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

1963 ◽  
Vol 41 (10) ◽  
pp. 1481-1485 ◽  
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.

Effects of crop rotations and fertilizer management on leaf spotting diseases of spring wheat in southwestern Saskatchewan

1998 ◽  
Vol 78 (3) ◽  
pp. 489-496 ◽  
Author(s):  
M. R. Fernandez ◽  
R. P. Zentner ◽  
B. G. McConkey ◽  
C. A. Campbell
Keyword(s):  
Spring Wheat ◽  
Leaf Spot ◽  
Leaf Tissue ◽  
Triticum Aestivum L ◽  
Fertilizer Application ◽  
Tan Spot ◽  
P Deficiency ◽  
Pyrenophora Tritici Repentis ◽  
Leaf Spots ◽  
Phaeosphaeria Nodorum

The objective of this study was to determine the effect of crop sequence, summerfallow frequency, and fertilizer application, on the severity of leaf spotting diseases of spring wheat (Triticum aestivum L.). In the field experiment examined, Pyrenophora tritici-repentis (Died.) Drechs. was the pathogen most commonly isolated from lesioned leaf tissue, followed by stagonospora blotch (Phaeosphaeria nodorum [E. Müller] Hedjaroude). The severity of leaf spots in wheat after fallow was greater than in monoculture continuous wheat, or in wheat after a noncereal crop. Percent area with leaf spots in wheat grown after wheat was higher than in wheat grown after flax (Linum usitatissimum L.) or lentil (Lens culinaris Medikus) in years with high disease pressure (1995 and 1996), but not in 1993 or 1994 when overall disease levels were low. Under soil N-deficient conditions, leaf spot levels increased in years with dry summers (1994 and 1996), whereas a P deficiency decreased leaf spot severity in years that had cool and wet springs (1995 and 1996). A survey of producers' fields confirmed the observations made in the research plots, in particular, wheat after wheat was not more severely diseased than wheat grown in rotation with a noncereal crop. We concluded that the use of fallow, or 1 yr of rotation with a noncereal crop, will not reduce leaf spotting diseases of spring wheat in southwestern Saskatchewan. The best rotation aimed at reducing the levels of disease appeared to be 2 consecutive years of spring wheat, followed by at least 2 yr of a noncereal crop, or by a noncereal crop and summerfallow. Key words: Leaf spot, tan spot, Pyrenophora tritici-repentis, stagonospora blotch, Phaeosphaeria nodorum, septoria blotch, Mycosphaerella graminicola, crop rotation, tillage, fertility

scholarly journals First Report of a Leaf Spot on Hazel Leaves Caused by Phyllosticta coryli in Liaoning Province of China

Plant Disease ◽  
2013 ◽  
Vol 97 (9) ◽  
pp. 1254-1254 ◽  
Author(s):  
J. Sun ◽  
D.-M. Wang ◽  
X.-Y. Huang ◽  
Z.-H. Liu
Keyword(s):  
Leaf Spot ◽  
Control Strategies ◽  
Morphological Characteristics ◽  
Leaf Tissue ◽  
Its Region ◽  
Liaoning Province ◽  
Single Spore ◽  
First Report ◽  
Leaf Spots ◽  
Microscopic Morphology

Hazel (Corylus heterophylla Fischl) is an important nut tree grown in China, especially in Liaoning Province, and is rich in nutritional and medicinal values. In August 2011, leaf spotting was observed on hybrid hazel (Dawei) leaves in Paotai Town, Wafangdian County of Liaoning Province. By August 2012, the disease had spread to Zhangdang Town, Fushun County. Symptoms initially appeared on both sides of leaves as pinpoint brown spots, which enlarged and developed into regular, dark brown lesions, 3 to 9 mm in diameter. The lesions were lighter in color in the center compared to the margin. To identify the pathogen, leaf pieces (3 to 5 mm) taken from the margins, including both symptomatic and healthy portions of leaf tissue, were surface-disinfected first in 75% ethanol for 5 s, next in 0.1% aqueous mercuric chloride for 50 s, and then rinsed with sterilized water three times. Leaf pieces were incubated on potato dextrose agar (PDA) at 25°C for 14 days in darkness. Single spore isolates were obtained from individual conidia. For studies of microscopic morphology, isolates were grown on synthetic nutrient agar (SNA) in slide cultures. Colonies grew up to 45 to 48 mm in diameter on PDA after 14 days. Pycnidia appeared on the colonies after 12 days. Conidiophores were short. Pycnidia were dark brown, subglobose, and 150 to 205 μm in diameter. Conidia were unicellular, colorless, ovoid to oval, and from 2.4 to 4.5 × 1.6 to 2.4 μm. On the basis of these morphological characteristics, the isolates were tentatively identified as Phyllosticta coryli Westend (2). The rDNA internal transcribed spacer (ITS) region was amplified using primers ITS1 and ITS4 and sequenced (GenBank Accession No. KC196068). The 490-bp amplicons had 100% identity to an undescribed Phyllosticta species isolated from Cornus macrophylla in Gansu, Tianshui, China (AB470897). On the basis of morphological characteristics and nucleotide homology, the isolate was tentatively identified as P. coryli. Koch's postulates were fulfilled in the growth chamber on hazelnut leaves inoculated with P. coryli conidial suspensions (107 conidia ml–1). Eight inoculated 1-year-old seedlings (Dawei) were incubated under moist conditions for 8 to 10 days at 25°C. All leaf spots that developed on inoculated leaves were similar in appearance to those observed on diseased hazel leaves in the field. P. coryli was recovered from lesions and its identity was confirmed by morphological characteristics. P. coryli was first reported as a pathogen of hazel leaves in Bull of Belgium (2). In China, P. coryli was first reported on Corylus heterophylla Fisch. in Jilin Province (1). To our knowledge, this is the first report of P. coryli causing leaf spot on hybrid hazel in Liaoning Province of China. The outbreak and spread of this disease may decrease the yield of hazelnut in northern regions of China. More studies are needed on control strategies, including the possible resistance of hazel cultivars to P. coryli. References: (1) Y. Li et al. J. Shenyang Agric. Univ. 25:153, 1994. (2) P. A. Saccardo. Sylloge Fungorum Vol. III, page 31, 1884.

scholarly journals First Report of Hainesia lythri Causing Leaf Spots of Paeonia suffruticosa in China

Plant Disease ◽  
2008 ◽  
Vol 92 (3) ◽  
pp. 486-486
Author(s):  
M. Zhang ◽  
H. L. Li ◽  
A. L. Zhao ◽  
J. X. Zhang
Keyword(s):  
Leaf Spot ◽  
Leaf Tissue ◽  
Causal Agent ◽  
Plant Diseases ◽  
Acer Pseudoplatanus ◽  
Paeonia Suffruticosa ◽  
Tree Peony ◽  
Korean Society ◽  
First Report ◽  
Leaf Spots

Tree peony (Paeonia suffruticosa) is known as “the king of flowers” for its beautiful and showy flowers. It is regarded as the symbol flower of China and is cultivated throughout the country. During the summer of 2006, a leaf spot was observed on tree peony cultivated in the Zhengzhou area of Henan Province, and in 2007, the leaf spot was observed in the Luoyang area. In some gardens, the leaf spot affected more than 50% of the plants. Early symptoms appeared as small, round, water-soaked lesions on the leaves. Lesions expanded into 5 to 35-mm-diameter spots that were circular or irregular, brown to dark brown, with pale brown margins. Later, the center of some lesions dropped out. Signs of the suspected pathogen were usually seen on the leaf spots after an abundant rainfall. Lesions contained numerous, pale brown, cupulate conidiomata with salmon-colored spore masses. Conidiophores (70 × 1 to 2 μm) were hyaline, branched, septate, and filiform. Conidia (5.5 to 7.5 × 1.5 to 2 μm) were hyaline, aseptate, and cymbiform to allantoid. The pathogen was identified as Hainesia lythri on the basis of the morphology. This fungus infects a wide variety of hosts including P. suffruticosa, Acer pseudoplatanus, Calluna sp., Dissotis paucistellata, Epilobium angustifolium, and Eucalyptus saligna (3). The fungus was isolated on potato dextrose agar (PDA) medium using conidia from conidiomata found on symptomatic leaf tissue; the fungus produced gray-to-brown colonies. Pathogenicity was tested by inoculating 10 leaves on one 5-year-old tree with a mycelia plug from the colony (0.5 cm in diameter); leaves inoculated with plugs of PDA medium served as controls. Inoculated leaves were covered with plastic for 24 h to maintain high relative humidity and incubated at 25 to 28°C. After 5 days, 100% of the inoculated leaves showed symptoms identical to those observed on leaves from P. suffruticosa infected in the field while controls remained symptom free. Reisolation of the fungus from lesions on inoculated leaves confirmed that the causal agent was H. lythri. Thus, we concluded that H. lythri is the causal agent of leaf spots of P. suffruticosa. To our knowledge, this is the first report of H. lythri infecting P. suffruticosa in China. H. lythri has been previously reported on Paeonia in Japan and Korea (1,2). References: (1) W. D. Cho and H. D. Shin, eds. List of Plant Diseases in Korea. 4th ed. Korean Society of Plant Pathology, 2004. (2) M. E. Palm. Mycologia 83:787, 1991. (3) B. C. Sutton. The Coelomycetes. CAB International Publishing, New York, 1980.

scholarly journals First Report of Botrytis cinerea Causing Leaf Spot of Aquilegia vulgaris in Japan

Plant Disease ◽  
2009 ◽  
Vol 93 (4) ◽  
pp. 425-425 ◽  
Author(s):  
M. Zhang ◽  
T. Tsukiboshi ◽  
I. Okabe
Keyword(s):  
United States ◽  
Botrytis Cinerea ◽  
Leaf Spot ◽  
Leaf Tissue ◽  
The United States ◽  
Plant Diseases ◽  
Its2 Region ◽  
Commonwealth Mycological Institute ◽  
First Report ◽  
Leaf Spots

European columbine, Aquilegia vulgaris L., Ranunculaceae, is an herbaceous flower widely used in gardens, parterres, and courtyards and is a traditional herbal plant. During the summer of 2008, leaf spots were observed on a plant cultivated along a roadside area in Nasushiobara, Tochigi, Japan. In some courtyards, the leaf spot affected more than 60% of the plants. Early symptoms appeared as small, round or elliptic, brown lesions on the leaves. Lesions expanded to 5 to 15 × 4 to 10 mm, irregular spots that were dark brown to black in the middle, with pale yellow-brown or purple-brown margins. In continuously wet or humid conditions, thick, gray mycelium and conidia appeared on the surface of leaf spots. Conidiophores were melanized at the base and hyaline near the apex, branched, and septated (approximately 3 mm × 16 to 18 μm). Conidia were hyaline, aseptate, ellipsoidal to obovoid, with a slightly protuberant hilum, and ranged from 9 to 14.5 × 5.5 to 6.5 μm. The pathogen was identified as Botrytis cinerea Pers.:Fr on the basis of morphology and sequence of ITS1-5.8s-ITS2 region of rDNA. The sequence (GenBank Accession No. FJ424510) exactly matched the sequences of two Botryotinia fuckeliana (anamorph Botrytis cinerea), (e.g., GenBank Accession Nos. AY686865 and FJ169666) (2). The fungus was isolated on potato dextrose agar (PDA) from a single conidium found on the symptomatic leaf tissue. Colonies of B. cinerea were first hyaline and later turned gray to black when the spores differentiated. Koch's postulates were performed with three whole plants of potted aquilegia. Leaves were inoculated with mycelia plugs harvested from the periphery of a 7-day-old colony; an equal number of plants were inoculated with the plugs of PDA medium only and served as controls. All plants were covered with plastic bags for 24 h to maintain high relative humidity and incubated at 25°C. After 8 days, all mycelium-inoculated plants showed symptoms identical to those observed on leaves from A. vulgaris infected in the field, whereas controls remained symptom free. Reisolation of the fungus from lesions on inoculated leaves confirmed that the causal agent was B. cinerea. B. cinerea has been previously reported on A. vulgaris in the United States and China (1,3). To our knowledge, this is the first report of leaf spots caused by B. cinerea on A. vulgaris in Japan. References: (1) Anonymous. Index of Plant Diseases in the United States. USDA Agric. Handb. No 165, 1960. (2) M. B. Ellis. Dematiaceous Hyphomycetes. Commonwealth Mycological Institute, Kew, England, 1971. (3) Z. Y. Zhang. Flora Fungorum Sinicorum. Vol. 26. Botrytis, Ramularia. Science Press, Beijing, 2006.

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

Plant Disease ◽  
2020 ◽  
Author(s):  
Muhammad Subhan Shafique ◽  
Luqman Amrao ◽  
Saba Saeed ◽  
Muhammad Zeshan Ahmed ◽  
Salman Ghuffar ◽  
...  
Keyword(s):  
Dna Sequences ◽  
Alternaria Alternata ◽  
Leaf Spot ◽  
Disease Incidence ◽  
Solanum Melongena ◽  
Leaf Tissue ◽  
Morphological Characters ◽  
Tween 20 ◽  
Family Farms ◽  
Leaf Spots

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.

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

Plant Disease ◽  
2012 ◽  
Vol 96 (5) ◽  
pp. 763-763 ◽  
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.

scholarly journals First Report of Alternaria alternata Causing Leaf Spot on Aloe vera in Louisiana

Plant Disease ◽  
2012 ◽  
Vol 96 (9) ◽  
pp. 1379-1379 ◽  
Author(s):  
W. L. da Silva ◽  
R. Singh
Keyword(s):  
Leaf Spot ◽  
Aloe Vera ◽  
Leaf Tissue ◽  
Infected Leaf ◽  
First Report ◽  
Succulent Plant ◽  
Leaf Spots ◽  
The Usa ◽  
Catalogue Raisonne ◽  
Aloe Gel

Aloe vera (L.) Burm. f. is a perennial succulent plant that is grown worldwide mainly for medicinal and cosmetic uses. In the USA, it is mainly cultivated in some southern states to produce aloe gel for the cosmetic industry (3), and in Louisiana it is also sold commercially as an ornamental. During the summer of 2011, several A. vera plants infected with leaf spots were observed on the campus of Louisiana State University, Baton Rouge. Large, necrotic, sunken, circular to oval, dark brown spots were present on both surfaces of the leaves. Infected leaf tissue pieces were surface disinfested with 1% NaOCl solution for 1 min and plated on potato dextrose agar (PDA). Plates were incubated at 28°C in the dark for 4 days. A dark olivaceous fungus with profuse golden brown, branched, and septate hyphae was consistently isolated from the infected tissue on PDA. The fungus produced conidia with longitudinal and transverse septa, and was morphologically identified as an Alternaria sp. (4). Conidia were produced in long chains, pale to light brown, obpyriform, with a beak (6.0 μm long), one to seven transverse and up to three longitudinal septa, and measured 10 to 45 μm long × 7 to 18 μm wide. Conidiophores were straight, septate, light to olive golden brown with conidial scar, and measured 35 to 100 μm long × 2 to 5 μm wide. Genomic DNA from a single-spored isolate was extracted and the internal transcribed spacer (ITS1-5.8s-ITS2) regions were amplified and sequenced using primers ITS1 and ITS4. BLASTn analysis of a 486-bp sequence (GenBank Accession No. JQ409455) resulted in 100% homology with A. alternata strain DHMJ16 (GenBank Accession No. JN986768) from China and several other Alternaria spp. The fungus was identified as A. alternata based on mycelial and conidia characters after being grown under standard, previously described conditions (4). Pathogenicity tests were carried out by inoculating six potted aloe plants with 0.5-cm diameter discs taken from a 6-day-old culture grown on PDA. Four discs were placed on the upper surface of each of the bottom leaves of every plant. Inoculated plants were individually covered with a plastic bag and maintained in a greenhouse for 1 week at 25 ± 2°C. Six control plants received only agar plugs. Seven days after inoculation, necrotic leaf spots were observed on the inoculated plants and A. alternata was reisolated from these spots. No leaf spots were observed on control plants. To the best of our knowledge, this is the first report of leaf spot caused by A. alternata on A. vera in Louisiana. Several outbreaks of the disease have been reported in Pakistan and India as damaging aloe gel production in those countries (1,2). An outbreak of this disease in Louisiana could represent a serious issue for the state's A. vera ornamental commerce. References: (1) R. Bajwa et al. Can. J. Plant Pathol. 32:490, 2010. (2) A. Kamalakannan et al. Australas. Plant Dis. Notes 3:110, 2008. (3) T. Reynolds. Aloes: The Genus Aloe. CRC Press, Boca Raton, FL, 2004. (4) E. G. Simmons. Alternaria: An Identification Manual: Fully Illustrated and with Catalogue Raisonné 1796-2007. CBS Fungal Biodiversity Centre, Utrecht, The Netherlands, 2007.

scholarly journals Molecular Phylogenetic Diversity and Biological Characterization of Diaporthe Species Associated with Leaf Spots of Camellia sinensis in Taiwan

Plants ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1434
Author(s):  
Hiran A. Ariyawansa ◽  
Ichen Tsai ◽  
Jian-Yuan Wang ◽  
Patchareeya Withee ◽  
Medsaii Tanjira ◽  
...  
Keyword(s):  
Camellia Sinensis ◽  
Leaf Spot ◽  
Phylogenetic Trees ◽  
Fungal Infections ◽  
Elongation Factor ◽  
Fungal Species ◽  
Tea Leaves ◽  
Phenotypic Characters ◽  
Leaf Spots ◽  
Molecular Phylogenetic

Camellia sinensis is one of the major crops grown in Taiwan and has been widely cultivated around the island. Tea leaves are prone to various fungal infections, and leaf spot is considered one of the major diseases in Taiwan tea fields. As part of a survey on fungal species causing leaf spots on tea leaves in Taiwan, 19 fungal strains morphologically similar to the genus Diaporthe were collected. ITS (internal transcribed spacer), tef1-α (translation elongation factor 1-α), tub2 (beta-tubulin), and cal (calmodulin) gene regions were used to construct phylogenetic trees and determine the evolutionary relationships among the collected strains. In total, six Diaporthe species, including one new species, Diaporthe hsinchuensis, were identified as linked with leaf spot of C. sinensis in Taiwan based on both phenotypic characters and phylogeny. These species were further characterized in terms of their pathogenicity, temperature, and pH requirements under laboratory conditions. Diaporthe tulliensis, D. passiflorae, and D. perseae were isolated from C. sinensis for the first time. Furthermore, pathogenicity tests revealed that, with wound inoculation, only D. hongkongensis was pathogenic on tea leaves. This investigation delivers the first assessment of Diaporthe taxa related to leaf spots on tea in Taiwan.

scholarly journals Photosynthesis of Blueberry Leaves as Affected by Septoria Leaf Spot and Abiotic Leaf Damage

Plant Disease ◽  
2004 ◽  
Vol 88 (4) ◽  
pp. 397-401 ◽  
Author(s):  
I. Roloff ◽  
H. Scherm ◽  
M. W. van Iersel
Keyword(s):  
Leaf Area ◽  
Disease Severity ◽  
Leaf Spot ◽  
Abiotic Factors ◽  
Lesion Size ◽  
Leaf Conductance ◽  
Yield Potential ◽  
Leaf Spots ◽  
Virtual Lesion ◽  
Septoria Leaf Spot

Leaf spots caused by fungal pathogens or abiotic factors can be prevalent on southern blueberries after harvest during the summer and fall, yet little is known about how they affect physiological processes that determine yield potential for the following year. In this study, we measured CO2 assimilation and leaf conductance on field-grown blueberry plants affected by Septoria leaf spot (caused by Septoria albopunctata) or by edema-like abiotic leaf blotching. Net assimilation rate (NAR) on healthy leaves varied between 6.9 and 12.4 μmol m-2 s-1 across cultivars and measurement dates. Infection by S. albopunctata had a significant negative effect on photosynthesis, with NAR decreasing exponentially as disease severity increased (R2 ≥0.726, P < 0.0001). NAR was reduced by approximately one-half at 20% disease severity, and values approached zero for leaves with >50% necrotic leaf area. There was a positive, linear correlation between NAR and leaf conductance (R2 ≥ 0.622, P < 0.0001), suggesting that the disease may have reduced photosynthesis via decreased CO2 diffusion into affected leaves. Estimates of virtual lesion size associated with infection by S. albopunctata ranged from 2.8 to 3.1, indicating that the leaf area in which photosynthesis was impaired was about three times as large as the area covered by necrosis. For leaves afflicted by edema-like damage, there also was a significant negative relationship between NAR and affected leaf area, but the scatter about the regression was more pronounced than in the NAR-disease severity relationships for S. albopunctata (R2 = 0.548, P < 0.0001). No significant correlation was observed between leaf conductance and affected area on these leaves (P = 0.145), and the virtual lesion size associated with abiotic damage was significantly smaller than that caused by S. albopunctata. Adequate carbohydrate supply during the fall is critical for optimal flower bud set in blueberry; therefore, these results document the potential for marked yield losses due to biotic and abiotic leaf spots.

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