1. KAUTIR (Kerala Agricultural University Theses Information and Retrieval)
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Item Multifunctional microbial consortium for bio- enriched compost(Department of Agricultural microbiology, College of Agriculture, Vellayani, 2026) Aiswarya PrasanthThe research work on “Multifunctional microbial consortium for bio-enriched compost” was performed at the Department of Agricultural Microbiology, College of Agriculture, Vellayani, Thiruvananthapuram during 2024-2025, with the objective of developing a lignocellulolytic microbial consortium with plant growth promotion potential for conversion of agricultural residues to bio-enriched compost. Microorganisms capable of decomposing lignin, hemicellulose and cellulose in plant material can be effectively used for the management of agricultural residues. Many lignocellulolytic microorganisms possess the ability to promote plant growth by enhancing the nutrient supply and supplying plant growth hormones. Ten lignocellulolytic bacterial isolates obtained from two previous studies were procured from the Department of Agricultural Microbiology and screened for lignocellulolytic potential and plant growth promotion ability. The isolates with superior lignocellulolytic activity and PGP activities were checked for compatibility and used for composting of banana residues. The potential of the resultant bio-enriched compost for supporting plant growth was evaluated by pot culture studies using red amaranthus var. Vaika. Among the ten isolates tested, isolate M1045 recorded the highest cellulolytic index (5.86) and CLSD07 exhibited the maximum ligninolytic index (5.77). Carboxymethyl cellulase (CMCase) activity of the isolates ranged from 3.43 to 9.88 U mL⁻¹ min⁻¹, with M1045 showing the highest activity, followed by CLSD07. Filter paper cellulose (FPase assay) activity was maximum in CLSD07 (2.56 U mL⁻¹ min⁻¹) which was followed by M1045 (2.40 U mL⁻¹ min⁻¹) after 96 h of incubation. Laccase activity peaked in CLSM03 (1.53 U mL⁻¹) and CLSM02 (1.39 U mL⁻¹), while lignin peroxidase and manganese peroxidase were maximally produced by M1045 (18.60 and 3.56 U mL⁻¹, respectively). All isolates synthesized indole-3-acetic acid (IAA), with CLSD07 producing the highest amount (55.36 μg mL⁻¹ in the presence of the precursor, tryptophan). Gibberellic acid production was highest in M1045 (98.54 μg mL⁻¹), followed by G1051 (84.11 μg mL⁻¹). Extracellular ammonia production was maximum in CLSD07 (7.46 μmol mL⁻¹). Six isolates were capable of solubilizing inorganic phosphate in NBRIP medium, with M1045 showing the highest phosphate solubilization index (2.87), followed by G1051 (2.67). Both M1045 and CLSD07 produced siderophores, and four isolates demonstrated antagonistic activity against Rhizoctonia solani, with G1051 showing the greatest inhibition (40.23% over control), followed by W1048 (36.48%). Compatibility analysis revealed that the best performing isolates M1045, CLSD07, W1048, and G1051 exhibited no mutual inhibition, confirming their suitability for consortium development. Morphological and biochemical characterization of the isolates revealed that all the five isolates were Gram-positive, endospore-forming rods. The 16S rRNA gene sequencing showed maximum sequence similarity of the isolates with Calidifontibacillus erzurumensis (M1045), Bacillus velezensis (CLSD07) and Bacillus spp. (W1048 and G1051). The microbial consortium prepared from these isolates was evaluated for its composting efficiency. The four bacterial isolates were cultured in nutrient broth and consortium was prepared by mixing equal volumes of all four isolates. The consortium (~1x108 cfu mL-1) was sprayed over banana residue chopped into small pieces at the rate of 0.1%, 0.2% and 0.5% (v/w). The treatment with 0.5% consortium (T₃) achieved rapid decomposition, attaining the highest temperature (48.2°C) during the fourth week, lowest C:N ratio (12.70:1) by the ninth week, minimum moisture content (21.54%), and lowest bulk density (0.185 g cm⁻³). The resulting compost was nutrient-enriched, with elevated levels of nitrogen (1.41%), phosphorus (0.43%), potassium (1.28%), zinc (14.65 mg kg⁻¹), and copper (53.75 mg kg⁻¹), while heavy metals remained below detectable limits, ensuring safety for agricultural use. However, the C:N ratio fell below 20:1 at the 5th week itself, which is the level acceptable for compost for agricultural purpose. From the initial screening, the treatment with 0.5% microbial consortium (T1) was identified as the most effective based on rapid decomposition rate and minimum time required to attain a lower C:N ratio. The selected treatment was therefore used for subsequent studies comparing its performance with an uninoculated control. The compost used for pot culture studies was prepared by mixing 0.5% v/w of bacterial consortiumwith 600 kg of banana residue. This treatment showed improved compost quality, registering a temperature of 68.64°C during the third week, pH of 7.81, EC of 2.71 dS m⁻¹, and a reduced C:N ratio of 13.05:1, with enhanced nutrient status (N 1.31%, P 0.466%, K 1.243%, Zn 15.01 mg kg⁻¹). Application of bio-enriched compost significantly improved seed germination (96.5%) and germination index (106.3) in red amaranthus. The treatment T1 – bio-enriched compost markedly enhanced growth attributes, including plant height (52.43 cm), number of leaves (57), branches (8.33), and root length compared to control. Overall, the lignocellulolytic bacterial consortium with plant growth promotion potential demonstrated superior composting efficiency, producing a nutrient-rich, agriculturally safe compost that promoted plant growth and could serve as a sustainable alternative to chemical fertilizers.Item Evaluation of plant growth promoting rhizobacteria for pokkali rice(Department of Agricultural Microbiology, College of Agriculture,Vellanikkara, 2023-02-17) Bony Cyriac.; Surendra Gopal, KPokkali rice farming is a time-honoured, environmentally beneficial, traditional and organic method of growing rice. Neither chemical fertilizers nor plant protection agents are used on the crop in this conventional rice farming technique. The present study was undertaken to evaluate a native plant growth promoting rhizobacteria (PGPR) consortia with an objective to screen PGPR for functional efficiency under in vitro and evaluate for plant growth promotion in Pokkali rice. Isolation, characterization and screening of plant growth promoting rhizobacteria such as nitrogen fixers, phosphate solubilizers, potassium solubilizers, fluorescent pseudomonads and Bacillus sp. were carried out from three Pokkali rice growing regions of Ernakulam district (Vytilla, Varapuzha and Kadamakudy). Maximum population of 4 x 103 , 4.66 x 103 and 16.67 x 103 cfu per g of soil were recorded for nitrogen fixers, phosphate solubilizers and Bacillus sp. respectively and fluorescent pseudomonads and potassium solubilizers were absent. A total of 25 predominant isolates were obtained of which 17 isolates belonged to Bacillus sp. and remaining 4 isolates each were nitrogen fixers and phosphate solubilizers. Cultural, morphological and biochemical characters of all the 25 isolates of rhizobacteria showed varied colony morphology and Gram reaction. These isolates were evaluated under in vitro for plant growth promotion activities (production of indole acetic acid, nitrogen fixation, phosphate and potassium solubilization), antagonistic mechanisms (NH3, HCN and siderophore production) and its activities against Xanthomonas oryzae. Quantity of IAA produced by rhizobacterial isolates ranged from 0.46 to 31.27 μg ml-1. Quantity of nitrogen fixed and phosphate solubilized by rhizobacterial isolates varied from 5.72 to 25.21 mg of N g-1 sucrose utilized and 1.98 to 53.19 μg ml-1, respectively. There was no significant difference between potassium solubilized by isolates. Among the rhizobacterial isolates all Bacillus sp. isolates and two isolates each of nitrogen fixers and phosphate solubilizers were found positive for ammonia production. In case of screening of isolates for siderophore production, isolate VYP1 produced moderate orange halo zone on CAS agar media. Isolates VYN1, VYN2, VRB1 and VRB3 recorded poor siderophore activity. Remaining all isolates in the study screened negative for siderophore production. All isolates in the study were found negative for HCN production. Antagonistic activities of isolates to inhibit the rice pathogen Xanthomonas oryzae was evaluated and twenty one isolates screened exhibited antagonistic response against pathogen in which Bacillus isolates KDB4 and KDB5 exhibited excellent antagonism against pathogen. Based on the plant growth promotion activities and antagonistic activities, four most efficient isolates each of nitrogen fixers, phosphate solubilizers and Bacillus sp. were selected for salinity tolerance studies. Among the isolates, nitrogen fixers and Bacillus sp. exhibited maximum salinity tolerance of 12% whereas, phosphate solubilizers exhibited salinity tolerance up to 4% salt concentration. After salinity tolerance studies, three most tolerant nitrogen fixers (VYN2, KDN1 and KDN2), phosphate solubilizers (VYP1, VRP1 and KDP1), and Bacillus sp. (VYB3, VYB6 and KDB1) were selected for compatibility studies. Three most promising PGPR based consortia, PGPR consortia1 (KDN2 + KDP1 + VYB6), PGPR consortia-2 (KDN1 + KDP1 + VYB6) and PGPR consortia-3 (KDN2 + VYP1 + KDB1) were formulated. The three most promising consortia were evaluated under pot culture experiment, along with KAU commercial formulation (PGPR Mix-1) and Organic Package of Practices Recommendations of KAU (2017), at RRS, Vytilla, with Pokkali rice (variety Vytilla-6) as the test crop. All the three native PGPR consortia (T1, T2 and T3) exhibited significant increase in plant height and plants treated with T1 (PGPR consortia 1- KDN2 + KDP1 + VYB6) and T2 (PGPR consortia 2 - KDN1 + KDP1 + VYB6) recorded significantly higher results. Higher number of grains per panicle, grain yield (g per pot) and theoretical grain yield (kg ha-1) were observed in PGPR consortia 1 consisting of isolates KDN2 (N-fixer) + KDP1 (P- solubilizer) + VYB6 (Bacillus sp.). Significantly higher test weight of seeds were observed in T1, T2 and T3 inoculated with native PGPR consortia compared to other treatments. However, the treatments did not have any significant effect on number of tillers, number of panicles per plant and the percentage of chaffy grains produced. The present study indicated that saline tolerant PGPR consortia-1 consisting of Enterobacter cloacae strain KDN2 (N-fixer) + Bacillus subtilis strain KDP1 (Psolubilizer) + Bacillus altitudinis strain VYB1 (Bacillus sp.) was the most promising biofertilizer in enhancing the production of Pokkali rice of Kerala. However, further evaluation of the most promising consortia needs to be done under field conditions to confirm the results.Item Evaluation of pink pigmented facultative methylotrophs (PPFM) for drought and acid tolerance(Department of Agricultural Microbiology, College of Agriculture,Vellanikkara, 2023-03-04) Arya, C.; Surendra GopalAmaranthus (Amaranthus spp.) is one of the most important leafy vegetables in Kerala. It is a storehouse of essential phytonutrients and antioxidants. Amaranth leaves are rich in proteins and higher in fiber content. Among the various cultural practices that increase crop productivity and yield, nutrient management is involved in a significant role in enhancing yield per unit area. Microbial strains are used for the improvement of productivity in sustainable agriculture and are widely accepted methods in different parts of the world. Drought stress affects agricultural productivity and yield. It is an important factor, which harms more than 50 percent of crop yield worldwide. Plant growth-promoting microorganisms like PPFMs supports plant to survive extreme environmental conditions like severe drought. Among the various foliar diseases affecting amaranth, the most serious foliar disease affecting amaranth is leaf blight, which is caused by Rhizoctonia solani. Pink Pigmented Facultative Methylotrophs, plays an important role in stress tolerance and they can stimulate induced systemic resistance against plant pathogens. Hence, the current investigation was carried out on a screening of abiotic stress tolerant PPFMs from phyllosphere as well as rhizosphere regions of amaranth growing areas of Thrissur district for their plant growth promoting and foliar disease management under pot culture studies. PPFMs were isolated from amaranth leaves and roots from ten significant locations where amaranth is being cultivated in Thrissur district. Morphological, cultural and biochemical characters of all PPFM isolates were studied. All bacterial isolates were rod shaped, motile and Gram negative. All the PPFM isolates were screened for plant growth promoting activities under in vitro conditions. In the present study, out of the ten native isolates of PPFM, seven were positive for IAA production. PPFM isolates produced IAA ranging from 3.15 to 15.03 µg ml-1. IAA production by Kod-c (15.03 µg ml-1) was significantly higher than other isolates. This was followed by Nel-c (9.60 µg ml-1), and Kan-a (9.42 µg ml- 1 ). Pat-c and Nel-c recorded significantly superior nitrogen fixation of 0.766 mg/g and 0.756 mg/g, respectively. Lowest amount of nitrogen fixation was shown by reference strain 0.350 mg/g. The amount of phosphate solubilization ranging from 5.99% to 11.15%. ACC deaminase, which plays a significant role in drought mitigation. Out of ten native isolates of PPFM, eight were positive for ACC deaminase activity. The antagonistic activity of all PPFM isolates was assessed against Rhizoctonia solani. Three isolates out of ten inhibited Rhizoctonia solani on potato dextrose medium, Kod-c (62.7 %),Kana(45.7 %) and Nel-c (48.9 %). PPFM isolates were screened for different mechanisms of antagonism like ammonia production, siderophore production and HCN production. Out of ten native isolates, eight were positive for ammonia production. None of the isolates showed the ability for HCN and siderophore production under in vitro conditions. In vitro screening of PPFM isolates for acidic pH and water stress tolerance showed that Nel-c isolate was tolerant to acidic pH upto 3.5 and two isolates namely Nel-c and Kan-a isolates were water stress tolerant upto 20% PEG. PPFM isolates were identified by 16S rRNA gene sequence analysis. The isolates were ranked and best isolates were Kod-c and Kan- a identified as Methylobacterium sp and Nel-c as Methylobacterium populi, which were further evaluated. Evaluation of the three most promising PPFM isolates (Kod-c, Kan-a and Nelc) that exhibited diverse growth promoting and antagonistic activities against Rhizoctonia solani in amaranth was carried out. The three most efficient isolates Kana (Methylobacterium sp), Nel-c (Methylobacterium populi) and Kod-c (Methylobacterium sp) significantly increased plant growth parameters like plant height, number of leaves, days for first flowering and fresh weight of shoots compared to uninoculated plants. Disease severity was also found significantly lower (54.08%) in treatment Nel-c (Methylobacterium populi) at all stages of growth. Methylobacterium populi (Nel-c) was the most promising PPFM isolate for growth promotion and disease management in pot culture studies. The present study proved that native PPFM isolates are more suitable for increased plant growth and disease suppression. Further evaluation under field conditions will help to confirm the results.Item Evaluation of native arbuscular mycorrhizal fungi for growth and management of rhizome rot of ginger (Zingiber officinale)(Department of agricultural microbiology,Vellanikkara, 2023-06-21) Revathy, S.; Preetha, R