전북지방을 중심으로 감자포장에 발생하는 역병 발생율 및 분리된 병원균의 교배형을 조사하였다. 1991년도 전북지방의 역병 발생율은 4~90%(평균 34.2%) 범위였으며, 92년도에는 1~75%(평균 21.6%)로 이 차이는 병발생시기의 기상요인에 의한 것이었다. 이병엽에서 분리된 역병균의 교배형은 91년에는 A₂형이 99%(200/202균주)였으며, 92년에는 100%(98/98균주)로 조사되어 대부분이 A₂임이 판명되었다. 또한 A₁형과 A₂형의 분리균주를 배양함으로써 저착성의 장정기를 가진 장난기가 형성되었다. A₂형의 많은 균주는 4주째 단독배양에서도 소수의 난포자를 형성하였다.
The rate of occurrence of potato late blight and mating types of the pathogen, Phytophthora infestans at potato growing fields in Korea were investigated in this study. Incidence of the late blight was in the range of 4~90% (average of 34.2%) and 1~75% (average of 21.6%) in 1991 and 1992, respectively, in Chonbuk Province. The yearly difference in the incidence was apparently attributed to the different weather conditions. When the isolates obtained from infected potato leaves were mated with standard A₁ and A₂ mating types, 200 among 202 isolates were A₂ types in 1991 and all were A₂ types in 1992. When A₁ and A₂ types were mated, oogonia with amphigynous antheridia and oospores were formed in great abundance at the juncture of two colonies. However, most of A₂ type isolates formed small amount of oospores after 4 weeks in single culture of A₂ type without mating in 5% clear V-8 juice agar medium.