd-A, Ptd-E and Ptr-A) and subjected to in vivo evaluation for growth promotion in black pepper (variety Panniyur 1). Rooted plants of black pepper were raised in sterile potting mixture. Bioinoculants applied at the time of planting and 45 days after planting. The PGPR Mix-1 and Organic Package of Practices Recommendations (2017) were used for comparison with the microbial inoculants along with control. In the in-planta experiment, biometric characters were recorded at monthly intervals, up to five months. The actinobacterial treatment, T1: Ptd-E, T2: Ptd-A and T3: Ptr-A showed significant increase in shoot length, number of leaves and internode length throughout the growth period from planting to five MAP. Significantly higher root growth was observed in treatment T2: Ptd-A, with significantly higher root volume, fresh and root weight. The potential actinobacteria were identified Ptd-A and Ptr-A as Streptomyces sp. and Ptd-A as Actinobacteria bacterium using 16S r RNA gene sequencing.

Morphological, Biochemical and Molecular Characterization of Rhizobia of Faba Bean Plants Grown in North Nile Delta Egypt.

&lt;b&gt;Background and Objective:&lt;/b&gt; Rhizobia are bacteria including genes codes for enzymes involved in the fixing of the atmospheric nitrogen. A set of twenty rhizobial isolates were studied to determine their morphological, biochemical, molecular characteristics using the 16S rRNA gene in addition to assess their growth and symbiotic performance. &lt;b&gt;Materials and Methods:&lt;/b&gt; Rhizobial isolates were isolated from root nodules of &lt;i&gt;Vicia faba &lt;/i&gt;L. plants. The isolates were morphologically characterized by determining cell shapes, size, Gram stain reaction, motility, sporulation, bacterial growth performance was determined by IAA production and biomass density. Symbiotic performance was measured by evaluation of nodulation status and shoot/root dry weight. Sequencing of 16S rRNA and phylogenetic analysis were done for the five promising isolates. Statistical analysis was performed using a one-sample Student t-test. &lt;b&gt;Results:&lt;/b&gt; Only five rhizobial isolates (Rh 32, Rh 6-A, Rh 3-4, Rh RL3 and Rh 8-A) were selected according to their growth and symbiotic performance and subjected to further molecular characterizations. All isolates were found to have remarkable nodulation status, IAA production, nitrogenase activity and increasing the root and shoot dry weight. The five selected rhizobial isolates were identified by partial sequencing of 16S rRNA genes and registered in the GenBank database. The alignment and phylogenetic analyses of 16S rRNA sequences closely related in the GenBank revealed that all isolates belonging to &lt;i&gt;Rhizobium leguminosarum&lt;/i&gt; bv. viciae. &lt;b&gt;Conclusion:&lt;/b&gt; The results confirmed that the five Rhizobial strains will be promising as a source of genes for nitrogen fixation and plant growth promotion.

Phialocephala fortinii increases aluminum tolerance in Miscanthus sinensis growing in acidic mine soil

Miscanthus sinensis growing in our study mine site contained a high concentration of Al in the adventitious roots. It has a root endophyte, Phialocephala fortinii, in its adventitious roots at a high frequency. The purpose of this study was to elucidate the effects of P. fortinii on Al tolerance mechanisms of M. sinensis and reveal potential underlying mechanisms. In the absence of P. fortinii, M. sinensis produced chlorogenic, citric, and malic acids that could act to alleviate Al toxicity in acidic mine soil. Up on fungal inoculation, the levels of these compounds were reduced, although the growth of seedlings and Mg concentration in the roots were increased. IAA production by the fungus may contribute to enhanced plant growth whereas an increase of Mg uptake could reduce toxicity of reactive oxygen species under Al stress. These actions of P. fortinii could promote growth and survival of M. sinensis in mine sites.

Antifungal activity and IAA production by endophytic fungi isolated from Elettaria sp

Medicinal plants may become a favourable habitat for associative microorganisms, especially endophytic microbes inhabiting Zingiberaceaen species. Preliminary investigation has revealed an assemblage of endophytic fungi colonizing the healthy rhizome of Elettaria sp. collected from Sibayak Forest, North Sumatra based on molecular evidences. This study investigated the IAA-producing and antifungal activity from Elletaria endophytic fungi identified as Curvularia lunata, Pholiota multicingulata, Trichoderma atroviride, T. harzianum and Schizophyllum commune. Quantification of IAA was based on colorimetry method using Salkowsky reagent which produced pinkish to reddish solution indicating the presence of IAA. Antagonistic test was based on dual culture assay measured in colony growth inhibition (%). Statistical test to signify the differences were analysed using one-way ANOVA. C. lunata produced the highest IAA concentration of 45.17 µg.mL−1 followed by S. commune, and T. atroviride with concentration of 11.7 and 5.27 µg.mL−1, respectively. The strongest antagonistic activities were displayed by T. harzianum against both G. boninense (CGI>75%) and R. lignosus (CGI>50%). In addition, the strongest endophytic fungus against F. oxysporum was P. multicingulata (CGI>70%). Further investigations are being conducted to elaborate other plant growth promotion properties and even characterization of bioactive metabolites produced by Elettaria endophytic fungi.

Influence of Plant Growth Promoting Rhizobium on Growth of Pigeon Pea [Cajanus cajan (L.) Millsp.

Background: Symbiotic nitrogen fixation plays a major role in the production of million tons of total biological nitrogen. The Rhizobium not only fixes the nitrogen but also produces plant growth promoting hormones. In this view, the present study was undertaken to characterize the native Rhizobium isolates for their functional properties and evaluate on pigeon pea for their plant growth promotional activities. Methods: The present investigation was carried out during the year 2018-19 at UAS, Dharwad. Five of the native isolates obtained from Northern district of Karnataka were subjected for functional characterization using standard methods. The isolates were also tested for their plant growth promotional activities.Result: The IAA production in the isolates was ranged from 20.50 to 22.85 mg IAA/ml of broth and GA production from 13.40 to 14.51 mg/25ml of broth. ACC deamination activity in the isolates was ranged from 57.50 to 75.5 nmoles of α-ketobutyrate/mg/h of broth. All the isolates exhibited their ability to solubilize P and Zn. Out of ten isolates, four isolates exhibited potential to inhibit mycelial growth of Fusarium oxysporum f. sp. udum and per cent inhibition was ranged from 48.75 to 73.75. All the isolates were found to be positive for siderophore and HCN production. The isolate AMVPR98 performed better with respect to all the growth parameters of pigeon pea. Molecular characterization of isolate AMVPR98 revealed 99% similarity with Rhizobium pusense strain AB3.

The Impact of Growth-Promoting Streptomycetes Isolated from Rhizosphere and Bulk Soil on Oilseed Rape (Brassica napus L.) Growth Parameters

Inoculation of Streptomyces to improve oilseed rape (Brassica napus L.) yields and minimise the use of chemical fertilisers is a promising sustainable strategy. In this study, we isolated 72 actinobacterial strains from rhizosphere of oilseed rape and maize and from bulk soil for screening and characterising their antimicrobial activity. Nine promising strains, identified as Streptomyces sp. by morphology, physiological characteristics, and 16S rRNA gene sequencing, were selected for their plant growth-promoting traits and in planta experiments. The actinobacterial strains were positive for IAA production, siderophore production, and HCN production. In planta experiments were conducted by soaking the oilseed rape seeds in the actinobacterial suspension, followed by plant growth under controlled conditions in a cultivate chamber (22–28 °C, 8 h dark/16 h light, constant humidity 80%). We recorded root and shoot length (cm) and seedling fresh weight (g). For most of the abovementioned parameters, a significant enhancement was observed with strain KmiRC20A118 treatment. The length of the root increased by 53.14%, the shoot length increased by 65.6%, and the weight of the fresh plant by 60% compared to the control. The integrated application of PGPS (Plant Growth Promoting Streptomyces) from the rhizosphere of oilseed rape is a promising strategy to improve the growth of oilseed rape.

OPTIMIZATION OF CULTURE CONDITION FOR IAA RODUCTION BY BACILLUS SP. ISOLATED FROM CASSAVA FIELD OF VIETNAM

Abstract. The bacteria capable producing IAA were isolated from roots of cassava growing in Tay Ninh region (Southern of Vietnam). The isolate producing highest amount of IAA was chosen for identification and optimization of culture conditions for IAA production. By analyzing 16S rRNA sequence, the selected isolate was identified as Bacillus sp. DTAN-M5. The influence of different parameters on IAA production of this strains was evaluated by “one factor at a time” method and the obtained results showed that the best conditions for IAA production of DTAN-M5 were medium with following components: 1% peptone; 0.5% sucrose , 0.6% yeast extract, 0.5% NaCl, pH 7.1, supplemented with 2mg/L L-tryptophan, incubation in a shaker 150 rpm at 30o C for 84 hours. The maximum amount of IAA was 84,13 µg/mL

Screening and characterization of nutrient solubilizing phytobeneficial rhizobacteria from healthy coconut palms in root (wilt) diseased tract of Kerala, India

Aim: Isolation, screening and characterization of beneficial rhizosphere bacteria associated with healthy (field-resistant) coconut palms in root (wilt) disease endemic hotspot areas of Kerala. Methodology: One hundred and ten rhizobacterial isolates associated with healthy coconut palms of root (wilt) diseased tract of Kerala were isolated and screened in-vitro for IAA production and solubilization of fixed forms of mineral nutrients. Seven isolates showing multiple phytobeneficial properties were characterized and the selected isolate was tested for its biopriming effect on maize. Results: Of the total isolates screened, 54 isolates produced IAA. Among the nutrient solubilizers, silicate solubilizers (57%) and phosphate solubilizers (48%) dominated. Of the seven isolates with multiple phytobeneficial properties, five rhizobacterial isolates belonged to Enterobacteriaceae family including three Enterobacter spp. The isolate T4HFB9 belonged to Acinetobacter sp. The green fluorescent Pseudomonas isolate K3HPSB2, showed 99% sequence similarity with Pseudomonas migulae. Seed biopriming of maize with Pseudomonas sp. strain K3HPSB2 recorded significant increase in germination percentage and seedling vigour index over untreated control. Interpretation: Disease-resistant coconut palms in RWD endemic tracts host a good proportion of phytobeneficial rhizosphere bacteria,with demonstrable multiple plant growth promoting traits. Multi-nutrient solubilizing Pseudomonas sp. with bioinoculant prospects has been selected for further studies on bio-priming for palm health management in RWD endemic tracts.

Culture medium optimization for Indole-3-Acetic Acid production by Serratia plymuthica UBCF_13

Serratia plymuthica UBCF_13 is one of the bacteria that can increase plant growth [plant growth-promoting bacteria] by producing IAA [Indole-3-Acetic Acid]. S. plymuthica UBCF_13 is a strain of Andalas University Biotechnology Laboratory Collection which can produce IAA and increase the growth of Solanaceae plants. Optimization of culture media needs to be analyzed to increase IAA production on UBCF_13. Optimization can be done by adding tryptophan as a precursor, using various types of media, adding wall affecting agents, and certain metal ions. In this study, optimization was carried out by testing the type of media [TSB, NB, YM, and King’s B], adding tryptophan [0, 100, 200, 300 μg/mL], differences in pH [5, 6, 7, 8], giving wall affecting agent [SDS 0.1 μg / mL, EDTA 0.1 μg/mL], and metal ions [Ca, Fe, K, Mg at a concentration of 0.05% and 0.1%]. The highest IAA production was obtained in the combination treatment of YM media and tryptophan 300 μg/mL. Meanwhile, the treatment of differences in pH and wall affecting agents did not have a significant effect on the increase in the production of IAA UBCF_13. Testing of metal types on IAA production showed that calcium was able to increase the production of IAA UBCF_13 by 12-14 μg/mL. Serratia plymuthica UBCF_13 produced the highest IAA on YM media combined with the addition of 300 μg/mL of tryptophan and 0.1% calcium ion.

Different pH levels medium effects in IAA production of phylloplane bacterium Serratia plymuthica strain UBCF_13

Indole-3-acetic acid [IAA] is the main source of auxin in plants that plays a major role in controlling various physiological processes. The ability of bacterium in IAA biosynthesis depends on several environmental factors, usually triggered by acidic stresses. This study was aimed to optimize the IAA production by phylloplane bacterium Serratiaplymuthica strain UBCF_13 with various pH levels. Optimization was carried out by using 0.2% L-Tryptophan in Luria Bertani[LB] media with various pH levels namely pH 4.0; 4.5; 5.0; 5.5; 6.0; 6.5; 7.0 and 9.0. UBCF_13 showed the best IAA production at pH 6.0 and 0.2% L-Tryptophan exhibited IAA concentration in the amount of 24.13 ppm. The UBCF_13 extracellular protein profile analysis showed that at pH 6.0 induced L-Tryptophan 0.2% produced protein bands of 60.8 kDa and 45 kDa in size. These protein bands are assumed to be ipdC and nitrilase proteins which are involved in the IAA biosynthesis. The application of IAA was carried out using chili peppers [Capsicum annuum L.] germination of the Lotanbar genotype. The application was using supernatant produced from media of pH 6.0 and 0.2% L-Tryptophan. The results show that root and hypocotyl lengths were 4.10 cm and 2.90 cm, respectively. Meanwhile, root and hypocotyl lengths in the control sample only 2.78 cm and 1.88 cm. The results indicated that the IAA production of UBCF_13 can promote the growth of chili seedling. A further detailed study on the visualization of protein profiles at the optimum treatment needs to be done. Two-DimensionalElectrophoresis is recommended to be applied so that protein bands can be accurately separated to identify detailed proteins involved in the IAA biosynthesis.

Preliminary analysis of Endophytic Plant Growth Promoting (PGP) Methylobacterium sp. Isolated from Palm Oil (Elaeis guineensis) Leaves

The genus Methylobacterium is known for its pink-pigmented facultative methylotrophs (PPFMs). They are able to utilize methanol emitted from plants and in return produce plant growth promoting substances. The genus Methylobacterium can be found in diverse habitats and they are known particularly for their close association with plants. The aims of this study are to isolate and characterize endophythic Methylobacterium sp. from palm oil leaves. Isolation of Methylobacterium sp was conducted using Ammonia Mineral Salts (AMS) agar supplemented with methanol. Three isolates were selected namely ENPM1, ENPM2 and ENPM3. Production of IAA by the selected isolates was evaluated under different concentration of L-tryptophan as an inducer. It was observed that the amount of(IAA) produced increased when higher concentration of tryptophan was used and ENPM1 recorded the highest amount of IAA production (1.930 μg/mL) at the 1000 μg/mL concentration of L-tryptophan. The ability to solubilized inorganic phosphate was investigated using Solubilisation Index (SI) assay on phosphate solubilisation media (PSM). The largest clear zone formation on PSM agar was shown by ENPM3 with the SI 1.5. As for nitrogen fixation, the growth of the selected isolates on two nitrogen free media namely Burk’s and Jensen media indicates potential nitrogen fixing activity.

Potential Screening of Indigenous Drought Stress Tolerant Bacteria for Plant Growth Promotion (PGP) Traits: An In-vitro Study

Aims: The study aims to formulate relevant microbial consortia against drought stress mitigation with potential drought stress tolerant bacterial isolates by polyethylene glycol 6000 (PEG 6000) different moisture stress levels to mitigate the drought stress which can finally helpful to increase plant and soil health under adverse stress conditions.&#x0D; Study Design: Source of rhizosphere soil samples from groundnut drought prone areas of Andhra Pradesh.&#x0D; Place and Duration of Study: Department of Agricultural Microbiology, Advanced Post Graduate Centre, Acharya N.G Ranga Agricultural University, Lam, Guntur, 522 034, between June 2017 and July 2020.&#x0D; Methodology: Isolated strains were also tested for further drought stress screening by polyethylene glycol 6000 In-vitro screening was done for different plant growth promotion activities i.e. phosphate solubilization, IAA production, ammonia production, ACC deaminase activity, HCN production and catalase. HCN production, catalase positive, colony morphology, Gram staining and biochemical tests.&#x0D; Results: Fifty-one efficient bacterial isolates were obtained from drought prone rhizosphere soils of groundnut. Isolated strains were also tested for further drought stress screening by polyethylene glycol 6000 at 0% (-0.05 MPa), 10% (-0.65 MPa), 20% (-1.57 MPa), 30% (-2.17 MPa) and 40% (-2.70 MPa). Thirty-seven bacterial isolates were further found to have an enzyme 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity which improved plant growth during stress conditions. The In-vitro screening was done for different plant growth promotion activities, twelve bacterial isolates were positive for phosphate solubilization. IAA production was shown by almost all the bacterial isolates. Three isolates were positive for ammonia production. Two isolates were positive for HCN production and all the isolates were found to be catalase positive. Seven isolates were showing maximum plant growth promotion activities and further identified based on colony morphology, Gram staining and biochemical tests.&#x0D; Conclusion: This study suggests that 51 bacterial isolates exhibited the highest tolerance to moisture stress under In-vitro, these are screened and considered as potential isolates against plant growth promoting characteristics. Plant growth promoting bacteria that can modulate physiological response for water shortage, enhanced water or nutrient uptake and transpiration, induction of plant growth hormone signaling and increased antioxidase activity and photosynthetic rate thereby ensuring plant survival under such stressful conditions. In regard to isolates having PGP properties from the research work presented could be studied further under In-vitro and in vivo conditions from different soils with several crops for confirming their use as bio inoculants.