IAA Production Research Articles

Plant Growth Promoting Microorganism Selection and Activity Test for Reforestation of Topsoil Restoration Site

Objectives : This study was conducted to investigate the applicability of plant growth promoting microorganisms during restoration through re-vegetation of damaged topsoil.Methods : As the vegetation to be applied to the restoration site, Weigela subsessilis, Spiraea prunifolia, Pine densiflora, Pennisetum alopecuroides were selected. An attempt was made to isolate plant growth promoting microorganisms from the root zone of plants of the same species inhabiting domestic park sites and hiking trails. Plant growth promoting activities such as phosphate solubilization ability, siderophore production ability, IAA production ability, and ACC deaminase production ability were examined, and the species to be finally applied was selected and then identified. Among the strains whose plant growth promoting activity was confirmed, Arthrobacter sp. 1B2 and Paraburkholderia terrae 1P2 were applied to the genitalia and pine, respectively, and a pot experiment was conducted to confirm the activity.Results and Discussion : Forty-five strains were isolated from Weigela subsessilis, Spiraea prunifolia, Pine densiflora, Pennisetum alopecuroides and the IAA-producing ability and ACC deaminase-producing ability were confirmed for 16 strains whose phosphate solubilizing ability and siderophore-producing ability were confirmed. After selecting and identifying strains with excellent plant growth promoting ability, strains such as Cupriavidus sp, Arthrobacter sp., Pseudomonas fluorescens, Pseudomonas sp., Paraburkholderia terrae were obtained. Among them, Arthrobacter sp. 1B2 and Paraburkholderia terrae 1P2 strains were applied to genitalia and pine, respectively, and it was confirmed that plant growth was promoted.Conclusions : Bioassay experiments and field applications using plant growth promoting microorganisms have been mainly studied for herbaceous species (Grandaceae, corn, oats, etc.). However, in this study, the applied plants are shrubs class, which do not significantly grow in length, targeting damaged areas with high subsoil content, which are poor in environment and insufficient in organic and inorganic matter. Therefore, it is meaningful in that the activity of plant growth promoting microorganisms focused on absorption of inorganic substances, such as phosphate solubilization activity and siderophore ability, was investigated and the activity was confirmed by performing a bioassay.

A potent cadmium bioaccumulating Enterobacter cloacae strain displays phytobeneficial property in Cd-exposed rice seedlings.

In agricultural soil, cadmium (Cd) pollution compromises soil health, reduces crop yield, and produces Cd-contaminated crops. Bio-based approaches are necessary as an eco-friendly and sustainable solution to mitigate Cd-polluted areas. A heavy metal-resistant rhizobacterial strain (AS10) has been isolated from a heavy metal-defiled rice field. The 16S rDNA sequence and MALDI-TOF MS analyses of ribosomal protein reveal its identity closely similar to Enterobacter cloacae. The strain was found to withstand up to 4000 μg/ml Cd2+, 3312 µg/ml Pb2+ and 1500 µg/ml As3+. The Cd2+ removal efficiency was recorded as high as 72.11% when grown in 4000 μg/ml Cd2+. The strain's Cd-accumulation efficiency was also apprehended by TEM-EDAX followed by XRD-XRF-FTIR analyses. Besides, the strain showed solubilization of inorganic phosphate, ACC deaminase activity, nitrogen fixation and IAA production ability. Added further, the strain, as an efficient bioinoculant, significantly improved rice plant growth at the seedling stage through Cd immobilization. It prevented the surge of stress ethylene and oxidative stress in rice seedlings, resulting in overall plant growth improvement. Hence, the strain AS10 as potent plant growth-promoting rhizobacteria (PGPR) may be beneficial, especially in heavy metal-contaminated crop fields.

Phytostimulation and growth promotion activities of Trichoderma spp. on groundnut (Arachis hypogaea L.) crop

Groundnut (Arachis hypogaea L.) suffers from many soil borne pathogens that deteriorate the quality of the seeds and are responsible for high yield loss. Practically Trichoderma sp. is used for seed treatment, it minimizes the seed and soil borne pathogens and supports plant growth promotion activities. In the present study, five different isolates of Trichoderma spp. were isolated from groundnut (A. hypogaea ) rhizosphere soil. All the five isolates were confirmed by morphological methods and using molecular tools through Polymerase Chain Reaction (PCR) amplification of Internal Transcribed Spacer (ITS) region of Trichoderma sp. and DNA gets amplified in 650 bp to 700 bp. Trichoderma spp. were molecularly identified as T(SP)-20 (Trichoderma longibrachiatum), T(AR)-10 (T. asperellum), T(VT)-3 (T. hamatum), T(BI)-16 (T. longibrachiatum), T(TK)-23 (T. citrinoviride). Phytostimulation activities of all the six isolates viz., phosphate solubilization, Ammonia production, IAA production, and Siderophore production, were evaluated. Among the six isolates, T(SP)-20, T(AR)-10, and TNAU-TA showed higher phytostimulation activities. The growth promotion of Trichoderma spp. on groundnut was assessed through the roll towel method. The isolate T(SP)-20 (T. longibrachiatum) produced the highest germination percentage of 93.33 and vigor index of 2246.2. This work developed a new isolate of T. longibrachiatum (T(SP)-20) which is a native isolate having significant phytostimulation and growth promotion activities and it could be exploited for other soil borne disease managing successfully.

Exploration of Klebsiella pneumoniae M6 for paclobutrazol degradation, plant growth attributes, and biocontrol action under subtropical ecosystem.

In recent times, injudicious use of paclobutrazol (PBZ) in mango orchards deteriorates the soil quality and fertility by persistence nature and causes a serious ecosystem imbalance. In this study, a new Klebsiella pneumoniae strain M6 (MW228061) was isolated from mango rhizosphere and characterized as a potent plant growth promoter, biocontrol, and PBZ degrading agent. The strain M6 efficiently utilizes PBZ as carbon, energy and nitrogen source and degrades up to 98.28% (50 mgL-1 initial conc.) of PBZ at 15th day of incubation in MS medium. In the soil system first order degradation kinetics and linear model suggested 4.5 days was the theoretical half-life (t1/2 value) of PBZ with strain M6. Box Behnken design (BBD) model of Response surface methodology (RSM) showed pH 7.0, 31°C temperature, and 2.0 ml inoculum size (8 x 109 CFU mL-1) was optimized condition for maximum PBZ degradation with strain M6. Plant growth promoting attributes such as Zn, K, PO4 solubilization IAA, HCN and NH3 production of strain M6 showed positive results and were assessed quantitatively. The relation between plant growth promotion and PBZ degradation was analyzed by heat map, principal component analysis (PCA) and, clustal correlation analysis (CCA). Strain M6 was also showing a significant biocontrol activity against pathogenic fungi such as Fusarium oxysporum (MTCC–284), Colletotrichum gloeosporioides (MTCC– 2190), Pythium aphanidermatum (MTCC– 1024), Tropical race 1 (TR -1), and Tropical race 4 (TR -4). Hence, results of the study suggested that strain M6 can be utilized as an effective bio-agent to restore degraded land affected by persistent use of paclobutrazol.

Metagenomic insights into plant growth promoting genes inherent in bacterial endophytes of Emilia sonchifolia (Linn.) DC

Studies on the genome of endophytes reveal the metabolic potential of endophytic microbiome including both culturable and unculturable fractions. The metagenome analysis through the Illumina HiSeq platform gives access to the genetic data encrypted for the molecular machinery, which takes part in plant growth promotion activity of the endophyte in various aspects including production of plant growth hormones and enhancing nutrient availability for the host plant. The present work was undertaken to identify the genes involved in plant growth promotion activities from the endophytes of Emilia sonchifolia(Linn.) DC. through metagenome analysis. Metagenomic studies include the analysis of functional annotations which aid in the detection of biocatalysts taking part in the metabolic pathway of host plants. The annotations of expressed genes in different databases like NCBI Nr, KEGG, eggnog and CAZy resulted in enlisting the vast array of information on the genetic diversity of the endophytic microbiome. The metagenome analysis of endophytic bacteria from the medicinal plant E.sonchifolia unveiled characteristic functional genes involved in plant growth promotion such as nitrogen metabolism (nif) and siderophore production (enterobactin category), ipdC and tnaA (IAA producing), ACC deaminase coding genes (regulation of elevated ethylene levels in host tissues), Mo-Nitrogenase, nitrous-oxide reductase (nosZ), nitrate reductase (narG, napA), nitrite reductase (nirD) (nutrient assimilation and absorption) enterobactin siderophore synthetase components F and D and acid phosphatase genes. This clearly explains the effective plant-microbe relationship and the role of bacterial endophytic microbes in regulating the growth of host plants.

The qualitative screening of cellulolytic, chitinolytic, IAA-producing, and phosphate solubilizing bacteria from black soldier fly larvae (Hermetia illucens L.)

Black soldier fly (Hermetia illucens L.) larvae are widely used in organic waste management. Its ability to digest organic compound was supported by the diversity of bacteria which produce various enzymes inside the larvae bodies. The exploration of potential bacteria in BSF larvae may have advantages for the agricultural field. This study aimed to screen cellulolytic, chitinolytic, phosphate solubilizing, and IAA-producing bacteria from BSF larvae. A total of 22 isolates were qualitatively screened using various media. Among the 22 isolates, five isolates showed positive results of cellulolytic activity; six isolates were able to digest chitin; nine isolates have positive result of IAA-producing test; and five isolates could solubilize phosphate in Pikovskaya’s agar. There were two isolates, B11 and B15, that gave positive result in three tests, those are on cellulolytic, phosphate solubilizing, and IAA producing test. Molecular identification of B11 showed that the isolate was similar to Bacillus altitudinis (100%) and B15 was closed to Klebsiella oxytoca (99.73%).

Evaluation of diverse range microbes for their plant growth promoting abilities and their pesticide compatibility

Plant growth-promoting rhizobacteria (PGPR) contribute to an increase in crop yield through an environmentally friendly method, therefore eight rhizospheric bacteria, two of each genera Bacillus, Pseudomonas, Azotobacter and Azospirillum were examined for their efficacy to solubilize mineral nutrients using atomic absorption spectrophotometry and a flame photometer. Their potency to produce phytohormones, synthesis biocontrol components and their compatibility with pesticides using in vitro assays was studied. All of the chosen bacterial isolates proved positive for the above-mentioned Plant Growth Promoting traits. Among the eight bacterial isolates Pseudomonas isolate P69 showed the highest phosphorous solubilization efficiency of 190.91 % and another isolate P48 produced a maximum of 27.63µg mL-1 of gibberellic acid, Bacillus isolate B120 could solubilize maximum amount of ZnO and ZnCO3 accounting for 21.3ppm and 25.9ppm, respectively, not merely in terms of solubilization when compared to the other isolates, B120 produced the highest levels of HCN (77.33 ppm TCC) and siderophores (48.87psu). On day 9 after inoculation, Azotobacter isolate AZB17 performed effectively in potassium solubilization of 6.25g mL-1 with a pH drop to 3.83. The Azospirillum isolate ASP25 outperformed all other isolates in terms of IAA production (22.64g mL-1) and Bacillus isolate B365 was found to be more compatible with eight different pesticides used in the field at varying concentrations. All of these factors point to the possibility of using these bacterial isolates B120, P48, P69, AZB17, and ASP25 as biofertilizers in sustainable agriculture.

Potentials of Lactic Acid Bacteria in Enhancing Nodulation of Bradyrhizobium daqingense and Yield in Soybean

Background: The ferments of lactic acid bacteria (LAB) are used since decades in agricultural practice to control diseases, to promote plant growth and also to improve soils. However the functional roles of LAB in phytomicrobiome need to be discovered, which would result in understanding of the symbiotic relationship between LAB and plants and that could be exploited to improve agricultural production. Methods: In this study, the scientific investigation was carried out for pot culture evaluation of six efficient LAB isolates from soybean rhizosphere, on nodulation and yield of soybean in green house condition, which were proven positive for IAA and GA production and PGPR traits. Result: Among the eight different treatment combination with Bradyrhizobium daqingense the treatment which received consortium of all six LAB isolates had significant impact on plant growth characters viz. plant height, root length, number of branches and chlorophyll content at 30 and 60 DAS. The LAB consortia also showed significantly high nodule number (47.67), nodule dry weight (117 mg plant-1) and leg haemoglobin content (6.27 mg g-1 fresh nodule) at 30 DAS. The yield and yield related traits was also highest in consortium treated plants. The property of plant to produce more nodules and healthy root growth can be attributed to IAA producing ability of inoculated LAB isolates.

Development of native Pseudomonas aeruginosa bioformulations with plant growth promoting potential for apple crop in Himachal Pradesh

This study was conducted to characterize different plant growth promoting Pseudomonas strains isolated from wet temperate zones of Himachal Pradesh and two best effective plant growth promoting P. aeruginosa strains An-14-Mg and An-15-Mg were tested under field conditions to evaluate their growth promotional effect on apple crop. Maximum production of all the plant growth promoting traits were shown by two Pseudomonas isolate An-14-Mg and An-15-Mg. Maximum phosphate solubilization was shown by An-15-Mg (46 mm) whereas highest siderophore units (SU) were recorded in An-14-Mg (71.23%SU) followed by An-15-Mg (70.12%SU) which were statistically at par with each other. Highest IAA production (95 µg/ml), HCN (++++) and ammonia (++++) production was observed again in Pseudomonas isolate An-15-Mg. Both the strains exhibited 99% level of similarity with P. aeruginosa. The presence of An-14-Mg, An-15-Mg alone and consortium were tested under field conditions to study their effect on percent survival of apple rootstocks, plant height and number of shoots up to 3 years period. Maximum increase in percent survival, plant height, number of shoots, chlorophyll content and available NPK content of soil were observed in consortial bioformulation after 3 years growth observed in apple plants. Both the P. aeruginosa strains were reported first time as plant growth promoter with apple tree, therefore can be used as biofertilizer in apple crop of Himachal Pradesh.

Endophyte bacteria growth promotion effect on Lemna gibba plants

Duckweeds a kind of aquatic plants classified as macrophytes, have been considered as nutrient pumps that can help to reduce the eutrophication effects. Studies of endophyte associates focused to their functional analysis contributing the knowledge of plant microbe interactions. This work compared the phytohormones in vitro production efficiency of endophyte bacteria isolated from Lemna gibba plants and their plant growth promoting effect in this plant species. Five endophyte bacteria belonging to Bacillus genera and named: Bacillus sp. strain Fb1, Bacillus sp. strain Fb2, Bacillus sp. strain Fb3, Bacillus sp. strain Fb4 and Bacillus sp. strain Fb5 were isolated. The IAA quantified as basal and inherent production without the addition of the amino acid tryptophan showed that Bacillus sp. strain Fb1, Bacillus sp. strain Fb3 and Bacillus sp. strain Fb5, were considered as higher producers (24.21, 25.44 and 30.8 μg/mL, respectively). Even the effect of plant growth (EPG) on Lemna gibba plants was between 40 to 70 %; a suitable promoting activity by the endophyte bacteria tested was obtained, and could be associated with their IAA production. This work contributes to the knowledge of the phytobacteria diversity in aquatic plants, particularly in Lemnaceae species; here the five endophyte bacteria could be candidates to be recommended as biostimulants.

Characterization of rhizobia isolated from leguminous plants and their impact on the growth of ICCV 2 variety of chickpea (Cicer arietinum L.)

Six rhizobia-like-bacterial strains in total, secluded from the root and stem nodules of various leguminous plants were characterized for growth promoting ability on ICCV 2 variety of chickpea. Bacterial strains showed production of IAA, NH3, siderophore, HCN, ACC deaminase, hydrolytic enzyme production such as chitinase, amylase, protease, lipase, β-1, 3-glucanase and solubilization of nutrients such as phosphate, zinc and potassium. However the performance of PGP traits characterized in-vitro varied among the six bacterial strains. The sequences of 16S rRNA gene of bacterial strains IHSR, IHRG, IHAA, IHGN-3, IHCP-1 and IHCP-2 showed maximum identity with Rhizobium sp., Rhizobium tropici, Rhizobium multihospitium, Mesorhizobium sp., Burkholderia cepacia and Rhizobium pusense. In plate culture conditions the bacterial strains changed the colour of media (NFB) from green to blue and showed amplification of nifH gene by PCR, and also enhanced nodule formation in chickpea under greenhouse conditions, which explains their nitrogen fixing ability. Scanning electron microscopy studies of chickpea roots showed colonization by all the six bacterial strains in solo and by consortium (IHRG + IHGN-3). Under greenhouse conditions, chickpea plants inoculated with different strains showed improvement in plant height, number of branches, total chlorophyll, nodule number, nodule weight, shoot weight, root weight, root volume and root surface area at 30 and 45 days after sowing (DAS) over the uninoculated control plants. It was also observed at the crop maturity stage all the bacterial strains inoculated separately enhanced pod number, seed number and total NPK compared to uninoculated control plants. This study suggests that bacteria associated with root and stem nodules can be a promising resource to enhance nodulation, PGP and crop yields in chickpea.

Detection and Identification of Plant Growth Promoting Bacteria from Sorghum (Sorghum bicolor L. Moench) Rhizosphere Soil in Northern Ethiopia

Plant growth promoting rhizobacteria are the bacteria which subsist inside and outside of the plant tissue and promote plant growth through direct or indirect mechanisms. To increase sorghum production and productivity we utilize herbicides and chemical fertilizers to overcome sorghum production constraints, but those chemicals have negative side effects. The current study was conducted with the objective of isolation of PGPR from sorghum rhizosphere and screening for primary growth related trait, evaluation of potential PGPR at greenhouse for sorghum growth performance and identify through biochemical characterization. So that, in this study a total of 117 plant growth promoting rhizobacteria were isolated from the rhizosphere of 12 sorghum (Sorghum bicolor L. Moench) genotype by cultivating using 3 collected soil samples from the northern part of Ethiopia (Amhara and Tigray regional states) in greenhouse. Isolated bacteria were screened for primary growth promoting traits such as phosphate solubilization test, IAA production test at different concentration of L-tryptophan and ammonia production test. From the isolated bacteria 28% solubilized Phosphorous, 78% produced IAA at different concentration of tryptophan. The greatest IAA production was scored at 100 mg/L of tryptophan and the lowest production of IAA was scored at 150 mg/L of tryptophan, 69% of isolated bacteria produced ammonia. Hence, 15% of isolated bacteria fulfilled the above primary screening test and used for further greenhouse evaluation. Accordingly, eighteen bacteria were tested for greenhouse experiment using completely randomized design and all 18 isolates were significantly increased all the agronomic parameter as compared to the control such as plant shoot height, plant shoot fresh and dry weight, root length, root fresh and dry weight at p < 0.01 and P ≤ 0.001. Two isolates G6E29 and G4E19 had significantly increased all the parameter but two isolates (G12E19 and G3E40) were statistically non-significant for root fresh weight compared to the control. These 18 potential isolates were characterized morphologically and biochemically. Eight isolates were grouped at Pseudomonas genera. Six isolates were grouped at Azotobacter and the rest four isolates were grouped at Bacillus genera. Thus, the use of plant growth promoting rhizosphere bacteria could be useful to improve sorghum production and productivity. However, further molecular identification and evaluation of the isolates exhibiting multiple plant growths promoting traits on plant-microbe interaction for economic crop of Ethiopia is needed to uncover their efficacy as effective plant growth promoting rhizosphere bacteria.

Streptomyces sp. S-9 promotes plant growth and confers resistance in Pigeon pea (Cajanus cajan) against Fusarium wilt.

Streptomyces sp. strain S-9 was studied for its effect in inducing systemic resistance in Pigeon pea against the plant pathogen Fusarium udum causing wilt. The 16S rRNA gene sequencing and phylogenetic analysis indicated that S-9 is closely related to genus Streptomyces for which it was referred to as Streptomyces sp. S-9. Streptomyces sp. S-9 caused 85% inhibition of the pathogen and showed various attributes of plant growth-promoting such as the production of IAA, P-solubilization, and -1, 3-Glucanase activity. Proline and malondialdehyde (MDA) content was significantly higher whereas the chlorophyll content decreased in the pathogen-infected plant when compared to S-9 treated Pigeon pea plants. The anatomical research assisted the biocontrol-mediated stress tolerance findings in the Pigeon pea plant through increased root epidermis and enhanced stress-related xylem tissues. Fungus inoculation elevated the antioxidative enzymatic activities of superoxide dismutase (SOD; 78%) and catalase (CAT; 56%). Marked reductions in antioxidant enzymes were associated with the antagonistic effects of the different treatments. Conclusions showed that S-9 bioinocula applied as a seed coating enhanced soil availability of nitrogen (N), phosphate (P), and potassium (K), indicating their suitability for direct application invigorating plant growth and persuade resistance in the plant Pigeon pea against Fusarium wilt. The online version contains supplementary material available at 10.1007/s13205-021-02989-0.

Wheat Growth Dependent Succession of Culturable Endophytic Bacteria and Their Plant Growth Promoting Traits.

Endophytic bacteria present ubiquitously in all plant parts. Their community structure may vary depending on plant tissue and growth condition. This work mainly focused on exploring the diversity of culturable nitrogen-fixing endophytic bacteria in above-ground plant parts of wheat by harvesting it during various growth points (Seed stage, 1st, 2nd, and 3rd month old plants, respectively). Distinct endophytic bacterial colonies were selected on Jensen's agar plate. Based on the 16S rRNA sequencing, 43 putative nitrogen-fixing endophytic bacteria were identified. Most of the isolates were found unique to the plant growth phase except for Pseudomonas sp., Bacillus sp., Paenibacillus sp., Microbacterium sp., Exiguobacterium sp. Further, endophytic bacteria were scrutinized for their plant growth promoting traits. They were found positive for IAA production (100%), P-solubilization (21%), Zn-solubilization (63%), ammonia production (93%), and nifH gene (33%). Extracellular enzyme production was found positive for cellulase (98%), pectinase (98%), and protease (100%). Their endophytic colonization ability was assessed using reactive oxygen species (ROS) induction assay, upon their entry inside the host plant.

Characterization and low-cost preservation of Chromobacterium violaceum strain TRFM-24 isolated from Tripura state, India

BackgroundChromobacterium species, through their bioactive molecules, help in combating biotic and abiotic stresses in plants and humans. The present study was aimed to identify, characterize and preserve in natural gums the violet-pigmented bacterial isolate TRFM-24 recovered from the rhizosphere soil of rice collected from Tripura state. ResultsBased on morphological, biochemical and 16S rRNA gene sequencing, the isolate TFRM-24 was identified as Chromobacterium violaceum (NAIMCC-B-02276; MCC 4212). The bacterium is saprophytic, free living and Gram negative. The strain was found positive for production of IAA, cellulase, xylanase and protease, and showed tolerance to salt (2.5%) and drought (-1.2 MPa). However, it showed poor biocontrol activity against soil-borne phytopathogens and nutrient-solubilizing abilitiets. C. violaceum strain TRFM-24 did not survive on tryptic soya agar (TSA) beyond 12 days between 4 and 32 °C temperature hence a method of preservation of this bacterium was attempted using different natural gums namely Acacia nilotica (babul), Anogeissus latifolia (dhavda), Boswellia serrata (salai) and Butea monosperma (palash) under different temperature regime (6–32 °C). The bacterium survived in babul gum (gum acacia), dhavda and salai solution at room temperature beyond a year. ConclusionBased on polyphasic approach, a violet-pigmented isolate TRFM-24 was identified as Chromobacterim violaceum which possessed some attributes of plant and human importance. Further, a simple and low-cost preservation method of strain TRFM-24 at room temperature was developed using natural gums such as babul, dhavda and salai gums which may be the first report to our knowledge.

Growth Promotion of Rapeseed (Brassica napus L.) and Blackleg Disease (Leptosphaeria maculans) Suppression Mediated by Endophytic Bacteria

Rapeseed is an important oil crop strongly dependent on high agrochemical inputs. Some pathogens, including Leptosphaeria maculans, cause blackleg disease and can drastically decrease yields. Microbial inoculants seem to be a promising solution to these problems. However, a selection of potent bacterial strains able to improve growth and/or suppress disease is needed. Endophytic bacteria (n = 38) isolated from rapeseed plants with exceptionally good growth were screened for plant growth promoting (PGP) traits and L. maculans antifungal activity. A majority of isolates (35) showed the ability to produce siderophores, 17 isolates solubilized phosphate, and 28 isolates inhibited the growth of L. maculans. The six most promising isolates belonging to Bacillus genera were characterized in detail and compared to two previously published PGP strains. Plant growth measured as total weight and root length of rapeseed seedlings was stimulated by all isolates in comparison to control. The best isolate, 1L6, preliminary identified as Bacillus pumilus showed the highest phosphate solubilization, IAA and HCN production, and growth promotion of plants. Isolates with high antifungal activity in screening showed good potential to suppress disease on plants, with 87% reduction of lesions caused by L. maculans. These strains are good candidates to be explored under field use either solely or in combination.

Plant growth-promoting activity of wild-type and bromate-resistant mutant of the endophytic fungus Colletotrichum karstii

Endophytes may play important roles in agriculture. Spontaneous or induced mutant strains may increase their biotechnological properties. Seventeen Colletotrichum endophytic fungi were investigated for their plant growth-promoting characteristics (in vitro phosphate solubilization, IAA, and siderophore production). The five best strains were inoculated into bean seeds, and the most prominent isolate was selected to obtain auxotrophic mutants by Potassium Bromate Resistance System (PBRS). The plant growth-promoting ability of the mutant was also investigated. Further, 41.17% of the evaluated endophytes presented promising results for in vitro assays (C. karstii SL10, C. karstii SL28, C. karstii SL57, C. karstii SL59, C. karstii SL12, C. karstii SL40, and C. karstii SL24). The endophyte C. karstii SL57 was statistically conspicuous for plant height and root length when compared to those in control plants. Bromate-resistant mutant C. karstii SL57 increased in vitro phosphate solubilization (23%) and chlorophyll levels (Chlb 0.607 mg g-1 and Chlt 0.973 mg g-1) of bean plants when compared to the wild-type strain (Chlb 0.551 mg g-1 and Chlt 0.881 mg g-1). This is the first time an auxotrophic mutant fungus has been obtained by PBRS with a biotechnological application for the agricultural field

Diversity, phosphate solubilizing, and IAA production of culturable fungi associated with healthy and wilt banana

The objective of the study was to isolate fungi from healthy and wilt banana in order to understand their diversity as well as their physiological characters to produce growth hormone and solubilize inorganic phosphate. The fungi were isolated from the leaves, roots, and rhizosphere of the banana. As many 13 fungal isolates were associated with wilt banana, consisted of Fusarium, Trichoderma, Bipolaris, Colletotrichum, Clonostachys, and Talaromyces genus. On the other hand, 12 fungal isolates that belong to 10 genera related to the healthy banana have been isolated, including Trichoderma, Pallidocercospora, Purpureocillium, Pallidocercospora, Mycosphaerella, Chaetomium, Neonectria, Pararamichloridium, Xylaria, and Neocordana. We found that the fungal isolates associated with wilt banana, particularly from the Fusarium genus, actively produced IAA in the presence of exogenous L-Tryptophan have high ability to solubilize insoluble phosphate. The ability of fungal isolates to solubilize insoluble phosphate was correlated with their ability to acidify the medium. Supplemental data for this article is available online at https://doi.org/10.1080/03235408.2021.1983362.

Bacillus siamensis CNE6- a multifaceted plant growth promoting endophyte of Cicer arietinum L. having broad spectrum antifungal activities and host colonizing potential

Exploration of endophytic bacteria with multiple plant growth promoting (PGP) attributes is considered as an eco-friendly and cost-effective alternative to agricultural chemicals for increasing crop productivity. In the present endeavor, healthy chickpea plants (Cicer arietinum L.) collected from district Birbhum, West Bengal, India were subjected for the isolation of endophytic bacteria having multifarious PGP properties. One potent endophytic Gram positive bacterial strain CNE6 was isolated from the nodule of chickpea and was identified as Bacillus siamensis based on 16S rDNA sequence homologies. The isolate showed a number of PGP properties like phosphate solubilization, IAA production, nitrogen fixation, hydroxamate type of siderophore production and ACC deaminase activities. The isolate CNE6 produced 33.27 ± 2.16 μg/mL of IAA in the presence of tryptophan. Production of IAA was also confirmed by HPLC analysis and it was found effective for inducing lateral root branching in chickpea. In addition, the isolate displayed significant antagonistic activity against a number of plant pathogenic fungi when tested by dual culture overlay and agar well diffusion assay. 50 % cell free supernatant of CNE6 was found effective for 60–80 % inhibition of radial growth of pathogenic fungi tested. Scanning electron microscopic observation revealed massive degradation of pathogenic fungal mycelia by the antifungal metabolites of CNE6. LC–MS analysis of bacterial lipopeptides suggested the production of antifungal antibiotics like surfactin, fengycin and iturin by the isolate. The presence of genes encoding antifungal lipopeptides was also confirmed by PCR amplification using specific primers. Green fluorescent protein (GFP) tagging of CNE6 using broad host range plasmid vector (pDSK-GFPuv) followed by colonization study indicated very good host colonization potential of the isolate and its probable movement through xylem vessels. Enhanced shoot and root length and chlorophyll content upon treatment with CNE6 as observed in in vivo pot experiments also supported the positive role of the endophytic isolate on overall development and growth of the chickpea plants. This is the first report of Bacillus siamensis as an endophyte of Cicer arietinum L. which can be successfully applied for improving the productivity of this crop plant.

Characterization and Plant Growth Promoting Properties of a Bacillus sp. Isolated from Maize Roots

Aim: To isolate plant growth promoting Bacillus strains from maize roots and to characterize using molecular methods, the strain with greatest potential for plant growth promotion.
 Place and Duration of Study: Department of Applied Microbiology and Brewing, Nnamdi Azikiwe University, Awka, between February 2019 and March 2020.
 Methodology: The isolation of plant growth promoting rhizobacteria (PGPR) from maize roots was made using Nitrogen Free Bromothymol Blue (NFB) broth. They were screened for Phosphate solubilizing activities on Pikovskaya (PVK) agar. Quantitative determination and solubilization of different types of Phosphates was carried out using Pikovskaya broth. Optimization of factors affecting phosphate such as NaCl concentration, initial pH of the medium, size of inoculum, was done using pvk broth. Evaluation of other plant growth promoting properties were carried out such as IAA, Ammonia, cellulase and HCN production. 
 Results: Eleven Nitrogen fixing bacteria were isolated using NFB broth based on colour change of the medium from green to blue. Test for phosphate solubilization abilities of the organisms revealed that nine of the isolates solubilized phosphate on PVK agar. Organism coded with IS52 gave the least solubilization index of 1.14 while isolate IS19 gave the highest index of 3.4. Isolate IS19 yielded the highest amount of 73.5µg/ml P, while isolate IS30 was the weakest solubilizer in PVK broth, yielding 19.4µg/ml P. The best isolate IS19, produced the plant growth hormone Indole Acetic acid at a concentration of 105.4μg/ml. The organism also gave a positive result for ammonia and cellulase production but did not produce Hydrogen cyanide. It was identified as Bacillus subtilis using the 16S rRNA gene sequencing.
 Conclusion: Bacillus subtilis fixed Nitrogen qualitatively and solubilized insoluble phosphates in addition to other plant growth promoting properties, thus Bacillus subtilis has potential for plant growth promotion, making it an efficient strain for biofertilizer production