scholarly journals Cylindrocladiella peruviana and Pleiocarpon algeriense causing stem and crown rot on avocado (Persea americana)

2020 ◽  
Vol 158 (2) ◽  
pp. 419-430
Author(s):  
Dalia Aiello ◽  
Giorgio Gusella ◽  
Alessandro Vitale ◽  
Vladimiro Guarnaccia ◽  
Giancarlo Polizzi
Keyword(s):  
Morphological Characterization ◽  
Persea Americana ◽  
Crown Rot ◽  
Koch’S Postulates ◽  
Fungal Isolates ◽  
Pathogenicity Tests ◽  
Old Trees ◽  
Koch's Postulates

Abstract During the winter of 2018, 3-years-old trees of avocado (Persea americana) cv “Hass” from Trapani province (Sicily, Italy) showed symptoms of stem and crown rot. Two different fungi were consistently isolated from infected tissues. Morphological characterization and multi-locus phylogenies using five genomic loci (ITS, tef1, tub2, his3, and rpb2) identified these fungi as Cylindrocladiella peruviana and Pleiocarpon algeriense. Pathogenicity tests on healthy 5-months-old seedlings and 3-year-old trees of avocado reproduced similar symptoms as those observed in nature, and Koch’s postulates were fulfilled for both pathogens. Moreover, the tested fungal isolates revealed a different pathogenic behaviour among two species. Two isolates of Pleiocarpon algeriense resulted more aggressive than Cylindrocladiella peruviana isolates causing major lesions on young seedlings. This study is the first to report of stem and crown rot on avocado caused by Cylindrocladiella peruviana and Pleiocarpon algeriense.

scholarly journals Colletotrichum species associated with anthracnose of Pyrus spp. in China

2019 ◽  
Vol 42 (1) ◽  
pp. 1-35 ◽  
Author(s):  
M. Fu ◽  
P.W. Crous ◽  
Q. Bai ◽  
P.F. Zhang ◽  
J. Xiang ◽  
...  
Keyword(s):  
Plant Pathogens ◽  
Novel Species ◽  
Phylogenetic Analyses ◽  
Koch’S Postulates ◽  
Colletotrichum Species ◽  
Organ Specific ◽  
Pathogenicity Tests ◽  
Koch's Postulates

Colletotrichum species are plant pathogens, saprobes, and endophytes on a range of economically important hosts. However, the species occurring on pear remain largely unresolved. To determine the morphology, phylogeny and biology of Colletotrichum species associated with Pyrus plants, a total of 295 samples were collected from cultivated pear species (including P. pyrifolia, P. bretschneideri, and P. communis) from seven major pear-cultivation provinces in China. The pear leaves and fruits affected by anthracnose were sampled and subjected to fungus isolation, resulting in a total of 488 Colletotrichum isolates. Phylogenetic analyses based on six loci (ACT, TUB2, CAL, CHS-1, GAPDH, and ITS) coupled with morphology of 90 representative isolates revealed that they belong to 10 known Colletotrichum species, including C. aenigma, C. citricola, C. conoides, C. fioriniae, C. fructicola, C. gloeosporioides, C. karstii, C. plurivorum, C. siamense, C. wuxiense, and two novel species, described here as C. jinshuiense and C. pyrifoliae. Of these, C. fructicola was the most dominant, occurring on P. pyrifolia and P. bretschneideri in all surveyed provinces except in Shandong, where C. siamense was dominant. In contrast, only C. siamense and C. fioriniae were isolated from P. communis, with the former being dominant. In order to prove Koch's postulates, pathogenicity tests on pear leaves and fruits revealed a broad diversity in pathogenicity and aggressiveness among the species and isolates, of which C. citricola, C. jinshuiense, C. pyrifoliae, and C. conoides appeared to be organ-specific on either leaves or fruits. This study also represents the first reports of C. citricola, C. conoides, C. karstii, C. plurivorum, C. siamense, and C. wuxiense causing anthracnose on pear.

scholarly journals Assessment of Fungal Pathogens Affecting the Weed Conyza bonariensis in Argentina

2018 ◽  
Vol 10 (3) ◽  
pp. 62
Author(s):  
Martin Bonacci ◽  
Ángela N. Formento ◽  
Fernando Daita ◽  
Melina Sartori ◽  
Miriam Etcheverry ◽  
...  
Keyword(s):  
Fungal Pathogens ◽  
Alternative Methods ◽  
Weed Species ◽  
Koch’S Postulates ◽  
Fungal Isolates ◽  
Conyza Bonariensis ◽  
Pesticide Reduction ◽  
Colletotrichum Spp ◽  
And Control ◽  
Koch's Postulates

In the last years Conyza bonariensis has become an important weed and control is difficult with the use of current technology in Argentinean pampas region. The increasing prevalence of herbicide-resistant weed species, public concern related to pesticide use and the introduction of government policies for pesticide reduction, is driving the search for alternative methods to chemical control. The aims of the present study were to detect fungal diseases associated with C. bonariensis, to identify fungal isolates from the symptomatic leaves and to confirm through Koch’s postulates the isolates pathogenicity. Mycological analysis of symptomatic leaves showed the presence of twelve genera of filamentous fungi. Among 116 isolates, Colletotrichum spp. was the most prevalent genus followed by Nigrospora spp. and Septoria spp. In the pathogenicity assays, 22 out of 116 isolates were able to comply with the Koch’s postulates. The pathogenic isolates were included into three genera Alternaria spp., Colletotrichum spp. and Septoria spp. This study provides the first report that demonstrates pathogenicity of fungal isolates on C. bonariensis in Argentina and represents the first step in a future biocontrol program.

Red Crown Rot of Hop in Oregon Caused by Phomopsis tuberivora

2013 ◽  
Vol 14 (1) ◽  
pp. 52
Author(s):  
David H. Gent ◽  
George Mueller-Warrant ◽  
Joanna L. Woods ◽  
Melodie L. Putnam ◽  
Megan C. Twomey
Keyword(s):  
Crown Rot ◽  
Management Implications ◽  
Koch’S Postulates ◽  
First Report ◽  
Red Crown Rot ◽  
Weak Growth ◽  
Koch's Postulates

During July 2007, symptoms including weak growth and death of plants of cultivar Fuggle were reported by a hop grower in Marion Co., OR. Phomopsis tuberivora H.T. Güssow & W.R. Foster 1932 was consistently recovered from affected plants. Koch's postulates were fulfilled with three isolates of the fungus, establishing the pathogen and the disease red crown rot as the cause of the damage. This is the first report of red crown rot on hop in Oregon, which may have important management implications for affected hop yards and farms. Accepted for publication 19 March 2013. Published 24 June 2013.

scholarly journals Recent Outbreak of Soybean Sudden Death Syndrome Caused by Fusarium virguliforme and F. tucumaniae in Argentina

Plant Disease ◽  
2004 ◽  
Vol 88 (9) ◽  
pp. 1044-1044 ◽  
Author(s):  
M. Scandiani ◽  
D. Ruberti ◽  
K. O'Donnell ◽  
T. Aoki ◽  
R. Pioli ◽  
...  
Keyword(s):  
United States ◽  
Phylogenetic Analyses ◽  
The United States ◽  
Positive Control ◽  
Koch’S Postulates ◽  
First Report ◽  
Molecular Phylogenetic ◽  
Soil Infestation ◽  
Pathogenicity Tests ◽  
Koch's Postulates

Sudden death syndrome (SDS) of soybean was detected initially in Argentina during 1991-1992 in the Pampas Region and 1992-1993 in the Northwest Region. The first report of the fulfillment of Koch's postulates of SDS caused by Fusarium solani f. sp. glycines in Argentina was published in 2003 (3). Subsequently, analyses have shown that F. solani f. sp. glycines represents several morphologically and phylogenetically distinct species, including F. tucumaniae in Argentina and F. virguliforme in the United States (1). Isolations were made from plants that exhibited typical SDS symptoms (interveinal foliar chlorosis and necrosis leading to defoliation of the leaflets but not the petioles) from fields in Santa Fe and Buenos Aires provinces in 2001, 2002, and 2003. To determine which species are responsible for SDS in Argentina, cultures of eight slow growing isolates that developed bluish pigmentation and produced abundant macroconidia in sporodochia on potato dextrose agar were subjected to morphological and molecular phylogenetic analyses and pathogenicity tests. Morphological analyses demonstrated that three of the isolates were F. virguliforme and five were F. tucumaniae. Isolates of F. tucumaniae produced long and narrow sporodochial conidia while F. virguliforme produced diagnostic comma-shaped conidia. Molecular phylogenetic analyses of DNA sequences from multiple loci confirmed morphology-based identifications and showed that the soybean SDS pathogen in the United States, F. virguliforme, was also present in Argentina. To our knowledge, this is the first report of F. virguliforme in Argentina and of this pathogen outside the United States. Five isolates of F. tucumaniae and three isolates of F. virguliforme were used for pathogenicity tests. F. virguliforme isolate 171 provided by J. Rupe (University of Arkansas, Fayetteville) was used as a positive control. Soybean cultivars Ripley, RA 702, Pioneer 9492RR, Spencer, and A-6445RG were inoculated with each of the isolates tested in a greenhouse assay using soil infestation and toothpick methods (2). All eight isolates produced typical foliar SDS symptoms 15 to 25 days after inoculation. Severity of foliar symptoms averaged 3.3 for F. virguliforme, 2.6 for F. tucumaniae, and 3.3 for the positive control using a disease severity scale in which 1 = no symptoms and 5 = severely infected or dead plants. Under these conditions, F. virguliforme appeared to be more virulent than F tucumaniae. Noninoculated plants remained symptomless. Koch's postulates were confirmed with soybean cultivars RA 702 and A6445RG. Isolates recovered from symptomatic plants inoculated by the soil infestation and toothpick methods were identical to those used to inoculate the plant. Strains were recovered at frequencies of 100 and 60% from plants inoculated by the toothpick and soil infestation methods, respectively. To our knowledge, this is the first report of the fulfillment of Koch's postulates for F. tucumaniae and F. virguliforme in Argentina. References: (1) T. Aoki et al. Mycologia 95:660, 2003. (2) K. W. Roy et al. Plant Dis. 81:1100, 1997 (3) M. Scandiani et al. Plant Dis. 87:447, 2003.

scholarly journals First Report of Pilidiella granati on Pomegranate with Symptoms of Crown Rot in the Prefecture of Xanthi, Greece

Plant Disease ◽  
2011 ◽  
Vol 95 (1) ◽  
pp. 79-79 ◽  
Author(s):  
T. Thomidis ◽  
E. Exadaktylou
Keyword(s):  
Potato Dextrose Agar ◽  
Crown Rot ◽  
Fruit Rot ◽  
Adhesive Tape ◽  
Petroleum Jelly ◽  
Koch’S Postulates ◽  
First Report ◽  
Agar Plug ◽  
Pilidiella Granati ◽  
Koch's Postulates

In spring 2010, plants of pomegranate (Punica granatum L.) cv. Wonderful with symptoms of crown rot were observed in the Prefecture of Xanthi, Thrace, Greece. Close examination of these plants revealed distinct symptoms of crown rots. Isolations from the lower margins of the necrotic area were made by plating tissues of approximately 3 mm on acidified (2.5 ml of 85% lactic acid per liter of nutrient medium to create a pH = 3.5 after autoclaving) potato dextrose agar. The plates were incubated at 23°C for 5 to 7 days, and consistent colonies with light yellow, leathery mycelia and abundant, black, solitary pycnidia of various sizes were observed. Hyphae were septate and conidia were hyaline, one-celled, and ellipsoid to fusiform (average 10.1 to 20.2 × 3.2 to 4.3 μm). The pathogen was identified as Pilidiella granati Saccardo (synonym Coniella granati (Saccardo) Petrak & Sydow (3)) based on mycelium and spore morphology and ribosomal ITS1-5.8S-ITS2 sequences, which were identical to GenBank No. FN908875. Koch's postulates were completed in the laboratory by inoculating 20 1-year-old plants of pomegranate cv. Wonderful. With a 7-mm-diameter cork borer, a wound was created in the middle of each collar by removing the bark. A 6-mm-diameter agar plug bearing mycelia and spores from a 15-day-old culture of P. granati was inserted into each wound. The wound was covered with petroleum jelly and wrapped with adhesive tape to prevent desiccation. Ten trees were inoculated with sterile potato dextrose agar plugs to serve as controls. All plants were incubated at 25°C for 10 days, at which time necrosis was observed. Koch's postulates were satisfied after reisolating the fungus from inoculated plants that developed symptoms similar to those observed in the field. Control plants produced no symptoms of disease. To our knowledge, this is the first report of P. granati from pomegranate plants with symptoms of crown rots in Greece. The role of predisposing factors such as herbicides and frost damage to infection by P. granati is unknown. This pathogen has been reported to cause fruit rot of pomegranate in Spain (2) and California (1). References: (1) T. J. Michailides et al. (Abstr.) Phytopathology 100(suppl.):S83, 2010. (2) L. Palou et al. New Dis. Rep. Online publication. doi:10.5197/j.2044-0588.2010.022.021, 2010. (3) G T. Tziros and K. Tzavella-Klonari. Plant Pathol. 57:783, 2007.

First Report of Crown Rot Caused by Phytophthora tropicalis on Gloxinia in North Carolina

2010 ◽  
Vol 11 (1) ◽  
pp. 47 ◽  
Author(s):  
Heather A. Olson ◽  
D. Michael Benson
Keyword(s):  
North Carolina ◽  
Its Rdna ◽  
Crown Rot ◽  
Successful Completion ◽  
Koch’S Postulates ◽  
First Report ◽  
Koch's Postulates

In 2007, wilting and crown rot were observed on recently transplanted gloxinias (a popular ornamental houseplant) in a commercial greenhouse in North Carolina. The pathogen was identified as Phytophthora tropicalis based on morphology and sequencing of the ITS rDNA region. Pathogenicity of the isolates to gloxinia was confirmed by successful completion of Koch's postulates. To our knowledge, this is the first report of Phytophthora tropicalis on gloxinia. Accepted for publication 2 June 2010. Published 8 July 2010.

scholarly journals Neofusicoccum spp. Associated with Stem Canker and Dieback of Blueberry in Chile

Plant Disease ◽  
2009 ◽  
Vol 93 (11) ◽  
pp. 1187-1194 ◽  
Author(s):  
J. G. Espinoza ◽  
E. X. Briceño ◽  
E. R. Chávez ◽  
J. R. Úrbez-Torres ◽  
B. A. Latorre
Keyword(s):  
Sequence Analysis ◽  
Nucleotide Sequence ◽  
Internal Transcribed Spacer ◽  
Its Region ◽  
Stem Canker ◽  
Nucleotide Sequence Analysis ◽  
Susceptible Cultivar ◽  
Koch’S Postulates ◽  
Pathogenicity Tests ◽  
Koch's Postulates

Blueberry (Vaccinium spp.) plantings have significantly increased in Chile during the last decade and, currently, over 10,700 ha are cultivated throughout the country. Among other diseases, stem canker and dieback has been frequently observed in commercial plantations with incidences between 15 and 45%. The aim of this study was to identify and characterize Neofusicoccum spp. causing stem canker and dieback of blueberry in Chile. Three species, N. arbuti, N. australe, and N. parvum, were identified based on colony and conidia morphology, and nucleotide sequence analysis of the internal transcribed spacer (ITS) region (ITS1-5.8S-ITS2). These Neofusicoccum spp. were found alone or coexisting with Pestalotiopsis spp., Truncatella spp., or Phomopsis spp. Koch's postulates showed all Neofusicoccum spp. isolated from infected plants to be pathogenic when inoculated on blueberry fruit and twigs using both mycelia and conidia suspension. All blueberry cultivars tested, including, Brigitta, Bluecrop, Brightwell, Duke, Elliott, Misty, and O'Neal, were susceptible to Neofusicoccum spp. infection. Pathogenicity tests showed N. parvum to be the most virulent species and Elliott to be the most susceptible cultivar. This report represents the first description of N. arbuti, N. australe, and N. parvum as canker-causing agents on blueberry in Chile.

scholarly journals Morphology Characterization, Molecular Phylogeny, and Pathogenicity of Diaporthe passifloricola on Citrus reticulata cv. Nanfengmiju in Jiangxi Province, China

Plants ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 218
Author(s):  
Chingchai Chaisiri ◽  
Xiang-Yu Liu ◽  
Wei-Xiao Yin ◽  
Chao-Xi Luo ◽  
Yang Lin
Keyword(s):  
Phylogenetic Analyses ◽  
Citrus Fruit ◽  
Epidemiological Studies ◽  
Morphological Characterization ◽  
Jiangxi Province ◽  
Citrus Reticulata ◽  
Fruit Storage ◽  
Pathogenicity Tests ◽  
Rot Disease ◽  
Morphology Characterization

The Nanfengmiju (Citrus reticulata cv. Nanfengmiju), a high-quality local variety of mandarin, is one of the major fruit crops in Jiangxi Province, China. Citrus melanose and stem-end rot, two common fungal diseases of Nanfengmiju, are both caused by Diaporthe spp. (syn. Phomopsis spp.). Identification of the Diaporthe species is essential for epidemiological studies, quarantine measures, and management of diseases caused by these fungi. Melanose disease was observed on Nanfengmiju fruit in Jiangxi Province of China in 2016. Based on morphological characterization and multi-locus phylogenetic analyses, three out of 39 isolates from diseased samples were identified as D. passifloricola. Since these three isolates did not cause melanose on citrus fruit in the pathogenicity tests, they were presumed to be endophytic fungi present in the diseased tissues. However, our results indicate that D. passifloricola may persist as a symptom-less endophyte in the peel of citrus fruit, yet it may cause stem-end if it invades the stem end during fruit storage. To the best of our knowledge, this is the first report of D. passifloricola as the causal agent of the stem-end rot disease in Citrusreticulata cv. Nanfengmiju.

First Report of Pathogenicity of Fusarium sporotrichioides and Fusarium acuminatum on Sunflowers in the United States

2010 ◽  
Vol 11 (1) ◽  
pp. 42 ◽  
Author(s):  
F. Mathew ◽  
B. Kirkeide ◽  
T. Gulya ◽  
S. Markell
Keyword(s):  
United States ◽  
Helianthus Annuus ◽  
The United States ◽  
Fusarium Sporotrichioides ◽  
Charcoal Rot ◽  
Koch’S Postulates ◽  
First Report ◽  
Fusarium Acuminatum ◽  
Helianthus Annuus L ◽  
Koch's Postulates

Widespread infection of charcoal rot was observed in a commercial sunflower field in Minnesota in September 2009. Based on morphology, isolates were identified as F. sporotrichioides and F. acuminatum. Koch's postulates demonstrated pathogencity of both species. To our knowledge, this is the first report of F. sporotrichoides and F. acuminatum causing disease on Helianthus annuus L. in the United States. Accepted for publication 23 August 2010. Published 15 September 2010.

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