The whitefly, Bemisia tabaci (Aleyrodidae, Hemiptera), regarded as a species complex comprising over 34 genetic groups, is a serious insect pest of several crops. The aim of this study was to find out the difference in alkaline phosphatase (ALP) activity between developmental stages of two populations of B. tabaci belonging to Asia II-1 and Asia I genetic groups. There was a rise in ALP activity from first to second instar followed by gradual decline through third and fourth instars. ALP activity reached its peak during the adult stages of both Asia I and Asia II-1 populations. The specific activity of ALP in nymphal instars of Asia II-1 was significantly higher than that of Asia I.
The kinetics of ALP revealed that Asia I population showed significant increase in Vmax value compared to Asia II-1 in the second instar, fourth instar and adult stages, whereas the opposite is seen in the first and third instars. Also, the Asia I population showed significant decrease in Km value compared to Asia II-1 in the first and fourth instars; the opposite was seen in second instar. No significant differences were observed between the Km values of the third instar and adult stages of both the populations. The possible physiological role of ALP and its implications in management of this pest are also discussed in this communication.