First Report of Rice Brown Spot Caused by Exserohilum rostratum in Mali

Rice brown spot is an emerging disease of concern in many rice-growing countries. Different fungal species of the genera Bipolaris and Exserohilum were reported as the causal agents of this disease. These fungal pathogens cause similar necrotic lesions on leaves and infect grains with a significant effect on seed germination. In 2018, samples of rice seed and leaves with typical brown spot symptoms were collected from irrigated (Manikoura and Niono) and lowlands (M’pegnesso and Loulouni) rice fields in Mali and incubated for 5 to 7 days on wet filter paper at 25°C with 12 h photoperiod. Conidia observed under microscope were straight or slightly curved and light-brown or dark. They were also rostrate or obclavate and measured 31.4 to 275.6 x 7.3 to 18 µm (n=40). These morphological characteristics are identical to those of Exserohilum rostratum (Hernández-Restrepo et al. 2018). DNA from eight single-spored isolates was extracted by a CTAB-based protocol (Doyle and Doyle, 1987). Internal transcribed spacer (ITS) rDNA region, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and translation elongation factor 1 alpha (TEF1-α) genes were amplified by PCR with the primers ITS5/ITS4 (White et al. 1990), GPD1/GPD2 (Berbee et al. 1999) and EF1 983/EF1 2218 (Rehner et al. 2005), respectively. The amplicons were sequenced and deposited in NCBI GenBank. Sequence similarity between Malian strain was 100% for ITS and GAPDH, and 99.8-100% for TEF1. Sequence similarity between Malian strains and reference E. rostratum sequences BRIP 11417 (GenBank acc. no. LT837836, LT882553 and LT896656) and CBS 128061 (GenBank acc. no. KT265240, LT715900 and LT896658) were 99.6-100%. The maximum-likelihood phylogenetic tree generated with ITS, GAPDH and TEF1-α concatenated sequences, using MEGA-X 10.1.7 grouped all eight strains from Mali in the E. rostratum clade with a bootstrap value of 100%. For pathogenicity test, four strains from leaves and seed were grown on rabbit food agar (50 g/liter steeped filtrate of rabbit food pellets, Kaytee Products, Inc. Chilton, WI, USA, and 15 g agar) for 14 days at 25°C with a 12 h photoperiod (Hau and Rush 1980). Spores were collected and the concentration of spore suspension adjusted to 1.5 x 105 conidia/ml with 0.5% gelatin. The rice varieties ADNY 11, ARICA 9 and Shwetasoké were grown in pots with peat soil and NPK 13-5-18 at 3.5 g/liter of soil for 21 days. Four pots of each variety (5 seedlings/pot) were placed in a tray (60 plants per tray) and the leaves were sprayed with 30 ml of the conidial suspension or water at 0.5% gelatin (negative control). Plants were kept at maximum humidity (100%) at 21°C for one night and then transferred to a phytotron at 27°C. Seven days after inoculation, circular or oval foliar lesions of less than 5 mm long, either brown or dark, sometimes whitish in their centers were observed . These lesions were identical to those observed in the field. E. rostratum was reisolated from these lesions. E. rostratum affects a wide range of plant species, particularly grasses and has been observed on rice in many countries (Cardona and Gonzàlez 2007; Majeed et al. 2016; Silva et al. 2016; Toher et al. 2016). However, to our knowledge, this is the first report of E. rostratum causing brown spot in rice in Mali.

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First Report of Stem and Foliage Blight of Chrysanthemum Caused by Phytophthora drechsleri in the United States

Plant Disease ◽

10.1094/pdis-03-21-0631-pdn ◽

2021 ◽

Author(s):

Charles Krasnow ◽

Nancy Rechcigl ◽

Jennifer Olson ◽

Linus Schmitz ◽

Steven N. Jeffers

Keyword(s):

United States ◽

South Carolina ◽

Sequence Similarity ◽

Morphological Characteristics ◽

The United States ◽

Universal Primers ◽

Broad Host Range ◽

Pathogenicity Test ◽

First Report ◽

Foliage Blight

Chrysanthemum (Chrysanthemum × morifolium) plants exhibiting stem and foliage blight were observed in a commercial nursery in eastern Oklahoma in June 2019. Disease symptoms were observed on ~10% of plants during a period of frequent rain and high temperatures (26-36°C). Dark brown lesions girdled the stems of symptomatic plants and leaves were wilted and necrotic. The crown and roots were asymptomatic and not discolored. A species of Phytophthora was consistently isolated from the stems of diseased plants on selective V8 agar (Lamour and Hausbeck 2000). The Phytophthora sp. produced ellipsoid to obpyriform sporangia that were non-papillate and persistent on V8 agar plugs submerged in distilled water for 8 h. Sporangia formed on long sporangiophores and measured 50.5 (45-60) × 29.8 (25-35) µm. Oospores and chlamydospores were not formed by individual isolates. Mycelium growth was present at 35°C. Isolates were tentatively identified as P. drechsleri using morphological characteristics and growth at 35°C (Erwin and Ribeiro 1996). DNA was extracted from mycelium of four isolates, and the internal transcribed spacer (ITS) region was amplified using universal primers ITS 4 and ITS 6. The PCR product was sequenced and a BLASTn search showed 100% sequence similarity to P. drechsleri (GenBank Accession Nos. KJ755118 and GU111625), a common species of Phytophthora that has been observed on ornamental and vegetable crops in the U.S. (Erwin and Ribeiro 1996). The gene sequences for each isolate were deposited in GenBank (accession Nos. MW315961, MW315962, MW315963, and MW315964). These four isolates were paired with known A1 and A2 isolates on super clarified V8 agar (Jeffers 2015), and all four were mating type A1. They also were sensitive to the fungicide mefenoxam at 100 ppm (Olson et al. 2013). To confirm pathogenicity, 4-week-old ‘Brandi Burgundy’ chrysanthemum plants were grown in 10-cm pots containing a peat potting medium. Plants (n = 7) were atomized with 1 ml of zoospore suspension containing 5 × 103 zoospores of each isolate. Control plants received sterile water. Plants were maintained at 100% RH for 24 h and then placed in a protected shade-structure where temperatures ranged from 19-32°C. All plants displayed symptoms of stem and foliage blight in 2-3 days. Symptoms that developed on infected plants were similar to those observed in the nursery. Several inoculated plants died, but stem blight, dieback, and foliar wilt were primarily observed. Disease severity averaged 50-60% on inoculated plants 15 days after inoculation. Control plants did not develop symptoms. The pathogen was consistently isolated from stems of symptomatic plants and verified as P. drechsleri based on morphology. The pathogenicity test was repeated with similar results. P. drechsleri has a broad host range (Erwin and Ribeiro 1996; Farr et al. 2021), including green beans (Phaseolus vulgaris), which are susceptible to seedling blight and pod rot in eastern Oklahoma. Previously, P. drechsleri has been reported on chrysanthemums in Argentina (Frezzi 1950), Pennsylvania (Molnar et al. 2020), and South Carolina (Camacho 2009). Chrysanthemums are widely grown in nurseries in the Midwest and other regions of the USA for local and national markets. This is the first report of P. drechsleri causing stem and foliage blight on chrysanthemum species in the United States. Identifying sources of primary inoculum may be necessary to limit economic loss from P. drechsleri.

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First Report of Ramularia coleosporii causing Leaf Spot on Perilla frutescens in Korea

Plant Disease ◽

10.1094/pdis-01-21-0223-pdn ◽

2021 ◽

Author(s):

Md Aktaruzzaman ◽

Tania Afroz ◽

Hyo-Won Choi ◽

Byung Sup Kim

Keyword(s):

Leaf Spot ◽

Ipomoea Batatas ◽

Rust Fungus ◽

Morphological Characteristics ◽

Perilla Frutescens ◽

Herbaceous Plant ◽

Pathogenicity Test ◽

Conidial Suspension ◽

Single Spore ◽

First Report

Perilla (Perilla frutescens var. japonica), a member of the family Labiatae, is an annual herbaceous plant native to Asia. Its fresh leaves are directly consumed and its seeds are used for cooking oil. In July 2018, leaf spots symptoms were observed in an experimental field at Gangneung-Wonju National University, Gangneung, Gangwon province, Korea. Approximately 30% of the perilla plants growing in an area of about 0.1 ha were affected. Small, circular to oval, necrotic spots with yellow borders were scattered across upper leaves. Masses of white spores were observed on the leaf underside. Ten small pieces of tissue were removed from the lesion margins of the lesions, surface disinfected with NaOCl (1% v/v) for 30 s, and then rinsed three times with distilled water for 60 s. The tissue pieces were then placed on potato dextrose agar (PDA) and incubated at 25°C for 7 days. Five single spore isolates were obtained and cultured on PDA. The fungus was slow-growing and produced 30-50 mm diameter, whitish colonies on PDA when incubated at 25ºC for 15 days. Conidia (n= 50) ranged from 5.5 to 21.3 × 3.5 to 5.8 μm, were catenate, in simple or branched chains, ellipsoid-ovoid, fusiform, and old conidia sometimes had 1 to 3 conspicuous hila. Conidiophores (n= 10) were 21.3 to 125.8 × 1.3 to 3.6 μm in size, unbranched, straight or flexuous, and hyaline. The morphological characteristics of five isolates were similar. Morphological characteristics were consistent with those described for Ramularia coleosporii (Braun, 1998). Two representative isolates (PLS 001 & PLS003) were deposited in the Korean Agricultural Culture Collection (KACC48670 & KACC 48671). For molecular identification, a multi-locus sequence analysis was conducted. The internal transcribed spacer (ITS) regions of the rDNA, partial actin (ACT) gene and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene were amplified using primer sets ITS1/4, ACT-512F/ACT-783R and gpd1/gpd2, respectively (Videira et al. 2016). Sequences obtained from each of the three loci for isolate PLS001 and PLS003 were deposited in GenBank with accession numbers MH974744, MW470869 (ITS); MW470867, MW470870 (ACT); and MW470868, MW470871 (GAPDH), respectively. Sequences for all three genes exhibited 100% identity with R. coleosporii, GenBank accession nos. GU214692 (ITS), KX287643 (ACT), and 288200 (GAPDH) for both isolates. A multi-locus phylogenetic tree, constructed by the neighbor-joining method with closely related reference sequences downloaded from the GenBank database and these two isolates demonstrated alignment with R. coleosporii. To confirm pathogenicity, 150 mL of a conidial suspension (2 × 105 spores per mL) was sprayed on five, 45 days old perilla plants. An additional five plants, to serve as controls, were sprayed with sterile water. All plants were placed in a humidity chamber (>90% relative humidity) at 25°C for 48 h after inoculation and then placed in a greenhouse at 22/28°C (night/day). After 15 days leaf spot symptoms, similar to the original symptoms, developed on the leaves of the inoculated plants, whereas the control plants remained symptomless. The pathogenicity test was repeated twice with similar results. A fungus was re-isolated from the leaf lesions on the inoculated plants which exhibited the same morphological characteristics as the original isolates, fulfilling Koch’s postulates. R. coleosporii has been reported as a hyperparasite on the rust fungus Coleosporium plumeriae in India & Thailand and also as a pathogen infecting leaves of Campanula rapunculoides in Armenia, Clematis gouriana in Taiwan, Ipomoea batatas in Puerto Rico, and Perilla frutescens var. acuta in China (Baiswar et al. 2015; Farr and Rossman 2021). To the best of our knowledge, this is the first report of R. coleosporii causing leaf spot on P. frutescens var. japonica in Korea. This disease poses a threat to production and management strategies to minimize leaf spot should be developed.

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First Report of Passalora Leaf Spot Caused by Passalora bougainvilleae on Bougainvillea in Mexico

Plant Disease ◽

10.1094/pdis-11-10-0787 ◽

2011 ◽

Vol 95 (6) ◽

pp. 775-775 ◽

Cited By ~ 1

Author(s):

V. Ayala-Escobar ◽

V. Santiago-Santiago ◽

A. Madariaga-Navarrete ◽

A. Castañeda-Vildozola ◽

C. Nava-Diaz

Keyword(s):

Uv Light ◽

Disease Incidence ◽

Morphological Characteristics ◽

The United States ◽

Pathogenicity Test ◽

Commonwealth Mycological Institute ◽

Conidial Suspension ◽

Single Spore ◽

First Report ◽

Bougainvillea Spectabilis

Bougainvillea (Bougainvillea spectabilis Willd) growing in 28 gardens during 2009 showed 100% disease incidence and 3 to 7% disease severity. Bougainvilleas with white flowers were the most affected. Symptoms consisted of light brown spots with dark brown margins visible on adaxial and abaxial sides of the leaves. Spots were circular, 2 to 7 mm in diameter, often surrounded by a chlorotic halo, and delimited by major leaf veins. Single-spore cultures were incubated at 24°C under near UV light for 7 days to obtain conidia. Pathogenicity was confirmed by spraying a conidial suspension (1 × 104 spores/ml) on leaves of potted bougainvillea plants (white, red, yellow, and purple flowers), incubating the plants in a dew chamber for 48 h and maintaining them in a greenhouse (20 to 24°C). Identical symptoms to those observed at the residential gardens appeared on inoculated plants after 45 to 60 days. The fungus was reisolated from inoculated plants that showed typical symptoms. No symptoms developed on control plants treated with sterile distilled water. The fungus produced distinct stromata that were dark brown, spherical to irregular, and 20 to 24 μm in diameter. Conidiophores were simple, born from the stromata, loose to dense fascicles, brown, straight to curved, not branched, zero to two septate, 14 × 2 μm, with two to four conspicuous and darkened scars. The conidia formed singly, were brown, broad, ellipsoid, obclavate, straight to curved with three to four septa, 40 × 4 μm, and finely verrucous with thick hilum at the end. Fungal DNA from the single-spore cultures was obtained using a commercial DNA Extraction Kit (Qiagen, Valencia, CA); ribosomal DNA was amplified with ITS5 and ITS4 primers and sequenced. The sequence was deposited at the National Center for Biotechnology Information Database (GenBank Accession Nos. HQ231216 and HQ231217). The symptoms (4), morphological characteristics (1,2,4), and pathogenicity test confirm the identity of the fungus as Passalora bougainvilleae (Muntañola) Castañeda & Braun (= Cercosporidium bougainvilleae Muntañola). This pathogen has been reported from Argentina, Brazil, Brunei, China, Cuba, El Salvador, India, Indonesia, Jamaica, Japan, Thailand, the United States, and Venezuela (3). To our knowledge, this is the first report of this disease on B. spectabilis Willd in Mexico. P. bougainvilleae may become an important disease of bougainvillea plants in tropical and subtropical areas of Mexico. References: (1) U. Braun and R. R. Castañeda. Cryptogam. Bot. 2/3:289, 1991. (2) M. B. Ellis. More Dematiaceous Hypomycetes. Commonwealth Mycological Institute, Kew, Surrey, UK, 1976. (3) C. Nakashima et al. Fungal Divers. 26:257, 2007. (4) K. L. Nechet and B. A. Halfeld-Vieira. Acta Amazonica 38:585, 2008.

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

Plant Disease ◽

10.1094/pdis-03-12-0277-pdn ◽

2012 ◽

Vol 96 (7) ◽

pp. 1070-1070 ◽

Cited By ~ 1

Author(s):

J. H. Park ◽

K. S. Han ◽

Y. D. Kwon ◽

H. D. Shin

Keyword(s):

Colletotrichum Gloeosporioides ◽

Morphological Characteristics ◽

Its Region ◽

Culture Collection ◽

Perennial Herb ◽

Pathogenicity Test ◽

Conidial Suspension ◽

Natural Habitats ◽

First Report ◽

Small Water

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. References: (1) K. Sawada. Rep. Dept. Agric. Gov. Res. Inst. Formosa 87: 1, 1944. (2) B. C. Sutton. Pages 1–27 in: Colletotrichum Biology, Pathology and Control. J. A. Bailey and M. J. Jeger, eds. CAB International, Wallingford, U.K. 1992. (3) S. C. Teng. Contrib. Biol. Lab. Sci. Soc. China 8:36, 1932.

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First Report of Alternaria Brown Spot of Citrus Caused by Alternaria alternata in Yunnan Province, China

Plant Disease ◽

10.1094/pdis-94-3-0375c ◽

2010 ◽

Vol 94 (3) ◽

pp. 375-375 ◽

Cited By ~ 7

Author(s):

X. F. Wang ◽

Z. A. Li ◽

K. Z. Tang ◽

C. Y. Zhou ◽

L. Yi

Keyword(s):

Alternaria Alternata ◽

Yunnan Province ◽

Morphological Characteristics ◽

Control Measures ◽

Brown Spot ◽

Control Treatment ◽

Infected Leaf ◽

Conidial Suspension ◽

First Report ◽

Alternaria Brown Spot

Brown spot of citrus is considered a major problem on the fruit of many citrus cultivars grown for fresh markets including tangerines (Citrus reticulata) and their hybrids. It causes lesions on leaves, stems, and fruit and reduces yield and fruit quality (2). In 2003 in southern Wenshan Municipality, Yunnan Province in China, sporadic occurrence of Alternaria brown spot was observed on Tangfang mandarin, a local citrus cultivar identified preliminarily as a kind of mandarin hybrid. From 2006 to 2008, nearly 80% of local orchards were infected with the disease. Fruit symptoms typical of Alternaria brown spot ranging from light brown, slightly depressed spots to circular and dark brown areas were observed. Leaves showed small, brown, circular spots and irregular blighted areas with characteristic yellow halos. Tissues from the margin of fruit spots or infected leaf parts of eight different trees were surface sterilized in 1.5% sodium hypochlorite for 1 min, plated on potato dextrose agar (PDA), and then incubated at 27°C in the dark for 1 week. Dark brown mycelia and pigmented septate conidia with lengths of 10 to 35 μm and widths of 5 to 13 μm were produced. On the basis of conidial morphological characteristics, the pathogen was identified as Alternaria alternata (Fr.:Fr.) Keissl (1). Detached young healthy leaves of ‘Minneola’ tangelo (C. reticulata × C. paradisi) were sprayed with a conidial suspension of 105 conidia per ml and incubated in a moist chamber at 27°C. A control treatment with an equal number of leaves was sprayed with distilled water only. After 48 h, seven of these isolates caused necrotic lesions on detached leaves, characteristic of the disease, whereas there were no symptoms on leaves of the water control. Pure cultures were recovered on PDA from symptomatic tissues and the morphological characteristics of the conidia closely fit the description of A. alternata, confirming Koch's postulates. Currently, the distribution of Alternaria brown spot of citrus is confined to southern Wenshan Municipality in Yunnan Province where it is a serious disease problem on the most important commercial cultivar in this region. The identification of the pathogen now allows for appropriate field management and control measures. To our knowledge, this is the first report of Alternaria brown spot of citrus in China. References: (1) Z. Solel. Plant Pathol. 40:145, 1991. (2) J. O. Whiteside. Plant Dis. Rep. 60:326, 1976.

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First report of Cercospora cf. citrulina causing leaf spot of Ipomoea pes-caprae in China

Plant Disease ◽

10.1094/pdis-05-20-1081-pdn ◽

2020 ◽

Author(s):

Min Li ◽

Meijiao Hu ◽

Zhaoyin Gao ◽

Xiaoyu Hong ◽

Chao Zhao ◽

...

Keyword(s):

Molecular Identification ◽

Leaf Spot ◽

Plant Protection ◽

Morphological Characteristics ◽

Pathogenicity Test ◽

Conidial Suspension ◽

Xisha Islands ◽

First Report ◽

Initial Symptoms ◽

Leaf Surfaces

Ipomoea pes-caprae plays an important role in protecting the tropical and subtropical coastal beach of the world. In 2018, a leaf spot was observed on I. pes-caprae in Xisha islands of China, 13.2–25.8% of leaves were infected. The initial symptoms were small (1–3 mm diameter), single, circular, dark gray spots with a light-yellow center on the leaves. The lesions enlarged and were scattered or confluent, distinct and circular, subcircular or irregular, occasionally vein-limited, pale to dark gray-brown, with a narrow dark brown border surrounded by a diffuse yellow margin. Microscopic observations of the spots revealed that caespituli were dark brown and amphigenous, but abundant on the underside of the leaves. Mycelia were internal. Conidiophores were fasciculate, occasionally solitary, pale olivaceous-brown throughout, 0- to 3-septate, 27.9–115.8 (63.4±22.5) µm × 3.2–5.3 (4.3±0.87) µm (n=100). Conidial scars were conspicuously thickened. Conidia were solitary, hyaline, filiform, acicular to obclavate, straight to slightly curved, subacute to obtuse at the apex, truncate at the base, multi-septate, 21.0–125.5 (60.2±20.1) µm × 2.0–5.0 (3.8±0.83) µm (n=100). Single-conidium isolates were obtained from representative colonies grown on potato dextrose agar (PDA) incubated at 25℃ in the dark. The colonies grew slowly and were dense, white to gray and flat with aerial mycelium. Mycelia were initially white, and then became gray. Conidia were borne on the conidiophores directly. The pure isolate HTW-1 was selected for molecular identification and pathogenicity test, which were deposited in Microbiological Culture Collection Center of Environment and Plant Protection Institute, Chinese Academy of Tropical Agricultural Sciences. The internal transcribed spacer (ITS) region of rDNA, translation elongation factor 1-alpha (tef1) and histone H3 (his3) genes were amplified with ITS1/ITS4, EF-1 / EF-2, and CYLH3F / CYLH3R primers, respectively (Groenewald et al. 2013). The obtained sequences of HTW-1 were all deposited in GenBank with accession numbers MT410467 for ITS, MT418903 for tef1 and MT418904 for his3. The ITS, tef1 and his3 genes all showed 100% similarity for ITS (JX143582), tef1 (JX143340) and his3 (JX142602) with C. cf. citrulina (MUCC 588; MAFF 239409) from I. pes-caprae in Japan. Based on the morphological characteristics and molecular identification, the pathogen was identified as Cercospora cf. citrulina (Groenewald et al. 2013). The pathogenicity test was conducted by spraying conidial suspension (1×104 conidia/mL) on wounded and unwounded leaves for seedling of I. pes-caprae in greenhouse and in sterile vitro condition. The conidial suspension was prepared using conidia from 30-day-old culture grown on PDA at 25℃ in the dark. Leaf surfaces of seedling in greenhouse were wounded by lightly rubbing with a steel sponge and detached leaf surfaces were wounded by sterile needles. the treatments were sprayed with conidial suspensions on wounded and unwounded leaf surfaces. The control was sprayed with sterile water. After eight days, the typical symptoms of spots which were small, single, circular and dark gray appeared on the inoculated wounded leaves, while the inoculated unwounded leaves and the control leaves were symptomless. The pathogen was only re-isolated from the inoculated wounded leaves. The pathogen may be infected by wound. A total of 20 Cercospora and related species was found on Ipomoea spp. (García et al. 1996). Cercospora cf. citrulina has been reported on I. pes-caprae in Japan, although it was unclear if it was a pathogen or saprophyte (Groenewald et al. 2013). To our knowledge, this is the first report of C. cf. citrulina causing leaf spot of I. pes-caprae in China. This disease could threat the cultivation of I. pes-caprae in China.

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First Report of Fusarium Wilt in Blueberry (Vaccinium corymbosum) Caused by Fusarium oxysporum in China

Plant Disease ◽

10.1094/pdis-02-14-0167-pdn ◽

2014 ◽

Vol 98 (8) ◽

pp. 1158-1158 ◽

Cited By ~ 1

Author(s):

Y. H. Liu ◽

T. Lin ◽

C. S. Ye ◽

C. Q. Zhang

Keyword(s):

Fusarium Oxysporum ◽

Infected Plant ◽

Morphological Characteristics ◽

Vaccinium Corymbosum ◽

Morphological Characterization ◽

Internal Transcribed Spacers ◽

Fluorescent Light ◽

Pathogenicity Test ◽

Conidial Suspension ◽

First Report

Blueberry (Vaccinium corymbosum) production is developing quickly in China with about 20,000 ha presently cultivated. In 2010 in Lin'an, Zhejiang Province, plants developed an apparently new disease of blueberry (cv. Duke) with symptoms consisting of wilting of foliage, stunting of plants, and reduced fruit yields. Internal vascular and cortical tissues of plant crowns showed a brown to orange discoloration. Approximately 3% of the plants in the commercial plantings were affected and eventually died after 50 to 60 days. Infected plant samples (stems and roots) collected from different fields were surface sterilized with 1.5% sodium hypochlorite for 2 min, rinsed in water, plated on 2% potato dextrose agar (PDA), and incubated at 25°C in the dark for 1 week. Single conidium cultures were consistently isolated and cultured on acidified PDA (APDA) for morphological characterization (1,2). Colonies were light with purple mycelia, and beige or orange reverse colony colors developed after 7 days incubation at 25°C. Colonies producing abundant microconidia and macroconidia. Microconidia were hyaline and oval-ellipsoid to cylindrical (3.9 to 9.6 × 1.1 to 3.4 μm). Macroconidia were 3 to 5 septate and fusoid-subulate with a pedicellate base (28.6 to 37.5 × 3.3 to 4.2 μm). Morphology and development of macroconidia and microconida were consistent with a description of Fusarium oxysporum Schltdl (1,2). The ribosomal internal transcribed spacers ITS1 and ITS2 of eight isolates were amplified using primers ITS1/ITS4 on DNA extracted from mycelium and nucleotide sequences showed 100% similarity to that of F. oxysporum. To confirm pathogenicity, 20 blueberry plants (cv. Duke) were inoculated by dipping the roots into a conidial suspension (107 conidia per ml) for 30 min. The inoculated plants were transplanted into pots containing sterilized peat and maintained at 25°C and 100% relative humidity in a growth chamber with a daily 12-h photoperiod of fluorescent light. The pathogenicity test was conducted twice. Within 40 days, all inoculated plants developed wilt symptoms similar to that observed in the field. No symptoms were observed on plants dipped into distilled water. The fungus was successfully re-isolated from crowns and roots cultured on APDA, exhibiting morphological characteristics identical to F. oxysporum (1,2), confirming Koch's postulates. To our knowledge, this is the first report of blueberry wilt caused by Fusarium. References: (1) P. M. Kirk et al. The Dictionary of the Fungi, 10th edition, page 159. CABI Bioscience, Wallingford, UK, 2008. (2) W. C. Snyder and H. N. Hansen. Am. J. Bot. 27:64, 1940.

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First Report of Fusarium Maize Ear Rot Caused by Fusarium meridionale in China

Plant Disease ◽

10.1094/pdis-01-14-0108-pdn ◽

2014 ◽

Vol 98 (8) ◽

pp. 1156-1156 ◽

Cited By ~ 4

Author(s):

H. Zhang ◽

W. Luo ◽

Y. Pan ◽

J. Xu ◽

J. S. Xu ◽

...

Keyword(s):

Fusarium Species ◽

Elongation Factor ◽

Morphological Characteristics ◽

Pathogenicity Test ◽

Conidial Suspension ◽

Fusarium Ear Rot ◽

Ear Rot ◽

Translation Elongation Factor ◽

Translation Elongation ◽

First Report

Fusarium is an important genus of fungal pathogens that are responsible for devastating diseases, such as Fusarium ear rot on maize, which may result in yield losses and/or mycotoxin contamination. In September 2013, a survey to determine population composition of Fusarium species on maize was conducted at 22 fields in 18 counties in Gansu Province. Maize ears with clear symptoms (with a white to pink- or salmon-colored mold at the ear tip) were collected. Symptomatic seeds were surface-sterilized with 70% ethanol and 10% sodium hypochlorite and rinsed three times with sterile water to eliminate hypochlorite residues. After drying on sterile filter paper, the seeds were placed on potato dextrose agar (PDA) and incubated at 25°C in the dark for 3 days. Mycelium that was characteristic of Fusarium spp. (2) was purified by transferring single spores to fresh PDA. Fusarium species were identified by morphological characteristics (2), multilocus genotyping assay (MLGT) (3), and sequence analysis of the translation elongation factor-1α (TEF) gene. Several Fusarium species were identified and Fusarium verticillioides and F. proliferatum were the predominant species. Based on MLGT, two strains from Chenghong County were identified as F. meridionale with NIV chemotype, a species in F. graminearum species complex (FGSC). Morphological characteristics were also identical to FGSC. Colonies grew rapidly on PDA and produce relatively large amounts of dense mycelia and red pigments. Slender, thick-walled, and moderately curved or straight macroconidia were observed with 5- to 6-septate. Furthermore, conidia on SNA also showed typical characteristics of F. meridionale, as the dorsal and ventral lines were often parallel and gradually curved. Sequences comparison of the partial translation elongation factor (TEF-1α, 644 bp) gene (1) was used to validate these observations. BLASTn analysis with the FUSARIUM-ID database revealed 100% sequence identity to F. meridionale (GenBank Accession No. KJ137017). Thus, both morphological and molecular criteria supported identification of the strains as F. meridionale. A pathogenicity test was performed on Zhengdan958, the maize variety with the largest planted acreage in China. Four days after silk emergence, 2 ml conidial suspension (105 macroconidia/ml) of each isolate were injected into each of 10 maize ears through silk channel. Control plants were inoculated with sterile distilled water. Typical FER symptoms (reddish-white mold) was observed on inoculated ears and no symptoms were observed on water controls. Koch's postulates were fulfilled by re-isolating the same fungus from the infected seeds. F. meridionale was one of the pathogens causing Fusarium head blight on wheat and barley in China and produced nivalenol (4,5) and it also has been isolated from maize in Korea and Nepal. To our knowledge, this is the first report of F. meridionale causing Fusarium ear rot on maize in China. Further studies on biological characteristics such as temperature sensibility and fungicide resistance are needed to gain a better understanding of this new pathogen. References: (1) D. M. Geiser et al. Eur. J. Plant Pathol. 110:473, 2004. (2) J. F. Leslie and B. A. Summerell. The Fusarium Laboratory Manual. Blackwell Publishing, Ames, IA, 2006. (3) T. J. Ward et al. Fungal Genet. Biol. 45:473, 2008. (4) L. Yang et al. Phytopathology 98:719, 2008. (5) H. Zhang et al. Plos one 7:e31722, 2012.

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First report of Fusarium falciforme (FSSC 3+4) causing root rot on chickpea in Mexico

Plant Disease ◽

10.1094/pdis-05-21-1123-pdn ◽

2021 ◽

Author(s):

Sixto Velarde Felix ◽

Victor Valenzuela ◽

Pedro Ortega ◽

Gustavo Fierros ◽

Pedro Rojas ◽

...

Keyword(s):

Fusarium Solani ◽

Root Rot ◽

Species Complex ◽

Elongation Factor ◽

Morphological Characteristics ◽

Aerial Mycelium ◽

Pathogenicity Test ◽

Conidial Suspension ◽

Single Spore ◽

First Report

Chickpea (Cicer aretinium L.) is a legume crop of great importance worldwide. In January 2019, wilting symptoms on chickpea (stunted grow, withered leaves, root rot and wilted plants) were observed in three fields of Culiacan Sinaloa Mexico, with an incidence of 3 to 5%. To identify the cause, eighty symptomatic chickpea plants were sampled. Tissue from roots was plated on potato dextrose agar (PDA) medium. Typical Fusarium spp. colonies were obtained from all root samples. Ten pure cultures were obtained by single-spore culturing (Ff01 to Ff10). On PDA the colonies were abundant with white aerial mycelium, hyphae were branched and septae and light purple pigmentation was observed in the center of old cultures (Leslie and Summerell 2006). From 10-day-old cultures grown on carnation leaf agar medium, macroconidias were falciform, hyaline, with slightly curved apexes, three to five septate, with well-developed foot cells and blunt apical cells, and measured 26.6 to 45.8 × 2.2 to 7.0 μm (n = 40). The microconidia (n = 40) were hyaline, one to two celled, produced in false heads that measured 7.4 to 20.1 (average 13.7) μm × 2.4 to 8.9 (average 5.3) μm (n = 40) at the tips of long monophialides, and were oval or reniform, with apexes rounded, 8.3 to 12.1 × 1.6 to 4.7 μm; chlamydospores were not evident. These characteristics fit those of the Fusarium solani (Mart.) Sacc. species complex, FSSC (Summerell et al. 2003). The internal transcribed spacer and the translation elongation factor 1 alpha (EF1-α) genes (O’Donnell et al. 1998) were amplified by polymerase chain reaction and sequenced from the isolate Ff02 and Ff08 (GenBank accession nos. KJ501093 and MN082369). Maximum likelihood analysis was carried out using the EF1-α sequences (KJ501093 and MN082369) from the Ff02 and Ff08 isolates and other species from the Fusarium solani species complex (FSSC). Phylogenetic analysis revealed the isolate most closely related with F. falciforme (100% bootstrap). For pathogenicity testing, a conidial suspension (1x106 conidia/ml) was prepared by harvesting spores from 10-days-old cultures on PDA. Twenty 2-week-old chickpea seedlings from two cultivars (P-2245 and WR-315) were inoculated by dipping roots into the conidial suspension for 20 min. The inoculated plants were transplanted into a 50-hole plastic tray containing sterilized soil and maintained in a growth chamber at 25°C, with a relative humidity of >80% and a 12-h/12-h light/dark cycle. After 8 days, the first root rot symptoms were observed on inoculating seedlings and the infected plants eventually died within 3 to 4 weeks after inoculation. No symptoms were observed plants inoculated with sterilized distilled water. The fungus was reisolated from symptomatic tissues of inoculated plants and was identified by sequencing the partial EF1-α gene again and was identified as F. falciforme (FSSC 3 + 4) (O’Donnell et al. 2008) based on its morphological characteristics, genetic analysis, and pathogenicity test, fulfilling Koch’s postulates. The molecular identification was confirmed via BLAST on the FusariumID and Fusarium MLST databases. Although FSSC has been previously reported causing root rot in chickpea in USA, Chile, Spain, Cuba, Iran, Poland, Israel, Pakistan and Brazil, to our knowledge this is the first report of root rot in chickpea caused by F. falciforme in Mexico. This is important for chickpea producers and chickpea breeding programs.

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First Report of Anthracnose Caused by Colletotrichum gloeosporioides on Malus prunifolia in Korea

Plant Disease ◽

10.1094/pdis-01-12-0063-pdn ◽

2012 ◽

Vol 96 (5) ◽

pp. 766-766 ◽

Cited By ~ 1

Author(s):

W. Cheon ◽

Y. S. Kim ◽

Y. H. Jeon

Keyword(s):

Colletotrichum Gloeosporioides ◽

Sequence Similarity ◽

Morphological Characteristics ◽

Its Rdna ◽

Plant Diseases ◽

Conidial Suspension ◽

Korean Society ◽

First Report ◽

Malus Prunifolia ◽

Crab Apple

In 2010 and 2011, crab apples in Andong Province, Korea were found with dark brown spots on the fruit and mummified fruit on a tree. The fruit surface had red, circular spots that contained smaller, white spots; the color of the inner spots later changed to brown or black. Eventually, the rotten fruit dried and became mummified. Microscopic examination revealed the presence of acervuli and dark brown-to-black, needle-shaped setae. To isolate potential pathogens from infected fruit, small sections (5 to 10 mm2) were excised from the margins of lesions. These sections were surface sterilized with 70% ethanol and 1% NaOCl for 1 min and then rinsed three times with sterile distilled water. The fungus that was isolated produced whitish mycelia when grown on potato dextrose agar (PDA); the mycelia later became gray to dark gray with aerial mycelia in tufts and numerous conidia were produced. The conidia were straight, cylindrical with an obtuse apex and a truncated base, and measured 11.4 to 17.5 × 4.2 to 7.1 μm. The measurements and taxonomic characteristics coincide with those of Colletotrichum gloeosporioides (Penz.) (1). The isolated fungus was tested for pathogenicity on crab apples and cv. Fuji apples by inoculation with a conidial suspension (105 conidia/ml) prepared from 20-day-old PDA cultures. A 20-μl drop of the conidial suspension was placed onto crab apple and apple fruits that had been wounded by piercing them 1 to 2 mm deep with a pin. Small, dark lesions were observed on the artificially inoculated fruit 3 days after inoculation. Nine days after inoculation, dark lesions with salmon-colored masses of conidia were observed on fruit, which were also soft and sunken. Abundant masses of conidia were produced in the decayed tissues. The fungus was reisolated from the parts of the fruits showing the symptoms. The internal transcribed spacer (ITS) rDNA of the isolated fungus was amplified and sequenced by PCR as described by White et al. (2). The resulting 582-bp of ITS rDNA sequence was deposited in GenBank (Accession No. JQ405742). A BLAST analysis for sequence similarity of the ITS region revealed 100% identity with nucleotide sequences for C. gloeosporioides isolates (Accession Nos. HQ645080 and AB458667). The results obtained on morphological characteristics, pathogenicity, and molecular data corresponded with those of C. gloeosporioides described by Sutton (1). To our knowledge, this is the first report of the presence of C. gloeosporioides on crab apple in Korea (3). Crab apple is used as a pollinator for single-cultivar apple orchards and may become a possible source of inoculum for cultivated apple. References: (1) T. B. Sutton. Compendium of Apple and Pear Diseases. The American Phytopathological Society, St. Paul, MN, 1990. (2) T. J. White et al. PCR Protocols: A Guide to Methods and Applications, Academic Press, Inc., New York, 1990. (3) S. H. Yu. List of Plant Diseases in Korea. 5th ed. (in Korean). The Korean Society of Plant Pathology, 2009.

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