• The Plant Pathology Journal
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• v.30 no.4
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• pp.416-424
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• 2014

Sweet potato is grown extensively from tropical to temperate regions and is an important food crop worldwide. In this study, we established detection methods for 17 major sweet potato viruses using single and multiplex RT-PCR assays. To investigate the current incidence of viral diseases, we collected 154 samples of various sweet potato cultivars showing virus-like symptoms from 40 fields in 10 Korean regions, and analyzed them by RT-PCR using specific primers for each of the 17 viruses. Of the 17 possible viruses, we detected eight in our samples. Sweet potato feathery mottle virus (SPFMV) and sweet potato virus C (SPVC) were most commonly detected, infecting approximately 87% and 85% of samples, respectively. Furthermore, Sweet potato symptomless virus 1 (SPSMV-1), Sweet potato virus G (SPVG), Sweet potato leaf curl virus (SPLCV), Sweet potato virus 2 ( SPV2), Sweet potato chlorotic fleck virus (SPCFV), and Sweet potato latent virus (SPLV) were detected in 67%, 58%, 47%, 41%, 31%, and 20% of samples, respectively. This study presents the first documented occurrence of four viruses (SPVC, SPV2, SPCFV, and SPSMV-1) in Korea. Based on the results of our survey, we developed multiplex RT-PCR assays for simple and simultaneous detection of the eight sweet potato viruses we recorded.

• The Plant Pathology Journal
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• v.30 no.4
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• pp.407-415
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• 2014

Viral diseases have been a major limiting factor threating sustainable potato (Solanum tuberosum L.) production in Pakistan. Surveys were conducted to serologically quantify the incidence of RNA viruses infecting potato; Potato virus X (PVX), Potato virus Y (PVY), Potato virus S (PVS), Potato virus A (PVA), Potato virus M (PVM) and Potato leaf roll virus (PLRV) in two major potato cultivars (Desiree and Cardinal). The results suggest the prevalence of multiple viruses in all surveyed areas with PVY, PVS and PVX dominantly widespread with infection levels of up to 50% in some regions. Co-infections were detected with the highest incidence (15.5%) for PVX and PVS. Additionally the data showed a positive correlation between co-infecting viruses with significant increase in absorbance value (virus titre) for at least one of the virus in an infected plant and suggested a synergistic interaction. To test this hypothesis, glasshouse grown potato plants were challenged with multiple viruses and analyzed for systemic infections and symptomology studies. The results obtained conclude that multiple viral infections dramatically increase disease epidemics as compared to single infection and an effective resistance strategy in targeting multiple RNA viruses is required to save potato crop.

• Research in Plant Disease
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• v.18 no.4
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• pp.338-348
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• 2012

Potato late blight caused by Phytophthora infestans Cooke is one of the major diseases in the cultivation of potatoes in Korea. Effect of chitosan preparations (SH-1 and SH-2) was evaluated on the inhibition of mycelial growth of P. infestans, and protective activity using detached potato leaf assay both in vivo and in the field test. SH-1 and SH-2 were showed protective activity of young plant with control values more than 95% potato late blight by inoculation with pathogens under growth chamber conditions. Mycelial growth was inhibited the radial growth over 74% at a concentration of $300{\mu}g/ml$ of both SH-1 and SH-2. Spraying with SH-1 and SH-2 on the leaves for detached leaf assay reduced disease development. The content of total polyphenol in stem was significantly increased by SH-1 and SH-2 application in the field. In field experiments, foliar application with both SH-1 and SH-2 were significantly reduced the development of late blight on potato plants. Control of late blight disease was obtained with control values of 72% and 53% by application of 1% SH-1 and SH-2, respectively, with 4 times at 7 days interval, and reduced with similar disease control values by application with 3 times at 14 days interval compared with untreated control. SH-1 and SH-2 applications increased the fresh weight of potato, and higher grade potatoes were also increased. The results showed that SH-1 and SH-2 applications can be used as eco-friendly natural fungicide for organic farming for the increase of yields and control of late blight.

• Research in Plant Disease
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• v.21 no.4
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• pp.330-333
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• 2015

In June 2013, we collected leaf spot disease samples of Datura metel from Gangneung, Gangwon Province, Korea. The symptoms observed were small circular to oval dark brown spots with irregular in shape or remained circular with concentric rings. We isolated the pathogen from infected leaves and cultured the fungus on potato dextrose agar. We examined the fungus morphologically and confirmed its pathogenicity according to Koch's postulates. The results of morphological examinations, pathogenicity tests, and the rDNA sequences of the internal transcribed spacer regions (ITS1 and ITS4), glycerol-3-phosphate dehydrogenase (G3PDH) and the RNA polymerase II second largest subunit (RPB2) gene sequence revealed that the causal agent was Alternaria tenuissima. To the best of our knowledge, this is the first report of leaf spot of D. metel caused by A. tenuissima in Korea as well as worldwide.

• Journal of the Korean Society of Tobacco Science
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• v.15 no.1
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• pp.15-25
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• 1993

The severities of major tobacco diseases had been surveyed throughout northern Kyeongbuk, a major flue-cured tobacco growing district in Korea, in relation to the actual control method used by the farmers in 1992. At seedling stage, anthracnose caused by Colletotrichum nicotianae was major disease of the plant due to poor damage of the temporary transplanting pots. Mosaic caused by tobacco mosaic virus(TMV) was very severe in certain of greenhouses. Although viral disease caused by TMV, cucumber mosaic virus(CMV) and by potato virus Y(PVY) were severe in fields, but mosaic by TMV was major of the diseases. Potato virus Y was found later than that in Honam district. The late occurrence of the disease might be caused the difference between cultivating method of potato plants in northern Kyeongbuk and that in Honam district. In fields suffered from hail disaster, the damage of tobacco plants by angular leaf spot was severe. Most of tobacco growers had wrong information about the practical methods not only of milk treatment for the protection of the plants from TMV, but also of fungicide applications for the control of other major diseases. It suggested that education on the methods to the farmers must be very important for control of the diseases.

• Korean journal of applied entomology
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• v.51 no.4
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• pp.377-382
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• 2012

This study investigated the occurrence of sweet potato whitefly, Bemisia tabaci affecting cucumber, eggplant and red pepper, as well as sweet potato species, and its response to insecticides in Gyeonggi province from 2010 to 2011. Sweet potato whitefly is widespread throughout the southern part of Gyeonggi province. Most regional populations of B. tabaci belong to biotype Q having been reported in the south Korea since 2005, but in Goyang mixed populations of two biotypes (B and Q) were found. Survey results of Tomato Yellow Leaf Curl Virus (TYLCV) disease that was vectored by B. tabaci indicated that this virus disease was not spread throughout the Gyeonggi province. Biotype Q of B. tabaci was found to be resistant to neonicotinoid insecticides, whereas biotype B was highly susceptible to them.

• The Korean Journal of Pesticide Science
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• v.5 no.1
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• pp.1-11
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• 2001

Climate in the year of 2000 was characterized as a long severe drought in tile spring, unusually high and low temperature in summer, two times of typoons, and floods by heavy rains in fall. Rice leaf and panicle blast and bacterial grain rot occurred severely comparing with 1999 and Bipolaris leaf spot spread over tile country. Phytophthora blight and anthracnose in red-pepper became epidemic especially in the late season causing severe yield losses. Tomato fusaruim wilt, CGMMV, powdery mildew, and sudden wilt syndrom of cucurbits and strawberry powdery mildew were also severe in 2000. In garlic, sclerotium rot occurred severely mainly due to the frequent rainfalls in planting time and much snowfalls in 1999's winter. Spring potato had severe infection of viruses due to a long spring drought, and fall potato had high incidence of bacterial soft rot and bacterial wilt due to fall floods by heavy rains. In sweet potato fusarium wilt was the most severe as in other year. Disease incidence of apple and pear trees was rotatively mild compared with previous years. In wheat and barley, Gibberella petch rarely occurred because of spring drought.

• Korean journal of applied entomology
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• v.18 no.4 s.41
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• pp.183-188
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• 1979

The study has been carried to describe a new disease of strawberry in Korea, which was found in 1977 at Kimhae. Symptom of the disease occurred mainly on leaves as showing large annular brown spots or 'V' shaped brown lesions. Many of dark pycnidia were observed from the both side of old lesions. The pathogen was identified as Dendrophoma obscurans (Ell. & Ev) Anderson which has not been described in Korea as a pathogen of strawberry disease. The common name of the disease was given, temporaly, as Annular leaf blight of strawberry. In the laboratory study, light was necessary for the production of pycnidia and potato dextrose agar was the best media for tile pycnidia formation. There were some difference on resistance to the disease among 48 tested strawberry varieties though none of them shelved highly resistant reaction, and the older leaves showed more susceptible reaction than younger ones.

• Research in Plant Disease
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• v.13 no.2
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• pp.126-129
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• 2007

Sooty leaf blight disease of Cymbium spp. was observed on orchid fields located at Gyeonggi-do in 2005-2006. Symptoms of the disease appeared on leaves and leaf spots were circular to nearly-circular, these circular blemished were yellow, with greater amounts of brown to black flecks forming as the spots enlarge. Severely infected leaves were dry and defoliated. These symptoms were realized wrongly as symptoms by virus. But Pseudocercospora cymbidiicola were isolated from the diseased plants. Conidiophores were produced on the lesion surface of the leaf with the blemished areas andconidia formed dark brown, cylindrical and straight to slightly curved, 5-9 septate, $23.7-85.0\;{\times}\;2.0-3.4\;{\mu}m$. Mycelial growth was mostly slow on potato dextrose agar and the optimum temperature for growth was $25^{\circ}C$. We were identified as Pseudocercoepora cymbidiicola based on the morphological characteristics.

• Research in Plant Disease
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• v.16 no.1
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• pp.94-96
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• 2010

In May of 2004 through 2007, Leptosphaerulina leaf blight caused by Leptosphaerulina trifolii occurred on Kentucky bluegrass (Poa pratensis) at golf courses in Gangwon Province, Korea. Symptoms on the turfgrass caused by L. trifolii were leaf blights, dying from the leaf tip downwards to the crown, which appeared patches in the field because of local pockets of severely infected (blighted) grass. Perithecia were produced on old or weak leaves, including club-shaped asci, each of which contained 8 pale brown muriform ascospores with cross and longitudinal septa. Ascospores of the fungus isolated from the diseased leaf tissue and cultured on potato-dextrose agar (PDA) were muriform multicellular (composed of 3-6 cells) and $23.4-40.5{\times}7.8-15.6{\mu}m$ in size with 3-4 transverse and 0-3 longitudinal septa, which were morphologically identical to L. trifolii reported previously. DNA sequences of ribosomal RNA gene (internal transcribed spacer) of the fungus were homologous with similarity of 99% to those of L. trifolii isolates in GenBank database, confirming the identity of the causal agent of the disease. Pathogenicity of the fungus was also confirmed on the creeping bentgrass by Koch's postulates. This is first report of Leptosphaerulina leaf blight on turfgrass caused by L. trifolii in Korea.