scholarly journals First Report of Glomerella Leaf Spot (Glomerella cingulata) of Apple in the United States

Plant Disease ◽  
1999 ◽  
Vol 83 (11) ◽  
pp. 1074-1074 ◽  
Author(s):  
E. González ◽  
T. B. Sutton
Keyword(s):  
Leaf Spot ◽  
The United States ◽  
Distilled Water ◽  
Glomerella Cingulata ◽  
Pathogenicity Tests ◽  
Petri Dishes ◽  
Glomerella Leaf Spot ◽  
Microscope Slides ◽  
Mycelial Suspension ◽  
Severe Leaf

In August 1998, severe leaf spot, resulting in extensive defoliation, was observed on cv. Gala apple trees in two orchards in eastern Tennessee. Symptoms were similar to those reported in Brazil for Glomerella leaf spot on Gala (1), and Glomerella cingulata (Stoneman) Spauld. & H. Schrenk was observed fruiting in lesions. Single-ascospore isolates were obtained by placing individual perithecia from different lesions on microscope slides in a drop of sterilized distilled water. Perithecia were crushed, and the spore and mycelial suspension was distributed on the surface of petri dishes containing acid-water agar (AWA). Petri dishes were incubated at 24°C in light for 24 h. Germinated ascospores were transferred to petri dishes containing AWA. Cultures were transferred to potato dextrose agar and grown at 24°C in light for 14 days to induce sporulation. Four isolates (TN-1A, TN-1B, TN-2A, and TN-2B) were selected for pathogenicity tests. Three virulent isolates from Brazil (FK6, R-11, and 2VGE) also were included. Trees of apple cvs. Gala and Golden Delicious were placed in humidity chambers before inoculation. After 24 h, shoots on three trees of each cultivar were sprayed with an aqueous spore suspension of each isolate (1× 105 spores per ml) and maintained at 100% relative humidity (RH) and ≈22°C for 2 days. Shoots on three trees sprayed with sterilized distilled water and maintained at 100% RH served as a control. All isolates from Brazil and isolates TN-1A and TN-1B caused symptoms characteristic of Glomerella leaf spot on both cultivars after 2 days. Five days after inoculation disease severity on each leaf was visually rated on a scale of 0 to 5 (where 0 = no lesions and 5 = 25 to 50% of leaf surface covered with lesions). FK6 and R-11 were the most aggressive isolates on both cultivars. 2VGE and TN-1B were the least aggressive isolates. Reference: (1) T. B. Sutton and R.M. Sanhueza. Plant Dis. 82:267, 1998.

scholarly journals First Report of Glomerella Leaf Spot of Apple Caused by Glomerella cingulata in China

Plant Disease ◽  
2012 ◽  
Vol 96 (6) ◽  
pp. 912-912 ◽  
Author(s):  
C. X. Wang ◽  
Z. F. Zhang ◽  
B. H. Li ◽  
H. Y. Wang ◽  
X. L. Dong
Keyword(s):  
Leaf Spot ◽  
Morphological Characteristics ◽  
The United States ◽  
Causal Agent ◽  
Control Measures ◽  
Effective Control ◽  
Initial Symptom ◽  
Glomerella Cingulata ◽  
Golden Delicious ◽  
Glomerella Leaf Spot

A new destructive apple disease, causing black spots and necrotic lesions on leaves and defoliation on cvs. Gala and Golden Delicious (Malus × domestica Borkh.), was observed in August 2011 in Fengxian, Jiangsu Province, China. More than 90% of trees of those cultivars in the area were defoliated by the disease and almost no leaves were left on trees before harvest. The disease was similar to Glomerella leaf spot reported first in Brazil in 1988 (2) and in the United States in 1998 (1) on cvs. Gala and Golden Delicious. The initial symptom was small black lesions on leaves. Above 30°C, the lesions developed quickly and grew to 2 to 3 cm, with a blurred edge. Diseased leaves became dark and were shed. At lower temperatures, the black lesions stopped enlarging after 5 to 6 days and formed large necrotic spots with clear edges; these leaves gradually grew yellow and were shed. When incubated at 30°C and 100% relative humidity for 1 to 2 days, the black lesions produced a mass of saffron-yellow conidia. On fruit, the pathogen only caused circular, necrotic, sunken, red-bordered lesions 2 to 3 mm in diameter, which was different from bitter rot. Three monospored cultures were isolated from diseased leaves and new conidia were obtained from isolates. The colony, with abundant mycelium, was white but turned gray to black. Conidia were 12 to 17 × 5 to 7 μm, and were cylindrical with rounded ends. After germination, conidia formed appressoria, oval, or circular cells with black thick walls 7 to 12 × 5 to 7 um. Based on morphological characteristics, the pathogen was putatively identified as Glomerella cingulata. The conidia were inoculated in vitro on leaves of cvs. Gala and Fuji by dripping a suspension of about 104 conidia/ml of water onto upper leaf surfaces. Dark necrotic lesions were observed on all inoculated Gala leaves, which were similar to those observed in orchards, after 4 days incubation in a chamber at 30°C with 100% humidity. Only small black lesions, about 1 to 2 mm in diameter, were observed on Fuji leaves. No symptoms developed on leaves inoculated with distilled water. The internal transcribed spacer (ITS) region of ribosomal DNA and part of the 18S and 28S ribosomal RNA of the three isolates were amplified with the universal primers ITS1 (5′-TCCGTAGGTGAACCTGCGG-3′) and ITS4 (5′-CCTCCGCTTATTGATATGC-3′). The amplified ITS sequences confirmed that the three isolates belonged to the same species, with only one base pair variation among sequences. The nucleotide sequence of isolate 1 and 2 was deposited in GenBank (JN714400 and JN714401). BLAST analysis showed that the sequence had 99% homology with the sequence of G. cingulata (EU008836), the causal agent of Glomerella leaf spot. However, the sequence of isolate 1 had 100% homology with that of G. cingulata (HQ845103.1) isolated from walnut in Shandong, China, while the sequence of isolate 2 had 100% homology with that of G. cingulata (HM015004.1) isolated from sweet pepper in Taiwan. Results suggested the disease is Glomerella leaf spot and the causal agent is G. cingulata. The disease will eliminate sensitive apple cultivars, such as Gala, from wet, warm production areas if effective control measures are not developed within a few years. To our knowledge, this was the first finding of the disease in China and will provide useful information for developing effective control strategies. References: (1) E. González and T. B. Sutton. Plant Dis. 83:1074, 1999. (2) T. B. Sutton and R. M. Sanhueza. Plant Dis. 82:267, 1998.

scholarly journals First Report of Leaf Spot Caused by Corynespora cassiicola on Kiwifruit (Actinidia chinensis) in China

Plant Disease ◽  
2014 ◽  
Vol 98 (11) ◽  
pp. 1586-1586 ◽  
Author(s):  
G. Q. Yuan ◽  
Y. L. Xie ◽  
D. C. Tan ◽  
Q. Q. Li ◽  
W. Lin
Keyword(s):  
Leaf Spot ◽  
Morphological Characteristics ◽  
Its Region ◽  
Corynespora Cassiicola ◽  
Detached Leaf Assay ◽  
Detached Leaf ◽  
Concentric Pattern ◽  
Pathogenicity Tests ◽  
Petri Dishes ◽  
Whole Plants

Kiwifruit (Actinidia) is a common fruit cultivated in many countries. Actinidia deliciosa and A. chinensis are two commercially important kiwifruit species. Over 70,000 ha are grown annually in China. In 2012, a leaf spot disease of A. chinensis was observed in several orchards in Leye County (106°34′ E, 24°47′ N), Guangxi Zhuang Autonomous Region, China. The disease mainly damaged the leaves during the fruit development stage through to the maturity stage. Initially reddish-brown small lesions appeared on the leaves; later, typical symptoms were tan to taupe lesions surrounded by purple brown margins, nearly circular to irregular, 2 to 10 × 2.2 to 15.5 mm in diameter. Some lesions exhibited a concentric pattern. The lesions eventually coalesced, causing extensive leaf necrosis and defoliation. The fungus that sporulated from lesions had the following morphological characteristics: light brown conidiophores with slightly swollen apexes, light brown conidia formed singly or in acropetal chains, straight or curved, cylindrical to oblavate, 52.9 to 240.5 μm long (avg. 138.9 μm) and 5.3 to 13.6 μm wide (avg. 8.4 μm), 5 to 12 distoseptate, with a flat, darkened, and thickened hilum. These morphological characteristics corresponded with that of Corynespora cassiicola (Berk. & Curt.) Wei (1). To isolate the pathogen of the disease, small pieces of symptomatic foliar tissues, including young lesions, typical older lesions, and atypical older lesions with concentric pattern were surface sterilized with 75% ethanol for 30 to 60 s, disinfected in 0.1% HgCl2 for 1 min followed by washing with sterile water, plated on PDA, and incubated at 28°C for 7 to 10 days. Gray to dark gray colonies and conidia of C. cassiicola were observed. To validate the identity of the fungus, the sequence of the ITS region of one of the purified strains, LYCc-1, was determined. DNA was extracted from the isolate that was grown on PDA at 28°C for 4 days, and the ITS region was amplified using the universal primer pair ITS4/ITS5 (2). The double strand consensus sequence was submitted to GenBank (KJ747095) and had 99% nt identity with published sequences of C. cassiicola in GenBank (JN853778, FJ852574, and FJ852587). Pathogenicity tests were carried out on detached leaves in petri dishes in an incubator at 28°C and on whole plants in a glasshouse at 25 ± 3°C. The isolations did not produce enough conidia in pure culture, so mycelial discs were used in pathogenicity tests. For both assays, 60-day-old healthy kiwifruit leaves were inoculated with a 5-mm mycelial disc obtained from the periphery of a 5-day-old C. cassiicola strain (LYCc-1) grown on PDA. The PDA discs were placed on the leaf surface with their mycelial surface down and secured with sterile wet cotton. Controls consisted of leaves that were inoculated with sterile PDA discs. For the detached leaf assay, the leaves were placed on filter paper reaching water saturation in petri dishes, and for the whole plant assays the inoculated leaves were kept moist with intermittent water sprays for 48 h. Four leaves of each plant were inoculated with the isolate in both assays, and experiment was repeated twice. Eight inoculated leaves of the detached leaf assay all showed the first water soaked lesions 36 h after inoculation, followed by extensive leaf rot 72 h after inoculation, and yielded abundant conidia of C. cassiicola. Six out of eight leaves inoculated on whole plants showed the first lesions 5 days after inoculation, whereas control leaves remained healthy. Only C. cassiicola was re-isolated from the lesions in both assays, fulfilling Koch's postulates. This is the first report of leaf spot caused by C. cassiicola on kiwifruit in China. References: (1) M. B. Ellis. Dematiaceous Hyphomycetes. CMI, Kew, Surrey, UK, 1971. (2) T. J. White et al. In: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, 1990.

Differentiation of Isolates of Glomerella cingulata and Colletotrichum spp. Associated with Glomerella Leaf Spot and Bitter Rot of Apples Using Growth Rate, Response to Temperature, and Benomyl Sensitivity

2005 ◽  
Vol 6 (1) ◽  
pp. 6 ◽  
Author(s):  
Eugenia González ◽  
Turner B. Sutton
Keyword(s):  
Growth Rate ◽  
Leaf Spot ◽  
Molecular Diversity ◽  
Colletotrichum Gloeosporioides ◽  
Glomerella Cingulata ◽  
Optimum Growth Temperature ◽  
Bitter Rot ◽  
Colletotrichum Spp ◽  
Glomerella Leaf Spot ◽  
Response To Temperature

Cultural characteristics were investigated as a way to distinguish isolates of Glomerella cingulata and Colletotrichum spp. associated with Glomerella leaf spot and bitter rot of apples from those that cause only bitter rot. The growth rate, response to temperature, and benomyl sensitivity of 27 isolates of Glomerella cingulata, 12 isolates of Colletotrichum gloeosporioides, and 7 isolates of C. acutatum, collected from apple orchards located in the U.S. and Brazil and previously characterized based on morphology, vegetative compatibility, and mitochondrial DNA (mtDNA) haplotypes, were determined. These isolates represent the genetic and molecular diversity within isolates of C. gloeosporioides, C. acutatum, and G. cingulata from apples found in a previous study. Slower growth, lower optimum growth temperature, and less sensitivity to benomyl distinguished isolates of C. acutatum from isolates of G. cingulata and C. gloeosporioides. However, growth rate and benomyl sensitivity were not useful for distinguishing between G. cingulata and C. gloeosporioides or differentiating isolates of G. cingulata that cause leaf spot and bitter rot from those that only cause bitter rot. Accepted for publication 17 May 2005. Published 19 July 2005.

scholarly journals Characterization of Leaf Spot Pathogens from Several Spinach Production Areas in the United States

Plant Disease ◽  
2020 ◽  
Vol 104 (7) ◽  
pp. 1994-2004
Author(s):  
Bo Liu ◽  
Larry Stein ◽  
Kimberly Cochran ◽  
Lindsey J. du Toit ◽  
Chunda Feng ◽  
...  
Keyword(s):  
United States ◽  
South Carolina ◽  
Leaf Spot ◽  
The United States ◽  
Leaf Damage ◽  
Leaf Spots ◽  
Pathogenicity Tests ◽  
Agar Media ◽  
Production Areas

Leaf spot diseases have become a major concern in spinach production in the United States. Determining the causal agents of leaf spots on spinach, their prevalence and pathogenicity, and fungicide efficacy against these pathogens is vital for effective disease management. Spinach leaves with leaf spots were collected from Texas, California, Arizona, and South Carolina from 2016 to 2018, incubated in a moist chamber, and plated on potato dextrose and tryptic soy agar media. Fungal and bacterial colonies recovered were identified based on morphology and sequence analysis of the internal transcribed spacer rDNA and 16S rRNA, respectively. Two predominant genera were isolated: (i) Colletotrichum spp., which were identified to species based on sequences of both introns of the glutamate synthetase (GS-I) and glyceraldehyde-3-phosphate dehydrogenase (gapdh-I) genes; and (ii) Stemphylium spp., identified to species based on sequences of the gapdh and calmodulin (cmdA) genes. Anthracnose (Colletotrichum spinaciae) and Stemphylium leaf spot (Stemphylium vesicarium and S. beticola) were the predominant diseases. Additional fungi recovered at very limited frequencies that were also pathogenic to spinach included Colletotrichum coccodes, C. truncatum, Cercospora beticola, and Myrothecium verrucaria. All of the bacterial isolates were not pathogenic on spinach. Pathogenicity tests showed that C. spinaciae, S. vesicarium, and S. beticola caused significant leaf damage. The fungicides Bravo WeatherStik (chlorothalonil), Dithane F-45 (mancozeb), Cabrio (pyraclostrobin), and Merivon (fluxapyroxad and pyraclostrobin) were highly effective at reducing leaf spot severity caused by an isolate of each of C. spinaciae and S. vesicarium, when inoculated individually and in combination.

scholarly journals Three New Fungal Leaf Spot Diseases of Spinach in the United States and the Evaluation of Fungicide Efficacy for Disease Management

Plant Disease ◽  
2021 ◽  
pp. PDIS-04-20-0918
Author(s):  
Bo Liu ◽  
Larry Stein ◽  
Kimberly Cochran ◽  
Lindsey J. du Toit ◽  
Chunda Feng ◽  
...  
Keyword(s):  
United States ◽  
Sequence Analysis ◽  
Leaf Spot ◽  
The United States ◽  
Leaf Spots ◽  
Fungicide Efficacy ◽  
Windblown Sand ◽  
Pathogenicity Tests ◽  
Spinach Leaf ◽  
Production Areas

Leaf spot diseases of spinach, caused by Colletotrichum spinaciae, has become a major production constraint in several production areas, including Texas, in recent years. Leaf spot symptoms were observed in several fields in Texas in 2016 and 2017, with typical anthracnose-like symptoms and leaves with small, circular, and sunken lesions that appeared similar to injury from windblown sand. The lesions were plated on potato dextrose agar, from which fungal cultures were recovered. The fungi were identified based on morphology and sequence analysis of the introns of glutamate synthetase and glyceraldehyde-3-phosphate dehydrogenase (for isolates determined to be Colletotrichum spp.) and the internal transcribed spacer ribosomal DNA (for isolates determined to be Myrothecium spp.). Based on foliar symptoms, fungal colony and spore morphology, pathogenicity tests of fungal isolates on the spinach cultivar ‘Viroflay’, and DNA sequence analysis of the isolates, the symptoms on spinach leaves for two sets of samples were caused by Colletotrichum coccodes and Colletotrichum truncatum, and leaf spots resembling damage from windblown sand were caused by Myrothecium verrucaria. This is the first report of spinach leaf spot diseases caused by C. coccodes, C. truncatum, and M. verrucaria in the United States. C. coccodes and C. truncatum caused severe symptoms on the spinach cultivar ‘Viroflay’, whereas M. verrucaria caused symptoms of intermediate severity. Fungicide efficacy tests demonstrated that chlorothalonil, mancozeb, pyraclostrobin, fluxapyroxad + pyraclostrobin, and penthiopyrad were completely effective at preventing leaf spots caused by any of these pathogens when applied 24 h before inoculation of ‘Viroflay’ plants in greenhouse trials.

scholarly journals Root Rot of Hydroponically Grown Lettuce Caused by Phytophthora drechsleri in Mexico

Plant Disease ◽  
2009 ◽  
Vol 93 (10) ◽  
pp. 1077-1077
Author(s):  
G. Rodríguez-Alvarado ◽  
M. I. Pérez-Cáliz ◽  
K. B. Caudillo-Ruiz ◽  
E. Garay-Serrano ◽  
R. Rodríguez-Fernández ◽  
...  
Keyword(s):  
Root Rot ◽  
Morphological Characteristics ◽  
The United States ◽  
Soil Extract ◽  
Internal Transcribed Spacers ◽  
Distilled Water ◽  
Lettuce Seedling ◽  
Phytophthora Drechsleri ◽  
Pathogenicity Tests ◽  
Hydroponically Grown

During March of 2008, bibb lettuce (Lactuca sativa L.) plants with severe wilting and root rot were observed in a commercial liquid-hydroponic greenhouse in Guanajuato, Mexico. By July of that year, the disease affected most plants in the facility. A Phytophthora sp. was consistently isolated from diseased roots on potato carrot agar. Several Phytophthora isolates were morphologically characterized. Sporulation was achieved by placing colonized disks of clarified V8 juice agar (V8A) into nonautoclaved soil extract (10 g avocado soil/1,000 ml distilled water, stirred for 3 h, and filtered). Sporangia were persistent, nonpapillate, and 40 to 58 μm long × 30 to 40 μm wide. External and internal proliferation was observed. Hyphal swellings were predominantly rounded. Oospores were not observed. The isolates grew on V8A at 35°C. Pathogenicity tests were conducted twice by utilizing a representative isolate (AC1) on bibb lettuce seedlings (10 replicates per experiment). Seeds were placed on sterile, water-soaked paper in petri dishes. After 10 days, each lettuce seedling was placed into a tube containing approximately 2 ml of sterile distilled water and 2,000 zoospores. Control plants were placed in tubes with water only. Plants were incubated for 7 days in a moist chamber at 25°C. Symptoms of wilting and root necrosis were observed 2 to 3 days after inoculation. All plants were dead 5 to 7 days after inoculation. A Phytophthora sp. was always isolated from the roots of inoculated plants. Control plants remained healthy. The pathogen was identified as Phytophthora drechsleri Tucker according to morphological characteristics. To confirm the identity of the pathogen, sequences of the internal transcribed spacers (ITS) were obtained from three representative isolates. The ITS sequences that were obtained shared 100% homology to several strains of P. dreschleri, including isolates from cucurbits (GenBank Accession No. AF228097). The ITS sequence was deposited in NCBI as Accession No. FJ790770. P. cryptogea and P. dreschleri have been reported as causing root rot on lettuce grown hydroponically in the United States and Korea (1,2). To our knowledge, this is the first report of P. drechsleri causing root rot on lettuce in Mexico. References: (1) H. J. Jee et al. Plant Pathol. J. 17:311, 2001. (2) A. R. Linde et al. Plant Dis. 74:1037, 1990.

scholarly journals First Report of Colletotrichum karstii Causing Glomerella Leaf Spot on Apple in Santa Catarina State, Brazil

Plant Disease ◽  
2014 ◽  
Vol 98 (1) ◽  
pp. 157-157 ◽  
Author(s):  
A. C. Velho ◽  
M. J. Stadnik ◽  
L. Casanova ◽  
P. Mondino ◽  
S. Alaniz
Keyword(s):  
United States ◽  
Leaf Spot ◽  
Management Practices ◽  
Eastern China ◽  
The United States ◽  
Subtropical Climate ◽  
Santa Catarina ◽  
First Report ◽  
Glomerella Leaf Spot ◽  
Santa Catarina State

Glomerella leaf spot (GLS) is an emerging disease of apple (Malus domestica Borkh.) that has been reported in regions with a humid subtropical climate, such as southern Brazil, the southeastern United States, and more recently eastern China. GLS is favored by high humidity and temperatures between 23 and 28°C and can result in extensive defoliation when the severity is high. The disease was first reported 1988 in Brazil on cvs. Gala and Golden Delicious in orchards in Paraná State (3), but now is widespread in the country's producing areas. Two Colletotrichum species of different complexes have been associated with GLS, C. gloeosporioides (Penz.) Penz. & Sacc. and its sexual stage Glomerella cingulata (Stoneman) Spaulding & Scherenk, and C. acutatum J. H. Simmonds, although GLS is more commonly associated with the former. In the summer of 2012, necrotic spots were observed on apple leaves (cv. Gala) in Santa Catarina state, Brazil. The first symptoms were reddish-brown spots, evolving to small necrotic lesions 1 to 10 mm long at 7 to 10 days after symptoms were first noted. Pure cultures were obtained by monosporic isolation and grown on PDA at 25°C and with a 12-h photoperiod under fluorescent light. The color of the upper surface of the colony varied from white to gray and the reverse was pink. The conidia length and width ranged from 9.1 to 17.1 μm ([Formula: see text] = 12.8) and from 2.9 to 6.8 μm ([Formula: see text] = 4.9), respectively, and were cylindrical, hyaline, and straight. After germination, conidia formed oval or circular appressoria measuring between 4.0 and 10.0 ([Formula: see text] = 6.3) × 3.0 and 9.0 ([Formula: see text] = 5.7). To confirm pathogenicity, susceptible apple seedlings (cv. Gala) were inoculated with a suspension of 1 × 106 conidia.mL–1. Seedlings sprayed with sterile distilled water served as controls. Seedlings were incubated in a moist chamber at 25°C and 100% RH for 48 h. First symptoms appeared 4 days after inoculation and were similar to those observed in the field. The control treatment remained symptomless. The pathogen was reisolated from lesions, confirming Koch's postulates. Fungus was molecularly characterized by sequencing the internal transcribed spacer (ITS) rDNA and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and the nucleotide sequence was deposited in the GenBank database (KC876638 and KC875408). C. karstii, considered as part of the C. boninense species complex (1), was identified with 100% sequence homology. This species was previously reported in China (4), Thailand, and the United States, affecting Orchidaceae plants (2), and in Brazil it has been reported affecting Carica papaya, Eugenia uniflora, and Bombax aquaticum (1). To our knowledge, this is the first report of C. karstii causing GLS on apple in Brazil. The development of pre-harvest management practices may be warranted to manage this disease. References: (1) U. Damm et al. Stud. Mycol. 73:1, 2012. (2) I. Jadrane. Plant Dis. 96:1227, 2012. (3) T. B. Sutton. Plant Dis. 82:267, 1998. (4) Y. Yang. Cryptogamie Mycologie 32:229, 2011.

scholarly journals The First Report of Leaf Spots in Aloe vera Caused by Nigrospora oryzae in China

Plant Disease ◽  
2013 ◽  
Vol 97 (9) ◽  
pp. 1256-1256 ◽  
Author(s):  
L. F. Zhai ◽  
J. Liu ◽  
M. X. Zhang ◽  
N. Hong ◽  
G. P. Wang ◽  
...  
Keyword(s):  
Leaf Spot ◽  
Aloe Vera ◽  
Kentucky Bluegrass ◽  
The United States ◽  
Leaf Spot Disease ◽  
First Report ◽  
Spot Disease ◽  
Leaf Spots ◽  
Pathogenicity Tests ◽  
Nigrospora Oryzae

Aloe vera L. var Chinese (Haw) Berg is a popular ornamental plant cultivated worldwide, whose extracts are used in cosmetics and medicine. Aloe plants are commonly affected by leaf spot disease caused by Alternaria alternata in Pakistan, India, and the United States (1). An outbreak of Alternaria leaf spot recently threatened aloe gel production and the value of ornamental commerce in Louisiana (1). During the summer of 2011, leaf spot symptoms were observed on A. vera plants growing in several greenhouses and ornamental gardens in Wuhan, Hubei Province, China. In two of the greenhouses, disease incidence reached 50 to 60%. The initial symptoms included chlorotic and brown spots that expanded to 2 to 4 mm in diameter and became darker with age. Lesions also developed on the tips of 30 to 50% of the leaves per plant. In severe infections, the lesions coalesced causing the entire leaf to become blighted and die. In September of 2012 and February of 2013, 10 symptomatic A. vera leaves were collected randomly from two greenhouses and gardens in Wuhan. A fungus was consistently recovered from approximately 80% of the tissue samples using conventional sterile protocols, and cultured on potato dextrose agar (PDA). The colonies were initially white, becoming grey to black, wool-like, and growing aerial mycelium covering the entire petri dish (9 cm in diameter) plate within 5 days when maintained in the dark at 25°C. The conidia were brown or black, spherical to subspherical, single celled (9 to 13 μm long × 11 to 15 μm wide), borne on hyaline vesicles at the tip of conidiophores. The conidiophores were short and rarely branched. These colonies were identified as Nigrospora oryzae based on the described morphological characteristics of N. oryzae (2). Genomic DNA was extracted from a representative isolate, LH-1, and the internal transcribed spacer region was amplified using primer pair ITS1/ITS4 (3). A 553-bp amplicon was obtained and sequenced. The resulting nucleotide sequence (GenBank Accession No. KC519728) had a high similarity of 99% to that of strain AHC-1 of N. oryzae (JQ864579). Pathogenicity tests for strain LH-1 were conducted in triplicate by placing agar pieces (5 mm in diameter) containing 5-day-old cultures on A. vera leaves. Four discs were placed on each punctured surface of each leaf. Noncolonized PDA agar pieces were inoculated as controls. Leaves were placed in moist chambers at 25°C with a 12-h photoperiod. After 3 days, the inoculated leaves showed symptoms similar to those observed in the greenhouses. N. oryzae was reisolated from these spots on the inoculated leaves. No visible symptoms developed on the control leaves. The pathogenicity tests were performed twice with the same results. Based on the results, N. oryzae was determined as a pathogen responsible for the leaf spots disease on A. vera. N. oryzae has been described as a leaf pathogen on fig (Ficus religiosa), cotton (Gossypium hirsutum) and Kentucky bluegrass (Poa pratensis) (4), and to our knowledge, this is the first report of N. oryae causing leaf spot disease on A. vera worldwide. References: (1) W. L. da Silva and R. Singh. Plant Dis. 86:1379, 2012. (2) M. B. Ellis. Dematiaceous Hyphomycetes, CAB, Kew, Surrey, England, 1971. (3) T. J. White et al. PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, 1990. (4) L. X. Zhang et al. Plant Dis. 96:1379, 2012.

scholarly journals First Report of Gray Leaf Spot on Perennial Ryegrass Turf in California

Plant Disease ◽  
2002 ◽  
Vol 86 (1) ◽  
pp. 75-75 ◽  
Author(s):  
W. Uddin ◽  
G. Viji ◽  
L. Stowell
Keyword(s):  
United States ◽  
Perennial Ryegrass ◽  
Leaf Spot ◽  
Disease Incidence ◽  
The United States ◽  
Gray Leaf Spot ◽  
Water Soluble ◽  
Distilled Water ◽  
First Report ◽  
Polyethylene Bags

Gray leaf spot of perennial ryegrass (Lolium perenne L.) turf was first reported in the United States in 1991. The disease epidemic was primarily confined to golf course fairways in southeastern Pennsylvania (1). Subsequently, moderate to severe outbreaks of gray leaf spot occurred in perennial ryegrass fairways and roughs in numerous locations throughout the eastern and midwestern United States. In August 2001, a serious decline of perennial ryegrass turf was observed in a bermudagrass (Cynodon dactylon (L.) Pers) baseball field in Dodger Stadium in Los Angeles, CA, that had been overseeded with perennial ryegrass. The bermudagrass turf was not affected. The perennial ryegrass turf developed necrotic lesions that resulted in blighting of leaf blades. In laboratory assays, Pyricularia grisea (Cooke) Sacc., was consistently isolated from symptomatic ryegrass blades from turf samples collected from the site. Of the 12 P. grisea isolates collected from the assayed leaf blades, five isolates were selected for a pathogenicity assay. Twenty-five ‘Legacy II’ perennial ryegrass plants were grown from seeds in 4 × 4 in.-plastic pots, (10 × 10 cm) which were filled to 1 cm below the rim with granular calcine clay medium (Turface MVP, Allied Industrial Material Corp., Buffalo Grove, IL). Three weeks after seeding, plants were fertilized with a water-soluble 20-20-20 N-P-K fertilizer (1.3 g/liter of water) once per week. Treatments (isolates of P. grisea and a control) were arranged as a randomized complete block design with five replications. Five-week-old plants were sprayed with an aqueous suspension of P. grisea conidia (≈5 × 104 conidia per ml of sterilized distilled water with 0.1% Tween 20) using an atomizer until the leaves were completely wet. Plants sprayed with sterilized distilled water served as the control. After inoculation, individual pots were covered with clear polyethylene bags and placed in a controlled environment chamber maintained at 28°C and continuous fluorescent light (88 μE m-2 s-1). Four days after inoculation, necrotic lesions (<2 mm diameter) developed on ryegrass blades inoculated with each isolate of P. grisea. Lesions did not develop on leaves of control plants. Seven days after inoculation, the polyethylene bags were removed, and 50 symptomatic blades from each pot were collected, and disease incidence (percent infected leaves) and severity (index 0 to 10; 0 = none, 10 = >90% of the leaf blade necrotic ) were assessed. P. grisea was isolated from symptomatic leaves of plants inoculated with the fungus. Disease incidence and severity on inoculated plants were 92 to 96% and 8.8 to 10, respectively. There were no significant differences in disease incidence and severity (P = 0.05) among the isolates of P. grisea included in the test. To our knowledge, this is the first report of gray leaf spot of perennial ryegrass turf in California. Reference: (1) P. J. Landschoot and B. F. Hoyland. Plant Dis. 76:1280, 1992.

scholarly journals First Report of Leaf Spot on Japanese Plum Caused by an Alternaria sp. in Korea

Plant Disease ◽  
2005 ◽  
Vol 89 (3) ◽  
pp. 343-343 ◽  
Author(s):  
Youngjun Kim ◽  
Hyang Burm Lee ◽  
Seung Hun Yu
Keyword(s):  
Leaf Spot ◽  
Morphological Characteristics ◽  
The United States ◽  
Conidial Suspension ◽  
First Report ◽  
Japanese Plum ◽  
Leaf Spots ◽  
Causal Fungus ◽  
Pathogenicity Tests ◽  
Alternaria Sp

Japanese plum (Prunus salicina Lindley) is a deciduous tree in the family Rosaceae. In Korea, this plant is widely distributed in orchards as an important stone fruit as well as in gardens as an ornamental tree because of their abundant white blossoms. Every September to November since 2001, leaf spots were observed on Japanese plum in a garden in Cheongyang, Chungnam District, Korea. Early symptoms consisted of small, brown spots that were 2 to 5 mm in diameter. Later, the leaf lesions became circular or irregular, dark brown, expanded to 15 mm in diameter, and resulted in discoloration with necrosis on twisted leaves that was followed by defoliation. In November, older lesions sometimes appeared blackish brown as sporulation occurred on the lesions. The causal fungus was isolated from diseased leaves and cultured on potato dextrose agar. A culture has been placed in the CABI Herbarium (IMI Accession No. 387139). Conidial dimension averaged 34 × 12 μm. On the basis of morphological characteristics of conidia and conidiophores, the causal fungus was identified as a small-spored species of Alternaria as described by E. G. Simmons (1). Pathogenicity tests were conducted by inoculating slightly wounded and nonwounded leaves with a conidial suspension adjusted to 1 × 106 conidia/ml. Four leaves per each experiment were either wounded or not and inoculated with a spore suspension. The eight leaves were placed in a moist chamber at 25°C. After 6 to 10 days, small brown spots appeared on 87% of the wounded and nonwounded leaves. Control leaves sprayed with distilled water did not develop any symptoms. The causal fungus was consistently reisolated from the leaf spots. Results from pathogenicity tests were similar in a repeated test. It is possible that small-spored Alternaria spp. isolates are host specific (2). Eight Alternaria spp., including A. alternata, A. tenuis, A. tenuissima, and A. citri, have been found to cause black spot on fifteen Prunus spp. in China, Japan, Hong Kong, Libya, Mexico, Australia, and the United States (2). Further studies on the host-specific toxin production, geographical distribution, and host ranges for the species of Alternaria isolated from Japanese plum are in progress. To our knowledge, this is the first report of leaf spot on Japanese plum (P. salicina) caused by a small-spored Alternaria sp. in Korea. References: (1) E. G. Simmons. Mycotaxon 55:79, 1995. (2) K. Inoue and H. Nasu. J. Gen. Plant Pathol. 66:18, 2002.

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