scholarly journals First report of Colletotrichum siamense causing anthracnose on Erythrina crista-galli in China

Plant Disease ◽  
2020 ◽  
Author(s):  
Min Li ◽  
Zhaoyin Gao ◽  
Xiaoyu Hong ◽  
Zhang Shao Gang ◽  
Chao Zhao ◽  
...  
Keyword(s):  
Leaf Spot ◽  
Phylogenetic Analyses ◽  
Conidial Suspension ◽  
Disease Symptoms ◽  
First Report ◽  
Brown Center ◽  
Detached Leaves ◽  
Leaf Tissues ◽  
Pathogenicity Tests ◽  
White Mycelium

Erythrina crista-galli L. (Fabaceae) is a popular ornamental plant in tropical and subtropical regions of South Asia. In October 2019, anthracnose-like lesions were observed on the leaves of E. crista-galli planted in Haikou, China. 5-30% of leaves were infected. At first, the circular spots of 1-2 mm in diameter were reddish-brown on the leaves, and then enlarged to circular, subcircular or irregular spots with reddish-brown center and surrounded by a diffuse yellow margin. Neighboring spots sometimes coalesced. Under continuously wet or humid conditions, the lesions expanded quickly, and became gray, subcircular or irregular spots covered by grayish-white mycelium and orange-pink conidial masses. Diseased leaves eventually fell off the trees. To identify the pathogen, diseased leaves were sampled from four gardens. Leaf tissues (5×5 mm) were cut from the margins of typical symptomatic lesions, surface-sterilized in 1% sodium hypochlorite for 1 min, plated on potato dextrose agar (PDA) medium, and incubated at 28.0±0.5℃ in the dark. Similar fungal colonies were obtained from all plated tissues after 3 days. The single-conidium colonies of all isolates were white to pale gray and cottony with visible orange conidial masses. Conidia were one-celled, aseptate, hyaline, straight, cylindrical to fusiform with obtuse ends, and ranged from 14.2-18.6 µm (16.4 µm)× 3.8-5.4 µm (4.7 µm) (n=100). After germination, conidia formed single, brown, oval or slightly irregular appressoria ranging from 8.0 to 11.8 μm (9.6 µm), and from 4.8 to 6.0 μm (5.4 µm). Sexual stage was absent. These characteristics of conidia and appressoria were matched with C. siamense belonging to the C. gloeosporioides complex (Prihastuti et al. 2009; Yang et al. 2009; Weir et al. 20012; Hu et al. 2015). To accurately identify the species, DNA was extracted from four purified isolates (JG-1, JG-3-1, SWS-1-3, SWS-2-1) （Fu et al. 2019）. The internal transcribed spacer of rDNA region (ITS), glyceraldehydes-3-phosphate dehydrogenase (GAPDH), calmodulin (CAL), actin (ACT) and chitin synthase (CHS) genes were amplified and sequenced. The nucleotide sequences were all deposited in GenBank (ITS: MT229427-MT229430, GAPDH: MT250821-MT250824, CAL: MT258893-MT258896, ACT: MT258897-MT258900 and CHS: MT258901-MT258904). Multi-locus phylogenetic analyses (ITS, GAPDH, CAL, ACT and CHS) (Weir et al. 2012) showed that the four isolates were clustered with C. siamense, which was in accordance with BLAST results. Pathogenicity tests of the four isolates were repeated three times on detached leaves (Ji et al. 2019). The conidial suspension (1×106 conidia/mL) was prepared using the conidia from 10-day-old cultures grown on PDA. Two 20-µL drops of conidial suspension were inoculated on non-wounded young healthy leaves, and each isolate was inoculated on 10 leaves. Two 20-µL drops of sterile water were inoculated on non-wounded young healthy leaves as control. The samples were maintained in containers at a relative humidity of 90± 5 per cent inside and 28℃ with a 12-h photoperiod. Gray, subcircular spots similar to the field disease symptoms were observed on the all inoculated leaves after 7 days, whereas no visible symptoms appeared on the non-inoculated leaves. The pathogen was re-isolated from inoculated leaves thus fulfilling Koch’s postulates. C. gloeosporioides has been previously reported as a pathogen causing leaf spot on Erythrina (E. indica var. picta, E. variegata var. orientalis) in Guam in 1983 and Brazil in 2012. (Russo et al. 1983; Oliveira et al. 2012). To our knowledge, this is the first report of C. siamense causing leaf spot of E. crista-galli in China.

scholarly journals First Report of Colletotrichum acutatum on Strawberry in Northwestern Argentina

Plant Disease ◽  
2000 ◽  
Vol 84 (6) ◽  
pp. 706-706 ◽  
Author(s):  
C. J. Ramallo ◽  
L. D. Ploper ◽  
M. Ontivero ◽  
M. P. Filippone ◽  
A. Castagnaro ◽  
...  
Keyword(s):  
Colletotrichum Acutatum ◽  
Conidial Suspension ◽  
Disease Symptoms ◽  
Northwestern Argentina ◽  
First Report ◽  
Surface Control ◽  
Detached Leaves ◽  
Strawberry Anthracnose ◽  
Pathogenicity Tests ◽  
Necrotic Spots

Isolates were obtained from strawberry tissue with anthracnose symptoms from several locations near Tucumán, Argentina. Isolates were characterized using several criteria. Isolates produced fusiform conidia, tapered to a point at both ends, and averaged 13.5 × 4.9 μm. On potato dextrose agar, colonies produced a white cottony mycelial colony that turned orange in older cultures. Compared with Colletotrichum fragariae, the new isolates produced fewer appressoria. Pathogenicity tests were conducted on detached leaves and plants in the greenhouse and field. Detached immature leaves of cvs. Chandler, Fern, and Sweet Charlie were inoculated with a 20-μl droplet of an aqueous conidial suspension (106 conidia per ml) placed on the adaxial surface. Control leaves were inoculated with sterile distilled water. Leaves were maintained under white light (2,000 lux, 12 h/day) at 26°C, and 100% relative humidity. Necrotic spots were visible 4 days after inoculation. Greenhouse and field plants were spray-inoculated and covered for 48 h. Disease symptoms were mainly observed on petioles and runners 9 days after inoculation. No lesions were observed on control detached leaves or plants. Koch's postulates were confirmed in all cases. Based on morphological and cultural characteristics, isolates were identified as C. acutatum Simmonds (1). This is the first report of C. acutatum causing strawberry anthracnose in northwestern Argentina. Reference: (1) B. Smith and L. L. Black. Plant Dis. 74:69, 1990.

scholarly journals First Report of Gray Leaf Spot on St. Augustinegrass in Italy

Plant Disease ◽  
2003 ◽  
Vol 87 (12) ◽  
pp. 1536-1536 ◽  
Author(s):  
G. Polizzi ◽  
I. Castello ◽  
A. M. Picco ◽  
D. Rodino
Keyword(s):  
Leaf Spot ◽  
Magnaporthe Grisea ◽  
Fungal Spore ◽  
Gray Leaf Spot ◽  
Blast Disease ◽  
Leaf Spot Disease ◽  
High Humidity ◽  
Conidial Suspension ◽  
First Report ◽  
Pathogenicity Tests

St. Augustinegrass (Stenotaphrum secundatum (Walt.) Kuntze) is used for lawns in southern Italy because it is much more resistant to biotic and abiotic adversities than other turfgrass species. Because few seeds are viable, this species is established by vegetative propagation. A new disease was noticed during the spring of 2002 and 2003 on cuttings of St. Augustinegrass growing in three greenhouses in eastern Sicily. The disease affected leaves and culms and caused a progressive drying of the plants. The infection was first seen on leaves as gray, necrotic spots that enlarged in high-humidity conditions to form oval, and later, spindle-shaped lesions. In association with the lesions, it was possible to observe fungal spore development and sunken areas with blue-gray centers and slightly irregular, brown margins with yellow halos. Spots were concentrated without specific arrangement along longitudinal veins and the midrib and at the base, tip, and margins of the leaf blade. Symptoms on the culms consisted of brown-to-black blotches that sometimes extended throughout the internodes. From these infected tissues, 20 explants taken from leaves and culms were cut, washed with sterile water, and placed on 1.5% water agar (WA). Later, conidia and conidiophores were obtained from colonies with a sterile glass needle and placed on 4% WA. From these plates, two monoconidial isolates were obtained and transferred to rice meal medium (1). The colonies were identified as Pyricularia grisea Cooke (Sacc.), anamorphic state of Magnaporthe grisea (Hebert) Yeagashi & Udagawa, the cause of rice blast disease and gray leaf spot disease of turfgrasses. The conidia were pyriform to obclavate, narrowed toward the tip, rounded at the base, 2-septate, 21 to 31 μm × 6 to 10 μm (average 25.7 ×8.2 μm). Pathogenicity tests were performed by inoculating leaves and culms of six St. Augustinegrass plants with a conidial suspension of the fungus (1.5 ×105 conidia per ml). The same number of noninoculated plants was used as controls. All plants were incubated in a moist chamber with high humidity at 25°C. After 6 days, all inoculated plants showed typical symptoms of the disease. Koch's postulates were fulfilled by isolating P. grisea from inoculated plants. Gray leaf spot caused by P. grisea has been a chronic problem on St. Augustinegrass since it was first reported in 1957 (2). To our knowledge, this is the first report of P. grisea on St. Augustinegrass in Italy. While it does not appear to be an important disease in the field at this time in Sicily, it could cause losses in greenhouses where vegetative material is propagated for field planting. A preliminary molecular analysis has shown a clear distinction between the tested strain and other strains isolated from rice seeds and plants in northern Italy. References: (1) E. Roumen et al. Eur. J. Plant Pathol. 103:363, 1997. (2) L. P. Tredway et al. Plant Dis. 87:435, 2003.

scholarly journals First Report of Leaf Spot Caused by Alternaria alternata on Kiwifruit in Italy

Plant Disease ◽  
1999 ◽  
Vol 83 (5) ◽  
pp. 487-487 ◽  
Author(s):  
L. Corazza ◽  
L. Luongo ◽  
M. Parisi
Keyword(s):  
New Zealand ◽  
Alternaria Alternata ◽  
Leaf Spot ◽  
Southern Italy ◽  
Morphological Characteristics ◽  
Potato Dextrose Agar ◽  
First Report ◽  
Leaf Spots ◽  
Detached Leaves ◽  
Pathogenicity Tests

A leaf spot of kiwifruit (Actinidia deliciosa (A. Chev.) C. F. Liang & A. R. Ferg.) leaves was recently observed on plants of the cultivar Hayward in an orchard near Salerno, in southern Italy. The affected plants showed early severe defoliation. The fungus isolated from the infected leaves was identified as Alternaria alternata (Fr.:Fr.) Keissl., based on conidial morphological characteristics. Pathogenicity tests were made by inoculating detached leaves of male pollinator cultivar Tomuri and the female cultivars Hayward and Bruno with a 7-mm disk taken from actively growing cultures of the fungus on potato dextrose agar (PDA). After 14 days, necrotic leaf spots developed and A. alternata was consistently isolated from the inoculated leaves. A. alternata has been observed as a pathogen on leaves and fruits in New Zealand. In the Mediterranean, it has been reported in Israel (2) and in the island of Crete (1). This is the first report of Alternaria leaf spot on kiwifruit in Italy. References: (1) V. A. Bourbos and M. T. Skoudridakis. Petria 7:111, 1997. (2) A. Sive and D. Resnizky. Alon Hanotea 41:409, 1987.

scholarly journals Leaf spot disease of Orychophragmus violaceus caused by Alternaria tenuissima in China

Plant Disease ◽  
2021 ◽  
Author(s):  
Dongli Liu ◽  
Jing Li ◽  
Saisai Zhang ◽  
Xiangjing Wang ◽  
Wensheng Xiang ◽  
...  
Keyword(s):  
Leaf Spot ◽  
Morphological Characteristics ◽  
Leaf Spot Disease ◽  
Its Sequence ◽  
Conidial Suspension ◽  
Orychophragmus Violaceus ◽  
Disease Symptoms ◽  
Alternaria Tenuissima ◽  
Spot Disease ◽  
Pathogenicity Tests

Orychophragmus violaceus (L.) O. E. Schulz, also called February orchid or Chinese violet cress, belongs to the Brassicaceae family and is widely cultivated as a green manure and garden plant in China. During the prolonged rainy period in August 2020, leaf spot disease of O. violaceus was observed in the garden of Northeast Agricultural University, Harbin, Heilongjiang province. One week after the rainy days, the disease became more serious and the disease incidence ultimately reached approximately 80%. The disease symptoms began as small brown spots on the leaves, and gradually expanded to irregular or circular spots. As the disease progressed, spots became withered with grayish-white centers and surrounded by dark brown margins. Later on, the centers collapsed into holes. For severely affected plants, the spots coalesced into large necrotic areas and resulted in premature defoliation. No conidiophores or hyphae were present, and disease symptoms were not observed on other tissues of O. violaceus. To isolate the pathogen, ten leaves with typical symptoms were collected from different individual plants. Small square leaf pieces (5×5 mm) were excised from the junction of diseased and healthy tissues, disinfected in 75% ethanol solution for 1 min, rinsed in sterile distilled water, and then transferred to Petri dishes (9 cm in diameter) containing potato dextrose agar (PDA). After 3 days of incubation at 25 oC in darkness, newly grown-out mycelia were transferred onto fresh PDA and purified by single-spore isolation. Nine fungal isolates (NEAU-1 ~ NEAU-9) showing similar morphological characteristics were obtained and no other fungi were isolated. The isolation frequency from the leaves was almost 90%. On PDA plates, all colonies were grey-white with loose and cottony aerial hyphae, and then turned olive-green and eventually brown with grey-white margins. The fungus formed pale brown conidiophores with sparsely branched chains on potato carrot agar (PCA) plates after incubation at 25 oC in darkness for 7 days. Conidia were ellipsoidal or ovoid, light brown, and ranged from 18.4 to 59.1 × 9.2 to 22.3 µm in size, with zero to two longitudinal septa and one to five transverse septa and with a cylindrical light brown beak (n = 50). Based on the cultural and morphological characteristics, the fungus was tentatively identified as Alternaria tenuissima (Simmons 2007). Genomic DNA was extracted from the mycelia of five selected isolates (NEAU-1 ~ NEAU-5). The internal transcribed spacer region (ITS) was amplified and sequenced using primers ITS1/ITS4 (White et al., 1990). Blast analysis demonstrated that these five isolates had the same ITS sequence, and the ITS sequence of representative strain NEAU-5 (GenBank accession No. MW139354) showed 100% identity with the type strains of Alternaria alternata CBS916.96 and Alternaria tenuissima CBS918.96. Furthermore, the translation elongation factor 1-α gene (TEF), RNA polymerase II second largest subunit (RPB2), and glyceraldehyde 3-phosphate dehydrogenase (GPD) of representative strain NEAU-5 were amplified and sequenced using primers EF1-728F/EF1-986R (Carbone and Kohn 1999), RPB2-5F2/RPB2-5R (Sung et al., 2007), and Gpd1/Gpd2 (Berbee et al., 1999), respectively. The sequences of RPB2, GPD, and TEF of strain NEAU-5 were submitted to GenBank with accession numbers of MW401634, MW165223, and MW165221, respectively. Phylogenetic trees based on ITS, RPB2, GPD, and TEF were constructed with the neighbour-joining and maximum-likelihood algorithms using MEGA software version 7.0. The results demonstrated that strain NEAU-5 formed a robust clade with A. tenuissima CBS918.96 (supported by 99% and 96% bootstrap values) in the neighbour-joining and maximum-likelihood trees. As mentioned above, strain NEAU-5 produced seldomly branched conidial chains on PCA plates. The pattern is consistent with that of A. tenuissima (Kunze) Wiltshire, but distinct from that of A. alternata which could produce abundant secondary ramification (Simmons 2007). Thus, strain NEAU-5 was identified as A. tenuissima based on its morphology and phylogeny. Pathogenicity tests were carried out by inoculating five unwounded leaves with a conidial suspension of strain NEAU-5 (approximately 106 conidia/ml) on five different healthy plants cultivated in garden, and an equal number of leaves on the same plants inoculated with sterilized ddH2O served as negative controls. Inoculated and control leaves were covered with clear plastic bags for 3 days. After 6 days, small brown and irregular or circular spots were observed on all leaves inoculated with conidial suspension, while no such symptoms were observed in the control. The tests were repeated three times. Furthermore, the pathogenicity tests were also performed using 2-month-old potted plants in a growth chamber (28 oC, 90% relative humidity, 12 h/12 h light/dark) with two repetitions. Five healthy plants were inoculated by spraying 20 ml of a conidial suspension of strain NEAU-5 (approximately 106 conidia/ml) onto unwounded leaves. Five other healthy plants were inoculated with sterilized ddH2O as controls. After 7 days, similar symptoms were observed on leaves inoculated with strain NEAU-5, whereas no symptoms were observed in the control. The pathogen was reisolated from the inoculated leaves and identified as A. tenuissima by morphological and molecular methods. In all pathogenicity tests, A. tenuissima could successfully infect unwounded leaves of O. violaceus, indicating a direct interaction between leaves and A. tenuissima. It is known that high humidity and fairly high temperatures can favor the epidemics of Alternaria leaf spot (Yang et al., 2018), and this may explain why severe leaf spot disease of O. violaceus was observed after prolonged rain. Previously, it has been reported that Alternaria brassicicola and Alternaria japonica could cause leaf blight and spot disease on O. violaceus in Hebei and Jiangsu Provinces, China, respectively (Guo et al., 2019; Sein et al., 2020). Although these pathogens could lead to similar disease symptoms on the leaves of O. violaceus, it is easy to distinguish them by the morphological characteristics of conidiophores and ITS gene sequences. To our knowledge, this is the first report of A. tenuissima causing leaf spot disease of O. violaceus in China.

scholarly journals First Report of a New Leaf Spot Caused by Plectosphaerella cucumerina on Field Grown Endive (Cichorium endivia) in Italy

Plant Disease ◽  
2013 ◽  
Vol 97 (6) ◽  
pp. 848-848 ◽  
Author(s):  
A. Garibaldi ◽  
G. Gilardi ◽  
G. Ortu ◽  
M. L. Gullino
Keyword(s):  
Leaf Spot ◽  
Economic Losses ◽  
Leaf Spot Disease ◽  
Fluorescent Light ◽  
Conidial Suspension ◽  
Fresh Market ◽  
First Report ◽  
Cichorium Endivia ◽  
Pathogenicity Tests ◽  
Plectosphaerella Cucumerina

During summer 2012, symptoms of a new leaf spot disease were observed in several commercial fields in Treviglio (Bergamo, northern Italy) on plants of curly (Cichorium endivia var. crispum) and Bavarian (C. endivia var. latifolium) endive (Asteraceae). This crop is widely grown in the region for fresh market. The first symptoms on leaves of affected plants consisted of small (1 mm) black-brown spots of irregular shape, later coalescing into larger spots, up to 10 to 15 mm diameter. Eventually, spots were surrounded by a yellow halo. Particularly, affected tissues rotted quickly under high moisture. Disease severity was greatest at 75 to 90% RH and air temperature between 23 and 30°C, where affected tissues rotted quickly. This disease resulted in severe production losses. On one farm in particular, three different fields totaling 2 ha, 5 to 13% of the plants were affected. Diseased tissue was excised, immersed in a solution containing 1% sodium hypochlorite for 60 s, rinsed in water, then placed on potato dextrose agar (PDA) medium, containing 25 mg/liter of streptomycin sulphate. After 5 days, a fungus developed producing a whitish-orange mycelium when incubated under 12 h/day of fluorescent light at 23°C. The isolates obtained were purified on PDA. On this medium, they produced hyaline elliptical and ovoid conidia, rarely septate, measuring 5.0 to 9.0 × 1.7 to 3.9 (average 6.0 × 2.9) μm. Conidia were born on phialides, single, clavate, and 2.8 × 1.4 μm. Such characteristics are typical of Plectosphaerella sp. (1,2). The internal transcribed spacer (ITS) region of rDNA was amplified using the primers ITS1/ITS4 (3) and sequenced. BLAST analysis of the 530-bp segment obtained from C. endivia var. crispum isolate PLC28 and of the 527-bp from C. endivia var. latifolium isolate PLC 30, respectively, showed 99% similarity with the sequence of Plectosphaerella cucumerina (anamorph Plectosporium tabacinum), GenBank EU5945566. The nucleotide sequences of isolates PLC 28 and PLC 30 have been assigned the GenBank accession numbers KC293994 and KC293993, respectively. To confirm pathogenicity, tests were conducted on 30-day-old C. endivia plants. C. endivia var. crispum cv Myrna and C. endivia var. latifolium cv. Sardana plants, grown in 2-liter pots (1 plant per pot, 10 plants per treatment) were inoculated by spraying a 106 CFU/ml conidial suspension of the two isolates of P. cucumerina, prepared from 10-day-old cultures, grown on PDA. Inoculated plants were maintained in a growth chamber at 25 ± 1°C and 90% RH for 5 days. Non-inoculated plants, only sprayed with water, served as controls. All plants inoculated with the two isolates, showed typical leaf spots 7 days after the artificial inoculation, similar to those observed in the field. Later, spots enlarged and leaves rotted. Non-inoculated plants remained healthy. P. cucumerina was reisolated from inoculated plants. The pathogenicity tests were conducted twice with identical results. This is, to our knowledge, the first report of P. cucumerina on endive n Italy, as well as worldwide. Due to the importance of the crop in Italy, this disease can cause serious economic losses. References: (1) A. Carlucci et al. Persoonia 28:34, 2012. (2) M. E. Palm et al. Mycologia 87:397, 1995. (3) T. J. White et al. PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al., eds. Academic Press, San Diego, 1990.

scholarly journals First Report of Colletotrichum siamense Causing Leaf Spot on Alocasia macrorrhiza in China

Plant Disease ◽  
2021 ◽  
Author(s):  
Rong Huang ◽  
Wenxiu Sun ◽  
Wei Li ◽  
Chunxiang Zhou ◽  
SuiPing Huang ◽  
...  
Keyword(s):  
Phylogenetic Tree ◽  
Leaf Spot ◽  
Morphological Characteristics ◽  
Tween 20 ◽  
Control Group ◽  
Sodium Hypochlorite Solution ◽  
Conidial Suspension ◽  
Disease Symptoms ◽  
First Report ◽  
Wide Range

Alocasia macrorrhiza (L.) Schott, known as Alocasia is found in the Araceae, and is widely planted in southern China for its ornamental and medicinal value. This plant has a wide range of pharmacological effects, and has potential anti-tumor activity (Lei et al. 2013). In July of 2019, leaf spots were observed on A. macrorrhiza in the Xixiangtang Area, Nanning, Guangxi, China. Disease symptoms began with water-soaked yellow-green spots and progressed to form brown, round or oval lesions with yellow halos. Under severe conditions, spots merged into larger irregular lesions. More than 60% of the plants in a 0.5 ha field showed disease symptoms. Symptomatic leaves were collected and cut into small pieces (3×3 mm). Leaf pieces from the margin of the necrotic tissue were surface sterilized in 75% alcohol for 10 s, followed by 2% sodium hypochlorite solution for 2 min, then rinsed three times in sterile distilled water. Tissues were plated on potato dextrose agar (PDA) and incubated at 28°C for 5 days in the dark. Among over 30 isolates, most shared a similar morphology, the isolation rate of these was 86.7% and three of these (GY1-1A, GY1-1B, and GY1-1C) were chosen for single-spore purification and used for fungal morphological characterization and identification. White feathery aerial mycelia with olivaceous gray mycelia below were observed in 7-day cultures. After 14 days, orange conidia were observed. Conidia were hyaline, guttulate, smooth, one-celled, and cylindrical, averaged 13.79 μm × 5.26 μm, 13.89 μm × 5.33 μm and 13.92 μm × 5.42 μm for GY1-1A, GY1-1B and GY1-1C, respectively. Appressoria were mostly irregular in outline, deeply lobed or lightly lobed, gray brown to dark brown, conidial appressoria were 7.93 to 8.74 μm × 5.26 to 5.42 μm, mycelial appressoria were 7.15 to 10.11 μm × 5.60 to 7.44 μm. These morphological characteristics were similar to the C. siamense as previously described (Weir et al. 2012). The partial internal transcribed spacer (ITS) regions, actin (ACT), chitin synthase (CHS-1), glyceraldehydes-3-phosphate dehydrogenase (GAPDH), calmodulin (CAL), β-tubulin (TUB2), and the intergenic region of apn2 and MAT1-2-1 (ApMAT) were amplified from genomic DNA for the three isolates using primers ITS4/ITS1 (White et al. 1990), ACT-512F/ACT-783R, CHS-79F/CHS-354R, GDF1/GDR1, CL1C/CL2C, Bt2a/Bt2b (Weir et al. 2012), and AM-F/AM-R (Silva et al. 2012) and sequenced. All sequences showed over 99% identity with C. siamense and were deposited in GenBank (ITS, MW040179-MW040181; ACT, MW049220-MW049222; CHS-1, MW049229-MW049231; GAPDH, MW049232-MW049234; CAL, MW049226-MW049228; TUB, MW049235-MW049237; ApMAT, MW049223-MW049225). Maximum Likelihood (ML) phylogenetic tree was constructed with MEGA 5 using the concatenation of multiple sequences (ACT, CHS-1, GAPDH, ITS, TUB2, CAL). According to the phylogenetic tree, all three isolates were found with C. siamense with 95% bootstrap support. To confirm pathogenicity, three sets (three plants per set) of healthy leaves were slightly scratched with autoclaved toothpicks at each of eight locations. Each inoculation location was a cross (2 mm length) and inoculation location was at least 3 cm apart. Ten μl of conidial suspension (106 conidia /ml in 0.1% sterile Tween 20) was applied to the inoculation areas. A control group was mock inoculated with 0.1% sterile Tween 20. Plants were covered with plastic bags to maintain a high humidity environment and placed in a 28°C growth chamber with constant light for 7 days. Inoculated leaves showed yellowish brown spots (0.4 × 0.65 cm), but no symptoms were observed in the control group. The fungus was reisolated from inoculated leaves, and these isolates matched the molecular and morphological characteristics of the original isolates confirming Koch’s postulates. Reported hosts of this pathogen include Coffea arabica, Carica papaya, Melilotus indicus and Litchi chinensis (Weir et al. 2012; Qin et al. 2017; Ling et al. 2019) and so on. To our knowledge, this is the first report of C. siamense causing leaf spot on A. macrorrhiza in China. The identification of this pathogen provides a foundation for the management of leaf spot on this medicinal plant.

scholarly journals First Report of Colletotrichum aenigma Causing Apple Glomerella Leaf Spot on the Granny Smith Cultivar in China

Plant Disease ◽  
2021 ◽  
Author(s):  
Zhaohui Zhang ◽  
Mingjie Yan ◽  
Wenwen Li ◽  
Yunzhong Guo ◽  
Xiaofei Liang
Keyword(s):  
Leaf Spot ◽  
Manganese Superoxide Dismutase ◽  
Negative Control ◽  
Post Inoculation ◽  
Pathogenicity Test ◽  
Conidial Suspension ◽  
Species Identity ◽  
First Report ◽  
Leaf Tissues ◽  
Glomerella Leaf Spot

Glomerella leaf spot (GLS) is a devastating fungal disease causing pre-mature defoliation on apple (Malus domestica). It was first reported in 1970s and since then has been reported in North America, South America and Asia. GLS disease is caused by Colletotrichum fungi and the pathogens are genetically diverse, encompassing at least nine species belonging to three species complexes (Velho et al. 2018). In August 2018, disease with sudden leaf necrosis symptom, typical of GLS symptom appearance, occurred in a Granny Smith orchard in Wugong county, China, over 70% tree leaves bared brown and necrotic lesions. Small leaf tissues (3-4 mm2) cut from lesion margins were surface sterilized for 30 s in 3% NaClO and 30 s in 75% ethanol, followed by rinsing three times in sterile water before transferring onto potato dextrose agar (PDA) plates (25 ± 2°C). Seven isolates were obtained, all producing round cottony colonies on PDA, being white to pale on the upper side and dark green on the reverse side. Conidia were single-celled, cylindrical and transparent (17.33 ± 1.29 × 5.11 ± 0.77 μm, n=50). Appressoria were single-celled, thick-walled, dark brown, oval or irregular shaped, sometimes lobed (9.07 ± 0.88 × 6.66 ± 0.33 μm, n=50). The morphological and cultural characteristics of the fungal isolates matched the descriptions of Colletotrichum aenigma (Weir et al. 2012). To confirm the species identity, genomic DNAs were isolated from two representative isolates (QSG1 and QSY1), and the internal transcribed spacer (ITS), actin (ACT), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), beta-tubulin (TUB2), manganese-superoxide dismutase (SOD2), chitin synthase (CHS), and calmodulin (CAL) regions were amplified by PCR using reported primers (Weir et al. 2012). The sequences were deposited in GenBank (Accession Nos. MT872061, MT873580, MT873581, MT888183, MT888185, MT888187 and MT888189 for QSG1, and MT834933, MT835166, MT873579, MT888182, MT888184, MT888186 and MT888188 for QSY1). BLASTn search against GenBank nr database showed that ITS sequences of the two strains showed high nucleotide identity (over 99%) to sequences derived from the Colletotrichum gloeosporioides species complex (CGSC). Further concatenated phylogenetic analysis with reported CGSC strains (Weir et al. 2012) placed QSG1 and QSY1 in the clade of C. aenigma. To fulfill Koch’s postulates, field pathogenicity test was performed. The experiment was performed in an orchard located in Yangling in September 2020, with the daily average temperature ranging between 15 - 20 ℃. Healthy ‘Granny Smith’ leaves were surface sterilized with 70% alcohol and inoculated with conidial suspension (106 conidia/mL) using cotton swabs. For each isolate, 10 leaf inoculations were performed. Inoculation with distilled water served as a negative control. Inoculated leaves were covered with plastic bags to maintain high humidity and the bags were removed at 48 hours post inoculation (hpi). Conidium-inoculated leaves started to exhibit GLS-resembling necrotic lesions from 5 dpi onward. The lesion extent, however, varied among inoculated leaves, ranging from blurry, small-sized lesions to blight of entire leaf. In contrast with conidium inoculations, water-inoculated leaves remained asymptomatic until 14 dpi. Re-isolated fungi from the symptomic leaf tissues were identical to C. aenigma in morphological appearance. Taken together, this is the first report of GLS on ‘Granny Smith’ apple, and the first report of C. aenigma causing apple GLS in China. This information should provide important guideline for developing field control practices of GLS.

scholarly journals First Report of Fusarium proliferatum Causing Rot on Garlic and Onion in Argentina

Plant Disease ◽  
2013 ◽  
Vol 97 (4) ◽  
pp. 556-556 ◽  
Author(s):  
A. E. Salvalaggio ◽  
A. del C. Ridao
Keyword(s):  
Brown Rot ◽  
Fusarium Proliferatum ◽  
Conidial Suspension ◽  
First Report ◽  
Allium Cepa L ◽  
Pathogenicity Tests ◽  
White Mycelium ◽  
Standard Tester ◽  
Gibberella Intermedia ◽  
Made In

In October 2001 and January 2002, in onion fields (Allium cepa L. cv Valencianita) in the Provinces of San Juan (SJ) and Mendoza (MZ), Argentina, plants were observed with chlorosis, dry leaf tips, and bulbs showing discoloration and rot. During the summer of 2002, a tan rot with white mycelium in rot cavities was also observed in stored garlic bulbs (Allium sativum) in MZ. Four monosporic cultures obtained with a micro punch adapted microscope (three from onion CSJ1, CMZ1, CMZ2 and one from garlic AMZ1) were characterized by morphology on PDA and carnation leaf agar (2). The isolates were deposited in the fungal collection of the Plant Mycosis Laboratory of the Integrated Unit Balcarce. The isolates produced abundant aerial white mycelium and a violet to vinaceous pigmentation. Club-shaped microconidia were abundant, in chains on both mono- and polyphialides. Slender, thin-walled and relatively straight macroconidia were produced only under black light and were mostly 3-septate. Chlamydospores were absent. The isolates were identified as Fusarium proliferatum. Crosses to confirm mating populations and to identify mating types were made in triplicate on carrot agar (3) with standard tester strains D-04853 (MATD-2) and D-04854 (MATD-1) as female parents and the field isolates as male parents. Crosses were examined weekly and were scored positive only if perithecia were seen oozing a cirrhus of ascospores. The identities of these isolates were confirmed as showing positive crosses with standard tester strains of Gibberella intermedia. Pathogenicity tests were conducted with healthy 45-day-old onion seedlings (cv. Valcatorce INTA). The roots of the onion seedlings were soaked in a conidial suspension (5 × 106 conidia/ml) of each isolate (CSJ1, CMZ1, CMZ2) for 2 h; the control was soaked in sterile water (SW). Seedlings were transplanted to pots in a sterile mixture of soil and sand (v/v). Five plants were used for each of 3 replications. The plants were placed in a greenhouse and irrigated with SW. After 3 weeks, symptoms were evaluated. All inoculated plants exhibited symptoms similar to those observed in the bulbs from which the pathogen was isolated and a brown rot appeared on the basal plate of the onion, later becoming dark brown. In garlic, the inoculation consisted of a wound 4.5 mm deep and 2 mm wide in superficially sterilized garlic cloves (cv. Nieve INTA). Inside the cavity, a drop (50 μl) was placed from a suspension of 5 × 106 conidia/ml (AMZ1), then covered with a drop of paraffin. Controls used SW. The garlic cloves were incubated in hermetically sealed trays at 22 ± 3°C in darkness for 3 weeks (1). Garlic showed tan rot and white mycelium in the wound. F. proliferatum was reisolated from inoculated onion seedlings and garlic cloves. The controls did not exhibit symptoms nor were any fungi recovered when tissue was excised from the inoculation points and plated on agar. F. proliferatum was previously reported in Argentina on asparagus (4) with symptoms similar to those of onion and garlic. To our knowledge, this is the first report of F. proliferatum attacking onion and garlic in Argentina. This pathogen has the potential risk of mycotoxin accumulation in contaminated bulbs. References: (1) F. M. Dugan et al. J. Phytopathol. 155:437, 2007. (2) W. Gerlach and H. Nirenberg. The genus Fusarium – A Pictorial Atlas. Mitt. Biol. Bundesanst. Land. Forstwirsch. Berl.-Dahlem, 1982. (3) C. J. R. Klittich and J. F. Leslie. Genetics 118:417, 1988. (4) G. Lori et al. Plant Dis. 82:1405, 1998.

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.

scholarly journals First Report of Alternaria Leaf Blight on Bupleurum chinense Caused by Alternaria alternata in China

Plant Disease ◽  
2010 ◽  
Vol 94 (7) ◽  
pp. 918-918
Author(s):  
Z. Zhang ◽  
J. H. Wei ◽  
C. M. Yang ◽  
H. Q. Chen ◽  
C. Sui ◽  
...  
Keyword(s):  
Disease Incidence ◽  
Conidial Suspension ◽  
First Report ◽  
High Soil Moisture ◽  
Leaf Spots ◽  
Black Spots ◽  
Initial Symptoms ◽  
Leaf Tissues ◽  
Pathogenicity Tests ◽  
Symptomatic Leaf

Bupleurum chinense DC. (family Umbelliferae) is an important medicinal herb in traditional Chinese medicine and is cultivated as an economically important plant in China (2). From 2006 to 2009, severe foliar disease was observed on B. chinense in Haidian, Changping, and Shunyi districts, Beijing, China. Approximately 75 to 85% of fields were affected with disease incidence ranging from 65 to 90%. Distribution of the disease in affected B. chinense fields was generally associated with high soil moisture, often corresponding to poor drainage. Initial symptoms first appeared on older leaves as irregularly shaped, minute, dark brown-to-black spots, with yellow borders on the edge of the affected leaflet blade. As the disease progressed, the lesions expanded, causing the leaflets to turn brown, shrivel, and die. Isolations performed on potato dextrose agar (PDA) initially resulted in white colonies. After 7 days of incubation at 25°C, the colonies turned gray or brown. Conidia varied in size from 10 × 6 to 40 × 12 μm, appeared brown to dark brown or olive-brown, were short beaked and borne in long chains, oval and bean-shaped with one to six transverse septa and zero to three longitudinal septa. Sequences of the rDNA from the internal transcribed spacer regions 1 and 2 and the 5.8S gene were amplified using primers ITS1 and ITS4, were obtained from three isolates, and comparisons with GenBank showed 100% similarity with A. alternata (Genbank Accession No. AB470912.1). For pathogenicity tests, three isolates were grown on PDA for 14 days. Inoculations were performed on detached, surface-sterilized, and healthy B. chinense leaflets following the method of Belisario (1). A 5-μl drop of conidial suspension containing 1 × 105 CFU/ml was placed on each leaflet and 12 leaves per isolate were used. Leaves were incubated in a growth chamber (80 to 90% relative humidity; 50 to 60 klx/m2 light intensity with a 12-h photoperiod). After 5 days, leaf spots similar to the original symptoms developed on all inoculated leaves and A. alternata was consistently reisolated from symptomatic leaf tissues on PDA. Control leaflets inoculated with sterile water remained asymptomatic. The experiment was performed three times. To our knowledge, this is the first report of A. alternata on B. chinense from China. References: (1) A. Belisario et al. Plant Dis. 83:696, 1999. (2) C. Sui et al. Plant Dis. 93:844, 2009.

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