scholarly journals First Report of Puccinia pelargonii-zonalis Causing Rust on Pelargonium × hortorum in Xinjiang Province, China

Plant Disease ◽  
2021 ◽  
Author(s):  
Jin Sun ◽  
Guo Qin Wang ◽  
Jia Ge Song ◽  
Biao Xu

Geranium (Pelargonium × hortorum) is an ornamental plant cultivated throughout world. In May 2019, typical symptoms of rust with nearly 90% disease incidence were observed on leaves of Pel. × hortorum growing in pots in a scenic spot in the ancient city of Kashgar, Xinjiang province, China. Early symptoms of the disease appeared small lesions with pale-yellow halos on the lower leaf surfaces. Infected tissues subsequently formed a concentric circle of sori on lesion reaching a final diameter of 0.5 to 1.5 cm, which resulted in leaf blighting and premature. Two representative specimens were deposited in the Mycological Herbarium of Tarim University (HMUT 8001 and HMUT 8002). Urediniospores were globose or subglobose to ovoid, light brown, echinulate, thin-walled with two conspicuous subequatorial pores, 19.8 to 27.3 × 17.8 to 23.6 μm (24.3 × 21.7 μm average, n=30). Telia and teliospores were not seen. The sizes and characteristics of urediniospores were similar with those of Puccinia pelargonii-zonalis as described by Doidge (1926). To confirm the identification, genomic DNAs were extracted directly from sori on diseased leaves from isolates HMUT 8001 and HMUT 8002. The part of the nuclear large subunit (LSU, 28S) rDNA was amplified and sequenced following Aime et al. (2006), and deposited in GenBank (Accession Nos. MT648851 and MT648852). An NCBI blast search indicated that 99.6% identity of the LSU (772/775 nucleotides) with Puc. pelargonii-zonalis on Pel. hortorum (KX999887) from Australia (Marin-Felix et al. 2017). The phylogenetic analysis based on the LSU sequences using Maximum-Likelihood and Bayesian methods placed the Xinjiang isolates from Pel. × hortorum in the same clade with the reference sequences of Puc. pelargonii-zonalis. Pathogenicity test was confirmed by Koch’s postulates. Leaves of three healthy potted plants were sprayed with a spore suspension (2 × 105 spores/ml). Sterile water was sprayed on three healthy seedlings as controls. Inoculated and control plants were covered with a plastic bag and placed in a moist chamber with 90% relative humidity at 25°C. Initial symptoms were observed with small light-yellow spots on the upper surface after 15 days, but not in the control plants. Puc. pelargonii-zonalis has been previously reported on Pel. × hortorum in Argentina, Australia, Canada, Georgia, Greece, India, Mexico, New Zealand, Norway, Portugal, South Africa, the United States, and Venezuela (Farr and Rossman 2021). Geranium rust was first found in Yunnan province in southwestern China (Zhou and Zhuang 2005). However, this is the first report of geranium rust in Xinjiang province in northwestern China. The occurrence of the disease seriously affected their ornamental and economic value.

Plant Disease ◽  
2014 ◽  
Vol 98 (9) ◽  
pp. 1275-1275 ◽  
Author(s):  
J. H. Park ◽  
S. E. Cho ◽  
K. S. Han ◽  
S. H. Lee ◽  
H. D. Shin

Hibiscus rosa-sinensis L., commonly known as Chinese hibiscus, is an evergreen flowering shrub belonging to the Malvaceae and is widely cultivated throughout Asia including Korea. In August 2013, blight was observed on Chinese hibiscus in a commercial flower nursery in Seoul, Korea. Initial symptoms began as reddish purple spots at the tip of flowers and expanded to encompass entire flowers. Infected lesions appeared water-soaked, reddish brown, and were followed by rapid rotting of infected tissues. Approximately 50% of the plants surveyed were affected. Monosporous sporangiola formed on infected tissue were transferred to potato dextrose agar (PDA). Fungal colonies were obtained that were at first white with abundant aerial mycelium, and then became yellowish with the appearance of sporangiola. Sporangiophores bearing sporangiola were erect to slightly curved, unbranched, and hyaline. Funnel-shaped secondary vesicles formed on the primary vesicles. Sporangiola were indehiscent, ovoid to subglobose, smooth, non-striated, brown to dark brown, 10 to 27.5 × 8.5 to 17 μm, and sometimes germinated in culture. The fungus was identified as Choanephora infundibulifera (Curr.) D.D. Cunn. based on the morphological and cultural characteristics (2). Voucher specimens were housed in the Korea University Herbarium (KUS). An isolate obtained from KUS-F27535 was deposited in the Korean Agricultural Culture Collection (Accession No. KACC47643) and used for a pathogenicity test and molecular analyses. To confirm identity of the fungus, genomic DNA was extracted with DNeasy Plant Mini Kits (Qiagen Inc., Valencia, CA). The internal transcribed spacer (ITS) region of rDNA and the D1/D2 region of the large subunit (LSU) were amplified with the primers ITS1/ITS4 and NL1/LR3, respectively (3), and sequenced. The resulting 635-bp ITS and 680-bp D1/D2 sequences were deposited in GenBank (Accession Nos. KF486539 and KF486538). A GenBank BLAST search revealed that the ITS sequences showed 100% similarity with that of C. infundibulifera (JN943009) and D1/D2 sequences also showed 100% identity with that of C. infundibulifera (JN939193). A sporangiola suspension (2 × 104 cells/ml) was sprayed over three pots of the shrub, kept in a humid chamber for 2 days, and placed in greenhouse (28°C and 80 to 100% RH). Another three potted plants of the same age were sprayed with sterile water and served as controls. After 4 days, typical blossom blight symptoms, identical to the ones observed in the nursery, developed on the inoculated flowers. No symptoms were observed on controls. C. infundibulifera was re-isolated from inoculated plants. Pathogenicity test was conducted twice with the same results, fulfilling Koch's postulates. Choanephora blight caused by C. infundibulifera on H. rosa-sinenesis has been reported in Japan, Myanmar, Nepal, Guinea, and the United States (1). In Korea, there was one record of this fungus on H. syriacus (1). To our knowledge, this is the first report of C. infundibulifera on H. rosa-sinensis in Korea. This pathogen could be a potential threat to the production of this ornamental shrub over a prolonged period of hot and humid weather. References: (1) D. F. Farr and A. Y. Rossman. Fungal Databases. Syst. Mycol. Microbiol. Lab., Online publication, ARS, USDA, Retrieved February 28, 2014. (2) P. M. Kirk. Mycol. Pap. 152:1, 1984. (3) G. Walther et al. Persoonia 30:11, 2013.


Plant Disease ◽  
2002 ◽  
Vol 86 (1) ◽  
pp. 71-71
Author(s):  
A. Garibaldi ◽  
A. Minuto ◽  
M. L. Gullino

The production of potted ornamental plants is very important in the Albenga Region of northern Italy, where plants are grown for export to central and northern Europe. During fall 2000 and spring 2001, sudden wilt of tussock bellflower (Campanula carpatica Jacq.) and butterfly flower (Schizanthus × wisetonensis Hort.) was observed on potted plants in a commercial greenhouse. Initial symptoms included stem necrosis at the soil line and yellowing and tan discoloration of the lower leaves. As stem necrosis progressed, infected plants growing in a peat, bark compost, and clay mixture (70-20-10) wilted and died. Necrotic tissues were covered with whitish mycelia that produced dark, spherical (2 to 6 mm diameter) sclerotia. Sclerotinia sclerotiorum was consistently recovered from symptomatic stem pieces of both plants disinfested for 1 min in 1% NaOCl and plated on potato dextrose agar amended with streptomycin sulphate at 100 ppm. Pathogenicity of three isolates obtained from each crop was confirmed by inoculating 45- to 60-day-old C. carpatica and Schizanthus × wisetonensis plants grown in containers (14 cm diameter). Inoculum that consisted of wheat kernels infested with mycelia and sclerotia of each isolate was placed on the soil surface around the base of previously artificially wounded or nonwounded plants. Noninoculated plants served as controls. All plants were maintained outdoors where temperatures ranged between 8 and 15°C. Inoculated plants developed symptoms of leaf yellowing, followed by wilt, within 7 to 10 days, while control plants remained symptomless. White mycelia and sclerotia developed on infected tissues and S. sclerotiorum was reisolated from inoculated plants. To our knowledge, this is the first report of stem blight of C. carpatica and Schizanthus × wisetonensis caused by S. sclerotiorum in Italy. The disease was previously observed on C. carpatica in Great Britain (2) and on Schizanthus sp. in the United States (1). References: (1) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St. Paul, MN, 1989. (2) J. Rees. Welsh J. Agric. 1:188, 1925.


Plant Disease ◽  
2014 ◽  
Vol 98 (11) ◽  
pp. 1580-1580 ◽  
Author(s):  
C. Kithan ◽  
L. Daiho

Etlingera linguiformis (Roxb.) R.M.Sm. of Zingiberaceae family is an important indigenous medicinal and aromatic plant of Nagaland, India, that grows well in warm climates with loamy soil rich in humus (1). The plant rhizome has medicinal benefits in treating sore throats, stomachache, rheumatism, and respiratory complaints, while its essential oil is used in perfumery. A severe disease incidence of leaf blight was observed on the foliar portion of E. linguiformis at the Patkai mountain range of northeast India in September 2012. Initial symptoms of the disease are small brown water soaked flecks appearing on the upper leaf surface with diameter ranging from 0.5 to 3 cm, which later coalesced to form dark brown lesions with a well-defined border. Lesions often merged to form large necrotic areas, covering more than 90% of the leaf surface, which contributed to plant death. The disease significantly reduces the number of functional leaves. As disease progresses, stems and rhizomes were also affected, reducing quality and yield. The diseased leaf tissues were surface sterilized with 0.2% sodium hypochlorite for 2 min followed by rinsing in sterile distilled water and transferred into potato dextrose agar (PDA) medium. After 3 days, the growing tips of the mycelium were transferred to PDA slants and incubated at 25 ± 2°C until conidia formation. Fungal colonies on PDA were dark gray to dark brown, usually zonate; stromata regularly and abundantly formed in culture. Conidia were straight to curved, ellipsoidal, 3-septate, rarely 4-septate, middle cells broad and darker than other two end cells, middle septum not median, smooth, 18 to 32 × 8 to 16 μm (mean 25.15 × 12.10 μm). Conidiophores were terminal and lateral on hyphae and stromata, simple or branched, straight or flexuous, often geniculate, septate, pale brown to brown, smooth, and up to 800 μm thick (2,3). Pathogen identification was performed by the Indian Type Culture Collection, Division of Plant Pathology, Indian Agricultural Research Institute, New Delhi (ITCC Accession No. 7895.10). Further molecular identity of the pathogen was confirmed as Curvularia aeria by PCR amplification and sequencing of the internal transcribed spacer (ITS) regions of the ribosomal DNA by using primers ITS4 and ITS5 (4). The sequence was submitted to GenBank (Accession No. MTCC11875). BLAST analysis of the fungal sequence showed 100% nucleotide similarity with Cochliobolus lunatus and Curvularia aeria. Pathogenicity tests were performed by spraying with an aqueous conidial suspension (1 × 106 conidia /ml) on leaves of three healthy Etlingera plants. Three plants sprayed with sterile distilled water served as controls. The first foliar lesions developed on leaves 7 days after inoculation and after 10 to 12 days, 80% of the leaves were severely infected. Control plants remained healthy. The inoculated leaves developed similar blight symptoms to those observed on naturally infected leaves. C. aeria was re-isolated from the inoculated leaves, thus fulfilling Koch's postulates. The pathogenicity test was repeated twice. To our knowledge, this is the first report of the presence of C. aeria on E. linguiformis. References: (1) M. H. Arafat et al. Pharm. J. 16:33, 2013. (2) M. B. Ellis. Dematiaceous Hyphomycetes. CMI, Kew, Surrey, UK, 1971. (3) K. J. Martin and P. T. Rygiewicz. BMC Microbiol. 5:28, 2005. (4) C. V. Suberamanian. Proc. Indian Acad. Sci. 38:27, 1955.


Plant Disease ◽  
2011 ◽  
Vol 95 (6) ◽  
pp. 775-775 ◽  
Author(s):  
V. Ayala-Escobar ◽  
V. Santiago-Santiago ◽  
A. Madariaga-Navarrete ◽  
A. Castañeda-Vildozola ◽  
C. Nava-Diaz

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.


Plant Disease ◽  
2005 ◽  
Vol 89 (9) ◽  
pp. 1016-1016
Author(s):  
A. Garibaldi ◽  
A. Minuto ◽  
M. L. Gullino

Rosmarinus officinalis L. ‘Prostratus’ is an evergreen shrub that is native to the Mediterranean Region in southern Europe and grown as a potted plant in Italy. This cultivar is widely used in gardens and landscapes. During the winter of 2002, extensive chlorosis was observed on 8-month-old potted plants of R. officinalis L. ‘Prostratus’ grown outdoors in commercial farms near Albenga in northern Italy. Initial symptoms included stem necrosis at the soil level and darkening of leaves. As stem necrosis progressed, infected plants wilted and died. Wilt, characterized by the presence of soft and watery tissues, occurred within a few days on young plants. The disease infected 15% of the plants. Necrotic tissues became covered with a whitish mycelium that produced dark sclerotia. The diseased stem tissue was surface sterilized for 1 min in 1% NaOCl and plated on potato dextrose agar (PDA) amended with 100 ppm of streptomycin sulfate. Sclerotinia sclerotiorum (1) was consistently recovered from infected stem pieces. Sclerotia observed on infected plants measured 0.30 to 3.33 × 1.00 to 4.23 mm (average 1.31 × 1.88 mm). Sclerotia produced on PDA measured 0.09 to 3.08 × 0.38 to 4.05 mm (average 1.94 × 2.43 mm). Pathogenicity of three isolates obtained from infected plants and used in mixture was confirmed by inoculating 60-day-old plants grown in 14-cm-diameter pots in a glasshouse. Inoculum (wheat kernels infested with mycelium and sclerotia) for each isolate was placed on the soil surface around the base of each plant. Pathogenicity tests included three inoculated plants grown in separate pots per isolate. Three noninoculated plants grown in three pots served as controls. The inoculation trial was conducted twice. All plants were kept at temperatures ranging between 8 and 34°C (average 18°C) and watered as needed. Plants were covered with plastic for 96 h after inoculation to increase the moisture level. All inoculated plants developed symptoms of leaf yellowing within 30 days, soon followed by the appearance of white mycelium and sclerotia, and eventual wilt. Control plants remained symptomless. S. sclerotiorum was reisolated from the stems of inoculated plants. To our knowledge, this is the first report of white mold of R. officinalis L. ‘Prostratus’ in Italy and in Europe. S. sclerotiorum has been previously reported on R. officinalis in India (2) and the United States (3). The economic importance of this disease for the crop in Italy can be considered low at the moment. References: (1) N. F. Buchwald. Den. Kgl. Veterin.er-og Landbohojskoles Aarsskrift, 32:75, 1949. (2) L. Mohan. Indian Phytopathol. 47:443, 1994. (3) M. L. Putnam. Plant Pathol. 53:252, 2004.


Plant Disease ◽  
2014 ◽  
Vol 98 (11) ◽  
pp. 1584-1584 ◽  
Author(s):  
E. A. Markakis ◽  
N. Kavroulakis ◽  
G. C. Koubouris

Avocado (Persea americana) is an important crop for Chania, Crete, Greece, and is grown on more than 800 ha. In November 2013, 4-year-old trees in a new avocado grove of cv. Hass grafted onto the rootstock ‘Bacon,’ previously planted in citrus trees, showed symptoms of yellowing, leaf fall, twig and branch dieback and vascular tissue discoloration. Disease incidence was estimated at 2.3% (12 out of 530 trees affected). A fungus was consistently and readily isolated from symptomatic vascular tissue, previously surface-disinfested with 95% ethanol, on acidified potato dextrose agar (APDA). After 7 days, slow-growing colonies were transferred to PDA and the growth rate of the fungus was 2.9 mm/day at 24°C in the dark. Microscopic observations revealed hyaline hyphae with many irregular, dark microsclerotia measuring 40 to 200 × 30 to 75 μm (average 94.5 × 50.3 μm) developing after 21 days of growth. Hyaline, elliptical, single-celled conidia measuring 2.8 to 7.5 × 2.5 to 4.3 μm (average 4.8 × 3.1 μm) developed on verticillate conidiophores. For molecular characterization, Verticillium dahliae specific primer pair ITS1-F/ITS2-R that amplifies the rRNA internal transcribed spacer (ITS) region was used (2). Band of expected size was amplified, sequenced, and deposited in GenBank (Accession No. KJ818294). On the basis of morphological characteristics (3) and a BLAST search with 100% identity to the published ITS sequence of a V. dahliae isolate in GenBank (KC834733.1), the fungus was identified as V. dahliae. Five 1-year-old avocado plants of cv. Hass, grafted onto the rootstock ‘Bacon,’ were used for pathogenicity tests. Artificial inoculation was performed by making a 5.0 × 3.5 mm hole in the rootstock trunk, injecting approximately 40 μl of a 2.8 × 107 conidia/ml suspension into the vessels (spores were introduced passively), sealing with Vaseline, and covering with adhesive paper tape. Five control plants were mock inoculated with sterilized distilled water. Disease symptoms that appeared 18 days post artificial inoculation were similar to those observed under natural infection conditions. Thirty-five days post artificial inoculation, disease incidence was 80%, whereas the percentage of positive V. dahliae re-isolations from infected tissues was 95% (96.7 and 93.3% from rootstock and graft, respectively). The extent of vascular tissue discoloration from the point of inoculation ranged from 11 to 62 cm, whereas V. dahliae was successfully re-isolated even from the end of the graft (approximately 60 cm above the initial inoculation point), thus confirming Koch's postulates. Neither symptoms nor positive isolations were observed in control plants. The pathogenicity test was repeated twice with similar results. Verticillium wilt of avocado has been observed in several countries including Argentina, Chile, Ecuador, Israel, Mexico, Morocco, Spain, and the United States (1). To the best of our knowledge, this is the first report of Verticillium wilt on avocado in Greece. This disease could potentially be an increasing problem in areas where young avocado trees are established on land previously planted in vegetable crops. References: (1) J. C. Goud and J. A. Hiemstra. Chapter 3 in: A Compendium of Verticillium Wilt in Trees Species, 1998. (2) E. A. Markakis et al. Eur. J. Plant Pathol. 124:603, 2009. (3) G. F. Pegg and B. L. Brady. Verticillium Wilts. CABI Publishing, Wallingford, UK, 2002.


Plant Disease ◽  
2008 ◽  
Vol 92 (7) ◽  
pp. 1133-1133
Author(s):  
A. Garibaldi ◽  
A. Minuto ◽  
M. L. Gullino

Calceolaria integrifolia L. is an ornamental species grown as a potted plant in Liguria, northern Italy. In the winter of 2006, extensive chlorosis was observed on approximately 10% of the 10-month-old potted plants in a commercial greenhouse. Initial symptoms included stem necrosis and darkening of leaves. As stem and foliar necrosis progressed, infected plants wilted and died. Wilt occurred on young plants within a few days after the initial appearance of symptoms. Infected plants were characterized by the presence of soft, watery tissues that became covered with white mycelium and dark sclerotia. The diseased stem tissue was surface sterilized for 1 min in 1% NaOCl and plated on potato dextrose agar (PDA) amended with 100 mg/liter of streptomycin sulfate. Sclerotinia sclerotiorum (Lib.) de Bary (3) was consistently recovered from infected stem pieces. Sclerotia observed on infected plants measured 0.7 to 1.0 × 2.8 to 4.4 mm (average 1.6 to 2.1 mm). Sclerotia produced on PDA measured 1.0 to 1.1 × 3.0 to 4.2 mm (average 1.7 to 2.3 mm). The internal transcribed spacer (ITS) region of rDNA was amplified with primers ITS4/ITS6 and sequenced. BLASTn analysis (1) of the 522-bp amplicon resulted in 100% homology with the sequence of S. sclerotiorum. The nucleotide sequence has been assigned GenBank Accession No. EU 627004. Pathogenicity of two isolates obtained from infected plants was confirmed by inoculating 10 120-day-old plants grown in individual 14-cm-diameter pots maintained in a greenhouse under partial shade. Inoculum consisted of 1 cm2 of mycelial plugs excised from a 10-day-old PDA culture of each isolate. Plants were inoculated by placing a mycelial plug on the soil surface around the base of each plant. Ten plants were inoculated per isolate and an equal number of noninoculated plants served as controls. The trial was repeated once. All plants were kept at temperatures ranging between 8 and 17°C (average 12.5°C) and watered as needed. All inoculated plants developed leaf yellowing within 8 days after inoculation, soon followed by the appearance of white mycelium and sclerotia, and then by wilt. Control plants remained symptomless. S. sclerotiorum was reisolated from the stems of inoculated plants. S. sclerotiorum was reported previously on a Calceolaria sp. in the United States (2). To our knowledge, this is the first report of white mold on C. integrifolia in Italy. The economic importance of this disease is currently limited. References (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) Anonymous. USDA Agric. Handb. 165:441, 1960. (3) N. F. Buchwald. Den. Kgl. Veterin.er-og Landbohojskoles Aarsskrift 75, 1949.


Plant Disease ◽  
2012 ◽  
Vol 96 (4) ◽  
pp. 588-588 ◽  
Author(s):  
A. Garibaldi ◽  
G. Gilardi ◽  
G. Ortu ◽  
M. L. Gullino

Fuchsia is a genus of flowering plants that is native to South America and New Zealand and belongs to the family Onagraceae. In September 2011, 2-year-old potted plants of Fuchsia × hybrida, cv. Citation, in a garden located near Biella (northern Italy) showed signs and symptoms of a previously unknown disease. Typically, infected plants showed leaf chlorosis followed by the appearance of necrosis on the adaxial leaf surfaces, while the abaxial surfaces showed orange uredinia irregularly distributed. As the disease progressed, infected leaves turned yellow and wilted. Affected plants showed a progressive phylloptosis and also flowering was negatively affected. Urediniospores were globose, yellow to orange, and measured 14.6 to 25.9 (average 19.6) μm. Teliospores were not observed. Morphological characteristics of the fungus corresponded to those of the genus Pucciniastrum. DNA extraction and PCR amplification were carried out with Terra PCR Direct Polymerase Mix (Clontech, Saint Germain-en-Laye, France) and primers ITS1/ITS4 (4). A 700-bp PCR product was sequenced and a BLASTn search (1) confirmed that the sequence corresponded with a 96% identity to Pucciniastrum circaeae. The nucleotide sequence has been assigned the GenBank Accession No. JQ029688. Pathogenicity tests were performed by spraying leaves of healthy 1-year-old potted Fuchsia × hybrida plants with an aqueous suspension of 1 × 103 urediniospores ml–1. The inoculum was obtained from infected leaves. Plants sprayed only with water served as controls. Three plants were used for each treatment. Plants were covered with plastic bags for 4 days after inoculation and maintained outdoors at temperatures ranging between 18 and 25°C. Lesions developed on leaves 20 days after inoculation with the urediniospore suspension, showing the same symptoms as the original plants, whereas control plants remained healthy. The organism that was recovered from the lesions after inoculation was the same as the one obtained from the diseased plants. The pathogenicity test was carried out twice with similar results. The presence of P. fuchsiae, later identified as P. epilobii, was repeatedly reported in the United States (3). P. epilobii and P. circaeae have closely related hosts and morphologically similar urediniospores. These species were reported to form a single group in molecular phylogenetic trees (2). This is, to our knowledge, the first report of P. circaeae on Fuchsia × hybrida in Italy. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997 (2) Y. M. Liang et al. Mycoscience 47:137, 2006. (3) L. B. Loring and L. F. Roth. Plant Dis. Rep. 48:99, 1964. (4) T. J. White et al. PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al., eds. Academic Press, San Diego, 1990.


Plant Disease ◽  
2021 ◽  
Author(s):  
Yang Zhang ◽  
Guangqiang Li ◽  
Dou Yang ◽  
Ruoling Zhang ◽  
Songze Wan

Mu oil tree (Vernicia montana) is an economically important woody oil plant, which is widely distributed in southern China. In mid-May 2020, a leaf spot disease was observed on the leaves of mu oil tree in Taihe County in Jiangxi Province, China (26°55′25.55″N, 114°49′5.85″E). The disease incidence was estimated to be above 40%. Initial symptoms were circular red-brown spots which were 1-2 mm in diameter, then enlarged with red-brown center. In later stages, the spots coalesced and formed large patches, and subsequently red-brown centers of lesions gradually dried and fell out, forming a “shot hole” appearance. To identify the pathogen, diseased leaves were collected from Taihe County. Leaf tissues (5 × 5 mm) were cut from the margins of typical symptomatic lesions, surface- sterilized in 75% ethanol for 30 seconds and 3% sodium hypochlorite for 60 seconds, then rinsed with sterile distilled water three times. Leaf pieces were placed on potato dextrose agar (PDA; 1.5%, Difco-BD Diagnostics) and incubated at 25 °C in the dark. Pure cultures were obtained from individual conidia by recovering single spores. On PDA, colonies were initially white and cottony. The mycelia then became pinkish to deep-pink with time at the center on the front side and pink on the reverse side. Colonies produced pale orange conidial masses after 9 days. Conidia were fusiform with acute ends, smooth-walled, hyaline, and measured 3.6–5.5 × 8.1–14.5 µm (4.5 ± 0.5 × 10.6 ± 1.0 µm, n = 100). The morphological characteristics of the isolate matched the descriptions of Colletotrichum acutatum complex (Damm et al. 2012). For molecular identification, the internal transcribed spacer (ITS) region, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), chitin synthase (CHS-1), beta-tubulin 2 (TUB2), and actin (ACT) were sequenced using the primers ITS1/ITS4, GDF/GDR, CHS-79F/CHS-345R, T1/Bt2b, ACT-512F/ACT-783R, respectively (Weir et al. 2012). The obtained sequences were deposited into the GenBank [accession nos. MW584317 (ITS); MW656269 (GAPDH); MW656270 (TUB2); MW656268 (CHS-1); MW656267 (ACT)]. All the sequences showed 94 to 100% similarity with those of C. fioriniae. A neighbor-joining phylogenetic tree was generated by combining all the sequenced loci using MEGA7.0 (Kumar et al. 2016). The isolate TH-M4 clustered with C. fioriniae, having 99% bootstrap support. Base on the morphology and multi-gene phylogeny, isolate TH-M4 was identified as C. fioriniae (Damm et al. 2012). To confirm pathogenicity, 20 healthy leaves of 10 mu oil trees (3-year-old) grown outdoors were inoculated with a drop of spore suspension (106 conidia per mL) of the isolate TH-M4 in September 2020. Another 10 plants were inoculated with sterile water as the control. The leaves were wounded with a sterile toothpick. All the inoculated leaves were covered with black plastic bags to maintain humidity for 2 days. The pathogenicity test was repeated twice. The resulting symptoms were similar to those on the original infected plants, whereas the control leaves remained asymptomatic. The same fungus was re-isolated from the lesions on the inoculated plant, fulfilling Koch’s postulates. C. fioriniae has been recorded as anthracnose pathogen on Mahonia aquifolium (Garibaldi et al. 2020), Paeonia lactiflora (Park et al. 2020), Solanum melongena (Xu et al. 2020), and Juglans regia (Varjas et al. 2020). To our knowledge, this is the first report of C. fioriniae associated with leaf spot disease on mu oil tree in China. This study provided crucial information for epidemiologic studies and appropriate control strategies for this oil plant disease.


Plant Disease ◽  
2015 ◽  
Vol 99 (1) ◽  
pp. 158-158 ◽  
Author(s):  
J. H. Park ◽  
S. E. Cho ◽  
K. S. Han ◽  
B. S. Kim ◽  
H. D. Shin

Hosta plantaginea (Lam.) Asch. is an herbaceous perennial plant with ornamental value. In August 2013, water-soaked spots and wet rot were found on flowers of H. plantaginea in a garden bedded out for landscaping in Hongcheon County, Korea. Symptoms initially appeared as water-soaked spots at the tips of flowers. Dark gray spots on flower petals often coalesced and led to rotting of flowers, with abundant sporulation. However, no symptoms were found on the leaves. Approximately 30% of the flowers were affected in the landscape bed. A fungal isolate was obtained by plating surface-disinfested diseased flower tissue on potato dextrose agar (PDA). Fungal colonies covering the plate (diam. 90 mm) in 48 h were white at first, with abundant aerial mycelia, but later turned pale yellow with abundant sporangiola. Sporangiophores bearing sporangiola were aseptate, hyaline, and usually arose from infected tissue. Sporangiola were ellipsoid to ovoid, indehiscent, brown to dark brown, pediculate, 7 to 12 μm wide and 9 to 20 μm high, and showed longitudinal striations at high magnification. Sporangia were few-spored to multispored, pale brown to brown, and 50 to 150 μm. Sporangiospores from sporangia were broadly ellipsoid, brown to pale brown, with hyaline polar appendages, 8 to 10 μm wide and 15 to 22 μm high. Zygospores were not observed. The morphological and cultural characteristics, especially based on shape and striation of sporangiola, were identical with those of Choanephora cucurbitarum (Berk. & Ravenel) Thaxt. (2,3). A representative specimen was deposited in the Korea University Herbarium (KUS-F27540). Genomic DNA was extracted using a DNeasy Plant Mini Kit (Qiagen Inc., Valencia, CA). The primers ITS1/ITS4 and NL1/LR3 were used to amplify the internal transcribed spacer (ITS) region of rDNA and the D1/D2 region of the large subunit (LSU), respectively (4). The PCR products were purified and directly sequenced. The resulting 594-bp ITS and 680-bp D1/D2 sequences were submitted to GenBank (Accession Nos. KM200034 and KM200035). A GenBank BLAST search of the fungal database showed that the sequences of ITS and D1/D2 regions matched those of C. cucurbitrarum (JN943006 and JN939195) with 100% similarity. A pathogenicity test was conducted by spraying three healthy potted plants (2 months old) with a sporangiola suspension (2 × 104 conidia/ml). Another three potted plants of the same age were treated with sterile water and served as controls. The plants were kept in humid chambers for 2 days and placed in a greenhouse (28°C and 60 to 80% RH). After 4 to 5 days, water-soaked spots were evident on the flowers of inoculated plants. No symptoms were observed on control plants. A pathogenicity test was conducted twice with the same results, fulfilling Koch's postulates. C. cucurbitarum has a wide host range but has not been previously reported to cause disease on H. plantaginea (1). To our knowledge, this is the first report of C. cucurbitarum on H. plantaginea globally as well as in Korea. Choanephora rot of flowers is an issue under high-moisture conditions, so allowing for adequate airflow and a dry plant canopy should aid in disease suppression. References: (1) D. F. Farr and A. Y. Rossman. Fungal Databases. Syst. Mycol. Microbiol. Lab. Online publication, ARS, USDA, retrieved July 11, 2014. (2) P. M. Kirk. Mycol. Pap. 152:1, 1984. (3) A. Saroj et al. Plant Dis. 96:293, 2012. (4) G. Walther et al. Persoonia 30:11, 2013.


Sign in / Sign up

Export Citation Format

Share Document