Browsing by Author "Meenakumari, K S"

Now showing 1 - 12 of 12

Development of encapsulated formulation of PGPR mix-I and its evaluation
(Department of Agricultural Microbiology, college of Agriculture, Vellayani, 2020) Ayisha, Y L; Meenakumari, K S
The study entitled “Development of encapsulated formulation of PGPR mix-I and its evaluation” was conducted during 2018-2020, in the Department of Agricultural Microbiology, College of Agriculture, Vellayani, Thiruvananthapuram, with the objective to develop calcium alginate based encapsulated formulation of PGPR mix-I and its evaluation for slow release and biodegradation. The component cultures of PGPR mix-I were procured from the Department of Agricultural Microbiology, College of Agriculture, Vellayani for standardization of protocol for preparation of calcium alginate based encapsulated bead formulation of PGPR mix-I. Encapsulated bead formulation of PGPR mix-I was prepared by standard procedures. An experiment was carried out to standardize the protocol for preparation of calcium alginate based encapsulated formulation of PGPR mix–I in completely randomized design with different treatments such as 10% Standard starch, 15% Standard starch, 10% Wheat flour, 15% Wheat flour, 10% Talc, 15% Talc and control treatment as 2% Sodium alginate alone in three replications. Consistent viable count was recorded in encapsulated formulation amended with 10% Standard starch. It exhibited maximum viable count of each of the component cultures of PGPR mix-I as a result of three month population study. A significant decline of total viable population in control treatment was observed in each month compared to encapsulated formulation amended with 10% Standard starch. Based on the population study, encapsulated formulation of PGPR mix-I 10% Standard starch amended was adjudged as the best combination of filler material and hence the shelf life studies of the same had to be continued at monthly intervals at room temperature and refrigerated conditions for six months by serial dilution and plate count method. Significant viable count was recorded in encapsulated beads stored at room temperature condition throughout the shelf life study. The moisture content of beads were also monitored during standardization and shelf life study. During standardization study, moisture content of PGPR mix-I encapsulated beads of each treatment was monitored for a period of three months at monthly intervals at room temperature and it showed a significant variation among treatments in each month. A reduction in moisture content of beads was observed from first month to the end of sixth month in all treatments. Beads amended with 10% Standard starch showed a moisture content of 13.37%, 12.07%, 11.72% and 11.45% after 24 hours of drying, first, second and third month respectively. During shelf life study, 10% Standard starch combination at refrigerated condition showed moisture content in the range of 12.83% to 11.45% while at room temperature the same has recorded values in the range of 12.07% to 10.70%. Evaluation of rate of release of immobilized bacteria from encapsulated beads was determined as per the procedure described by Bashan (1986) and the number of released bacteria was determined by the plate count method in respective selective medium. The higher cfu of component cultures of PGPR mix-I was observed after gentle shaking at 32⁰C for 24hours (T1) in75ml of sterile saline solution. Evaluation of biodegradation of encapsulated beads was studied at weekly intervals in sterile and non-sterile soil with PGPR mix-I inoculated and non-inoculated beads with three replications each (Bashan, 1986). Both the sets were observed weekly for their rate of biodegradation. As per biodegradation scale values like 0, ˃0-0.5, ˃0.5-1, ˃1-2, ˃2-2.5 or 3 was assigned according to the degree of visible degradation which indicates no visible degradation,onset of degradation, slight visible degradation on bead edges, one-half to three-fourth of the beads degraded, 90% of beads become mushy, full degradation (beads are disintegrated into small pieces or not found in the nylon bag) repectively (Bashan, 1986). The PGPR mix-I inoculated beads with bacteria in non-sterile soil showed highest scale of biodegradation throughout the biodegradation study (mean value 1.34) and beads without bacteria in sterile soil showed the lowest scale (mean value 0.52). Kruskal-Wallis rank sum test was done and there was a significant difference between treatments and so multiple comparison was done using Dunn test. During all the four weeks of biodegradation study, treatment T1 (beads with PGPR mix-I in non sterile soil) recorded the highest biodegradation and T4 (beads without PGPR mix-I in sterile soil) recorded the least biodegradation. Treatments T2 (beads with PGPR mix-I in sterile soil) and T3 (beads without PGPR mix-I in non sterile) were on par with both the treatments T1 and T4 in all the four weeks. Treatment wise evaluation of biodegradation of beads was done with Kruskal-Wallis rank sum test and gives a chi-squared value of 46.205 with df = 15 and p-value = 4.932e-05. There was a significant difference between treatments and so multiple comparison was done using Dunn test. Treatment T4 (beads with bacteria in non sterile soil during fourth week) showed significantly different from treatment T13 (beads without bacteria in sterile soil during first week). In the present investigation, calcium alginate based encapsulated beads of PGPR mix-I amended with 10% Standard starch exhibited maximum viable count of component cultures of PGPR mix-I throughout the three months period of standardization study. In terms of evaluation of shelf life and moisture retention during storage, beads stored under room temperature condition was found to be better. The rate of release of component cultures of PGPR mix-I from the encapsulated formulation was more during the first 24-48 hours. Biodegradation studies of encapsulated beads of PGPR mix-I revealed that the beads inoculated with PGPR mix-I in non sterile soil showed highest biodegradation throughout the period of investigation.
Effect of phophatic fertilizer application on vesicular-arbuscular mycorrhizal infection in cowpea
(Kerala Agricultural University, 1992) Meenakumari, K S; Nair, S K
Influence of soil chemical properties on root nodulation by Bradyrhizobium sp. in cowpea, blackgram and greengram
(Kerala Agricultural University, Vellanikara, 2001) Meenakumari, K S; Nair, S K
Isolation and characterization of pink pigmented facultative methylotrophs (PPFMs) associated with paddy
(Department of Agricultural Microbiology, College of Agriculture, Vellayani, 2018) Nysanth, N S; Meenakumari, K S
Isolation and in vitro screening of silicate solubilizing bacteria from paddy rhizosphere
(Department of Agricultural Microbiology, college of Agriculture, Vellayani, 2020) Akhila Subash, P; Meenakumari, K S
The study entitled “Isolation and in vitro screening of silicate solubilizing bacteria from paddy rhizosphere”, was conducted during 2018-2020, in the Department of Agricultural Microbiology, College of Agriculture, Vellayani, Thiruvananthapuram, with the objective of isolation and in vitro screening of bacteria which are capable of solubilizing insoluble form of silicate. Bacteria capable of solubilizing silicates were isolated from the rhizosphere soils collected from different upland and low land paddy fields by serial dilution and plate count method using Bunt and Rovira medium supplemented with 0.25 per cent magnesium trisilicate. Based on the clear halo zone formed around the bacterial colonies on solid media, they were identified as Silicate Solubilizing Bacteria (SSB). Twenty seven isolates of bacteria capable of solubilizing insoluble form of silicate (magnesium trisilicate) were obtained from different locations and were allotted code numbers from SSB 1 to SSB 27. These isolates were subjected to plate and broth assay in Bunt and Rovira medium supplemented with 0.25 per cent magnesium trisilicate. After three days of incubation of test plates at room temperature, all the twenty seven isolates solubilized magnesium trisilicate and produced clearing zone around the bacterial colonies on solid media. The size of clearance zone ranged from 3 mm to 13 mm in plates. The maximum clearance zone of 13 mm was recorded with the isolate SSB 14 which was significantly superior to all other isolates. In broth culture, SSB 20 showed the highest silicate solubilization of 94.65 mg L-1. Based on plate as well as broth assay of all the twenty seven isolates obtained, five isolates viz., SSB 3, SSB 14, SSB 18, SSB 20 and SSB 22 which showed the maximum clearance zone in plate and silicate solubilization in broth were selected as superior isolates. All the isolates obtained were subjected to plate and broth assay for phosphate solubilization in Pikovskaya’s medium and potassium solubilization in Aleksandrov medium. Among them, fourteen isolates showed phosphate solubilization in plates and the clearance zone ranged from 0.87 mm to 5.50 mm. The maximum clearance zone of 5.50 mm was recorded with the isolate SSB 22 which was on par with SSB 23 with 5 mm clearance zone in plate and highest solubilization of 41.92 mg L-1 in broth was shown by SSB 22 which was significantly superior to all other isolates. Twelve isolates showed potassium solubilization in plates and the clearance zone ranged from 2.25 mm to 5.50 mm. Maximum clearance zone of 5.50 mm was recorded with the isolate SSB 8 which was significantly superior to all other isolates. The highest potassium solubilization of 37.50 mg L-1 in broth was observed with isolates SSB 1, SSB 2, SSB 7, SSB 8, SSB 13, SSB 18, SSB 21 and SSB 22 which were found to be statistically on par. Acid production by the five superior SSB isolates, SSB 3, SSB 14, SSB 18, SSB 20 and SSB 22 was detected as a yellow halo around the bacterial colonies in bromophenol blue amended Bunt and Rovira medium. All the five superior isolates tested showed positive results for acid production. The antagonistic activity of the five superior SSB isolates were assessed against major pathogens of paddy viz., Rhizoctonia solani, Magnaporthe grisea, Helminthosporium oryzae and Xanthomonas oryzae pv. oryzae following dual culture method. Out of the five isolates tested, three isolates (SSB 18, SSB 20 and SSB 22) inhibited Rhizoctonia solani. Three isolates (SSB 3, SSB 18 and SSB 22) showed antagonism against Magnaporthe grisea and four isolates (SSB 3, SSB 18, SSB 20 and SSB 22) inhibited Helminthosporium oryzae. The bacterial pathogen, Xanthomonas oryzae pv. oryzae was inhibited by three isolates (SSB 18, SSB 20 and SSB 22). Among all the five isolates tested against different phytopathogens, SSB 18 was found superior with the maximum zone of inhibition of 9.65 mm, 14.45 mm, 10.80 mm and 11.50 mm against Rhizoctonia solani, Magnaporthe grisea, Helminthosporium oryzae and Xanthomonas oryzae pv. oryzae respectively. The five superior isolates were characterized based on morphological and biochemical characters. The results revealed that all the isolates were rod shaped, Gram positive endospore formers. Based on the results of present study, it can be concluded that SSB 3, SSB 14, SSB 18, SSB 20 and SSB 22 are the superior silicate solubilizing bacterial isolates. Among them, SSB 18 showed the highest antagonistic activity against major pathogens of paddy.
Isolation characterization and evaluation of soil microorganisms for bioremediation of chlorpyrifos
(Department of Agricultural Microbiology, College of Agriculture, Vellayani, 2014) Karolin, K P; Meenakumari, K S
The present study on “Isolation, characterization and evaluation of soil microorganisms for bioremediation of chlorpyrifos”, was conducted in the Department of Agricultural Microbiology at College of Agriculture, Vellayani during 2012-14, with the objective of isolation, characterization and evaluation of microorganisms for chlorpyrifos degradation, development of consortia and evaluation of bioremediation potential against chlorpyrifos in vivo. Microorganisms capable of degradation of chlorpyrifos were isolated by enrichment culture technique from identified locations with high residue levels of chlorpyrifos. In all, nineteen isolates comprising eleven bacteria, seven fungi and one actinomycete obtained were subjected to a preliminary screening based on the ability of isolates to utilize 50,100,200,400 and 800 ppm concentrations of chlorpyrifos at intervals of 7, 15, 20, 25, 30 DAI. The six isolates selected (M5, M6, M7, M10, M12, M17) were further evaluated for their ability to degrade different concentrations of chlorpyrifos based on population build up , analysis of chlorpyrifos residue and chloride released into the medium. The fungal isolates, M5, M6, M7 and M17 which recorded significant growth in terms of viable count, maximum reduction in chlorpyrifos residue and release of chloride were selected and subjected to morphological and molecular characterization. The isolates M5, M6, M7 and M17 were identified as Isaria farinosa, Aspergillus fumigatus, Trichoderma viride and Penicillium griseofulvum respectively. In order to develop a consortium, the compatibility of the selected fungal isolates - M5, M6, M7 and M17 was tested by co-culturing in liquid MSM and by dual culture technique. All the fungal isolates were compatible and no inhibition could be recorded. A consortium of the four fungal isolates was prepared in liquid formulation and its ability to degrade different concentrations of chlorpyrifos was studied under in vitro conditions on 25th day of inoculation. The percentage degradation of chlorpyrifos by the isolates increased with increase in concentrations, but showed a decline at 800 ppm. The percentage degradation of chlorpyrifos was higher in consortium compared to individual isolates under in vitro conditions. The developed liquid consortium was evaluated in sterilized soil spiked with 100 and 400 ppm concentration of chlorpyrifos with cowpea as the test crop. Significant reduction in all biometric characters was observed due to spiking with chlorpyrifos at 100 and 400 ppm concentrations. Application of consortium in soil spiked with chlorpyrifos enhanced all the biometric characters and reduced the residue of chlorpyrifos. The study also established efficient colonization of the chlorpyrifos degraders present in the consortium in the rhizosphere of cowpea.
Management of bacterial wilt of chilli caused by Ralstonia solanacearum(E.F Smith) yabuuchi et al. using AMF and flurescent pseudomonads
(Department of Plant Pathology, College of Agriculture, Vellayani, 2005) Sonia Basheer; Meenakumari, K S
Management of bacterial wilt of chilli caused by Ralstonia solanacearum (E.F. Smith) Yabuuchi et al. using AMF and Pseudomonas fluorescens was studied. The pathogen was isolated and pathogenicity proved. Based on the cultural, morphological, physiological and biochemical characteristics, the isolate was identified as R. solanacearum. Out of the ten native AMF cultures screened, cultures M5 and M7 were found effective for disease suppression and growth improvement in chilli.Pseudomonas spp. were isolated from phyllosphere and rhizosphere of chilli plants collected from different locations of Thiruvananthapuram district. Out of the 45 isolates subjected to in vitro screening by dual culture technique, two best isolates viz., Pf-14 and P-1 were selected. These isolates, Pf-14 and P-1 were subjected to biochemical characterization and were tentatively identified as Pseudomonas aeruginosa and Pseudomonas fluorescens biovar 2 respectively.Interaction of efficient native isolates of AMF and P. fluorescens isolates on disease suppression and growth improvement in chilli was studied. Talc based formulation of the two best native isolates, Pf-14 and P-1 were applied as soil drench and foliar spray. Dual inoculation of chilli seedlings with M5 and P-1 recorded the least disease incidence. The growth, biomass production and yield was highest for the treatment M7P1R0 which is a combination of AMF culture M7 and Pseudomonas culture Pf-14. The application of antibiotic agrimycin was found ineffective in suppressing bacterial wilt pathogen.The present study forms the first report of the synergistic interaction of AMF and P. fluorescens for the management of bacterial wilt and growth improvement in chilli. The technology of combined inoculation of AMF and P. fluorescens could be recommended for adoption by the vegetable farmers of Kerala after confirming the results under field conditions.
Management of damping off and improvement of growth in chilli with native species of arbuscular mycorrhizae
(Department of Plant Pathology, College of Agriculture, Vellayani, 2001) Kavitha, K; Meenakumari, K S
Management of damping off, the most destructive disease of chilli both 111 nursery and main field incited by Pythium aphanidermatum (Edson) Fitz. using native AMF was attempted in the present investigation. Out of nine native AMF and one identified culture (Glomus mosseae) screened, the cultures Ms and M9 were found effective for suppression of damping off and growth improvement in chilli. Application of AMF inoculum in the nursery furrows along with chilli seeds was very effective for rapid and easy colonization of AMF. Likewise application of AMF inoculum at the rate of 850 g m-2 was selected as the economic dose for achieving satisfactory colonization of AMF. Azospirillum spp. were isolated from chilli roots collected from different locations of Thiruvananthapuram district. The in vitro nitrogen fixing capacity of the isolates ranged between 11.2 and 20 mg N s' of malate and IAA production between 21 and 55 ug mrl. Six best isolates which performed well under in vitro screening were selected an-d subjected to in vivo screening for growth, biomass production and yield in chilli. The isolates Az-l and Az-2 which performed well both under in vitro and in vivo screening were selected for further studies. Based on the characterization studies it was found that the isolate Az-l is related to Azospirillum lipoJerum and Az-2 is similar to Azospirillum brasilense. The isolate Az-l grew well at pH 5,6 and 7 whereas the isolate Az-2 grew well at pH 6 and 7. In the study on the interaction of native AMF and Azospirillum on damping off disease suppression, pre-inoculation of chilli seedlings with M9 culture alone recorded the least disease incidence. Eventhough dual inoculation of AMF and Azospirillum could suppress the damping off, Azospirillum had no direct effect on disease suppression. However dual inoculation of AMF and Azospirillum (M9A2PO) significantly increased the growth, biomass production and yield in chilli. The present study forms the first report of the synergistic effect of AMF and Azospirillum for the management of damping off and growth improvement in chilli. The present investigation emphasizes the importance of pre-inoculation of AMF in the chilli nursery as a prophylatic measure to prevent pathogen attack. The technology of combined inoculation of AMF and Azospirillum could be recommended for adoption by the vegetable farmers. Eventhough the present study was carried out in chilli, the same cultures could be recommended for all transplanted solanaceous vegetables after confirming the results through field trials.
Microflora associated with earthworms and vermicompost
(Kerala Agricultural University, 1997) Nair, S K; Naseema, A; Meenakumari, K S; Prabhakumari, P; Peethambaran, C K
Screening of pink pigmented facultative methylotroph isolates for water stress tolerance and yield in paddy
(Department of Agricultural Microbiology, College of Agriculture, Vellayani, 2019) Riyas, N K; Meenakumari, K S
Sensitivity of blue green algae to soil reaction - A factor affecting its efficient use as biofertilizer
(Kerala Agricultural University, 1993) Nair, S K; Shehana, R S; Girija, V K; Meenakumari, K S
Standardization of liquid formulation of PGPR MIX-1 and its evaluation for plant growth promotion in amaranthus(amaranthus tricolor L.)
(Department of Agricultural Microbiology,College of Agriculture, Vellayani,Thiruvananthapuram, 2018) Gokul K Gopi; Meenakumari, K S