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ThesisItem Open Access Evaluation of native rhizosphere microflora for plant growth promotion and management of fusarium yellows in ginger(Department of Agricultural Microbiology, College of Horticulture, Vellanikkara, 2016) Rekha, K G; KAU; Surendra Gopal, KA study was undertaken on “Evaluation of native rhizosphere microflora for plant growth promotion and management of Fusarium yellows in ginger”. The main objectives were to enhance the growth and yield of ginger using native beneficial microorganisms isolated from wayanad district and to manage Fusarium yellows disease in ginger by using antagonistic microorganisms. Rhizosphere soils were collected from ten different locations of healthy and diseased ginger fields of Wayanad district. The predominant beneficial microorganisms namely nitrogen fixing bacteria, phosphate solubilizing bacteria, Bacillus sp., Pseudomonas fluorescens, Streptomyces sp., and Trichoderma sp. were isolated. The highest population of nitrogen fixers (1.4x104 cfu/g), fluorescent pseudomonads (9x104 cfu/g), and Trichoderma sp. (6x103 cfu/g) were obtained from Pulpalli location. Phosphate solubilizing bacteria (9x103 cfu/g) and Streptomyces sp. (6x104cfu/g) were highest in Kappikunnu and maximum population of Bacillus sp. (2.3x104 cfu/g) was recorded in Mayilumpadi. The isolates were screened for plant growth promotion and antagonistic activity under in vitro condition. Maximum nitrogen fixation was recorded in NFMh isolate (0.43 mg/g of sucrose utilized) among nitrogen fixers. Highest IAA (35.02 μg/ ml), HCN and siderophore production were recorded by NFAh (nitrogen fixer) isolate. Among the phosphate solubilizers, highest P- solubilization (450.00%) was by PSBAh isolate where as, IAA (33.07 μg/ ml) and HCN was shown by PSBMh isolate. Among the isolates of Bacillus sp. The maximum P- solubilization index (182.99%) was recorded by BsAh isolate and the least (137.43%) by BsKUh isolate. Highest IAA (14.54 μg/ml) was produced by BsMh isolate (Mayilumpadi) and the least (12.92 μg/ml) by BsAh isolate (Appade). Out of the ten isolates tested for HCN production, only three BsMh, BsKuh and BsPTd isolate resulted moderate level of HCN production. Only one isolates, BsMh positive for siderophore production. All the seven isolates of fluorescent pseudomonads the highest (241.57%) psolubilization was in PfMh isolate and lowest (190.11%) by the isolate PfKh. Highest IAA production was (16.75 μg/ml) by the isolate PfKh from Kappikunnu and the lowest (12.13 μg/ml) by PfPh isolate. Hydrogen cyanide production of all the isolates were tested and that isolates PfPh and PfKUh produced highest HCN under in vitro screening. Siderophore production was produced only by three isolates PfKh, PfMh, and PfPh. Among the eight isolates of Streptomyces sp. the maximum P- solubilization index (176.99%) was recorded by StrAh isolate and the least (153.76%) by StrPh isolate. Highest IAA (11.63 μg/ml) was produced by StrMh isolate (Mayilumpadi) and the least (10.41 μg/ml) by StrKUh isolate (Kurumankotta). Two isolates StrMh and StrPh resulted moderate level of HCN production. Four isolates StrMh, StrPh, StrAh and StrAd isolates resulted siderophore production. StrPh (Pulpalli) isolate resulted excellent siderophore production. All the isolates of Trichoderma sp. did not solubilized phosphorus and IAA under in vitro screening Two isolates TrPh and TrKUh produced moderate HCN under in vitro screening. Siderophore production was produced only by three isolates TrKh, TrMh, and TrAh. Selected isolates of Bacillus sp., Pseudomonas fluorescens, Streptomyces sp., Trichoderma sp., were tested for their antagonistic activity against the major soil borne pathogens of ginger viz., Fusarium oxysporum, Pythium aphanidermatum, Rhizoctonia solani and Ralstonia solanacearum under in vitro condition. The isolate BsAh showed maximum antagonistic activity against F. oxysporum (64.08 per cent) and P. aphanidermatum (15. 09 per cent) where as, BsKh isolate was antagonistic against R. solani (47.09 per cent) and BsMh isolate showed 43.81per cent inhibition against R. solanacearum. Among Pseudomonas fluorescens, PfKh showed 59.43 per cent inhibition against F. oxysporum where as PfAh isolate recorded 33.71 per cent inhibition against P. aphanidermatum, 27.20 per cent aginst R. solani and PfPh isolate showed 31.32 per cent inhibition against R. solanacearum. Among the isolates of Streptomyces sp., StrPh isolate recorded maximum inhibition (67.78 per cent) against F. oxysporum, 43.11 per cent inhibition against R. solani and 34.23 per cent against R. solanacearum. TrAh isolate (Trichoderma sp.,) showed highest (78.93 per cent) inhibition against F. oxysporum, 51.30 per cent inhibition against P. aphanidermatum and 43.27 per cent against R. solani. However, TrMh isolate shown 15.96 per cent inhibition against R. solanacearum. Three most efficient isolates of nitrogen fixers (NFMh, NFPh, NFKh), phosphate solubilizing bacteria (PSBPh, PSBKh, PSBAh), Bacillus sp., (BSMh, BSAh, BSKUh), fluorescent pseudomonads (PFKh, PFPh, PFAh), Streptomyces sp., (StrPh, StrMh, StrKh) and Trichoderma sp., (TrAh, TrKUh, TrPh) obtained under in vitro studies were further screened under pot culture studies. Among the isolates PSBPh (T4) was found to be the most efficient in enhancing the growth and yield of ginger where as the isolate TrKUh (T11) was the most efficient isolate for the management of Fusarium yellows disease. These two isolates were identified as Burkholderia cepacia (PSBPh) and Trichoderma harzianum (TrKUh). The present study clearly showed that Burkholderia cepacia (PSBPh) and Trichoderma harzianum (TrKUh) were effective for plant growth promotion and management of Fusarium yellows in ginger respectively. However, these isolates have to be evaluated for efficiency under field conditionThesisItem Open Access Development of inoculant cultures of zinc solubilizing microorganisms(Department of Agricultural Microbiology, Vellayani, 2016) Aathira S Kumar; KAU; Anith, K NThe study entitled “Development of inoculant cultures of zinc solubilising microorganisms” was conducted at College of Agriculture, Vellayani during the period 2014 - 2016 with the objective of isolation, characterization and evaluation of zinc solubilising microorganisms from soils of Kerala and to develop inoculant culture of the best zinc solubilising isolate. Microorganisms capable of solubilising zinc were isolated from Agroecological units 20, 21 (Wayanad) and 8 (Thiruvananthapuram) by serial dilution technique on Bunt and Rovira medium containing 0.1% insoluble zinc oxide. Ten isolates of bacteria capable of solubilising insoluble forms of zinc (zinc oxide) were obtained and allotted code numbers from ZSB-1 to ZSB-10. These were subjected to plate assay and broth assay in media supplemented with 0.1 per cent insoluble forms of zinc as zinc oxide or zinc phosphate. After three days of incubation of test plates, all the ten isolates solubilised zinc and produced clearing zone around the colonies on solid media. The size of the solubilisation zone ranged from 8.67 mm to13.33 mm in zinc oxide and from 1.00 mm to 5.33 mm in zinc phosphate incorporated medium. In broth culture, maximum solubilisation of zinc in both sources was observed on 30th day in the range of 35.91 ppm to 104.08 ppm in zinc oxide supplemented medium and 1.38 ppm to 4.15 ppm in zinc phosphate supplemented medium. The isolate ZSB – 4 showed maximum solubilisation of zinc in plate assay and broth assay. For soil incubation study, the isolate with maximum zinc solubilisation (ZSB – 4) was inoculated in zinc deficient soils and analysed for the soil chemical parameters and population dynamics of the bacterial isolate for a period of three months. The treatments were designed as T1 and T2 with Zn at two levels as ZnO, T3 with Zn solubilising culture alone @ 2 kg ha-1, T4 and T5 with Zn solubilising culture @ 2 kg ha-1 supplemented with Zn at two levels as ZnO and T6, the absolute control had no insoluble zinc supplementation and inoculation with the bacterial isolate. The isolate ZSB – 4 significantly increased the available zinc content in soil from 0.55 ppm to 9.47 ppm in treatment T4 (ZSB – 4 @ 2 kg ha-1 + zinc oxide @ 1 kg ha-1) during the incubation period. The same treatment registered the highest mean value for available phosphorus content, 12.09 kg ha-1 and 12.26 kg ha-1 respectively for the 2nd and 3rd month. There was an increase in oxidisable organic carbon content in the 3rd month for treatments T4 (1.44%), T5 (1.43%) and T3 (1.38%) and it was maximum in T4 which was statistically on par with T3 and T5. On the 3rd month, there was a decrease in the available boron content in soil for the treatments T3 (0.30 ppm) and T5 (0.34 ppm) when compared with previous months and the treatment T4 (0.33) maintained the level of boron. The total zinc content of the soil ranged from 0.05 % to 0.08 % during the entire three months and the mean values had no significant difference among treatments. The maximum colony count of 9.3 x 103 cfu g-1 of soil was recorded in the treatment T4 during the 3rd month which was on par with T5 (9.1 x 103 cfu g-1) and T3 (8.8 x 103 cfu g-1). The best isolate ZSB – 4 was subjected to molecular characterization and it was revealed that the organism is Bacillus cereus. Different carrier materials like talc, lignite, vermiculite, vermicompost and perlite were used in the present study to assess survival of ZSB – 4. Among the different carriers tested, the talc powder supported the maximum population of 3.9 x 108 cfu g-1 during the 3rd month. Based on the results of present study it can be concluded that application of talc based formulation of the zinc solubilising bacteria ZSB – 4 (Bacillus cereus) @ 2 kg ha-1along with zinc oxide @ 1 kg ha-1 was found to increase zinc content in soil after incubation. Based on the survival of the isolates in different carriers for the development of inoculant cultures, talc was found to be most suitable carrier for the formulated product.ThesisItem Open Access Exploration of native mineral phosphate solubilizing microorganisms as biofertilizer for the acidic soils of Kerala(Department of Agricultural Microbiology, College of Horticulture, Vellanikkara, 2016) Saranya, K S; KAU; Girija, DA study was undertaken on ‘Exploration of native mineral phosphate solubilizing microorganisms as biofertilizer for the acidic soils of Kerala’. The main objective was to exploit native microorganisms with mineral phosphate solubilization and plant growth promoting activities for the acidic soils of Kerala.
