Abstract

                                The immune system in insects involves in clearing the haemolymph of foreign pathogens by haemocytes and humoral factor. They can accomplish this in a couple of different ways. One is a cellular mediated response by physically clearing the haemolymph by phagocytosis, nodulation and encapsulation and the other is by humoral secretion of proteins. Pathogenic infection in silkworm, Bombyx mori L. is common and there is a possibility of differential response by haemocytes in different breeds to microbial infection. Hence, the differential response in the form of difference in Total haemocyte count (THC) and Differential haemocyte count (DHC) in susceptible and tolerant breeds were investigated under normal and Beauveria bassiana invasion conditions. Under normal condition, there was a gradual increase in THC as the age of the silkworm increases and high THC was recorded in Nistari, PM and NB4D2 (tolerant breeds) compared to susceptible breeds (NB7, NB18 and KA). There was a gradual increase in THC, gradual decrease in prohaemocyte and oenocyte counts and increase in plasmatocyte and granulocyte counts during the progressive infection by Beauveria bassiana.

Key words : Bombyx mori L, Silkworm breeds, Beauveria bassiana, Total haemocyte count, Differential haemocyte count