Enhanced resistance to fungal pathogens in forest trees by genetic transformation of black spruce and hybrid poplar with a Trichoderma harzianum endochitinase gene

An endochitinase gene (ech42) from the biocontrol fungus Trichoderma harzianum was introduced into black spruce (Picea mariana) and hybrid poplar (Populus nigra×Populus maximowiczii) by Agrobacterium-mediated transformation. Fifteen transgenic black spruce lines and six poplar lines were obtained. Northern hybridization analysis showed an increased accumulation of the transcript encoding the recombinant endochitinase gene in all the transgenic plants tested. Endochitinase activity 55-115 times the level of the control was detected in transformed poplar leaves. Embryogenic tissue of transgenic black spruce showed endochitinase activity two to eight times that of the non-transgenic line, despite stronger basal endogenous activity. In vitro assays using inoculated leaf disks demonstrated that the transgenic poplars had increased resistance to the leaf rust pathogen Melampsora medusae. Seedlings of transgenic spruce lines showed an increased resistance to the spruce root pathogen Cylindrocladium floridanum in vitro. These results suggest that constitutive expression of the ech42 gene from T. harzianum could be exploited to enhance resistance to fungal pathogens in important forest tree species.