Influence of Bt Transgenes on Cell Wall Lignification and Digestibility of Maize Stover for Silage

Abstract

There have been inconsistent reports that maize (Zea mays L.) hybrids with the Bacillus thuringiensis (Bt) cry1 Ab transgene contain more lignin than non‐Bt hybrids of similar genetic background. Our objective was to evaluate the impact of the cry1 Ab transgene on lignin concentration (using three different assays), yield, and forage quality traits of maize. Replicated trials were conducted at four locations in Minnesota with 12 commercial hybrids (three MON810 and three Bt11 cry1 Ab transgene event hybrids, and respective near‐isogenic controls). Whole plants and the fourth elongated, above‐ground internodes were harvested at silage maturity. Samples were analyzed for crude protein, starch, neutral detergent fiber (NDF), acid detergent fiber, 24‐ and 96‐h in vitro ruminal NDF digestibility, and lignin (acid detergent, Klason, and acetyl bromide). European corn borers (Ostrinia nubilalis Hübner) were not controlled and damage was limited to the non‐Bt hybrids, averaging 1.5 internodes plant−1 with tunnels. Environment and environment × hybrid interactions affected all measures of maize performance and quality, but comparisons of non‐Bt/Bt hybrid pairs, for both whole plants and internodes, found no consistent differences in yield, nutrient content, in vitro ruminal NDF digestibility, or lignin concentration. Differences in lignin concentration were infrequent, small in magnitude, and inconsistent between a few non‐Bt/Bt hybrid pairs at individual locations. Two non‐Bt/Bt hybrid pairs did not differ in lignin concentration at any location. Contrary to some earlier reports, presence of the cry1 Ab transgene did not alter lignin concentration or other forage quality traits of maize stover in commercial maize hybrids.