Comparative study of total hydroperoxides and antioxidant defense system in the Indian tropical tasar silkworm, Antheraea mylitta, in diapausing and non-diapausing generations.

In the present study, the total hydroperoxides, catalase, glutathione-s-transferase, and ascorbic acid contents were determined in different developmental stages of the non-diapause and the diapause generation of the tropical tasar silkworm, Antheraea mylitta Drury (Lepidoptera: Saturniidae). The results showed stage-specific significantly higher levels of total hydroperoxides, catalase, and ascorbic acid contents in the non-diapause as compared to the diapause generation (p < 0.05). However, a significantly enhanced level of glutathione-S-transferase activity was observed in mature 5th instar larvae of the diapause generation (p < 0.05). In the case of pupae, significantly higher levels of total hydroperoxides, catalase, and glutathione-s-transferase activity were observed in the non-diapause generation (p < 0.05). These results could be the effect of intensive metabolic transformation that takes place in tissues of the non-diapause generation and causes increased production of reactive oxygen species, such as hydroperoxides. The results suggest that antioxidants play an important role in protecting cells against reactive oxygen species.

Identification of RAPD and SCAR markers associated with yield traits in the Indian tropical tasar silkworm Antheraea mylitta drury.

The tropical tasar silkworm, Antheraea mylitta, is a semi-domesticated vanya silk-producing insect of high economic importance. To date, no molecular marker associated with cocoon and shell weights has been identified in this species. In this report, we identified a randomly amplified polymorphic DNA (RAPD) marker and examined its inheritance, and also developed a stable diagnostic sequence-characterized amplified region (SCAR) marker. Silkworms were divided into groups with high (HCSW) and low (LCSW) cocoon and shell weights, and the F(2) progeny of a cross between these two groups were obtained. DNA from these silkworms was screened by PCR using 34 random primers and the resulting RAPD fragments were used for cluster analysis and discriminant function analysis (DFA). The clustering pattern in a UPGMA-based dendogram and DFA clearly distinguished the HCSW and LCSW groups. Multiple regression analysis identified five markers associated with cocoon and shell weights. The marker OPW16(905 bp) showed the most significant association with cocoon and shell weights, and its inheritance was confirmed in F(2) progeny. Cloning and sequencing of this 905 bp fragment showed 88% identity between its 134 nucleotides and the Bmc-1/Yamato-like retroposon of A. mylitta. This marker was further converted into a diagnostic SCAR marker (SCOPW 16(826 bp)). The SCAR marker developed here may be useful in identifying the right parental stock of tasar silk-worms for high cocoon and shell weights in breeding programs designed to enhance the productivity of tasar silk.