SENSITIVITY OF IMPROVED BREEDS AND HYBRIDS OF MULBERRY SILKWORM TO BmNPV AND MANAGEMENT PRACTICES
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Date
2007-06-06
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UNIVERSITY OF AGRICULTURAL SCIENCES GKVK, BANGALORE
Abstract
Sensitivity of four improved breed s (CSR2, CSRt, MH\, BL43) and five hybrids of mulberry
silkworm (CSR2 x CSRt, CSR4 x CSR2, MH) x CSR2, BL43 X CSR2 and PM x CSR2) with two
concentration (10-3 and 10-6 PIBs) ofBmNPV were tested under laboratory condi tion s.
The ET50 for symptom ex pression and ET50 for mortality were min imum in CSR2 when
inoculated with BmNPV, while the same were maximum in PM x CSR2. The ERR was
significantly maximum in PM x CSR2 and it was minimum in CSR2 when treated with BmNPV.
The cocoon traits (cocoon, pupal and shell weights) except shell ratio were found to be nonsignificant
in improved breeds and hybrids of silkworm when inoculated with BmNPV. Among the
improved breeds and hybrids of silkworm, the cocoon filament length and cocoon fila ment weight
were significantly maximum in CSR2. The cocoon filament length and cocoon f lament weig ht were
significantly minimum in MH) x CSR2•
Among the concentrations of PIBs, ET50 for symptom expression was less but ETso for
larval mortality was minimum at 10-3 PIBs Iml with reduced econonuc parameters. The
consumption, digestion an.d consumption indices were significantly minimum among .BmNPV
inoculated batches compared to non-inoculated ones, irrespective of breedsl hybrids and PIBs
concentration both ~uring fourth and fifth instars.
The total "protein, total carbohydrate and free amino acid contents of haemolymph, the
digestive amylase activity, gut and haemolymph pH were greatly altered in BmNPV infected worms
compared to untreated worms.
The silkworms (CSR2 x CSRt) reared on mulberry leaves dipped in aqueous leaf extracts of
Psoralea 'cory leifolia L. @ 800 ppm was found effective in reducing the larval mortality due to
BmNPV (10-3 PIBs) infection besides enhancing the economic traits of silkworm.
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