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

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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Outbreaks of Alternaria Brown Spot of Citrus in Brazil and Argentina

Plant Disease ◽

10.1094/pdis.2003.87.6.750c ◽

2003 ◽

Vol 87 (6) ◽

pp. 750-750 ◽

Cited By ~ 19

Author(s):

N. A. R. Peres ◽

J. P. Agostini ◽

L. W. Timmer

Keyword(s):

Morphological Characteristics ◽

Severe Infection ◽

Sao Paulo ◽

Brown Spot ◽

Control Treatment ◽

Citrus Reticulata ◽

Conidial Suspension ◽

São Paulo ◽

Surface Sterilization ◽

Alternaria Brown Spot

Alternaria alternata (Fr.) Keissler causes lesions on leaves, twigs, and fruit and reduces yield and fruit quality of many tangerines (Citrus reticulata) and their hybrids (2). Severe outbreaks of Alternaria brown spot were observed on ‘Murcott’ tangor (Citrus reticulata × Citrus sinensis) trees in southern São Paulo, southern Minas Gerais states in Brazil, and in Misiones and Corrientes provinces in Argentina. A single diseased ‘Fortune’ tangerine tree was observed in a grove in Misiones. On young leaves, brown-to-black lesions often expanded to cover large parts of the leaf, causing abscission of young shoots and dieback of twigs. Lesions were often surrounded by yellow halos. On fruit, dark specks from 0.2 to 0.5 cm were observed, and severe infection caused premature fruit abscission. Isolations were made on potato dextrose agar (PDA) after surface sterilization of leaf and fruit tissues in 1.5% sodium hypochlorite for 1 min. Plates were incubated at 27°C in the dark for 1 week. Isolated colonies were olive brown to black, and the fungus was stimulated to form conidia by scraping the surface of the mycelium. The pathogen was a typical small-spored Alternaria species, and the morphological characteristics of the conidia and conidiophores fit the description of A. alternata. Inoculation of three detached young shoots of ‘Murcott’ with a conidial suspension (105 conidia per ml) confirmed pathogenicity of three isolates obtained from widely separated groves in southern and eastern São Paulo State in Brazil and one from Misiones Province in Argentina. A control treatment with an equal number of shoots was sprayed with distilled water only. After 48 h, all isolates caused dark lesions on the leaves, characteristic of the disease. Symptoms were observed on inoculated, but not on control shoots. Koch's postulates were satisfied by reisolation of the fungus from symptomatic tissue in all cases. Although Alternaria brown spot was reported previously in neighboring Rio de Janeiro, Brazil on ‘Dancy’ and ‘Ponkan’ tangerines (1), serious disease problems now occur on ‘Murcott’, an important commercial variety in the major production area in Brazil. To our knowledge, this is the first report of Alternaria brown spot in Argentina. References: (1) A. de Goes et al. Fitopatologia Brasileira 26(Suppl.):386, 2001. (2) L. W. Timmer et al. Pages 19–21 in: Compendium of Citrus Diseases. 2nd ed. L. W. Timmer, S. M. Garnsey, and J. H. Graham, eds. The American Phytopathological Society, St. Paul, MN, 2000.

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First Report of Leaf Blight of Basella alba Caused by Alternaria alternata in India

Plant Disease ◽

10.1094/pdis-06-11-0513 ◽

2011 ◽

Vol 95 (11) ◽

pp. 1476-1476 ◽

Cited By ~ 6

Author(s):

N. Ravi Sankar ◽

A. Sreeramulu ◽

D. Sai Gopal ◽

G. Bagyanarayana

Keyword(s):

Alternaria Alternata ◽

Disease Incidence ◽

Morphological Characteristics ◽

Infected Leaf ◽

Conidial Suspension ◽

First Report ◽

Perennial Plant ◽

Basella Alba ◽

Leaf Spots ◽

Severe Infections

Basella alba is a perennial plant of the Basellaceae, native to India, and is distributed widely in the tropics as an ornamental. It is also known as Indian spinach, Ceylon spinach, vine spinach, Malabar spinach or Malabar nightshade and is mostly cultivated as a leafy vegetable or spinach substitute, being rich in vitamin A and C. From 2008 to 2010, severe foliar disease was observed on B. alba in the region of Southern Andhra Pradesh, India. Approximately 75 to 85% of the fields were affected with disease incidence ranging from 70 to 90%. Leaf lesions were elliptical to irregular oval, yellow brown to dark brown, and sometimes concentrically zonate with diffuse margins frequently surrounded by light-colored haloes. Infection often started at the leaf tips and progressed to the base of leaves as symptoms developed. In severe infections, lesions enlarged and coalesced, causing necrosis, wilting, and ultimately death of leaves. Tissues from the margin of infected leaf parts were surface sterilized in 1% sodium hypochlorite for 1 min, plated on potato dextrose agar (PDA), and then incubated at 27°C in the dark for 7 days. Hyphal tips from the margin of each developing colony were subcultured on PDA. Fungal colonies were initially white, becoming olivaceous, and turning brown with age. Conidiophores were brown, short, simple, or sometimes branched. Conidia were obclavate, obpyriform or ellipsoidal with a short conical beak, borne in long chains, branched or unbranched, pale brown to brown, and 18 to 32 μm long and 5 to 14 μm wide at the broadest point. Conidia had three to eight transverse septa and one to two longitudinal septa. On the basis of conidial morphological characteristics, the pathogen was identified as Alternaria alternata (Fr.) Keissler (2). For pathogenicity tests, inoculations were performed on detached, surface sterilized, healthy leaves following the method of Belisario (1). A 5-μl drop of conidial suspension containing 1 × 105 CFU/ml was placed on each leaf and 12 leaves per isolate were used. Leaves were incubated in a growth chamber (90% relative humidity with a 12-h photoperiod). After 7 days, leaf spots that were similar to the original symptoms developed on all inoculated leaves and A. alternata was consistently reisolated from symptomatic leaf tissues on PDA. Control leaves inoculated with sterile distilled water remained asymptomatic. The experiment was performed three times. To our knowledge, this is the first report of A. alternata on B. alba in India. References: (1) A. Belisario et al. Plant Dis. 83:696, 1999. (2) E. G. Simmons. Alternaria: An Identification Manual. The American Phytopathological Society, St. Paul, MN, 2007.

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First Report of Powdery Mildew Caused by Golovinomyces biocellatus on Agastache rugosa in Korea

Plant Disease ◽

10.1094/pdis-03-14-0298-pdn ◽

2014 ◽

Vol 98 (9) ◽

pp. 1278-1278 ◽

Cited By ~ 1

Author(s):

S. E. Cho ◽

J. H. Park ◽

S. H. Hong ◽

I. Y. Choi ◽

H. D. Shin

Keyword(s):

Powdery Mildew ◽

Severe Disease ◽

Morphological Characteristics ◽

Control Measures ◽

Control Treatment ◽

Width Ratio ◽

Korean Isolate ◽

Pathogenicity Test ◽

Agastache Rugosa ◽

First Report

Agastache rugosa (Fisch. & C.A. Mey.) Kuntze, known as Korean mint, is an aromatic plant in the Lamiaceae. It is widely distributed in East Asian countries and is used as a Chinese traditional medicine. In Korea, fresh leaves are commonly added to fish soups and stews (3). In November 2008, several dozen Korean mints plants growing outdoors in Gimhae City, Korea, were found to be severely infected with a powdery mildew. The same symptoms had been observed in Korean mint plots in Busan and Miryang cities from 2008 to 2013. Symptoms first appeared as thin white colonies, which subsequently developed into abundant hyphal growth on stems and both sides of the leaves. Severe disease pressure caused withering and senescence of the leaves. Voucher specimens (n = 5) were deposited in the Korea University Herbarium (KUS). Appressoria on the mycelium were nipple-shaped or nearly absent. Conidiophores were 105 to 188 × 10 to 13 μm and produced 2 to 4 immature conidia in chains with a sinuate outline, followed by 2 to 3 cells. Foot-cells of the conidiophores were straight, cylindrical, slightly constricted at the base, and 37 to 58 μm long. Conidia were hyaline, ellipsoid to barrel-shaped, measured 25 to 40 × 15 to 23 μm (length/width ratio = 1.4 to 2.1), lacked distinct fibrosin bodies, and showed reticulate wrinkling of the outer walls. Primary conidia were obconically rounded at the apex and subtruncate at the base. Germ tubes were produced at the perihilar position of conidia. No chasmothecia were observed. The structures described above were typical of the Oidium subgenus Reticuloidium anamorph of the genus Golovinomyces. The measurements and morphological characteristics were compatible with those of G. biocellatus (Ehrenb.) V.P. Heluta (1). To confirm the identification, molecular analysis of the sequence of the internal transcribed spacer (ITS) region of ribosomal DNA (rDNA) of isolate KUS-F27200 was conducted. The complete ITS rDNA sequence was amplified using primers ITS5 and P3 (4). The resulting 514-bp sequence was deposited in GenBank (Accession No. KJ585415). A GenBank BLAST search of the Korean isolate sequence showed >99% similarity with the ITS sequence of many G. biocellatus isolates on plants in the Lamiaceae (e.g., Accession Nos. AB307669, AB769437, and JQ340358). Pathogenicity was confirmed by gently pressing diseased leaf onto leaves of five healthy, potted Korean mint plants. Five non-inoculated plants served as a control treatment. Inoculated plants developed symptoms after 7 days, whereas the control plants remained symptomless. The fungus present on inoculated plants was identical morphologically to that observed on the original diseased plants. The pathogenicity test was repeated with identical results. A powdery mildew on A. rugosa caused by G. biocellatus was reported from Romania (2). To our knowledge, this is the first report of powdery mildew caused by G. biocellatus on A. rugosa in Korea. The plant is mostly grown using organic farming methods with limited chemical control options. Therefore, alternative control measures should be considered. References: (1) U. Braun and R. T. A. Cook. Taxonomic Manual of the Erysiphales (Powdery Mildews), CBS Biodiversity Series No. 11. CBS, Utrecht, 2012. (2) D. F. Farr and A. Y. Rossman. Fungal Databases. Syst. Mycol. Microbiol. Lab., online publication, USDA ARS, retrieved 17 February 2014. (3) T. H. Kim et al. J. Sci. Food Agric. 81:569, 2001. (4) S. Takamatsu et al. Mycol. Res. 113:117, 2009.

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First Report of Powdery Mildew Caused by Golovinomyces ambrosiae on Verbena bonariensis in Korea

Plant Disease ◽

10.1094/pdis-02-21-0349-pdn ◽

2021 ◽

Author(s):

In-Young Choi ◽

Ho-Jong Ju ◽

Kui-Jae Lee ◽

Hyeon-Dong Shin

Keyword(s):

Powdery Mildew ◽

Large Subunit ◽

Morphological Characteristics ◽

Morphological Characterization ◽

Control Measures ◽

Width Ratio ◽

Infected Leaf ◽

Voucher Specimen ◽

First Report ◽

Pcr Products

Verbena bonariensis L., named as purple-top vervain or Argentinian vervain, is native to tropical South America. It is cultivated worldwide as an ornamental plant. During summer and autumn of 2020, over 50% of the leaves of V. bonariensis were found infected with powdery mildew in a flower garden in Seoul (37°35'19"N 127°01'07"E), Korea. White, superficial mycelia developed initially on the leaves and subsequently covered surfaces of leaves and stems, are resulting in leaf discoloration, early defoliation, and shoots distortion. Heavily infected plants lost ornamental value. A representative voucher specimen was deposited in the Korea University herbarium (KUS-F32168). Morphological characterization and measurements of conidiophores and conidia were carried out using fresh samples. Microscopic observation showed that aAppressoria on the superficial hypha were nipple-shaped, but rarely found or nearly absent. Conidiophores (n = 30) were cylindrical, 110 to 220 × 10 to 12 µm, and produced 2 to 5 immature conidia in chains with a sinuate outline, followed by 2 to 3 short cells. Foot-cells of conidiophores were straight, cylindrical, and 46 to 90 μm long. Conidia (n = 30) were hyaline, ellipsoid to doliiform, 28 to 40 × 18 to 24 μm with a length/width ratio of 1.3 to 2.0, and contained small be like oil-like drops, but without distinct fibrosin bodies. Primary conidia were apically rounded and sub-truncate at the base. Germ tubes were produced at perihilar position of the conidia. Chasmothecia were not observed. These morphological characteristics were typical of the conidial stage of the genus Golovinomyces (Braun and Cook 2012, Qiu et al. 2020). To identify the fungus, rDNA was extracted from the voucher sample. PCR products were amplified using the primer pair ITS1F/PM6 for internal transcribed spacer (ITS), and PM3/TW14 for the large subunit (LSU) of the rDNA (Takamatsu and Kano 2001). The resulting sequences were registered to GenBank (MW599742 for ITS, and MW599743 for LSU). Using Blast’n search of GenBank, sequences showed 100% identity for ITS and LSU with G. ambrosiae (MT355557, KX987303, MH078047 for ITS, and AB769427, AB769426 for LSU), respectively. Thus, based on morphology and molecular analysis, the isolate on V. bonariensis in Korea was identified as G. ambrosiae (Schwein.) U. Braun & R.T.A. Cook. Pathogenicity tests were carried out by touching an infected leaf onto healthy leaves of disease-free pot-grown plants using a replication of five plants, with five non-inoculated plants used as controls. After 7 days, typical powdery mildew colonies started to appear on the inoculated leaves. The fungus on inoculated leaves was morphologically identical to that originally observed in the field. All non-inoculated control leaves remained symptomless. On different global Verbena species, tThere have been many reports of Golovinomyces powdery mildews including G. cichoracearum s.lat., G. longipes, G. monardae, G. orontii s.lat., and G. verbenae (Farr and Rossman 2021). In China, G. verbenae was recorded on V.erbena phlogiflora (Liu et al. 2006). Golovinomyces powdery mildew has not been reported on Verbena spp. in Korea. Powdery mildew has been reported on V. bonariensis in California, but identity of the causal agent had not been reported. To our knowledge, this is the first report on the identity of the powdery mildew caused by G. ambrosiae on V. bonariensis in Korea. Since heavily infected plants lost ornamental value, appropriate control measures should be developed.

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First report of fruit blight caused by Alternaria alternata on sesame in Northeast China

Plant Disease ◽

10.1094/pdis-01-21-0047-pdn ◽

2021 ◽

Author(s):

Hongsen Cheng ◽

De Xue Gao ◽

Huijie Sun ◽

Yanbin Na ◽

Jing Xu

Keyword(s):

Alternaria Alternata ◽

Morphological Characteristics ◽

Its Region ◽

Liaoning Province ◽

Oilseed Crop ◽

Distilled Water ◽

Conidial Suspension ◽

First Report ◽

Health Products ◽

Blight Disease

Sesame (Sesamum indicum L.) is an important oilseed crop in China and it is also used in food and health products. In August of 2019, a blight sesame fruit was observed in a field of Liaoyang city, Liaoning province of China. Initial disease symptoms consisted of brown or dark brown spots on fruit. With time, lesions coalesced and the whole fruit turned dark brown or black. Most of the diseased fruit had thin and small, deformed, necrotic, hardened cracked epidermal lesions. Lesions were also produced on stem and petioles leading to leaf abscission. The disease results in premature fruit death, and in turn, considerable yield losses. To determine the causal agent, symptomatic fruit with developing lesions were collected, and surface sterilized in 2% NaClO for 3 min, rinsed three times in distilled water, and plated onto PDA medium. After incubation at 25°C for 5 days, a dark olivaceous fungus with abundant, branched, brown to black, and septate hyphae was consistently isolated. Twenty single spores were separated with an inoculation needle under stereomicroscope. The conidia were in chains, brown, obclavate, ovoid or ellipsoid, with 1-6 transverse septa and 0-4 longitudinal or oblique septa 12.5 to 45 × 6.5 to 14.5 μm in size. Conidiophores were septate, light brown to olive brown, measuring 22-60 μm × 2-4 μm. The morphological characteristics of the 20 isolates all matched the description of Alternaria alternata (Simmons, 2007). The internal transcribed spacer (ITS) region of rDNA of 15 isolates was amplified using primers ITS1/ITS4 (White et al. 1990) and EF1-728F/EF1-986R (Carbone et al. 1999) and sequenced. Identical sequences were obtained and the sequence of the isolate ZMHG12 was submitted to GenBank (Accession no. MW418181 and MW700316). BLAST analysis of the sequences of the isolates of ZMHG12 showed 100% to A. alternata (KP739875 and LC132712). In pathogenicity tests, a conidial suspension (2.5 × 105 conidia per ml) was prepared from 7 days-old cultures of isolate ZMHG12 grown on PDA at 25°C. Fruit of 10 two-month-old potted sesame plants (Variety “Liaozhi 8”) were sprayed with the conidia suspension until runoff. Another 10 plants sprayed with distilled water to served as non-inoculated controls. All plants were maintained for 48 h in a humid chamber with a temperature of 25°C to 26°C, and then moved to a greenhouse. Ten days after inoculation, all fruit of inoculated plants exhibited symptoms similar to those observed in the field and non-inoculated control plants remained symptomless. The experiment was repeated twice with similar results. A. alternata has been reported as a pathogen caused leaf blight disease of sesame in Pakistan (Nayyar et al. 2017). To our knowledge, this is the first report of A.alternata causing fruit blight of sesame in China. To date, we have observed the disease on sesames in fields of Fuxin, Chaoyang and Tieling city in Liaoning Province, and Tongliao city in Inner Mongolia of China, and it has become an important disease in sesame production of China. References : Simmons E. G. 2007. Alternaria: An identification manual. CBS Fungal Biodiversity Center, Utrecht, Netherlands. White T. J., et al. 1990. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego. Carbone I., et al. 1999. Mycologia, 91: 553-556. Nayyar, B. G., et al. 2017. Plant Pathology Journal, 33 (6): 543-553.

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First Report of Ascochyta rabiei Causing Ascochyta Blight of Chickpea in Argentina

Plant Disease ◽

10.1094/pdis-02-12-0153-pdn ◽

2012 ◽

Vol 96 (9) ◽

pp. 1375-1375 ◽

Cited By ~ 3

Author(s):

G. Viotti ◽

M. A. Carmona ◽

M. Scandiani ◽

A. N. Formento ◽

A. Luque

Keyword(s):

Disease Incidence ◽

Ascochyta Blight ◽

Morphological Characteristics ◽

Pathogenic Fungi ◽

Ascochyta Rabiei ◽

Infected Leaf ◽

Buenos Aires Province ◽

Conidial Suspension ◽

First Report ◽

Plastic Bags

In November 2011, lesions similar to those reported for Ascochyta blight (1) were observed on Cicer arietinum L. (chickpea) plants growing in three commercial fields located at Río Primero and Río Segundo (Cordoba Province) and Lobería (Buenos Aires Province), Argentina. Disease incidence (percentage of plants affected) was 100% in all fields surveyed. Plants showed leaves, petioles, stems, and pods with brown lesions. Symptoms on leaves and pods were circular to oval (2 to 14 mm) while in the stems the lesions were elongated (2 to 30 mm). Seeds appeared small and shriveled with brown discoloration. Morphology of the fungi was examined on infected tissues. Numerous black pycnidia measuring 94.6 to 217.9 μm (145.9 ± 28.8 μm), arranged in concentric rings, were observed within of all the lesions. Conidia were predominantly aseptate, straight, hyaline with blunt ends, and measured 9.3 to 12.9 (11.3 ± 1.12) × 3.3 to 5.0 μm (4.2 ± 0.51). Morphological characteristics of the pathogen were similar to those described for Ascochyta rabiei (Pass.) Labrousse (teleomorph Didymella rabiei (Kovacheski) v. Arx (= Mycosphaerella rabiei Kovacheski)) (2). Fungus from infected leaf tissues was isolated on potato dextrose agar. Pathogenicity tests were conducted on seedlings of the susceptible cultivar by spraying leaves of each of 100 seedling plants with 10 ml of a conidial suspension (2 × 104 conidia/ml) of the isolated pathogen with a handheld atomizer. Plants were covered with plastic bags and placed in a growing chamber at 20 to 25°C for 3 days. The plastic bags were removed and the plants were maintained in high humidity at the same temperature. Noninoculated plants were used as controls. After 5 days, all inoculated plants showed typical symptoms. Foliar and stem lesions symptoms were similar to those originally observed in the field. Control plants remained healthy. Koch's postulates were fulfilled by isolating A. rabiei from inoculated plants. The colonies and the morphology of conidia were the same as those of the original isolates. To our knowledge, this is the first report of A. rabiei infecting chickpeas in Argentina. The outbreak of Ascochyta blight in Argentina is of concern because of its severity and the possibility that the pathogen was introduced on seed. This report underscores the need for further research on effective management programs for Ascochyta blight. References: (1) B. Bayaa and W. Chen. Compendium of Chickpea and Lentil Diseases and Pests The American Phytopathological Society, St. Paul, MN, 2011. (2) E. Punithalingam and P. Holliday. Page 337 in: CMI Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, UK, 1972.

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First Report of Citrus Alternaria Brown Spot Caused by Alternaria alternata in Taiwan

Plant Disease ◽

10.1094/pdis-12-14-1341-pdn ◽

2015 ◽

Vol 99 (12) ◽

pp. 1864-1864 ◽

Cited By ~ 1

Author(s):

H. F. Ni ◽

C. W. Huang ◽

H. R. Yang

Keyword(s):

Alternaria Alternata ◽

Brown Spot ◽

First Report ◽

Alternaria Brown Spot

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First Report of Daylily Leaf Streak Caused by Kabatiella microsticta in China

Plant Disease ◽

10.1094/pdis-04-12-0381-pdn ◽

2012 ◽

Vol 96 (10) ◽

pp. 1579-1579 ◽

Cited By ~ 1

Author(s):

Q. R. Bai ◽

S. Han ◽

Y. Y. Xie ◽

R. Dong ◽

J. Gao ◽

...

Keyword(s):

Morphological Characteristics ◽

Its Region ◽

The United States ◽

Control Treatment ◽

Conidial Suspension ◽

First Report ◽

Perennial Plant ◽

Leaf Spots ◽

Plastic Bags ◽

Hemerocallis Citrina

Daylily (Hemerocallis spp.) is an herbaceous, perennial plant, cultivated for its flowers. Daylily is sold in Asian markets as fresh or dried flowers (the flowers of some species, e.g., Hemerocallis citrina, are edible) or as the corm, which is used for medicinal purposes. In June 2011, daylily leaf streak was found in a nursery of Jilin Agricultural University, Jilin Province, China. Symptoms included water-soaked, irregular spots along the leaf midvein that turned orange to reddish brown and eventually enlarged to coalesce into extensive, necrotic streaks along the length of the leaf, as previously reported (2). Heavily infected leaves often withered and died. Four isolates were recovered from necrotic tissue of leaf spots and cultured on potato dextrose agar (PDA) at 25°C. All colonies were initially cream to peach colored and appeared slimy. With the maturation of the culture, the colonies became dark brown to black with sparse aerial hyphae. Blastic conidia formed simultaneously on intercalary or terminal, undifferentiated conidiogenous cells, and were scattered in dense sections on culture surface. When the conidia dropped from conidiogenous cell, an indistinct scar or a denticle remained. Conidia were hyaline, one-celled, smooth, ellipsoidal, and variable in size (2.73 to 6.01 × 8.45 to 19.36 μm), and all morphological characteristics were consistent with Kabatiella microsticta Bubak (syn. Aureobasidium microstictum; 2,4). The internal transcribed spacer (ITS) region of the nuclear rDNA was amplified using primers ITS4/ITS5 (1). ITS (534 bp) was identical among all four isolates (GenBank Accession No. HE798117) and 100% identical to that of K. microsticta CBS 114.64 (FJ150873). Pathogenicity was confirmed by spraying 20 seedlings of daylily, propagated in tissue-culture medium, with a conidial suspension (106 conidia/ml) of each isolate. A second set of 20 seedlings was sprayed with the same volume of sterile water as the noninoculated control treatment. Plants were grown in the greenhouse at 20 to 25°C and were covered with plastic bags to maintain humidity on the foliage for 72 h. After 5 days, the foliar symptoms described earlier for the field plants appeared on the leaves, whereas the control plants remained healthy. K. microsticta was reisolated from the leaf spots of all 20 inoculated plants. Leaf streak is the most destructive disease of daylily, and was previously reported in Japan and the United States (Illinois, Kentucky, Mississippi, Louisiana, Pennsylvania, Maryland, Virginia, Florida, North Carolina, and Georgia) (3). To our knowledge, this is the first report of the disease caused by K. microsticta in China. References: (1) D. E. L. Cooke et al. Mycol. Res. 101:667, 1997. (2) E. J. Hermanides-Nijhof. Stud. Mycol. 15:153, 1977. (3) R. M. Leahy et al. Plant Pathology Circular No. 376, 1996. (4) P. Zalar et al. Stud. Mycol. 61:21, 2008.

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First Report of Alternaria Brown Spot of Citrus in Spain

Plant Disease ◽

10.1094/pdis.2000.84.9.1044b ◽

2000 ◽

Vol 84 (9) ◽

pp. 1044-1044 ◽

Cited By ~ 20

Author(s):

A. Vicent ◽

J. Armengol ◽

R. Sales ◽

J. García-Jiménez ◽

F. Alfaro-Lassala

Keyword(s):

External Surface ◽

Morphological Characteristics ◽

Brown Spot ◽

Economic Losses ◽

Sterile Water ◽

Eastern Province ◽

First Report ◽

Alternaria Brown Spot ◽

Young Leaves ◽

Pathogenicity Tests

In 1998, a new disease of Fortune mandarin trees was detected in orchards in the eastern province of Valencia. This is one of the most important late-maturing cultivars grown in Spain. Symptoms were typical of Alternaria brown spot of citrus (2). Young leaves showed brown necrotic and irregular blighted areas with characteristic yellow halos. The necrosis had a tendency to follow the veins. On fruits, symptoms included light brown, slightly depressed spots to circular and dark brown areas on the external surface. Infected young fruits and leaves often fell and the mature fruits were unmarketable due to lesions, resulting in important economic losses. Isolations on potato dextrose agar supplemented with 0.5 mg/ml of streptomycin sulfate (PDAS) from affected leaves and fruits consistently yielded Alternaria alternata (Fr.:Fr.) Keissl., which was identified based on conidial morphological characteristics. Pathogenicity tests were conducted using 15 isolates from fruit and leaves by inoculating detached immature Fortune leaves with a sterile water suspension of 5 × 105 conidia per ml. Drops of this suspension (40 μl each) were placed on the lower surfaces of each leaflet using four leaves per isolate. Leaves were incubated in a moist chamber in the dark at 27°C (1). After 48 h, most of these isolates caused necrotic lesions on the leaves similar to those observed in the field, and the fungus was reisolated, confirming Koch's postulates. In 1999, the fungus spread to other citrus-growing areas, and to date the disease has been detected affecting Fortune and Nova mandarins and Minneola tangelo. This is the first report of Alternaria brown spot of citrus in Spain. References: (1) K. Kohmoto et al. Phytopathology 81:719, 1991. (2) J. O. Whiteside. Plant Dis. Rep. 60:326, 1976.

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First Report of Myrothecium Leaf Spot of Hemionitis arifolia Caused by Myrothecium roridum in China

Plant Disease ◽

10.1094/pdis-02-11-0124 ◽

2011 ◽

Vol 95 (8) ◽

pp. 1030-1030 ◽

Cited By ~ 4

Author(s):

Y. X. Zhang ◽

J. H. Huang ◽

M. M. Xiang

Keyword(s):

Leaf Spot ◽

Ornamental Plants ◽

Morphological Characteristics ◽

Control Measures ◽

Control Treatment ◽

Chinese Isolate ◽

Single Spore ◽

First Report ◽

Leaf Spots ◽

Myrothecium Roridum

Hemionitis arifolia (Burm.) Moore. was grown commercially as an ornamental plant in China. In January 2010, a new foliar disease with typical leaf spot symptoms was observed on H. arifolia in Dongguan City, Guangdong Province. Approximately 10% of the plants in the Dongguan nursery were affected. Leaf spots were circular to subcircular, dark brown, with distinct concentric zones, and ranged from 10 to 20 mm in diameter. Lesions developed mostly on the lower leaves and black sporodochia with white mycelial tufts were produced mostly in older lesions under high humidity. Single-spore isolates from lesions plated on potato dextrose agar (PDA) produced white, floccose colonies and dark green-to-black sporodochia. Colonies reached 60 mm on PDA at 25°C after 14 days. Conidiophores branched repeatedly. Conidiogenous cells in whorls of two to six on ultimate branches were hyaline, cylindrical, and 13 to 20 × 1.2 to 1.8 μm. Conidia were hyaline, cylindrical, mostly with both rounded ends, occasionally one blunt end, and mean size was 6.1 (4.5 to 7.0) × 2.3 (1.8 to 3.0) μm. These characteristics were consistent with the descriptions of Myrothecium roridum Tode ex Fr. (2–4). The internal transcribed spacer regions including ITS1, ITS2, and the 5.8S rRNA of one isolate were PCR amplified and sequenced. A BLAST search in GenBank revealed highest similarity (99%) to M. roridum sequences from isolates collected from Germany (Accession Nos. AJ302001.1 and AJ301995.1). The M. roridum sequence from the Chinese isolate was submitted to GenBank (Accession No. JF343832). To confirm pathogenicity, five leaves on five H. arifolia plants were inoculated with 5-mm mycelial plugs from the periphery of 7-day-old cultures; sterile PDA plugs were used as the control treatment. Plants were covered with plastic bags and incubated in a growth chamber at 28°C. Necrotic lesions appeared 2 to 3 days after inoculation and the symptoms described above were observed after 7 days on all inoculated leaves, whereas sterile PDA plugs did not produce any leaf lesion. The pathogen was reisolated from the inoculated leaves and confirmed to be M. roridum on the basis of morphological characteristics. There are approximately 271 hosts of M. roridum (1), including many ornamental plants such as salvia (2) and garden hydrangea (3). To our knowledge, this is the first report of Myrothecium leaf spot on H. arifolia. Because the disease caused damage to the foliage and reduced the ornamental value of H. arifolia plants, control measures may need to be implemented for production of this species in ornamental nurseries. References: (1) D. F. Farr and A. Y. Rossman. Fungal Databases. Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrived from http://nt.ars-grin.gov/fungaldatabases/ , 6 February 2011. (2) J. A. Mangandi et al. Plant Dis. 91:772, 2007. (3) M. T. Mmbaga et al. Plant Dis. 94:1266, 2010. (4) M. Tulloch. Mycol. Pap. No. 130. CMI, Wallingford, UK, 1972.

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