First Report of Sclerotinia Blight Caused by Sclerotinia sclerotiorum on Peanut in Georgia

Sclerotinia blight is one of the most economically important diseases of peanut (Arachis hypogaea L.) in Oklahoma and Virginia. Yield losses of 10% are common in these areas; however, losses may exceed 50% in highly infested fields (1). While Sclerotinia minor is considered the primary causal agent, S. sclerotiorum may also incite the disease. Symptoms typically appear late in the season and are favored by cool temperatures and high relative humidity (RH). Initial symptoms include wilting and yellowing of main or lateral branches. Dense mats of white mycelium develop on diseased areas, and small water-soaked lesions are apparent near the soil line. Lesions become bleached and infected tissues have a shredded appearance. Sclerotia are produced on and inside infected plant parts (2). During October 2004, following a period of heavy rainfall and cool temperatures, peanut plants (cv. Tifrunner) with these symptoms were observed in a field near Surrency, GA. The field had been planted to cotton (Gossypium hirsutum L.) for many years and peanut was strip-tilled into a heavy rye (Secale cereale L.) cover. Disease foci were found throughout the field and final incidence was 20%. Stem sections were surface disinfested in 0.5% sodium hypochlorite for 1 min and plated on potato dextrose agar (PDA). Cultures of S. sclerotiorum (2) were recovered after incubation at 20°C for 2 weeks. Pathogenicity tests were conducted by inoculating wounded peanut mainstems with PDA plugs either with or without the fungus. Inoculation sites were wrapped with moistened cheesecloth, and plants were incubated in a dew chamber at 20°C and 95% RH. There were a total of four replications and the experiment was repeated once. Symptoms consistent with those observed in the field appeared after 3 days and lesion lengths were measured after 5 days. Average lesion lengths were 1.4 and 1.6 cm for cvs. Georgia Green and Tifrunner, respectively Controls remained symptomless. Sections of symptomatic tissue were plated on PDA, and S. sclerotiorum was reisolated from 100% of symptomatic tissue. Although S. sclerotiorum is a common pathogen of various winter crops and weeds found in the southeast, to our knowledge, this is a first report of Sclerotinia blight on peanut in the region. No other occurrences of the disease have been reported since the initial discovery; however, potential losses could be incurred if peanuts are planted in infested fields and harvest is delayed. References: (1) H. A. Melouk and P. A. Backman. Management of soilborne fungal pathogens. Pages 75–85 in: Peanut Health Management. H. A. Melouk and F. M. Shokes, eds. The American Phytopathologicial Society, St. Paul, MN, 1995. (2) D. M. Porter and H. A. Melouk. Sclerotinia blight. Pages 34–36 in: Compendium of Peanut Diseases. 2nd ed. N. Kokalis-Burelle et al., eds. The American Phytopathologicial Society, St. Paul, MN, 1997.

Download Full-text

First Report of Bacterial Streak of Fennel (Foeniculum vulgare) in California Caused by Pseudomonas syringae pv. apii

Plant Disease ◽

10.1094/pdis-09-11-0794 ◽

2012 ◽

Vol 96 (2) ◽

pp. 285-285 ◽

Cited By ~ 4

Author(s):

T. M. Jardini ◽

S. T. Koike ◽

C. T. Bull

Keyword(s):

Host Range ◽

Pseudomonas Syringae ◽

Foeniculum Vulgare ◽

Banding Patterns ◽

First Report ◽

Initial Symptoms ◽

Symptomatic Tissue ◽

Dna Fragment ◽

Natural Host Range ◽

Group 1

A previously undescribed disease appeared on commercially grown fennel (Foeniculum vulgare) in Salinas (Monterey County), CA in March 2010. Initial symptoms consisted of small, dark brown-to-black lesions on leaves and stems. As disease progressed, lesions expanded in a linear fashion and eventually spread down the stems and into the bulbs. Once the disease reached the fennel bulbs, the plants were unmarketable. Eighteen, gram-negative, blue-fluorescing bacterial isolates were obtained on sucrose peptone agar from individual plants of two outbreaks from different fields in Salinas. The isolates were dome shaped on sucrose-amended media and produced necrotic lesions when injected into tobacco. Isolates were oxidase negative and did not rot potatoes or hydrolyze arginine. These reactions corresponded to Lelliot's group 1, which includes Pseudomonas syringae (2). The fennel isolates were identical to recently characterized isolates of P. syringae pv. apii from parsley grown in coastal California (1) and similar to the pathotype strain of P. syringae pv. apii according to DNA fragment banding patterns of amplicons generated from repetitive extragenic palindromic sequence (rep)-PCR using the BOXA1R primer. The isolates were distinct from the pathotype strain P. syringae pv. coriandricola. Like P. syringae pv. apii, the fennel isolates did not nucleate ice but did hydrolyze gelatine. Six isolates were tested for pathogenicity in each of two independent experiments with a total of six replications per isolate. Healthy, potted fennel plant stems of a proprietary cultivar were pierced once with insect display pins that had been dipped into bacterial colonies grown for 48 h on nutrient agar. Control stems were inoculated with sterile pins. Plants were incubated for 48 h at 100% relative humidity and then held in a greenhouse. After 4 to 6 days, inoculated fennel plants developed symptoms similar to those originally observed in the field. Bacteria isolated from surface-disinfested symptomatic tissue were fluorescent and identical to strains used to inoculate plants as evaluated by rep-PCR, thus fulfilling Koch's postulates. Control plants remained symptomless. To our knowledge, this is the first report of this pathogen causing a disease on fennel; the disease has been named bacterial streak. The disease occurred in three fields in 2010 and incidence was <1% in each case. Similar symptoms were also observed on fennel in the 2011 season in at least two fields. Previously, the host range of P. syringae pv. apii was reported to be restricted to celery. This research expands the natural host range of P. syringae pv. apii; thus, care should be taken in choosing Apiaceae crops for plantings subsequent to the occurrence of this pathogen. References: (1) C. T. Bull et al. Phytopathology 101:847, 2011. (2) R. A. Lelliott. J. Appl. Bacteriol. 29:470, 1966.

Download Full-text

First Report of Leaf Blotch Caused by Septoria phalaridis on Phalaris paradoxa

Plant Disease ◽

10.1094/pdis-94-3-0375b ◽

2010 ◽

Vol 94 (3) ◽

pp. 375-375

Author(s):

Sh. Seifbarghi ◽

M. Razavi ◽

M. Abbasi ◽

R. Zare

Keyword(s):

Infected Plant ◽

Its Region ◽

Morphological Characters ◽

Fungal Species ◽

Leaf Blotch ◽

First Report ◽

Initial Symptoms ◽

Csiro Publishing ◽

Voucher Specimens ◽

Severity Of The Disease

Phalaris paradoxa (hood canarygrass) is one of the most abundant weeds in wheat fields of Iran. In a survey conducted from 2005 to 2007 in Ilam (Dehloran City) and Golestan (Gorgan City) provinces, leaf blotch symptoms were prevalent on P. paradoxa. Initial symptoms were pale brown and necrotic lesions that were 3 to 4 mm long on the leaves. Severity of the disease on the lower leaves was higher than on the upper leaves. Pycnidia were observed on the adaxial surface of infected leaves, scattered or sometimes in clusters, dark brown, globose, and 70 to 90 μm in diameter, with the ostiole approximately 10 μm in diameter. Conidia were filiform, hyaline, 0 to 3 septate (mostly 1 septate), and 17 to 40 × 1.5 to 2.0 μm. Conidiogenesis type was holoblastic. On the basis of the above morphological characters, this species was identified as Septoria phalaridis Cocc. & Morini (2,3). Sequencing the internal transcribed spacer (ITS) region of the fungus (GenBank Accession No. GU123926) showed 98% homology to Mycosphaerella graminicola strain 687 and 97% to S. passerinii strain ATCC26515 (GenBank Accession Nos. AB435068.1 and AF181696.1). To confirm pathogenicity of the fungus, 25 P. paradoxa seedlings were inoculated at the three-leaf stage with 20 ml of 1 × 107 spores/ml suspension with a hand sprayer. Plants were covered with a clear polyethylene bag to increase humidity and prevent cross contamination. After 72 h, bags were removed and plants were kept in a greenhouse at 21 ± 2/16 ± 2°C (day/night) and a 16-h photoperiod. Control plants received sterilized distilled water only. Leaves of each plant were visually inspected every day and the appearance of disease symptoms was recorded. After 1 month, all inoculated leaves showed symptoms and signs of the disease such as chlorosis, necrosis, and pycnidia, whereas control plants showed no symptoms or signs of disease. The infected plant tissues were examined with a microscope, the pycnidia and pycnidiospores were measured, and S. phalaridis was reisolated from leaf lesions. The first description of S. phalaridis was on P. brachystachys (1); however, to our knowledge, this is the first report of this pathogen on P. paradoxa. In addition, this is a new fungal species for the mycobiota of Iran. Two voucher specimens (IRAN 14078 F and IRAN 14218 F) were deposited in the Fungus Collection of the Ministry of Jihad-e Agriculture, Tehran, Iran. References: (1) G. Cocconi and F. Morini. Mem. R. Accad. Sci. Ist. Bologna, Cl. Sci. Fis. Ser. 4, 6:371, 1884. (2) M. J. Priest. Fungi of Australia, Septoria. ABRS, Canberra. CSIRO Publishing, Melbourne, 2006. (3) D. N. Teterevnikova-Babayan. Fungi of the Genus Septoria in the USSR. Akademiya Nauk Armyanskoi SSR, Yerevan, 1987.

Download Full-text

First Report of Bacterial Blight of Strelitzia augusta Caused by Pseudomonas syringae pv. lachrymans

Plant Disease ◽

10.1094/pd-89-1010a ◽

2005 ◽

Vol 89 (9) ◽

pp. 1010-1010 ◽

Cited By ~ 4

Author(s):

G. Polizzi ◽

I. Castello ◽

G. Parlavecchio ◽

G. Cirvilleri

Keyword(s):

Pseudomonas Syringae ◽

Cross Sections ◽

Plate Count ◽

Bacterial Suspension ◽

First Report ◽

Small Water ◽

Plate Count Agar ◽

Leaf Spots ◽

Initial Symptoms ◽

Pathogenicity Tests

White bird of paradise tree (Strelitzia augusta Thunb.), originally from South Africa, is a tender perennial cultivated as an ornamental plant and is used in gardens in Italy. During February of 2004, a new blight disease was noticed on potted S. augusta at different ages (6 months to 4 years) in several commercial nurseries of eastern Sicily. Field inspections revealed disease incidences as high as 40%. Initial symptoms were small, water-soaked leaf spots that expanded throughout the veins in dark brown streaks. Stem cross sections revealed browning of the vascular tissues, which might involve the entire stem. In some cases, the necrosis extended to the apical bud, causing death of the plant. Thirty explants from infected tissues were washed in sterile water and plated on plate count agar (PCA) from which two types of bacterial colonies were consistently isolated. Pathogenicity tests were performed on S. augusta plants. Twenty-four plants were inoculated (12 per bacterial isolate) using two different procedures: spray with a bacterial suspension (106 CFU/ml) and wounding with an infected needle on the midribs. The same number of noninoculated plants was used as controls. All plants were maintained at 24 to 26°C with 95 to 100% relative humidity until symptoms occurred 4 days later. Just one of the two tested bacterial types was pathogenic. The symptoms were similar to those previously observed in the field. No symptoms were observed in the plants spray inoculated with the bacterial suspension, proving that the bacteria were unable to infect in the absence of a wound. The controls showed no symptoms. Koch's postulates were fulfilled by the reisolation of the infective strain which was sent to the CBS (Centraalbu-reau voor Schimmelcultures) and identified as Pseudomonas syringae pv. Lachrymans/pisi using the Biolog MicroLog3 4.01C program (Biolog Inc., Hayward, CA). Further pathogenicity tests have been carried out on zucchini and pea pods to characterize the pathovar using 48SR1 of P. syringae pv. syringae and B4 of P. syringae pv. pisi as reference strains. Necrotic, sunken, water-soaked spots surrounded by a chlorotic halo, reported in the literature as typical symptoms of P. syringae pv. lachry-mans (Smith & Bryan) Young, Dye & Wilkie (1), were observed on zucchini when inoculated with our strain. Our P. syringae strain did not cause the typical symptoms of P. syringae pv. pisi on inoculated pea pods. The results of the pathogenicity tests and the inability of the P. syringae strain isolated from S. augusta to utilize homoserine, used to discriminate pv. pisi from other pathovars of P. syringae, allowed us to identify the strain as P. syringae pv. lachrymans. Low temperature damage and late transplant may have promoted the spread of the disease in the nurseries. Under these conditions, the economic importance of this disease for the crop can be considered high. To our knowledge, this is first report of P. syringae pv. lachrymans on S. augusta. Reference: (1) K. Pohronezny et al. Plant Dis. Rep. 62:306, 1978.

Download Full-text

First Report of Aerial Blight of Peanut Caused by Rhizoctonia solani AG1-IA in Arkansas

Plant Disease ◽

10.1094/pdis-04-13-0414-pdn ◽

2013 ◽

Vol 97 (12) ◽

pp. 1658-1658 ◽

Cited By ~ 1

Author(s):

T. R. Faske ◽

T. N. Spurlock

Keyword(s):

Rhizoctonia Solani ◽

Fungal Pathogens ◽

Health Management ◽

Disease Incidence ◽

Its Region ◽

First Report ◽

Circular Pattern ◽

Rdna Its ◽

Randolph County ◽

Humidity Chamber

In early September 2012, symptoms similar to aerial blight were observed on runner peanut (cv. Georgia 09B) in a commercial field in Randolph County, Arkansas (3). Leaves within the canopy closest to the soil had water-soaked, gray to green lesions or tan to brown lesions. Localized areas of matted leaves with mycelium occurred on stems and hyphae extended along stems and newly affected leaves. Dark brown spherical sclerotia (1.5 to 4 mm diam.) were produced on the surface of symptomatic peanut tissue (3). Aerial blight symptoms were observed in two peanut fields (~4 to 6 ha) that were furrow irrigated. Symptomatic plants were localized in a single circular pattern (~20 × 25 m) near the lower end of each field with the final disease incidence of less than 5%. Isolations from surface-disinfected leaves on potato dextrose agar consistently yielded light brown to brown colonies with sclerotia typical of Rhizoctonia solani AG1-IA. The fungus was confirmed to be R. solani AG1 by anastomosis reaction (2) with known cultures of AG1-IA isolated from soybean and rice in Arkansas. Sequencing of the rDNA ITS region 5.8s with primers ITS1 and ITS4 (1) supported the identification of the R. solani isolates as AG1-IA. The BLAST search revealed that the sequence had a 96 to 97% maximum sequence identity to several R. solani AG1-IA isolates collected from rice sheaths in China and Arkansas. Eight-week-old peanut plants (cv. Georgia 09B) growing in pots were sprayed until runoff (2 ml/plant) with a solution containing approximately 1 × 105 hyphal fragments/ml. Five inoculated plants were placed in a humidity chamber within a greenhouse where temperatures ranged from 28 to 33°C. After 14 days, water soaked, gray to green or light brown lesions developed on all inoculated plants along with hyphal strands along inoculated sections of the peanut with dark brown sclerotia. None of the plants inoculated with sterile water expressed symptoms. Rhizoctonia solani was consistently reisolated from symptomatic tissue plated on PDA. Inoculations were repeated on peanut cv. Flavor Runner 458, Florida 07, FloRun 107, and Red River Runner with similar results. Although R. solani AG1-IA is a common pathogen on rice and soybean, causing sheath blight and aerial blight, respectively, to our knowledge this is the first report of aerial blight of peanut in the region. Currently, there is a renewed interest in peanut production in the state. Production practices include furrow irrigation, which can distribute floating sclerotia to peanut vines and the rotation practiced with soybean and, less frequently, rice, could potentially increase inoculum for the subsequent crop. Thus, this may be a significant disease problem in the region or Mid-South where peanut is planted after rice or soybean and furrow irrigated. References: (1) S. Kuninaga et al. Curr. Genet. 32:237, 1997. (2) G. C. MacNish et al. Phytopathology 83:922, 1993. (3) H. A. Melouk and P. A. Backman. Management of soilborne fungal pathogens. Pages 75-85 in: Peanut Health Management. H. A. Melouk and F. M. Stokes, eds. The American Phytopathological Society, St. Paul, MN, 1995.

Download Full-text

Fungal pathogens associated with wilting of Neolitsea cassia trees

International Journal of Forestry, Ecology and Environment ◽

10.18801/ijfee.040221.19 ◽

2021 ◽

Vol 04 (02) ◽

pp. 172-176

Author(s):

A. L. M. Zuhry ◽

R. G. A. S. Rajapaksha ◽

J. Kahawatta ◽

S. Kohombange

Keyword(s):

Sri Lanka ◽

Tree Species ◽

Fungal Pathogens ◽

Infected Plant ◽

Pathogenic Fungi ◽

Fungal Species ◽

Wilt Disease ◽

Thiophanate Methyl ◽

First Report ◽

Collar Region

Neolitsea cassia, a tree species, belongs to family Lauraceae, is endemic to Sri Lanka. Few planted trees of Neolitsea cassia were severely affected by wilt disease. Two fungal pathogens were consistently isolated from collar region and roots of symptomatic trees. These two fungal species were identified as Colletotrichum and Pestalotiopsis by microscopic observations of conidia and culture characters of isolates on PDA. This is the first report of Colletotrichum and Pestalotiopsis species causing tree wilting of Neolitsea cassia in Sri Lanka. Application of 25 l of fungicide, Thiram + Thiophanate Methyl, 50+30% WP (Homai) solution (1g/l) around the base of each infected plant as a soil drenching was effectively controlled wilting of Neolitsea cassia caused by both pathogenic fungi.

Download Full-text

First Report of Wet Rot of Withania somnifera Caused by Choanephora cucurbitarum in India

Plant Disease ◽

10.1094/pdis-09-11-0801 ◽

2012 ◽

Vol 96 (2) ◽

pp. 293-293 ◽

Cited By ~ 8

Author(s):

A. Saroj ◽

A. Kumar ◽

N. Qamar ◽

M. Alam ◽

H. N. Singh ◽

...

Keyword(s):

Withania Somnifera ◽

Infected Plant ◽

Morphological Characteristics ◽

Universal Primers ◽

28S Rrna ◽

Plant Parts ◽

Northern India ◽

Initial Symptoms ◽

Humidity Chamber ◽

Choanephora Cucurbitarum

Withania somnifera (Ashwagandha) is native to India and commercially cultivated for the production of root withanolides that have anticarcinogenic properties. A disease appeared on plantings of W. somnifera during the 2010 monsoon at the CIMAP and in adjoining areas of northern India. Symptoms first appeared as water-soaked lesions on leaves and stems that progressed to a wet rot. Mature lesions harbored black fructifications of the suspect pathogen. Pathogen isolations were done by placing pieces of infected tissues on potato dextrose agar. A fungus tentatively identified as a Choanephora sp. that produced white aerial mycelia that later turned pale yellow was consistently isolated from infected plant parts. Mycelia were hyaline and nonseptate. Sporangiophores bearing sporangiola were erect, hyaline, unbranched, apically dilated to form a clavate vesicle from which arose dichotomously branched distally clavate secondary vesicles. Sporangiola were indehiscent, ellipsoid, brown to dark brown with distinct longitudinal striations, and measured 12 to 20 × 6 to 12 μm. Sporangia were multispored, spherical, initially white to yellow and pale brown to dark brown at maturity, and measured 40 to 160 μm. Sporangiospores from sporangia were ellipsoid to broadly ellipsoid, brown to dark brown, indistinctly striate with fine hyaline polar appendages, and measured 16 to 20 × 8 to 12 μm. On the basis of the cultural as well as morphological characteristics and description in the monograph by Kirk (2), the fungus was identified as a Choanephora sp. The identification was also confirmed by IMTECH, Chandigarh, India with Accession No. MTCC-10731. The species was later characterized as Choanephora cucurbitarum (Berk. & Ravenel) Thaxt (GenBank Accession No. AB470642) by using universal primers ITS-1 and ITS-4. Its sequence comprising of 18S rRNA partial, complete ITS 1, 5.8S rRNA, ITS 2, and 28S rRNA partial was submitted to NCBI GenBank with Accession No. JN639861. Pathogenicity of the fungus was established on five healthy plants by artificial inoculation with spray of an aqueous spore suspension containing 106 spores/ml. Plants sprayed with sterile distilled water were used as controls. Both inoculated and control plants were kept in a humidity chamber (96%) for 3 days and thereafter placed in the glasshouse at 28 ± 2°C. Initial symptoms developed in 2 to 3 days while typical disease symptoms appeared on all the inoculated plants after 7 to 10 days. Control plants were free from infection. The reisolation from artificially infected plants again yielded a Choanephora sp., thus fulfilling Koch's postulates. W. somnifera cultivation has been affected by root rot and wilt caused by Fusarium solani and leaf spot caused by Alternaria dianthicola (3). The occurrence of a Choanephora sp. was reported on periwinkle, petunia (1), and Boerhavia diffusa (4). However, to our knowledge, incidence of this pathogen on W. somnifera has not been reported so far. Thus, wet rot of W. somnifera caused by C. cucurbitarum is a new report from India and worldwide. References: (1) G. E. Holcomb. Plant Dis. 87:751, 2003. (2) P. M. Kirk. Mycol. Pap. 152:1, 1984. (3) C. K. Maiti et al. Plant Dis. 91:467, 2007. (4) N. Singh et al. New Dis. Rep. 23:29, 2011.

Download Full-text

First Report of Sclerotinia Blight Caused by Sclerotinia sclerotiorum on Peanut in Arkansas

Plant Health Progress ◽

10.1094/php-br-16-0056 ◽

2017 ◽

Vol 18 (1) ◽

pp. 7-8

Author(s):

T. R. Faske ◽

G. Drennan ◽

K. Hurd

Keyword(s):

Sclerotinia Sclerotiorum ◽

Negative Impact ◽

The State ◽

First Report ◽

Sclerotinia Blight ◽

Peanut Production

This is the first report of Sclerotinia blight caused by Sclerotinia sclerotiorum on peanut occurring in Arkansas. There has been renewed interest in commercial peanut production in Arkansas, and this pathogen could have a negative impact on peanut in the state.

Download Full-text

First Report of Pythium Root Rot of Rau Ram (Polygonum odoratum)

Plant Disease ◽

10.1094/pd-89-0340a ◽

2005 ◽

Vol 89 (3) ◽

pp. 340-340

Author(s):

E. N. Rosskopf ◽

C. B. Yandoc ◽

B. Stange ◽

E. M. Lamb ◽

D. J. Mitchell

Keyword(s):

Root Rot ◽

Vascular System ◽

Pond Water ◽

Centraalbureau Voor ◽

First Report ◽

Pathogenicity Tests ◽

Symptomatic Tissue ◽

Pythium Helicoides ◽

Production House ◽

Test Plants

Polygonum odoratum (= Persicaria odorata), known as rau ram or sang hum, is native to southeastern Asia and is a common herb in Vietnamese cuisine (1). It has been studied most extensively for its aromatic compound content (2). In Florida, rau ram commonly is grown hydroponically in greenhouses using large, cement beds with recirculated water. The plants form dense mats from which new growth is trimmed for market. During January of 2002, a severe dieback was observed in one production house in Saint Lucie County, FL. Plants with less severe symptoms were yellowed and stunted. Roots of symptomatic plants were largely decayed with root symptoms beginning as a tip necrosis. The cortex of severely affected roots slipped off easily, leaving a stringy vascular system. Plating of symptomatic tissue from 20 randomly selected plant samples was performed with multiple general and selective media including potato dextrose agar, corn meal agar with pimaricin, ampicillin, rifampicin, and pentachloronitrobenzene (PARP) (3). All colonies produced were identified as Pythium helicoides Drechsler on the basis of sporangial, oogonial, and antheridial characteristics (4). Isolates had proliferous, obovoid, papillate sporangia, and were homothallic with smooth-walled oogonia and thick-walled, aplerotic oospores. Multiple antheridial attachments per oogonium were common with the antheridium attached along its entire length. Pathogenicity tests were conducted using P. odoratum plants grown from commercial transplants. Two tests were performed. Each test was conducted using eight inoculated and eight control plants. In the first test, plants were maintained in 10-cm pots immersed in sterilized pond water for the duration of the test. Plants were inoculated with five 7- × 70-mm sections of freshly growing mycelial culture per plant using 10-day-old cultures of Pythium helicoides grown on water agar. Chlorosis was observed at approximately 2 months after inoculation. Root necrosis was observed in inoculated plants approximately 5 months after inoculation. This test was performed in the greenhouse with temperatures ranging from 20 to 30°C. The second test was performed in growth chambers at 35 to 40°C. Plants were maintained in 10-cm pots immersed in Hoagland's solution and were inoculated with four 6-mm plugs per plant. Symptoms were observed on inoculated plants at this temperature within 1 week of inoculation. No chlorosis or root decay was observed in noninoculated, immersed plants. The pathogen was reisolated from inoculated, symptomatic tissue. To our knowledge, this is the first report of root rot of P. odoratum caused by Pythium helicoides. References: (1) R. E. Bond. Herbarist 55:34, 1989. (2) N. X. Dung et al. J. Essent. Oil Res. 7:339, 1995. (3) M. E. Kannwischer and D. J. Mitchell. Phytopathology 68:1760, 1978. (4) A. J. van der Plaats-Niterink. Monograph of the Genus Pythium. Vol. 21, Studies in Mycology. Centraalbureau voor Schimmelcutltures, Baarn, The Netherlands, 1981.

Download Full-text

First Report of Sclerotinia sclerotiorum on Campanula carpatica and Schizanthus × wisetonensis in Italy

Plant Disease ◽

10.1094/pdis.2002.86.1.71a ◽

2002 ◽

Vol 86 (1) ◽

pp. 71-71

Author(s):

A. Garibaldi ◽

A. Minuto ◽

M. L. Gullino

Keyword(s):

United States ◽

Sclerotinia Sclerotiorum ◽

Ornamental Plants ◽

Soil Surface ◽

The United States ◽

First Report ◽

Potted Plants ◽

Initial Symptoms ◽

Stem Necrosis ◽

Campanula Carpatica

The production of potted ornamental plants is very important in the Albenga Region of northern Italy, where plants are grown for export to central and northern Europe. During fall 2000 and spring 2001, sudden wilt of tussock bellflower (Campanula carpatica Jacq.) and butterfly flower (Schizanthus × wisetonensis Hort.) was observed on potted plants in a commercial greenhouse. Initial symptoms included stem necrosis at the soil line and yellowing and tan discoloration of the lower leaves. As stem necrosis progressed, infected plants growing in a peat, bark compost, and clay mixture (70-20-10) wilted and died. Necrotic tissues were covered with whitish mycelia that produced dark, spherical (2 to 6 mm diameter) sclerotia. Sclerotinia sclerotiorum was consistently recovered from symptomatic stem pieces of both plants disinfested for 1 min in 1% NaOCl and plated on potato dextrose agar amended with streptomycin sulphate at 100 ppm. Pathogenicity of three isolates obtained from each crop was confirmed by inoculating 45- to 60-day-old C. carpatica and Schizanthus × wisetonensis plants grown in containers (14 cm diameter). Inoculum that consisted of wheat kernels infested with mycelia and sclerotia of each isolate was placed on the soil surface around the base of previously artificially wounded or nonwounded plants. Noninoculated plants served as controls. All plants were maintained outdoors where temperatures ranged between 8 and 15°C. Inoculated plants developed symptoms of leaf yellowing, followed by wilt, within 7 to 10 days, while control plants remained symptomless. White mycelia and sclerotia developed on infected tissues and S. sclerotiorum was reisolated from inoculated plants. To our knowledge, this is the first report of stem blight of C. carpatica and Schizanthus × wisetonensis caused by S. sclerotiorum in Italy. The disease was previously observed on C. carpatica in Great Britain (2) and on Schizanthus sp. in the United States (1). References: (1) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St. Paul, MN, 1989. (2) J. Rees. Welsh J. Agric. 1:188, 1925.

Download Full-text

First Report of Anthracnose of Papaya (Carica papaya L.) Caused by Colletotrichum siamense in China

Plant Disease ◽

10.1094/pdis-10-20-2154-pdn ◽

2021 ◽

Author(s):

Yujie Zhang ◽

Wenxiu Sun ◽

Ping Ning ◽

Tangxun Guo ◽

SuiPing Huang ◽

...

Keyword(s):

Carica Papaya ◽

Disease Incidence ◽

Aerial Mycelium ◽

Postharvest Disease ◽

Distilled Water ◽

First Report ◽

Surface Samples ◽

Initial Symptoms ◽

Colletotrichum Siamense ◽

Pathogenicity Tests

Papaya (Carica papaya L.) is a rosaceous plant widely grown in China, which is economically important. Anthracnose caused by Colletotrichum sp. is an important postharvest disease, which severely affects the quality of papaya fruits (Liu et al., 2019). During April 2020, some mature papaya fruits with typical anthracnose symptoms were observed in Fusui, Nanning, Guangxi, China with an average of 30% disease incidence (DI) and over 60% DI in some orchards. Initial symptoms of these papayas appeared as watery lesions, which turned dark brown, sunken, with a conidial mass appearing on the lesions under humid and warm conditions. The disease severity varied among fruits, with some showing tiny light brown spots, and some ripe fruits presenting brownish, rounded, necrotic and depressed lesions over part of their surface. Samples from two papaya plantations (107.54°E, 22.38°N) were collected, and brought to the laboratory. Symptomatic diseased tissues were cut into 5 × 5 mm pieces, surface sterilized with 2% (v/v) sodium hypochlorite for 1 minute, and rinsed three times with sterilized water. The pieces were then placed on potato dextrose agar (PDA). After incubation at 25°C in the dark for one week, colonies with uniform morphology were obtained. The aerial mycelium on PDA was white on top side, and concentric rings of salmon acervuli on the underside. A gelatinous layer of spores was observed on part of PDA plates after 7 days at 28°C. The conidia were elliptical, aseptate and hyaline (Zhang et al., 2020). The length and width of 60 conidia were measured for each of the two representative isolates, MG2-1 and MG3-1, and these averaged 13.10 × 5.11 μm and 14.45 × 5.95 μm. DNA was extracted from mycelia of these two isolates with the DNA secure Plant Kit (TIANGEN, Biotech, China). The internal transcribed spacer (ITS), partial actin (ACT), calmodulin (CAL), chitin synthase (CHS), β-tubulin 2 (TUB2) and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) regions were amplified by PCR and sequenced. The sequences were deposited into GenBank with accessions MT904003, MT904004, and MT898650 to MT898659. BLASTN analyses against the GenBank database showed that they all had over 99% identity to the type strain of Colletotrichum siamense isolate ICMP 18642 (GenBank accession numbers JX010278, GQ856775, JX009709, GQ856730, JX010410, JX010019) (Weir et al., 2012). A phylogenetic tree based on the combined ITS, ACT, CAL, CHS, TUB2 and GAPDH sequences using the Neighbor-joining algorithm also showed that the isolates were C. siamense. Pathogenicity tests were conducted on 24 mature, healthy and surface-sterilized papaya fruits. On 12 papaya fruits, three well separated wounded sites were made for inoculation, and for each wounded site, six adjacent pinhole wounds were made in a 5-mm-diameter circular area using a sterilized needle. A 10 µl aliquot of 1 × 106 conidia/ml suspension of each of the isolates (MG2-1 and MG3-1) was inoculated into each wound. For each isolate, there were six replicate fruits. The control fruits were inoculated with sterile distilled water. The same inoculation was applied to 12 non-wound papaya fruits. Fruits were then placed in boxes which were first washed with 75% alcohol and lined with autoclaved filter paper moistened with sterilized distilled water to maintain high humidity. The boxes were then sealed and incubated at 28°C. After 10 days, all the inoculated fruits showed symptoms, while the fruits that were mock inoculated were without symptoms. Koch's postulates were fulfilled by re-isolation of C. siamense from diseased fruits. To our knowledge, this is the first report of C. siamense causing anthracnose of papaya in China. This finding will enable better control of anthracnose disease caused by C. siamense on papaya.

Download Full-text