B. Horizontal resistance水平抗病性 a variety is resistant to many races of a pathogen with a rather even eve Non race-specific resistance: Polygenes, minor effects Big environmental Influence: Durable resistance Incidence Race a b c dB. Horizontal Resistance 水平抗病性 A variety is resistant to many races of a pathogen with a rather even level. Non race-specific resistance: Polygenes, minor effects Big environmental Influence; Durable resistance Race a b c d e f Incidence %