Race Identification of Phytophthora Parasitica var. Nicotianae in Yunnan Province

The distribution of pathogen races is distinguished in different region. The study of race in Yunnan Province is benefit to planning tobacco variety with a purpose of disease-resistant and disease-prevent. So pathogenicity and race of the pathogen in Yunnan Province was determinate by the method of injured roots inoculation. The result showed that the incidence of 39 strains isolated in 2004 was from 22.22% to 100.00%, 93.73% in average, the disease index was 2.8~86.1 and the incidence of 45 strains isolated in 2005 was from 66.67% to 100.00%, 96.05% in average, the disease index was 16.7~97.2. The tested 55 isolates differ greatly in pathogenicity to same variety and their pathogenic differentiation was obvious in different varieties. In this paper we concluded that 50 isolates was race 0. Race 0 was the superior race of Phytophthora parasitica var. nicotianae in Yunnan province.