First Report of Postharvest Fruit Rot in Avocado (Persea americana) Caused by Lasiodiplodia theobromae in Italy

Avocado (Persea americana Mill.) is grown in some areas of southern Italy. In spring 2011, a previously unknown rot was observed on fruit that was marketed in Torino (northern Italy). The decayed area started from the stalk, appeared irregular and soft, and was surrounded by a dark brown margin. The internal decayed area appeared rotten, brown, and surrounded by bleached tissue. Fragments (approximately 3 mm) were taken from the margin of the internal diseased tissues, cultured on potato dextrose agar (PDA), and incubated at temperatures between 21 and 25°C under alternating conditions of light and dark. Colonies of the fungus initially appeared whitish, later turning mouse gray to black. Mature mycelium was septate and produced a dark pigment. The fungus, grown on oat agar (2) and incubated at temperatures between 21 and 25°C under alternating light and darkness, produced grayish colonies with a fluffy aerial mycelium that became dark with age and produced black pigments. After 18 days of incubation, such colonies produced pycnidia aggregated into stromatic masses, emerging from decayed tissues, and up to 3 to 4 mm in diameter. Conidia produced in the pycnidia were initially unicellular, hyaline, granulose, ovoid to ellipsoidal, and measured 20.8 to 26.9 × 12.5 to 16.1 (average 24.4 × 13.5) μm. After 7 days, mature conidia became darker, uniseptate, and longitudinally striate. Paraphyses produced within the tissues of pycnidia were hyaline, cylindrical, nonseptate, and up to 63 μm long. Morphological characteristics of mycelia, pycnidia, and conidia observed with a light microscope permitted identify of the fungus as Lasiodiplodia theobromae (3). The internal transcribed spacer (ITS) region of rDNA was amplified using the primers ITS1/ITS4 and sequenced. BLAST analysis (1) of the 488-bp segment showed a 100% similarity with the corresponding sequence (GenBank Accession No. GQ502453) of L. theobromae Pat. Griffon & Maubl. The nucleotide sequence of the strain used for pathogenicity tests was submitted to GenBank (Accession No. JN849098). Pathogenicity tests were performed by inoculating 10 avocado fruits after surface disinfesting in 1% sodium hypochlorite and then wounding. Mycelial disks (8 mm in diameter) obtained from PDA cultures of one strain were placed on wounds. Ten control fruits were inoculated with plain PDA. Fruits were incubated at 15 ± 1°C. The first symptoms developed 4 days after the artificial inoculation. After 7 days, the rot was evident and L. theobromae was consistently reisolated. Noninoculated fruit remained healthy. The pathogenicity test was performed twice. To our knowledge, this is the first report of the presence of L. theobromae causing postharvest fruit rot on avocado in Italy, as well as in Europe. The occurrence of postharvest fruit rot on avocado caused by L. theobromae was described in many avocado-producing areas such as the United States (4), South Africa, and Israel. In Italy, the economic importance of avocado cultivation is currently limited. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2). P. Narayanasamy. Microbial Plant Pathogens. Detection and Disease Diagnosis: Fungal Pathogens. Springer, Dordrecht, 2011. (3) E. Punithalingam. Sheet 519. CMI Description of Fungi and bacteria, 1976. (4) H. E. Stevens and R. B. Piper. Circular No. 582, USDA, 1941.

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First Report of Fruit Rot in Pear Caused by Botryosphaeria dothidea in Italy

Plant Disease ◽

10.1094/pdis-02-12-0130-pdn ◽

2012 ◽

Vol 96 (6) ◽

pp. 910-910 ◽

Cited By ~ 9

Author(s):

A. Garibaldi ◽

D. Bertetti ◽

A. Poli ◽

M. L. Gullino

Keyword(s):

Morphological Characteristics ◽

Its Region ◽

The United States ◽

Fruit Rot ◽

Pathogenicity Test ◽

Botryosphaeria Dothidea ◽

First Report ◽

Irregular Margin ◽

Pyrus Communis L ◽

Pathogenicity Tests

Pear (Pyrus communis L.) is widely grown in Italy, the leading producer in Europe. In summer 2011, a previously unknown rot was observed on fruit of an old cultivar, Spadoncina, in a garden in Torino Province (northern Italy). The decayed area of the fruit was soft, dark brown, slightly sunken, circular, and surrounded by an irregular margin. The internal decayed area appeared rotten and brown and rotted fruit eventually fell. To isolate the causal agent, fruits were soaked in 1% NaOCl for 30 s and fragments (approximately 2 mm) were taken from the margin of the internal diseased tissues, cultured on potato dextrose agar (PDA), and incubated at temperatures between 20 and 28°C under alternating light and darkness. Colonies of the fungus initially appeared whitish, then turned dark gray. After about 30 days of growth, unicellular elliptical hyaline conidia were produced in pycnidia. Conidia measured 16 to 24 × 5 to 7 (average 20.1 × 5.7) μm (n = 50). The morphological characteristics are similar to those of the fungus Botryosphaeria dothidea (Moug.: Fr.) Ces. & De Not. (4). The internal transcribed spacer (ITS) region of rDNA was amplified with the primers ITS1/ITS4 and sequenced. BLAST analysis (1) of the 473-bp segment showed a 100% similarity with the sequence of the epitype of B. dothidea AY236949. The nucleotide sequence has been assigned the GenBank Accession No. JQ418493. Pathogenicity tests were performed by inoculating six pear fruits of the same cultivar (Spadoncina) after surface disinfesting in 1% sodium hypochlorite and wounding. Mycelial disks (8 mm diameter), obtained from 10-day-old PDA cultures of one strain, were placed on wounds. Six control fruits were inoculated with plain PDA. Fruits were incubated at 25 ± 1°C in plastic boxes. The first symptoms developed 3 days after inoculation. After 5 days, the rot was very evident and B. dothidea was consistently reisolated. Noninoculated fruits remained healthy. The pathogenicity test was performed twice. B. dothidea was identified on decayed pears in the United States (2), South Africa, New Zealand, Japan, and Taiwan (3). To our knowledge, this is the first report of the presence of B. dothidea on pear in Italy, as well as in Europe. In Italy, the economic importance of the disease on pear fruit is at present limited, although the pathogen could represent a risk for this crop. References: (1) S. F. Altschul et al. Nucleic Acids Res., 25:3389, 1997. (2) L. F. Grand. Agr. Res. Serv. Techn. Bull. 240:1, 1985. (3) Y. Ko et al. Plant Prot. Bull. (Taiwan) 35:211, 1993. (4) B. Slippers et al. Mycologia 96:83, 2004.

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First Report of Postharvest Fruit Rot in Persimmon Caused by Phacidiopycnis washingtonensis in Italy

Plant Disease ◽

10.1094/pdis-94-6-0788b ◽

2010 ◽

Vol 94 (6) ◽

pp. 788-788 ◽

Cited By ~ 2

Author(s):

A. Garibaldi ◽

D. Bertetti ◽

M. T. Amatulli ◽

M. L. Gullino

Keyword(s):

United States ◽

Its Region ◽

The United States ◽

Fruit Rot ◽

Diospyros Kaki ◽

Pathogenicity Test ◽

Conidial Suspension ◽

First Report ◽

Pathogenicity Tests ◽

Phacidiopycnis Washingtonensis

Persimmon (Diospyros kaki L.) is widely grown in Italy, the leading producer in Europe. In the fall of 2009, a previously unknown rot was observed on 3% of fruit stored at temperatures between 5 and 15°C in Torino Province (northern Italy). The decayed area was elliptical, firm, and appeared light brown to dark olive-green. It was surrounded by a soft margin. The internal decayed area appeared rotten, brown, and surrounded by bleached tissue. On the decayed tissue, black pycnidia that were partially immersed and up to 0.5 mm in diameter were observed. Light gray conidia produced in the pycnidia were unicellular, ovoid or lacriform, and measured 3.9 to 6.7 × 2.3 to 3.5 (average 5.0 × 2.9) μm. Fragments (approximately 2 mm) were taken from the margin of the internal diseased tissues, cultured on potato dextrose agar (PDA), and incubated at temperatures between 23 and 26°C under alternating light and darkness. Colonies of the fungus initially appeared ash colored and then turned to dark greenish gray. After 14 days of growth, pycnidia and conidia similar to those described on fruit were produced. The internal transcribed spacer (ITS) region of rDNA was amplified using the primers ITS4/ITS6 and sequenced. BLAST analysis (1) of the 502-bp segment showed a 100% similarity with the sequence of Phacidiopycnis washingtonensis Xiao & J.D. Rogers (GenBank Accession No. AY608648). The nucleotide sequence has been assigned the GenBank Accession No. GU949537. Pathogenicity tests were performed by inoculating three persimmon fruits after surface disinfesting in 1% sodium hypochlorite and wounding. Mycelial disks (10 mm in diameter), obtained from PDA cultures of one strain were placed on wounds. Three control fruits were inoculated with plain PDA. Fruits were incubated at 10 ± 1°C. The first symptoms developed 6 days after the artificial inoculation. After 15 days, the rot was very evident and P. washingtonensis was consistently reisolated. Noninoculated fruit remained healthy. The pathogenicity test was performed twice. Since P. washingtonensis was first identified in the United States on decayed apples (2), ‘Fuji’, ‘Gala’, ‘Golden Delicious’, ‘Granny Smith’, ‘Red Chief’, and ‘Stark Delicious’, apple fruits also were artificially inoculated with a conidial suspension (1 × 106 CFU/ml) of the pathogen obtained from PDA cultures. For each cultivar, three surface-disinfested fruit were wounded and inoculated, while three others served as mock-inoculated (sterile water) controls. Fruits were stored at temperatures ranging from 10 to 15°C. First symptoms appeared after 7 days on all the inoculated apples. After 14 days, rot was evident on all fruit inoculated with the fungus, and P. washingtonensis was consistently reisolated. Controls remained symptomless. To our knowledge, this is the first report of the presence of P. washingtonensis on persimmon in Italy, as well as worldwide. The occurrence of postharvest fruit rot on apple caused by P. washingtonensis was recently described in the United States (3). In Italy, the economic importance of the disease on persimmon fruit is currently limited, although the pathogen could represent a risk for apple. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) Y. K. Kim and C. L. Xiao. Plant Dis. 90:1376, 2006. (3) C. L. Xiao et al. Mycologia 97:473, 2005.

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First Report of Fusarium solani Fruit Rot of Pumpkin (Cucurbita pepo) in Trinidad

Plant Disease ◽

10.1094/pdis-93-5-0547b ◽

2009 ◽

Vol 93 (5) ◽

pp. 547-547

Author(s):

S. N. Rampersad

Keyword(s):

Fusarium Solani ◽

Cucurbita Pepo ◽

Morphological Characteristics ◽

Soft Rot ◽

The United States ◽

Fruit Rot ◽

Laboratory Manual ◽

First Report ◽

Pathogenicity Tests ◽

Negative Controls

Trinidad is a major exporter of pumpkins (Cucurbita pepo L.) to other Caribbean countries, Canada, and the United States. Producers and exporters have reported 50 to 80% yield losses because of soft rot and overnight collapse of fruit at the pre- and postharvest stages. Severe fruit rot occurred in fields in Victoria County in South Trinidad between April and May 2006 (mid-to-late dry season) with an increase in the severity and number of affected fruit in the rainy season (July to December). Symptoms began as water-soaked lesions on the fruit of any age at the point of contact with the soil. The disease progressed to a soft rot with leakage and whole fruit collapse. A dark brown, soft decay also developed at the base of the main vines. Fusarium solani was isolated on selective fusarium agar and potato dextrose agar (PDA) (1) after 7 to 10 days of incubation at 25°C. The pathogen was identified by morphological characteristics and pathogenicity tests. Colonies were fast growing with white aerial mycelia and a cream color on the reverse side; hyphae were septate and hyaline, conidiophores were unbranched, and microconidia were abundant, thin walled, hyaline, fusiform to ovoid, generally one to two celled, and 8 to 10 × 2 to 4 μm. Macroconidia were hyaline, two to three celled, moderately curved, thick walled, and 25 to 30 × 4 to 6 μm. Pathogenicity tests for 10 isolates were conducted on 2-week-old pumpkin seedlings (cv. Jamaican squash; seven plants per isolate) and mature pumpkin fruit (2). Briefly, seedlings were inoculated by dipping their roots in a spore suspension (1 × 104 spores per ml) for 20 min. The plants were repotted in sterile potting soil. For negative controls, plant roots were dipped in sterile water. After the rind of fruit was swabbed with 70% ethanol followed by three rinses with sterile distilled water, 0.4-cm-diameter agar plugs of the isolates were inserted into wounds made with a sterile 1-cm-diameter borer. Sterile PDA plugs served as negative controls. Fruit were placed in sealed, clear, plastic bags. Inoculated plants and fruit were placed on greenhouse benches (30 to 32°C day and 25 to 27°C night temperatures) and monitored over a 30-day period. Tests were repeated once. Inoculated fruit developed a brown, spongy lesion that expanded from the initial wound site over a period of approximately 17 days after inoculation. White mycelia grew diffusely over the lesion. Inoculated plants developed yellow and finally necrotic leaves and lesions developed on stems at the soil line approximately 21 days after inoculation. No symptoms developed on the control plants. The fungus was reisolated from symptomatic tissue, fulfilling Koch's postulates. To my knowledge, this is the first report of Fusarium fruit rot of pumpkin in Trinidad. References: (1) J. Leslie and B. Summerell. Page 1 in: The Fusarium Laboratory Manual. Blackwell Publishing, Oxford, 2006. (2) W. H. Elmer. Plant Dis. 80:131, 1996.

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First Report of Lasiodiplodia theobromae Causing Postharvest Fruit Rot on Guava (Psidium guajava) in Malaysia

Plant Disease ◽

10.1094/pdis-12-20-2732-pdn ◽

2021 ◽

Author(s):

Kar Yan Zee ◽

Norhayu Asib ◽

Siti Izera Ismail

Keyword(s):

Morphological Characteristics ◽

Its Region ◽

Psidium Guajava ◽

Fruit Rot ◽

Pathogenicity Test ◽

Tropical Fruit ◽

Lasiodiplodia Theobromae ◽

First Report ◽

Guava Fruit ◽

Initial Symptoms

Guava (Psidium guajava L.) is an economically important tropical fruit crop and is cultivated extensively in Malaysia. In September and October 2019, postharvest fruit rot symptoms were observed on 30% to 40% of guava fruit cv. Kampuchea in fruit markets of Puchong and Ipoh cities in the states of Selangor and Perak, Malaysia. Initial symptoms appeared as brown, irregular, water-soaked lesions on the upper portion of the fruit where it was attached to the peduncle. Subsequently, lesions then progressed to cover the whole fruit (Fig.1A). Lesions were covered with an abundance of black pycnidia and grayish mycelium. Ten symptomatic guava fruit were randomly collected from two local markets for our investigation. For fungal isolation, small fragments (5×5 mm) were excised from the lesion margin, surface sterilized with 0.5% NaOCl for 2 min, rinsed three times with sterile distilled water, placed on potato dextrose agar (PDA) and incubated at 25 °C with 12-h photoperiod for 2-3 days. Eight single-spore isolates with similar morphological characteristics were obtained and two representative isolates (P8 and S9) were characterized in depth. Colonies on PDA were initially composed of grayish-white aerial mycelium, but turned dark-gray after 7 days (Fig. 1B). Abundant black pycnidia were observed after incubation for 4 weeks. Immature conidia were hyaline, aseptate, ellipsoid, thick-walled, and mature conidia becoming dark brown and 1-septate with longitudinal striations, 25.0 − 27.0 ± 2.5 × 13.0 − 14.0 ± 1.0 μm (n = 30) (Fig.1C, D). On the basis of morphology, both representative isolates were identified as Lasiodiplodia theobromae (Pat.) Griffon & Maubl. (Alves et al. 2008). For molecular identification, genomic DNA of the two isolates was extracted using the DNeasy plant mini kit (Qiagen, USA). The internal transcribed spacer (ITS) region of rDNA and translation elongation factor 1-alpha (EF1-α) genes were amplified using ITS5/ITS4 and EF1-728F/EF1-986R primer set, respectively (White et al. 1990, Carbone and Kohn 1999). BLASTn analysis of the resulting ITS and EF1-α sequences indicated 100% identity to L. theobromae ex-type strain CBS 164.96 (GenBank accession nos: AY640255 and AY640258, respectively) (Phillips et al. 2013). The ITS (MW380428, MW380429) and EF1-α (MW387153, MW387154) sequences were deposited in GenBank. Phylogenetic analysis using the maximum likelihood based on the combined ITS-TEF sequences indicated that the isolates formed a strongly supported clade (100% bootstrap value) to the related L. theobromae (Kumar et al. 2016) (Fig.2). A pathogenicity test of two isolates was conducted on six healthy detached guava fruits per isolate. The fruit were surface sterilized using 70% ethanol and rinsed twice with sterile water prior inoculation. The fruit were wound-inoculated using a sterile needle according to the method of de Oliveira et al. (2014) and five-mm-diameter mycelial agar plugs from 7-days-old PDA culture of the isolates were placed onto the wounds. Six additional fruit were wound inoculated using sterile 5-mm-diameter PDA agar plugs to serve as controls. Inoculated fruit were placed in sterilized plastic container and incubated in a growth chamber at 25 ± 1 °C, 90% relative humidity with a photoperiod of 12-h. The experiment was conducted twice. Five days after inoculation, symptoms as described above developed on the inoculated sites and caused a fruit rot, while control treatment remained asymptomatic. L. theobromae was reisolated from all symptomatic tissues and confirmed by morphological characteristics and confirmed by PCR using ITS region. L. theobromae has recently been reported to cause fruit rot on rockmelon in Thailand (Suwannarach et al. 2020). To our knowledge, this is the first report of L. theobromae causing postharvest fruit rot on guava in Malaysia. The occurrence of this disease needs to be monitored as this disease can reduce the marketable yield of guava. Preventive strategies need to be developed in the field to reduce postharvest losses.

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First Report of Leaf Spot of Orange Coneflower (Rudbeckia fulgida) Caused by a Phoma sp. in Italy

Plant Disease ◽

10.1094/pdis-94-6-0788a ◽

2010 ◽

Vol 94 (6) ◽

pp. 788-788

Author(s):

A. Garibaldi ◽

D. Bertetti ◽

M. T. Amatulli ◽

M. L. Gullino

Keyword(s):

Leaf Spot ◽

Morphological Characteristics ◽

Its Region ◽

The United States ◽

Pathogenicity Test ◽

First Report ◽

Humidity Chamber ◽

Pathogenicity Tests ◽

Symptomatic Tissue ◽

White Mycelium

Rudbeckia fulgida (orange coneflower) is an herbaceous species (Asteraceae) grown in full sun in flower beds and borders in gardens. In the summer of 2009, a previously unknown leaf spot was observed on R. fulgida plants in three private gardens located near Biella (northern Italy). Leaves of infected plants showed extensive and irregular, dark brown, necrotic lesions that were slightly sunken with a well-defined border. Lesions initially ranged from 0.5 to 3 mm in diameter and eventually coalesced to cover the entire leaf, which curled without falling. At a later stage, stems were also affected, causing death of the plant. The disease affected 90% of plants. Dark brown pycnidia, 68 to 195 × 60 to 165 (average 135 × 117) μm in diameter, containing hyaline (light gray in mass), and ellipsoid, nonseptate conidia measuring 4.0 to 7.0 × 2.4 to 3.5 (average 5.4 × 3.0) μm were observed on symptomatic tissue. On the basis of these morphological characteristics, the fungus was related to the genus Phoma. Diseased tissue was excised from the margin of lesions, immersed in a solution containing 1% sodium hypochlorite for 2 to 3 s, rinsed in sterile distilled water, and then cultured on potato dextrose agar (PDA) medium. Fungal colonies initially produced a white mycelium that became greenish gray when incubated at temperatures ranging between 22 and 25°C under alternating daylight and darkness (13 h of light and 11 h of dark). After 14 days of incubation, unicellular, cylindrical or truncated cone-shaped, light brown chlamydospores measuring 6 to 12 μm in diameter developed in long chains. The internal transcribed spacer (ITS) region of rDNA was amplified using the primers ITS4/ITS6 and sequenced. BLAST analysis (1) of the 498-bp segment showed 100% homology with a sequence of a Phoma sp. (EF585395). The nucleotide sequence of our isolate was assigned GenBank Accession No. GU573979. Pathogenicity tests were performed by placing 100 ml of a water homogenate of mycelium (1 × 105 mycelial fragments/ml) obtained from 15-day-old PDA cultures of the fungus on leaves of three healthy 4-month-old potted R. fulgida plants. Three plants inoculated with a homogenate of PDA served as controls. Plants were maintained in a greenhouse, in a high humidity chamber for 7 days after inoculation, at temperatures ranging from 18 to 22°C and under high relative humidity conditions (70 to 90%). The first foliar lesions developed on leaves 7 days after inoculation, and after 10 to 12 days, 80% of leaves were severely infected. Control plants remained healthy. The organism reisolated on PDA from leaf lesions was identical in morphology to the isolate used for inoculation. The pathogenicity test was carried out twice. To our knowledge, this is the first report of the presence of a Phoma sp. on R. fulgida in Italy. Mycosphaerella ligulicola was reported on Rudbeckia sp. (2), while M. rudbeckiae and Phoma exigua have been reported on R. hirta (3). Currently, the economic importance of this disease is limited, but may become a more significant problem if the cultivation of this species increases. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) C. G. C. Chesters and J. P. Blakeman. Ann. Appl. Biol. 60:385, 1967. (3) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St. Paul, MN, 1989.

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First report of postharvest fruit rot on passion fruit (Passiflora edulis) caused by Lasiodiplodia theobromae in Mainland China

Plant Disease ◽

10.1094/pdis-06-20-1346-pdn ◽

2020 ◽

Author(s):

Wu Zhang ◽

Xue Li Niu ◽

Jin Yu Yang

Keyword(s):

Southern China ◽

Morphological Characteristics ◽

Its Region ◽

Passion Fruit ◽

Fruit Rot ◽

Pathogenicity Test ◽

Single Spore ◽

Passiflora Edulis ◽

Lasiodiplodia Theobromae ◽

First Report

As an economically important tropical and subtropical fruit crop, passion fruit (Passiflora edulis Sims) is widely planted in many provinces of southern China. In April 2017, postharvest fruit rot was observed on 15% to 25% of passion fruit in several fruit markets of Zhanjiang City in Guangdong Province. Initial disease symptoms on infected fruit were irregular, brown, water-soaked lesions, which enlarged into large black and sunken patches. Lesions were usually covered with an abundance of little black dots (pycnidia) and black-gray hyphae. For the pathogen isolation, fifteen symptomatic fruit were randomly collected from three local markets. Fourteen single-spore fungal isolates with similar morphology ware isolated from the infected tissues. Two isolates (ZW 49-1 and ZW 50-1) were randomly selected to further study. The colonies on PDA were initially greyish-white and became dark-gray with age. Abundant globular and irregular pycnidia were observed after incubation at 25 °C for 3 weeks. The conidia of the fungus were initially hyaline, unicellular, apex rounded, thick-walled, and ellipsoid, becoming dark brown, bicellular with longitudinal striations at maturity, 26.4 ± 2.5 × 13.4 ± 1.2 μm (n = 50). The morphology of the fungus resembled Lasiodiplodia theobromae (Pat.) Griff. & Maubl. (Phillips et al. 2013). To confirm species identification, the partial internal transcribed spacer (ITS) region of rDNA, translation elongation factor-alpha (EF1-α) and β-tubulin (TUB) gene were amplified from genomic DNA of the two isolates with the ITS1/ITS4, EF1-688F/EF1-986R, and Bt2a/Bt2b primers, respectively (Glass and Donaldson 1995; Alves et al. 2008; White et al. 1990). Base on the BLASTn analysis, the ITS (MT644473, MT644474), EF1-α (MT649210, MT649211) and TUB (MT649212, MT649213) sequences of both isolates were 100%, 99% and 100% similarity to the L. theobromae CBS 164.96 ex-type sequences in the NCBI database (AY640255, AY640258, and KU887532, respectively) (Phillips et al. 2013). For pathogenicity test, asymptomatic passion fruit were previously disinfested in 0.5 % sodium hypochlorite and superficially wounded with a sterile needle. Five-mm-diameter plugs with mycelial taken from 5-day-old PDA colonies were placed on the wounds. Sterile PDA plugs were used as negative controls. Each treatment had five replicates and the test was repeated twice. Fruit were maintained in plastic boxes to keep at 25°C for one week. One week after inoculation, gray mycelia had covered a majority of the fruit surface and caused a black, sunken rot. The inoculated fungus was reisolated and confirmed as L. theobromae by morphological characteristics. The mock inoculated fruit remained asymptomatic. The occurrence of fruit rot on passion fruit caused by L. theobromae was reported in Taiwan, China recently (Huang et al., 2019). To our knowledge, this is the first report of L. theobromae causing postharvest fruit rot on passion fruit in the Chinese mainland.

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First Report of White Mold Caused by Sclerotinia sclerotiorum on Sweet Basil in Turkey

Plant Disease ◽

10.1094/pdis-92-10-1471c ◽

2008 ◽

Vol 92 (10) ◽

pp. 1471-1471 ◽

Cited By ~ 1

Author(s):

F. M. Tok

Keyword(s):

Sclerotinia Sclerotiorum ◽

Morphological Characteristics ◽

The United States ◽

Ocimum Basilicum ◽

Pathogenicity Test ◽

Distilled Water ◽

First Report ◽

Sweet Basil ◽

Pathogenicity Tests ◽

Filter Papers

In February of 2008, wilt and collapse of sweet basil (Ocimum basilicum L.) was observed on approximately 20% of the plants in a commercial greenhouse in Demre, Antalya, Turkey. Crown and stems of infected plants were necrotic; leaves turned brown and wilted. Profuse, white mycelia and occasionally black sclerotia were found inside and outside of affected stems. Sclerotinia sclerotiorum (Lib). de Bary, identified based on morphological characteristics was isolated from sclerotia and symptomatic stems on potato dextrose agar amended with tetracycline. To conduct pathogenicity tests, sclerotia produced on carrot discs were surface disinfested in 70% ethanol and dried on sterilized filter papers. Ten sclerotia were placed in 9-cm-diameter glass petri plates containing 15 ml of sterilized distilled water. Plates were wrapped with Parafilm and incubated at 4°C for 5 to 6 weeks in the dark. Plates were then incubated at 15°C in 12 h of dark and 12 h of light. Apothecia developed after 2 weeks. Ascospores were harvested from apothecia with distilled water by crushing and shaking the apothecia in centrifuge tubes. Thirty basil plants sprayed with ascospores (106 spores per ml) were maintained in a growth chamber at 22°C and 90% humidity. After 2 weeks, necrotic leaves and stems were observed on all inoculated plants. S. sclerotiorum was recovered from symptomatic tissues. No symptoms developed on the 30 basil plants sprayed with sterile distilled water. The pathogenicity test was repeated with similar results. S. sclerotiorum on basil has been reported in Canada (4), the United States, (2,3), and Italy (1). To our knowledge, this is the first report of S. sclerotiorum on basil in Turkey. References: (1) A. Garibaldi et al. Plant Dis. 81:124, 1997. (2) G. E. Holcomb and M. J. Reed. Plant Dis. 78:924, 1994. (3) S. T. Koike. Plant Dis. 84:1342, 2000. (4) T. C. Paulitz. Plant Dis. 81:229, 1997.

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First Report of Stem and Foliage Blight of Chrysanthemum Caused by Phytophthora drechsleri in the United States

Plant Disease ◽

10.1094/pdis-03-21-0631-pdn ◽

2021 ◽

Author(s):

Charles Krasnow ◽

Nancy Rechcigl ◽

Jennifer Olson ◽

Linus Schmitz ◽

Steven N. Jeffers

Keyword(s):

United States ◽

South Carolina ◽

Sequence Similarity ◽

Morphological Characteristics ◽

The United States ◽

Universal Primers ◽

Broad Host Range ◽

Pathogenicity Test ◽

First Report ◽

Foliage Blight

Chrysanthemum (Chrysanthemum × morifolium) plants exhibiting stem and foliage blight were observed in a commercial nursery in eastern Oklahoma in June 2019. Disease symptoms were observed on ~10% of plants during a period of frequent rain and high temperatures (26-36°C). Dark brown lesions girdled the stems of symptomatic plants and leaves were wilted and necrotic. The crown and roots were asymptomatic and not discolored. A species of Phytophthora was consistently isolated from the stems of diseased plants on selective V8 agar (Lamour and Hausbeck 2000). The Phytophthora sp. produced ellipsoid to obpyriform sporangia that were non-papillate and persistent on V8 agar plugs submerged in distilled water for 8 h. Sporangia formed on long sporangiophores and measured 50.5 (45-60) × 29.8 (25-35) µm. Oospores and chlamydospores were not formed by individual isolates. Mycelium growth was present at 35°C. Isolates were tentatively identified as P. drechsleri using morphological characteristics and growth at 35°C (Erwin and Ribeiro 1996). DNA was extracted from mycelium of four isolates, and the internal transcribed spacer (ITS) region was amplified using universal primers ITS 4 and ITS 6. The PCR product was sequenced and a BLASTn search showed 100% sequence similarity to P. drechsleri (GenBank Accession Nos. KJ755118 and GU111625), a common species of Phytophthora that has been observed on ornamental and vegetable crops in the U.S. (Erwin and Ribeiro 1996). The gene sequences for each isolate were deposited in GenBank (accession Nos. MW315961, MW315962, MW315963, and MW315964). These four isolates were paired with known A1 and A2 isolates on super clarified V8 agar (Jeffers 2015), and all four were mating type A1. They also were sensitive to the fungicide mefenoxam at 100 ppm (Olson et al. 2013). To confirm pathogenicity, 4-week-old ‘Brandi Burgundy’ chrysanthemum plants were grown in 10-cm pots containing a peat potting medium. Plants (n = 7) were atomized with 1 ml of zoospore suspension containing 5 × 103 zoospores of each isolate. Control plants received sterile water. Plants were maintained at 100% RH for 24 h and then placed in a protected shade-structure where temperatures ranged from 19-32°C. All plants displayed symptoms of stem and foliage blight in 2-3 days. Symptoms that developed on infected plants were similar to those observed in the nursery. Several inoculated plants died, but stem blight, dieback, and foliar wilt were primarily observed. Disease severity averaged 50-60% on inoculated plants 15 days after inoculation. Control plants did not develop symptoms. The pathogen was consistently isolated from stems of symptomatic plants and verified as P. drechsleri based on morphology. The pathogenicity test was repeated with similar results. P. drechsleri has a broad host range (Erwin and Ribeiro 1996; Farr et al. 2021), including green beans (Phaseolus vulgaris), which are susceptible to seedling blight and pod rot in eastern Oklahoma. Previously, P. drechsleri has been reported on chrysanthemums in Argentina (Frezzi 1950), Pennsylvania (Molnar et al. 2020), and South Carolina (Camacho 2009). Chrysanthemums are widely grown in nurseries in the Midwest and other regions of the USA for local and national markets. This is the first report of P. drechsleri causing stem and foliage blight on chrysanthemum species in the United States. Identifying sources of primary inoculum may be necessary to limit economic loss from P. drechsleri.

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First Report of Rhizoctonia solani AG 4 on Lamb's Lettuce in Italy

Plant Disease ◽

10.1094/pd-90-1109c ◽

2006 ◽

Vol 90 (8) ◽

pp. 1109-1109 ◽

Cited By ~ 2

Author(s):

A. Garibaldi ◽

G. Gilardi ◽

M. L. Gullino

Keyword(s):

Rhizoctonia Solani ◽

Morphological Characteristics ◽

Northern Italy ◽

Crown Rot ◽

Pathogenicity Test ◽

First Report ◽

Pathogenicity Tests ◽

Hyphal Diameter ◽

Wheat Kernels ◽

Extensive Necrosis

Lamb's lettuce or corn salad (Valerianella olitoria) is increasingly grown in Italy and used primarily in the preparation of mixed processed salad. In the fall of 2005, plants of lamb's lettuce, cv Trophy, exhibiting a basal rot were observed in some commercial greenhouses near Bergamo in northern Italy. The crown of diseased plants showed extensive necrosis, progressing to the basal leaves, with plants eventually dying. The first symptoms, consisting of water-soaked zonate lesions on basal leaves, were observed on 30-day-old plants during the month of October when temperatures ranged between 15 and 22°C. Disease was uniformly distributed in the greenhouses, progressed rapidly in circles, and 50% of the plants were affected. Diseased tissue was disinfested for 1 min in 1% NaOCl and plated on potato dextrose agar amended with 100 μg/liter of streptomycin sulfate. A fungus with the morphological characteristics of Rhizoctonia solani was consistently and readily isolated and maintained in pure culture after single-hyphal tipping (3). The five isolates of R. solani, obtained from affected plants successfully anastomosed with tester isolate AG 4, no. RT 31, received from R. Nicoletti of the Istituto Sperimentale per il Tabacco, Scafati, Italy (2). The hyphal diameter at the point of anastomosis was reduced, and cell death of adjacent cells occurred (1). Pairings were also made with AG 1, 2, 3, 5, 7, and 11 with no anastomoses observed between the five isolates and testers. For pathogenicity tests, the inoculum of R. solani (no. Rh. Vale 1) was grown on autoclaved wheat kernels at 25°C for 10 days. Plants of cv. Trophy were grown in 10-liter containers (20 × 50 cm, 15 plants per container) on a steam disinfested substrate (equal volume of peat and sand). Inoculations were made on 20-day-old plants by placing 2 g of infected wheat kernels at each corner of the container with 3 cm as the distance to the nearest plant. Plants inoculated with clean wheat kernels served as controls. Three replicates (containers) were used. Plants were maintained at 25°C in a growth chamber programmed for 12 h of irradiation at a relative humidity of 80%. The first symptoms, consisting of water-soaked lesions on the basal leaves, developed 5 days after inoculation with crown rot and plant kill in 2 weeks. Control plants remained healthy. R. solani was consistently reisolated from infected plants. The pathogenicity test was carried out twice with similar results. This is, to our knowledge, the first report of R. solani on lamb's lettuce in Italy as well as worldwide. The isolates were deposited at the AGROINNOVA fungal collection. The disease continues to spread in other greenhouses in northern Italy. References: (1) D. Carling. Rhizoctonia Species: Pages 37–47 in: Taxonomy, Molecular Biology, Ecology, Pathology and Disease Control. B. Sneh et al., eds. Kluwer Academic Publishers, the Netherlands, 1996. (2) J. Parmeter et al. Phytopathology, 59:1270, 1969. (3) B. Sneh et al. Identification of Rhizoctonia Species. The American Phytopathological Society, St. Paul, MN, 1996.

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First Report of Fusarium pernambucanum Causing Fruit Rot of Muskmelon in China

Plant Disease ◽

10.1094/pdis-07-21-1520-pdn ◽

2021 ◽

Author(s):

Xianping Zhang ◽

Jiwen Xia ◽

Jiakui Liu ◽

Dan Zhao ◽

Lingguang Kong ◽

...

Keyword(s):

Phylogenetic Analyses ◽

Apical Cell ◽

Morphological Characteristics ◽

Fruit Rot ◽

Likelihood Method ◽

Correct Identification ◽

Pathogenicity Test ◽

First Report ◽

The Core ◽

Representative Isolate

Muskmelon (Cucumis melo L.) is one of the most widely cultivated and economically important fruit crops in the world. However, many pathogens can cause decay of muskmelons; among them, Fusarium spp. is the most important pathogen, affecting fruit yield and quality (Wang et al. 2011). In May 2017, fruit rot symptoms were observed on ripening muskmelons (cv. Jipin Zaoxue) in several fields in Liaocheng of Shandong Province, China. Symptoms appeared as brown, water-soaked lesions, irregularly circular in shape, with the lesion size ranging from a small spot (1 to 2 cm) to the decay of the entire fruit. The core and the surface of the infected fruit were covered with white to rose-reddish mycelium. Two infected muskmelons were collected from each of two fields, 10 km apart. Tissues from the inside of the infected fruit were surface disinfected with 75% ethanol for 30 s, and cultured on potato dextrose agar (PDA) at 25 °C in the dark for 5 days. Four purified cultures were obtained using the single spore method. On carnation leaf agar (CLA), macroconidia had a pronounced dorsiventral curvature, falcate, 3 to 5 septa, with tapered apical cell, and foot-shaped basal cell, measuring 19 to 36 × 4 to 6 μm. Chlamydospores were abundant, 5.5–7.5 μm wide, and 5.5–10.5 μm long, ellipsoidal or subglobose. No microconidia were observed. These morphological characteristics were consistent with the descriptions of F. pernambucanum (Santos et al. 2019). Because these isolates had similar morphology, one representative isolate was selected for multilocus phylogenetic analyses. DNA was extracted from the representative isolate using the CTAB method. The nucleotide sequences of the internal transcribed spacers (ITS) (White et al. 1990), translation elongation factor 1-α gene (TEF1), RNA polymerase II second largest subunit gene (RPB2), calmodulin (CAM) (Xia et al. 2019) were amplified using specific primers, sequenced, and deposited in GenBank (MN822926, MN856619, MN856620, and MN865126). Based on the combined dataset of ITS, TEF1, RPB2, CAM, alignments were made using MAFFT v. 7, and phylogenetic analyses were processed in MEGA v. 7.0 using the maximum likelihood method. The studied isolate (XP1) clustered together with F. pernambucanum reference strain URM 7559 (99% bootstrap). To perform pathogenicity test, 10 μl of spore suspensions (1 × 106 conidia/ml) were injected into each muskmelon fruit using a syringe, and the control fruit was inoculated with 10 μl of sterile distilled water. There were ten replicated fruits for each treatment. The test was repeated three times. After 7 days at 25 °C, the interior of the inoculated muskmelons begun to rot, and the rot lesion was expanded from the core towards the surface of the fruit, then white mycelium produced on the surface. The same fungus was re-isolated from the infected tissues and confirmed to fulfill the Koch’s postulates. No symptoms were observed on the control muskmelons. To our knowledge, this is the first report of F. pernambucanum causing of fruit rot of muskmelon in China. Considering the economic value of the muskmelon crop, correct identification can help farmers select appropriate field management measures for control of this disease.

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