1. KAUTIR (Kerala Agricultural University Theses Information and Retrieval)
Permanent URI for this communityhttp://localhost:4000/handle/123456789/1
Browse
3 results
Search Results
Item Isolation and characterization of beneficial rhizosphere microorganisms from ragi grown in Attappady hill tract of Kerala(Department of Agricultural Microbiology, College of Agriculture, Vellayani, 2021) Gayathri, M; Chitra, NThe study entitled “Isolation and characterization of beneficial rhizosphere microorganisms from ragi grown in Attappady hill tract of Kerala” was conducted during the year 2019-2021 in the Department of Agricultural Microbiology, College of Agriculture, Vellayani, Thiruvananthapuram with the objective to isolate nitrogen fixing and phosphate solubilizing bacteria from soil and root samples collected from Attapady and select efficient isolates through in vitro screening process and assess the plant growth promotion activity by roll towel assay. Thirty six nitrogen fixing bacteria and eight phosphate solubilizing bacteria were isolated from root and soil samples from ragi grown in Attappady region. The isolates were designated as ATY1-ATY36 for NFB isolates and PSB1-PSB8 for PSB isolates. Twenty isolates were selected after eliminating isolates with similarities in colony morphological characters, in order to avoid repetition among the isolates obtained from the same sample. Both NFB and PSB isolates were characterized by morphology and biochemical tests. All selected isolates were subjected to plant growth promotion activity studies. The Indole Acetic Acid (IAA) production showed a wide range of variation from 101.22 µg mL-1 to 3.26 µg mL-1 . Gibberellic Acid (GA) production of all the twenty isolates were done and the results ranged between 10.07 µg mL-1 and 2.18 µg mL-1 . Maximum IAA and GA production was recorded in isolate ATY10. Extracellular ammonia production of the bacterial isolates ranged between 176.53±5.07 μmol mL−1 and 75.59 μmol mL−1. The nitrogen content of NFB isolates ranged between 30.75 µg mL-1 and 9 µg mL-1 . The isolate ATY33 had maximum nitrogen content. The selected PSB isolates were subjected to plate assay and broth assay using Pikovskaya’s medium. The isolate PSB1 recorded maximum zone of solubilization (18.23 mm), phosphate solubilizing index (2.82) and quantification of phosphate solubilization (53.41 mg L-1 ). The bacterial isolates were screened based on weighted average ranking. In NFB, ATY10, ATY34 and ATY35 were selected for further studies and in PSB, the isolates PSB1, PSB3 and PSB4 were selected. The selected isolates were 164 identified as Pantoea agglomerans ATY10, Rhizobium sp. ATY34, Ensifer adhaerens ATY35, Burkholderia territorii PSB1, Burkholderia cepacia PSB3 and Aeromonas hydrophila PSB4 by 16s rRNA sequencing. Effect of these isolates were assessed for plant growth promotion in vitro in ragi seeds using roll towel assay. Maximum germination percentage was recorded by Aeromonas hydrophila PSB4 (81.24 per cent) and the minimum number of days taken for germinationwas recorded by Pantoea agglomerans ATY10 treated seeds. Also, the treatment Pantoea agglomerans ATY10 recorded maximum shoot length (3.31 cm), root length (7.76 cm), seedling length (11.08 cm), seedling vigour index (876.62), root dry weight (0.443 mg) and root shoot ratio (0.50). The treatment Burkholderia territorii PSB1 recorded maximum root fresh weight (3.762 mg) and shoot dry weight (0.877 mg). The six isolates were subjected to assess the multiple traits such as phosphorus, potassium and silicate solubilizing capacity, siderophore production and antifungal activity. Burkholderia territorii PSB1 showed maximum zone of inhibition against Rhizoctonia solani (3.16 mm) and Sclerotium rolfsii (0.58 mm). The maximum antagonistic activity against Fusarium sp. and Helminthosporium sp. was recorded by Burkholderia cepacia PSB3 with 4.13 mm and 5.66 mm of zone of inhibition respectively. Burkholderia territorii PSB1 and Burkholderia cepacia PSB3 solubilized potassium alumino silicate in agar also, with clearance zone of 11.00 mm and 12.66 mm (in diameter), respectively. None of the isolates solubilized magnesium trisilicate in Bunt and Rovira medium. The siderophore production was observed in Aeromonas hydrophila PSB4 isolate in Chrome Azurol S (CAS) agar medium plates. Based on the results of the present study, it can be concluded that Pantoea agglomerans ATY10 is the superior isolate among NFB isolates for plant growth promotion. Also, the isolate Burkholderia territorii PSB1 is best among PSB isolates for plant growth promotion and biocontrol activity.Item Assessment of soil temperature and soil parameters on the population and functional efficiency of pseudomonas fluorescens in the rhizosphere of pokkali rice (Oryza sative L.)(Department of Agricultural Microbiology, College of Agriculture, Vellayani, 2018) Reshma Francis; Surendra Gopal, KPokkali is a umque variety of rice that is cultivated organically in coastal wetlands of Kerala. Pokkali fields are situated close to the sea and therefore prone to flooding and salinity. Pokkali rice has enormous potential for tolerating most of the abiotic stresses. It is the only economic crop which can be grown in waterlogged environment while tolerating salinity. The present study on “Assessment of soil temperature and soil parameters on the population and functional efficiency of Pseudomonas fluorescens in the rhizosphere of Pokkali rice (Oryza sativa L.)”, was conducted in Rice Research Station, Vyttila, under Kerala Agricultural University during 2016 to 2018. Two plots (40 m2) were used for the study. One of the plots was maintained as control (without application of Pseudomonas fluorescens) and another plot with rice was treated with P. fluorescens. P. fluorescens (KAU) was applied as seed treatment (10g kg-1) just before sowing and soil application (2.5 kg ha-1) at 1 week after dismantling. The main objectives were to study the effect of soil temperature and soil parameters on the population and functional efficiency of P. fluorescens / fluorescent Pseudomonas in Pokkali rice. The rhizosphere soils of Pokkali rice were collected at monthly interval from June, 2017 to October, 2017. The population of fluorescent Pseudomonas sp. in the rhizosphere soils of Pokkali rice were recorded at monthly interval. The population was absent before the start of the experiment in treated plot. However, the highest population 3.3x102 cfu g-l) was recorded at 90 DAS (August, 2017). However, the lowest population was recorded at 60 DAS (July, 2017). The population was not found at 30 DAS (June, 2017), 120 DAS (September, 2017) and 150 DAS (October, 2017). In the case of control plot, population of fluorescent Pseudomonas was absent before the start of experiment. At 30 DAS (June, 2017) population of fluorescent Pseudomonas was 3.3 x 102 cfu g-1. However, no fluorescent Pseudomonas were found at 60 DAS (July, 2017), 90 DAS (August, 2017), 120 DAS (September, 2017) and 150 DAS (October, 2017). Out of the six isolates (VPJU, VPJL, VPAU1, VPAU2, VPAU3 and VPAU4) of fluorescent Pseudomonas obtained, all the isolates produced IAA and ammonia with varied intensity. Three isolates (VPAU1, VPAU3 and VPAU4) produced HCN and none of the isolates showed siderophore production. The correlation studies between soil temperature, soil pH, EC and C02 evolution with population, revealed that the population of fluorescent Pseudomonas was affected by soil pH and soil EC. However, soil temperature and C02 evolution did not affect the population of fluorescent Pseudomonas. The functional efficiency of the fluorescent Pseudomonas were correlated with soil temperature, soil pH, EC and C02 evolution It was found that soil temperature, soil pH, EC and C02 evolution did not affect the functional efficiency of fluorescent Pseudomonas. All the six isolates obtained m the study were identified and confirmed through 168 rDNA sequencing. The isolates VPAJU, VPAU1 and VPAU2 were identified as Pseudomonas sp. and VPAJL, VPAU3 and VPAU4 isolates were found to be Pseudomonas aeruginosa. The present studies indicated that the inoculated P.fluorescens did not survive in Pokkali fields. The population of fluorescent Pseudomonas showed negative correlation with soil pH and EC. However, soil temperature and C02 evolution did not had any effect on population. The functional efficiency of fluorescent Pseudomonas was not affected by soil temperature, soil pH, EC and C02 evolution. However, further studies on influence of soil edaphic factors and weather variables on host plant and P. fluorescens needs to be studied and develop a suitable PGPR for Pokkali rice.Item Impact of weather variables on the functional efficiency of beneficial microflora in the rhizosphere of black pepper (piper nigrum L.)(Department of Agricultural Microbiology, College of Horticulture, Vellanikkara, 2017) Manju Mohan, E; Surendra Gopal, K