Enhanced resistance to late blight pathogen conferred by expression of rice oxalate oxidase 4 gene in transgenic potato

Phytophthora infestans is the pathogen responsible for late blight disease of potato. Multiple spraying of crop protection chemicals is so far the only means to control the disease. Despite the continuous effort from breeders, late blight resistant potato varieties are not available to farmers. In this context, development of genetic resistance by incorporating new genes through genetic engineering is an attractive way to combat the pathogen. Here, we report the development of transgenic potato cultivars overexpressing the rice oxalate oxidase 4 gene (Osoxo4). Transgenic lines showed higher activity of oxalate oxidase enzyme and were able to degrade externally applied oxalic acid. The levels of reactive oxygen H2O2 were elevated in transgenic plants. The transcription of defense related genes (anionic peroxidase and phenylalanine ammonia lyase) was found to be elevated after pathogen inoculation. Detached leaf bioassays with spore suspension and in vitro plantlet bioassays with mycelia of P. infestans showed enhanced resistance in transgenic plants. Interestingly, constitutive overexpression of Osoxo4 did not show any effect on the morphology and yield of transgenic potato plants as evident from agronomic performance studies. Thus, constitutive expression of Osoxo4 represents an efficient strategy for engineering late blight resistance in potato.