Genus Acinetobacter can be exploiting as an ecofriendly plant-growth promoting rhizobacteria and as an alternative to chemical fertilizers. In present study, Acinetobacter strain RSC7 isolated from the rhizosphere of sugarcane cultivar Co671 has been used for the characterization of plant growth potential and molecular identification through 16S rRNA gene sequence. The phosphate solubilisation Index (SI) of the isolate strain was tested on the Pikovskaya agar and recorded 3.5 and quantitative estimation of isolated strain revealed that maximum 27.10μg/ml phosphate was releases in NBRIP broth with 1.5% tricalcium phosphate after 120 hr incubation at 37°C. Further, IAA production was also estimated and it was reported 20.89μg/ml after 24 hr and within 48 hr production significantly increase to 43.85μg/ml. Acinetobacter strain has potential to act as plant-growth promoting rhizobacteria and can enhance the growth of Vigna radiate, Vigna unguiculata, Abelmoschus esculentus, Dolichos lablab. The improved seedling growth parameters of the treated crop seeds indicated the potential of Acinetobacter sp. RSC7 to be used in a bio-fertilizer formulation for sustainable production.
Plant growth promoting rhizobacteria is free living soil microorganisms that directly or indirectly exert beneficial effects on plants. Hundred strains were characterized morphologically and biochemically. Primary screening was carried out for all hundred isolates for IAA, phosphate solubilization, siderophore and nitrogen fixation. Eight isolates F181, F271, F323, F372, F373, F531, ELB1 and ESB4 from different sites and sugarcane cultivars have showed potential for all PGPR activities and were further investigated quantitatively. The isolates could exhibit more than two or three PGP traits, which may promote plant growth directly or indirectly or synergistically. The results shown, F372 achieved the highest phosphate solubilization of 15 mg L -1, and F271 was the most promising IAA producer with 63 mg L -1. Furthermore, most of the PGPR isolates shown antifungal properties like HCN chitinase and protease production. The present study, therefore, suggests that the use of selected PGPR isolates as inoculants might be beneficial for sugarcane cultivation.
In our study, soil samples from the rhizosphere of various uncultivated weeds were collected from fifteen different locations of Gujarat. Heat treatment was given at 65°C for 20 minutes prior to initial screening for spore-forming Bacilli spp. Among them, 20 nitrogen-fixing (NFB), 27 phosphate solubilizing (PSB) and 15 potassium mobilizing (KMB) isolates were screened primarily. After molecular identification only Bacilli isolates were further selected and characterized. Three superior Bacillus isolates were selected from each category by secondary screening. All three isolates for nitrogen fixation were found nif positive, while Bacillus megaterium (NAUN2) showed maximum 2.04 µmol/ml ammonia production followed by Bacillus sp. (NAUN1) and Lysinibacillus macroides (NAUN3) with 0.64 and 0.99 µmol/ml, respectively. Bacillus sp. (NAUP1) gave maximum 401.94 µg/ml phosphate solubilization on Pikovaskya broth media after third day while Bacillus sp. (NAUP2) and Brevibacillus sp. (NAUP3) showed 376.74 and 308.16 µg/ml phosphate solubilization, correspondingly. Lysinibacillus macroides (NAUK2) showed maximum 228.14 µg/ml potassium mobilization on Aleksandrov after the twentieth day while Lysinibacillus macroides (NAUK1), Bacillus megaterium (NAUK3) and Bacillus sp. (NAUP1) had effective 196.91, 158.18, 59.33 µg/ml potassium mobilization, respectively. Interestingly, no selected Bacilli isolates from the consortia were found to have inhibitory effect on other isolates in compatibility test. Out of the nine Bacillus isolates NAUK1, NAUK2, NAUK3 were found to be effective against rice pathogen Magnaportha oryzae on PDA plates. All the nine isolates were checked for IAA and siderophore production. Isolate NAUN1, NAUP3, NAUK1, NAUK2 and NAUK3 showed 37.2%, 17.9%, 33.6%, 38.9%, 48.2% siderophore production on CAS medium after 72 hrs, respectively. Isolate NAUP3 showed maximum 146.68 µg/ml IAA production while NAUN1, NAUN3, NAUP1, NAUK2 and NAUP2 showed 99.37, 99.37, 114.57, 101.46, 93.48 µg/ml IAA production, respectively after the seventh day. Rice seeds were inoculated with individual isolate and different Bacilli consortia, which significantly improved growth parameters as compared to control in pot study after 60 days of sowing. 100% RDF + NPK consortia gave significantly increased root length (11.65%), shoot length (10.28%), no. of leaves (17.39%), leaf area (11.68%) and chlorophyll content in leaf (4.76%). Similar trends were observed when the data was compared with absolute control. The spore forming Bacilli consortia was able to survive a wide range of temperature and pH fluctuations and found effective Nfixers, P-solubilizers, K-mobilizers, siderophore producers, IAA producers with antagonistic activity against rice pathogen Magnaportha oryzae.
In this study, soil samples from the rhizosphere of various uncultivated weeds were collected from fifteen different locations of Gujarat. Heat treatment was given at 65°C for 20 minutes prior to initial screening for spore-forming Bacillus spp. Among them, 20 nitrogen-fixing (NFB), 27 phosphate solubilising (PSB) and 15 potassium mobilizing (KMB) isolates were screened primarily. After molecular identification only Bacillus isolates were further selected and characterized. Three superior Bacillus isolates were selected from each category by secondary screening. All isolates belonging to different category were compatible in nature and showed significant ammonia production, ARA, phosphate solubilisation, potassium mobilization, siderophore production, IAA production and organic acid producers. The relative expression analysis of three genes NRT2.1 (Nitrate transporter), PT6 (Phosphorus transporter), and AKT1 (Potassium transporter) at transcriptional level were performed in the juvenile root tissues of Rice using qRT-PCR technique at 15th, 30th and 45th days after transplanting with Actin as a internal control. Rice transplants were inoculated with different NPK fixing Bacillus consortia, which significantly improved growth parameters as compared to control in field study. Various growth and yield attributing characters of rice viz., plant height (at 60 DAT, 90 DAT, and at harvesting), number of productive tillers, days to 50 % flowering, 100 seed weight, grain yield, straw yield, as well as dry biomass per hectare were significantly influenced by different treatments. An application of 100 % RDF with NPK consortia (T7) treatment of rice crop resulted in significantly higher plant height (49.25 cm at 60 DAT, 107.00 cm at 90 DAT, 129.50 cm at harvesting), days to 50% flowering (75.63), 100 seed weight (3.53 g), number of productive tillers per plant (12.13), grain yield (6889.00 kg ha-1), straw yield (8754.25 kg ha-1) and dry biomass (7889.25 kg ha-1) followed by the treatments T4 (T2 + N consortia), T5 (T2 + P consortia), T6 (T2 + K consortia), and T2 (RDF (NP) 100%). Nutrient content in grain and straw was differing significantly due to different treatments. However, significantly higher N, P, K, content in straw (1.28 %, 0.15 %, and 1.52 %) and grain (2.06 %, 0.23 %, and 0.25 %) respectively, were recorded under the treatment T7. The spore forming Bacillus consortia was able to survive at a wide range of temperature and pH fluctuations and found to be effective as N-fixers, P-solubilizers, K-mobilizers, siderophore producers, IAA producers with having antagonistic activity against rice pathogen Magnaportha oryzae.
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