@article{Mesén-Porras_Dahdouh-Cabia_Jiménez-Quirós_Mora-Castro_Rodríguez_Pinto-Tomás_2020, title={Soybean protease inhibitors increase Bacillus thuringiensis subs. israelensis toxicity against Hypothenemus hampei}, volume={31}, url={https://revistas.ucr.ac.cr/index.php/agromeso/article/view/36573}, DOI={10.15517/am.v31i2.36573}, abstractNote={<p><span class="CharOverride-2"><strong>Introduction.</strong> </span>The coffee berry borer (<span class="CharOverride-6">Hypothenemus hampei</span> Ferrari, CBB) is one of the most devastating pests on coffee plantations around the world. Although CBB is susceptible to the effect of δ–endotoxins of <span class="CharOverride-6">Bacillus thuringiensis </span>subs. israelensis (Bti) at laboratory level, the efficacy of this control method is poor in the field, presumably due to the inactivation by digestive proteases different to those required for protoxin activation. <strong><span class="CharOverride-2">Objective. </span></strong>To study whether the addition of a soybean flour extract enriched with protease inhibitors (PI), mixed with Bti crystals and spores (Bti-sc) in an artificial diet, could improve the toxicity of Bti against CBB. <strong><span class="CharOverride-2">Materials and methods.</span></strong> This study was performed in San José, Costa Rica, between 2012 and 2013. A set of adult female CBB insects was exposed to a mixture containing different concentrations of a partially purified soybean meal extract with active PI and lyophilized Bti-sc, and were tested through a bioassay in artificial diet to estimate the sub-lethal concentration (LC<span class="CharOverride-7">50</span>). The mortality results were validated by observing the dissected midgut, whose ultrastructure was analyzed by transmission electron microscopy. <strong><span class="CharOverride-2">Results. </span></strong>The soybean extracts partially degraded the Bti-sc complex, it reduced its LC<span class="CharOverride-7">50</span> by almost four times (from 1.135 to 0.315 µg µl<span class="CharOverride-4">-1</span>) and enhanced CBB mortality in a concentration-dependent manner. Histological analyses of the midgut confirmed this synergistic effect, since severe epithelial damage to the intestinal epithelium of CBB exposed to Bti-sc + PI was visualized compared to Bti-sc alone. <strong><span class="CharOverride-2">Conclusions. </span></strong>The combination of a soybean extract enriched in PI and Bti-sc enhanced the mortality effect over CBB, which was confirmed by the midgut collapse. Soybean flour is a cost-effective supplement that could increase Bti effectiveness against CBB and delay the appearance of biological resistance.</p>}, number={2}, journal={Agronomía Mesoamericana}, author={Mesén-Porras, Esteve A. and Dahdouh-Cabia, Sergio and Jiménez-Quirós, Catherine and Mora-Castro, Rebeca and Rodríguez, César and Pinto-Tomás, Adrián A.}, year={2020}, month={May}, pages={461–478} }