EFFECT OF ENTOMOPATHOGENIC FUNGI BEAUVERIA BASSIANA ON THE CELLULAR IMMUNITY AND BIOCHEMISTRY OF GREEN BUG NEZARA VIRIDULA L.

Abstract

Entomopathogenic fungi (EPF) are considered effective methods for investigating insects’ immunity in response to infection. Insects have a variety of defense mechanisms against infectious diseases, namely phenoloxidase, hemocytes, detoxification and antioxidant enzymes.The instinctive immune system of insects is highly advanced and depends on humoral and cellular elements. In this study, five haemocytes types were found in fifth nymphal instar and adults of green bug, Nezara viridula (Heteroptera: Pentatomidae) namely; prohaemocyte (pr),granulocyte (gr), spherulocyte (sp), plasmatocyte (pl), coagulate cells (co) and oenocytoid (oe). Infection with Beauveria bassiana significantly decreased the different haemocytes count in both fifth nymphal instar and adults, especially after 72h post-infection. The haemocytes’ response against fungi was also investigated. A significant increase in Alpha esterase (EST), Acid phosphatise (ACP) and Alkaline phosphatise (ALP) were observed after 72h post infection in the haemolymph of N. viridula adults. In contrast, phenoloxidase activity significantly decreased in adults’ hemolymph after the same period of infection. Results indicated that infection with B. bassania affects the number of circulating haemocytes and decreases phenoloxidase activity.