A Severe Outbreak of Charcoal Rot in Cantaloupe Melon Caused by Macrophomina phaseolina in Chile

A severe outbreak of charcoal rot was observed in cantaloupe melon (Cucumis melo L.) in the summer of 2011 to 2012 in Curacaví Valley, Chile. Prior to harvest, of 72 plants per cultivar, charcoal rot prevalence varied from 32% to 82% in cvs. Colima, Charantias, Navigator, Origami, Otero, and Samoa. Symptoms were wilting and leaf browning associated with water-soaked lesions at the base of the crown with amber to dark brown exudates. Lesions dried out progressively, turned tan, and cracked. Affected plants declined and died before harvest. Reddish fruit decay was observed. Symptomatic stem and root samples (n = 97) were collected, surface disinfected (96% ethanol, 30 s), plated on PDA acidified with 0.5 ml/liter of 92% lactic acid (APDA), and incubated at 20 ± 1°C. A white, fast-growing mycelium was obtained that turned gray to black after 7 days due to the presence of spherical to oblong black microsclerotia 136 ± 52 μm (n = 80) in diameter. On the basis of colony morphology and microsclerotia, 57 isolates (59%), obtained from 97 melon samples, were tentatively identified as Macrophomina phaseolina (Tassi) Goid. (2,3). The morphological identification of four isolates M1HB-B, M2CO-B, M3CH-R, and M4OT-B (GenBank Accession Nos. JX203630, JX203631, JX203632, and JX203633) was confirmed by sequencing of the internal transcribed spacer region (ITS1-5.8S-ITS2) of rDNA, using primers ITS4 and ITS5, with >99% similarity with the sequences of M. phaseolina (GenBank Accession No. HQ660592) (4). Pathogenicity tests were conducted with isolates M1HB-B, M2CO-B, M3CH-R, and M4OT-B on melon fruits cvs. Colima, Origami, Charantias, and Diva. Four mature melon fruits per cultivar per isolate were surface disinfected with 0.5% sodium hypochlorite for 2 min before inserting a mycelium plug (19 mm2) in a 6 mm diameter hole made with a sterile cork borer. An equal number of perforated fruits in which a sterile agar plug was inserted were left as non-inoculated controls. After 8 days of incubation at 20°C, inoculated fruits developed a spherical, reddish, soft necrotic lesion of 15 to 20 mm in diameter in the pulp. Non-inoculated fruits remained symptomless. The pathogenicity of the four isolates was also studied in 3-month-old melon plants (n = 4) cvs. Colima and Navigator. Plants were inoculated by inserting a mycelial plug (9 mm2) underneath the epidermis of the crown, 5 cm above the soil level. The inoculation site was immediately wrapped with Parafilm to avoid dehydration. An equal number of non-inoculated, but injured plants, treated with a sterile agar plug, were left as controls. After 21 days of incubation under greenhouse conditions (17 ± 5.5°C), all inoculated plants developed water-soaked to dry necrotic lesions, 20 to 70 mm long, yellow to tan in color. No symptoms were obtained in non-inoculated controls. M. phaseolina was reisolated in 84% and 100% of the inoculated plants and fruits, respectively. To our knowledge, this study is the first report of charcoal rot in cantaloupe melon in Chile, previously found on watermelon and melon group inodorus (1). Charcoal rot appears as an emerging disease that aggressively affects current cantaloupe melon cultivars in central Chile. References: (1) G. Apablaza. Cien. Inv. Agr. 20:101, 1993. (2) B. D. Bruton and E. V. Wann. Charcoal rot. Page 9 in: Compendium of Cucurbit Diseases. T. A. Zitter, D. L. Hopkins, and C. E. Thomas, eds. APS, St. Paul, MN, 1996. (3) S. Kaur et al. Crit. Rev. Microbiol. 38:136, 2012. (4) J. Q. Zhang et al. Plant Dis. 95:872, 2011.

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First Report of Botryosphaeria rhodina Causing Shoot Blight of Pistachio in California

Plant Disease ◽

10.1094/pdis.2002.86.11.1273c ◽

2002 ◽

Vol 86 (11) ◽

pp. 1273-1273 ◽

Cited By ~ 9

Author(s):

T. J. Michailides ◽

D. P. Morgan ◽

D. Felts ◽

J. Phillimore

Keyword(s):

Current Season ◽

First Report ◽

Mycelial Plug ◽

Shoot Blight ◽

Botryosphaeria Rhodina ◽

Pathogenicity Tests ◽

Cork Borer ◽

Negative Controls ◽

Positive Controls ◽

Pistachio Trees

In the summers of 2000 and 2001, shoot blight was observed in pistachios (Pistacia vera L.) grown in Kern County, California. Black, necrotic lesions developed at the base of shoots originating from contaminated or partially infected buds. Infection moved upward resulting in a progressive wilting and blighting of leaves. Leaf blades on infected shoots withered, and petioles became necrotic. Symptoms have been considered characteristic of infection by Botryosphaeria dothidea (Moug.:Fr.) Ces. & de Not., but this pathogen causes panicle and shoot blight of pistachio (1). However, there were no symptoms of any fruit panicle infections on trees we observed. Isolations on acidified potato dextrose agar from the base of blighted shoots in both years revealed a fast-growing fungus producing pycnidia which was identified as the anamorph Lasiodiplodia theobromae (Pat.) Griffon & Maubl. of B. rhodina Berk. & Curt. Arx. Identification of the pathogen was based on characteristic dark brown, oval pycnidiospores with striations on the surface of the spore along the long axis. Pathogenicity tests were performed on 12 Kerman pistachio trees grown at Kearney Agricultural Center, in Parlier, CA, using three isolates recovered from pistachios grown in two locations. Six to 16 current season shoots of pistachio trees (1 to 2 shoots per tree) were wounded with a 5-mm-diameter cork borer, and a mycelial plug of 5-day-old cultures of B. rhodina was inserted in each wound. Shoots were wrapped with Parafilm to prevent desiccation of inoculum. Six other shoots (one per tree) were inoculated similarly with mycelial agar plugs of a pistachio isolate of B. dothidea and served as positive controls, while six similar shoots were inoculated with only agar plugs and served as negative controls. Wilting of lower leaves in the majority of inoculated shoots started within 4 days for B. rhodina and 7 days for B. dothidea. Depending on the isolate of B. rhodina, 1 to 5 shoots and 50 to 80% of leaves were blighted within 7 days after inoculation. All inoculated shoots were left on the trees until 3 to 4 months after inoculation, pruned and assessed again. For inoculations done in September 2001, 33 to 71% of shoots were blighted, and the rest had cankers ranging from 22.5 to 28 mm long and 13.5 to 23.5 mm wide. A majority (67 to 100%) of shoots had pycnidia of the pathogen present. For inoculations done in October 2001, none of the shoots was blighted, but cankers ranged from 5 to 55.4 mm long and 6 to 22 mm wide and 33.3 to 100% developed pycnidia. B. rhodina was isolated from all inoculated shoots but not from negative controls or those inoculated with B. dothidea. Inoculations of shoots with B. dothidea produced similar symptoms as those of B. rhodina. Shoots that served as negative controls did not develop symptoms. Because panicle and shoot blight of pistachio caused by B. dothidea has developed to epidemic levels in commercial pistachio orchards and is of concern to the pistachio industry in California, it would be of interest to monitor how much shoot blight caused by B. rhodina would eventually develop over the years in commercial pistachio orchards. A survey was initiated in 2002 to determine how widespread B. rhodina is in California pistachios. To our knowledge, this is the first report worldwide of B. rhodina causing shoot blight of pistachio. Reference: (1) T. Michailides. Panicle and shoot blight. Page 68 in: Compendium of Nut Crop Diseases in Temperate Zones. B. L. Teviotdale, T. J. Michailides, and J. W. Pscheidt, eds. American Phytopathological Society, St. Paul, MN 2002.

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First Report of Charcoal Rot Caused by Macrophomina phaseolina in Sunflower in Turkey

Plant Disease ◽

10.1094/pdis-09-10-0631 ◽

2011 ◽

Vol 95 (2) ◽

pp. 223-223 ◽

Cited By ~ 10

Author(s):

A. Mahmoud ◽

H. Budak

Keyword(s):

Random Amplified Polymorphic Dna ◽

Peat Soil ◽

Pathogenic Fungi ◽

Macrophomina Phaseolina ◽

Vascular Bundles ◽

Internal Transcribed Spacer Region ◽

Charcoal Rot ◽

First Report ◽

Surface Sterilization ◽

Lower Stem

Charcoal rot symptoms were observed on 2-month-old oilseed sunflower plants (Helianthus annuus L.) in the Eskişehir Province of Turkey in June 2009. The disease was observed in 70% of the fields surveyed and incidence ranged from 10 to 50%. Symptoms were first observed in plants approaching physiological maturity and consisted of silver-gray lesions girdling the stem at the soil line, reduced head diameter compared with noninfected plants, and premature plant death. Pith in the lower stem was completely absent or compressed into horizontal layers. Black, spherical microsclerotia were observed in the pith area of the lower stem, underneath the epidermis, and on the exterior of the taproot. The internal stem had a shredded appearance. Later, the vascular bundles became covered with small, black flecks or microsclerotia of the fungus. Forty plant samples were collected from 10 fields. After surface sterilization with 2% NaOCl, outer tissues sampled from diseased tissues (2 to 3 mm long) of root and stems were removed and transferred to potato dextrose agar containing 250 mg liter–1 of chloramphenicol. Petri plates were incubated for 7 days at 26 ± 2°C in the dark. Ninety-eight percent of the fungal colonies were identified as Macrophomina phaseolina (Tassi) Goidanich based on gray colony color, colony morphology, and the size of the microsclerotia, which ranged from 80 to 90 μm in diameter, from both infected sunflowers and compared with pure cultures (3). All resulting cultures produced abundant microsclerotia. The only other sunflower pathogen known to form microsclerotia is Verticillium dahliae Kleb., whose microsclerotia are irregular in shape and 15 to 50 μm in diameter. Sequence-related amplified polymorphisms technique was used for diversity of M. phaseolina since it has proven to be more informative than amplified fragment length polymorphism, random amplified polymorphic DNA, and simple sequence repeat (2). Results showed a high level of genetic diversity (60%) among the 26 isolates of M. phaseolina. Sequencing of the internal transcribed spacer region (1) showed high homology (>96%) to M. phaseolina (GenBank Accession No. HQ380051). Pathogenicity tests for 20 isolates of M. phaseolina were carried out on three commercially used cultivars, SANAY, TUNCA, and TR-3080. Groups of 10 seedlings were grown separately in an autoclaved peat/soil mixture in 30-cm-diameter plastic pots in a greenhouse at 30 ± 2°C. Soil infestation was performed 1 day before sowing. Two-week-old cultures on barley medium (4) were blended in distilled sterile water and adjusted to 105 sclerotia ml–1. Each pot received 250 ml of inoculant. Each treatment had three replications. Three pots for each cultivar were left uninoculated. Within 3 weeks, five to seven inoculated plants in each pot died. Identical disease symptoms were observed 30 days after inoculation; on the control plants no symptoms were observed. Microsclerotia were produced after 7 weeks at the stem base on 85% of the surviving plants. To our knowledge, this is the first report of M. phaseolina in sunflower in Turkey. References: (1) B. D. Babu et al. J. Plant Dis. Prot. 96:797, 2007. (2) H. Budak et al. Theor. Appl. Genet. 109:280, 2004. (3) P. Holliday and E. Punithalingam. No. 275 in: Description of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, UK, 1970. (4) M. R. Omar et al. J. Plant Dis. Prot. 114:196, 2007.

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First Report of the Anamorph of Glomerella acutata Causing Anthracnose on Avocado Fruits in Mexico

Plant Disease ◽

10.1094/pdis-91-9-1200a ◽

2007 ◽

Vol 91 (9) ◽

pp. 1200-1200 ◽

Cited By ~ 4

Author(s):

G. Avila-Quezada ◽

H. V. Silva-Rojas ◽

D. Teliz-Ortiz

Keyword(s):

Colletotrichum Gloeosporioides ◽

Soft Rot ◽

Lower Surface ◽

Persea Americana ◽

Colletotrichum Acutatum ◽

Morphological Identification ◽

Internal Transcribed Spacer Region ◽

First Report ◽

Mexican State ◽

Pathogenicity Tests

Mexico is a major avocado (Persea americana) producer in the world. Glomerella cingulata (anamorph Colletotrichum gloeosporioides) has been reported as a causal agent of anthracnose on avocado fruits worldwide (3), while G. acutata (anamorph Colletotrichum acutatum) has been identified as the cause of this disease only in New Zealand (2) and Australia (4). This study was done with the objective to determine the Glomerella spp. involved as the causal agents of avocado anthracnose in Mexico. From 2003 to 2006, avocado fruits cv. Hass with anthracnose symptoms appearing as brown-black lesions on the pericarp and soft rot in the mesocarp were collected in 10 counties in Michoacan, the leading avocado-producing Mexican state. Glomerella spp. were isolated on potato dextrose agar (PDA) for molecular and morphological identification. A phylogenetic analysis was done by amplifying the internal transcribed spacer region of rDNA for 28 of the isolates. Primers ITS5/NL4 was used and successfully amplified bands of approximately 1,000 bp. Each sequence corresponding to Glomerella spp. was compared with sequences deposited in the GenBank database using BLAST. The results from molecular approach indicated 86% of the isolates used in this study were G. cingulata and 14% were G. acutata. Sequences of both species were deposited in GenBank under Accession Nos. EF221828, EF221829, and EF221830 for G. cingulata and EF175780, EF221831, and EF221832 for G. acutata. Colonies of G. acutata that developed on PDA medium were pale gray, occasionally the lower surface was olive green, and the center was covered with orange-to-salmon pink masses of conidia and perithecia. Conidia grown in the same media were straight, fusiform, 8.2 to 16.5 μm long, and 2.7 to 4.0 μm wide (4). Pathogenicity tests of G. acutata were carried out by inoculating six healthy cv. Hass fruits (1) at three evenly spaced locations on the fruit surface with a needle dipped in a conidial mass from a 3-day-old monoconidial culture of G. acutata. Fruits were then incubated in a moist chamber for 3 days. Anthracnose symptoms were observed on healthy fruits inoculated with G. acutata, while control fruits inoculated with sterile water did not develop symptoms. The fungi were reisolated successfully to confirm the pathogen's identity using morphological key. To our knowledge, this is the first report of G. acutata causing anthracnose on avocado fruits in Mexico. References: (1) R. Guetsky et al. Phytopathology 95:1341, 2005. (2) W. F. T. Hartill. N. Z. J. Crop Hortic. Sci. 19:297, 1991. (3) D. Prusky. Annu. Rev. Phytopathol. 34:413, 1996. (4) J. H. Simmonds. Qld. J. Agric. Anim. Sci. 22:437, 1965.

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First Report of Charcoal Rot Caused by Macrophomina phaseolina on Mungbean in China

Plant Disease ◽

10.1094/pdis-01-11-0010 ◽

2011 ◽

Vol 95 (7) ◽

pp. 872-872 ◽

Cited By ~ 10

Author(s):

J. Q. Zhang ◽

Z. D. Zhu ◽

C. X. Duan ◽

X. M. Wang ◽

H. J. Li

Keyword(s):

Infected Plant ◽

Pcr Primers ◽

Macrophomina Phaseolina ◽

Shaanxi Province ◽

Shanxi Province ◽

Universal Primers ◽

Yield Reduction ◽

Morphological Identification ◽

Charcoal Rot ◽

Mist Chamber

Mungbean (Vigna radiata L.), an important leguminous food crop in China, is popularly grown in arid regions. The total area of mungbean production is 8.0 × 105 ha. In August and September 2010, wilted symptoms were observed in mungbean plants in Yulin, Shaanxi Province and Datong, Shanxi Province. Infected plants had silvery gray coloration of stems and lateral branching with senesced leaves still attached to the plant. Dark brown necrotic areas were observed on the exterior of the taproot underneath the epidermis and in the pith of the lower stems of wilted plants. Black spherical microsclerotia, 43.9 μm, were present in infected plant tissues. Six fungal isolates were cultured on potato dextrose agar at 25°C and the mycelium was initially hyaline but later became gray. Black microsclerotia, 60 to 80 × 75 to 123 μm, were observed in culture after 2 to 7 days of incubation. On the basis of field symptoms, colony color, and the size of microsclerotia, the fungus was identified as Macrophomina phaseolina (Tassi) Goid (3). To confirm the morphological identification, the rDNA internal transcribed spacer (ITS) regions of the six isolates were amplified with universal primers ITS1 and ITS4. The resulting ITS sequences of the six isolates (GenBank Accession Nos. HQ660589, HQ660590, HQ660591, HQ660592, HQ660593, and HQ660594) were aligned in GenBank, which showed 97 to 99% identity with 60 M. phaseolina isolates (e.g., Accession Nos. GU046867, FJ415067, and FJ960441). Using the PCR primers MpKF1 (5′-CCGCCAGAGGACTATCAAAC-3′) and MaKR1 (5′-CGTCCGAAGCGAGGTGTATT-3′) specific for M. phaseolina (1), a 350-bp PCR fragment was obtained, indicating that these isolates were M. phaseolina. Pathogenicity tests of six isolates were performed by inoculation of 3-week-old seedlings of cv. Zhonglv 8 using the hypocotyl inoculation technique, respectively (2). Each isolate was transferred to petri dishes containing PDA 2 days prior to inoculation. On the day of inoculation, an inoculum slurry was prepared by cutting agar with the pathogen into small strips and passing the strips through a 5-syringe until uniform. A small quantity of inoculum extruded into the vertical cut in each hypocotyl of at least eight seedlings in each pot, and the PDA was used as the control to extrude into the vertical cut in each hypocotyl of at least eight seedlings in another pot. The inoculated and control plants were incubated in the mist chamber at 25°C and 90 to 100% relative humidity for 48 h before growing in a greenhouse at 30°C. Six days after inoculation, all inoculated plants, wilted or dead, showed dark brown-toblack lesions. No symptoms were observed on the control plants. For each isolate tested, M. phaseolina was reisolated from inoculated plants, but was not isolated from the control plants. The fungus has been detected in 29 plant species of 23 genera in China, including the major crops Arachis hypogaea, Helianthus annuus, and Glycine max. Although M. phaseolina has caused great yield reduction of mungbean in many areas of Asia, to our knowledge, this fungus as a causal agent of mungbean charcoal rot has not previously been reported in China. Reference: (1) B. K. Babu et al. Mycologia 99:797, 2007. (2) D. L. Pazdernik et al. Plant Dis. 81:1112, 1997. (3) G. S. Smith and T. D.Wyllie. Charcoal rot. Page 29 in: Compendium of Soybean Diseases. 4th ed. G. L. Hartmann et al., eds. The American Phytopathological Society, St. Paul, MN, 1999.

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Characterization and pathogenicity of Pythium-like species associated with root and collar rot of kiwifruit in Turkey

Plant Disease ◽

10.1094/pdis-05-21-0961-re ◽

2021 ◽

Author(s):

Muharrem Türkkan ◽

Göksel Özer ◽

Gürsel Karaca ◽

İsmail Erper ◽

Sibel Derviş

Keyword(s):

Dna Sequences ◽

Growth Parameters ◽

Morphological Identification ◽

Nuclear Rdna ◽

Internal Transcribed Spacer Region ◽

Collar Rot ◽

Optimum Growth Temperature ◽

Rdna Its ◽

Optimum Ph ◽

Pathogenicity Tests

During the period of June to October in 2018, a widespread decline was observed on kiwifruit vines in the vineyards located in Altınordu, Fatsa, and Perşembe districts of Ordu province. The symptoms were associated with reddish-brown rots expanding from the root to the collar with sparse off-color foliage. Based on the percentage of the total infected samples across 18 vineyards, the most common oomycete species were Globisporangium intermedium (37.1%), Phytopythium vexans (34.3%), G. sylvaticum (14.3%), G. heterothallicum (11.4%), and Pythium dissotocum (2.9%). The morphological identification of isolates was confirmed based on partial DNA sequences containing the nuclear rDNA internal transcribed spacer region (rDNA ITS) and the mitochondrial cytochrome c oxidase subunit II (coxII) gene. The optimum growth temperature and the optimum pH of 5 species ranged from 22.98 to 28.25°C and 5.67 to 8.51, respectively. Pathogenicity tests on the seedlings of kiwifruit cv. Hayward revealed significant differences in virulence among isolates. Phytopythium vexans and G. sylvaticum isolates caused severe root and collar rot resulting in seedling death, while G. heterothallicum and G. intermedium isolates had relatively lower virulence. All Globisporangium spp. and P. vexans isolates significantly decreased plant growth parameters (plant height, shoot and root dry weights and root length); however, P. dissotocum caused very mild symptoms and did not affect these parameters of growth. To our knowledge, this is the first study reporting G. sylvaticum, G. heterothallicum, and G. intermedium causing root and collar rot on kiwifruit not only in Turkey but also in the world.

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First Report of Seimatosporium botan Associated with Trunk Disease of Grapevine (Vitis vinifera) in Chile

Plant Disease ◽

10.1094/pdis-05-12-0478-pdn ◽

2012 ◽

Vol 96 (11) ◽

pp. 1696-1696 ◽

Cited By ~ 4

Author(s):

G. A. Díaz ◽

K. Elfar ◽

B. A. Latorre

Keyword(s):

Cross Sections ◽

Lesion Length ◽

Woody Tissue ◽

First Report ◽

Trunk Disease ◽

Agar Plug ◽

Significant Difference ◽

Pathogenicity Tests ◽

Cork Borer ◽

Dark Green

Grapevines are planted on 180,000 ha in Chile. In 2010 and 2011, necrotic lesions and hard texture were observed on woody tissue on 10-year-old vines of cvs. Cabernet Sauvignon, Carménère, Moscatel de Alejandría, and Pedro Jimenez in Ovalle (lat. 30°58′ S) and Cauquenes (lat. 35°58′ S). Symptoms were on 10 to 25% of the arm cross sections, resembling symptoms caused by Botryosphaeriaceae (4). Prevalence of 5% was estimated visually in Ovalle (n = 920 grapevines) and Cauquenes (n = 350 grapevines). Small pieces (3 mm) of necrotic tissues from the margins of lesions in cordons (n = 32) were surface sterilized (96% ethanol, 15 s), and plated on acidified PDA plus 0.5 ml/liter of 92% lactic acid, 0.005% tetracycline, 0.01% streptomycin, and 0.1% Igepal CO-630 (Sigma-Aldrich, St. Louis, MO) (APDA). The plates were incubated at 20°C for 14 days. Isolates (n = 12) were obtained from the yellow to dark green slimy colonies with white irregular margins, staining brown the underside of APDA plates. Black acervuli and ellipsoid to fusiform conidia were obtained. Conidia were triple septated, with hyaline upper and bottom cells and brown middle cells (n = 30) of 17.7 ± 1.2 × 5.8 ± 0.8 μm. A basal conidial appendage (6.2 ± 1.0 μm) was always obtained, but conidia having appendages at both ends also were observed. Morphologically, these isolates were identified as Seimatosporium botan Sat. Hatak. & Y. Harada (2). The identification of isolates sei-302 and sei-316 was confirmed by amplifying and sequencing the region ITS1-5.8S-ITS2 of rDNA using ITS4 and ITS5 primers (GenBank Accession Nos. JN088482 and JN088483). BLAST analyses showed 100% similarity with S. botan (Accession No. HM067840) (2). Pathogenicity tests were conducted with isolates sei-302 and sei-316 on detached green shoots (GS) and on rooted 2-year-old vines ‘Carménère.’ Rooted vines were inoculated at the base of canes and trunks. Inoculations were performed by placing a mycelial agar plug taken from APDA on a wound aseptically made with a cork borer. Wounds were sealed with Parafilm to avoid a rapid dehydration. The inoculated GS were incubated for 2 weeks in a moisture chamber (relative humidity >80%) at 20°C. Inoculated 2-year-old vines were placed in a lath-house for 7 and 15 months for canes and trunk inoculation, respectively. An equal number of GS and vines were inoculated with sterile agar plugs and left as controls. Necrotic lesions with mean of 23.7 ± 2.5 mm on GS, 50.5 ± 3.4 mm on canes, and 41.9 ± 2.3 mm on trunks developed. No significant difference (P < 0.05) was obtained in lesion length between S. botan isolates. After 7 months, 40% of inoculated canes had died. No symptoms were observed in GS controls and rooted control vines treated with sterile agar plugs. S. botan was reisolated from 93 to 100% of the inoculated samples. Previously, S. botan was reported as pathogenic in Paeonia suffruticosa (1), and Seimatosporium sp. was isolated from V. vinifera in California, but their pathogenicity was not demonstrated (3). To our knowledge, this is the first report of pathogenic isolates of S. botan associated with trunk disease of grapevines. These results contribute to the knowledge of the trunk disease of grapevines worldwide. References: (1) Y. Duan et al. Plant Dis. 95:226, 2011. (2) S. Hatakeyama et al. Mycoscience 45:106, 2004. (3) Z. Morales et al. Phytopathol. Mediterr. 49:109, 2010. (4) J. R. Úrbez-Torres. Phytopathol. Mediterr. 50:S5, 2011.

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First Report of Charcoal Rot Caused by Macrophomina phaseolina in Soybean in New York

Plant Disease ◽

10.1094/pdis-03-13-0318-pdn ◽

2013 ◽

Vol 97 (11) ◽

pp. 1506-1506 ◽

Cited By ~ 5

Author(s):

J. A. Cummings ◽

G. C. Bergstrom

Keyword(s):

United States ◽

New York ◽

Pcr Amplification ◽

Macrophomina Phaseolina ◽

The United States ◽

Its Sequencing ◽

Charcoal Rot ◽

Production Region ◽

Agar Plug ◽

Soybean Plants

Charcoal rot of soybean (Glycine max (L.) Merr.), incited by Macrophomina phaseolina (Tassi) Goidanich, is commonly found in much of the southern soybean production region of the United States, where it can be a major contributor to yield loss in warm, dry seasons (4). The disease has also been reported in northern states including Michigan, Minnesota, North Dakota, and Wisconsin (1,2,3). In early July of the warmer and drier than normal 2012 growing season, wilted soybean plants were observed and collected for diagnosis from a field in Cayuga County, NY. The diseased plants showed brown discoloration of the stem and roots but the diagnostic microsclerotia of M. phaseolina had not yet developed in the epidermis. Cut pieces of roots and crowns were surface-sterilized in 20% sodium hypochlorite, rinsed in sterile distilled water, and incubated on potato dextrose agar at room temperature with a 12-h photoperiod for 7 days. The pathogen was observed growing out of many of the crown and root pieces, and produced abundant microsclerotia as described by Smith and Wyllie (4). Pathogenicity of isolate Mp001NY12 was confirmed using a cut stem inoculation method. Five soybean plants were grown to the unifoliate stage and inoculated by cutting the stem above the unifoliate leaves and applying a fully colonized agar plug to the wound. Within 2 weeks, infection was obvious with microsclerotia formed in the epidermis of all infected plants, and M. phaseolina was reisolated from all infected plants. DNA of isolate Mp001NY12 was extracted from colonies grown on PDA with PrepMan Ultra DNA extraction kit (Applied Biosystems, Foster City, CA), and the DNA was submitted for ITS sequencing with the ITS1 and ITS4 primers used for PCR amplification. The ITS sequence (GenBank Accession No. KC800709) of Mp001NY12 was compared to those in the NCBI GenBank database using a BLAST search, and had 99% nucleotide sequence identity with M. phaseolina (accessions JX945170, FJ415067, and EU250575). To the best of our knowledge, charcoal rot has not been reported previously on soybean or other plant hosts in New York or in other states in the northeastern United States. References: (1) Baird et al. Mycopathologia 170:169, 2010. (2) C. A. Bradley and L. E. del Rio. Plant Dis. 87:601, 2003. (3) M. E. ElAraby et al. Plant Dis. 87:202, 2003. (4) G. S. Smith and T. D. Wyllie. Charcoal rot. Page 29 in: Compendium of Soybean Diseases, 4th ed. G. L. Hartman et al., eds. APS Press, St. Paul, MN, 1999.

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First Report of Cylindrocarpon pauciseptatum Associated with Grapevine Decline from Castilla y León, Spain

Plant Disease ◽

10.1094/pdis-10-10-0750 ◽

2011 ◽

Vol 95 (3) ◽

pp. 361-361 ◽

Cited By ~ 5

Author(s):

M. T. Martin ◽

L. Martin ◽

M. J. Cuesta ◽

P. García-Benavides

Keyword(s):

Morphological Characteristics ◽

Vascular Lesions ◽

Width Ratio ◽

Morphological Identification ◽

Malt Extract ◽

Internal Transcribed Spacer Region ◽

Current Season ◽

First Report ◽

Grapevine Decline ◽

Agar Plug

During a survey for grapevine decline, 10 young grapevines (cvs. Tempranillo and Verdejo) with low vigor and little foliage were collected between June 2008 and August 2009. Small pieces of vascular and brown wood were placed onto malt extract agar supplemented with 0.25 g/liter of chloramphenicol and incubated at 25°C. Fifteen resulting colonies were transferred to potato dextrose agar in petri dishes (90 mm). Colonies with white mycelium covered the dishes after 10 days of incubation at 25°C in darkness; mycelium gradually became yellowish with some brownish aspect. Macroconida were predominantly three septate (40 to 45 to 50 × 8.6 to 9 to 9.5 μm with a length and width ratio of 4.7 to 5 to 5.4), straight, and cylindrical with both ends broadly rounded. Chlamydospora and ovoidal microconidia were observed on synthetic nutrient-poor agar (1). Cylindrocarpon pauciseptatum was not easy to distinguish from other Cylindrocarpon species based on morphological characteristics. Ribosomal internal transcribed spacer region sequences of single-spore cultures confirmed the morphological identification and revealed 100% genetic identity with other isolates of C. pauciceptatum present in GenBank (EF607090), a sequence of the fragment was deposited with Accession No. EU983277. Pathogenicity tests were conducted with two isolates. The inoculations were done on 110R rootstock wood of four different young plants and 15 detached canes of current-season growth (cv. Tempranillo). Plants were inoculated with an agar plug containing C. pauciceptatum; controls were treated with agar only. Grapevines were maintained in a greenhouse at 20 to 25°C. After 3 to 4 months, C. pauciceptatum was reisolated from brown tissues and internal vascular lesions in 45% of inoculated samples, fulfilling Koch's postulates. Control plants were asymptomatic and C. pauciceptatum was not recovered. To our knowledge, this is the first report implicating C. pauciceptatum as a cause of grapevine black foot disease in Spain with potentially significant impact on grapevine nurseries. Reference: (1) H. J. Schroers et al. Mycol. Res. 112:82, 2008.

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Toxin Production in Soybean (Glycine max L.) Plants with Charcoal Rot Disease and by Macrophomina phaseolina, the Fungus that Causes the Disease

Toxins ◽

10.3390/toxins11110645 ◽

2019 ◽

Vol 11 (11) ◽

pp. 645 ◽

Cited By ~ 8

Author(s):

Hamed K. Abbas ◽

Nacer Bellaloui ◽

Cesare Accinelli ◽

James R. Smith ◽

W. Thomas Shier

Keyword(s):

Culture Media ◽

Leaf Disc ◽

Toxin Production ◽

Macrophomina Phaseolina ◽

Economic Losses ◽

Limit Of Quantification ◽

Charcoal Rot ◽

Wide Range ◽

Soybean Plants ◽

Rot Disease

Charcoal rot disease, caused by the fungus Macrophomina phaseolina, results in major economic losses in soybean production in southern USA. M. phaseolina has been proposed to use the toxin (-)-botryodiplodin in its root infection mechanism to create a necrotic zone in root tissue through which fungal hyphae can readily enter the plant. The majority (51.4%) of M. phaseolina isolates from plants with charcoal rot disease produced a wide range of (-)-botryodiplodin concentrations in a culture medium (0.14–6.11 µg/mL), 37.8% produced traces below the limit of quantification (0.01 µg/mL), and 10.8% produced no detectable (-)-botryodiplodin. Some culture media with traces or no (-)-botryodiplodin were nevertheless strongly phytotoxic in soybean leaf disc cultures, consistent with the production of another unidentified toxin(s). Widely ranging (-)-botryodiplodin levels (traces to 3.14 µg/g) were also observed in the roots, but not in the aerial parts, of soybean plants naturally infected with charcoal rot disease. This is the first report of (-)-botryodiplodin in plant tissues naturally infected with charcoal rot disease. No phaseolinone was detected in M. phaseolina culture media or naturally infected soybean tissues. These results are consistent with (-)-botryodiplodin playing a role in the pathology of some, but not all, M. phaseolina isolates from soybeans with charcoal rot disease in southern USA.

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