Arthropods, 2013, 2(3): 126-136 IAEES www.iaees.org Article Biochemical properties of digestive carbohydrases from the sugar beet weevil, Lixus incanescens (Coleoptera: Curculionidae) Seyed Mohammad Ahsaei, Vahid Hosseininaveh, Mahdieh Bigham Department of Plant Protection, College of Agriculture, University of Tehran, Karaj 31587-77871, Iran E-mail: ahsaei_mohammad@ut.ac.ir,vnaveh@ut.ac.ir Received 22 April 2013; Accepted 25 May 2013; Published online 1 September 2013 Abstract The sugar beet weevil, Lixus incanescens B., is one of the most important pests of sugar beet plant in Iran. The petioles and leaves of sugar beet are attacked by larvae and adults of the sugar beet weevil. Chemical application is currently used for controlling the pest. Digestion in the alimentary canal of the sugar beet weevil is facilitated by some carbohydrases. Results of the in vitro studies indicated the presence of α-amylase, β- glucosidase and β-galactosidase in the digestive tract of the pest. Highest activities of α-amylase, β-glucosidase and β-galactosidase were at pH 5, pH 5 and pH 4, respectively. No significant α-glucosidase and α- galactosidase activity was detected in the pest’s digestive system. Optimum temperatures for α-amylase, β- glucosidase and β-galactosidase activity were determined at 45, 50 and 40 °C, respectively. α-amylase was more stable under acidic condition (pH 4 to pH 6) than under highly acidic and alkaline condition. Na + and K + increased α-amylase activity, but sodium dodecyl sulfate significantly decreased amylase activity. Also, the activity of α-amylase was inhibited by the other compounds such as MgCl 2 , CaCl 2 and EDTA. Zymogram analysis using native-PAGE revealed one band of α-amylase activity in Lixus incanescens. High activity of carbohydrases in the digestive system of adults was determined and further researches are needed to be applied to design new strategies for controlling the sugar beet weevil based on natural carbohydrase inhibitors. Keywords α-amylases; sugar beet weevil; carbohydrases; Lixus incanescens. 1 Introduction The sugar beet weevil, Lixus incanescens B. (Coleoptera: Curculionidae) is a key pest of sugar beet plants causing significant damage to living plants in Iran. It has been reported from many parts of Iran and some other countries (Davatchi et al., 1960; Aleeva, 1953). The sugar beet weevil has three generations per year. The petioles and leaves of sugar beet plants are attacked by larvae and adults of L. incanescens. The larvae can cause up to 75% root weight loss (Ocete et al., 1994). The most damage happens in the second and third generations. Loss in early-planted sugar beet is less than late-planted ones (Parvizi et al., 1988). Currently, Arthropods ISSN 22244255 URL: http://www.iaees.org/publications/journals/arthropods/onlineversion.asp RSS: http://www.iaees.org/publications/journals/arthropods/rss.xml Email: arthropods@iaees.org EditorinChief: WenJun Zhang Publisher: International Academy of Ecology and Environmental Sciences