First investigations into the effects of Bt corn crop on Nematofauna

Abstract

The research, done in 1999, was carried out in 8 north Italian localities in fields planted with isogenic and transgenic corn (Event 176, Novartis). The objective was to find a first indication of the possible effect of transgenic corn on soil fauna and, in particular, on the nematode community, considered a good indicator of the trophic chain state. The nematode community was investigated for general composition, trophic structure and biodiversity, and the findings from Bt and isogenic fields of corn were compared. The classification of 2,000 nematodes belonging to 22 families and 45 different genera was made. The most abundant was Rhabditis, which was common to all regions and which often dominated, followed by Pratylenchus, Helicotylenchus and Acrobeloides. These genera made up more than 70% of the total nematodes extracted. The dominant trophic group was the bacteriophagous, followed by the phytophagous. For a synthetic description, and a comparison of the different communities, calculations were made of several biodiversity indexes (Shannon, Hill numbers, Pielou index), the maturity index and the Sorensen similarity index. All the examined sites were found to have quite low biodiversity, the H' values being not more than 1.08. The data, independently of the presence of the transgenic hybrid, indicate a high level of disturbance. The Bt transgenic corn cultivation appears to have no significant influence on the nematofauna, neither at the level of genus composition nor with regard to biodiversity. Nevertheless one region did have a change in trophic group composition: fungal feeders nematodes were more numerous in the soil with Bt corn, while in the field with the isogenic hybrid the bacterial feeders percentages were higher.