Production of Cry1Ac protein in transgenic cotton and control of lepidoperan larvae

Abstract

The Cry1Ac protein expressed by the Bollgard^® cotton must confer to the plant a season long resistance against lepidopteran pest under a range of cropping conditions. This study was conducted during two seeding seasons, in the beginning of the high and the low rainfall season in the Northeast of Brazil, to investigate Cry1Ac production by different parts of the plant Bollgard^® variety Acala 90B and its efficacy against lepidopteran larvae. Larvae of Alabama argillacea (Hübner) and Spodoptera frugiperda (J.E. Smith) were respectively caged on terminals and whole cotton plants in the field, and cotton leaves, flower buds, and soft bolls in the laboratory for both larvae. The Cry1Ac production was measured using ELISA assays. The mean levels of Cry1Ac (?g of Cry1Ac g^-1 of fresh tissue) ranged according to the cotton plant parts across the season with higher levels in the leaves (0.28 ?g), followed in the flower buds (0.101 ?g), in the square bracts (0.067 ?g), and in the skin of the soft boll (0.014 ?g). Levels of Cry1Ac in cotton plants, assayed only in leaves, during low rain season were similar to those produced by unstressed plants (0.21 versus 0.23 ?g de Cry1Ac g^-1 of fresh tissue). A. argillacea is efficiently controlled irrespective of parts of the Acala 90B plants in the laboratory and in the field, while S. frugiperda exhibited mortality similar in Acala 90B and its isoline non-Bt.