First Report of Citrus Root Rot Caused by Phytophthora palmivora in Egypt

During spring-summer 2009, a survey was conducted to determine the species of Phytophthora present in citrus nurseries in Egypt. A total of 300 samples of soil and fibrous roots were collected from the rhizosphere of symptomatic Volkameriana lemon (Citrus volkameriana Tan. & Pasq.) plants growing in Delta (Benha-Qalyubia) and a desert (Cairo/Alexandria desert road) citrus nurseries. Plants showed various symptoms. Canopies of affected plants showed few and yellowish leaves, a general stunted growth, no new vegetation, and sometimes sudden desiccation; the root system showed few dark brown feeder roots, no new yellow-white apexes, and a fibrous appearance of the rootlets due to disintegration of the cortical bark but not of the xylem. Collected rootlets and soil were plated in Petri dishes containing a selective medium for the oomycete Phytophthora (2) and incubated for 3 to 6 days at 19 ± 1°C as described by Ippolito et al. (1). Pure cultures were obtained by single-hypha transfers and the isolates were identified as Phytophthora palmivora (Butler) Butler on the basis of morphological and cultural characteristics (3). Isolates formed stoloniferous colonies on potato dextrose agar (PDA) and grew between 10 and 30°C, with the optimum at 25°C. On V8 juice agar, they showed a highly fluffy pattern and produced terminal and intercalary globose chlamydospores. Sporangia were papillate, elliptical (45 to 51 × 29 to 35 μm; length/breadth ratio of 1.3:1.8), and were caducous with short pedicel. All isolates were A2 mating type, forming spherical oogonia and amphigynous antheridia in dual cultures with reference P. palmivora isolate of A1 mating type. Identification of the isolates was further confirmed by amplification and sequencing of the internal transcribed spacer (ITS) region using the universal primers ITS4 and ITS6. BLASTn analysis of ITS sequences (GenBank Accession No. HE583183) showed 99% homology with P. palmivora isolates available in GenBank. Pathogenicity tests for P. palmivora were conducted by inoculating three groups of ten 6-month-old Volkameriana lemon plants, transplanted into 1.4 liter pots with growing medium artificially inoculated at the rate of 1% (v/v) of P. palmivora inoculum produced according to Yaseen (4). Ten uninoculated plants served as a control. Two months after the inoculation, plants were analyzed for canopy symptoms and the presence of pathogen in feeder roots. More than 50% of inoculated plants showed foliage symptoms and extensive decay of feeder roots. Colonies of Phytophthora were recovered from necrotic rootlets and identified as P. palmivora, fulfilling Koch's postulates. To the best of our knowledge, this is the first report of P. palmivora as a pathogen to citrus plants in the Egyptian nurseries. P. palmivora should be considered a potential threat to the Egyptian citrus industry since it may negatively influence the nurseries and orchards production in the future. References: (1) A. Ippolito, V. De Cicco, and M. Salerno. Rivista di Patologia Vegetale 2:57, 1992. (2) H. Masago, M. Yoshikawa, M. Fukada, and N. Nakanishi. Phytopathology 67:425, 1977. (3) D. J. Stamps. Revised tabular key to the species of Phytophthora. CAB International Mycological Institute, Kew, Surrey, 1990. (4) T. Yaseen. Molecular diagnosis and biological control of Phytophthora-citrus root rot. PhD thesis. University of Bari, Italy, 2004.

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First Report of Phytophthora palmivora on Coronilla valentina subsp. glauca in Italy

Plant Disease ◽

10.1094/pdis.2002.86.3.327b ◽

2002 ◽

Vol 86 (3) ◽

pp. 327-327

Author(s):

S. O. Cacciola ◽

A. Pane ◽

S. Davino ◽

F. Raudino

Keyword(s):

Mating Type ◽

Irrigation System ◽

Field Capacity ◽

Industrial Area ◽

Selective Medium ◽

Phytophthora Palmivora ◽

Dual Culture ◽

Trickle Irrigation ◽

First Report ◽

Pure Cultures

The genus Coronilla L. (family Fabaceae), which includes several species native to central and southern Europe, such as C. varia L. (axseed or crown-vetch), C. emerus (scorpion senna), and C. valentina L., is used in Italy as a landscape shrub or potted ornamental plant. During the summer of 2001, 80% of approximately 10,000 1-year-old plants of C. valentina subsp. glauca (L.) Batt. used to landscape an industrial area in the Caltanissetta Province (Sicily) showed symptoms of dieback associated with basal stem and root rot. Plants had been transplanted from pots in April and watered using a trickle irrigation system. A species of Phytophthora was isolated consistently from rotted roots and basal stems using BNPRAH selective medium (3). Pure cultures of this fungus were obtained by single-hypha transfers. Ten isolates, each originating from a single plant, were identified as P. palmivora (Butler) Butler on the basis of morphological and cultural characters as described by Erwin and Ribeiro (1). On solid media, including potato dextrose agar, cornmeal agar, and V8-juice agar, all the isolates produced elliptical to ovoid, papillate sporangia with a mean length/breadth ratio of 1.8. Sporangia were caducous with a short pedicel (mean pedicel length = 5 µm) and a conspicuous basal plug. Mating type was determined on V8 agar in dual culture with mating type A1 and A2 of reference isolates of P. nicotianae and P. palmivora. All isolates were heterothallic and produced oogonia and oospores only with reference isolates of the A2 mating type. Antheridia were amphigynous. Electrophoresis of mycelial proteins on polyacrylamide slab gel confirmed that all isolates were pure cultures and belonged to the same species. Koch's postulates were fulfilled using 6-month-old C. valentina subsp. glauca plants that were transplanted into pots filled with soil artificially inoculated with chlamydospores (50 chlamydospores per gram of soil) produced in submerged axenic cultures (2). The plants were maintained in a glasshouse at temperatures ranging from 18 to 28°C, and the pots were watered to field capacity once a week. One month after transplanting, 70% of plants showed dieback symptoms, while control plants, which were grown in pots containing noninoculated soil, remained healthy. The pathogen was reisolated from roots and basal stems of symptomatic plants. These results demonstrate that P. palmivora is the causal agent of dieback of C. valentina subsp. glauca plants. High temperatures in summer and waterlogging of soil due to excess irrigation water could have enhanced disease development. To our knowledge, this is the first report of P. palmivora on a species of Coronilla. P. palmivora is an exotic pathogen, but it is becoming widespread in Italy, where it has been reported from various regions on different hosts, including cyclamen, English ivy, palms, Pittosporum, and olive. References: (1) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society. St Paul, MN, 1996. (2) J. Y Kadooka and W. H. Ko. Phytopathology 63:559, 1973. (3) H. Masago et al. Phytopathology 67:425, 1977.

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First Report of Phytophthora tentaculata Causing Root and Stem Rot of Oregano in Italy

Plant Disease ◽

10.1094/pdis-93-8-0843b ◽

2009 ◽

Vol 93 (8) ◽

pp. 843-843 ◽

Cited By ~ 2

Author(s):

P. Martini ◽

A. Pane ◽

F. Raudino ◽

A. Chimento ◽

S. Scibetta ◽

...

Keyword(s):

Dna Amplification ◽

Its Region ◽

Selective Medium ◽

Stem Rot ◽

Universal Primers ◽

Basal Stem Rot ◽

First Report ◽

Soilborne Disease ◽

Potted Plants ◽

Morphological Criteria

Oregano (Origanum vulgare L.; Lamiaceae) is cultivated for culinary and medicinal purposes and as an ornamental. In October of 2007, 1- to 2-year-old potted plants of oregano showed symptoms of decline associated with root and basal stem rot in a nursery in Liguria (northern Italy) that produces 1 million to 1.5 million potted aromatic plants per year. Aboveground symptoms included leaf russeting and chlorosis, wilt, defoliation and dieback of twigs, browning of the basal stem, and subsequent collapse of the entire plant. Approximately 80% of the plants died within 30 days after the appearance of the first symptoms on the canopy. Approximately 20% of a stock of 30,000 oregano plants was affected. Stocks of other aromatic species, such as mint, lavender, rosemary, and sage, appeared healthy. A Phytophthora species was consistently isolated from symptomatic stems and roots of oregano plants on BNPRAH selective medium (2). Ten pure cultures were obtained by single-hypha transfers, and the species was identified as Phytophthora tentaculata Kröber & Marwitz by morphological criteria and sequencing of the internal transcribed spacer (ITS) region of rDNA using the ITS 4 and ITS 6 universal primers for DNA amplification. Isolates from oregano formed stoloniferous colonies with arachnoid mycelium on potato dextrose agar and had a growth rate of 2 to 3 mm per day at 24°C with optimum, minimum, and maximum temperatures of 24, 8, and 34°C, respectively. Sporangia formed in soil extract solution and were papillate and spherical or ovoid to obpyriform with a length/breadth ratio of 1.3:1. Few sporangia were caducous and all had a short pedicel (<5 μm). Hyphal swellings and chlamydospores were produced in sterile distilled water and corn meal agar, respectively. All isolates were homothallic and produced globose terminal oogonia (mean diameter of 34 μm) with one or occasionally two paragynous, monoclinous, or diclinous antheridia. Amphigynous antheridia were also observed. The sequence of the ITS region of the rDNA (GenBank No. FJ872545) of an isolate from oregano (IMI 395782) showed 99% similarity with sequences of two reference isolates of P. tentaculata (Accession Nos. AF266775 and AY881001). To test for pathogenicity, the exposed root crowns of 10 6-month-old potted plants of oregano were drench inoculated with 10 ml of a suspension of 2 × 104 zoospores/ml of isolate IMI 395782. Sterile water was pipetted onto the roots of 10 control plants. All plants were maintained in 100% humidity at 22 to 24°C in a greenhouse under natural light and watered once a week. Within 3 weeks after inoculation, all inoculated plants developed symptoms identical to those observed in the nursery and died within 30 to 40 days after the appearance of the first symptoms. Control plants remained healthy. P. tentaculata was reisolated solely from symptomatic plants. P. tentaculata has been reported previously on several herbaceous ornamental plants (1,3). However, to our knowledge, this is the first report of this species on O. vulgare. Root and basal stem rot caused by P. tentaculata is the most serious soilborne disease of oregano reported in Italy so far. References: (1) G. Cristinzio et al. Inf. Fitopatol. 2:28, 2006. (2) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society, St. Paul, MN, 1996. (3) H. Kröber and R. Marwitz. Z. Pflanzenkr. Pflanzenschutz 100:250, 1993.

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First Report of a Root Rot Caused by Phytophthora palmivora on Lavandula angustifolia in Turkey

Plant Disease ◽

10.1094/pdis-04-11-0306 ◽

2011 ◽

Vol 95 (8) ◽

pp. 1035-1035 ◽

Cited By ~ 5

Author(s):

S. Dervis ◽

M. Arslan ◽

C. U. Serce ◽

S. Soylu ◽

I. Uremis

Keyword(s):

Root Rot ◽

Peat Soil ◽

Its Region ◽

Phytophthora Palmivora ◽

Width Ratio ◽

Lavandula Angustifolia ◽

Crop Species ◽

First Report ◽

Initial Symptoms ◽

Wide Range

English Lavender (Lavandula angustifolia Mill.) has been considered an alternative crop to tobacco in Hatay Province of Turkey because of its great production potential. As a new, nonnative crop, diseases and pests of lavender are not well known in the region. In summer 2010, root rot symptoms were observed with an average incidence of 45% in a 2-year-old lavender nursery in Hatay. Initial symptoms of chlorosis and wilting were followed by progressive death of the plants starting at the shoot tips. An oomycetous species was isolated consistently from the stems and roots of diseased plants on potato dextrose agar (PDA) amended with several fungicides and antibiotics. The culture of the single-zoospore isolate produced arachnoid growth on PDA. Chlamydospores of the isolate were approximately 35.0 μm in diameter. The isolate produced papillate, caduceus, hyaline sporangia in different shapes ranging from spherical to ellipsoidal. Sporangia with short pedicels (5 μm) were 35.0 to 57.5 × 27.5 to 42.5 μm with a length/width ratio of 1.2 to 1.8. On the basis of symptoms and morphology of the organism, the pathogen was identified as Phytophthora palmivora (E.J. Butler) E.J. Butler (3). Identification of the isolate was also confirmed by comparison of the sequence of the nuclear ribosomal internal transcribed spacer (ITS) region with reference isolates. The ITS region of rDNA was amplified by PCR with primers ITS1/ITS4 and sequenced (GenBank Accession No. JF777117). BLAST analysis of the sequence obtained showed a 99 to 100% homology with P. palmivora. Pathogenicity tests were performed on 12 greenhouse-grown 2-year-old lavender plants in 2-liter pots containing a steamed sand/peat/soil mixture. After rooting, the plants were inoculated by placing mycelial plugs from a 1-week-old culture of the isolate into an incision made at the base of each plant. Control plants were treated with plugs of sterile PDA. Inoculated plants were kept at 27°C for 5 weeks. Similar symptoms developed on the inoculated plants within 4 weeks after inoculation. P. palmivora was consistently reisolated from symptomatic plants. No symptoms developed on control plants. P. palmivora attacks a wide range of crop species including lavenders (1,2,4). To our knowledge, this is the first report of a root rot caused by P. palmivora, a new pathogen of lavender in Turkey. References: (1) S. Davino et al. Plant Dis. 86:561, 2002. (2) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society, St Paul, MN, 1996. (3) D. J. Stamps. C.M.I. Descr. Fungi Bact. 831:1, 1985. (4) G. A. Torres et al. Plant Dis. 94:1163, 2010.

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First report of Mycoleptodiscus terrestris causing root rot of soybean in Indiana

Plant Disease ◽

10.1094/pdis-09-20-2023-pdn ◽

2020 ◽

Author(s):

Christopher Detranaltes ◽

Guohong Cai

Keyword(s):

Root Rot ◽

Biological Control Agent ◽

Lateral Roots ◽

Its Region ◽

Selective Medium ◽

Internal Transcribed Spacers ◽

Root Tissue ◽

Pathogenicity Test ◽

First Report ◽

Soybean Seedlings

During the summers in 2019 and 2020, 137 soybean (Glycine max (L.) Merr) seedlings (V1-V3 stage) showing stunting, delayed emergence, and/or crown lesions were collected at Purdue’s Agronomy Center for Research and Education in West Lafayette, Indiana. Four seedlings were stunted with reddish-brown girdled lesions along the hypocotyl and crown, rotted tap and lateral roots, and brown discoloration of the cortex and vascular tissues. Four fungal isolates (AC4, AC58, AC96, and AC127) were recovered by plating surface-sterilized symptomatic root tissue onto water agar plates and incubating on the benchtop until mycelia emerged. The growing hyphal tips were transferred to the semi-selective medium DCPA (Andrews and Pitt 1986). On potato dextrose agar, the fungal colonies developed olivaceous green mycelia which melanized into a mat of black microsclerotia with time and no conidia were observed. On 1.5% water agar plates amended with twice autoclaved soybean leaf and root tissue collected from flowering soybean plants, conidia were formed in sporodochia in darkness at 28 οC within one week. Conidia were 1-2 septate, cylindrical with two setae on either end, and measured 20.8 to 26.4 x 4 to 5.6 μm (average 23.9 x 4.7 μm, n=20). The morphological characters matched with the description of Mycoleptodiscus terrestris (Gerd.) Ostaz (Gerdemann 1953). Species identification was further confirmed by sequencing the internal transcribed spacers (ITS) region of rDNA amplified by ITS1 and ITS4 primers (White et al. 1990) and the translation elongation factor 1 alpha (TEF1-α) gene using 983F and 1567R primers with annealing temperature at 53 ○C (Rehner and Buckley 2005). The sequences were deposited in GenBank under the following accession numbers: ITS: MW002684, MT998441, MW010258, and MW010260; and TEF1-α: MW015941-MW015944. The GenBank BLAST searches revealed 100% identity in the ITS region (accession NR_145373.1) and 99.75% identity in the TEF1-α region (MK495977.1) to M. terrestris. Pathogenicity test was conducted on soybean seedlings (cv. Williams) at V1 growth stage using a root dip assay. Isolate AC58 was grown in a modified cotton seed meal broth (CSMB) to produce microsclerotia as inoculum (Gray 1978; Shearer and Jackson 2006). Microsclerotia concentration was measured using a hemocytometer and adjusted to 1.5 x 104 per ml. Five soybean seedlings each were dipped into inoculum or sterile CSMB for 30 minutes then planted individually in vermiculite-filled Styrofoam cups placed on flooded trays in 16-hr photoperiod light racks at room temperature. Seven days after inoculation, all inoculated plants were visibly stunted with root and crown symptoms identical to field symptoms while all controls were healthy. M. terrestris was successfully re-isolated from inoculated plants, but not from the controls, and identified by morphology and sequencing as above. M. terrestris has been previously reported causing root rot of soybean in Illinois (Gray 1978) and Wisconsin (Smith et al. 1998). To our knowledge, this is the first report of M. terrestris infecting soybean in Indiana. Increased geographic distribution of this pathogen warrants more attention for its control. M. terrestris has been proposed as a biological control agent against multiple aquatic weeds (Verma and Charudattan 1993; Shearer and Jackson 2006). Introduction of this fungus into soybean production regions should be avoided.

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Bud and Root Rot of Windmill Palm (Trachycarpus fortunei) Caused by Simultaneous Infections of Phytophthora palmivora and P. nicotianae in Sicily

Plant Disease ◽

10.1094/pdis-11-10-0823 ◽

2011 ◽

Vol 95 (6) ◽

pp. 769-769 ◽

Cited By ~ 5

Author(s):

S. O. Cacciola ◽

A. Pane ◽

R. Faedda ◽

C. Rizza ◽

F. Badalà ◽

...

Keyword(s):

Root Rot ◽

Rhizosphere Soil ◽

Sprinkler Irrigation ◽

Its Region ◽

Selective Medium ◽

Phytophthora Species ◽

Phytophthora Palmivora ◽

Infested Soil ◽

Tissue Samples ◽

Reference Isolate

In June 2009 in a commercial nursery in eastern Sicily (Italy), 3-year-old potted windmill palms (Trachycarpus fortunei (Hooker) H. Wendl.) showed a decline in growth, wilt, droop, and basal rot of the youngest leaves. The rot progressed inward and killed the bud. Initially, older leaves remained green but eventually the entire plant collapsed. Root rot was consistently associated with aboveground symptoms. Two Phytophthora species were consistently isolated from the petiole base, heart, roots, and rhizosphere soil of symptomatic plants on a selective medium (2) and occasionally recovered from roots and rhizosphere soil of asymptomatic plants. Pure cultures were obtained by single-hypha transfers and the two species were identified on the basis of morphological and molecular characters as Phytophthora palmivora and P. nicotianae. Both species were recovered from all symptomatic plants. From multiple tissue samples per plant, we recovered either or both species. On potato dextrose agar (PDA), P. palmivora isolates grew between 10 and 35°C, with the optimum at 27°C. On V8 juice agar, they produced elliptical to ovoid, papillate, caducous sporangia (32 to 78 × 23 to 39 μm) with a mean length/breadth (l/b) ratio of 1.8:1 and a short pedicel (mean pedicel length = 5 μm). Isolates of P. nicotianae produced arachnoid colonies on PDA, grew at 37°C but did not grow at 40°C. Sporangia (29 to 55 × 23 to 45 μm) were spherical to ovoid (l/b ratio 1.3:1), papillate and often bipapillate, and noncaducous. Isolates of both species produced amphigynous antheridia and oogonia only when paired with reference isolates of P. nicotianae of the A2 mating type. The internal transcribed spacer (ITS) region of rDNA of two isolates of P. palmivora (IMI 398987 and IMI 398988) and an isolate of P. nicotianae (IMI 398989) from T. fortunei was amplified with primers ITS6/ITS4 and sequenced (1). Blast analysis of the sequences of isolates IMI 398987 and IMI 398988 (GenBank Accession Nos. HQ596556 and HQ596558) showed 99% homology with the sequence of two reference isolates of P. palmivora (GQ398157.1 and GU258862), while the sequence of isolate IMI 398989 (HQ596557) showed 99% homology with a reference isolate of P. nicotianae (EU331089.1). Pathogenicity of isolates IMI 398987 and IMI 398989 was proved by inoculating separately each isolate on 1-year-old potted plants of T. fortunei (10 plants per isolate). A zoospores suspension (2 × 104 zoospores/ml) was pipetted onto the petiole base of the three central leaves (200 μl per leaf) of each plant. Sterile water was used for control plants. All plants were incubated at 25 ± 2°C with 100% humidity for 48 h and then maintained in a greenhouse at 24 to 28°C. Within 3 weeks, all inoculated plants showed symptoms of bud rot. Control plants remained healthy. P. palmivora and P. nicotianae were reisolated only from inoculated plants. Bud rot of palms caused by P. palmivora was reported previously in Italy (3). However, to our knowledge, this is the first report of simultaneous infections of P. palmivora and P. nicotianae as causal agents of this disease. Outbreak of bud rot may have been favored by overhead sprinkler irrigation. The recovery of P. palmivora and P. nicotianae from rhizosphere soil and roots of asymptomatic plants suggests infested soil was the primary inoculum source. References: (1) D. E. L. Cooke et al. Fungal Genet. Biol. 30:17, 2000. (2) H. Masago et al. Phytopathology 67:425, 1977. (3) A. Pane et al. Plant Dis. 91:1059, 2007.

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First Report of Phytophthora palmivora Causing Root Rot of Cassava in China

Plant Disease ◽

10.1094/pdis-09-11-0780-pdn ◽

2012 ◽

Vol 96 (7) ◽

pp. 1072-1072 ◽

Cited By ~ 5

Author(s):

H. Guo ◽

C.-P. Li ◽

T. Shi ◽

C.-J. Fan ◽

G.-X. Huang

Keyword(s):

Root Rot ◽

Morphological Characteristics ◽

Its Region ◽

Phytophthora Palmivora ◽

First Report ◽

Tuberous Roots ◽

Whole Plant ◽

Pure Cultures ◽

Short Pedicel ◽

Rot Disease

Cassava (Manihot esculenta) is an economically important crop grown widely in South China. Seventy percent of the cassava grown is used for starch and ethanol production and it has become the foundation of local food and bioenergy systems. In November 2010, a new root rot disease was found on cv. HuaNan205 from a cassava plantation in Danzhou, Hainan Province. Disease occurred on 30% or less of the plants. Initially, the upper leaves wilted at noon and recovered in the evening. Eventually, infected plants no longer recovered and the whole plant wilted and died. Root rot symptoms consisting of irregular brown patches occurred on the tuberous roots. Symptomatic root rot tissue was cut into 1-cm pieces, washed in distilled water, and soaked in a solution of 1% sodium hypochlorite for 3 min. A subsection was cut from each sterilized piece, placed on a plate of V8 agar medium, and incubated at 28°C for 7 days. Pathogenicity was established by following Koch's postulates. In July 2011, 10 plants of cassava cv. HuaNan205 were selected from a disease-free plantation in Danzhou. The pathogen was cultivated on V8 agar at 28°C for 14 days. Four holes were established 15 cm from the base of the cassava plants. Five plants were inoculated with 100 mL of the mycelial suspension in each of the four spots and covered by soil. The other five plants were treated with sterile water as control. Plants were maintained for 4 months. All five of the inoculated plants wilted and two died, while the control plants grew normally. Symptoms similar to the original root lesions were observed on tuberous roots of inoculated plants, while only scars formed on tuberous roots of control plants. The pathogen was reisolated from the lesions of inoculated plants. Microscopic examination showed the sporangia as papillate and ovoid with the widest part close to the base. They were easily washed off and each detached sporangium contained a short pedicel 1.2 to 6.9 μm long, average 2.9 μm. Chlamydospores were readily observed on diseased roots and observed in pure cultures on V8 agar. Morphological characteristics of the specimen were similar to the descriptions for Phytophthora palmivora (2). Genomic DNA of this isolate was extracted with a cetyltrimethylammoniumbromide protocol (3) from mycelium and used as a template for amplification of the internal transcribed spacer (ITS) region of rDNA with primer pair ITS1/ITS4 (1). The sequence (GenBank Accession No. HE580279) exactly matched several sequences (e.g., GenBank Accession Nos. HQ237481.1, AY745750, and AY745751) of P. palmivora. To our knowledge, this is the first report of root rot caused by P. palmivora on cassava in China. References: (1) D. E. L. Cooke et al. Fungal Genet. Biol. 30:17, 2000. (2) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society, St. Paul, MN, 1996. (3) J. R. Xu et al. Genetics 143:175, 1996.

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First Report of Lily Blight and Wilt Caused by Fusarium tricinctum in China

Plant Disease ◽

10.1094/pdis-11-12-1010-pdn ◽

2013 ◽

Vol 97 (7) ◽

pp. 993-993 ◽

Cited By ~ 10

Author(s):

Y. Y. Li ◽

Y. J. Wang ◽

Z. K. Xie ◽

R. Y. Wang ◽

Y. Qiu ◽

...

Keyword(s):

Root Rot ◽

Elongation Factor ◽

Aerial Mycelium ◽

Its Region ◽

Universal Primers ◽

Conidial Suspension ◽

Root Tips ◽

First Report ◽

Horticultural Crops ◽

Blastn Analysis

Lily (Lilium spp.) is one of the most well-known horticultural crops, and plays an important economic role in China. In September 2011, wilted plants were observed on Lilium oriental hybrid cultivar ‘Sorbonne’ growing in Longde County, Ningxia Hui Autonomous Region, China. Disease symptoms included wilting, stem and root rot, brown spots of bulbs and then bulbs rotting and spalling from the basal disc, plus a progressive yellowing and defoliation of the leaves from the base. Diseased plants were sampled from fields. Small pieces of symptomatic bulbs, stems, and roots from 10 different plants were surface disinfected with 75% ethanol for 30 s, 3% sodium hypochlorite for 5 min, and then washed three times in sterilize distilled water. The tissues were placed onto Martin Agar (2) at 25°C for 7 days. Nine isolates with morphology similar to Fusarium were obtained from the diseased tissues. Isolates were transferred to potato dextrose agar (PDA) and carnation leaf agar (CLA) and incubated at 25°C. Seven were identified as Fusarium oxysporum and one was F. solani, which have been reported as pathogens of lily in China (1). The other isolate, when grown on PDA, rapidly produced dense, white aerial mycelium that became pink with age and formed red pigments in the medium. On CLA, macroconidia with three to five septate were abundant, relatively slender, and curved to lunate. Microconidia were abundant, oval or pyriform, and one to two celled. Chlamydospores were in chains with smooth exine. The rDNA internal transcribed spacer (ITS) region and a portion of the translation elongation factor 1-alpha (EF-1α) gene of the fungus were amplified, with universal primers ITS1/ITS4 and EF1/EF2 primers respectively (3) and sequenced. In addition, the β-tubulin gene (β-tub) of the fungus was amplified with modified primers Btu-F-F01 (5′-CAGACMGGTCAGTGCGTAA-3′) and Btu-F-R01 (5′-TCTTGGGGTCGAACATCTG-3′) (4). BLASTn analysis showed that the ITS sequences of the isolate (GenBank Accession No. JX989827) had 98.9% similarity with those of F. tricinctum (EF611092, JF776665, and HM776425) and the EF-1α sequences of the isolate (JX989828) had 98.1% similarity with those of F. tricinctum (EU744837 and JX397850). The β-tub sequences of the isolate (JX989829) had 99.0% similarity with those of F. tricinctum (EU490236 and AB587077). The isolate was tested for pathogenicity. Two-month-old ‘Sorbonne’ seedlings were inoculated by placing 5 ml of conidial suspension (about 106 conidia per ml) over the roots of plants in each pot. Control plants were treated with sterile water in the same way. Plants were placed in a greenhouse at 22 to 25°C with a 15-h photoperiod. There were eight plants per pot and three replicates for each treatment. After 3 weeks, 87.5% of the inoculated plants exhibited browning of the root tips, root rot, and yellowing of the leaves, while control plants were symptomless. The pathogen was reisolated from the infected roots and identified as F. tricinctum, thus fulfilling Koch's postulates. To our knowledge, this is the first report of Fusarium wilt of lily caused by F. tricinctum. This information will provide guidance for the control of lily wilt disease and add information useful for the production of lilies. References: (1) C. Li and J. J. Li. Acta Phytopathol. Sin. (in Chinese) 26:192, 1995. (2) J. P. Martin. Soil Sci. 38:215, 1950. (3) K. O'Donnell et al. Proc. Nat. Acad. Sci. U. S. A. 95:2044, 1998. (4) M. Watanabe et al. BMC Evol. Biol. 11:322. 2011.

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First Report of Mucor spp. Causing Root Rot of Radix pseudstellariae in Guizhou Province of China

Plant Disease ◽

10.1094/pdis-07-20-1634-pdn ◽

2020 ◽

Author(s):

Hongmiao Wu ◽

Jiachun Wu ◽

Feng Li ◽

Ling Zheng ◽

Jingkai Fan ◽

...

Keyword(s):

Root Rot ◽

Disease Incidence ◽

Acid Soils ◽

Its Region ◽

Significant Loss ◽

Day Length ◽

Guizhou Province ◽

First Report ◽

Chinese Medicinal Plants ◽

Branched Chains

Radix pseudostellariae L. is one of the most common and highly-prized Chinese medicinal plants with various pharmacological effects, and mainly produced in acid soils in the Guizhou and Fujian provinces of southwestern and southeastern China, respectively (Wu et al. 2020). However, consecutive monoculture of R. pseudostellariae results in severe root rot and decline in biomass and quality of underground tubers. Root tubers of R. pseudostellariae are typically planted in December and harvested in next June. Root rot commonly starts developing in May. The disease incidence of root rot was ranging from 37 to 46% in root portions and basal stem of R. pseudostellariae under the consecutive monoculture fields in Shibing County, Guizhou Province, China (108°12ʹE, 27°03ʹN) (Li et al. 2017). Severe root rot was observed in Shibing County in May 2018. Infected plants displayed curly, withered, and yellow leaves, blight, retarded growth, root rot, and yield losses. Abundant whitish mycelia were observed on roots and surrounding soil. Two fungal isolates, designated GZ20190123 and GZ20190124, were obtained from symptomatic roots cultured on potato dextrose agar (PDA). The optimum temperature range for growth of the two isolates was 25 to 30°C. The optimum pH range for the growth of GZ20190123 was 5 to 5.5, whereas GZ20190124 grew better between pH 5 to 8.5. The mean mycelial growth rates of GZ20190123 and GZ20190124 at 30°C were 2.1 and 1.5 cm/day, respectively. Conidia of the two isolates were ovoid or obclavate and were produced in single or branched chains. The internal transcribed spacer (ITS) region was amplified with primers ITS1 and ITS4 (White et al. 1990). The sequences were deposited in GenBank as accession No. MN726736 for GZ20190123 and MN726738 for GZ20190124. Sequence comparison revealed 99% (GZ20190123) and 97% (GZ20190124) identity with previously reported isolate xsd08071 of Mucor racemosus Bull. (accession No. FJ582639.1) and isolate BM3 of Mucor fragilis Bainier (accession No. MK910058.1), respectively, which was confirmed by phylogenetic analysis. The two isolates were tested for pathogenicity on R. pseudostellariae. Six roots of R. pseudostellariae were surface-sterilized with 75% ethanol and stab inoculated with mycelia using a sterile toothpick for each isolate. Sterile distilled water was stab inoculated to twelve roots to serve as the control. Treated roots were incubated in a greenhouse with 16 h day length [light intensity 146.5 μmol/(m2·s)] and day/night temperature 26°C/18°C. The inoculated roots showed the expected symptoms on roots and sprouts 7 days after inoculation, whereas the control roots with sprouts did not show any symptom. The fungi were re-isolated from the diseased roots and confirmed as expected M. racemosus or M. fragilis based on the ITS sequences, which satisfied Koch’s postulates. Thus, isolate GZ20190123 was identified as M. racemosus and GZ20190124 as M. fragilis. Previously, M. racemosus and M. fragilis have been reported as a pathogen on tomato (Kwon and Hong 2005) and grape (Ghuffar et al. 2018), respectively. To our knowledge, this is the first report of M. racemosus and M. fragilis causing root rot of R. pseudostellariae in southwestern China, where the disease could cause a significant loss to production of this important medicinal plant.

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First Report of Phytophthora megasperma Causing Decline and Death on Celtis australis in Italy

Plant Disease ◽

10.1094/pdis-05-14-0534-pdn ◽

2015 ◽

Vol 99 (1) ◽

pp. 155-155 ◽

Cited By ~ 2

Author(s):

L. Luongo ◽

A. Haegi ◽

M. Galli ◽

S. Berti ◽

S. Vitale ◽

...

Keyword(s):

Sensu Stricto ◽

Biological Species ◽

Selective Medium ◽

Phytophthora Species ◽

Universal Primers ◽

Term Survival ◽

Phytophthora Megasperma ◽

First Report ◽

Umbria Region ◽

Celtis Australis

European hackberry (Celtis australis L.) is a popular shade tree mainly planted in southern Europe and known to be tolerant to dry and poor soils. In early autumn 2013, hackberry plants grown in soil in a commercial nursery located in the floodplain in Umbria region showed symptoms of wilting, dieback, and death. Up to 100% of the canopy was affected, and over 60% of the plants were symptomatic or dead. A Phytophthora species was consistently isolated from symptomatic 6-year-old plants by plating small pieces of collar and root tissues, cut from the margin of dark-brown necrotic lesions, onto P5ARPH selective medium (4). Pure cultures were obtained by single-hyphal transfers on potato dextrose agar (PDA). Sporangia, produced on pepper seeds in soil extract solution (3), were nonpapillate and noncaducous, measuring 34.0 to 85.0 × 22.0 to 50.0 μm. Oospores had an average diameter of 44 μm with mostly paragynous antheridia. On the basis of morphological features, the isolates were identified as P. megasperma Drech. (2). The identity was confirmed by sequencing the cytochrome c oxidase subunit II (Cox II) (5), which gave 100% identity with P. megasperma sequences available in GenBank (GU222070), and by sequencing the internal transcribed spacer (ITS) using the universal primers ITS4 and ITS6, which gave 99% identity with the AF266794 sequence from Cooke et al. (1). The sequences of one isolate (AB239) were deposited in the European Nucleotide Archive (ENA) with accession numbers HG973451 and HG973450 for Cox II and ITS, respectively. Pathogenicity tests were conducted in the greenhouse with isolate AB239 on eight 2-year-old potted European hackberry plants. Mycelial plugs (5 mm diameter) cut from the margins of actively growing 8-day-old cultures on PDA were inserted through the epidermis to the phloem at the collar level. Two plants were used as controls and treated as described above except that sterile PDA plugs replaced the inoculum. Inoculated plants were kept for 4 weeks in a greenhouse at 24 ± 2°C. During that period, inoculated plants showed wilting symptoms similar to those observed in the field. Lesions were evident at all the inoculation points progressing downward to the roots. Colonies of Phytophthora were isolated from the margins of lesions and identified as P. megasperma, thus fulfilling Koch's postulates. Controls remained symptomless. P. megasperma taxonomy is rather complex since it embraces different subgroups, including host specialized forms (formae speciales), some of which are recognized as biological species. Based on morphological and molecular data presented here, the Phytophthora isolates from hackberry belong to P. megasperma sensu stricto, which is included in the “pathogenic to a broad range of hosts” (BHR) group (1). This pathogen is rather polyphagous, attacking mainly fruit and ornamental woody plants, commonly Prunus spp., Malus spp., and Actinidia deliciosa. Like other homothallic Phytophthora species, it is particularly dangerous due to its abundant production of thick-walled resting oospores that enable long-term survival in the soil. To our knowledge this is the first report of P. megasperma sensu stricto (1) on C. australis and its family Ulmaceae/Cannabaceae. References: (1) D. E. L. Cooke et al. Fungal Genet. Biol. 30:17, 2000. (2) D. C. Erwin and O. K. Ribeiro, American Phytopathological Society, St. Paul, MN, 1996. (3) E. Ilieva et al. Eur. J. Plant Path. 101:623, 1995. (4) S. N. Jeffers and S. B. Martin. Plant Dis. 70:1038, 1986. (5) F. N. Martin and P. W. Tooley. Mycologia 95:269, 2003.

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

Plant Disease ◽

10.1094/pdis-94-7-0917a ◽

2010 ◽

Vol 94 (7) ◽

pp. 917-917

Author(s):

A. Garibaldi ◽

D. Bertetti ◽

M. L. Gullino

Keyword(s):

Root Rot ◽

Infected Plant ◽

Its Region ◽

Soil Extract ◽

Phytophthora Nicotianae ◽

Control Treatment ◽

Experimental Unit ◽

Peat Moss ◽

Late Winter ◽

First Report

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

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