Reduction of lesion growth rate of late blight plant disease in transgenic potato expressing harpin protein.

Using harpin protein gene from apple fire blight pathogen Erwinia amylovora and potato prp1-1 promoter as main DNA elements, the feasibility of using pathogen infection-induced hypersensitive response was explored as a new strategy of engineering fungal disease resistance. Three plant transformation vectors were constructed and 68 transgenic potato plants were produced through Agrobacterium mediated transformation method. Southern, Northern and Western blot analysis demonstrated the insertion, transcription and protein expression of harpin protein gene in transgenic plants. Disease resistance test using a complex race of Phytophthora infestans as challenging pathogen showed that both constitutive and pathogen infection-induced expression of harpin protein gene in transgenic potato reduced the lesion growth rate of fungus. Among plants where harpin protein gene expression was induced only by fungus infection, two plants were found to be highly resistant to P.infestans infection. Fungal hyphae were not produced on total of 30 inoculated leaves from the two resistant plants and necrotic lesion was limited to inoculation area. The results highlighted that engineered hypersensitive response in plants was a very promising approach to produce fungal disease resistant genotype.