Browsing by Author "Litty Thomas"

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    Antagonistic activity of coconut rhizospheric and endophytic Bacillus spp. against Ganoderma applanatum and Thielaviopsis paradoxa
    (2011) Priya George; Alka Gupta; Murali Gopal; Chandra Mohanan, R.; Litty Thomas; George V. Thomas
    A screening study was carried out to detect the antagonistic potential of Bacillus spp. against Ganoderma applanatum and Thielaviopsis paradoxa, fungal pathogens of coconut. A total of 327 heat resistant, endospore producing bacilli were isolated from the rhizospheric soil and roots of coconut growing in Kerala, Tamil Nadu, Karnataka, Andhra Pradesh and Maharashtra. All the isolates were tested for antifungal activity against G. applanatum and T. paradoxa by dual cultural technique on nutrient agar medium. The zone of inhibition was measured and percentage of inhibition was calculated. More than 90 % of the rhizospheric and root endophytic isolates were found to effectively inhibit the mycelial growth of G. applanatum, with a maximum inhibition zone of 12 mm and percentage inhibition ranging from 44 to 91. About 86 % of the isolates inhibited the mycelial growth of T. paradoxa, with a maximum inhibition zone of 14 mm and percentage inhibition ranging from 42 to 93. Further tests of potent antagonists revealed that more than one mode of mechanisms like production of chitinase, siderophores, HCN, antibiotics, ammonia, β-1,3- glucanase and salicylic acid may be involved in the antagonistic activities. The results of this study revealed 13 Bacillus spp. having potential for use as biocontrol agents against G. applanatum and T. paradoxa, fungal pathogens of coconut.
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    Efficacy of rhizospheric Bacillus spp. for growth promotion in Theobroma cacao L. seedlings
    (2011) Litty Thomas; Alka Gupta; Murali Gopal; Priya George; George V. Thomas
    Cocoa (Theobroma cacao L.) trees harbour a diverse microbial communities of epiphytic, rhizospheric and endophytic organisms, many possessing plant growth promoting abilities. Since plant growth promoting rhizobacteria (PGPR) can significantly promote plant health and sustain agriculture by a variety of mechanisms, their potential for use in cocoa crop can be exploited. PGPR based products with strains of Bacillus are more successful in the field due to the fact that they produce spores which offer them ability to tolerate wide range of biotic and abiotic stress. This paper highlights the screening of selected Bacillus spp., isolated from the rhizosphere of cocoa growing in different agro-climatic and soil types in Kerala, Karnataka, Tamil Nadu and Andhra Pradesh, on the growth parameters of cocoa seedlings when grown in polybags. Statistically significant increase (P = 0.05) over the control was observed in the tested parameters such as total seedling length (up to 37 %), total fresh weight (up to 73 %) and total dry weight (up to 56 %) of cocoa seedlings when they were inoculated with Bacillus spp. The overall improvement in seedling vigour through a significant increase in various growth parameters indicated that the Bacillus strains (Bacillus sp. ASB3, ASB12, CSB8, CSB16 and CSB17) had positive and effective plant growth promoting ability on cocoa seedlings. In addition to its plant growth promotion abilities the potential PGPR Bacillus spp. (isolates CSB8, CSB16, CSB17 and ASB12) also showed high abiotic stress tolerance, growing at higher temperatures (> 50 0C) and salt concentrations (10 % NaCl). These PGPRs were identified according to Bergey’s Manual of Determinative Bacteriology and confirmed by Biolog® GEN III microplate identification system. The results of this study points to the potential of rhizospheric Bacillus spp. to enhance growth and vigour of cocoa seedlings when grown in polybags.
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    Evaluation of plant growth promotion ability of fluorescent Pseudomonas spp. on cacao (Theobroma cocoa L.) seedlings
    (2012-11) Litty Thomas; Alka Gupta; Murali Gopal; Priya George; George V. Thomas
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    Evaluation of rhizospheric and endophytic Bacillus spp. and fluorescent Pseudomonas spp. isolated from Theobroma cacao L. for antagonistic reaction to Phytophthora palmivora, the causal organism of black pod disease of cocoa
    (2011) Litty Thomas; Alka Gupta; Murali Gopal; Chandra Mohanan, R.; Priya George; George V. Thomas
    Biological control has assumed significance in the research programmes on disease management of cocoa due to the increasing concern on the detrimental effect of agrochemicals on environment and the presence of residues in food products. This study was conducted to evaluate the potential of Bacillus spp. and fluorescent Pseudomonas spp. isolated from cocoa roots and rhizosphere for their antagonistic reaction against Phytophthora palmivora (Butl.) Butl., causing black pod disease of cocoa. A total of 519 isolates obtained from the rhizosphere and roots of cocoa trees in different locations in South India were evaluated for their antagonistic reaction to P. palmivora, under in vitro conditions on Carrot Dextrose Agar (CDA). Out of the 519 cocoa isolates (359 Bacillus spp. and 160 fluorescent Pseudomonas spp.), 95 isolates (44 rhizospheric and 45 endophytic Bacillus spp; and 6 rhizospheric fluorescent Pseudomonas spp.) were found to be antagonistic to P. palmivora. Four Bacillus spp., one from Pollachi (Bacillus sp. PSB6) and three from Kasaragod (Bacillus sp. KGSB5, Bacillus sp. KGSB11 and Bacillus sp. KGSB26) effected a maximum of 57 % mycelial growth reduction of the fungal pathogen. None of the endophytic fluorescent Pseudomonas spp., showed antagonism against the black pod pathogen. Bacillus spp. isolated from Tamil Nadu showed higher antagonistic potential (48 % of rhizospheric and 76 % of endophytic Bacillus spp.) than bacterial isolates obtained from other states. Further studies with these antagonists showed that 35 %, 18 %, and 56 % of the isolates produced siderophore, HCN and antibiotics respectively.The isolates showing antagonistic activity (89 Bacillus spp. and 6 Pseudomonas spp.) against the fungal pathogens can be used in developing bio-control agents.
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    In vitro antagonism of rhizospheric fluorescent pseudomonads of coconut against Ganoderma applanatum and Thielaviopsis paradoxa, fungal pathogens of coconut
    (2012-08) Priya George; Alka Gupta; Murali Gopal; Chandra Mohanan, R.; Litty Thomas; George V. Thomas
    A total of 156 fluorescent pseudomonads were tested for antagonistic activity towards G. applanatum and T. paradoxa in a dual-plate assay on King’s B agar plates. Eight percent of the total fluorescent pseudomonads showed antagonism towards G. applanatum (inhibition ranging from 39% to 73%) and 16% of the isolates inhibited T. paradoxa in the range of 20% - 76%. Moreover, eight percent of the fluorescent pseudomonads significantly inhibited both pathogens tested. They were found to possess some important biocontrol traits such as HCN, siderophores, ammonia and antibiotics. Among them fluorescent Pseudomonas spp. KiSF 17 and KiSF 16 exhibited strong antagonistic activity. They were identified as P. aeruginosa by Biolog® GEN III microplate identification system and confirmed by 16S rDNA sequencing. The present studies revealed the survival of useful bacterial antagonists in the rhizosphere of coconut palm, which have the potential to be used as a biocontrol agent.
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    Multifarious beneficial traits and plant growth promoting potential of Serratia marcescens KiSII and Enterobacter sp. RNF 267 isolated from the rhizosphere of coconut palms (Cocos nucifera L.)
    (2013) Priya George; Alka Gupta; Murali Gopal; Litty Thomas; George V. Thomas
    Two plant growth promoting bacteria designated as KiSII and RNF 267 isolated from the rhizosphere of coconut palms were identified as Serratia marcescens and Enterobacter sp. based on their phenotypic features,BIOLOG studies and 16S rRNA gene sequence analysis.Both bacteria exhibited phosphate solubilization, ammonification, and production of indole acetic acid, b-1, 3 glucanase activities and 1-aminocyclopropane-1-carboxylate-deaminase activity. They could also tolerate a range of pH conditions, low temperature and salinity (NaCl). In addition, S. marcescens KiSII exhibited N- fixation potential,chitinase activity, siderophore production and antibiotics production. Seed bacterization with these bacteria increased the growth parameters of test plants such as paddy and cowpea over uninoculated control in green house assay. In coconut seedlings, significant increase in growth and nutrient uptake accompanied with higher populations of plant beneficial microorganisms in their rhizospheres were recorded on inoculation with both the PGPRs. The present study clearly revealed that PGPRs can aid in production of healthy and vigorous seedlings of coconut palm which are hardy perennial crops. They offer a scope to be developed into novel PGPR based bioinoculants for production of elite seedlings that can benefit the coconut farming community and the coconut based ecology.
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    Plant growth promoting potential of Bacillus spp. isolated from rhizosphere of cocoa (Theobroma cacao L.)
    (2010-08) Litty Thomas; Alka Gupta; Murali Gopal; Priya George; George V. Thomas
    A total of 185 bacilli were isolated from rhizosphere soils of cocoa from various locations in southern states of India and they were subsequently screened in vitro for plant growth promoting (PGP) traits such as production of IAA, ACC deaminase, HCN, siderophore, chitinases and antibiotics, ammonification, ability to grow on N-free media and solubilization of phosphates. It was found that 91 % of the Bacillus spp. isolates produced ammonia; less than 20 % isolates produced HCN and siderophore; IAA production was noticed in 22 % isolates and 19 % isolates were found to produce antibiotics. About 49 % of 185 Bacillus isolates solubilized phosphates; 50 % of isolates could grow on N-free medium and 71 % of isolates showed ACC deaminase production. The isolates could exhibit upto six PGP traits, which may promote plant growth directly or indirectly or synergistically. Thirty six isolates were selected based on the in vitro plant growth promotion potential and were further screened for plant growth promotion under Environmental Plant Growth Chamber (EPGC) conditions. Thirty isolates which showed increase in seedling length in EPGC study were further screened for in vivo growth promotion in cowpea seedlings under greenhouse conditions. Out of 30 isolates tested, 11 were found to increase seedling length and fresh and dry weight of cowpea seedlings when compared to the uninoculated control. The results of this study points to the potential of rhizospheric soil bacilli for plant growth promotion. Further studies are necessary to confirm their effectiveness and potential in the field.
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    Plant Growth Promoting Rhizobacteria (Pgpr) for Growth Improvement in Cocoa
    (2011) Murali Gopal; Litty Thomas; Alka Gupta; Priya George; George V. Thomas
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    Systematic Screening Strategies for Identifying Elite Plant Growth Promoting Rhizobacteria for Coconut (Cocos nucifera L.)
    (2018) Priya George; Alka Gupta; Murali Gopal; Litty Thomas; George V. Thomas