Laboratory evaluation of transgenic Bt cotton against helicoverpa armigera (Hubner) and spodoptera litura (Fabricius)
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Date
2007
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CCSHAU
Abstract
Studies on the “Laboratory evaluation of transgenic Bt cotton against
Helicoverpa armigera (Hubner) and Spodoptera litura (Fabricius)” were carried out in the
laboratory and at Research Farm, Department of Entomology Chaudhary Charan Singh
Haryana Agricultural University, Hisar, during kharif 2006. Eleven genotypes including five Bt
(Ankur 2534 Bt, Ankur 651 Bt, RCH 134 Bt, RCH 317 Bt and MRC 6304 Bt) and their
corresponding non-Bt hybrids with one local hybrid HHH-223 were taken for the study and
they were grown by adopting recommended package of practices. The survival of first instar
larvae of H. armigera was observed on top leaves, middle leaves, squares and bolls for five
days at an interval of 60, 90, 100, 120 and 140 days of crop age. Significant adverse effect of
Bt was observed at 60, 90 and 100 days of crop age in top leaves, middle leaves, squares and
bolls. The maximum per cent reduction in survival of larvae was observed at 60 days of crop
age in top leaves (16.67-76.67 %), middle leaves (13.33-86.67 %), squares (26.67-86.67 %) xivand
bolls (30.00-86.67 %). Similar trend followed at 90 and 100 days of crop age. No
significant effect of Bt at 120 and 140 days of crop age was observed in comparison to non-Bt.
The various biological parameters (larval period, larval weight, larval survival, pupal period,
pupal weight and adult emergence) of H. armigera larvae from third instar onwards were
studied on top leaves, middle leaves, squares and bolls at an interval of 65, 95, 105, 125 and
145 days of crop age. Significant adverse effect of Bt was observed at 65, 95 and 105 days of
crop age in top leaves, middle leaves, squares and bolls. At 125 and 145 days of crop age no
significant effects of Bt were observed. The various biological parameters of S. litura larvae
from first instar onwards were studied on top leaves and middle leaves at an interval of 80, 120
and 140 days of crop age. No significant difference between Bt and non-Bt hybrids were
observed. Fourth instar larvae of H. armigera were used to study various
consumption-utilization indices at an interval of 70, 100 and 130 days of crop age in top
leaves, middle leaves, squares and bolls. There was significant reduction in CI, GR, ECI,
AD/AE and ECD in Bt genotypes at 70 and 100 days of crop age for H. armigera. At 130 days
of crop age no significant effect of Bt was observed. Similarly fourth instar larvae of S. litura
were used to study various consumption-utilization indices at an interval of 75, 105 and 135
days of crop age in top leaves and middle leaves. There was no significant reduction in CI, GR,
ECI, AD/AE and ECD in Bt genotypes at 75, 105 and 135 days of crop age for S. litura. Twigs
of different genotypes bearing leaves, flowers, squares and bolls were brought to the laboratory
at 80 days of crop age to observe the ovipositional preference of H. armigera between Bt and
non-Bt genotypes in a choice test conditions. No significant variation was found between Bt
and non-Bt genotypes for oviposition studies. The total number of eggs laid on Bt and non-Bt
hybrids ranged from 344 to 361 eggs/2 twigs/4 females.