|Legaspi, Jesusa - Susie|
|Legaspi, j., Benjamin|
Submitted to: Journal of Economic Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/15/2001
Publication Date: 4/1/2002
Citation: Setamou, M., Bernal, J., Legaspi, J.C., Mirkov, T.E., Legaspi, J., B.C. 2002. Evaluation of lectin-expressing transgenic sugarcane against stalkborers (Lepidoptera: Pyralidae): effects on life history parameters and damage. Journal of Economic Entomology. 95(2):469-477. Interpretive Summary: The Mexican rice borer, Eourema loftini, is an important insect pest in sugarcane causing economic losses estimated at US$10-20 million annually. A secondary insect pest is the sugarcane borer, Diatraea saccharalis. To mitigate the losses due to these insects, we studied the effects of use of a genetically-engineered (or transgenic) sugarcane crop in reducing damage by the Mexican rice borer and sugarcane borer. An insecticidal gene called GNA (Galanthus nivalis agglutinin) from the snowdrop lily was transferred to sugarcane. This gene is known to have resistance to insect damage in plants. The genetically-engineered sugarcane leaves and tissues were incorporated in an artificial diet made up mostly of ground corn cob, wheat, agar and other ingredients and then fed to Mexican rice borer and sugarcane borer larvae in the laboratory. In the greenhouse, the two insect species were fed the genetically-engineered sugarcane plants. Laboratory results indicated that the transgenic sugarcane diet reduced the survival egg production and adult emergence of the Mexican rice borer but did not affect the sugarcane borer. However, female longevity was reduced in both insect species when fed transgenic diet compared to non-transgenic diet. In the greenhouse, we found that development and reproduction of the Mexican rice borer was negatively affected when fed transgenic sugarcane plants compared to non-transgenic plants but the sugarcane borers were not affected.
Technical Abstract: The impacts of snowdrop lectin (Galanthus nivalis agglutinin, GNA) expressed in transgenic sugarcane on life history parameters & damage of Mexican rice borer [Eoreuma loftini (Dyar)] & sugarcane borer [Diatraea saccharalis (F.)] (both Lepidoptera: Pyralidae) was evaluated. In the lab, lyophilized sugarcane leaf sheath tissue was incorporated in a meridic diet tresulting in a GNA concentration of 0.47% of total protein & used for bioassays over two successive generations. Feeding damage & larval weights of both borers were evaluated on transgenic & non-transgenic sugarcane stalk cuttings in the greenhouse. Deleterious effects of GNA were not observed on survival, weight & developmental periods of larvae & pupae, nor on adult fecundity & egg viability of D. saccharalis. In the first generation, addition of transgenic sugarcane tissue to the diet enhanced larval growth in D. saccharalis resulting in higher larval & pupal weight compared to diet with nontransgenic sugarcane. This effect was not observe in the second generation. In contrast, larval survival, percent adult emergence & female fecundity of E. loftini were significantly reduced when fed transgenic diet compared to non-transgenic diet. A substantial reduction of female pupal weight of E. loftini was observed in the second generation. For both species the only consistent effect of GNA in both generations was reduction in adult female longevity. In the greenhouse significant differences were not found in larval weights & feeding damage between transgenic & non-transgenic sugarcane for both species. Life table parameters showed that GNA at the level found in the transgenic diet did not affect development & reproduction of D. saccharalis. It did negatively affect development & reproduction of E. loftini.