First report of Diaporthe eres causing branch canker on Cinnamomum camphora (camphor tree) in Jiangxi Province, China

In September 2019, approximately 75 to 90% of camphor trees (Cinnamomum camphora) were observed with cankers and branch dieback symptoms in Anyi (N28°32’54’’, E115°37’52’’) and Xinyu (N27°37’38’’, E114°50’25’’) county (Jiangxi Province, China). The symptoms included dark brown to dark, oval-shaped canker lesions, sunken and cracked longitudinally, cracked and evenly swelling, or reddish brown (Figure 1 A-D). Samples were collected from symptomatic branches and were cut into small pieces (ca. 0.5 cm × 0.5 cm × 0.5 cm). Sections were surface sterilized as described by Zhang et al. (2020), then placed on potato dextrose agar amended with 0.01% penicillin and 0.015% streptomycin sulfate and incubated in the laboratory at 25℃ with darkness. After 3 to 5 days, mycelium growing out from tissues were transferred onto PDA medium. In total, 68 fungal isolates including 22 isolates of Diaporthe sp. were obtained from cankers and then were classified into five categories based on morphological characteristics and sequencing of the ITS for morphological representative strains. Pathogenicity tests were conducted in the greenhouse (Figure 1 E-M) and field (Figure 1 N-Q). Branches were surface sterilized and inoculated as described by Prencipe et al. (2017). In the greenhouse, a total of 13 representative isolates (including 6 isolates of Diaporthe sp., 2 isolates of Neofusicoccum sp., 2 isolates of Botryosphaeria sp. and 3 isolates of Colletotrichum sp.) were selected and evaluated using 2-year-old seedlings of camphor tree in pots with 5 replicates per isolate, in which 3 isolates of Collectotrichum sp. had no pathogenicity. Then, two isolates of Diaporthe sp. (Z4 and Z7) were selected for field experiment. In field tests, the same method was used as in the greenhouse. The inoculated and control branches were collected 40 days after inoculation and the fungi were isolated and placed on PDA plates to recover the inoculated fungi and complete Koch’s postulates. Both isolates of Diaporthe sp. produced canker symptoms on the branches. Isolate Z4 caused discoloration also on the branch without wounding. Both isolates produced pycnidia scattered in PDA plates supplemented with stems of alfalfa, were dark brown to black, globose to subglobose (Figure 1 T). Alpha conidia were cylindrical, 5.72-9.98 µm (mean 7.64 µm) × 2.15-3.13 µm (mean 2.69 µm) (n = 30) (Figure 1 S, red arrow), while beta conidia were biguttulate, one-celled, hyaline, non-septate, and 16.21-25.52 µm (mean 21.60 µm) × 0.76~1.65 µm (mean 1.14 µm) (n = 30, green arrow) (Figure 1 S). Five isolates (Z4, S-Z4, P-Z4, Z7 and S-Z7) including those used for pathogenicity test were selected for multi-locus phylogenetic analyses of ITS (White et al., 1990), TEF1-α and TUB2 (Glass et al. 1995) gene sequences, which the accession number was MW036358- MW036362 for ITS, MW052267- MW052271 for TEF1- α, MW052276-MW052280 for TUB2. Based on the phylogenetic tree analysis using IQ-TREE 2, all five isolates were identified as D. eres (Figure 2). D. eres has been reported to cause canker on many different woody plants, such as almond (Holland et al. 2020), peach (Prencipe et al. 2017), hazelnut (Wiman et al. 2019), and so on. However, this is the first report worldwide of D. eres causing disease on Cinnamomum camphora in China.

Download Full-text

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.

Download Full-text

First Report of Fruit Rot Caused by Fusarium luffae in Muskmelon in China

Plant Disease ◽

10.1094/pdis-12-21-2666-pdn ◽

2022 ◽

Author(s):

Xianping Zhang ◽

Xuedong Cao ◽

Qingqing Dang ◽

Yongguang Liu ◽

Xiaoping Zhu ◽

...

Keyword(s):

Phylogenetic Analyses ◽

Apical Cell ◽

Morphological Characteristics ◽

Fruit Rot ◽

Likelihood Method ◽

Correct Identification ◽

Pathogenicity Test ◽

Fusarium Spp ◽

First Report ◽

The Core

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 muskmelon fruit, including Fusarium spp.. Fusarium spp. are the most important pathogen, affecting muskmelon fruit yield and quality (Wang et al. 2011). In August 2020, fruit rot symptoms were observed on ripening muskmelons (cv. Tianbao) in several fields in Jiyang District, Jinan City of Shandong Province, China. The incidences of infected muskmelon ranged from 15% to 30% and caused an average 20% yield loss. Symptoms appeared as pale brown, water-soaked lesions that were irregular in shape, with the lesion sizes ranging from a small spot (1 to 2 cm) to decay of the entire fruit. The core and surface of infected fruit were colonized and covered with white mycelia. Two infected muskmelons were collected from two fields, 3.5 km apart. Tissues removed from inside 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), 3 to 5 septate, falcate, with a pronounced dorsiventral curvature macroconidia with tapered apical cell, and foot-shaped basal cell, measuring 20 to 40 × 3.5 to 4.5 μm. Microconidia and chlamydospores were not observed. These morphological characteristics were consistent with the description of F. luffae (Wang et al., 2019). Because these isolates had similar morphology, two representative isolates (XP11 and XP12) were selected for multilocus phylogenetic analyses. DNA was extracted from the representative isolates using a CTAB method. Nucleotide sequences of the internal transcribed spacers (ITS) (White et al. 1990), calmodulin (CAM), RNA polymerase II second largest subunit (RPB2), translation elongation factor 1-α gene (TEF1) (Xia et al. 2019) were amplified using specific primers, sequenced, and deposited in GenBank (ITS: MW391509 and MW391510, CAM: MW392789 and MW392790, RPB2: MW392797 and MW392798, TEF1: MW392793 and MW392794). Alignments of a combined dataset of ITS, CAM, RPB2 and TEF1 were made using MAFFT v. 7, and phylogenetic analyses were conducted in MEGA v. 7.0 using the maximum likelihood method. The muskmelon isolates (XP11 and XP12) clustered together with the F. luffae reference strain LC12167 (99% bootstrap). To perform a pathogenicity test, 10 μl of conidial 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 expanded from the core towards the surface of the fruit, then white mycelia were produced on the surface. Ten isolations were re-isolated from the infected tissues and confirmed to fulfill Koch’s postulates. No symptoms were observed on the control muskmelons. To our knowledge, this is the first report of fruit rot caused by F. luffae in 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.

Download Full-text

First Report of Postharvest Fruit Rot Disease of Yellow Peach Caused by Diaporthe eres in China

Plant Disease ◽

10.1094/pdis-11-21-2484-pdn ◽

2021 ◽

Author(s):

Yusen Xiao ◽

Guanghua Huo ◽

Lili Liu ◽

Chunxi Yang ◽

Chaoyu Cui

Keyword(s):

Management Practices ◽

Phylogenetic Analyses ◽

Morphological Characteristics ◽

Its Region ◽

Fruit Rot ◽

Economic Losses ◽

Pathogenicity Test ◽

Transparent Plastic ◽

First Report ◽

Agar Disc

The yellow peach (Amygdalus persica), is a fruit crop native to China with golden peel and pulp that is of particular interest in the fruit markets. In August of 2021, yellow peaches showing fruit rot symptoms were purchased from a commercial market in Linyi city, Shandong province, China. The symptoms included circular, tan to brown in color, rotten, necrotic lesions, and whitish mycelium mass in the center of the lesions. The infected fruit were surface disinfected with 1% NaClO for 30 s and rinsed with sterile distilled water three times. Diseased tissues from the infected fruits were cut into small segments, aseptically shifted onto potato dextrose agar media containing petri plates and incubated at 25℃ for 5 days. Eight isolates were obtained in total from two isolation experiments. Fungal colonies were initially white, aerial, fluffy at first, and gradually turned brown to gray, with black stromata at maturity. Alpha conidia were aseptate，hyaline，fusiform to ellipsoidal，and ranged in size from 4.16 to 7.76 µm × 1.95 to 3.14 µm (n=30). Beta conidia were aseptate, hyaline, filiform, curved to hamate, and 15.91 to 22.55 µm × 0.82 to 1.66 µm (n=30). The morphological characteristics were consistent with those of Diaporthe species (Gomes et al. 2013). For further identification, a multigene phylogenetic analysis was carried out. The internal transcribed spacer (ITS) region, translation elongation factor 1-α (TEF1-α), histone H3 (HIS), calmodulin (CAL), and β-tubulin (TUB) genes of two representative isolates were amplified by using primers ITS1/ITS4, EF1-728F/EF1-986R, CYLH3F/H3-1b，CAL228F/CAL737R, and Bt2a/Bt2b (Chaisiri et al. 2021), respectively. The sequences were deposited in GenBank (Accession No. OL375154 for ITS; OL406409 for TEF1-α; OL406410 for HIS; OL106407 for CAL; OL406408 for TUB). phylogenetic analyses were conducted using the concatenation of multiple sequences (ITS, TEF1-α, HIS, CAL, TUB) with Maximum Likelihood (ML) in IQtree v1.5.6 (Nguyen et al. 2015). Based on the morphological and phylogenetic characters, the isolates were identified as D. eres. A Pathogenicity test was performed by wound inoculation on harvested fruits of A. persica Variety ‘Jinxiu’. Mature and healthy yellow peaches purchased from Shandong, Anhui, and Hunan Provinces in China were surface sterilized with 1% NaClO solution for 1 minute, rinsed with sterile water and dried. Each fruit was wounded with a sterile scalpel creating a 2-3 mm incision on the peel. A 5 mm agar disc with mycelium grown on PDA at 28℃ for 7 days was placed on wound and sealed with parafilm. Sterile PDA plugs were used as controls. Ten fruit were used for each treatment and the assays were repeated three times. Inoculated fruit were placed in sterilized transparent plastic cans containing wet, sterile paper towels. After 5 days of incubation at 25℃, the same rot symptoms were observed on fruits inoculated with mycelium and the control remained symptomless. D. eres was re-isolated from the lesions of inoculated fruits and the pathogen identification was confirmed by molecular analysis, thus fulfilling complete Koch’s postulates. Although D. eres was previously reported on peach trees of causing shoot blight (Thomidis and Michailides 2009) and stem canker (Prencipe et al. 2017). To our knowledge, this is the first report of D. eres causing postharvest fruit rot of yellow peach in China and it may lead to considerable economic losses in the peach industry should post-harvest disease management practices not be implemented.

Download Full-text

First Report of Lasiodiplodia theobromae Causing Branch Dieback on Castor Bean in Zhanjiang, China

Plant Disease ◽

10.1094/pdis-08-20-1723-pdn ◽

2021 ◽

Author(s):

Jian Rong Tang ◽

Yue Lian Liu ◽

Xue Gui Yin ◽

Jian Nong Lu ◽

Yu Han Zhou

Keyword(s):

Castor Bean ◽

Ricinus Communis ◽

Elongation Factor ◽

Morphological Characteristics ◽

Aerial Mycelium ◽

Molecular Data ◽

Pathogenicity Test ◽

First Report ◽

Branch Dieback ◽

Β Tubulin

Castor bean (Ricinus communis L.) is an oil crop of significant economic importance in the industry and medicine. In August 2019, a branch dieback disease was observed on castor bean in a field in Zhanjiang (21.17°N, 110.18°E), China. The incidence rate was 35% (n=600 investigated plants). Symptoms were discoloration of leaves, branch dieback, and discoloration of internal stem tissues. The disease had spread to the whole branches and causing the plant to die. Seven diseased branches were collected from seven plants. Margins between healthy and diseased tissues were cut into 2 mm × 2 mm pieces. The surfaces were disinfested with 75% ethanol for 30 s and 2% sodium hypochlorite for 60 s. Then, the samples were rinsed thrice in sterile water, placed on PDA, and incubated at 28 °C. Pure cultures were obtained by transferring the hyphal tips to new PDA plates. Eighteen isolates were obtained (the isolate rate of 75%), which were the same fungus on the basis of morphological characteristics and molecular analysis of the internal transcribed spacer (ITS). A single representative isolate (RiB-1) was used for further study. The colony of RiB-1 was 5 cm in diameter on the 5th day on the PDA culture. The colony was greenish gray with an irregularly distributed and fluffy aerial mycelium, which turned black after 10 days. The mature conidia were 21.3–26.5 µm × 12.2–15.7 µm in size (n=100) and had two ovoid, dark brown cells with longitudinal striations. The morphological characteristics of the colonies were consistent with the description of Lasiodiplodia sp. (Alves et al. 2008). Three regions of the ITS, translation elongation factor (EF1-α), and β-tubulin genes were amplified and sequenced with the primer pairs ITS1/ITS4 (White et al. 1990), EF1-728F/EF1-986R (Alves et al. 2008), and Bt2a/Bt2b (Glass and Donaldson 1995), respectively. The resulting sequences were deposited in the GenBank under accession numbers MN759432 (ITS), MN719125 (EF1-α), and MN719128 (β-tubulin). BLASTn analysis demonstrated that these sequences were 100% identical to the corresponding ITS (MK530052), EF1-α (MK423878), and β-tubulin (MN172230) sequences of L. theobromae. Based on the morphological and molecular data, RiB-1 was determined as L. theobromae. A pathogenicity test was performed in a greenhouse with 80% relative humidity at 25 °C to 30 °C. Ten healthy plants of Zi Bi No. 5 castor bean (1-month-old) were grown in pots with one plant in each pot. Five pots were wound-inoculated with 5-mm-diameter mycelial plugs obtained from 7-day cultures. Five additional pots treated with PDA plugs served as the controls. Inoculated stems were moisturized with sterile cotton for five days. The test was conducted three times. Disease symptoms, similar to those in the field, were observed on the inoculated plants two weeks after inoculation, and L. theobromae was 100% reisolated from the inoculated plants. The control plants remained symptomless, and reisolations were unsuccessful. These results consistent with Koch’s postulates. L. theobromae (Lima et al. 1997) and L. hormozganensis (Fábio et al. 2018) had been reported to cause stem rot on castor bean in Brazil, but whether L. theobromae caused the branch dieback on castor bean in China has not been reported yet. Thus, this study is the first report of L. theobromae causing the branch dieback on castor bean in Zhanjiang, China. This study provides an important reference for the control of the disease.

Download Full-text

First Report of Anthracnose Caused by Colletotrichum fructicola on Loropetalum chinense in China

Plant Disease ◽

10.1094/pdis-07-21-1531-pdn ◽

2021 ◽

Author(s):

Ling Qiu ◽

Jingwen Liu ◽

Weigang Kuang ◽

RuQiang Cui ◽

Lianhu Zhang ◽

...

Keyword(s):

Phylogenetic Analyses ◽

Morphological Characteristics ◽

Molecular Data ◽

Jiangxi Province ◽

Conidial Suspension ◽

Sterile Water ◽

Mountain Area ◽

First Report ◽

Landscape Plant ◽

Medicinal Value

Loropetalum chinense Oliv. (Hamamelidaceae), an evergreen shrub or small tree, is widely used as a bonsai and landscape plant because of its aesthetic value. In addition, it has medicinal value, its leaves, flowers and roots can be used to treat diarrhea, coughs, hemorrhaging and burn (Zhang et al. 2013). In October 2020, leaf spot symptoms were observed on L. chinense distributed in Meiling Scenic Spot of Nanchang, Jiangxi Province, China (28.78°N, 115.83°E). We surveyed about 500 m2 of the mountain area which holds about 60 trees of L. chinense, with an incidence up to 20%. Initially, small gray-brown spots with dark brown edges appeared on the leaf surface, becoming large circular or irregular brown necrotic lesions over time. To isolate the pathogen, ten leaves of infected tissues were cut into 4 mm2 pieces, and surface disinfected with 75% ethanol for 30s and 1% hypochlorite for 1 min, rinsed three times with sterile water, plated on potato dextrose agar (PDA), and incubated at 25°C in the dark for 5 to 7 days. Five isolates with similar morphological characteristics were obtained. Conidia were hyaline, aseptate, smooth-walled, cylindrical with obtuse to slightly rounded ends, and their dimensions varied from 8.57 to 15.80 × 1.56 to 4.65 μm (n = 20). The morphological characteristics of the isolates matched the descriptions of Colletotrichum gloeosporioides species complex (Cai et al. 2009; Weir et al. 2012; Liu et al. 2015). For molecular identification, two representative isolates (JAUCC L003 and JAUCC L004) were selected for genomic DNA extraction, and the internal transcribed spacer (ITS), partial calmodulin (CAL), chitin synthase (CHS-1), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and actin (ACT) were amplified, using primer pairs ITS1/ITS4, CL1C/CL2C, CHS-79F/CHS-345R, GDF1/GDR1, and ACT-512F/ACT-783R, respectively (White et al. 1990; Weir et al. 2012; Yang et al.2020). The sequenced loci (GenBank accession nos. ITS: MZ054401, MZ054400; CAL: MZ056750, MZ056754; CHS-1: MZ056751, MZ056755; GAPDH: MZ056752, MZ056756; ACT: MZ056753, MZ056757) exhibited up to 99% homology with corresponding sequences of C. fructicola Prihast., L. Cai & K.D. Hyde strains (GenBank accession nos. LC494271, MN525833, MN525854, MN525875 and MN525814). Concatenated sequences of the five genes were used to conduct a phylogenetic analysis using Maximum-Likelihood (ML) method in MEGA7. The isolates were identified as C. fructicola based on morphology and a multigene phylogenetic analyses. Pathogenicity of one representative isolate (JAUCC L003) was tested indoor by inoculating the top wounded leaves of six healthy L. chinense plants, rather than inoculating unwounded leaves due to the low incidence. Three leaves from each of three plants were punctured with flamed needles and sprayed with a conidial suspension (1 × 106 conidia/ml), and three leaves from each of other three plants were wounded and inoculated with mycelial plugs (5 × 5 mm3). Mock inoculations were used as controls with sterile water and PDA plugs on three leaves each. Treated plants were incubated in an artificial climate box at 25 °C, 90% relative humidity, with a 12-h photoperiod. All leaves inoculated with conidial suspension and mycelial plugs produced similar symptoms as described above 10 days postinoculation, whereas the mock inoculated plants remained asymptomatic. The fungus isolated from inoculated leaves was identical to the original pathogen on account of morphological and molecular data, confirming Koch's postulates, but not from the mock inoculated plants. Anthracnose disease caused by C. fructicola has been reported affecting numerous plants worldwide, including cotton, coffea, grape, citrus, mango, apple, pear, and cassava, among others (Guarnaccia et al. 2017, Oliveira et al. 2018). To our knowledge, this is the first report of C. fructicola causing anthracnose on L. chinense in China. This disease is significant concern in horticulture due to its impact on the aesthetics of ornamentals used in landscape plantings.

Download Full-text

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.

Download Full-text

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.

Download Full-text

First Report of Phytophthora drechsleri Associated with Stem and Foliar Blight of Gynura bicolor in Taiwan

Plant Disease ◽

10.1094/pdis-12-10-0931 ◽

2011 ◽

Vol 95 (7) ◽

pp. 874-874 ◽

Cited By ~ 1

Author(s):

Y. M. Shen ◽

C. H. Chao ◽

H. L. Liu

Keyword(s):

Disease Incidence ◽

Morphological Characteristics ◽

Hyphal Growth ◽

Pathogenicity Test ◽

Distilled Water ◽

First Report ◽

Foliar Blight ◽

Dual Cultures ◽

Phytophthora Drechsleri ◽

Gynura Bicolor

Gynura bicolor (Roxb. ex Willd.) DC., known as Okinawa spinach or hong-feng-cai, is a commonly consumed vegetable in Asian countries. In May 2010, plants with blight and wilt symptoms were observed in commercial vegetable farms in Changhua, Taiwan. Light brown-to-black blight lesions developed from the top of the stems to the petioles and extended to the base of the leaves. Severely infected plants declined and eventually died. Disease incidence was approximately 20%. Samples of symptomatic tissues were surface sterilized in 0.6% NaOCl and plated on water agar. A Phytophthora sp. was consistently isolated and further plated on 10% unclarified V8 juice agar, with daily radial growths of 7.6, 8.6, 5.7, and 2.4 mm at 25, 30, 35, and 37°C, respectively. Four replicates were measured for each temperature. No hyphal growth was observed at 39°C. Intercalary hyphal swellings and proliferating sporangia were produced in culture plates flooded with sterile distilled water. Sporangia were nonpapillate, obpyriform to ellipsoid, base tapered or rounded, and 43.3 (27.5 to 59.3) × 27.6 (18.5 to 36.3) μm. Clamydospores and oospores were not observed. Oospores were present in dual cultures with an isolate of P. nicotianae (p731) (1) A2 mating type, indicating that the isolate was heterothallic. A portion of the internal transcribed spacer sequence was deposited in GenBank (Accession No. HQ717146). The sequence was 99% identical to that of P. drechsleri SCRP232 (ATCC46724) (3), a type isolate of the species. The pathogen was identified as P. drechsleri Tucker based on temperature growth, morphological characteristics, and ITS sequence homology (3). To evaluate pathogenicity, the isolated P. drechsleri was inoculated on greenhouse-potted G. bicolor plants. Inoculum was obtained by grinding two dishes of the pathogen cultured on potato dextrose agar (PDA) with sterile distilled water in a blender. After filtering through a gauze layer, the filtrate was aliquoted to 240 ml. The inoculum (approximately 180 sporangia/ml) was sprayed on 24 plants of G. bicolor. An equal number of plants treated with sterile PDA processed in the same way served as controls. After 1 week, incubation at an average temperature of 29°C, blight and wilt symptoms similar to those observed in the fields appeared on 12 inoculated plants. The pathogen was reisolated from the lesions of diseased stems and leaves, fulfilling Koch's postulates. The controls remained symptomless. The pathogenicity test was repeated once with similar results. G. bicolor in Taiwan has been recorded to be infected by P. cryptogea (1,2), a species that resembles P. drechsleri. The recorded isolates of P. cryptogea did not have a maximal growth temperature at or above 35°C (1,2), a distinctive characteristic to discriminate between the two species (3). To our knowledge, this is the first report of P. drechsleri being associated with stem and foliar blight of G. bicolor. References: (1) P. J. Ann. Plant Pathol. Bull. 5:146, 1996. (2) H. H. Ho et al. The Genus Phytophthora in Taiwan. Institute of Botany, Academia Sinica, Taipei, 1995. (3) R. Mostowfizadeh-Ghalamfarsa et al. Fungal Biol. 114:325, 2010.

Download Full-text

First Report of Powdery Mildew Caused by Golovinomyces biocellatus on Agastache rugosa in Korea

Plant Disease ◽

10.1094/pdis-03-14-0298-pdn ◽

2014 ◽

Vol 98 (9) ◽

pp. 1278-1278 ◽

Cited By ~ 1

Author(s):

S. E. Cho ◽

J. H. Park ◽

S. H. Hong ◽

I. Y. Choi ◽

H. D. Shin

Keyword(s):

Powdery Mildew ◽

Severe Disease ◽

Morphological Characteristics ◽

Control Measures ◽

Control Treatment ◽

Width Ratio ◽

Korean Isolate ◽

Pathogenicity Test ◽

Agastache Rugosa ◽

First Report

Agastache rugosa (Fisch. & C.A. Mey.) Kuntze, known as Korean mint, is an aromatic plant in the Lamiaceae. It is widely distributed in East Asian countries and is used as a Chinese traditional medicine. In Korea, fresh leaves are commonly added to fish soups and stews (3). In November 2008, several dozen Korean mints plants growing outdoors in Gimhae City, Korea, were found to be severely infected with a powdery mildew. The same symptoms had been observed in Korean mint plots in Busan and Miryang cities from 2008 to 2013. Symptoms first appeared as thin white colonies, which subsequently developed into abundant hyphal growth on stems and both sides of the leaves. Severe disease pressure caused withering and senescence of the leaves. Voucher specimens (n = 5) were deposited in the Korea University Herbarium (KUS). Appressoria on the mycelium were nipple-shaped or nearly absent. Conidiophores were 105 to 188 × 10 to 13 μm and produced 2 to 4 immature conidia in chains with a sinuate outline, followed by 2 to 3 cells. Foot-cells of the conidiophores were straight, cylindrical, slightly constricted at the base, and 37 to 58 μm long. Conidia were hyaline, ellipsoid to barrel-shaped, measured 25 to 40 × 15 to 23 μm (length/width ratio = 1.4 to 2.1), lacked distinct fibrosin bodies, and showed reticulate wrinkling of the outer walls. Primary conidia were obconically rounded at the apex and subtruncate at the base. Germ tubes were produced at the perihilar position of conidia. No chasmothecia were observed. The structures described above were typical of the Oidium subgenus Reticuloidium anamorph of the genus Golovinomyces. The measurements and morphological characteristics were compatible with those of G. biocellatus (Ehrenb.) V.P. Heluta (1). To confirm the identification, molecular analysis of the sequence of the internal transcribed spacer (ITS) region of ribosomal DNA (rDNA) of isolate KUS-F27200 was conducted. The complete ITS rDNA sequence was amplified using primers ITS5 and P3 (4). The resulting 514-bp sequence was deposited in GenBank (Accession No. KJ585415). A GenBank BLAST search of the Korean isolate sequence showed >99% similarity with the ITS sequence of many G. biocellatus isolates on plants in the Lamiaceae (e.g., Accession Nos. AB307669, AB769437, and JQ340358). Pathogenicity was confirmed by gently pressing diseased leaf onto leaves of five healthy, potted Korean mint plants. Five non-inoculated plants served as a control treatment. Inoculated plants developed symptoms after 7 days, whereas the control plants remained symptomless. The fungus present on inoculated plants was identical morphologically to that observed on the original diseased plants. The pathogenicity test was repeated with identical results. A powdery mildew on A. rugosa caused by G. biocellatus was reported from Romania (2). To our knowledge, this is the first report of powdery mildew caused by G. biocellatus on A. rugosa in Korea. The plant is mostly grown using organic farming methods with limited chemical control options. Therefore, alternative control measures should be considered. References: (1) U. Braun and R. T. A. Cook. Taxonomic Manual of the Erysiphales (Powdery Mildews), CBS Biodiversity Series No. 11. CBS, Utrecht, 2012. (2) D. F. Farr and A. Y. Rossman. Fungal Databases. Syst. Mycol. Microbiol. Lab., online publication, USDA ARS, retrieved 17 February 2014. (3) T. H. Kim et al. J. Sci. Food Agric. 81:569, 2001. (4) S. Takamatsu et al. Mycol. Res. 113:117, 2009.

Download Full-text

First Report of Phytophthora ramorum on Viburnum bodnantense in Belgium

Plant Disease ◽

10.1094/pdis.2003.87.2.203c ◽

2003 ◽

Vol 87 (2) ◽

pp. 203-203 ◽

Cited By ~ 11

Author(s):

D. De Merlier ◽

A. Chandelier ◽

M. Cavelier

Keyword(s):

The Netherlands ◽

Plant Protection ◽

Morphological Characteristics ◽

Pcr Primers ◽

Selective Medium ◽

Phytophthora Species ◽

Phytophthora Ramorum ◽

Pathogenicity Test ◽

First Report ◽

Root Necrosis

In the past decade, a new Phytophthora species inducing shoot canker on Rhododendron and dieback of Viburnum has been observed in Europe, mainly in Germany and the Netherlands, and California. This new pathogen has been named Phytophthora ramorum (3). In May 2002, a diseased Viburnum plant (Viburnum bodnantense) from the Plant Protection Service (Ministry of Agriculture, Belgium) was submitted to our laboratory for diagnosis. Symptoms included wilting, leaves turning from green to brown, discolored vascular tissues, and root necrosis. The plant came from a Belgian ornamental nursery that obtained supplies of stock plants from the Netherlands. Pieces of necrotic root tissue were excised, surface-disinfected, and transferred aseptically to a Phytophthora selective medium. P. ramorum was identified based on morphological characteristics, including the production of numerous, thin-walled chlamydospores (25 to 70 µm in diameter, average 43 µm) and deciduous, semi-papillate sporangia arranged in clusters. Radial growth after 6 days at 20°C on V8 juice agar was 2.8 mm per day. Random amplified microsatellite markers (RAMS) (2) from the total genomic DNA of the Belgian strain (CBS 110901) were similar to those of P. ramorum reference strains (CBS 101330, CBS 101332, and CBS 101554). Using PCR primers specific for P. ramorum, the identification was confirmed by W. A. Man in't Veld (Plantenziektenkundige Dienst, Wageningen, the Netherlands) (1). A pathogenicity test was carried out on three sterile cuttings of Rhododendron catawbiense (3). Brown lesions were observed on the inoculated cuttings after 6 to 7 days. None of the three uninoculated cuttings showed symptoms of infection. P. ramorum was reisolated from lesion margins on the inoculated cuttings. To our knowledge, this is the first report of the fungus from Belgium. Since our initial observation, we have found P. ramorum in other Belgian nurseries on R. yakusimanum. References: (1) M. Garbelotto et al. US For. Ser. Gen. Tech. Rep. PSW-GRT. 184:765, 2002. (2) J. Hantula et al. Mycol. Res. 101:565, 1997. (3) S. Werres et al. Mycol. Res. 105:1155, 2001.

Download Full-text