Korean Agricultural Culture Collection Research Articles

First Confirmed Report of Anthracnose Fruit Rot Caused by Colletotrichum gloeosporioides on Common Fig in Korea.

Common fig (Ficus carica L.) was introduced into Korea in the 1890s from Japan and planted in residential gardens for home consumption. Commercial cultivation of the tree did not begin until the 1990s (2). In early August 2012, several dozen unripened fig fruits, cv. Banane, were found damaged by fruit rot in an experimental plot of Jeollabuk-do Agricultural Research and Extension Services, Iksan City, South Korea (GPS coordinates 35°56'38.44″ N, 126°59'37.14″ E). Though infections recurred until late September, infection rates were as low as 1 to 5%. Early symptoms appeared as small, slightly sunken, water-soaked, and circular spots. Lesions increased in size, became more depressed, with a darkened central portion. The darkened areas contained blackish acervuli from which masses of salmon-colored conidia were released in moist weather. A semisoft decay resulted, sometimes causing premature fruit drop. No symptoms were found on leaves. Acervuli were circular to ellipsoid, 50 to 400 μm in diameter. Acervular setae were 2- to 3-septate, dark brown at the base, paler toward the apices, acicular, and up to 120 μm long. Conidia (n = 30) were long obclavate to oblong-elliptical, sometimes fusiform-elliptical, guttulate, hyaline, and 16 to 21 × 4 to 6 μm. These characters were consistent with the description of Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. (4). From an isolate (KACC46943, deposited in the Korean Agricultural Culture Collection), fungal DNA was extracted, and the complete internal transcribed spacer (ITS) region of rDNA was amplified with the primers ITS1(5'-TCCGTAGGTGAACCTGCGG-3')/ITS4(5'-TCCTCCGCTTATTGATATGC-3') and sequenced. The resulting 606-bp sequence was deposited in GenBank (KC430919). The sequence showed 100% identity with sequences of C. gloeosporioides (e.g., JX669446, JQ936316, JQ753973). To confirm pathogenicity, inoculum was prepared by harvesting conidia from 3-week-old cultures on potato dextrose agar. A conidial suspension (3 × 105 conidia/ml) was sprayed onto 10 fruits wounded with a fine needle. Ten fruits sprayed with sterile water served as controls. Fruits were placed in moist chambers for 24 h and then kept in plastic containers (25°C and 60 to 80% RH). After 5 days, fruit rot symptoms, identical to those observed in the field, developed on the inoculated fruits, but never on controls. C. gloeosporioides was reisolated from the lesions of inoculated fruits. Anthracnose associated with C. gloeosporioides on common figs has been known from North America, Central America, South America, Australia, New Zealand, South Africa, and Turkey (1). In Korea, anthracnose fruit rot of common figs was recorded in 1928 under the name C. caricae F. Stevens & J.G. Hall, but without fulfillment of Koch's postulates (3). Subsequent to that time, there has been no published finding of the disease in Korea. C. caricae is regarded as synonymous with C. gloeosporioides (4). To our knowledge, this is the first confirmed report of anthracnose fruit rot of common figs caused by C. gloeosporioides in Korea. Anthracnose fruit rot of common figs may cause losses not only for fruit production but also for marketing.

First Report of Zonate Leaf Spot Caused by Hinomyces moricola on Japanese Hop in Korea.

Japanese hop (Humulus japonicus Siebold & Zucc. = H. scandens (Lour.) Merr.), native to East Asia, is an annual, climbing or trailing vine. The vines can spread to cover large areas of open ground or low vegetation, eventually blanketing the land and vegetation. Pollen of H. japonicus is allergenic, and this species is considered as one of the important causes of pollinosis in Korea and China. It is a notorious invasive weed in the United States and also in France, Hungary, and Italy (1). In September 2012, zonate leaf spots were observed on Japanese hops growing in wetlands in Yeongdong County of Korea. A voucher specimen was preserved in the Korea University Herbarium (KUS-F26901). Initial symptoms included grayish-green to grayish-brown spots without border lines. As the lesions enlarged, they coalesced, leading to leaf blight. Sporophores on the leaf lesions were dominantly hypophyllous, rarely epiphyllous, solitary, erect, easily detachable, and as long as 700 μm. The upper portion of the sporophores consisted of a pyramidal head was ventricose, 320 to 520 μm long and 110 to 150 μm wide. The fungus was isolated from leaf lesions and maintained on potato dextrose agar (PDA). Sclerotia were produced on PDA after 4 to 5 weeks at 18°C without light, but conidia were not observed in culture. These morphological and cultural characteristics were consistent with those of Hinomyces moricola (I. Hino) Narumi-Saito & Y. Harada (= Cristulariella moricola (I. Hino) Redhead) (3,4). An isolate was preserved in the Korean Agricultural Culture Collection (Accession No. KACC46955). Genomic DNA was extracted using the DNeasy Plant Mini DNA Extraction Kit (Qiagen Inc., Valencia, CA). The complete internal transcribed spacer (ITS) region of rDNA was amplified with the primers ITS1/ITS4 and sequenced. The resulting sequence of 452 bp was deposited in GenBank (Accession No. KC460209). A BLAST search in GenBank revealed that the sequence showed an exact match with those of C. moricola (JQ036181 ex Acer negundo and JQ036182 ex Glycine max). To determine the pathogenicity of the fungus, according to the procedure of Cho et al. (2), sporophores with the pyramidal head were carefully detached from a lesion on the naturally infected leaf using a needle. Each sporophore was transferred individually onto five places of four detached healthy leaves. The leaves were placed in dew chambers and incubated at 16°C. Symptoms were observed after 2 days on all inoculated leaves. A number of sporophores and immature sclerotia which were morphologically identical to the ones observed in the field were formed on the abaxial surface of the leaf 2 weeks after inoculation. The pathogen was reisolated from lesions on the inoculated leaves, confirming Koch's postulates. No symptoms were observed on the control leaves kept in humid chambers for 2 weeks. H. moricola was known to cause zonate leaf spots and defoliation on a wide range of woody and annual plants (3). To the best of our knowledge, this is the first report of Hinomyces infection on Japanese hops in Korea.

First Report of Sclerotinia Stem Rot of Anemone Caused by Sclerotinia sclerotiorum in Korea.

In Korea, anemones (Anemone coronaria L.) are mostly grown during winter, in polyethylene tunnels that may have high humidity and poor ventilation, to meet the high demand of cut flowers in February and March for school ceremonies. During the winter of 2011 to 2012, symptoms typical of Sclerotinia stem rot were observed in commercial crops of anemone (cv. Rosso Mistral Plus) in Hwaseong City, Korea. About 40% of anemones withered or died before harvest due to the disease, causing considerable economic losses. In one farmer's polyethylene tunnel with a good ventilation system in Icheon City, Korea, less than 1% of the anemones showed Sclerotinia stem rot during the same season. Symptoms included stem necrosis and withering of leaves, followed by crown rot and wilt a few days afterward. White cottony growth of the fungus was observed on dead plants and the nearby soil surface, especially under high relative humidity. Black sclerotia 2 to 7 mm in diameter developed in the mycelium. Isolations from surface-disinfested stem pieces onto potato dextrose agar (PDA) consistently yielded white, fluffy colonies. Two-week-old colonies produced plentiful numbers of sclerotia on PDA. The isolated fungus was morphologically identified as Sclerotinia sclerotiorum (Lib.) de Bary (1,3). Voucher specimens (n = 4) were deposited in the Korea University herbarium (KUS). Two isolates were deposited in the Korean Agricultural Culture Collection with accession numbers KACC46708 (ex KUS-F26433) and KACC46834 (ex KUS-F26437), respectively. Fungal DNA was extracted with a DNeasy Plant Mini DNA Extraction Kit (Qiagen Inc., Valencia, CA). The complete internal transcribed spacer (ITS) region of rDNA was amplified with the primers ITS1/ITS4 (4) and sequenced using an ABI Prism 337 automatic DNA sequencer (Applied Biosystems, Foster, CA). The resulting sequences of 501 bp were deposited in GenBank (Accession Nos. KC412065 and KC412066). A BLAST search revealed that sequences of the two Korean isolates showed 100% identity with those of S. sclerotiorum (e.g., GenBank Accession No. JN012606). A pathogenicity test was achieved by placing agar segments (9 mm2) from a 7-day-old culture grown on PDA on the stems of healthy anemones (cv. Rosso Mistral Plus) near the soil line. Three plants inoculated with agar blocks served as controls. Plants were maintained in a greenhouse at 16 to 20°C and relative humidity >90%. After 2 days, all inoculated stems became discolored, soft, watery, and covered with white mycelia, whereas control plants remained symptomless. S. sclerotiorum was consistently reisolated from the symptomatic tissue, fulfilling Koch's postulates. Sclerotinia stem rot of anemones caused by S. sclerotiorum has previously been recorded from the United States and New Zealand (2), and to our knowledge, this is the first report of S. sclerotiorum on anemone in Korea. According to our observations in damaged plots, low temperature, high humidity, poor ventilation, and continuous cultivation would accelerate the incidence of Sclerotinia stem rot in polyethylene tunnel cultivation systems in Korea.

First Report of Leaf Spot Caused by Corynespora cassiicola on Rose of Sharon in Korea.

Rose of Sharon, Hibiscus syriacus L., is a flowering shrub in the family Malvaceae planted as the national flower of South Korea. In September 2012, previously unknown leaf spots with premature defoliation were observed on dozens of Rose of Sharon plants growing in the shaded area in a park of Dongducheon, Korea. The same symptoms were found on Rose of Sharon in several localities of Korea in 2012. The symptoms usually started as small, dark brown to grayish leaf spots, eventually causing leaf yellowing with significant premature defoliation. The diseased leaves retained for a while green color at the margin of the spots. Representative samples (n = 5) were deposited in the Korea University Herbarium (KUS). Conidiophores of the fungus observed microscopically on the leaf spots were erect, brown to dark brown, single or in clusters, amphigenous but mostly hypophyllous, and measured 80 to 400 × 5 to 10 μm. Conidia were borne singly or in short chains, ranging from cylindrical to broadest at the base and tapering apically, straight to slightly curved, pale olivaceous brown, 2 to 16 pseudoseptate, 50 to 260 × 9 to 20 μm, each with a conspicuous thickened hilum. On potato dextrose agar, single-spore cultures of two isolates were identified as Corynespora cassiicola (Berk. & M.A. Curtis) C.T. Wei on the basis of morphological and cultural characteristics (1,2). Two monoconidial isolates were preserved at the Korean Agricultural Culture Collection (KACC46956 and KACC46957). Genomic DNA was extracted using the DNeasy Plant Mini DNA Extraction Kit (Qiagen Inc., Valencia, CA). The complete internal transcribed spacer (ITS) region of rDNA was amplified with the primers ITS1/ITS4 and sequenced. The resulting sequences of 520 bp were deposited in GenBank (Accession Nos. KC193256, KC193257). A BLAST search in GenBank revealed that the sequences showed 100% identity with those of numerous C. cassiicola isolates from diverse substrates. To conduct a pathogenicity test, a conidial suspension (ca. 2 × 104 conidia/ml) was prepared in sterile water by harvesting conidia from 2-week-old cultures of KACC46956, and the suspension was sprayed onto the leaves of three healthy 2-year-old plants. Inoculated plants were kept in humid chambers for the first 48 h and thereafter placed in the glasshouse. After 10 days, typical leaf spot symptoms developed on the leaves of all three inoculated plants. C. cassiicola was reisolated from the lesions, confirming Koch's postulates. Control plants treated with sterile water remained symptomless. C. cassiicola is cosmopolitan with a very wide host range (1,2). Though Corynespora hibisci Goto was recorded to be associated with brown spot disease of H. syriacus in Japan (4), there is no previous record of C. cassiicola on H. syriacus (3). To our knowledge, this is the first report of Corynespora leaf spot on Rose of Sharon in Korea. According to our field observations in Korea, this disease was found in August and September, following a prolonged period of moist weather. Severe infection resulted in leaf yellowing and premature defoliation, reducing tree vigor and detracting the beauty of green leaves.

First Report of Black Stem Caused by Botryosporium longibrachiatum on Sweet Basil in Korea.

Sweet basil, Ocimum basilicum L., is cultivated mainly for fresh consumption in Korea. In March 2009, in Icheon, Korea, several dozen plants showing symptoms of black stems were found in an organic farm that used polyethylene tunnels for production. The black stems were usually covered with a fungus that gave the appearance of hoar-frost on the stems, especially when plants were grown under a cool and humid environment. According to the farmer, black stems appear during the winter season of November to March when the tunnels were mostly closed. The relative humidity (RH) during that period was around 100% every night due to poor ventilation. Beginning the middle of April when both sides of the tunnels were open, providing good ventilation, no further disease development was observed. The fungus on the stems had an elongate, upright conidiophore, reaching 5 mm in length. At intervals along its length, the main axis of conidiophores produced lateral fertile branches in acropetal succession. Each lateral branch terminated in a cluster of four or five ampullae. Conidia were hyaline, oval, and 5.5 to 9.5 × 3.5 to 6 μm. The fungus was non-pigmented and colonies on potato dextrose agar were chalk white. Morphological and cultural characteristics of the fungus were consistent with the previous reports of Botryosporium longibrachiatum (Oudem.) Maire (3,4). Voucher specimens (n = 4) were housed at Korea University Herbarium (KUS). An isolate from KUS-F24010 was deposited in the Korean Agricultural Culture Collection (Accession No. KACC44849) and used for molecular analysis and pathogenicity tests. The complete internal transcribed spacer (ITS) region of rDNA was amplified with the primers ITS1/ITS4 and sequenced. The resulting sequence of 592 bp was deposited in GenBank (Accession No. JX666334). A BLAST search in GenBank showed that there was no comparable sequence of B. longibrachiatum and thus this was the first ITS sequence for the species submitted in GenBank. To confirm the pathogenicity, colonized mycelial plugs (3 mm in diameter) from 10-day-old PDA cultures were placed onto the stem apices (n = 10) of 2-month-old sweet basil pot plants, which were topped as normally harvested. Control plants were inoculated with uncolonized agar plugs. All plants were incubated at 22 ± 2°C in a humidified chamber with a 12-h photoperiod for 48 h, and then maintained in a greenhouse (22 ± 2°C). Three to four days after inoculation, necrotic lesions developed around the points of inoculation on all stems and expanded downwards, leading to black stems covered with the hoar-frost like fungus after 14 days. B. longibrachiatum was successfully reisolated from all inoculated stems, while control plants remained symptomless. The pathogenicity test was conducted twice with the same result. The association of B. longibrachiatum and sweet basil was previously reported (4). Several other plants including burley tobacco are also reported to be infected by this fungus (1,2). To our knowledge, this is the first etiological report of B. longibrachiatum on sweet basil globally as well as in Korea.

First Confirmed Report of Cercospora Blight of Asparagus Caused by Cercospora asparagi in Korea.

In September 2011, hundreds of asparagus (Asparagus officinalis L.) showing symptoms of blight with nearly 100% incidence (percentage of plants affected) were found in polyethylene tunnels at an organic farm in Gangneung City of Korea. Lesions on needles and branches of the ferns were small, elliptic to subcircular, pale tan to brown with reddish brown borders, and became gray and cottony due to heavy sporulation under continuous high humidity. Infection caused premature defoliation and weakened plant vigor. The damage purportedly due to this disease has reappeared with confirmation of the causal agent made again in 2012. A cercosporoid fungus was consistently associated with disease symptoms. Stromata were well developed, consisting of brown cells, and were 10 to 30 μm wide. Conidiophores were fasciculate (n = 2 to 12), olivaceous brown, paler upwards, straight to mildly curved, not geniculate in shorter ones, or 1 to 2 times geniculate in longer ones, 40 to 260 μm long, 3.5 to 5.5 μm wide, and 1- to 6-septate. Conidia were hyaline, cylindric to acicular, straight in shorter ones, curved in longer ones, truncate to obconically truncate at the base with darkened hila, guttulate, 2- to 12-septate, and 40 to 220 × 3 to 5 μm. Morphological characteristics of the fungus were consistent with the previous reports of Cercospora asparagi Sacc. (1). Voucher specimens were housed at the Korea University herbarium (KUS). An isolate from KUS-F26046 was deposited in the Korean Agricultural Culture Collection (Accession No. KACC46400). The complete internal transcribed spacer (ITS) region of rDNA was amplified with the primers ITS1/ITS4 and sequenced. The resulting sequence of 497 bp was deposited in GenBank (Accession No. JX964995). This showed >99% similarity with sequences of many Cercospora species, indicating their close phylogenetic relationship. For pathogenicity tests, conidial suspensions (105 conidia/ml) were prepared by culturing the fungus on V8 juice agar (2) for 3 weeks. Five plants were inoculated with conidial suspensions and five plants were sprayed with sterile distilled water. The plants were covered with plastic bags to maintain 100% RH for 24 h and then transferred to a greenhouse. Typical symptoms of necrotic lesions appeared on the inoculated plants 6 days after treatment, and were identical to the ones observed in the field. C. asparagi was reisolated from symptomatic tissues, confirming Koch's postulates. No symptoms were observed on control plants. The disease has been reported through the regions of the world where asparagus is grown (3). In Korea, the disease was recorded in 1928 by Japanese workers under Cercosporina asparagicola Speg. (regarded as synonymous with Cercospora asparagi) with brief notes (4). Though one sample of asparagus was sent to the author (KSH) for diagnosis in 2009 summer and determined to be infected with C. asparagi (unpublished data), there has been no additional finding of the disease in Korea for the last 82 years. To our knowledge, this is the first confirmed report of Cercospora blight of asparagus caused by C. asparagi in Korea.

First Report of Leaf Spot Caused by Pseudocercospora subsessilis on Melia azedarach in Korea.

Melia azedarach L., called chinaberry, is native to Southeast Asia and Australia. The trees are commonly planted as ornamentals in the southern part of Korea. In October 2010, a leaf spot disease was observed on trees for the first time in Wando, Korea. Further surveys conducted from 2010 to 2012 showed that the disease occurs on trees in Jeju, Seogwipo, and Tongyeong cities as well as Wando county with nearly 100% incidence. Leaf spots were circular to semicircular, later becoming angular, small, pale brown in the center with a dark brown margin, and later becoming milky white. Leaf spots sometimes coalesced to blight the entire leaf and were capable of rapidly defoliating whole trees in late September. Fruiting was amphigenous, but mostly hypogenous. Stromata were substomatal, globular, dark brown, and 25 to 70 μm in diameter. Conidiophores were densely fasciculate, pale olivaceous to pale brown, substraight to mildly curved, not geniculate, 10 to 30 μm long, 2.5 to 4.5 μm wide, and aseptate or uniseptate. Conidia were pale olivaceous, generally darker than conidiophores, cylindric to obclavate, substraight in shorter ones, curved to mildly sinuous in longer ones, obconically truncate at the base, obtuse at the apex, 2- to 14-septate, 16 to 120 × 3 to 5 μm, guttulate, and had inconspicuous hila. Morphological characteristics of the fungus were consistent with the previous descriptions of Pseudocercospora subsessilis (Syd. & P. Syd.) Deighton (2). Voucher specimens (n = 6) were deposited in the Korea University Herbarium (KUS). An isolate from KUS-F25395 was deposited in the Korean Agricultural Culture Collection (KACC45688). The complete internal transcribed spacer (ITS) region of rDNA was amplified with the primers ITS1/ITS4 (3) and sequenced. The resulting sequence of 517 bp was deposited in GenBank (Accession No. JX993904). A BLAST search in GenBank revealed that the sequence shows >99% similarity (1 bp substitution) with a sequence of P. subsessilis ex M. azedarach from Cuba (GU269815). For pathogenicity tests, hyphal suspensions were prepared by grinding 3-week-old colonies grown on potato dextrose agar with distilled water using a mortar and pestle. Five 3-year-old chinaberry trees were inoculated with hyphal suspensions using a fine haired paint brush. Three healthy trees of the same age, serving as controls, were sprayed with sterile water. The plants were covered with plastic bags to maintain 100% relative humidity for 24 h and then transferred to a greenhouse. Typical symptoms of necrotic spots that appeared on the inoculated leaves 10 days after inoculation were identical to the ones observed in the field. P. subsessilis was reisolated from symptomatic leaf tissues, confirming Koch's postulates. No symptoms were observed on control plants. The disease has been reported in several Asian countries as well as in Cuba and the United States (1). To our knowledge, this is the first report of leaf spot on chinaberry caused by P. subsessilis in Korea. The observed high incidence and severity suggest that this disease can be a limiting factor in utilizing this tree species as ornamentals in public areas.

First Report of Leaf Blight Caused by Septoria allii on Garlic Chives in Korea

Garlic chives, Allium tuberosum Roth., are widely cultivated in Asia and are the fourth most important Allium crop in Korea. In June 2011, a leaf blight of garlic chives associated with a Septoria spp. was observed on an organic farm in Hongcheon County, Korea. Similar symptoms were also found in fields within Samcheok City and Yangku County of Korea during the 2011 and 2012 seasons. Disease incidence (percentage of plants affected) was 5 to 10% in organic farms surveyed. Diseased voucher specimens (n = 5) were deposited at the Korea University Herbarium (KUS). The disease first appeared as yellowish specks on leaves, expanding to cause a leaf tip dieback. Half of the leaves may be diseased within a week, especially during wet weather. Pycnidia were directly observed in leaf lesions. Pycnidia were amphigenous, but mostly epigenous, scattered, dark brown to rusty brown, globose, embedded in host tissue or partly erumpent, separate, unilocular, 50 to 150 μm in diameter, with ostioles of 20 to 40 μm in diameter. Conidia were acicular, straight to sub-straight, truncate at the base, obtuse at the apex, hyaline, aguttulate, 22 to 44 × 1.8 to 3 μm, mostly 3-septate, occasionally 1- or 2-septate. These morphological characteristics matched those of Septoria allii Moesz, which is differentiated from S. alliacea on conidial dimensions (50 to 60 μm long) (1,2). A monoconidial isolate was cultured on potato dextrose agar (PDA). Two isolates have been deposited in the Korean Agricultural Culture Collection (Accession Nos. KACC46119 and 46688). Genomic DNA was extracted using the DNeasy Plant Mini DNA Extraction Kit (Qiagen Inc., Valencia, CA). The internal transcribed spacer (ITS) region of rDNA was amplified using the ITS1/ITS4 primers and sequenced. The resulting sequence of 482-bp was deposited in GenBank (JX531648 and JX531649). ITS sequence information was at least 99% similar to those of many Septoria species, however no information was available for S. allii. Pathogenicity was tested by spraying leaves of three potted young plants with a conidial suspension (2 × 105 conidia/ml), which was harvested from a 4-week-old culture on PDA. Control leaves were sprayed with sterile water. The plants were placed in humid chambers (relative humidity 100%) for the first 48 h. After 7 days, typical leaf blight symptoms started to develop on the leaves of inoculated plants. S. allii was reisolated from the lesions of inoculated plants, confirming Koch's postulates. No symptoms were observed on control plants. The host-parasite association of A. tuberosum and S. allii has been known only from China (1). S. alliacea has been recorded on several species of Allium, e.g. A. cepa, A. chinense, A. fistulosum, and A. tuberosum from Japan (4) and A. cepa from Korea (3). To the best of our knowledge, this is the first report of S. allii on garlic chives. No diseased plants were observed in commercial fields of garlic chives which involved regular application of fungicides. The disease therefore seems to be limited to organic garlic chive production.

First Report of Frosty Mildew Caused by Mycopappus alni on Asian Pear in Korea.

Asian pear (Pyrus pyrifolia Nakai), also known as Japanese or Korean pear, is widely cultivated in East Asia. On September 2011, irregularly shaped necrotic lesions were observed on leaves of cv. Shinheung growing in an orchard in Gangneung City, Korea. At 40× magnification under a microscope, the white to cream colored propagules were epiphyllous, conical, scattered to aggregated, and composed of stroma-like bases, globose to subglobose, 55 to 100 μm wide and 35 to 75 μm high with filamentous and claviform hyphae. The filamentous hyphae were cylindrical, 125 to 425 × 3.5 to 6 μm, 2- to 8-septate, and obtuse to subobtuse at the apex. The claviform hyphae were clavate to cylindrical, 35 to 125 × 5 to 12.5 μm, aseptate to 3-septate, and obtuse at the apex. The fungus was isolated from leaf lesions and cultured on potato dextrose agar (PDA). The colonies consisted of thin mycelia colored whitish at first and then pale brown on PDA. Sclerotia were produced on PDA after 2 weeks incubation at 15°C, but conidia were not observed in culture. An isolate from KUS-F26196 was deposited in the Korean Agricultural Culture Collection (Accession No. 25 KACC46693). These morphological and cultural characteristics were consistent with Mycopappus alni (Dearn. & Barthol.) Redhead & G.P. White (1,3,4). Fungal DNA was extracted with DNeasy Plant Mini DNA Extraction Kits (Qiagen Inc., Valencia, CA). The complete internal transcribed spacer (ITS) region of rDNA was amplified with the primers ITS1/ITS4 and sequenced. The resulting sequence product of 520 bp was deposited in GenBank (Accession No. JX458815). A BLAST search in GenBank revealed that the sequence was 99% similar to M. alni (AB254190, AB254177, AB254189). To determine the pathogenicity of the fungus, propagules were detached from lesions on the naturally infected leaves using fine needles. Each propagule was transferred individually onto five places of six detached healthy leaves. Control treatment comprised placing small agar blocks onto five places of six detached healthy leaves. The plants were incubated in a humid chamber at RH 100% and 18°C. Symptoms were observed after 2 days on all inoculated leaves. The pathogen was reisolated from lesions on the inoculated leaves, confirming Koch's postulates. No symptoms were observed on control leaves. The fungus has been associated with frosty mildew on Alnus spp., Betula spp., Crataegus spp., and Pyrus spp. in North America, Turkey, Russia, and Japan (1,2,4). To our knowledge, this is the first report of frosty mildew on P. pyrifolia caused by M. alni globally as well as in Korea. Since the infections may be limited to the mountainous area with low night temperature and high humidity, economic losses seem to be negligible. However, the disease could be a potential threat to the safe production of Korean pears in case of prolonged period of cool and moist weather.

고추 역병균의 접종원에 따른 역병 저항성의 유전 양식

본 연구는 국내 고추 주산지의 P. capsici의 균주에 대한 병원성과 균주별 역병 저항성 유전 양식을 구명하고자 수행하였다. 이병성 재료 '#308'과 역병 저항성 재료 'CM334' 및 이들의 <TEX>$F_1$</TEX>, <TEX>$F_2$</TEX> 그리고 'Kataguma'(Sakata Korea) 고추 총 5종의 공시 재료에 이천, 음성, 부안, 임실, 영양 지역에서 수집한 P. capsici 각각의 균주와 국립농업유전자원센터에서 분양받은 PA-159(KACC No. 40482)를 포함하여 총 6종의 고추 P. capsici 균주를 사용하여 접종하였다. 접종 농도는 <TEX>$1{\times}10^5spores/ml$</TEX>로 관주 접종하였고 이들의 기내 특성, 이병률, <TEX>$F_2$</TEX> 후대 집단의 역병저항성 분리 기대비를 분석하였다. 이병성 재료 '#308'과 저항성 'CM334', <TEX>$F_1$</TEX>의 비분리세대는 균주별 군내 비교에서는 각각 고추 역병의 발병도는 4.94-5.00, 1.00-1.07, 1.01-1.08을 보여 P. capsici 균주별 군내 비교에서 공시재료간 역병 저항성 차이는 명확히 구분할 수 있다. 또한 <TEX>$F_2$</TEX> 분리세대의 역병 발병도의 경향은 1.79-2.31을 보여 P. capsici 군내 비교의 차이가 없고 저항성과 이병성 재료간에 유의한 차이를 보여 본 연구에서 사용된 6종의 P. capsici 균주 모두 역병 저항성 검정을 위한 균주로 활용 가능한 것으로 나타났다. 하지만 <TEX>$F_2$</TEX> 분리세대의 균주별 군간 비교에서 PA-159 균주를 중심으로 이천 균주, 부안 균주, 임실 균주가 포함된 집단과 이보다 높은 병원성을 지닌 영양 균주와 음성 균주로 구분되었다. 각 균주별 <TEX>$F_2$</TEX> 세대의 역병 저항성에 대한 분리 기대비를 분석하였는데, PA-159 균주는 3:1 또는 9:3:3:1의 분리비를 보여 1-2개의 유전자가 관여하는 것으로 나타났다. 반면 음성 균주와 영양 균주는 11:5, 이천 균주는 12:3:1의 분리비를 보여 유전자간 상호작용이 있는 것으로 나타났다. 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 <TEX>$F_1$</TEX> and <TEX>$F_2$</TEX>, 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 <TEX>$F_1$</TEX> 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, <TEX>$F_2$</TEX> 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 <TEX>$F_2$</TEX> 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 <TEX>$F_2$</TEX> 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.

First Report of Leaf Spot Caused by Septoria erigerontis on Erigeron strigosus in Korea.

Erigeron strigosus Muhl. ex Willd., known as daisy fleabane, is native to North America and was accidently introduced to Korea in the 1990s (2). It is increasingly invasive in natural and managed ecosystems throughout Korea. In June 2011, a leaf spot was first observed on daisy fleabanes growing wild in Hongcheon County of Korea. A voucher specimen was deposited in the Korea University Herbarium (KUS-F25759). Symptoms developed on lower leaves as small, distinct, reddish brown lesions, which enlarged progressively and turned into pale, dull brown spots surrounded by dark purplish-brown margins. Black pycnidia became visible in the lesions. Pycnidia were epigenous, occasionally hypogenous, scattered, dark brown to rusty brown, globose, embedded in host tissue or partly erumpent, 60 to 160 μm in diameter, with ostioles measuring 10 to 30 μm in diameter. Conidia were straight to mildly curved or even flexuous, guttulate, hyaline, 30 to 75 × 1.5 to 2 μm, and one- to seven-septate. Based on the morphological characteristics, the fungus was consistent with Septoria erigerontis Peck (3,4). Conidia were harvested from cirrhi of pycnidia on leaf lesions with a drop of sterile water and then directly streaked onto water agar media using a bacterial loop. Isolates were incubated at 24°C for 48 h. Germinating conidia were individually transferred to potato dextrose agar (PDA) plates. An isolate was deposited in the Korean Agricultural Culture Collection (Accession No. KACC46120). Genomic DNA was extracted using the DNeasy Plant Mini DNA Extraction Kit (Qiagen Inc., Valencia, CA). The internal transcribed spacer (ITS) region of rDNA was amplified using the ITS1/ITS4 primers and sequenced. The resulting sequence of 505 bp was deposited in GenBank (Accession No. JX480493). A GenBank BLAST search was conducted with the 505-bp sequence showing 100% identity with the sequences of S. erigerontis ex Erigeron annuus (EF535638, GU269862). Pathogenicity was tested by spraying leaves of three potted plants with a conidial suspension (2 × 105 conidia/ml) harvested from a 4-week-old PDA culture. Control leaves were sprayed with sterile distilled water. The plants were placed in a dew chamber at 26°C in darkness and continuous dew for the first 24 h and then moved to a greenhouse bench. After 7 days, leaf spot symptoms identical to those observed in the field developed on the leaves inoculated with the fungus. No symptoms were observed on control plants. S. erigerontis was reisolated from the lesions of inoculated plants, fulfilling Koch's postulates. A leaf spot disease of E. strigosus associated with S. erigerontis has been reported in the United States and Canada (1). To our knowledge, this is the first report of leaf spot on E. strigosus caused by S. erigerontis outside of North America as well as in Korea.

First Report of Leaf Blight Caused by Phomopsis ipomoeae-batatas on Sweet Potato in Korea.

Ipomoea batatas (L.) Lam., belonging to the Convolvulaceae, is widely cultivated and used as an industrial resource as well as for food and feed worldwide (2). In September 2010, an unknown leaf blight was observed on leaves in Hoengseong County and Jecheon City in Korea. Symptoms were mostly observed in older leaves as cream to tan-brown lesions surrounded by purplish brown-to-dark brown margin. Each lesion was circular to irregular, not exceeding 10 mm, but coalesced to form larger lesions. Necrotic tissue fell out giving rise to shot-holes. A number of black pycnidia were present in the lesions of diseased leaves. The same symptoms were observed at several localities in Korea during 2010 and 2011 seasons. The voucher specimens (n = 5) were preserved in the Korea University Herbarium (KUS). Two isolates were obtained from the two samples (KUS-F25274 and KUS-F25361) and deposited in the Korean Agricultural Culture Collection (Accession Nos. KACC45680 and KACC45702). Pycnidia were amphigenous, but mostly epigenous, scattered, dark brown-to-rusty brown, globose, embedded in host tissue or partly erumpent, 110 to 170 μm in diameter, and with an ostiole of 25 to 40 μm in diameter. Alpha conidia were aseptate, lageniform, biguttulate, hyaline, and 5.5 to 8.0 × 3.5 to 4.5 μm. Beta conidia were absent. Based on the morphological characteristics, the fungus was consistent with Phomopsis ipomoeae-batatas Punith. (1,3). Preliminary identification of the fungal isolate was confirmed by molecular data. Genomic DNA was extracted from the two isolates. The D1/D2 region of 28S rDNA was amplified using the primers LROR and LR7, and sequenced. The resulting sequences of the two isolates were identical to each other, and were deposited in GenBank (Accession Nos. JX157848 and JX157849). A BLAST search showed that there was no matching sequence of P. ipomoeae-batatas. Therefore, these were the first 28S sequences for the species submitted to GenBank. The present sequences showed >98% similarity with 24 entries of Phomopsis spp. and Diaporthe spp. (teleomorph of Phomopsis spp.), indicating their close phylogenetic relationship. Pathogenicity was tested by spraying leaves of three potted plants with a conidial suspension (2 × 106 conidia/ml), which was harvested from a 3-week-old culture on potato dextrose agar. Control leaves were sprayed with sterile water. The plants were placed in a dew chamber at 24°C in darkness and continuous dew for the first 24 h and then moved to a greenhouse bench. After 10 days, leaf blight symptoms that were identical to those observed in the field started to develop on the leaves inoculated with the fungus. No symptoms were observed on control plants. P. ipomoeae-batatas was reisolated from the lesions of inoculated plants, confirming Koch's postulates. Occurrence of leaf blight caused by P. ipomoeae-batatas on sweet potato has been reported in many countries (1,3). To our knowledge, this is the first report of the disease in Korea. The economic losses are of minor importance, because the disease is mostly present toward the end of growing season; however, attention must be paid considering that the pathogen may reduce the quality of vines used as fodder.

First Report of Leaf Spot of Sweet Basil Caused by Cercospora guatemalensis in Korea.

Sweet basil, Ocimum basilicum L., is a fragrant herb belonging to the family Lamiaceae. Originated in India 5,000 years ago, sweet basil plays a significant role in diverse cuisines across the world, especially in Asian and Italian cooking. In October 2008, hundreds of plants showing symptoms of leaf spot with nearly 100% incidence were found in polyethylene tunnels at an organic farm in Icheon, Korea. Leaf spots were circular to subcircular, water-soaked, dark brown with grayish center, and reached 10 mm or more in diameter. Diseased leaves defoliated prematurely. The damage purportedly due to this disease has reappeared every year with confirmation of the causal agent made again in 2011. A cercosporoid fungus was consistently associated with disease symptoms. Stromata were brown, consisting of brown cells, and 10 to 40 μm in width. Conidiophores were fasciculate (n = 2 to 10), olivaceous brown, paler upwards, straight to mildly curved, not geniculate in shorter ones or one to two times geniculate in longer ones, 40 to 200 μm long, occasionally reaching up to 350 μm long, 3.5 to 6 μm wide, and two- to six-septate. Conidia were hyaline, acicular to cylindric, straight in shorter ones, flexuous to curved in longer ones, truncate to obconically truncate at the base, three- to 16-septate, and 50 to 300 × 3.5 to 4.5 μm. Morphological characteristics of the fungus were consistent with the previous reports of Cercospora guatemalensis A.S. Mull. & Chupp (1,3). Voucher specimens were housed at Korea University herbarium (KUS). An isolate from KUS-F23757 was deposited in the Korean Agricultural Culture Collection (Accession No. KACC43980). Fungal DNA was extracted with DNeasy Plant Mini DNA Extraction Kits (Qiagen Inc., Valencia, CA). The complete internal transcribed spacer (ITS) region of rDNA was amplified with the primers ITS1/ITS4 and sequenced. The resulting sequence of 548 bp was deposited in GenBank (Accession No. JQ995781). This showed >99% similarity with sequences of many Cercospora species, indicating their close phylogenetic relationship. Isolate of KACC43980 was used in the pathogenicity tests. Hyphal suspensions were prepared by grinding 3-week-old colonies grown on PDA with distilled water using a mortar and pestle. Five plants were inoculated with hyphal suspensions and five plants were sprayed with sterile distilled water. The plants were covered with plastic bags to maintain a relative humidity of 100% for 24 h and then transferred to a 25 ± 2°C greenhouse with a 12-h photoperiod. Typical symptoms of necrotic spots appeared on the inoculated leaves 6 days after inoculation, and were identical to the ones observed in the field. C. guatemalensis was reisolated from symptomatic leaf tissues, confirming Koch's postulates. No symptoms were observed on control plants. Previously, the disease was reported in Malawi, India, China, and Japan (2,3), but not in Korea. To our knowledge, this is the first report of C. guatemalensis on sweet basil in Korea. Since farming of sweet basil has recently started on a commercial scale in Korea, the disease poses a serious threat to safe production of this herb, especially in organic farming.

칠레산 수입포도 '레드글로브' 품종에 발생한 부패병 병원균의 동정

Korean Agricultural Culture Collection, Agricultural Microbiology Division, National Academy of Agricultural Science, Suwon 441-707, Korea(Received on July 9, 2012; Revised on September 26, 2012; Accepted on September 26, 2012)Post-harvest rot of grape causes a severe economic loss and lower of the grape quality. It is also one of theimportant limiting factors for grape export. Grape rots and their casual agents on ‘Red Globe’ varietyimported from Chile were identified. Grapes shown rotting symptom were collected from the storages nearthe import harbor. The 3 different rots were identified on the imported ‘Red Globe’; melting decay, graymold, and blue mold. A bacterium that isolated from a typical melting decay symptom was identified asGluconobacter cerinus on basis of its nucleotide sequence of 16S rDNA and fatty acid profile. By inoculationon grape, it caused cracking and dissolution of epidermis of grape which were the characteristics of meltingdecay. Botrytis cinerea and Penicillium expansum were isolated from grapes showing gray mold and bluemold. The 2 fungal isolates were identified on basis of their morphological characteristics and nucleotidesequence of their beta-tubulin genes. They showed strong pathogenicity on ‘Campbell Early’ variety that is amajor table grape in Korea.Keywords : Blue mold, Botrytis cinerea, Gluconobacter cerinus, Gray mold, Penicillium expansum

First Report of Anthracnose of Tricyrtis macropoda Caused by Colletotrichum gloeosporioides in Korea.

Tricyrtis macropoda Miq. (syn. T. dilatata Nakai), known as speckled toadlily, is a perennial herb native to China, Japan, and Korea. The plant has been highly praised for its beautiful flowers and rare populations in natural habitats. In September 2006, several dozen plants were heavily damaged by leaf spots and blight in cultivated plantings in the city of Pocheon, Korea. The infections with the same symptoms were repeated every year. In July 2011, the same symptoms were found on T. macropoda in the cities of Gapyeong and Osan, Korea. The leaf lesions began as small, water-soaked, pale greenish to grayish spots, which enlarged to form concentric rings and ultimately coalesced. A number of blackish acervuli were formed in the lesions. Acervuli were mostly epiphyllous, circular to ellipsoid, and 40 to 200 μm in diameter. Setae were two- to three-septate, dark brown at the base, paler upwards, acicular, and up to 100 μm long. Conidia (n = 30) were long obclavate to oblong-elliptical, sometimes fusiform-elliptical, guttulate, hyaline, and 12 to 20 × 4 to 6.5 μm (mean 15.4 × 5.2 μm). These morphological characteristics of the fungus were consistent with the description of Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. (2). Voucher specimens (n = 7) were deposited in the Korea University herbarium (KUS). Two isolates, KACC46374 (ex KUS-F25916) and KACC46405 (ex KUS-F26063), were deposited in the Korean Agricultural Culture Collection. Fungal DNA was extracted and the complete internal transcribed spacer (ITS) region of rDNA was amplified with the primers ITS1/ITS4 and sequenced. The resulting sequences of 549 bp were deposited in Genbank (Accession Nos. JQ619480 and JQ619481). They showed 100% similarity with a sequence of C. gloeosporioides (EU32619). Isolate KACC46374 was used in a pathogenicity test. Inoculum was prepared by harvesting conidia from 3-week-old cultures on potato dextrose agar. A conidial suspension (2 × 106 conidia/ml) was sprayed onto 15 leaves of three plants. Three noninoculated plants served as controls. Plants were covered with plastic bags to maintain 100% relative humidity for 24 h and then kept in a greenhouse (22 to 28°C and 70 to 80% RH). After 5 days, typical leaf spot symptoms, identical to the ones observed in the field, started to develop on the leaves of inoculated plants. No symptoms were observed on control plants. C. gloeosporioides was reisolated from the lesions of inoculated plants, thus fulfilling Koch's postulates. An anthracnose associated with C. tricyrtii (Teng) Teng was recorded on T. formosana and T. latifolia in China (3) and on T. formosana in Taiwan (1), respectively, without etiological studies. The morphological features of C. tricyrtii are within the variation of C. gloeosporioides (2). To our knowledge, this is the first report of anthracnose of T. macropoda. This report has significance to indigenous plant resource conservation managers and scientists because T. macropoda has been listed as one of the 126 "Rare and Endangered Plants" by the Korea Forest Service since 1991.

First Report of Zonate Leaf Spot of Glycine max Caused by Cristulariella moricola in Korea.

Soybean (Glycine max (L.) Merr.) is native to East Asia including Korea and is widely grown and consumed as an edible seed. In August 2011, following a prolonged period of cool and moist weather, zonate leaf spots were observed in local soybean (cultivar unknown) planted in a mountainous area of Goseong, central Korea. A voucher specimen was collected and entered at the Korea University herbarium (KUS-F26049). Initial symptoms included grayish green-to-grayish brown spots without border lines. As the lesions enlarged, they coalesced, leading to leaf blight and premature defoliation. Sporophores on the leaf lesions were dominantly hypophyllous, rarely epiphyllous, solitary, erect, easily detachable, and as long as 750 μm. The upper portion of the sporophores consisted of a pyramidal head that was ventricose, 275 to 500 μm long, and 80 to 160 μm wide. The fungus was isolated from leaf lesions and maintained on potato dextrose agar (PDA). Sclerotia were produced on PDA after 4 to 5 weeks at 18°C without light, but conidia were not observed in culture. The morphological and cultural characteristics were consistent with those of Cristulariella moricola (Hino) Redhead (2,3). An isolate was preserved in the Korean Agricultural Culture Collection (KACC46401). Genomic DNA was extracted with the DNeasy Plant Mini DNA Extraction Kit (Qiagen Inc., Valencia, CA). The complete internal transcribed spacer (ITS) region of rDNA was amplified with the primers ITS1/ITS4 and sequenced. The resulting sequence of 453 bp was deposited in GenBank (Accession No. JQ036182). A BLAST search in GenBank revealed that the sequence showed an exact match with that of C. moricola from Acer negundo (JQ036181) and >99% similarity with that of Grovesinia pyramidalis, teleomorph of C. moricola from Juglans sp. (Z81433). To determine the pathogenicity of the fungus, sporophores with the pyramidal head were carefully detached from a lesion on the naturally infected leaflet with fine needles. Each sporophore was transferred individually onto four places of six detached healthy soybean leaflets. The leaflets were placed in humid chambers at 100% relative humidity and incubated at 16 to 20°C (4). Symptoms were observed after 2 days on all inoculated leaflets (one to four lesions/leaflet). The lesions enlarged rapidly and reached ~20 mm diameter in a week. A number of sporulating structures and immature sclerotia were formed on the abaxial surface of the leaf 2 weeks after inoculation. The pathogen was reisolated from lesions on the inoculated leaflets, confirming Koch's postulates. No symptoms were observed on the control leaflets kept in humid chambers for 2 weeks. C. moricola was known to cause zonate leaf spots and defoliation on a wide range of woody and annual plants (1), but not on G. max. To our knowledge, this is the first report of Cristulariella infection in cultivated soybeans. Since the infections may be limited to the mountainous area with low night temperature and high humidity, economic losses seem to be negligible. However, the disease could be a potential threat to the safe production of soybeans in areas with prolonged periods of cool and moist weather.

First Report of Brown Spot Needle Blight on Pinus thunbergii Caused by Lecanosticta acicola in Korea.

Pinus thunbergii Parl., known as black pine, is a pine native to coastal areas of Japan and Korea. Because of its resistance to pollution and salt, it is planted as windbreakers along the coast. In March 2010, needle blight symptoms were found on several trees of black pine in Naju, southern Korea. Further surveys in 2010 and 2011 showed that these symptoms are rather common but disease incidence is less than 1%. Small, circular grayish green spots first appeared on the needles. The spots developed into brown bands reaching 1 to 2 mm long, sometimes with yellow margins. Dark olivaceous to dark grayish stromata were erumpent and conspicuous on the brown lesions in the later stage of disease development. Conidiophores were simple or occasionally branched, 1- to 2-septate, pale brown to olivaceous brown, and smooth walled. Conidia (n = 30) were olivaceous brown to grayish brown, verrucose, thick-walled, mildly curved, allantoid to fusiform, one- to five-septate (mostly three-septate), and 20 to 45 × 3.5 to 5 μm. Morphological characteristics of the fungus were consistent with those of Lecanosticta acicola (Thüm.) Syd. (anamorph of Mycosphaerella dearnessii M.E. Barr), previously known as the causal agent of brown spot needle blight of pines (2,4). The teleomorph was not observed. On potato dextrose agar, single-spore cultures of three isolates were obtained from conidia sporulating on needles. An isolate was preserved at the Korean Agricultural Culture Collection (Accession No. KACC44982). Genomic DNA was extracted using the DNeasy Plant Mini DNA Extraction Kit (Qiagen Inc., Valencia, CA) and the complete internal transcribed spacer (ITS) region of rDNA was amplified and sequenced with the primers ITS1/ITS4. The resulting ITS sequence of 543 bp was deposited in GenBank (Accession No. JQ245448). A GenBank BLAST search produced an exact match for the sequences of M. dearnessii (= L. acicola) on P. mugo Tura from Lithuania (HM367708) and P. radiata D. Don from France (GU214663), with 100% sequence similarity. To conduct a pathogenicity test, a conidial suspension (approx. 2 × 105 conidia/ml) was prepared by harvesting conidia from 5-week-old cultures of KACC44982 and sprayed onto the needles of five 3-year-old healthy seedlings. Five noninoculated seedlings of the same age served as controls. Inoculated and noninoculated plants were kept in humid chambers for 48 h in a glasshouse. After 28 days, typical leaf spot symptoms started to develop on the needles of inoculated plants. The fungus, L. acicola, was reisolated from those lesions, confirming Koch's postulates. No symptoms were observed on control plants. The disease has been previously reported on several species of Pinus in the Americas (1) and recently in China (3), Japan (4), and Europe (2). To our knowledge, this is the first report of the Lecanosticta-Pinus association in Korea. Occurrence of the disease in Korea is a new threat to the health of black pine, especially in nursery plots.

First Report of Leaf Spot of Rudbeckia hirta var. pulcherrima Caused by Septoria rudbeckiae in Korea.

Rudbeckia hirta L. var. pulcherrima Farw. (synonym R. bicolor Nutt.), known as the black-eyed Susan, is a flowering plant belonging to the family Asteraceae. The plant is native to North America and was introduced to Korea for ornamental purposes in the 1950s. In July 2011, a previously unknown leaf spot was first observed on the plants in a public garden in Namyangju, Korea. Leaf spot symptoms developed from lower leaves as small, blackish brown lesions, which enlarged to 6 mm in diameter. In the later stages of disease development, each lesion was usually surrounded with a yellow halo, detracting from the beauty of the green leaves of the plant. A number of black pycnidia were present in diseased leaf tissue. Later, the disease was observed in several locations in Korea, including Pyeongchang, Hoengseong, and Yangpyeong. Voucher specimens were deposited at the Korea University Herbarium (KUS-F25894 and KUS-F26180). An isolate was obtained from KUS-F26180 and deposited at the Korean Agricultural Culture Collection (Accession No. KACC46694). Pycnidia were amphigenous, but mostly hypogenous, scattered, dark brown-to-rusty brown, globose, embedded in host tissue or partly erumpent, 50 to 80 μm in diameter, with ostioles 15 to 25 μm in diameter. Conidia were substraight to mildly curved, guttulate, hyaline, 25 to 50 × 1.5 to 2.5 μm, and one- to three-septate. Based on the morphological characteristics, the fungus was consistent with Septoria rudbeckiae Ellis & Halst. (1,3,4). Morphological identification of the fungus was confirmed by molecular data. Genomic DNA was extracted using the DNeasy Plant Mini DNA Extraction Kit (Qiagen Inc., Valencia, CA.). The internal transcribed spacer (ITS) region of rDNA was amplified using the ITS1/ITS4 primers and sequenced. The resulting sequence of 528 bp was deposited in GenBank (Accession No. JQ677043). A BLAST search showed that there was no matching sequence of S. rudbeckiae; therefore, this is the first ITS sequence of the species submitted to GenBank. The ITS sequence showed >99% similarity with those of many Septoria species, indicating their close phylogenetic relationship. Pathogenicity was tested by spraying leaves of three potted young plants with a conidial suspension (2 × 105 conidia/ml), which was harvested from a 4-week-old culture on potato dextrose agar. Control leaves were sprayed with sterile water. The plants were covered with plastic bags to maintain 100% relative humidity (RH) for the first 24 h. Plants were then maintained in a greenhouse (22 to 28°C and 70 to 80% RH). After 5 days, leaf spot symptoms identical to those observed in the field started to develop on the leaves inoculated with the fungus. No symptoms were observed on control plants. S. rudbeckiae was reisolated from the lesions of inoculated plants, confirming Koch's postulates. A leaf spot disease associated with S. rudbeckiae has been reported on several species of Rudbeckia in the United States, Romania, and Bulgaria (1-4). To our knowledge, this is the first report of leaf spot on R. hirta var. pulcherrima caused by S. rudbeckiae in Korea.

First Report of Corynespora Leaf Spot on Ailanthus altissima Caused by Corynespora cassiicola in Korea.

Ailanthus altissima (Mill.) Swingle, known as tree-of-heaven, is a deciduous tree belonging to the family Simaroubaceae, which is native to both northeast and central China and Taiwan. The trees often have the ability to replace indigenous plants and disrupt native ecosystems (3). In August 2010, a leaf spot disease was observed on young trees in Yangpyeong, Korea. Field observation in 2010 and 2011 showed that infections are common on 1- or 2-year-old trees. Adult trees were rarely infected. Symptoms usually started at the margin of leaves and expanded into irregular, dark brown leaf spots, eventually causing significant premature defoliation. Representative samples were deposited in the herbarium of Korea University (KUS-F25174 and -F25304). Conidiophores of fungi observed microscopically on the leaf spots were erect, brown to dark brown, single or occasionally in clusters, 80 to 550 × 5 to 8 μm, and mostly arose on the abaxial surface of symptomatic leaves. Conidia were borne singly or in short chains of two to four, ranging from cylindrical to broadest at the base and tapering apically, straight to slightly curved, pale olivaceous brown, 3 to 18 pseudoseptate, 70 to 450 × 8 to 22 μm, each with a conspicuous thickened hilum. On potato dextrose agar, single-spore cultures of five isolates were identified as Corynespora cassiicola (Berk. & M.A. Curtis) C.T. Wei on the basis of morphological and cultural characteristics (1,4). A monoconidial isolate was preserved at the Korean Agricultural Culture Collection (Accession No. KACC45510). Genomic DNA was extracted with the DNeasy Plant Mini DNA Extraction Kit (Qiagen Inc., Valencia, CA). The complete internal transcribed spacer (ITS) region of rDNA was amplified with the primers ITS1/ITS4 and sequenced with an ABI Prism 337 automatic DNA sequencer (Applied Biosystems, Foster, CA). The resulting sequence of 548 bp was deposited in GenBank (Accession No. JN974462). The sequence showed >99% similarity (1-bp substitution) with a sequence of C. cassiicola from Ipomoea batatas (GenBank Accession No. FJ852716). To conduct a pathogenicity test, a conidial suspension (~2 × 104 conidia/ml) was prepared by harvesting conidia from 2-week-old cultures of KACC45510 and the suspension sprayed onto the leaves of three healthy seedlings. Three noninoculated seedlings served as control plants. Inoculated and noninoculated plants were kept in humid chambers for 48 h in a glasshouse. After 5 days, typical leaf spot symptoms started to develop on the leaves of all three inoculated plants. C. cassiicola was reisolated from the lesions, confirming Koch's postulates. No symptoms were observed on control plants. C. cassiicola is cosmopolitan with a very wide host range (2). To our knowledge, C. cassiicola has not been reported on A. altissima anywhere in the world. According to field observations in Korea, Corynespora leaf spot was most severe in August and September, especially following a prolonged period of moist weather. C. cassiicola may be a potential biocontrol agent for this highly invasive tree species.

First Asian Report of Leaf Spot of Ambrosia trifida Caused by Septoria epambrosiae.

Ambrosia trifida L., known as giant ragweed, is native to North America and was introduced in Korea in the 1970s (4). It is now widely naturalized, and since 1999, has been designated as one of 11 most 'harmful nonindigenous plants' by the Korean Ministry of Environment because of its adverse effects on native plants. Various strategies to eradicate this noxious weed have been unsuccessful (4). In June 2008, leaf spot symptoms on this weed were found in Inje, Korea. Hundreds of giant ragweed growing along stream banks contained leaf spots with leaf yellowing and premature defoliation. Leaf lesions were 1 to 5 mm in diameter, angular to irregular, dark brown without a distinct margin, later becoming pallid with a brown margin. Between 2008 and 2011, the authors observed the same symptoms in Dongducheon, Yangku, Namyangju, and Pocheon, Korea. Voucher specimens have been housed in the herbarium of Korea University. Numerous black pycnidia were formed on the lesion. Pycnidia were amphigenous, globose, dark brown, ostiolate, and measured 80 to 130 μm in diameter. Conidia were filiform, straight to mildly curved, eguttulate, hyaline, 18 to 36 × 1.5 to 2.5 μm, one to three septate, subtruncate at the base, and tapering to a rounded apex. Single-conidial isolations onto potato dextrose agar formed dark grayish colonies. Pycnidia matured after 5 weeks when plates were incubated under fluorescent illumination for 12-h photoperiods at 25°C. On the basis of morphological and cultural characteristics, the fungus was identified as Septoria epambrosiae D.F. Farr (2). Three isolates were deposited in the Korean Agricultural Culture Collection (KACC). Preliminary morphological identification of the fungal isolates was confirmed by molecular data. The internal transcribed spacer (ITS) region of rDNA was amplified using the ITS1/ITS4 primers and sequenced. The resulting sequences of 449 bp obtained from the three isolates were identical to each other. They showed 100% similarity when compared with a sequence of S. epambrosiae (GenBank No. AF279582). The nucleotide sequence of a representative isolate (KACC43850) was deposited in GenBank (No. JN695498). Pathogenicity was confirmed by inoculating the leaves of three seedlings with a conidial suspension (~2 × 105 conidia/ml). Three noninoculated seedlings served as controls. Plants were maintained in a glasshouse at 100% relative humidity for 48 h. After 6 days, typical leaf spots, identical to the one observed in the field, started to develop on the leaves of the inoculated plants. No symptoms were observed on the control plants. The fungus was successfully reisolated from the symptomatic plants, fulfilling Koch's postulates. A leaf spot disease associated with S. epambrosiae has previously been recorded on A. artemisiifolia in Hungary (1-3) and A. trifida in North America (2,3). To our knowledge, this is the first report of S. epambrosiae on giant ragweed in Asia. Because of its potential as a biocontrol agent, further studies are needed.