Chemical Characteristics and Effects on Soil Microbial Activity of Leaves from Tomato Plants Genetically Modified with a Transgene for Pathogen Resistance

Abstract

The chemical composition of leaves from transgenic tomato plants (RC332) showing tolerance to attack by some pathogens has been compared with those from untransformed control line (RIG). In addition, the respiration of soil amended with transgenic plant leaf residues was determined. The RC332 plants had the Gox gene coding d-glucose oxygen 1-oxido-reductase (GOD) enzyme. The chemical composition [soluble proteins, total nitrogen (N) and lignin contents] of the tomato leaves was determined to establish the quality of the organic residues entering the soil. The transgenic plants contained more nitrogen and insoluble lignin and less soluble protein than the control plants. Soil amended with leaves from the two lines had different respiration rates; both dried and fresh leaves from 130-day-old RC332 plants determined a lower soil respiration than untransformed material over the first 2 days of incubation. This difference was probably due to the larger lignin content or the smaller soluble protein content of the transgenic material. Compared with the control plants, significantly less CO2 was released when leaves from 60-day-old RC332 plants over the initial few hours of incubation, but only when they were applied to soil as fresh material, possibly because of the H2O2 presence in the plant material.