ISOLATION AND CHARACTERIZATION OF ENTOMOPATHOGENIC ...

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the metabolic activity (Paris and Ferron, 1971). UV rays that causes alkylation and has been found effective in mutagenesing fungi has been employed in this study. Randomly picked colonies of V. lecanii and M. anisopliae that came up on SMAY agar on plating the mutant bank were picked up and analysed for their insecticidal activity. Four UV mutants of V. lecanii (VA2, VA5, VA11 and VA12) were found to be more toxic to aphids B. brassicae. The mutants of M. anisopliae Ma2 including MH2, MH4, MH8 and MH12 showed higher pathogencity to H. armigera. The highest mortality was observed in case of VA2 (91.97%) and MH4 (91.67%) on B. brassicae and H. armigera respectively. The mutants VA2 and MH4 showed 11.3 per cent and 23.94 per cent higher mortality over the wild type respectively. The results obtained indicate the potential of chemical and UV mutagenesis in improving the toxicity of entomopathogens. Mutants of M. anisopliae and Paelomyces farinosus have been generated earlier which were significantly more virulent. It is possible that more vigorous mutagenesis and wider screening will enable identification of more potent strains. Evaluation of potency of V. lecanii Vl1 against selected crop pests The effect of V. lecanii Vl1 was initially tested on B. brassicae and A. disperses in laboratory using different dosages of conidia. The per cent mortality was observed after different days of inoculation. The per cent mortality (92.3%) progressively increased upto 10 days after inoculation. At 10 days, the maximum mortality of B. brassicae was observed when 1.2 x 10 9 conidia/ml was used. The per cent mortality (80.95%) of A. disperses during the same period was also the highest when 1.2 x 10 9 conidia/ml inoculum was used. However, in an earlier study (Masuda and Kikachi, 1992), it was found that higher concentration (10 7 to 10 8 conidia/ml) was enough to cause 96-100 per cent mortality on A. gossypii by V. lecanii. The results indicate variability of pathogencity of V. lecanii on the two insect tested. V. lecanii was found to be more toxic to B. brassicae than A. disperses. The effect of V. lecanii has been reported earlier on Trialeurodes vaporariorum and B. tabaci which reported a per cent mortality of 91 and 100 using a inoculum of 3.2 x 10 6 . The effectiveness of the fungus, V. lecanii has been proved against Myzus persicae (Khalil et al., 1990; Milner and Lutton, 1986). Having known the potential of V. lecanii to be toxic to B. brassiae, A. disperses in laboratory condition, a field experiment was laid out in order to assess the performance of the entomopathogen on B. brassicae and Apis crassivora. The mortality in the field was however, lower when the same dosage was used 10 days after inoculation. Among the three isolates, Vl1 application showed higher rate of mortality (61.16%) of B. brassicae followed by Vl3 (50.17%). Overall, the efficacy of fungus was more effective at higher concentration and high exposure period than lower concentration and low exposure period. The reduction in toxicity in the field could be due to several reasons including the harmful effects of UV rays on the fungal pathogen itself (Ignoffo et al., 1976), less accessibility of the pathogen to the insect pest and dispersal of the conidia due to wind. Hence, sprays with higher initial population and additional sprays are required to augment the biocontrol potential in field. The lower effectiveness could be also due to the low humidity prevented during the period of experiment. All the five dosages of V. lecanii proved their supremacy to uninoculated treatments. Comparatively, the highest dosage (2 x 10 12 conidia/ha) caused 61.6 per cent mortality of B. brassicae after second spray which was lesser than the mortality caused by the recommended spray of dimethoate 30 EC (@ 1.7 ml/l) which resulted in 87.53 per cent. However, the results indicated that the fungus Vl1 at higher dosage (2 x 10 12 conidia/ha) did not lag much. All the dosages of V. lecanii isolates against A. crassivora proved their superiority over untreated treatment. Among the three isolates, Vl3, caused highest mortality of 66.50 per cent after second spray of higher dosage (2 x 10 12 conidia/ha). Dimethoate maintained their supremacy over the mycopathogen throughout the experimental period recording significantly
higher mortality of aphids. The commercial formulation Vertalec was found to control whitefly and aphid effectively at 10-13 h at ≥97 per cent relative humidity in Japan (Hall, 1982). The lower mortality of fungus than chemicals may be due to the fact that chemical insecticides were quick in action and hence reduced the whitefly population considerably. The entomopathogen which acted slowly on the pest allowed them to live on the plant, until the incubation period of the disease was completed (Miranpuri and Khachatourians, 1995). FUTURE LINE <strong>OF</strong> WORK 1. Extensive exploration of diverse areas and environmental niches need to be done. 2. Mutagenesis of the isolates need to be done on more vigorous note and larger screening need to be done. 3. Refinement of formulation and development of application technology to enhance the effectiveness of the fungus under field conditions. 4. Genetic/molecular diversity of the isolate need to be done in order to develop an inoculum consortia containing diverse strains. 5. The molecular basis of toxicity needs to analyse to attempt further exploitation of these mycopathogens.
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ISOLATION AND CHARACTERIZATION OF E
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Chapter No. I INTRODUCTION C O N T
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Contd….. Table No. Title 14. Spor
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Contd….. Table No. Title 39. Per
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Plate No. LIST OF PLATES Title 1. M
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I.INTRODUCTION The increased use of
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II. REVIEW OF LITERATURE The variou
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The entomopathogenic fungi so far i
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Table 1. Contd….. Sl. No. Insect
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Milner et al. (2002) studied the ef
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25°C for sporulation and biomass p
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Pathogencity of various strains/iso
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Gopalkrishnan and Mohan (2000) test
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necessary serial dilutions under ph
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Sl. No. Table 2. Details of differe
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3.9 EVALUATION OF DIFFERENT FORMULA
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Fig. 1. Mycopathogens of insect pes
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Table 5. Contd….. Month/s visited
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Table 5. Contd….. Month/s visited
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Table 5. Contd….. Mycosis noticed
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Totally eight isolates of N. rileyi
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Metarhizium anisopliae Vertucillium
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Ma 1 (Dharwad) Ma2 (Dharwad) Ma 3 (
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Table 8. Mortality caused by the is
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Helicoverpa armigera Dimond Black M
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Plate 5. The moratality of Hlelicov
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Table 11. Total biomass production
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Table 12. Total biomass production
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Table 14. Sporulation of Metarhiziu
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Mean spore yield x 10 8 /g 25 20 15
Page 61 and 62: Among the non-grain substrates, the
Page 63 and 64: Mean spore yield x 10 4 /g 35 30 25
Page 65 and 66: Sl. No. Table 19. Effect of fungici
Page 67 and 68: Per cent inhibition 100 90 80 70 60
Page 69 and 70: Sl. No. Table 21. Effect of insecti
Page 71 and 72: Out of nine insecticides, endosulfa
Page 73 and 74: Sl. No. Table 23. Effect of weedici
Page 75 and 76: Days after storage Table 25. Persis
Page 77 and 78: Table 26. Survival of Metarhizium a
Page 79 and 80: Table 28. Survival of Metarhizium a
Page 81 and 82: Sl. No. Table 29. Survival of Metar
Page 83 and 84: Sl. No. Table 30. Survival of Metar
Page 85 and 86: Per cent germination 90 80 70 60 50
Page 87 and 88: Sl. No. Table 33. Survival of Verti
Page 93 and 94: 4.9 PATHOGENICITY OF Verticillium l
Page 95 and 96: Sl. No. Table 39. Per cent mortalit
Page 97 and 98: Culture grown on rice grains Harves
Page 99 and 100: Tr. No. Table 41. Per cent reductio
Page 101 and 102: Tr. No. Table 43. Per cent reductio
Page 103 and 104: The fungal spray at higher dosage (
Page 105 and 106: Table 46. Effect of wild types and
Page 107 and 108: The hyphal and conidial characters
Page 109 and 110: In an earlier experiment, bagasse w
Page 111: M. anisopliae exhibited rapid reduc
Page 115 and 116: 14. Oil formulations proved better
Page 117 and 118: CHARNLEY, A.K. AND ST. LEGER, R.J.,
Page 119 and 120: IGNOFFO, C.M., MARSTON, N.L., HOSTE
Page 121 and 122: MULLER, E.J., 2000, Control of the
Page 123 and 124: ST LEGER, R.J., BUTT, T.M., STAPLES
Page 125 and 126: APPENDIX I Mean monthly weather dat
Page 127 and 128: Maharashtra Association for the Cul
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