Studies on various histological changes in haemocytes associated with NPV infection in Helicoverpa armugera (Hubner)
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Date
2018-10
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College of Post Graduate Studies in Agricultural Sciences, Central Agricultural University , Imphal
Abstract
Laboratory rearing of insects using synthetic diets is a better option for knowing its biology under controlled conditions. Successful rearing becomes the first priority to study its life history and nourishing behaviour using synthetic diets. Many researchers attempted to rear H. armigera under laboratory conditions using synthetic diets. While its haemocytes are very vital components of the insect immune system and are biochemically very sensitive having multiple functions such as nodule formation, phagocytosis and encapsulation as defence mechanism, synthesis and transport of nutrients and hormones for proper growth and wound healing by way of connective tissue formation. Therefore, keeping these facts in mind, in the present investigation, study was done on some of the important biological parameters of this insect by rearing on the semi-synthetic diets based on four locally available pulses viz.,chickpea, green gram, pea and black gram and comparing with chickpea leaves used as control. The larvae obtained from the culture were used to study the changes in their Total Haemocyte Count (THC) and Differential Haemocytes Count (DHC) when they were NPV infected with 0.2 ml of 2x105 occlusion bodies (OB) ml-1 at various stages at 5, 8 and 10 days old. Results revealed that the fitness index on chickpea (1.48) showed the highest followed by pea (1.23) and the lowest on control (0.80) and proved that chickpea based semi-synthetic diet was the best for mass rearing of H. armigerawhile pea-based diet could also be used as substitute. DHC showed six identified cells-prohaemocyte, plasmatocytes, granulocytes, spherulocytes, adepohaemocytes and oenocytoids and another four unidentified cells. Among the identified cells oenocytoids did not show any involvement in defence mechanism. THC showed that the effect of NPV infection was more in younger larvae.