Resistência de variedades de milho crioulo ao gorgulho-do-milho Sitophilus zeamais (Coleoptera: Curculionidae)

Abstract

Corn is a cereal produced worldwide and with wide versatility of use. Maize culture suffers from insect-pest attack, and Sitophilus zeamais Motschulsky stands out as one of the main pests of stored maize grains. The cereal may express resistance of the non-preference type, antibiosis or insect tolerance. This research was developed with the objective of identifying varieties of Creole maize in relation to the response to Sitophilus zeamais by analyzing the chemical composition of the grains and biological changes of the insects. Adults of S. zeamais were exposed to grain samples of eight maize varieties: Asteca, Colorado, Palha Roxa, Oaxacan, Maisena, Caiano, Rajado and 8 Carreira for 10 days for copulation and oviposition, followed by adults of S. zeamais were removed, after 30 days, every two days the following evaluations were carried out: biological cycle and index of susceptibility by means of a mathematical formula, in addition to insect emergence, insect weight and grain weight loss. An analysis of the chemical composition was carried out to identify the concentration of proteins, carbohydrates, lipids, ashes and fibers present in the tested varieties. An analysis of S. zeamais amylase enzyme activity was performed to verify the presence of enzyme inhibitors in the maize varieties under study. The Colorado and 8 Carreira varieties were resistant to S. zeamais attack, while Palha Roxa and Maisena were the most susceptible. The results showed that Colorado presented resistance of the antibiosis type, because it provided reduced emersion of adults indicating larval death, and Oaxacan showed non-preference resistance, showing that this variety was less used by insects in relation to the other varieties under study. The chemical composition of the grains did not influence the resistance, except for the lipid content. Colorado, 8 Carreira, Rajado and Asteca showed high averages for inhibition of the enzyme, and Palha Roxa and Maisena the susceptible varieties showed low inhibition of amylase. It is suggested that the inhibitors contribute to the resistance of the varieties to S. zeamais attack. The varieties with the least emergence of insects presented higher resistance to insect attack. Colorado, 8 Carreira and Oaxacan were the most resistant varieties and Palha Roxa and Maisena the most susceptible to the attack of S. zeamais.