Pathogenicity of Phytophthora infestans on solanaceous and asteraceous plant species in Cameroon

Experiments were conducted to detect potential hosts of Phytophthora infestans, causal agent of potato late blight. Isolates of P. infestans recovered from garden huckleberry (Solanum scabrum), potato (S. tuberosum) and tomato (Lycopersicon esculentum) were inoculated on detached leaves of 12 solanaceous and 14 asteraceous plant species collected in and around potato fields in the western highlands of Cameroon. The inoculated leaves were maintained in Petri dishes in the laboratory for 7 days at 20-22 degrees C. Isolates of P. infestans from huckleberry, potato and tomato infected the same host plants as well as the gboma eggplant (Solanum macrocarpon) and two asteraceous weeds, Ageratum conyzoides and Solanecio biafrae. Inocula recovered from infected S. macrocarpon caused late blight symptoms on huckleberry, potato and tomato both under laboratory and screen house conditions, while those from both asteraceous weeds reinfected potato in the laboratory and inoculum from S. biafrae reinfected huckleberry in the screen house. This is a first observation of late blight infection on S. macrocarpon, A. conyzoides and S. biafrae in Cameroon. Results indicate the importance of both asteraceous weeds and S. macrocarpon as potential alternative hosts for P. infestans in garden huckleberry, potato or tomato fields.