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Papers by Karthikeyan Muthusamy

Brazilian Journal of Plant Physiology, 2006

The effect of soil application of biocontrol agents (Pseudomonas fluorescens, Trichoderma viride ... more The effect of soil application of biocontrol agents (Pseudomonas fluorescens, Trichoderma viride and T. harzianum) in combination with chitin on induction of phenolics and defense enzymes in coconut roots infected with Ganoderma lucidum, the causal agent of Ganoderma disease, was investigated. Soil application of these biocontrol formulations in combination with chitin induced a significant increase in the activities of peroxidase (PO), polyphenol oxidase (PPO), phenylalanine ammonia-lyase (PAL), chitinase and b-1,3-glucanase in the G. lucidum infected palms. Activities of both PAL and PO reached maximum levels within 3 d while the activity of PPO reached the maximum level 6 d after application of a mixture of P. fluorescens, T. viride and chitin. Isozyme analysis revealed that unique PO3 and PPO2 isozymes were induced in coconut palms treated with P. fluorescens + T. viride + chitin. Accumulation of phenolics was recorded 3 d after treatment and reached maximum levels 9 d after treatment application. Activity of chitinase was significantly increased from the third day after treatment imposition and continued to increase up to 9 to 12 d in all treatments. Chitinase isozyme analysis revealed that a unique Chit3 isoform was induced in coconut roots treated with P. fluorescens + T. viride + chitin. The b-1,3-glucanase activity was maximum 9 d after treatment application. The mechanisms by which P. fluorescens + T. viride + chitin reduced the incidence of Ganoderma disease in coconut may be related to its ability to induce defense mechanisms in coconut palms.

World Journal of Microbiology & Biotechnology, 2007

Aflatoxins are carcinogenic, teratogenic and immunosuppressive secondary metabolites produced by ... more Aflatoxins are carcinogenic, teratogenic and immunosuppressive secondary metabolites produced by Aspergillus flavus and Aspergillus parasiticus. Aflatoxin contamination of peanut is one of the most important constraints to peanut production worldwide. In order to develop an eco-friendly method of prevention of A. flavus infection and aflatoxin contamination in peanut, aqueous extracts obtained from leaves of 30 medicinal plants belonging to different families were evaluated for their ability to inhibit the growth of A. flavus in vitro. Among them the leaf extract of zimmu (Allium sativum L. × Allium cepa L.) was the only one that showed antifungal activity against A. flavus and recorded 73% inhibition of A. flavus growth. The antifungal activity of the zimmu extract was significantly decreased upon dialysis with a dialysis membrane having molecular cut off 12 kDa or autoclaving at 121°C for 20 min or boiling at 100°C for 10 min and recorded inhibition of 52, 16 and 21%, respectively. When A. flavus was grown in medium containing zimmu extract the production of aflatoxin B1 (AFB1) was completely inhibited even at a concentration of 0.5%. When AFB1 was incubated with zimmu extract a complete degradation of AFB1 was observed 5 days after incubation. When the roots of zimmu were incubated in water containing 70 ng of AFB1/ml, a reduction (by 58.5%) in AFB1 concentration was observed 5 days after incubation. A significant reduction in the population of A. flavus in the soil, kernel infection by A. flavus and aflatoxin contamination in kernels was observed when peanut was intercropped with zimmu. The population of the fungal antagonist, Trichoderma viride in the zimmu-intercropped field increased approximately twofold.

Archives of Phytopathology and Plant Protection, 2009

Abstract Various isolates of Aspergillus flavus collected from infected maize seeds were tested f... more Abstract Various isolates of Aspergillus flavus collected from infected maize seeds were tested for their ability to produce aflatoxin B1 (AFB1) in vitro. The amount of AFB1 produced by the toxigenic isolates of A. flavus was ranged from 0.57 to 82.91 ng/ml. Among the 51 isolates of A. ...

Aflatoxins, a group of mycotoxins mainly produced by Aspergillus flavus and A. parasiticus, have ... more Aflatoxins, a group of mycotoxins mainly produced by Aspergillus flavus and A. parasiticus, have adverse health effects on humans and livestock that ingest aflatoxin-contaminated food products and feeds. To secure the safety of food and feed, regular monitoring of aflatoxin levels is necessary. In order to understand the magnitude of aflatoxin contamination, a survey was conducted in different agro-ecological zones of Tamil Nadu, India and 242 samples consisting of pre-and post-harvest maize kernels, food products, poultry and livestock feeds were collected from farmers' fields, poultry farms, retail shops and supermarkets and analyzed for aflatoxin B 1 (AFB 1 ) contamination by enzyme-linked immunosorbent assay (ELISA) using antiserum raised against aflatoxin B 1 -Bovine serum albumin (AFB 1 -BSA). The results indicated that 61.3% of the maize kernel samples were contaminated with AFB 1 and the levels of AFB 1 in 26% of the pre-and post-harvest maize kernels exceeded 20 µg/kg. The highest level of AFB 1 (245 µg/kg) was recorded in post-harvest maize kernel samples. In food products AFB 1 was detected only in two samples out of 30 samples tested.

Journal of Plant Interactions, 2007

An attempt was made to study the biocontrol efficacy of antagonistic microorganisms in phylloplan... more An attempt was made to study the biocontrol efficacy of antagonistic microorganisms in phylloplane of rose cv. Edward to manage the black spot (Diplocarpon rosae) disease. Eight antagonistic microorganisms were tested in vivo against the black spot pathogen. Among these, Trichoderma viride and Pseudomonas fluorescens pf1 reduces the mycelial growth significantly. These two biocontrol agents were evaluated for their ability to induce defense-related enzymes and chemicals in plants. Increased activity of phenylalanine ammonia lyase (PAL), peroxidase (PO), polyphenoloxidase (PPO) and total phenolics were recorded in all the biocontrol agents treated leaves. P. fluorescens Pf1 recorded early and increased synthesis of the entire defense-related enzymes and total phenol within 6 days. The application of biocontrol agents induced the defense-related enzymes involved in phenyl propanoid pathway in addition to direct antagonism, which collectively contribute for enhanced resistance against invasion of Diplocarpon rosae in rose.

Journal of Plant Interactions, 2005

Abstract The effect of endophytic Pseudomonas fluorescens isolates Endo2 and Endo35 on induced sy... more Abstract The effect of endophytic Pseudomonas fluorescens isolates Endo2 and Endo35 on induced systemic disease protection against dry root rot of black gram (Vigna mungo L. Hepper) caused by Macrophomina phaseolina was investigated under glasshouse ...

Journal of The Science of Food and Agriculture, 2007

BACKGROUND: The in vitro antifungal activity of zimmu (Allium cepa L. × Allium sativum L.) extrac... more BACKGROUND: The in vitro antifungal activity of zimmu (Allium cepa L. × Allium sativum L.) extract against Aspergillus flavus Link., Fusarium moniliforme Sheld, Curvularia lunata (Wakker) Boedijn and Alternaria alternata (Fr.) Keissler, the fungi associated with grain mold of sorghum, was evaluated. An emulsifiable concentrate (EC) formulation of zimmu extract was prepared and its efficacy in controlling grain mold was tested under field conditions.RESULTS: The leaf extract of zimmu exhibited strong antifungal activity against A. flavus, F. moniliforme, C. lunata and A. alternata and caused in vitro fungal growth inhibition of 73.3%, 71.1%, 70.0% and 74.4%, respectively. Foliar application of zimmu formulation 50 EC at 3 mLL−1 (v/v) concentration 60, 75 and 90 days after sowing significantly reduced the incidence of grain mold and increased the grain weight and grain hardness. A significant reduction in the aflatoxin B1 content in sorghum grains was observed when sorghum plants were sprayed with zimmu formulation 50 EC at 0.3% concentration. Western blot analysis revealed that a thaumatin-like protein (TLP) a molecular mass of 23 kDa that cross-reacted with zeamatin antiserum was expressed at higher levels in sorghum grains after treatment with zimmu formulations.CONCLUSION: The leaf extract of zimmu exhibited antifungal activity against sorghum grain mold fungi. The formulated zimmu extract was significantly effective in reducing the grain mold incidence in sorghum under field conditions. This formulated zimmu extract offers a novel alternative for eco-friendly management of grain mold of sorghum. Copyright © 2007 Society of Chemical Industry

... were designed from ITS region 1 of ribosomal DNA of Ganoderma boninense (ob-tained ... C., NI... more ... were designed from ITS region 1 of ribosomal DNA of Ganoderma boninense (ob-tained ... C., NIEPOLD F. (2000): Development of diagnostic methods for detecting Ganoderma-infected oil ... by some fluorescent pseudomonads against Colletotrichum falcatum Went causing red rot ...

Aflatoxin B1 (AFB1) is a potent carcinogen, teratogen and mutagen. 660 pre-and post-harvest maize... more Aflatoxin B1 (AFB1) is a potent carcinogen, teratogen and mutagen. 660 pre-and post-harvest maize samples were collected from major maize growing areas in Tamil Nadu, India. A flatoxin contamination was observed in 40.22% of the samples tested of which, 22.97% of pre-harvest and 53.93% post-harvest maize samples were found to be infected with AFB1 and 12.05% of the total samples exceeded WHO permissible limit of 20 μg/kg. AFB1 contamination ranged from 0 to 149.32 µg/kg. 28 A. flavus isolates were isolated and grouped into three sets based on aflatoxin producing potential viz., highly aflatoxin producing isolates, medium producing isolates and no aflatoxin producer or traces of aflatoxin producing isolates. The genetic coefficient matrix analysis using random amplified polymorphic DNA (RAPD) with ten random primers revealed minimum and maximum percent similarities among the tested A. flavus strains ranging from 35 to 89%. Cluster analysis separated the three sets of isolates into two groups (groups I and II) with each two subgroup confirming the genetic diversity among the A. flavus isolates from maize.

Brazilian Journal of Plant Physiology, 2006

The effect of soil application of biocontrol agents (Pseudomonas fluorescens, Trichoderma viride ... more The effect of soil application of biocontrol agents (Pseudomonas fluorescens, Trichoderma viride and T. harzianum) in combination with chitin on induction of phenolics and defense enzymes in coconut roots infected with Ganoderma lucidum, the causal agent of Ganoderma disease, was investigated. Soil application of these biocontrol formulations in combination with chitin induced a significant increase in the activities of peroxidase (PO), polyphenol oxidase (PPO), phenylalanine ammonia-lyase (PAL), chitinase and b-1,3-glucanase in the G. lucidum infected palms. Activities of both PAL and PO reached maximum levels within 3 d while the activity of PPO reached the maximum level 6 d after application of a mixture of P. fluorescens, T. viride and chitin. Isozyme analysis revealed that unique PO3 and PPO2 isozymes were induced in coconut palms treated with P. fluorescens + T. viride + chitin. Accumulation of phenolics was recorded 3 d after treatment and reached maximum levels 9 d after treatment application. Activity of chitinase was significantly increased from the third day after treatment imposition and continued to increase up to 9 to 12 d in all treatments. Chitinase isozyme analysis revealed that a unique Chit3 isoform was induced in coconut roots treated with P. fluorescens + T. viride + chitin. The b-1,3-glucanase activity was maximum 9 d after treatment application. The mechanisms by which P. fluorescens + T. viride + chitin reduced the incidence of Ganoderma disease in coconut may be related to its ability to induce defense mechanisms in coconut palms.

World Journal of Microbiology & Biotechnology, 2007

Aflatoxins are carcinogenic, teratogenic and immunosuppressive secondary metabolites produced by ... more Aflatoxins are carcinogenic, teratogenic and immunosuppressive secondary metabolites produced by Aspergillus flavus and Aspergillus parasiticus. Aflatoxin contamination of peanut is one of the most important constraints to peanut production worldwide. In order to develop an eco-friendly method of prevention of A. flavus infection and aflatoxin contamination in peanut, aqueous extracts obtained from leaves of 30 medicinal plants belonging to different families were evaluated for their ability to inhibit the growth of A. flavus in vitro. Among them the leaf extract of zimmu (Allium sativum L. × Allium cepa L.) was the only one that showed antifungal activity against A. flavus and recorded 73% inhibition of A. flavus growth. The antifungal activity of the zimmu extract was significantly decreased upon dialysis with a dialysis membrane having molecular cut off 12 kDa or autoclaving at 121°C for 20 min or boiling at 100°C for 10 min and recorded inhibition of 52, 16 and 21%, respectively. When A. flavus was grown in medium containing zimmu extract the production of aflatoxin B1 (AFB1) was completely inhibited even at a concentration of 0.5%. When AFB1 was incubated with zimmu extract a complete degradation of AFB1 was observed 5 days after incubation. When the roots of zimmu were incubated in water containing 70 ng of AFB1/ml, a reduction (by 58.5%) in AFB1 concentration was observed 5 days after incubation. A significant reduction in the population of A. flavus in the soil, kernel infection by A. flavus and aflatoxin contamination in kernels was observed when peanut was intercropped with zimmu. The population of the fungal antagonist, Trichoderma viride in the zimmu-intercropped field increased approximately twofold.

Archives of Phytopathology and Plant Protection, 2009

Abstract Various isolates of Aspergillus flavus collected from infected maize seeds were tested f... more Abstract Various isolates of Aspergillus flavus collected from infected maize seeds were tested for their ability to produce aflatoxin B1 (AFB1) in vitro. The amount of AFB1 produced by the toxigenic isolates of A. flavus was ranged from 0.57 to 82.91 ng/ml. Among the 51 isolates of A. ...

Aflatoxins, a group of mycotoxins mainly produced by Aspergillus flavus and A. parasiticus, have ... more Aflatoxins, a group of mycotoxins mainly produced by Aspergillus flavus and A. parasiticus, have adverse health effects on humans and livestock that ingest aflatoxin-contaminated food products and feeds. To secure the safety of food and feed, regular monitoring of aflatoxin levels is necessary. In order to understand the magnitude of aflatoxin contamination, a survey was conducted in different agro-ecological zones of Tamil Nadu, India and 242 samples consisting of pre-and post-harvest maize kernels, food products, poultry and livestock feeds were collected from farmers' fields, poultry farms, retail shops and supermarkets and analyzed for aflatoxin B 1 (AFB 1 ) contamination by enzyme-linked immunosorbent assay (ELISA) using antiserum raised against aflatoxin B 1 -Bovine serum albumin (AFB 1 -BSA). The results indicated that 61.3% of the maize kernel samples were contaminated with AFB 1 and the levels of AFB 1 in 26% of the pre-and post-harvest maize kernels exceeded 20 µg/kg. The highest level of AFB 1 (245 µg/kg) was recorded in post-harvest maize kernel samples. In food products AFB 1 was detected only in two samples out of 30 samples tested.

Journal of Plant Interactions, 2007

An attempt was made to study the biocontrol efficacy of antagonistic microorganisms in phylloplan... more An attempt was made to study the biocontrol efficacy of antagonistic microorganisms in phylloplane of rose cv. Edward to manage the black spot (Diplocarpon rosae) disease. Eight antagonistic microorganisms were tested in vivo against the black spot pathogen. Among these, Trichoderma viride and Pseudomonas fluorescens pf1 reduces the mycelial growth significantly. These two biocontrol agents were evaluated for their ability to induce defense-related enzymes and chemicals in plants. Increased activity of phenylalanine ammonia lyase (PAL), peroxidase (PO), polyphenoloxidase (PPO) and total phenolics were recorded in all the biocontrol agents treated leaves. P. fluorescens Pf1 recorded early and increased synthesis of the entire defense-related enzymes and total phenol within 6 days. The application of biocontrol agents induced the defense-related enzymes involved in phenyl propanoid pathway in addition to direct antagonism, which collectively contribute for enhanced resistance against invasion of Diplocarpon rosae in rose.

Journal of Plant Interactions, 2005

Abstract The effect of endophytic Pseudomonas fluorescens isolates Endo2 and Endo35 on induced sy... more Abstract The effect of endophytic Pseudomonas fluorescens isolates Endo2 and Endo35 on induced systemic disease protection against dry root rot of black gram (Vigna mungo L. Hepper) caused by Macrophomina phaseolina was investigated under glasshouse ...

Journal of The Science of Food and Agriculture, 2007

BACKGROUND: The in vitro antifungal activity of zimmu (Allium cepa L. × Allium sativum L.) extrac... more BACKGROUND: The in vitro antifungal activity of zimmu (Allium cepa L. × Allium sativum L.) extract against Aspergillus flavus Link., Fusarium moniliforme Sheld, Curvularia lunata (Wakker) Boedijn and Alternaria alternata (Fr.) Keissler, the fungi associated with grain mold of sorghum, was evaluated. An emulsifiable concentrate (EC) formulation of zimmu extract was prepared and its efficacy in controlling grain mold was tested under field conditions.RESULTS: The leaf extract of zimmu exhibited strong antifungal activity against A. flavus, F. moniliforme, C. lunata and A. alternata and caused in vitro fungal growth inhibition of 73.3%, 71.1%, 70.0% and 74.4%, respectively. Foliar application of zimmu formulation 50 EC at 3 mLL−1 (v/v) concentration 60, 75 and 90 days after sowing significantly reduced the incidence of grain mold and increased the grain weight and grain hardness. A significant reduction in the aflatoxin B1 content in sorghum grains was observed when sorghum plants were sprayed with zimmu formulation 50 EC at 0.3% concentration. Western blot analysis revealed that a thaumatin-like protein (TLP) a molecular mass of 23 kDa that cross-reacted with zeamatin antiserum was expressed at higher levels in sorghum grains after treatment with zimmu formulations.CONCLUSION: The leaf extract of zimmu exhibited antifungal activity against sorghum grain mold fungi. The formulated zimmu extract was significantly effective in reducing the grain mold incidence in sorghum under field conditions. This formulated zimmu extract offers a novel alternative for eco-friendly management of grain mold of sorghum. Copyright © 2007 Society of Chemical Industry

... were designed from ITS region 1 of ribosomal DNA of Ganoderma boninense (ob-tained ... C., NI... more ... were designed from ITS region 1 of ribosomal DNA of Ganoderma boninense (ob-tained ... C., NIEPOLD F. (2000): Development of diagnostic methods for detecting Ganoderma-infected oil ... by some fluorescent pseudomonads against Colletotrichum falcatum Went causing red rot ...

Aflatoxin B1 (AFB1) is a potent carcinogen, teratogen and mutagen. 660 pre-and post-harvest maize... more Aflatoxin B1 (AFB1) is a potent carcinogen, teratogen and mutagen. 660 pre-and post-harvest maize samples were collected from major maize growing areas in Tamil Nadu, India. A flatoxin contamination was observed in 40.22% of the samples tested of which, 22.97% of pre-harvest and 53.93% post-harvest maize samples were found to be infected with AFB1 and 12.05% of the total samples exceeded WHO permissible limit of 20 μg/kg. AFB1 contamination ranged from 0 to 149.32 µg/kg. 28 A. flavus isolates were isolated and grouped into three sets based on aflatoxin producing potential viz., highly aflatoxin producing isolates, medium producing isolates and no aflatoxin producer or traces of aflatoxin producing isolates. The genetic coefficient matrix analysis using random amplified polymorphic DNA (RAPD) with ten random primers revealed minimum and maximum percent similarities among the tested A. flavus strains ranging from 35 to 89%. Cluster analysis separated the three sets of isolates into two groups (groups I and II) with each two subgroup confirming the genetic diversity among the A. flavus isolates from maize.