Pathogenicity and Virulence of a Canadian isolate of Phytophthora capsici on pepper

Phytophthora capsici is a soil borne plant pathogen that has spread globally infecting economically important crops. In Ontario, infection of peppers, tomatoes and cucurbits by P. capsici has become severe problem in recent years. P. capsici virulence may vary depending on geographic location but little is known about the pathogenicity of Canadian isolates. The aim of this study is to determine the pathogenicity and comparative virulence of a Canadian P. capsici isolate and two isolates from New York state and Michigan state, USA. Pure culture of P. capsici, isolated from Ontario, was established and characterized using morphological and molecular techniques. The molecular identification of the Canadian isolate was conducted by sequencing the ITS region, after which the complete genome was sequenced using both Illumina and PacBio sequencing technology to obtain reliable assembly and annotation. The virulence of different isolates from Ontario, New York and Michigan was evaluated by inoculating pepper leaves with a suspension of 5 × 104 zoospores/ml. Disease progression in terms of lesion development was measured 5 days after inoculation using the software ImageJ. Preliminary results show that there is a difference in virulence between the tested isolates, the most virulent isolate came from New York followed by Michigan and lastly the isolate from Ontario. A greenhouse experiment is currently being conducted to test the pathogenicity of isolates on greenhouse-grown pepper plants. The annotated and characterized genome assembly of the Canadian P. capsici will be compared with other P. capsici to gain insights into its pathogenic lifestyle. Improved understanding of P. capsici interactions with host plants may enable pathologists to more effectively evaluate strategies to control phytophthora leaf blight, root and crown rot diseases.