Plant Growth Promoting Rhizobacteria Isolates Research Articles

Utilization of Stenotrophomonas koreensis and Bacillus amyloliquefaciens for Improving Growth, Reducing Nitrogen Fertilization and Controlling Bipolaris sorokiniana in Wheat

Wheat (<em>Triticum aestivum</em> L.), a vital cereal, faces significant challenges from common root rot and spot blotch diseases caused by <em>Bipolaris sorokiniana</em>. This study aimed to explore the potential of plant growth promoting rhizobacteria (PGPR) to enhance wheat growth, reduce fertilizer input, and combat <em>Bipolaris </em>diseases. Two PGPR isolates, selected for their superior antagonistic properties, were identified as <em>Stenotrophomonas koreensis</em> RB11 and <em>Bacillus amyloliquefaciens </em>RB12. These PGPR strains displayed multiple plant growth promoting and biocontrol attributes, including phosphate solubilization, indole-3-acetic acid production, nitrogen fixation and antagonism against <em>B. sorokiniana</em> and other fungi. Wheat seed priming with the PGPR significantly improved germination, plant growth, nutrient content and biomass carbon accumulation in the rhizosphere soil. Importantly, the application of RB11 and RB12 allowed for a 25% and 50% reduction in nitrogen fertilizer usage, respectively, without compromising the yield. RB11 and RB12 also demonstrated potent inhibitory effects on <em>B. sorokiniana</em> conidial germination and significantly controlled common root rot and spot blotch in wheat, similar to those observed with the fungicide Protaf 250EC. Overall, this study underscores the multifaceted roles of <em>S. koreensis</em> RB11 and <em>B. amyloliquefaciens</em> RB12 in promoting wheat growth, reducing fertilizer inputs and effectively suppressing wheat pathogens. These findings contribute to the development of PGPR-based strategies for sustainable crop production and disease control.

Isolation of plant growth-promoting rhizobacteria from the agricultural fields of Tattiannaram, Telangana

BackgroundPlant probiotics bacteria are live microbes that promote soil health and plant growth and build the stress-tolerant capacity to the plants. They benefit the plants by increasing nutrient absorption and release of stress-related phytohormones. These plant probiotic bacteria serve a better purpose to the plant when compared to chemical fertilizers. Use of chemical fertilizers such as arsenic and cadmium can lead to soil acidification and even release of harmful gases such as methane which further pollutes the environment. ResultsDifferent bacterial species were isolated from the agricultural fields of Tattiannaram, Telangana, and identified as the efficient rhizosphere bacteria with the essential qualities of plant growth promotion by evaluating the nitrogen-fixing ability on a selective media and various other methods. Upon the molecular characterization of the isolates, they were identified as Corynebacterium spp., Bacillus spp., Lactobacillus spp., and Cytobacillus spp. The results were also examined using various bioinformatics tools for accuracy in their phylogenetic pattern. ConclusionThe recognized species of plant probiotics have established roles in promoting plant growth and strengthening plant immunity. This research introduces an innovative methodology for evaluating and investigating recently identified bacterial isolates, focusing on their distinctive plant probiotic attributes. Through harnessing the potential of advantageous microorganisms and comprehending their interaction with plants and soil, our objective is to formulate inventive approaches to elevate crop productivity, enhance soil richness, and foster environmentally sustainable and robust agricultural methodologies. These characteristics exhibit promising potential for future incorporation into plant systems, fortifying growth and development, and underscoring their distinctive significance within the realm of agriculture.

Inoculation with plant growth-promoting rhizobacteria improves seagrass Thalassia hemprichii photosynthesis performance and shifts rhizosphere microbiome

Plant growth-promoting rhizobacteria (PGPR) inoculation is a crucial strategy for maintaining the sustainability of agriculture and presents a promising solution for seagrass ecological restoration in the face of disturbances. However, the possible roles and functions of PGPRs in the seagrass rhizosphere remain unclear. Here, we isolated rhizosphere bacterial strains from both reef and coastal regions and screened two PGPR isolates regarding their in vivo functional traits. Subsequently, we conducted microcosm experiments to elucidate how PGPR inoculation affected seagrass photosynthesis and shape within each rhizosphere microbiome. Both screened PGPR strains, Raoultella terrigena NXT28 and Bacillus aryabhattai XT37, excelled at expressing a specific subset of plant-beneficial functions and increased the photosynthetic rates of the seagrass host. PGPR inoculation not only decreased the abundance of sulfur-cycling bacteria, it also improved the abundance of putative iron-cycling bacteria in the seagrass rhizosphere. Strain XT37 successfully colonized the seagrass rhizosphere and displayed a leading role in microbial network structure. As a nitrogen-fixing bacteria, NXT28 showed potential to change the microbial nitrogen cycle with denitrification in the rhizosphere and alter dissimilatory and assimilatory nitrate reduction in bulk sediment. These findings have implications for the development of eco-friendly strategies aimed at exploiting microbial communities to confer sulfide tolerance in coastal seagrass ecosystem.

Plant Growth Promoting (PGP) Performances and Diversity of Bacterial Species Isolated from Olive (Olea europaea L.) Rhizosphere in Arid and Semi-arid Regions of Morocco

Plant Growth Promoting Rhizobacteria (PGPR) play an essential role in enhancing plant growth, health and yield. In this study, we describe the isolation of PGPR associated with the olive tree (Olea europaea L.) grown in three Moroccan regions of Zouala, Errachidia, and Essaouira. In these regions, we isolated 95 PGPRs from rhizosphere of Olive trees, 78% of them were characterized by their tolerance to a salinity of 4-11%. We also found that 39% of these PGPRs were phosphate solubilizing bacteria (PSB) with a solubilization ability greater than 100 µg/mL. In fact, Pantoea agglomerans (MRC_ZO_17) and Enterobacter ludwigii (MRC_ZO_97), showed the highest phosphate solubilization rates of ~450 µg/mL and ~196 µg/mL, respectively. In addition to their ability to solubilize phosphate, various isolates had the ability to produce Indole-3-acetic acid (IAA). For instance, E. ludwigii (MRC_ZO_97) had an IAA production of ~60.48 g/mL. In the region of Zouala, characterized by relatively higher salinity and lower rate of organic matter, Firmicutes isolates account for 87% of the isolated rhizobacteria. Interestingly, we found that the olive tree-associated PGPRs vary significantly between the three sampled regions. Several rhizobacteria isolated in this study are excellent candidates for formulation as bioinocula for plants in saline soils.

Enhancing Upland Rice Growth and Yield with Indigenous Plant Growth-Promoting Rhizobacteria (PGPR) Isolate at N-Fertilizers Dosage

Upland rice farming plays a crucial role in ensuring food security in Indonesia. This study aimed to evaluate the impact of plant growth-promoting rhizobacteria (PGPR) isolates on the growth of upland rice. The bioassay and pot experiments were conducted to select the capable isolates of PGPR and to investigate the effect of the PGPR inoculant on the N fertilizer efficiency and agronomic traits of upland rice. The bacterial isolates were identified through a biochemical analysis and tested under controlled greenhouse conditions. The selected PGPR inoculant was formulated as a liquid biofertilizer (LB). The three capable isolates were obtained to fix nitrogen, produce indole-3-acetic acid (IAA), organic acid, and nitrogenase activity and were identified through a biomolecular analysis as Delftia tsuruhatensis strain D9, Delftia sp. strain MS2As2, and Bacillus sp. The application of the LB into the soil at a dose of 10 L ha−1 and 50 kg ha−1 N resulted in a grain yield of 29.81 g pot−1 and a relative agronomic effectiveness (RAE) value of 235.08%, signifying a significant improvement over the conventional method. Several variables, including the number of grains, number of panicles, root length, 1000-grain weight, population of nitrogen-fixing bacteria, and nitrogen uptake exhibited a strong correlation with the grain yield, accounting for 97.80% of the observed variation. These findings show the enormous potential of PGPR isolates, specifically of Delftia tsuruhatensis strain D9, Delftia sp. strain MS2As2, and Bacillus sp., in significantly enhancing the upland rice output in Indonesia. Furthermore, the use of an LB as a biofertilizer in conjunction with nitrogen fertilization provides a viable and sustainable way to increase yields and enhance the overall sustainability of the region’s upland rice farming systems.

In-vitro Assessment of Native Plant Growth Promoting Rhizobacterial Isolates Against Diverse Fungal Phytopathogens

Although many Plant growth promoting rhizobacteria (PGPR) are used commercially, there is a need to explore more biocontrol agents to combat various pathogens and sustain the productivity of crops. PGPRs inhabit the rhizosphere region of plant and are effective in managing various pathogens. In this study, twenty-six PGPR isolates were screened in-vitro against various fungal phytopathogens in the Plant Bacteriological Laboratory, Department of Plant Pathology, Bidhan Chandra Krishi Vishwavidyalaya, Mohanpur, Nadia, West Bengal during 2021-22. All the thirteen native Bacillus isolates, showed antagonistic activity against Alternaria alternata, Colletotrichum gloeosporioides, Pestalotiopsis sp., Rhizoctonia solani and Sclerotium rolfsii. Among the thirteen fluorescent pseudomonads, all showed antagonistic activity against A. alternata, C. gloeosporioides and Pestalotiopsis sp., eight, CK2LPP, CK2LP8, CK2LP12, GP2, GP8, G11SP37, K11SP4 and S21SP14, against R. solani, two, GP2 and GP8, against S. rolfsii. BRB 42, BRB 56, PR 18, GP2 and GP8 had the highest antagonistic activity against the fungal pathogens under in-vitro condition based on average mycelium inhibition per cent. BRB 56, SM 9 and GP8, showed the maximum inhibition zone against all the phytopathogens.

Rhizobacterial Isolates from Prosopis limensis Promote the Growth of Raphanus sativus L. Under Salt Stress

Microbial biotechnology employes techniques that rely based on the natural interactions that occur in ecosystems. Bacteria, including rhizobacteria, play an important role in plant growth, providing agricultural crops with an alternative that can mitigate the negative effects of abiotic stress, such as those caused by saline environments. In this study, bacterial isolates were obtained from soil and roots of Prosopis limensis Bentham from the department of Lambayeque, Peru. This region has high salinity levels, therefore, the collected samples were used to isolate plant growth-promoting rhizobacteria (PGPR), which were identified through morphological, and physical-biochemical characteristics. These salt tolerant bacteria were screened phosphate solubilization, indole acetic acid, deaminase activity and molecular characterization by 16S rDNA sequencing. Eighteen samples from saline soils of the Prosopis limensis plants in the northern coastal desert of San Jose district, Lambayeque, Peru. The bacterial isolates were screened for salt tolerance ranging from 2 to 10%, a total of 78 isolates were found. Isolates 03, 13 and 31 showed maximum salt tolerance at 10%, in vitro ACC production, phosphate solubilization and IAA production. The three isolates were identified by sequencing the amplified 16S rRNA gene and were found to be Pseudomonas sp. 03 (MW604823), Pseudomonas sp. 13 (MW604824) and Bordetella sp. 31 (MW604826). These microorganisms promoted the germination of radish plants and increased the germination rates for treatments T2, T3 and T4 by 129, 124 and 118% respectively. The beneficial effects of salt tolerant PGPR isolates isolated from saline environments can be new species, used to overcome the detrimental effects of salt stress on plants. The biochemical response and inoculation of the three isolates prove the potential of using these strains as a source of products that can be employed for the development of new compounds proving their potential as biofertilizers for saline environments.

Investigating the effects of plant growth-promoting rhizobacteria isolates on germination and physiology status of durum wheat under salt stress

The aim of this work is to evaluate the seedling growth and physiology status of wheat seeds inoculated with a suspension of eight plant growth-promoting rhizobacteria (PGPR) isolates. For this purpose, rhizobacteria strains were isolated from the roots of native plants growing in the Algerian steppe, then evaluated for their plant growth promotion (PGP) features, and finally applied on wheat seeds. The obtained results showed that the majority of the tested strains displayed pertinent PGP features. In in vitro experiments, results showed that salinity affected negatively seed germination and impaired plant growth while the inoculation with BC3, BC6 and BC7 strains induced a good germination rate and improved significantly the root length. In greenhouse experience, data demonstrated that non-inoculated plants accumulated a significant amount of osmoregulators (proline and glycine betaine), and recorded a decrease of their chlorophyll content, compared to inoculated plants, where the salinity tolerance of this latter has been much better with a high seedling growth as well as high chlorophyll and low osmolyte contents. The results may be a useful extension of our knowledge of the interaction between plant and PGPR, in view of their possible applications as a biofertilizer to improve plant growth in salinity-impacted regions.

Role of ACC deaminase-producing rhizobacteria in alleviation of water stress in watermelon

Owing to the increased global warming, drought severity has increased in many regions, threatening food security, especially in arid and semi-arid areas. Therefore, it is imperative to mitigate the impact of drought on plants in water-stressed areas. The utilization of plant-growth-promoting rhizobacteria (PGPRs) serves as an environmentally friendly approach to enhance the resilience of plants exposed to abiotic stress, specifically drought. This research focuses on examining the effects of 35 PGPR isolates, possessing significant ACC (1-aminocyclopropane-1-carboxylic acid) deaminase activity, which were obtained from diverse plant-rhizosphere soil samples encompassing approximately 17,000 km2 of semi-arid regions. The investigation was conducted on watermelon plants experiencing varying degrees of water stress (30% and 60% water stress). An increase in water stress exerted a detrimental effect on agro-morphological parameters, such as biomass (root + shoot), leaf number, and leaf area of non-inoculated plants. PGPRs stimulated plant growth and increased water use efficiency, especially under severe water-stress (60% water stress) conditions compared to non inoculated plants (control). Furthermore, some PGPRs such as B7, B22, B26 and B28 supported carotenoid synthesis, which plays an important role in photosynthesis, whereas some alleviated the effect of water stress in watermelon plants by stimulating the antioxidant defense system. The outcomes of principal component, where the data were collectively assessed, demonstrated the superior efficacy of certain PGPRs. Specifically, under water-stress conditions, PGPR isolates B31, B32, and B35 exhibited significant growth-promoting effects on watermelon. Additionally, isolates B13 and B15 demonstrated the activation of antioxidant defense mechanisms, including proline, catalase, and peroxidase. PGPRs showed considerable results on the agro-morphological, physiological, and biochemical properties of watermelon under 60% water-stress conditions compared with those under 30% water stress. In conclusion, PGPRs promoted growth and alleviated severe water stress in watermelon plants compared to their control. The results of this study elucidate PGPR-triggered response mechanisms in water-stressed watermelon plants.

Rhizobacterial Colonization and Management of Bacterial Speck Pathogen in Tomato by Pseudomonas spp.

Plants and soil microorganisms interact at every stage of growth. Pseudomonas spp. are highly regarded for their ability to increase crop production and protection from diseases. The aim of this study is to understand the mechanisms of the rhizobacterial colonization of tomato roots via chemotaxis assay and the activation of tomato resistance against the pathogenic bacterium, Pseudomonas syringae pv. tomato DC3000 (Pst). The capillary assay was used to evaluate the chemotaxis response of PGPRs (plant growth-promoting rhizobacteria). The activities of defense enzymes and the expressions of PR (pathogenesis-related) genes were measured using real-time qPCR. Chemotactic responses to malic and citric acids (the most important root exudates found in different plant species) at low concentrations varied substantially among the rhizobacterial isolates (63 species). Beneficial isolates including Pseudomonas resinovorans A5, P. vranovensis A30, P. resinovorans A28, P. umsongensis O26, P. stutzeri N42, and P. putida T15 reacted well to different concentrations of root exudates. P. putida T15 demonstrated the most potent anti-Pst activity. At three and six days after inoculation, the greatest levels of polyphenol oxidase and peroxidase activity were reported in the A5 and T15 groups. In tomato, transcript levels of four PR (pathogenesis-related) genes were elevated by rhizobacterial treatments. PGPR isolates alone or in combination with BABA (β-amino butyric acid) up-regulated the transcriptions of PR1, PR2, LOX, and PAL genes. Treatments with N42 and T15 resulted in the greatest improvements in tomato growth and yield traits. In conclusion, the results explain the mechanisms of rhizobacterial colonization for the improved management of Pst. Rhizobacterial isolates play a role in tomato’s resistance to Pst via salicylic acid and jasmonic acid pathways.

Improved growth and quality of saffron (Crocus sativus L.) in the field conditions through inoculation with selected native plant growth-promoting rhizobacteria (PGPR)

The use of bioresources such as bio-fertilizers especially those containing plant growth promoting rhizobacteria (PGPR), may be a strategy for sustainable agriculture that respects the environment while ensuring optimal plant growth. The objective of this study was to investigate the effects of selected PGPR strains on the growth, yield and quality of saffron. The bacteria tested were isolated from the saffron rhizosphere and selected for important plant beneficial activities (phosphate solubilization, siderophore, and auxin production). The best strains were identified by 16S rRNA gene sequence analysis. Strains S11P1 and S11A1a were identified as Rahnella aquatilis, while strain S12S4 belonged to the species Variovorax paradoxus. An inoculation field experiment was conducted in a 1575 m2 field area in Taliouine (Morocco). Four different inoculants were set-up: the three single selected strains and their mixture. Using the PGPR isolates as inoculum affects positively different saffron plant parameters, such as the number of leaves (28.87 ± 6.1 vs. 22.47 ± 8.19 for control treatment) and chlorophyll content. Underground parts, in particular, daughter corms production was significantly increased about 1.91 times more than the control. In addition, the quality of inoculated saffron was in accordance with the category I specifications (Crocin > 200, Picrocrocin > 70 and Safaranal >20). Overall these results bode well the possibility of using these rhizobacteria, and specially the treatment T2 (Rahnella aquatilis S11P1), as effective biofertilizers for saffron organic cultivation.

Performance evaluation of native plant growth-promoting rhizobacteria for paddy yield enhancement in the jhum fields of Mokokchung, Nagaland, North East India

The present study was carried out to evaluate the performance of native plant growth-promoting rhizobacteria (PGPR) on jhum paddy yield enhancement in Nagaland, Northeast India. Three indigenous PGPR isolates (Bacillus cereus MKGB, Pseudomonas fluorescens MKGPf, and Azospirillum oryzae MKGAz) were tested in the soil microcosm and jhum fields of Longkhum and Ungma villages in Mokokchung, Nagaland. The maximum 78.44% seed germination, 165 cm plant height, 30 leaves, 5 tillers, and 5 panicles per plant were recorded in the PGPR consortium inoculated pot soil. Similarly, maximum 151 grains per panicle, 21.66 g grain yield per plant, and 33.50 g of straw biomass were recorded in the same treatment. The observations from the field trials revealed a maximum of 4.67 t ha−1 paddy yield in the Longkhum village jhum field inoculated with the PGPR consortium which was significantly different from the control (T1) at a p value of ≤0.05%. Similarly 4.74 t ha−1 paddy yield was obtained from the PGPR consortium applied jhum plots in Ungma village. The PGPR consortium was found more effective and promising than the single culture inoculation in paddy yield enhancement. The study suggests the application of tested PGPR consortium in jhum fields for soil health and crop productivity improvement and achieving agricultural sustainability as well as social prosperity in the rural areas of North East India.

Plant-beneficial Bacillus, Pseudomonas, and Staphylococcus spp. from Kumaon Himalayas and their drought tolerance response

Plant growth-promoting rhizobacteria (PGPR) have been shown to augment plant responses against drought and other abiotic stresses. In the present study, we isolated 27 bacteria from the rhizosphere of various plants cultivated in the Kumaon Himalayas., and to measure their abiotic stress tolerance, these 27 isolates were subjected to variations in pH, temperature, and drought. All 27 isolates were also screened for various plant growth-promoting traits. Among these, the four isolates RR1, ASC1, AFS3, and NG4 demonstrated various plant growth promotion activities including the synthesis of indole-3-acetic acid (IAA), siderophores, ammonia, and 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase production, and concomitantly high tolerance to abiotic stresses. Moreover, 16S rRNA sequencing of these four isolates validated their identities as Bacillus, Pseudomonas, and Staphylococcus sp. Finally, to assess the in-vivo drought tolerance potential of these four isolates, a pot-trial experiment was undertaken in wheat cultivar VL-892. The results demonstrated that inoculating wheat plants with these four PGPR isolates greatly improved plant growth under drought circumstances by increasing root and shoot length and both fresh and dry weight of root and shoot. This study endeavors to discover the biochemical and molecular diversity of cultivable PGPR in six remotely located districts of Uttarakhand. In conclusion, the drought-tolerant PGPR strains described in this study are plant-beneficial and can effectively mobilize nutrients under drought conditions. Consequently, they could be used as bioinoculants to alleviate drought stress in wheat plants, in a sustainable manner. To the best of our knowledge, this is the first report of exploring the diversity and characterization of PGPR from the Kumaon Himalayas and their drought evaluation.

The Screening of Plant Growth-promoting Rhizobacteria based on the Ability to Promote the Growth and Nodulation of Soybean (Glycine max L.) Seedlings

Plant growth-promoting rhizobacteria (PGPR), which were isolated from the plant rhizosphere, decrease the addition of chemical fertilizer (N) and promote plant growth. Some PGPR isolates can fixate nitrogen, solubilize phosphate, produce phytohormones, and control soil pathogens. This study has focused on isolating rhizobacteria from root nodules of Edamame, Glycine max L, Dieng Peanut, Solanum sp. and Peanut root. Eleven isolates were assayed to examine their activities, including the ability of nitrogen fixation, produce Indol Acetic Acid hormone, siderophore, ammonia, and catalase activity. Furthermore, 11 isolates were tested to promote soybean growth in pot experiments using sterile sand media and the test of symbiotic capacity. The results showed that six isolates (RhizE2, RhizE3, RhizE4, RhizKdKbm1, Bio2DW, and Bio3DW) could form root nodules, and four isolates (RhizE2, RhizE3, RhizKdKbm1, and Bio2DW) showed a symbiotic capacity of more than 90%. RhizE2 significantly increased the number of nodules and dry weight of the entire plant (24.08 g) in comparison with plants without inoculation and added N fertilizer (11.59 g) and added N fertilizer (19.60 g). RhizE2 can be further developed as a biological fertilizer agent, especially for soybean plants. From all parameters observed, the plants inoculated with RhizE2 showed the best growth result.

Co-inoculation of multi-trait plant growth promoting rhizobacteria promotes growth and nutrient assimilation of transplant Aman rice (cv. BRRI dhan49)

BACKGROUND: Plant growth-promoting rhizobacteria (PGPR) are the rhizosphere bacteria that can enhance plant growth by a wide variety of mechanisms. This study was conducted to assess the effects of plant growth-promoting rhizobacteria on growth and nutrient assimilation of rice. METHODOLOGY: Seeds of transplant Aman rice (cv. BRRI dhan49) were collected from Bangladesh Rice Research Institute (BRRI). Pot experiment was conducted with rice plant inoculated with two PGPR isolates MQ1 (Zinc solubilizing, IAA producing, phosphate solubilizing and N2-fixing) and MQ2 (Zinc solubilizing, phosphate solubilizing and N2-fixing) with addition of three different levels of chemical fertilizers (FR0.0 no fertilizer, FR0.5 half of the recommended dose, FR1.0 full of the recommended dose of fertilizers) following Completely Randomized Design with three replications. Plant height at different days after transplanting, number of tillers hill-1 and biomass yield were recorded. Plant samples were analyzed for N, P, Ca, Mg, S, Fe, Zn, Mn, Cu and Cd contents. KEY FINDINGS: Rice plants inoculated with the PGPR both individually or in consortium along with different doses of fertilizers showed an improved plant growth and increased biomass production. Highest plant height (74.057±3.164 cm) and maximum number of tillers hill-1 (13.000±2.082) were recorded in PGPRMQ1RF1.0 treatment and the highest biomass production (10.275±0.541 t ha-1) was recorded in PGPRCONS.RF1.0. Nitrogen content and uptake of the individual PGPR treated rice plants was also found to be higher in comparison with the uninoculated control plants. Besides these iron and zinc content of the treated rice plants was also found to be higher in comparison with the uninoculated control plants. N (0.268±0.046), P (0.626±0.095), Fe (6.062094±A), Zn (1.237±0.197) and Mn (11.908±1.879) uptake were observed higher in PGPRMQ1RF1.0 treatment. CONCLUSION: PGPR inoculation has immense potential to be used as agricultural crop inoculants as they promote plant growth as well as nutrient assimilation of rice.

Isolation and Characterization of Plant Growth promoting Rhizobacteria from Bamboo Rhizosphere and Their Role in Plant Growth Promotion

Plant growth-promoting rhizobacteria (PGPR) are a group of root-associated bacteria that intimately interact with the plant roots and consequently enhance growth by extemporising nutrient retrieval or phytohormone production. We isolated and screened indigenous phosphate solubilising and auxinproducing PGPR from bamboo rhizosphere. 66 soil samples from bamboo (Bambusa nutans subsp. cupulata, B. balcooa and B. tulda) rhizospheres were collected from Dhanusha, Mahottari and Sarlahi districts, Nepal. 120 isolates of PGPR were obtained by serial dilution method in (PVK) agar and Luria Bertani agar. 92 out of 120 isolates of PGPR with the ability to solubilise phosphate were selected based on the halo colony ratio in PVK agar medium and auxin production in Luria Bertani agar. Among them, six isolates having high phosphate solubilising index and high production capacity of indole-3-acetic acid were further screened. Biochemical analysis revealed that these isolates belonged to the genus Pseudomonas. Phosphate solubilising index and indole-3- acetic acid production by six isolates ranged from 4.19±0.8 to 7.65±1.3, and IAA production ranged from 72.93±0.2 to 82.48±0.9µg/ml respectively. These isolates significantly increased shoot length (13.26±0.56cm), shoot fresh weight (16.26±1.02mg), shoot dry weight (10.56±0.09mg), root length (4.9±0.5cm), root fresh weight (7.56±1.05mg), root dry weight (3.21±0.01mg), and chlorophyll ‘a’ and chlrophyll‘b’ and carotenoid (2.16±0.01mg/g, 1.19±0.06mg/g and 0.92±0.01mg/g respectively) of B. nutans subsp. cupulata seedlings. This study suggests that PGPR isolated from bamboo rhizosphere demonstrated outstanding contribution to the growth promotion of seedlings of B. nutans subsp. cupulata as compared to negative control.

Brassicaceae, Chenopodiaceae ve Urticaceae Familyalarına Ait Bazı Bitki Türlerinin Arbusküler Mikorhizal Fungus (AMF) ve Rhizobacteria Arasındaki İlişki

This study was conducted to investigate the effects of some plant growth-promoting rhizobacteria (PGPR) on the arbuscular mycorrhizal fungi (AMF) formation on [Brassica oleracea (cauliflower), Spinacia oleracea (spinach) ,and Urtica urens (stinging nettle)] belonging to Brassicaceae, Chenopodiaceae and Urticaceae families, which are known to have a negative influence on the symbiotic life formation with AMF. Two PGPR isolates that contributed to the plant's growth and served as a “mycorrhizal helper” in various hosts were predetermined at the initial stage; then they were applied to three plant species with AMF species [Gigaspora margarita and commercial AMF (ERS)]. The obtained results revealed that combined AMF x PGPR treatments improved the growth and morphological development parameters of cauliflower, spinach, and nettle plants. PGPR bacteria had different effects on AMF root colonization depending on the plant species. The highest root colonization rate was achieved in spinach plants with the commercial AMF treatments. Commercial AMF isolate, alone or in combination with PGPR strains, was also found to increase AMF spore density and mycorrhizal dependency in cauliflower and spinach plants. There was no significant difference in total phosphorus content in cauliflower and nettle compared to the control group, and only one application group (G. margarita x PGPR) in spinach plants had an increase in phosphorus content.

Nematicidal potential of plant growth-promoting rhizobacteria against Meloidogyne incognita infesting tomato under protected cultivation

BackgroundIn the protected cultivation of tomato (Solanum lycopersicum L.) crop, the severity of root-knot nematode, Meloidogyne incognita, incidence is alarming nowadays. To combat this, growers usually prefer using synthetic chemical pesticides, which in turn results in harming non-target beneficial microbes present in the soil micro-flora and indirectly toxic to human health. Therefore, attempts were made to find out the nematicidal potential of plant growth-promoting rhizobacteria (PGPR) against M. incognita, which could be used as an alternative solution to manage M. incognita incidence under protected cultivation.ResultsNematicidal potential of three PGPR isolates and their consortium against M. incognita under laboratory, pots, and field experiments was studied. Juvenile mortality of 91.67% was recorded at 100% consortium, followed by 73.33–81.33% by individual isolates. Similarly, hatching inhibition of 84.26% was recorded at 100% PGPR consortium followed by 78.48–83.21% in individual isolates after 96 h. of incubation. In the pots’ study, soil drenched with PGPR isolates consortium, followed by Bacillus subtilis DTBS 5, Pantoea agglomerans, and Bacillus amyloliquefaciens DSBA 11 recorded significant reductions in the nematode incidence. Whereas in the field study, PGPR isolates applied as soil drenching also significantly reduced nematode’s incidence in consortium, followed by B. subtilis DTBS 5 and B. amyloliquefaciens DSBA 11-treated soil in both field experiments. On an average, the plant growth promotion and fruit yield were enhanced than untreated control and PGPR isolates applied as soil drenching gave a significant result than bare root dip treatment.ConclusionsPGPR isolates, B. amyloliquefaciens DSBA 11, B. subtilis DTBS 5, and P. agglomerans, were found to be effective against M. incognita. This finding can be incorporated into the nematode management strategy in tomato crop grown under protected cultivation. Further to enhance the biocontrol efficacy of these PGPR isolates, suitable formulations of either individual or consortium need to be done.

Use of plant growth-promoting rhizobacteria isolates as a potential biofertiliser for wheat

Use of plant growth-promoting rhizobacteria isolates as a potential biofertiliser for wheat

Growth Promotion of Rice (Oryza sativa L.) Seedlings Using Plant Growth-Promoting Rhizobacteria (PGPR) Isolated from Northwest Ethiopia

Plant growth-promoting rhizobacteria (PGPR) are beneficial soil microorganisms that colonize plant roots and enhance plant growth by a wide variety of mechanisms. In this work, five Bacillus and two Cyanobacteria isolates were successfully isolated and characterized. A pot experiment was conducted to evaluate the effect of PGPR on the growth of three cultivars of rice seedlings. Pots were laid down in a complete random design and 100 ml of spore and Cyanobacteria suspension were poured on the soil surface surrounding each seedling. After 45 days, the seedlings were uprooted and shoot and root parameters were recorded. All the Bacillus and Cyanobacteria isolates showed positive effects on the growth of rice seedlings as compared to control; however, their effectiveness varies from isolate to isolate and also from cultivar to cultivar. Bacterial isolates B3 and B5 showed the highest mean value and statistically significant difference ( P < 0.05 ) in most of the root and shoot parameters of cultivars Jegna and Getachew, respectively, as compared to other bacterial isolates. Both cyanobacterial isolates showed the highest and statistically significant difference ( P < 0.01 ) in almost all the above ground and underground growth parameters compared to other bacterial isolates in all the three cultivars of rice. Similarly, C2 and C1 recorded the highest growth promotion efficacy of shoot and root length (50.07% and 78.27%) on Edget and Getachew cultivars, respectively. Hence, the present study suggests that the use of PGPR isolates such as B3, B5, C1, and C2 as inoculant biofertilizers might be beneficial for rice cultivation as they enhanced the growth of rice seedlings.