Impact of Endochitinase-Transformed White Spruce on Soil Fungal Biomass and Ectendomycorrhizal Symbiosis

The impact of transgenic white spruce [Picea glauca (Moench) Voss] containing the endochitinase gene (ech 42) on soil fungal biomass and on the ectendomycorrhizal fungiWilcoxina spp. was tested using a greenhouse trial. The measured level of endochitinase in roots of transgenic white spruce was up to 10 times higher than that in roots of nontransformed white spruce. The level of endochitinase in root exudates of three of fourech 42-transformed lines was significantly greater than that in controls. Analysis soil ergosterol showed that the amount of fungal biomass in soil samples from control white spruce was slightly larger than that in soil samples fromech 42-transformed white spruce. Nevertheless, the difference was not statistically significant. The rates of mycorrhizal colonization of transformed lines and controls were similar. Sequencing the internal transcribed spacer rRNA region revealed that the root tips were colonized by the ectendomycorrhizal fungiWilcoxina spp. and the dark septate endophytePhialocephala fortinii . Colonization of root tips byWilcoxina spp. was monitored by real-time PCR to quantify the fungus present during the development of ectendomycorrhizal symbiosis inech 42-transformed and control lines. The numbers ofWilcoxina molecules in the transformed lines and the controls were not significantly different (P > 0.05, as determined by analysis of covariance), indicating that in spite of higher levels of endochitinase expression, mycorrhization was not inhibited. Our results indicate that the higher levels of chitinolytic activity in root exudates and root tissues fromech 42-transformed lines did not alter the soil fungal biomass or the development of ectendomycorrhizal symbiosis involvingWilcoxina spp.