scholarly journals First Report of Phytophthora nicotianae Causing Dianthus chinensis root rot and foliage blight in China

Plant Disease ◽  
2021 ◽  
Author(s):  
Jieying Xu ◽  
Xiao Yang ◽  
Cuiping Wu ◽  
Ziwei Zhou ◽  
Zhenpeng Chen ◽  
...  
Keyword(s):  
Root Rot ◽  
Large Subunit ◽  
Severe Infection ◽  
Average Diameter ◽  
Phytophthora Nicotianae ◽  
Crown Rot ◽  
Molecular Evidence ◽  
First Report ◽  
Whole Plant ◽  
Foliage Blight

Dianthus chinensis is a popular ornamental plant that is widely cultivated in China. From May 2020 to 2021, root rot and foliage blight were observed on approximately 50% groundcover plants at several landscape sites of Xuanwuhu Park and Nanjing Railway Station, China. Symptoms of wilting and chlorosis appeared in the initial stage, and severe infection caused the whole plant to die . To recover the causal pathogen, infected root and leaf samples were cut into 5×5 mm2 squares, surface-disinfected in 70% ethanol for 30 sec, placed onto 10% clarified V8 PARP agar at 25°C . After three days, Phytophthora-like hyphae were visibly emerged from both root and leaf tissues and growing into cV8A. Individual hyphal tips were transferred to new cV8A plates to obtain a total of 10 pure isolates. Colony morphology of all isolates on cV8A had slightly radiate to stellate patterns with cottony aerial mycelia. After four or five days all isolates had identical morphological traits including papillate and noncaducous sporangia on cV8, hyphal swellings, and intercalary and terminal chlamydospores. A representative isolate Pni-dc7 was examined for morphological measurements. Sporangia were mostly ovoid and sometimes obpyriform, averaging 28.9±5.6 µm in length and 24.9±5.8 µm in width (n=30). Chlamydospores were abundant and spherical with an average diameter at 29.2 ± 0.3 µm (n=30). Oogonia were not observed. For sequence analysis, the internal transcribed spacer (ITS) regions and large subunit (LSU) of the nuclear ribosomal RNA gene complex were amplified using the primer pairs ITS1/ITS4 and NL1/NL4 , respectively, while the mitochondrial cytochrome c oxidase subunit II (coxII) gene was amplified using FM58/FM66 (Martin et al. 2003). The ITS sequence of isolate Pni-dc7 (GenBank Acc. No. MZ519893) had a 100% identity to those of P. nicotianae (MH219914, KU172524, MT065839). The LSU sequence (MZ573547) had a 100% identity to those of P. nicotianae (KX250514, MZ348950, HQ665198).The cox2 sequence (MZ519893) had a 100% identity to those of P. nicotianae (MH221078, KJ506439, JF707072). Based on morphological and molecular evidence, Pni-dc7 was identified as P. nicotianae. Pathogenicity tests  were conducted using both detached leaves and whole plants. Asymptomatic leaves were collected from healthy plants.A 5×5 mm2 Pni-dc7-colonized cV8A plug was placed on each wound of five leaves. Sterile agar plugs were used for a non-inoculated control leaf. All six leaves were placed on a wet filter paper in a closed container at 25°C. All inoculated leaves had necrotic tissues around the wounds, the symptoms progressed from spots to the entire leaves after two days . The control leaves remained asymptomatic. In the whole-plant assay, a D. chinensis  plant (approx. 0.3 m in height) was inoculated with 5 mL of zoospore suspension that was mixed into the potting soil(500g). Three plants were inoculated and control plants were treated with sterile distilled water. After two weeks all three inoculated plants in three repeats of the assay had root and crown rot and foliage blight, whereas all control plants remained asymptomatic. P. nicotianae was reisolated from all inoculated plants. This is the first report of P. nicotianae causing root rot and foliage blight on D. chinensis in China. Considering the importance of D. chinensis to both ornamental nursery and landscaping industries in China, diseased plants at the landscape sites were removed to prevent the spread of P. nicotianae to production sites and other landscape locations.

scholarly journals First Report of a Phytopythium litorale Species Causing Crown and Root Rot on Rhododendron pulchrum in China

Plant Disease ◽  
2021 ◽  
Author(s):  
Yaxing Li ◽  
Yangfan Feng ◽  
Cuiping Wu ◽  
Junxin Xue ◽  
Binbin Jiao ◽  
...  
Keyword(s):  
Root Rot ◽  
Morphological Characters ◽  
Morphological Features ◽  
Crown Rot ◽  
Sterile Water ◽  
First Report ◽  
Inoculation Method ◽  
Platanus Orientalis ◽  
Crown And Root Rot ◽  
Root Tissues

During a survey of pathogenic oomycetes in Nanjing, China from June 2019 to October 2020, at least ten adjacent Rhododendron pulchrum plants at a Jiangjun Mountain scenic spot showed symptoms of blight, and crown and root discoloration . Symptomatic root tissues collected from three 6-year-old plants were rinsed with water, cut into 10-mm pieces, surface sterilized with 70% ethanol for 1 min, and plated onto 10% clarified V8 PARP agar (cV8A-PARP) containing pimaricin (20 mg/liter), ampicillin (125 mg/liter), rifampicin (10 mg/liter), and pentachloronitrobenzene (20 mg/liter). Four Pythium-like isolates were recovered after three days of incubation at 26°C, and purified using hyphal-tipping. Ten agar plugs (2×2 mm2) of each isolate were grown in 10 mL of 10% clarified V8 juice (cV8) in a 10 cm plate at 26°C for 3 days to produce mycelial mats, and then the cV8 was replaced with sterile water. To stimulate sporangial production, three to five drops of soil extract solution were added to each plate. Sporangia were terminal, ovoid to globose, and the size is 24 to 45.6 (mean 34.7) (n=10.8) in length x 23.6 to 36.0 (mean 29.8) (n=6.2) in width. Gametangia were not observed in cV8A or liquid media after 30 days. For colony morphology, the isolates were sub-cultured onto three solid microbial media (cV8A-PARP, potato dextrose agar, corn meal agar) . All isolates had identical morphological features in the three media. Complete ITS and partial LSU and cox2 gene regions were amplified using primer pairs ITS1/ITS4, NL1/NL4, and FM58/FM66 , respectively. The ITS, LSU, and cox2 sequences of isolate PC-dj1 (GenBank Acc. No. MW205746, MW208002, MW208003) were 100.00% (936/936 nt), 100.00% (772/772 nt), and 99.64% (554/556 nt) identical to those of JX985743, MT042003, and GU133521, respectively. We built a maximum-likelihood tree of Phytopythium species using the concatenated dataset (ITS, LSU, cox2) to observe interspecific differences. Based on the morphological characters and sequences, isolate PC-djl was identified as Phytopythium litorale . As the four isolates (PC-dj1, PC-dj2, PC-dj3 and PC-dj4) tested had identical morphological characters and molecular marker sequences, the pathogenicity of the representative isolate, PC-dj1, was tested using two inoculation methods on ten one-year-old R. pulchrum plants. For the first inoculation method, plants were removed from the pot, and their roots were rinsed with tap water to remove the soil. Each of these plants was placed in a glass flask containing 250 mL of sterile water and 10 blocks (10 x 10 mm2) of mycelial mats harvested from a three-day-old culture of P. litorale, while the other plant was placed in sterile water as a control, and incubated at 26°C. After three days, symptoms including crown rot, root rot and blight was observed on the inoculated plants whereas the control remained asymptomatic. For the second inoculation method, ten plants were dug up to expose the root ball. Ten three-day-old cV8A plugs (5×5 mm2) from a PC-dj1 culture or sterile cV8A plugs were evenly insert into the root ball of a plant before it was planted back into the original pots. Both plants were maintained in a growth chamber set at 26°C with a 12/12 h light/dark cycle and irrigated as needed. After 14 to 21 days, the inoculated plant had symptoms resembling those in the field , while the control plant remained asymptomatic. Each inoculation method was repeated at triplicate and the outcomes were identical. Phytopythium isolates with morphological features and sequences identical to those of PC-dj1 were recovered from rotted crown and root tissues of all inoculated plants. Previously, P. litorale was found causing diseases of apple and Platanus orientalis in Turkey, fruit rot and seedling damping-off of yellow squash in southern Georgia, USA. This is the first report of this species causing crown and root rot on R. pulchrum, an important ornamental plant species in China. Additional surveys are ongoing to determine the distribution of P. litorale in the city of Nanjing.

scholarly journals First Report of Root Rot on Atractylodes macrocephala (Largehead Atractylodes Rhizome) Caused by Ceratobasidium sp. in China

Plant Disease ◽  
2013 ◽  
Vol 97 (1) ◽  
pp. 139-139 ◽  
Author(s):  
J. M. You ◽  
X. M. Lin ◽  
J. Guo ◽  
M. D. Zhang ◽  
C. L. Liao ◽  
...  
Keyword(s):  
Root Rot ◽  
Morphological Characteristics ◽  
White Mold ◽  
Herbaceous Plant ◽  
First Report ◽  
Perennial Herbaceous Plant ◽  
Mercuric Chloride Solution ◽  
Whole Plant ◽  
Atractylodes Macrocephala ◽  
Increasing Temperature

Atractylodes macrocephala is a perennial herbaceous plant (family Asteraceae) native to China. The biennial root, Largehead Atractylodes Rhizome (LAR), is the most commonly used Chinese herbal medicine to prevent early pregnancy loss due to miscarriage. From summer 2010 to spring 2012, symptoms of root rot were observed on LAR in Xianfeng county, Enshi city, Hubei Province, China. White mold on the root of LAR could be observed at an early growth stage in the field and the white mold spread over the entire plant after 10 days, which differs from root rot of LAR caused by Fusarium oxysporum and Rhizoctonia solani, neither of which are characterized as having mycelium spreading over the whole plant (4). Where root rot symptoms were present, rhizome yield was reduced by 15% on average, with up to 40% yield loss in some fields. Under humid conditions in mid-June, the disease in the field spread quickly and the rhizomes of LAR were completely rotted. After rainfall and increasing temperature from 16 to 35°C, white mycelium appeared and plants withered within a few weeks. In April 2011 and 2012, a fungus was consistently recovered from symptomatic rhizome samples after they were surface sterilized with 0.1% mercuric chloride solution and plated onto potato dextrose agar (PDA). Pale gray colonies with short aerial mycelia and brown sclerotia formed on PDA after 7 days incubation at 28°C. Binucleate cells were observed using light microscopy and the characteristics were matched with morphological characteristics of a Ceratobasidium sp (3). Genomic DNA of the culture was extracted, and the rDNA-internal transcribed spacer sequence (GenBank Accession No. JQ926741) showed 99% identity to Ceratobasidium sp (GenBank No. H269825.1). Mycelial plugs of the culture taken from PDA were inoculated onto 40 rhizomes of 1-year-old seedlings and plants were incubated with a 16-h photoperiod at 28°C and 90% relative humidity in an artificial climate chamber where they developed typical disease symptoms after 2 days. Ten rhizomes of 1-year-old seedlings and were treated with PDA plugs only. All seedlings inoculated with the pathogen were withered and the rhizomes were completely covered with gray mycelium 2 days after inoculation, which was similar to the symptoms observed in the field. After 7 days, the symptoms were more severe than those observed in the field, with seedlings rotted completely. The main stalk of all inoculated plants was covered with gray mycelia in 4 days, and the stalk became withered, which was similar to the symptoms observed in the field. No symptoms were observed on control seedlings and plants. Koch's postulates were fulfilled by successful reisolation of Ceratobasidium sp. from diseased seedlings. The pathogenicity tests were carried out twice. Ceratobasidium sp. has been reported to cause root rot of canola in Washington (2). It has also been observed on Rehmannia in China (1). To our knowledge, this is the first report of Ceratobasidium sp. causing root rot on LAR. References: (1) B. B. Chen et al. Chin. J. Chin. Material Medica (In Chinese) 9:1137, 2011. (2) K. L. Schroeder et al. Plant Dis. 96:591, 2012. (3) B. Sneh et al. Page 39 in: Identification of Rhizoctonia Species. The American Phytopathological Society, 1991. (4) S. X. Zang et al. J. Agric. Univ. Hebei (In Chinese) 28:73, 2005.

scholarly journals Pumpkin Fruit Rot in North Carolina Caused by Phytophthora nicotianae

Plant Disease ◽  
2000 ◽  
Vol 84 (8) ◽  
pp. 923-923
Author(s):  
G. J. Holmes
Keyword(s):  
Fungal Growth ◽  
Average Diameter ◽  
Soft Rot ◽  
Selective Medium ◽  
Phytophthora Nicotianae ◽  
Crown Rot ◽  
Fruit Rot ◽  
Unknown Etiology ◽  
Postharvest Diseases ◽  
Phytophthora Spp

In 1999, during an evaluation of pumpkin (Cucurbita pepo) fruit for susceptibility to naturally occurring postharvest diseases, a soft rot of unknown etiology was noted. No fungal growth or sporulation was seen on the fruit surface and no root or crown rot was observed in the field. When fruit were cross-sectioned, masses of white, floccose mycelium covering large sections of the seed cavity were observed. Rot was observed in 21 fruit (6.4% of the total). The fungus was isolated from symptomatic fruit on a modified P10ARPH agar medium, semi-selective for Phytophthora spp. (2). Isolates from eight fruit formed papillate, ovoid sporangia, abundant chlamydospores, and colonies characteristic of P. nicotianae (1). No oospores were produced. Four sound pumpkin fruit (cv. Early Autumn) were inoculated with four isolates (one isolate per fruit). Each isolate was recovered from a different fruit. Pumpkins were surface sterilized at the point of inoculation by wetting with 70% ethanol. Inoculation was done by removing a small amount of mycelium from pure culture using a sterile, wooden toothpick and inserting it 2 cm deep into opposite sides of the mid section of sound fruit (two inoculations per fruit). Control fruit were punctured with sterile toothpicks (once per fruit). First symptoms appeared 4 days after inoculation at room temperature (22 to 24°C). Symptoms consisted of circular, water-soaked areas originating from the point of inoculation. Average diameter (based on four measurements on two fruit) of the water-soaked lesions were 3 cm at first appearance (i.e., 4 days) and 11 cm 10 days after inoculation. No symptoms developed on controls. When symptomatic fruit were cross-sectioned, masses of white, floccose mycelium were noted. Reisolation of this mycelium onto selective medium yielded P. nicotianae, thus fulfilling Koch's postulates. This is the first report of P. nicotianae causing fruit rot of pumpkins. References: (1) D. C. Erwin and O. K. Ribeiro. 1996. Phytophthora Diseases Worldwide. The American Phytopathological Society, St. Paul, MN. (2) H. D. Shew. Phytopathology 77:1090, 1987.

scholarly journals First Report of Collar and Root Rot Caused by Phytophthora nicotianae on Oriental Paperbush (Edgeworthia papyrifera) in Italy

Plant Disease ◽  
2010 ◽  
Vol 94 (7) ◽  
pp. 917-917
Author(s):  
A. Garibaldi ◽  
D. Bertetti ◽  
M. L. Gullino
Keyword(s):  
Root Rot ◽  
Infected Plant ◽  
Its Region ◽  
Soil Extract ◽  
Phytophthora Nicotianae ◽  
Control Treatment ◽  
Experimental Unit ◽  
Peat Moss ◽  
Late Winter ◽  
First Report

Edgeworthia papyrifera, Oriental paperbush, is a deciduous flowering shrub becoming increasingly popular because of its clove-like perfumed flowers appearing in late winter-early spring. During August of 2009 in a commercial nursery close to Maggiore Lake (Verbano-Cusio-Ossola Province) in northwest Italy, 2-year-old plants of E. papyrifera showed extensive chlorosis and root rot. Twigs wilted and died, dropping leaves in some cases. Most frequently, wilted leaves persisted on stems. At the soil level, dark brown-to-black water-soaked lesions formed and coalesced, girdling the stem. All of the crown and root system was affected. Infected plants died within 14 days of the appearance of symptoms. Disease was widespread and severe, affecting 90 of the 100 plants present. After disinfestation for 1 min in a solution containing 1% NaOCl, rotting root and collar pieces of E. papyrifera consistently produced a Phytophthora-like organism when plated on a medium selective for oomycetes (3). The pathogen was identified morphologically as Phytophthora nicotianae (= P. parasitica) (2). On V8 agar, coenocytic hyphae, 4 to 8 μm in diameter, formed fluffy, aerial colonies and spherical, intercalary chlamydospores, 21.0 to 36.5 (average 26.7) μm in diameter. Colonies grew well at 35°C and stopped growing at 40°C. Sporangia were produced by growing a pure hyphal-tip culture in a diluted, sterilized soil-extract. Sporangia were borne singly, laterally attached to the sporangiophore, were noncaducous, spherical to ovoid, papillate, and measured 28.6 to 55.2 × 22.4 to 45.1 (average 42.4 × 34.6) μm, length/breadth ratio (1.1:1)-1.2:1-(1.3:1). Papillae measured 3.1 to 7.6 (average 4.6) μm. The internal transcribed spacer (ITS) region of rDNA of a single isolate was amplified with primers ITS4/ITS6 and sequenced. BLAST analysis (1) of the 839-bp segment showed 99% homology with the sequence of P. nicotianae (No. AJ854296). The sequence has been assigned the GenBank No. GU353341. Pathogenicity of isolates Edg.1 and Edg.2 obtained, respectively, from the root and collar of an infected plant was confirmed by inoculating 1-year-old plants of E. papyrifera. Both strains were grown for 15 days on a mixture of 70:30 wheat/hemp kernels, and 4 g/liter of the inoculum was mixed into a substrate containing sphagnum peat moss/pumice/pine bark/clay (50:20:20:10 vol/vol). One plant per 3-liter pot was transplanted into the substrate and constituted the experimental unit. Five plants were used for each test strain and noninoculated control treatment; the trial was repeated once. All plants were kept in a greenhouse at 25 to 28°C. Plants inoculated with Edg.1 and Edg.2 developed chlorosis and root rot 18 and 14 days after the inoculation, respectively, and wilt rapidly followed. Control plants remained symptomless. P. nicotianae was consistently reisolated from inoculated plants. To our knowledge, this is the first report of P. nicotianae on E. papyrifera in Italy as well as worldwide. The current economic importance of the disease is minor due to the limited number of farms that grow this crop in Italy, although spread could increase as the popularity of plantings expand. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997 (2) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phtytopathological Society, St Paul, MN, 1996. (3) H. Masago et al. Phytopathology 67:425, 1977.

scholarly journals First Report of Phytophthora nicotianae Causing Asparagus Spear and Root Rot in China

Plant Disease ◽  
2018 ◽  
Vol 102 (5) ◽  
pp. 1042
Author(s):  
D. L. Li ◽  
J. F. Cao ◽  
C. Huo ◽  
N. A. Rajput ◽  
Z. J. Zhao
Keyword(s):  
Root Rot ◽  
Phytophthora Nicotianae ◽  
First Report

scholarly journals First Report of Rhizoctonia solani Causing a Disease of Sunflower in India

Plant Disease ◽  
2010 ◽  
Vol 94 (4) ◽  
pp. 488-488 ◽  
Author(s):  
K. Srinivasan ◽  
S. Visalakchi
Keyword(s):  
Rhizoctonia Solani ◽  
Root Rot ◽  
Crown Rot ◽  
Pathogenicity Test ◽  
American Phytopathological Society ◽  
First Report ◽  
Leaf Yellowing ◽  
Crown Tissue ◽  
Symptomatic Tissue ◽  
White Mycelium

During the spring of 2009, symptoms including leaf yellowing and wilting, root rot, and death of plants were noted in sunflower (Helianthus annuus L.) crops in Dharmapuri District, Tamilnadu, India. In some fields, approximately 30% of the plants were affected. The disease began when plants were approximately 10 weeks old and occurred on scattered or adjacent plants. The presence of white mycelium was observed on necrotic crowns. Symptomatic tissue was surface disinfested in 70% alcohol for 30 s and 0.5% sodium hypochlorite for 1 min and plated onto potato dextrose agar (PDA) (1). One isolate (coded SV001) had near right-angle branching with basal constriction and adjacent septa and sclerotia typical of Rhizoctonia spp. (2). Cream-colored colonies produced irregular, light brown sclerotia that were 3.0 to 7.3 mm (average 3.8 mm) in diameter. Hyphae were 6.8 to 7.0 μm (average 6.9 μm) wide and multinucleate (8 to 15 nuclei per cell). On the basis of hyphal anastomosis with several known AG testers, the fungus was characterized as Rhizoctonia solani Kühn AG-IV (3). One culture was deposited at the Madras University Botany Laboratory, Center for Advanced Studies in Botany, University of Madras, Chennai, India. In a pathogenicity test, R. solani SV001 was grown on PDA for 5 days at 24°C in the dark. Five-millimeter-diameter disks were placed at the base of sunflower plants (cv. Mordan). Four sunflower plants in each of three pots were inoculated; noninoculated plants served as controls. Plants were placed in a glasshouse maintained at 25 to 27°C. Inoculated plants developed yellow foliage and crown rot and root rot symptoms after 7 to 12 days and died in 17 to 20 days. No symptoms were observed on noninoculated plants. The pathogen was reisolated from fragments of necrotic crown tissue of inoculated plants. To our knowledge, this is the first report of R. solani AG-IV causing a disease of sunflower plants in India. References: (1). R. C. Fenille et al. Plant Pathol. 54:325, 2005. (2). J. R. Parmeter et al. Phytopathology 59:1270, 1969. (3) B. Sneh et al. Identification of Rhizoctonia Species. The American Phytopathological Society, St Paul, MN, 1991.

scholarly journals First Report of Phytophthora nicotianae on Skimmia japonica in Italy

Plant Disease ◽  
2004 ◽  
Vol 88 (8) ◽  
pp. 905-905
Author(s):  
A. Garibaldi ◽  
D. Bertetti ◽  
M. L. Gullino
Keyword(s):  
Root Rot ◽  
Northern Italy ◽  
Ornamental Plant ◽  
Phytophthora Nicotianae ◽  
Plant Production ◽  
Control Treatment ◽  
American Phytopathological Society ◽  
First Report ◽  
Average Temperature ◽  
Lower Stem

Skimmia japonica, an evergreen flowering shrub, is becoming increasingly popular as a potted ornamental plant in northern Italy and represents 5% of acidophilous plant production; cv. Rubella accounts for 99% of production. During the spring of 2003, in many commercial nurseries located in northwestern Italy, plants of S. japonica cv. Rubella showed extensive chlorosis and root rot, and diseased plants eventually wilted and died without dropping leaves. The disease was widespread and severe, and in some nurseries, 40% of plants were affected. A Phytophthora-like organism was isolated consistently from infected lower stem and root pieces of S. japonica that had been disinfested for 1 min in 1% NaOCl and plated on a medium selective for oomycetes (2). The pathogen was identified based on morphological and physiological features as Phytophthora nicotianae (= P. parasitica [1]). The sporangia produced on V8 medium were ± spherical to obpyriform, obturbinate, papillate, and measured 33 to 94 × 25 to 48 μm (average 56.4 × 36.8 μm). Papillae measured 3.5 to 19 μm (average 7.8 μm). Chlamydospores were spherical with a diameter ranging from 26 to 32 μm (average 29.2 μm). Pathogenicity of four isolates obtained from infected plants was confirmed by inoculating 9-month-old plants of S. japonica cv. Rubella grown in 1-liter pots containing a substrate based on sphagnum peatmoss, pine bark, and clay (70-20-10% vol/vol/vol). Inocula, which consisted of 90-mm-diameter V8 agar disks per pot containing mycelium of each isolate, were introduced and mixed into the substrate in all pots before transplanting. One plant was transplanted into each pot and served as a replicate, and noninoculated plants served as controls. Eight replicates were used for each isolate and the control treatment, and the trial was repeated. All plants were kept outside at temperatures ranging from 16 to 38°C (average temperature 27°C). Inoculated plants developed symptoms of chlorosis, root rot, and wilt within 20 days, while control plants remained symptomless. P. nicotianae consistently was isolated from inoculated plants. Previously, P. nicotianae has been reported on S. japonica in Poland (3). To our knowledge, this is the first report of P. nicotianae on S. japonica in Italy. References: (1) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society, St Paul, MN, 1996. (2) H. Masago et al. Phytopathology, 67:425, 1977 (3) G. Szkuta and L. B. Orlikowski. Prog. Plant Prot. 42:808, 2002.

Sign in / Sign up

Export Citation Format

Share Document