Abstract

ROMERO, Laura; AREVALO, Helber; DUARTE, William  and  MEJIA, Rodolfo. SUSCEPTIBILITY OF Heliothis virescens (LEPIDOPTERA: NOCTUIDAE) TO Cry1Ac PROTEIN INCORPORATED TO MERIDIC DIETS. rev.udcaactual.divulg.cient. [online]. 2012, vol.15, n.2, pp.381-389. ISSN 0123-4226.

As an alternative for pest management, plants were developed to express lethal proteins against target insects, which may develop resistance due to their constant exposure to these proteins. To monitor changes in susceptibility to Cry1Ac protein and determine the effect exerted by the diet composition on the susceptibility of Heliothis virescens, bioassays were carried out in the U.D.C.A's laboratory of Agricultural Biotechnology with populations collected on Desmodium sp., at Espinal, Tolima. The diets employed were ICRISAT, Greene and Shorey & Hale, incorporating serial concentrations of Cry1Ac, ranging from 0.01 to 100 ppm. Bioassays consisted of six treatments and six replicates; each experimental unit was represented by a plastic cup with diet, in which one or five neonate larvae were placed. With the mortality assessed at day seven the lethal concentration (LC₅₀) was calculated. The diet composition influenced the susceptibility response. The LC₅₀ obtained for Heliothis in 2011 (0.956 ppm) indicates that this insect lost susceptibility to Cry1Ac expressed by Bollgard®; however, this plant variety still has control over the species. Results also showed that the mortality obtained with five larvae per experimental unit was influenced by cannibalism and not by the consumption of Cry1Ac, indicating that only one larva per container should be used to eliminate the effect of cannibalism on mortality.

Keywords : Tobacco budworm; Bacillus thuringiensis; tolerance; bioassays.

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