CROP PROTECTION Inibidores de Amilase em Híbridos de Milho Como Fator de Resistência a Sitophilus zeamais (Coleoptera: Curculionidae)

ABSTRACT - Sitophilus zeamais Motschulsky is one of the major pests of stored corn and it ismainly controlled by insecticides. However, due to the undesirable consequences of chemicals on theenvironment and human health other control measures have been investigated, especially thedevelopment of resistant plants. The presence of amylase inhibitors in corn kernels may interferewith the insect digestive process. This research was developed in order to evaluate resistance of cornhybrids to the attack of S. zeamais correlated with amylase inhibitors and nutritional composition ofcorn kernels. Adults of the maize weevil were exposed to grain samples of different corn hybrids at27 ± 1°C and 75 ± 5% R.H. Biology, susceptibility index and grain consumption were evaluated. Theresults were correlated to the grain components (moisture content, ashes, lipids, proteins andcarbohydrates) and with the amylase inhibitor activity. The amylase inhibitor activity was determinedby incubating the amylase inhibitor with 0.2 units of amylase for 30 min at 25°C, and measuring theresidual amylase activity determined by the iodine method. From the nutritional parameters evaluated,only the lipid content correlated significantly with the susceptibility index (r = 0.46). The amylaseinhibitors obtained by the extraction with either ethanol or buffer were significantly and negativelycorrelated with the susceptibility index (r = -0.58), indicating that the inhibitors contribute to theresistance of corn hybrids to the attack of