Occurrence of Leaf Spot Caused by Alternaria alternata on Eggplant (Solanum melongena) in Pakistan

Eggplant (Solanum melongena L.) is a popular vegetable that is grown in both tropical and subtropical regions all year long. The crop is cultivated on small family farms and is a good source of income for resource-limited farmers in Pakistan. In early May 2019, leaf spots on eggplant (cv. Bemisaal) were observed in an experimental field (31°26'14.0"N 73°04'23.4"E) at the University of Agriculture, Faisalabad, Pakistan. Early symptoms were small, circular, brown, necrotic spots uniformly distributed on leaves. The spots gradually enlarged and coalesced into large, nearly circular or irregularly shaped spots that could be up to 3 cm in length. The center of the spots was light tan, surrounded by a dark brown ring, a chlorotic halo, and tended to split in the later developmental stages. Disease incidence was approximately 35% in the infected field. The causal agent of this disease was isolated consistently by plating surface sterilized (1% NaOCl) sections of symptomatic leaf tissue onto potato dextrose agar (PDA). After 6 days incubation at 25°C with a 12-h photoperiod, fungal colonies had round margins and the cottony mycelia were dark olivaceous with a mean diameter of 7.5 cm. For conidial production, the fungus was grown on potato carrot agar (PCA) and V8 agar media under a 16-h/8-h light/ dark photoperiod at 25°C. Conidiophores were septate, light to olive golden brown with a conidial scar, from which conidia were produced. Conidia were borne singly or in short chains and were obpyriform to obclavate, measured 29 ± 4.8 × 13.25 ± 2.78 μm (n=30) with zero to three longitudinal and two to six transversal septa. The morphological characters matched those of Alternaria alternata (Fr.) Keisel (Simmons et al. 2007). DNA was extracted using the DNAzol reagent (Thermo Fisher Scientific MA, USA). For molecular identification, internal transcribed spacer (ITS) region between ITS1 and ITS2, actin gene (β-Actin), translation elongation factor (TEF-1α) gene, and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) gene of two representative isolates (JLUAF1 and JLUAF2) were amplified with primers ITS1/ITS4 (White et al. 1990), β-Actin 512 F/783 R, EF1-728F/-986R (Carbone et al. 1999), and gpd1/gpd2 (Berbee et al. 1999), respectively. The sequences were deposited in GenBank (accession nos. MT228734.1 and MT228735.1 for ITS; MT260151.1 and MT260152.1 for β-Actin, MT260163.1 and MT260164.1, for TEF-1a, and MT260157.1 and MT260158.1 for GAPDH). BLASTn analysis of these sequences showed 100% identity with the sequences of A. alternata for ITS rDNA, β-Actin, TEF-1α, and GAPDH, respectively. Based on the morphological characters and DNA sequences, the leaf spot isolates of eggplant were identified as A. alternata. To confirm the pathogenicity on eggplant, six-week old healthy potted eggplants of cv. Bemisaal were sprayed at the true leaf stage with conidial suspensions of A. alternata (106 conidia/ml; obtained from 1-week-old cultures) amended with 0.1% (vol/vol) of Tween 20 until runoff (1.5 to 2 ml per plant) using an atomizer in the greenhouse. Three plants were inoculated with each of the two isolates (JLUAF1 and JLUAF2), whereas three control plants were sprayed with sterile distilled water amended with 0.1% Tween 20. The plants were incubated at 25 ± 2°C in a greenhouse, and the experiment was conducted twice. After 10 days of inoculation, each isolate induced leaf spots which were similar to typical spots observed in the field, whereas the control plants remained symptomless. The fungus was re-isolated from symptomatic tissues. Re-isolated fungal cultures were morphologically and molecularly identical to A. alternata, thus fulfilling Koch’s postulates. Previously, A. alternata has been reported to cause leaf spots on eggplant in India (Raina et al. 2018). To our knowledge, this is the first report of A. alternata causing leaf spot on eggplant in Pakistan. The disease could represent a threat for eggplant crops due to its increasing cultivation. It is important to develop disease management strategies for Alternaria alternata causing leaf spot of Eggplant in Pakistan.

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First report of Alternaria alternata causing Alternaria leaf spot of Fig in Pakistan

Plant Disease ◽

10.1094/pdis-05-21-0963-pdn ◽

2021 ◽

Author(s):

Hafiz Arslan Anwaar ◽

Rashida Atiq ◽

Sobia Chohan ◽

Amjad Saeed ◽

Muqaddas Tanveer Cheema ◽

...

Keyword(s):

Alternaria Alternata ◽

Leaf Spot ◽

Its Rdna ◽

Tween 20 ◽

Distilled Water ◽

Conidial Suspension ◽

Fungal Isolation ◽

First Report ◽

Leaf Spots ◽

Fruit Disease

Fig (Ficus carica) is a species of flowering plants within the mulberry family. During June 2020, leaf spots were observed on several fig plants (31°26'15.0"N 73°04'25.6"E) at the University of Agriculture, Faisalabad, Pakistan. Early symptoms were small, oval to circular, light brown, sunken spots that were uniformly distributed on the leaves. Spots gradually enlarged and coalesced into circular to irregular dark brown to black spots that could be up to 3cm diam. with no or small sized fruit. Disease incidence was approximately 25%. To identify the causal agent of the disease, 15 symptomatic leaves were collected. Small pieces from all diseased samples were removed from the margin between healthy and diseased tissues were surface disinfested in 70% ethanol for 2 min, rinsed three times with sterile distilled water, plated on Potato dextrose agar and incubated at 25 ± 2°C with a 12-h photoperiod. Fungal isolation on PDA medium frequency was 95% from diseases leaves. Morphological observations were made on 7- day- old single-spore cultures. The colonies initially appeared light grayish which turned sooty black in color. All fungal isolates were characterized by small, short-beaked, multicellular conidia. The conidia were ellipsoidal or ovoid and measured 9 to 25 μm × 5 to 10 μm (n = 40) with longitudinal and transverse septa. The morphological characters matched those of Alternaria alternata (Simmons et al. 2007). Genomic DNA of a representative isolate (FG01-FG03) was extracted using DNAzol reagent (Thermo Fisher Scientific MA, USA) and PCR amplification of the internal transcribed spacer (ITS) rDNA region, was performed with primers ITS1/ITS4 (White et al. 1990), partial RNA polymerase II largest subunit (RPB2) with RPB2-5F/RPB2-7cR (Liu et al. 1999) and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) gene regions was performed with gpd1/gpd2 (Berbee et al. 1999). The obtained sequences were deposited in GenBank with accession numbers MW692903.1 to MW692905.1 for ITS-rDNA gene, MZ066731.1 to MZ066733.1 for RPB2 and MZ066728.1 to MZ066730.1 for GAPDH. BLASTn analysis showed 100% identity with the submitted sequences of A. alternata for ITS rDNA, RPB2, and GAPDH. To confirm pathogenicity, 2-month-old 15 healthy potted F. carica plants were sprayed at true leaf stage with conidial suspension by using an atomizer in a greenhouse. Each representative A. alternata isolate (FG01-FG03) was inoculated on every three plants with conidial suspensions (106 conidia/ml; obtained from 1-week-old cultures) amended with 0.1% (vol/vol) of Tween 20 until runoff (1.5 to 2 ml per plant) whereas, three control plants were sprayed with sterile distilled water amended with 0.1% Tween 20. All plants were incubated at 25 ± 2°C in a greenhouse, and the experiment was conducted twice. After 10 days of inoculation, each isolate induced leaf spots similar to typical spots observed in the field, whereas the control plants remained symptomless. The fungus was re-isolated from symptomatic tissues and reisolation frequency was 100%. Re-isolated fungal cultures were again morphologically and molecularly identical to A. alternata, thus fulfilling Koch’s postulates. Previously, A. alternata has been reported cause fruit disease of fig in Pakistan and California, USA (Alam et al. 2021; Latinović et al. 2014). To our knowledge, this is the first report of A. alternata causing leaf spot on common fig in Pakistan. In Pakistan, fig is widely grown for drying, and this disease may represent a threat to fig cultivation.

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First Report of Botrytis cinerea Causing Leaf Spot on Strawberry in Florida

Plant Disease ◽

10.1094/pdis-05-21-1082-pdn ◽

2021 ◽

Author(s):

Marcus Vinicius Marin ◽

Natalia A. Peres

Keyword(s):

Botrytis Cinerea ◽

Leaf Spot ◽

Fungicide Resistance ◽

Disease Incidence ◽

Deionized Water ◽

Fruit Rot ◽

Tween 20 ◽

Isolation Medium ◽

First Report ◽

Leaf Spots

During the 2020-2021 Florida strawberry season (October to April), strawberry (Fragaria × ananassa) plants showing leaf spots were observed on samples submitted to the Diagnostic Clinic at the University of Florida’s Gulf Coast Research and Education Center. Disease incidence was up to 5% and observed on four different farms in Plant City, FL on cultivars SensationTM Florida127 and Florida Brilliance. All the samples were submitted early in the season (November) and shared the same nursery source in California. Symptoms consisted of circular or irregular lesions with purple or brown halos, eventually developing leaf blight with sporulation at the center on advanced lesions. Diseased tissues (0.5 mm2) were surface disinfested with 10% bleach solution for 90 s, rinsed twice in sterile deionized water, and plated on general isolation medium (Amiri et al. 2018). Plates were incubated at 25°C and a 12-h photoperiod. A fungus producing white mycelia with sparse sporulation of Botrytis-like spores was consistently isolated. Isolates were single-spored and grown on HA medium to induce sporulation (Leroch et al. 2013). Three isolates (20-291, 20-293, and 20-295) were selected for identification and pathogenicity assays. Resulting cultures on HA had profuse sporulation resembling gray mold. Conidia (n=50) were round to ellipsoid ranging from 9 to 14.6 μm long (Avg=10.8, SD=1.3) and 6.3 to 9.5 μm wide (Avg=7.7, Sd=0.7). No sclerotia formation was observed on GI and HA medium. Based on morphology, the pathogen was tentatively identified as Botrytis cinerea (Hong et al. 2001; Jarvis 1977). DNA was extracted from the same three isolates using the FastDNA kit (MP Biomedicals, Solon, OH), and the heat shock protein (HSP60), RNA polymerase II-binding (RPB2), and glyceraldehyde 3-phosphate dehydrogenase (G3PDH) genes were amplified (Staats et al. 2004). Sequences were deposited in GenBank (accession nos. MZ288746 - MZ288754). BLASTn searches revealed that isolates were 100% identical to B. cinerea reported causing leaf spot on strawberry in California; accession numbers MK919494 (HSP60, 996/996 bp), MK919495 (RPB2, 1131/1131 bp), and MK919496 (G3PDH, 877/877 bp). To test for pathogenicity, four one-month-old plants of 'Florida Brilliance' were used per isolate and control treatment. Spores were harvested from two-week-old cultures grown on HA medium, and the suspension adjusted to 106 spores/mL in a solution of 0.1% of Tween 20. Plants were spray inoculated until run-off and kept inside clear plastic boxes for 48 h. Control plants were sprayed with sterile deionized water. Afterward, plants were kept in a misting table in the greenhouse with a water regime of 3 s every 10 min during the day. Disease incidence was evaluated weekly, and the experiment repeated once. Two weeks after inoculation, leaf spots were observed in all inoculated plants, while controls remained healthy. Fungi morphologically identical to the original isolates were re-isolated from the diseased tissues. To our knowledge, this is the first report of B. cinerea causing leaf spot on strawberry in Florida. This disease was recently reported in California (Mansouripour and Holmes 2020), which is where the transplants originated from. Considering the disease was observed early in the Florida season, it is likely that it was introduced with transplants from the nursery. This pathogen is also the causal agent of Botrytis fruit rot, which is considered a major disease of strawberry, and a previous study has shown that populations resistant to multiple fungicides are introduced with transplants (Mertely et al. 2018, Oliveira et al. 2018). While Botrytis leaf spot is currently considered rare and of minor significance (Mansouripour and Holmes 2020), it could contribute to the spread of fungicide resistance to from nursery to strawberry fruit production fields. Efforts should be implemented to monitor its occurrence and spread considering the high variability and fungicide resistance profile of this pathogen.

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First Report of Leaf Spot Caused by Alternaria alternata on Switchgrass in Tennessee

Plant Disease ◽

10.1094/pdis-09-11-0785 ◽

2012 ◽

Vol 96 (5) ◽

pp. 763-763 ◽

Cited By ~ 2

Author(s):

A. L. Vu ◽

M. M. Dee ◽

T. Russell ◽

J. Zale ◽

K. D. Gwinn ◽

...

Keyword(s):

Alternaria Alternata ◽

Leaf Spot ◽

Panicum Virgatum ◽

Leaf Tissue ◽

Its Region ◽

Sporulation Medium ◽

Sterile Water ◽

One Pot ◽

First Report ◽

Leaf Spots

Field-grown seedlings of ‘Alamo’ switchgrass (Panicum virgatum L.) from Vonore, TN exhibited light brown-to-dark brown leaf spots and general chlorosis in June 2009. Symptomatic leaf tissue was surface sterilized (95% ethanol for 1 min, 20% commercial bleach for 3 min, and 95% ethanol for 1 min), air dried on sterile filter paper, and plated on 2% water agar amended with 10 mg/liter rifampicin (Sigma-Aldrich, St. Louis, MO) and 5 μl/liter miticide (2.4 EC Danitol, Valent Chemical, Walnut Creek, CA). Plates were incubated at 26°C for 4 days in darkness. An asexual, dematiaceous mitosporic fungus was isolated and transferred to potato dextrose agar. Cultures were transferred to Alternaria sporulation medium (3) to induce conidial production. Club-shaped conidia were produced in chains with branching of chains present. Conidia were 27 to 50 × 10 to 15 μm, with an average of 42.5 × 12.5 μm. Morphological features and growth on dichloran rose bengal yeast extract sucrose agar were consistent with characteristics described previously for Alternaria alternata (1). Pathogenicity studies were conducted with 5-week-old ‘Alamo’ switchgrass plants grown from surface-sterilized seed. Nine pots with approximately 20 plants each were prepared. Plants were wounded by trimming the tops. Eight replicate pots were sprayed with a conidial spore suspension of 5.0 × 106 spores/ml sterile water and subjected to high humidity by enclosure in a plastic bag for 7 days. One pot was sprayed with sterile water and subjected to the same conditions to serve as a control. Plants were maintained in a growth chamber at 25/20°C with a 12-h photoperiod. Foliar leaf spot symptoms appeared 5 to 10 days postinoculation for all replicate pots inoculated with A. alternata. Symptoms of A. alternata infection were not observed on the control. Lesions were excised, surface sterilized, plated on water agar, and identified in the same manner as previously described. The internal transcribed spacer (ITS) region of ribosomal DNA and the mitochondrial small sub-unit region (SSU) from the original isolate and the reisolate recovered from the pathogenicity assay were amplified with PCR, with primer pairs ITS4 and ITS5 and NMS1 and NMS2, respectively. Resultant DNA fragments were sequenced and submitted to GenBank (Accession Nos. HQ130485.1 and HQ130486.1). A BLAST search (BLASTn, NCBI) was run against GenBank isolates. The ITS region sequences were 537 bp and matched 100% max identity with eight A. alternata isolates, including GenBank Accession No. AB470838. The SSU sequences were 551 bp and matched 100% max identity with seven A. alternata isolates, including GenBank Accession No. AF229648. A. alternata has been reported from switchgrass in Iowa and Oklahoma (2); however, this is the first report of A. alternata causing leaf spot on switchgrass in Tennessee. Switchgrass is being studied in several countries as a potentially important biofuel source, but understanding of the scope of its key diseases is limited. References: (1) B. Andersen et al. Mycol. Res. 105:291, 2001. (2) D. F. Farr and A. Y. Rossman. Fungal Databases. Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ , September 22, 2011. (3) E. A. Shahin and J. F. Shepard. Phytopathology 69:618, 1979.

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First Report of Alternaria Leaf Spot of Banana Caused by Alternaria alternata in the United States

Plant Disease ◽

10.1094/pdis-01-13-0007-pdn ◽

2013 ◽

Vol 97 (8) ◽

pp. 1116-1116 ◽

Cited By ~ 3

Author(s):

V. Parkunan ◽

S. Li ◽

E. G. Fonsah ◽

P. Ji

Keyword(s):

United States ◽

Alternaria Alternata ◽

Leaf Spot ◽

Morphological Characteristics ◽

The United States ◽

Its Sequencing ◽

Single Spore ◽

First Report ◽

Alternaria Leaf Spot ◽

Leaf Spots

Research efforts were initiated in 2003 to identify and introduce banana (Musa spp.) cultivars suitable for production in Georgia (1). Selected cultivars have been evaluated since 2009 in Tifton Banana Garden, Tifton, GA, comprising of cold hardy, short cycle, and ornamental types. In spring and summer of 2012, 7 out of 13 cultivars (African Red, Blue Torres Island, Cacambou, Chinese Cavendish, Novaria, Raja Puri, and Veinte Cohol) showed tiny, oval (0.5 to 1.0 mm long and 0.3 to 0.9 mm wide), light to dark brown spots on the adaxial surface of the leaves. Spots were more concentrated along the midrib than the rest of the leaf and occurred on all except the newly emerged leaves. Leaf spots did not expand much in size, but the numbers approximately doubled during the season. Disease incidences on the seven cultivars ranged from 10 to 63% (10% on Blue Torres Island and 63% on Novaria), with an average of 35% when a total of 52 plants were evaluated. Six cultivars including Belle, Ice Cream, Dwarf Namwah, Kandarian, Praying Hands, and Saba did not show any spots. Tissue from infected leaves of the seven cultivars were surface sterilized with 0.5% NaOCl, plated onto potato dextrose agar (PDA) media and incubated at 25°C in the dark for 5 days. The plates were then incubated at room temperature (23 ± 2°C) under a 12-hour photoperiod for 3 days. Grayish black colonies developed from all the samples, which were further identified as Alternaria spp. based on the dark, brown, obclavate to obpyriform catenulate conidia with longitudinal and transverse septa tapering to a prominent beak attached in chains on a simple and short conidiophore (2). Conidia were 23 to 73 μm long and 15 to 35 μm wide, with a beak length of 5 to 10 μm, and had 3 to 6 transverse and 0 to 5 longitudinal septa. Single spore cultures of four isolates from four different cultivars were obtained and genomic DNA was extracted and the internal transcribed spacer (ITS1-5.8S-ITS2) regions of rDNA (562 bp) were amplified and sequenced with primers ITS1 and ITS4. MegaBLAST analysis of the four sequences showed that they were 100% identical to two Alternaria alternata isolates (GQ916545 and GQ169766). ITS sequence of a representative isolate VCT1FT1 from cv. Veinte Cohol was submitted to GenBank (JX985742). Pathogenicity assay was conducted using 1-month-old banana plants (cv. Veinte Cohol) grown in pots under greenhouse conditions (25 to 27°C). Three plants were spray inoculated with the isolate VCT1FT1 (100 ml suspension per plant containing 105 spores per ml) and incubated under 100% humidity for 2 days and then kept in the greenhouse. Three plants sprayed with water were used as a control. Leaf spots identical to those observed in the field were developed in a week on the inoculated plants but not on the non-inoculated control. The fungus was reisolated from the inoculated plants and the identity was confirmed by morphological characteristics and ITS sequencing. To our knowledge, this is the first report of Alternaria leaf spot caused by A. alternata on banana in the United States. Occurrence of the disease on some banana cultivars in Georgia provides useful information to potential producers, and the cultivars that were observed to be resistant to the disease may be more suitable for production. References: (1) E. G. Fonsah et al. J. Food Distrib. Res. 37:2, 2006. (2) E. G. Simmons. Alternaria: An identification manual. CBS Fungal Biodiversity Center, Utrecht, Netherlands, 2007.

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First Report of a Leaf Spot Disease of Bells-of-Ireland (Moluccella laevis) Caused by Cercospora apii in California

Plant Disease ◽

10.1094/pdis.2003.87.2.203a ◽

2003 ◽

Vol 87 (2) ◽

pp. 203-203

Author(s):

S. T. Koike ◽

S. A. Tjosvold ◽

J. Z. Groenewald ◽

P. W. Crous

Keyword(s):

Leaf Spot ◽

Sequence Data ◽

Disease Incidence ◽

Leaf Spot Disease ◽

Conidial Suspension ◽

Internal Transcribed Spacer Region ◽

First Report ◽

Spot Disease ◽

Leaf Spots ◽

Initial Symptoms

Bells-of-Ireland (Moluccella laevis) (Lamiaceae) is an annual plant that is field planted in coastal California (Santa Cruz County) for commercial cutflower production. In 2001, a new leaf spot disease was found in these commercially grown cutflowers. The disease was most serious in the winter-grown crops in 2001 and 2002, with a few plantings having as much as 100% disease incidence. All other plantings that were surveyed during this time had at least 50% disease. Initial symptoms consisted of gray-green leaf spots. Spots were generally oval in shape, often delimited by the major leaf veins, and later turned tan. Lesions were apparent on both adaxial and abaxial sides of the leaves. A cercosporoid fungus having fasciculate conidiophores, which formed primarily on the abaxial leaf surface, was consistently associated with the spots. Based on morphology and its host, this fungus was initially considered to be Cercospora molucellae Bremer & Petr., which was previously reported on leaves of M. laevis in Turkey (1). However, sequence data obtained from the internal transcribed spacer region (ITS1, ITS2) and the 5.8S gene (STE-U 5110, 5111; GenBank Accession Nos. AY156918 and AY156919) indicated there were no base pair differences between the bells-of-Ireland isolates from California, our own reference isolates of C. apii, as well as GenBank sequences deposited as C. apii. Based on these data, the fungus was subsequently identified as C. apii sensu lato. Pathogenicity was confirmed by spraying a conidial suspension (1.0 × 105 conidia/ml) on leaves of potted bells-of-Ireland plants, incubating the plants in a dew chamber for 24 h, and maintaining them in a greenhouse (23 to 25°C). After 2 weeks, all inoculated plants developed leaf spots that were identical to those observed in the field. C. apii was again associated with all leaf spots. Control plants, which were treated with water, did not develop any symptoms. The test was repeated and the results were similar. To our knowledge this is the first report of C. apii as a pathogen of bells-of-Ireland in California. Reference: (1) C. Chupp. A Monograph of the Fungus Genus Cercospora. Cornell University Press, Ithaca, New York, 1954.

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First Report of Alternaria Leaf Spot of Almond Caused by Species in the Alternaria alternata Complex in California

Plant Disease ◽

10.1094/pdis.2001.85.5.558b ◽

2001 ◽

Vol 85 (5) ◽

pp. 558-558 ◽

Cited By ~ 6

Author(s):

B. L. Teviotdale ◽

M. Viveros ◽

B. Pryor ◽

J. E. Adaskaveg

Keyword(s):

Alternaria Alternata ◽

Leaf Spot ◽

Disease Incidence ◽

Prunus Dulcis ◽

Leaf Spot Disease ◽

Yield Losses ◽

Mature Leaves ◽

Branching Chains ◽

Paper Towels ◽

Industry Conference

A new leaf spot disease of almond (Prunus dulcis [Mill.] D. Webb) was observed in California in the late 1980s and was first associated with severe defoliation in the mid-1990s (1). Orchards in areas with frequent summer dews, high humidity, and little air movement sustained severe defoliation, resulting in yield losses often exceeding 50%. Symptoms occur only on leaf blades in late spring and summer. Lesions develop as small, circular, tan spots 1 to 3 mm in diameter that may enlarge to 5 to 20 mm in size. Semicircular lesions frequently develop along the leaf margins and tips. The centers of mature lesions become black with fungal sporulation. The fungi isolated from the margins of sporulating and non-sporulating lesions were identified as three species in the Alternaria alternata complex: A. alternata, A. arborescens, and A. tenuissima (2,3). Cultures grown in the dark on potato dextrose (PDA) or potato-carrot agar are grayish white to olivacious green in the former two species and dark gray and wooly in the latter species. On 5% PDA, cultures of all three species produced catenulate dictyospores that were granular to punctate (-verrucose), pale yellowish to brown or black, and had visible apical and basal pores. Conidial morphology depended on chain position; apical conidia ranged from ovoid to ellipsoid, whereas basal conidia were elliptical to obclavate. Average conidial dimensions of A. alternata and A. arborescens ranged from 20 to 28 × 8 to 10 μm. Conidia of A. alternata were produced in acropetal succession in branching chains on single, short suberect conidiophores. A. arborescens produced conidia similarly but mostly in dichotomously branching chains on short to long conidiophores. Average conidial dimensions of A. tenuissima ranged from 20 to 34 × 8 to 12 μm and they were produced in simple chains with one or two branches forming occasionally. In preliminary studies, the optimum temperature for mycelial growth on PDA for all three species ranged from 24 to 28°C. Fifty mature leaves on each of four 7- or 8-year-old almond cv. Butte trees were inoculated at 2- to 3-week intervals from mid-spring through summer in 1999 and 2000. Leaves were sprayed with aqueous suspensions containing 105 conidia per milliliter for one isolate each of A. alternata and A. arborescens and two isolates of A. tenuissima or with sterile distilled water. The shoots were covered for 72 h with plastic-lined brown paper bags containing wet paper towels. Leaves were examined for infection after 7 and 14 days. All isolates were pathogenic and produced non-sporulating lesions similar to those observed in natural infections. No symptoms were observed on noninoculated control plants. Disease incidence was low (<15%) until late June 1999 and July 2000. Inoculations in summer produced increasingly more infections, reaching incidences of 40 to 52% in September 1999 and 18 to 80% in August 2000. References: (1) J. E. Adaskaveg. 1994. Pages 5–7 in Proceedings of the 22nd Annual Almond Industry Conference. 1994. (2) J. Rotem. 1994. The genus Alternaria. Biology, Epidemiology, and Pathogenicity. APS Press, St. Paul, MN. (3) E. G. Simmons. Mycotaxon 70:325–369, 1999.

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Screening of French Bean (Phaseolus vulgaris L.) Genotypes against Alternaria Leaf Spot Caused by (Alternaria alternata) under Dryland Conditions of Kashmir

International Journal of Plant & Soil Science ◽

10.9734/ijpss/2021/v33i2330715 ◽

2021 ◽

pp. 25-30

Author(s):

Sabiya Bashir ◽

Mohammad Najeeb Mughal ◽

Zahida Rashid ◽

Shabeena Majid ◽

Sabeena Naseer ◽

...

Keyword(s):

Alternaria Alternata ◽

Leaf Spot ◽

Disease Incidence ◽

French Bean ◽

Phaseolus Vulgaris L ◽

Dryland Agriculture ◽

Disease Reaction ◽

The Mean ◽

Selection For ◽

Resistant Genotypes

Sixty-three genotypes of french bean was screened against leaf spot (Alternaria alternata) in sick plots at Research Farm of Dryland Agriculture Research Srinagar, Rangreth during Kharif 2018 and 2019. The highest mean disease incidence ranged from 0.00 to 85.00 per cent with the mean disease intensity ranged from 0.00 to 53.26 per cent .One genotype namely ‘Local Pulwama’ was highly susceptible in their disease reaction. Among the screened germplasm, ‘Highly Resistant’ genotypes was SKU-R-601, SKUA-R-105, SKU-R-927, DARS-25, DARS-66, DARS-R-615, while as ‘Susceptible’ genotypes was DARS-8, DARS-12, DARS-11, SKUAST-R-155, SKU-R-928, DARS-7, DARS-R-4, Bhaderwah (L), Local Kupwara black and Raj Jawala. Local Pulwama was found to be a highly susceptible (HS) genotype. Twenty nine genotypes namely., DARS-16, DARS-9, DARS-54, DARS-39, VL-125, DARS-63, ENTO-504, SKUAST-204,SKU-R-925, DARS-60, DARS-109, DARS-43, DARS-44, SKU-R-23, DARS-4, DARS-74, SKU-R-105, DARS-40, DARS-23, DARS-18, SKU-R-71, WB-341, SKU-R-605, Uri local, Shopian (L), SKU-R-23, DARS-71, SSGB-729, DARS-R-19 showed resistant reaction to disease. The selection for resistance was based on the reaction of varieties on leaves.

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LEAF SPOT OF BANANAS CAUSED BY MYCOSPHAERELLA MUSICOLA: ASSOCIATED ASCOMYCETOUS FUNGI

Canadian Journal of Botany ◽

10.1139/b63-128 ◽

1963 ◽

Vol 41 (10) ◽

pp. 1481-1485 ◽

Cited By ~ 5

Author(s):

R. H. Stover

Keyword(s):

Leaf Spot ◽

Leaf Tissue ◽

Leaf Spots ◽

Mycosphaerella Musicola ◽

Banana Leaf

In addition to perithecia, spermagonia, and sporodochia of Mycosphaerella nmsicola Leach (Cercospora musac Zimm.), perithecia of M. minima Stahel, Leptosphaeria sp., Micronectridla sp. and Didymella sp. are present in banana leaf spots in Honduras. All of these fungi discharge ascospores from both surfaces of wet leaf spots. Discharges of M. musicola and Didymella are most abundant from June through December whereas ascospores of Micronectriella are abundant from January to June. Ascospores of M. minima and especially Leptosphaeria are abundant at all times. The two-celled ascospores of M. musicola, M. minima, and Didymella are readily identified by size, shape, and type of germination. M. musicola perithecia can be readily distinguished in non-sectioned lactophenol-cleared leaf tissue by the dark thick walls of the ostiole and periderm. M. minima and Micronectriella can produce ascospores in siugle-ascospore cultures. The latter also produces Fusarium macroconidia. Micronectriella sp. is present in young healthy leaves and is considered a banana leaf inhabitant. Perithecia of all species are more abundant in areas of mass leaf spot infection than in single, scattered spots.

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First Report of Leaf Spot Disease on Walnut Caused by Colletotrichum fioriniae in China

Plant Disease ◽

10.1094/pdis-09-14-0938-pdn ◽

2015 ◽

Vol 99 (2) ◽

pp. 289-289 ◽

Cited By ~ 9

Author(s):

Y. Z. Zhu ◽

W. J. Liao ◽

D. X. Zou ◽

Y. J. Wu ◽

Y. Zhou

Keyword(s):

Dna Sequences ◽

Leaf Spot ◽

Juglans Regia ◽

Morphological Characteristics ◽

Leaf Spot Disease ◽

Koch’S Postulates ◽

First Report ◽

Spot Disease ◽

Leaf Spots ◽

Koch's Postulates

In May 2014, a severe leaf spot disease was observed on walnut tree (Juglans regia L.) in Hechi, Guangxi, China. Leaf spots were circular to semicircular in shape, water-soaked, later becoming grayish white in the center with a dark brown margin and bordered by a tan halo. Necrotic lesions were approximately 3 to 4 mm in diameter. Diseased leaves were collected from 10 trees in each of five commercial orchards. The diseased leaves were cut into 5 × 5 mm slices, dipped in 75% ethanol for 30 s, washed three times in sterilized water, sterilized with 0.1% (w/v) HgCl2 for 3 min, and then rinsed five times with sterile distilled water. These slices were placed on potato dextrose agar (PDA), followed by incubating at 28°C for about 3 to 4 days. Fungal isolates were obtained from these diseased tissues, transferred onto PDA plates, and incubated at 28°C. These isolates produced gray aerial mycelium and then became pinkish gray with age. Moreover, the reverse of the colony was pink. The growth rate was 8.21 to 8.41 mm per day (average = 8.29 ± 0.11, n = 3) at 28°C. The colonies produced pale orange conidial masses and were fusiform with acute ends, hyaline, sometimes guttulate, 4.02 to 5.25 × 13.71 to 15.72 μm (average = 4.56 ± 0.31 × 14.87 ± 1.14 μm, n = 25). The morphological characteristics and measurements of this fungal isolate matched the previous descriptions of Colletotrichum fioriniae (Marcelino & Gouli) R.G. Shivas & Y.P. Tan (2). Meanwhile, these characterizations were further confirmed by analysis of the partial sequence of five genes: the internal transcribed spacer (ITS) of the ribosomal DNA, beta-tubulin (β-tub) gene, glyceraldehyde 3-phosphate dehydrogenase (GAPDH) gene, chitin synthase 3(CHS-1) gene, and actin (ACT) gene, with universal primers ITS4/ITS5, T1/βt2b, GDF1/GDR1, CHS1-79F/CHS1-354R, and ACT-512F/ACT-783R, respectively (1). BLAST of these DNA sequences using the nucleotide database of GenBank showed a high identify (ITS, 99%; β-tub, 99%; GAPDH, 99%; CHS-1, 99%; and ACT, 100%) with the previously deposited sequences of C. fioriniae (ITS, KF278459.1, NR111747.1; β-tub, AB744079.1, AB690809.1; GAPDH, KF944355.1, KF944354.1; CHS-1, JQ948987.1, JQ949005.1; and ACT, JQ949625.1, JQ949626.1). Koch's postulates were fulfilled by inoculating six healthy 1-year-old walnut trees in July 2014 with maximum and minimum temperatures of 33 and 26°C. The 6-mm mycelial plug, which was cut from the margin of a 5-day-old colony of the fungus on PDA, was placed onto each pin-wounded leaf, ensuring good contact between the mycelium and the wound. Non-colonized PDA plugs were placed onto pin-wounds as negative controls. Following inoculation, both inoculated and control plants were covered with plastic bags. Leaf spots, similar to those on naturally infected plants, were observed on the leaves inoculated with C. fioriniae within 5 days. No symptoms were observed on the negative control leaves. Finally, C. fioriniae was re-isolated from symptomatic leaves; in contrast, no fungus was isolated from the control, which confirmed Koch's postulates. To our knowledge, this is the first report of leaf disease on walnut caused by C. fioriniae. References: (1) L. Cai et al. Fungal Divers. 39:183, 2009. (2) R. G. Shivas and Y. P. Tan. Fungal Divers. 39:111, 2009.

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First Report of Leaf Spot of Houttuynia cordata Caused by Alternaria alternata in China

Plant Disease ◽

10.1094/pdis-10-10-0724 ◽

2011 ◽

Vol 95 (3) ◽

pp. 359-359

Author(s):

L. Zheng ◽

R. Lv ◽

Q. Li ◽

J. Huang ◽

Y. Wang ◽

...

Keyword(s):

Alternaria Alternata ◽

Leaf Spot ◽

Southern China ◽

Sclerotium Rolfsii ◽

Tween 20 ◽

Herbaceous Plant ◽

Houttuynia Cordata ◽

First Report ◽

Perennial Herbaceous Plant ◽

Pathogenicity Tests

Houttuynia cordata is a perennial herbaceous plant (family Saururaceae) that is native to southern China, Japan, Korea, and Southeast Asia where it grows well in moist to wet soils. It is commonly used as a Chinese herbal medicine and as a vegetable. In North America and Europe it is also used as an ornamental. From September 2007 to November 2009, symptoms of leaf spot were found on H. cordata leaves in Dangyang County, Hubei, China, with the crop area affected estimated to be over 600 ha per year. Rhizome yield was reduced by 20% on average, with up to 70% yield losses in some fields during the autumn growing season. Lesions were initially small, brown, and oval or circular that developed into dark spots and sometimes formed target spots with white centers. These spots enlarged and overlapped, extending until the leaves withered entirely usually within 2 months. A fungus was consistently recovered from symptomatic leaf samples collected in October 2008 or 2009 with an average 90% isolation rate from ~60 leaf pieces that were surface sterilized with 0.1% mercuric chloride solution. Three isolates, HCDY-2, HCDY-3, and HCDY-4, were used to further evaluate characteristics of the pathogen. On potato dextrose agar, all cultures initially developed white colonies and the centers turned gray or brown after 4 days of incubation. Conidiophores were single or fasciculate, straight or knee curved, gray-brown with regular septa, and 42 to 61 × 4 to 5 μm. Conidia were obclavate or ovate, brown, and 26 to 38 × 12 to 20 μm with three to five transverse and one to three longitudinal or oblique septa. The tops of some conidia developed into secondary conidiophores, which were cylindrical, beige, and 5 to 17 × 3 to 5 μm. The pathogen was identified as Alternaria alternata based on descriptions in Simmons (3). Genomic DNA of HCDY-2 was extracted, and the rDNA-internal transcribed spacer sequence showed 99.6% identity to A. alternata (GenBank No. AY513941). Pathogenicity tests were performed with the three isolates by spraying conidial suspensions (1 × 106 conidia/ml) containing 0.1% Tween 20 onto upper and lower surfaces of leaves of 40-day-old 15-cm high plants. There were 20 leaves from five replicate plants for each isolate. Control plants were treated with sterilized water containing 0.1% Tween 20 only. All plants were incubated with a 16-h photoperiod at 25°C and 90% relative humidity in an artificial climate chamber. Five days after inoculation, typical brown spots were observed on all inoculated leaves but no symptoms were seen on water-treated control plants. Koch's postulates were fulfilled by reisolation of A. alternata from diseased leaves. The pathogenicity tests were carried out twice. A survey of the literature revealed only a few fungal diseases associated with H. cordata (1,2,4), including Phyllosticta houttuyniae, Pseudocercospora houttuyniae, Rhizoctonia solani, and Sclerotium rolfsii. Although A. alternata is a cosmopolitan plant pathogen, it has not been reported on any species in the four genera in Saururaceae (Anemopsis, Gymnotheca, Houttuynia, and Saururus) (3). To our knowledge, this is the first report of A. alternata infecting H. cordata worldwide. References: (1) Y. L. Guo and W. X. Zhao. Acta Mycol. Sin. 8:118, 1989. (2) K. Sawada. Spec. Publ. Taiwan Univ. 8:138, 1959. (3) E. G. Simmons. Alternaria: An Identification Manual. The American Phytopathological Society, St. Paul, MN, 2007. (4) Y. Wu et al. J. Changjiang Vegetables (In Chinese) 2:19, 2007.

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