Molecular characterization of Beauveria bassiana (Balsamo) vuillemin and its bioefficacy against Tetranychus urticae Koch (Acari: Tetranychidae)
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Date
2011
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CCSHAU
Abstract
Investigations were carried out to assess the pathogenicity of Beauveria bassiana against Tetranychus
urticae on okra. Molecular characterization of six strains of B. bassiana was done by RAPD- PCR to know the
genetic similarity among them. The yield of genomic DNA of B. bassiana was higher in Lysis Buffer method
(2.10 to 10.50μg/ ml) as compared to CTAB method (2.34 to 7.10μg/ ml). Absorbance ratio of all strains varied
from 1.60 to 2.20. Eleven random primers generated 19 (82.16%) polymorphic and 4 (17.39%) monomorphic
bands. The size of PCR amplified products ranged from 500 to 4000 bp. The genetic similarity of the strains varied
from 50 to 70 percent. Under in vitro 42 to 94 and 34.1 to 66.25 percent mortality of T. urticae was recorded in
Direct Spray and Treated Food Bioassay, respectively with 1 × 105 to 1 × 1012 conidia ml-1 conecntrations of B.
bassiana. LC50 values of B. bassiana were in the range of 3 × 105 to 2.6 × 1011 conidia ml-1 and LT50 values varied
from 52.12 to 141.53 h for eggs, larvae, nymphs and adults in both the bioassay methods. Direct Spray Bioassay
was more effective as compared to Treated Food Bioassay. Under field conditions, the percent reduction in T.
urticae was from 51.03 to 65.18 percent with all the strains. Hb- Hyderabad (65.18%), was the most potent in
reducing the mite population followed by ITCC- 4668 (62.36%), ITCC- 5408 (58.55%), ITCC- 6063 (54.61%),
ITCC- 5549 (52.48%) and ITCC- 4513 (51.03%). There was no effect of B. bassiana spray S. punctillum
population as their numbers in B. bassiana (strain Hb- Hyderabad) treatments (1.43 beetles/ leaf) and control (1.17
beetles/ leaf) were statistically comparable. Higher yield of okra fruits was recorded in B. bassiana treated plots
(581.43 g/ plot) as compared to untreated plots (577.66 g/ plot). The Chlorophyll content was also higher in B.
bassiana treated leaves (0.289 to 0.492 μg/ ml) as compared to untreated plots (0.166 μg/ ml).
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