Pyramiding of <i>cry</i> genes in high-dose transgenic eucalyptus provides control of <i>Thyrinteina arnobia</i> (Lepidoptera: Geometridae) and reduces the risk of resistance

In Brazilian eucalyptus farms, the brown looper caterpillar (<i>Thyrinteina arnobia</i>) causes severe defoliation and up to 40% reduction in biomass production. In controlling <i>T. arnobia</i>, transgenic eucalyptus event 1521K059 was developed to produce the Cry1Ab, Cry1Bb, and Cry2Aa pesticidal proteins from the bacterium <i>Bacillus thuringiensis</i>. We performed bioassays with leaf material from eucalyptus events and the purified individual pesticidal proteins to establish susceptibility in <i>T. arnobia</i> larvae, and competition binding assays with the three Cry proteins and midgut brush border membrane vesicles of <i>T. arnobia</i>. The results from bioassays support high toxicity against <i>T. arnobia</i> for all three Cry proteins and that eucalyptus event 1521K059 is a high-dose event for <i>T. arnobia</i>. Lack of competition between the three Cry proteins supports that event 1521K059 is a pyramided trait. These observations support the high activity of eucalyptus event 1521K059 against <i>T. arnobia</i> larvae and a low risk of resistance evolution.