• Research in Plant Disease
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• v.18 no.4
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• pp.317-323
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• 2012

The study aims to identify the pathogenicity of Phytophthora. capsici isolates in major pepper-producing areas in Korea and the inherit genetic pattern of phytophthora blight resistance by inocula. With five kinds of testing materials including 'Kataguma (Sakata Korea)' peppers, a disease-susceptible material, '#308', a phytophthora blight resistance material, 'CM334', and their $F_1$ and $F_2$, respective isolates of P. capsici obtained from Icheon, Eumseong, Buan, Imsil and Yeongyang regions together with six kinds of peppers' inoculum including PA-159 (KACC No.40482) received from Korean Agricultural Culture Collection were used for inoculation. The disease-susceptible material '#308', the resistant material 'CM334' and the non-segregating generation of $F_1$ represented 4.94-5.00, 1.00-1.07, and 1.01-1.08 phytophthora blight incidence respectively in the group comparison by isolate. This result means that the phytophthora blight resistance was clearly distinguished among testing materials in the group comparison by P. capsici isolate. Moreover, $F_2$ segregating generation showed 1.79-2.31 phytophthora blight incidence which turned out to be identical in the group comparison by the six isolates of P. capsici isolate and with similarity between both the resistant and susceptible materials. Thus, the result proved that using the six isolates of P. capsici tested as inocula was suitable to investigate the phytophthora blight resistance. When it comes to group comparison of $F_2$ segregation generation, however, isolates were divided with PA-159 isolate being the center: a group consisting of isolates from Icheon, Buan, and Imsil and a group consisting of Yeongyang and Eumseong isolates with higher pathogenicity. The expected segregation ratio of the phytophthora blight resistance in $F_2$ generation by isolate was analyzed. PA-159 isolate showed 3:1 or 9:3:3:1, indicating that one to two genes were involved. On the other hand, results also proved that there is an interaction of genes since both Eumseong and Yeongyang isolates showed a segregation ratio of 11:5 while the Icheon isolate represented 12:3:1.