Crops genetically engineered to produce Bacillus thuringiensis toxins for insect control can reduce use of conventional insecticides, but insect resistance could limit the success of this technology. The first generation of transgenic cotton with B. thuringiensis produces a single toxin, Cry1Ac, that is highly effective against susceptible larvae of pink bollworm (Pectinophora gossypiella), a major cotton pest. To counter potential problems with resistance, second-generation transgenic cotton that produces B. thuringiensis toxin Cry2Ab alone or in combination with Cry1Ac has been developed. In greenhouse bioassays, a pink bollworm strain selected in the laboratory for resistance to Cry1Ac survived equally well on transgenic cotton with Cry1Ac and on cotton without Cry1Ac. In contrast, Cry1Ac-resistant pink bollworm had little or no survival on secondgeneration transgenic cotton with Cry2Ab alone or with Cry1Ac plus Cry2Ab. Artificial diet bioassays showed that resistance to Cry1Ac did not confer strong cross-resistance to Cry2Aa. Strains with >90% larval survival on diet with 10 g of Cry1Ac per ml showed 0% survival on diet with 3.2 or 10 g of Cry2Aa per ml. However, the average survival of larvae fed a diet with 1 g of Cry2Aa per ml was higher for Cry1Ac-resistant strains (2 to 10%) than for susceptible strains (0%). If plants with Cry1Ac plus Cry2Ab are deployed while genes that confer resistance to each of these toxins are rare, and if the inheritance of resistance to both toxins is recessive, the efficacy of transgenic cotton might be greatly extended.

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Steroidal glycoalkaloids are naturally occurring compounds present in solanaceous plants including potatoes. They are reported to be toxic to animals and humans. The recognition of their potential toxicity has led to implementation of guidelines limiting glycoalkaloid content. The effectiveness of these guidelines is dependent upon reliable analytical methods for their analysis. The objective of this study was to develop a simple, rapid, and inexpensive immunoassay for potato glycoalkaloids that correlates with HPLC. This was successfully demonstrated with various potato samples, including eight fresh potato varieties; potato flesh, peel, sprouts, and leaves; and processed products such as French fries, chips, and skins. Storage of the ELISA kit in a refrigerator for >3 months did not affect its effectiveness. The use of a stable, accurate, and highly sensitive ELISA kit should facilitate (a) development of standard protocols for handling and sampling of potatoes to minimize pre-and postharvest glycoalkaloid formation; (b) analysis of foliar glycoalkaloids, thus saving plant breeders considerable time, effort, and cost; (c) marketing potatoes at lower cost; (d) measurement of the metabolism and distribution of glycoalkaloids in animals and humans; and (e) assurance to the consumer of eating a good quality potato.

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