• The Plant Pathology Journal
• /
• v.25 no.4
• /
• pp.317-321
• /
• 2009

Sensitivity to the new carboxylic acid amide fungicide, mandipropamid, of Phytophthora capsici causing pepper Phytophthora blight was determined on 187 isolates collected in Korea over 3 years, from 2005 to 2007. All isolates were sensitive to mandipropamid, with $EC_{30}$ values for growth of mycelia ranging from 0.001 to $0.037\;{\mu}g/ml$. Among the isolates, 147 (79.0%) isolates were sensitive to metalaxyl, whereas others were resistant to this fungicide. Mandipropamid had the same effect on mycelium growth of both metalaxyl-sensitive and metalaxyl-resistant isolates, indicating an absence of cross-resistance between these two fungicides. Comparison of the sensitivities of P. capsici isolates showed a positive correlation between sensitivity to mandipropamid and dimethomorph ($r^2$=0.8533). The results of this study indicate that there is no evidence for development of resistance to mandipropamid in this population of P. capsici isolates collected in Korea.

• The Korean Journal of Mycology
• /
• v.30 no.1
• /
• pp.66-72
• /
• 2002

To develop DNA markers for analysis of genetic characteristics of Phytophthora capsici population, randomly selected clones from HindIII-digested genomic DNA library of P. capsici 95CY3119 were surveyed by hybridizing to Southern blots of HindIII-digested total genomic DNA of P. capsici. Probe DNAs inserted into selected individual clones strongly hybridized with HindIII digests of P. capsici. Among probes examined, PC9 revealed the repetitive and highly polymorphic bands to HindIII digests of inter-and intra-field P. capsici isolates. Genetic diversity of individual isolates was also clearly revealed in cluster analysis based on its band patterns. The other probe, PC22, was hybridized only to DNA from P. capsici and this was highly repetitive. However, there was no response to other Phytophthora species and Pythium sp. These DNA probes could be used as very useful markers in analysing genetic diversity and identification for P. capsici population throughout the world.

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

• The Plant Pathology Journal
• /
• v.29 no.2
• /
• pp.154-167
• /
• 2013

We previously developed a sequential screening procedure to select antagonistic bacterial strains against Phytophthora capsici in pepper plants. In this study, we used a modified screening procedure to select effective biocontrol strains against P. capsici; we evaluated the effect of selected strains on Phytophthora blight and anthracnose occurrence and fruit yield in pepper plants under field and plastic house conditions from 2007 to 2009. We selected four potential biocontrol strains (Pseudomonas otitidis YJR27, P. putida YJR92, Tsukamurella tyrosinosolvens YJR102, and Novosphingobium capsulatum YJR107) among 239 bacterial strains. In the 3-year field tests, all the selected strains significantly (P < 0.05) reduced Phytophthora blight without influencing rhizosphere microbial populations; they showed similar or better levels of disease suppressions than in metalaxyl treatment in the 2007 and 2009 tests, but not in the 2008 test. In the 2-year plastic house tests, all the selected strains significantly (P < 0.05) reduced anthracnose incidence in at least one of the test years, but their biocontrol activities were variable. In addition, strains YJR27, YJR92, and YJR102, in certain harvests, increased pepper fruit numbers in field tests and red fruit weights in plastic house tests. Taken together, these results indicate that the screening procedure is rapid and reliable for the selection of potential biocontrol strains against P. capsici in pepper plants. In addition, these selected strains exhibited biocontrol activities against anthracnose, and some of the strains showed plant growth-promotion activities on pepper fruit.

• The Plant Pathology Journal
• /
• v.26 no.4
• /
• pp.340-345
• /
• 2010

Two similar microbial fungicides (termed as MA and MB) developed in a Korean biopesticide company were analyzed and compared each other in their biocontrol activities against the phytophthora blight of chili pepper caused by Phytophthora capsici. MA and MB contained the microbe Paenibacillus polymyxa and Bacillus subtilis, respectively, with concentrations over those posted on the microbial products. In comparison of the isolated microbes (termed as MAP from MA and MBB from MB) in the antagonistic activities against P. capsici was effective, prominently against zoospore germination, while MBB only significantly inhibited the mycelia growth of the pathogen. Some effectiveness of MAP and MBB was noted in the inhibition of zoosporangium formation and zoospore release from zoosporangia; however, no such large difference between MAP and MBB was noted. In a pot experiment, MA reduced the severity of the phytophthora blight more than MB, suggesting that the disease control efficacy would be more attributable to the inhibition of zoospore germination than mycelia growth of P. capsici. These results also suggest that the similar microbes MA and MB targeting different points in the life cycle of the pathogen differ in the disease control efficacies. Therefore, to develop microbial fungicides it is required to examine the targeting points in the pathogen's life cycle as well as the action mode of antagonistic microorganisms.

• Current Research on Agriculture and Life Sciences
• /
• v.28
• /
• pp.17-23
• /
• 2010

Selection procedures for breeding genic male sterile lines for resistance to both Phytophthora blight caused by Phytophthora capsici and bacterial spot caused by Xanthomonas euvesicatoria were executed to $F_3$ and $F_4$ generations derived from a cross between a Phytophthora resistant genic male sterile (GMS) breeding line and a bacterial spot and Phytophthora resistant breeding line. Resistance to P. capsici was originally introduced from KC294(CM334) and KC263(AC2258), the well-known sources of resistance to P. capsici. Resistance to bacterial spot was introduced from KC47(PI244670). GMS lines with high resistance to P. capsici were obtained and the selected lines are expected to be quantitatively resistant also to bacterial spot.

• Korean Journal of Environmental Agriculture
• /
• v.15 no.3
• /
• pp.289-295
• /
• 1996

This study was attempted to select an antagonist against Phytophthora blight of red-pepper caused by Phytophthora capsici. The three strains, A-35, A-67 and A-183 were isolated from the rhizosphere in soil where red-pepper had been cultivated continuously for a long time, and the strain A-83 was estimated to be the strongest antagonist against P. capsici. The A-183 strain was identified as a strain of Pseudomonas sp., showing the maximum antifungal activity, when cultured at $30^{\circ}C$ for 5 days in the potato extract medium(pH 6.5) containing 2.0% mannitol and 0.3% peptone.

• Research in Plant Disease
• /
• v.28 no.3
• /
• pp.143-151
• /
• 2022

In order to investigate the cause of wilting symptoms in red pepper field of Korea, the frequency of occurrence of red peppers showing wilting symptoms was investigated in pepper cultivation fields in Goesan, Chungcheongbuk-do for 5 years from 2010 to 2014. There was a difference in the frequency of wilting symptoms depending on the year of investigation, but the frequency of occurrence increased as the investigation period passed from June and July to August. During this period, Ralstonia solanacearum causing the bacterial wilt was isolated at a rate four times higher than Phytophthora capsica causing the Phytophthora late blight. In wilted peppers collected in Goesan of Chungbuk and Andong of Gyeongbuk in 2013 and 2014, R. solanacearum and P. capsici were isolated from 20.3% and 3.8% of the total fields, respectively. In the year with a high rate of wilting symptoms, the average temperature was high, and the disease occurrence date of the bacterial wilt, estimated with disease forecasting model, was also fast. The inconsistency between the number of days at risk of Phytophthora late blight and the frequency of occurrence of wither symptoms is thought to be due to the generalization of the use of cultivars resistant to the Phytophthora late blight in the pepper field. In our study, the wilting symptoms were caused by the bacterial wilt caused by R. solanacearum rather than the Phytophthora late blight caused by P. capsica, which is possibly caused by increasing cultivation of pepper varieties resistant to the Phytophthora late blight in the field.

• The Plant Pathology Journal
• /
• v.20 no.3
• /
• pp.177-183
• /
• 2004

Phenylacetic acid (PAA) was evaluated for in vitro anti-oomycete activity and in vivo control efficacy against Phytophthora capsici. Microscopic observation revealed that the high level of anti-oomycete activity of PAA (10 $\mu\textrm{g}$/ml) against P. capsici is mainly due to the lytic effect on zoospores. Zoospore lysis began in the presence of 5 u$\mu\textrm{g}$/ml of PAA and most of the zoospores were collapsed at 10 $\mu\textrm{g}$/ml. PAA showed inhibitory activity against the zoospore germination and hyphal growth of P. capsici at the concentration of 50 $\mu\textrm{g}$/ml. In the glasshouse, the protective effect of PAA against Phytophthora blight was high on pepper plants when treated just before inoculation with P. capsici. In the artificially infested field, protection of pepper plants against the Phyto-phthora epidemic was achieved at a considerable level by PAA treatment.

• Proceedings of the Korean Society of Plant Pathology Conference
• /
• 2003.10a
• /
• pp.86-86
• /
• 2003

Phytophthora capsici is a pathogen on several economically important crops including pepper. In pepper growing areas in Korea, Phytophthora blight caused by p. capsici has been considered as the most serious problem in pepper production. The Oomycete attacks the roots, stems, leaves and fruits of the plant. To understand the molecular mechanisms involved in the disease development, the genes expressed doting pepper p. capsici interaction were explored by analyzing expressed sequence tags (ESTs). A complementary DNA (cDNA) library was constructed from total RNA extracted from pepper leaves challenged with p. capsici for 3 days resulting in early stage of symptom development. The comprehensive analysis on the single pass sequencing of over 4000 randomly selected cDNA clones with contig assembly, unique gene extraction, sequence comparison, and functional categorizing will be presented with an emphasis on the genes involved in plant defense and pathogenicity during disease development of the pepper Phytophthora blight.