Abstract: Among silkworm diseases, viral diseases are the major and most common which damages the cocoon production. Viral flacherie is caused by BmIFV, BmDNV1 and BmDNV2. Resistant and susceptible silkworm breeds against BmDNV1 were identified among the Indian Germ plasm stock. The changes in major organic constituents viz., total protein, carbohydrate and lipid content during the progressive infection of BmDNV1 in susceptible and resistant breeds were estimated as per the standard methods. As the larval age increases, there was a consistent increase in the level of organic constituents viz., protein and carbohydrates in both control and treated batches, but the level of increase in treated batches were markedly less when compared to the respective control batches. After inoculation with BmDNV1, there was a significant decrease in total protein content in haemolymph and mid gut tissue in susceptible breeds when compared with control batches. In resistant breeds, there was a significant decrease in total protein content up to 4 day post inoculation (PI) but subsequently, the decrease was less compared to the respective controls. There was a slight decrease in total carbohydrate content in haemolymph and mid gut tissue in susceptible and resistant breeds. In case of lipid content, there was a significant increase in haemolymph and mid gut tissues in susceptible breeds and in resistant breeds the changes were not found significant. In susceptible silkworm breeds, the biochemical changes clearly indicated that the BmDNV1 infection depletes the major organic constituents viz., total protein and total carbohydrate contents which are the major sources energy. This depletion in these contents resulted in stunted growth in infected silkworms.

Key words: Silkworm, Bombyx mori, BmDNV1, total protein, total carbohydrate, total lipid, resistant breeds, susceptible breeds