Informatics Publishing Limited

M. Jayasekhar ¹, K. Manonmani ¹, C. Gailce Leo Justin ¹

Affiliations
1 Horticultural Research Station, Krishi Vigyan Kendra, Pechiparai-629 161, IN

Abstract

Stem rot disease of vanilla caused by Fusarium oxysporum f.sp. vanillae is a major constraint in its cultivation in Kanyakumari District. The in vitro studies on the mycelial growth of the pathogen expressed the superior efficacy of the native isolate of Pseudomonas fluorescens (Pf_NI) that recorded an inhibition zone of 25.00mm and was followed by T. harzianum. Under field conditions soil application of Pf(_NI) followed by carbendazim spray (0.2%) after 30 days of Pseudomonas application recorded the lowest disease incidence of 3.77, 4.03 and 3.67 per cent in three years and exerted 79.95, 80.50, 80.48 per cent reduction in disease over the control plot respectively. Among the bioagents, the soil application of Pf(_NI) followed T. harzianum after 30 days and another dose of Pf(_NI) after 30 days recorded a significant disease reduction of 69.84, 68.24 and 70.21 per cent in three consecutive years.

Full Text

     

K. Manonmani ¹, R. Bhaskaran ², R. Jagannathan ², M. Jayasekhar ¹

Affiliations
1 Krishi Vigyan Kendra, Pechiparai, Kanyakumari, IN
2 Agricultural College and Research Institute TNAU, Madurai-625 002, IN

Abstract

Studies were conducted to screen out the compatible host and pathogen combination with acid lime and canker causing pathogenic culture of Xanthomonas axonopodis Pv. Citri (Xac). Among the 21 isolates collected from acid lime cultivating areas of Tamil Nadu, isolate I₃ was found to be the most virulent. This compatible combination was tested under controlled environment condition at 28°C and its effect on biochemical parameters of host metabolism was studied. The biochemical changes in the host during the course of pathogenicity include, slight increase in protein, phenol, phenyl alanine ammonia lyase (PAL), β-1, 3-glucanase and chitinase enzymes. Significant increase in the activities of peroxidase (POX), polyphenol oxidase (PPO) and catalase was observed in the infected tissues. Total and non-reducing sugars decreased, but reducing sugar content increased slightly.

Keywords

Acid Lime, Pathogenicity, Xanthomonas axonopodis Pv. Citri, Biochemical Changes.

Full Text

     

K. Manonmani ¹, M. Jayasekhar ¹, C. Gailce Leo Justin ¹, T. Thangaselvabai ¹

Affiliations
1 Krishi Vigyan Kendra, Horticultural Research Station (TNAU), Pechiparai-629161, IN

Abstract

Bactericidal action ofsome selected herbal extracts viz., Acalypha indica, Achyranthes aspera, Aloe vera, Azadirachta indica, Datura metal, Hibiscus rosasinensis, Nerium oleander, Ocimum sanctum, O. basilicum, Phyllanthus emblica, Polyalthia longifolia, Piper betle, Punica granatum, Solanum torvum and Solanum trilobatum were tested in vitro against the growth of citrus canker disease causing pathogen, Xanthomonas axonopodis pv. citri (Xac). The leaf extract of P. longifolia followed by A. aspera recorded the maximum growth inhibition of 9.77mm and 8.47mm diameter respectively. The 20-40% ammonium sulphate fraction of A. aspera and 40-60% fraction of P. longifolia exhibited inhibitory action on in vitro growth of the pathogen. The molecular weight of the fractions of leaf extracts was found to be 30 kDa and 19 kDa for P. longifolia and A. aspera respectively.

Keywords

Herbal Extracts, Citrus Canker, Xanthomonas axonopodis pv. Citri.

Full Text

     

K. Manonmani ¹, M. Jayasekhar ¹, M. Muthusamy ¹

Affiliations
1 Krishi Vigyan Kendra, Pechiparai-629161, IN

Abstract

Rice is affected by number of fungal, bacterial and viral diseases. Among the fungal diseases, sheath rot caused by Sarocladium oryzae has been reported to cause considerable loss in yield. Bacterial biocontrol agents viz., Pseudomonas fluorescens (Pf₁) and Bacillus subtilis have been formulated in different carriers viz., gypsum, peat soil and talc powder. Their longevity and biocontrol efficacy against sheath rot incidence were assessed under artificially inoculated condition. The results revealed that gypsum based formulation of two bioagents were effective in controlling the disease by recording the disease incidence of 10.67 per cent and 12.00 per cent respectively. Under field condition also, gypsum based formulation of these biocontrol agents were found to be more effective in controlling sheath rot incidence than the talc and peat based formulations.

Full Text

     

K. Manonmani ¹, M. Jayasekhar ¹, C. Gailce Leo Justin ², T. Thangaselvabai ¹

Affiliations
1 Krishi Vigyan Kendra, Pechiparai-629 161, IN
2 Horticultural Research Station, Pechiparai, 629 161, IN

Abstract

Disease management options currently available to farmers do not provide adequate control of plant diseases and there is a need for new disease management strategies. Induced systemic resistance (ISR) of plants against pathogens is a widespread phenomenon that has been intensively reviewed with respect to the underlying signalling pathways as well as to its potential use in plant protection. Systemic acquired resistance (SAR) is also vital plant defense system that confers broad spectrum resistance accompanied by coordinated expression of SAR genes. The present review focuses on international and indigenous research efforts in resistance induction in plants to the pathogen attack. It provides a perceptible review on the agents inducing systemic disease resistance and the mechanism underlying the induction of resistance. Recent trends in plant disease management in India cover the use of chemicals, plant extracts, cultural methods and the use of biological agents. Each and every agent possesses inherent ability to induce resistance mechanism of the host systemically. Such hidden efficacy can be potentially utilized for plant disease management.

Full Text

     

K. Manonmani ¹, N. Murugan ²

Affiliations
1 Govt. College of Technoloy, Coimbatore, IN
2 Coimbatore Institute of Technology, Coimbatore, IN

Abstract

In this paper, an attempt is made to achieve a robust weld quality that is insensitive to uncontrollable factors. The best process parameters are identified by integrating the Robust Design Concept and simulation. The influence of process parameters on Laser Beam Welding are studied The controllable parameters considered are heat flux, welding speed, focus diameter and plate thickness. The ambient temperature is taken as uncontrollable factor. Simulation of Experiments is performed for different combinations of parameter using ANSYS software based on Taguchi's Robust technique. Three dimensional non-linear transient thermal analysis is performed and the temperature distribution along the laser welded plate is obtained in the form of contour plots. Bead width and penetration depth are determined from these plots. To find the effect of control factors on the responses, ANOVA table is formed. Also, the best parameters for different responses are identified using S/N curves.

Keywords

Laser Beam Welding, Simulation, FEA, Design of Experiments, Robust Design.

Full Text