EFFECTS OF LECTINS, CRY1A CRY1B BT DELTA-ENDOTOXIN, PAPA, PROTEASE AND ALPHA-AMYLASE INHIBITORS, ON THE DEVELOPMENT OF THE RICE WEEVIL, SITOPHILUS-ORYZAE, USING AN ARTIFICIAL SEED BIOASSAY/

An artificial maize seed bioassay was developed to evaluate potential resistance factors against the rice weevil, Sitophilus oryzae. Weevils reared in artificial seeds compared to those reared in whole maize se eds: (i) developed faster, (ii) had similar within-seed developmental mortalities, (iii) were lighter in weight upon emergence and (iv) ovip osited the same number of eggs. Using this bioassay we found that E-64 , a cysteine protease inhibitor, decreased the number of emerged adult s per seed and delayed within-seed developmental time, suggesting that the rice weevil utilizes a cysteine protease to digest its dietary pr otein. Weevils fed inhibitors of trypsin and chymotrypsin, Bowman-Birk and Kunitz inhibitors respectively, developed normally. Para-amino-L- phenylalanine (PAPA), a non-protein amino acid implicated as an insect resistance factor in Vigna vexillata, was lethal at dietary levels of 0.2% (w/w) and higher. An extract from Amaranthus caudatus seeds dela yed the developmental time of the rice weevil at dietary levels of 0.2 % (w/w) and increased mortality at dietary levels of 1.0% (w/w). Sever al proteins tested, including Griffonia simplicifolia agglutinin II, p hytohemagglutinin extract containing common bean a-amylase inhibitor, pokeweed agglutinin, Bacillus thuringiensis CRY1A/CRY1B endotoxin, and an alpha-amylase inhibitor from wheat, had no effect on the rice weev il. The artificial maize seed bioassay was adapted by pelleting the se ed for use with an ultrasonic insect feeding monitor to determine the finding activity of rice weevils as they developed from egg hatch to p upation.