First Report of the Prevalence of Benzimidazole-Resistant Isolates in a Population of Cylindrocladium pauciramosum in Italy

Cylindrocladium pauciramosum C.L. Schoch & Crous (teleomorph Calonectria pauciramosa C.L. Schoch & Crous), described as a member of the Cylindrocladium candelabrum Viégas complex (4), was recently reported from Europe (3). In southern Italy, the fungus has caused extensive losses, and chemical control measures are necessary, especially in ornamental nurseries. Several researchers have found benzimidazole fungicides to be effective for control of different species of Cylindrocladium, however, in fungicide trials conducted on myrtle plants infected by C. pauciramosum, benomyl was ineffective (2). Another study showed that mycelial growth of six isolates was completely inhibited by carbendazim at a concentration of 1 μg a.i./ml whereas, concentrations of 10, 100, and 500 μg a.i./ml did not completely inhibit growth of four isolates (1). To examine benzimidazole resistance in C. pauciramosum, 200 single-conidia isolates were tested. These were collected during 1996 and 1997 from several symptomatic hosts in different nurseries located in Sicily and Calabria and identified through morphological characteristics as well as mating-type studies with tester strains. Sensitivity to benomyl was determined by plating mycelial plugs on potato dextrose agar (PDA) amended with benomyl at 1, 10, 100, and 500 μg a.i./ml. For 20 benomyl-resistant isolates, fungal growth was also determined at the same concentrations on carbendazim-amended PDA. Sensitivity was expressed as the minimum inhibitory concentration (MIC) (the lowest fungicide concentration that completely prevented fungal growth). Isolates that did not grow on benzimidazole-amended PDA were classed as sensitive. Isolates were considered resistant to benzimidazole if MIC values were greater than 1 μg a.i./ml. Of the 200 isolates tested, 58% were resistant to benomyl. The benomyl-resistant isolates tested for carbendazim sensitivity were cross-resistant to carbendazim. Most resistant isolates grew in the presence of benomyl at 500 μg a.i./ml. On agar culture, the isolates were either the fast-growing or slow-growing type. The slow-growing phenotype appears to be related to the higher level of resistance (500 μg a.i./ml). On the basis of these data, the use of benzimidazole for the control of this pathogen should be seriously questioned. To our knowledge, this is the first report of the prevalence of benzimidazole resistance in a population of C. pauciramosum. References: (1) G. Polizzi. Inf. Fitopatol. 11:39, 2000. (2) G. Polizzi and A. Azzaro. Petria 6:117, 1996. (3) G. Polizzi and P. W. Crous. Eur. J. Plant Pathol. 105:407, 1999. (4) C. L. Schoch et al. Mycologia 91:286, 1999.

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First Report of Benzimidazole-Resistant Isolates of Cylindrocladium scoparium in Europe

Plant Disease ◽

10.1094/pdis-93-1-0110a ◽

2009 ◽

Vol 93 (1) ◽

pp. 110-110 ◽

Cited By ~ 5

Author(s):

A. Vitale ◽

D. Aiello ◽

I. Castello ◽

G. Polizzi

Keyword(s):

South African ◽

Management Practices ◽

Resistance Management ◽

Fungal Growth ◽

Control Measures ◽

Tree Seedlings ◽

Benzimidazole Fungicides ◽

Centraalbureau Voor ◽

First Report ◽

Concentration Sensitivity

Cylindrocladium scoparium Morg. (teleomorph Calonectria morganii Crous, Alfenas & M.J. Wingf.) was detected for the first time in Sicilian ornamental nurseries in 2005 and was responsible for damping-off and leaf spot of mastic tree seedlings (4). In Sicily, C. scoparium has caused extensive losses, and chemical control measures for the disease were necessary, especially in young plants. The benzimidazoles, including the thiophanates, which are transformed to benzimidazoles, are effective at relatively low doses for the inhibition of different species of Cylindrocladium (2). However, in a fungicide trial conducted in a Sicilian nursery on Callistemon cuttings infected by C. scoparium, thiophanate methyl was ineffective. Fourteen isolates of Cylindrocladium sp. were recovered on potato dextrose agar (PDA) from rotted crown and roots of Pistacia lentiscus L. and Callistemon cvs. Laevis, Hanna Ray, Masotti Mini Red, and Rose Opal and cultured on carnation leaf agar. Isolates were identified as C. scoparium based on pyriform-to-broadly ellipsoidal terminal vesicles, conidiophore branching pattern, morphology of conidia and perithecia, as well as their ability to mate with opposite mating types of South African C. scoparium and Italian C. pauciramosum isolates. Perithecia containing viable ascospores developed after approximately 2 months. Three representative isolates were deposited at Fungal Biodiversity Centre, Centraalbureau voor Schimmelcultures (CBS120892, CBS119669, and CBS119670). Sensitivity to benzimidazole was determined by plating mycelial plugs on PDA amended with benomyl or carbendazim at 1, 10, 100, and 500 μg a.i./ml. Four plates were used for each fungicide concentration. Sensitivity was expressed as the minimum inhibitory concentration (MIC) (the lowest fungicide concentration that completely prevented fungal growth). Isolates that did not grow on benzimidazole-amended PDA were classed as sensitive. The experiment was repeated two times. Isolates were considered resistant to benzimidazole if MIC values were greater than 1 μg a.i./ml for benomyl and carbendazim. Of the 14 isolates tested, 13 were resistant to benzimidazole. The benomyl-resistant isolates were also resistant to carbendazim. Among the resistant isolates, five grew in the presence of 10 μg a.i./ml and one isolate grew at 100 μg a.i./ml. Widespread incidence of benzimidazole-resistant isolates in a population of C. pauciramosum was detected in Italy (3). Benzimidazole-resistant isolates of C. scoparium were previously detected in Brazil (1) where the constant use of benomyl in nurseries led to the selection of strains resistant to fungicide at nearly 1,000 μg a.i./ml. To our knowledge, this is the first report of benzimidazole-resistant isolates of C. scoparium in Europe. Because of the high incidence of benzimidazole-resistant isolates detected in our study, good fungicide resistance management practices should be followed. Appropriate cultural, biological, and chemical disease control methods should be combined and implemented to delay further changes in sensitivity of the pathogen. The exclusive use of benzimidazole fungicides in nursery for the control of Cylindrocladium spp. should be avoided. References: (1) A. Alfenas et al. ISPP. Chem. Contr. Newsl. 10:23, 1988. (2) P. W. Crous. Taxonomy and Pathology of Cylindrocladium (Calonectria) and Allied Genera. The American Phytopathological Society, St. Paul MN, 2002. (3) G. Polizzi and A. Vitale. Plant Dis. 85:1210, 2001. (4) G. Polizzi et al. Plant Dis. 90:1110, 2006.

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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.

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First Report of Postharvest Rot of Chestnuts Caused by Mucor racemosus f. sphaerosporus in Korea

Plant Disease ◽

10.1094/pdis-05-14-0547-pdn ◽

2014 ◽

Vol 98 (12) ◽

pp. 1742-1742

Author(s):

J. H. Park ◽

S. E. Cho ◽

S. H. Lee ◽

C. K. Lee ◽

H. D. Shin

Keyword(s):

Large Subunit ◽

Morphological Characteristics ◽

Control Measures ◽

Its Sequences ◽

Pathogenicity Test ◽

Postharvest Diseases ◽

Mucor Racemosus ◽

First Report ◽

Sewing Needle ◽

Postharvest Rot

The Republic of Korea (South Korea) is the second largest chestnut producer in the world. Major cultivars planted in Korea, including cv. Daebo, Hyogo57, and Okkwang, are hybrids of Japanese chestnut (Castanea crenata) and Chinese chestnut (C. mollissima). Because of high perishability, most chestnuts harvested in September and October are preserved in cold rooms (0°C) for marketing. During a survey of postharvest diseases in April to August 2013, chestnut rots were continuously observed in cold rooms located in Buyeo County, Korea. Preliminary studies revealed that the most common agent of rot appeared to be a species of Mucor. When cut open, infected chestnuts showed partial interior discoloration varying from chalky white to dark brown. About 3 to 10% of chestnuts showed symptoms. Hyogo57 seemed to be the most susceptible variety with higher infection rates, up to 30% in some piles. Isolation was done by placing infected tissues on potato dextrose agar. A representative isolate was deposited in the Korean Agricultural Culture Collection (Accession No. KACC47727). Sporangiophores were mostly erect, branched sympodially, and hyaline. Sporangia were globose, pale yellow at first, then grayish brown at maturity. Columellae were obovoid to globose, subhyaline to pale brown, and usually with truncate base and collars. Sporangiospores were globose to irregular, and 4 to 10 μm in diameter. Chlamydospores were cylindrical to globose with oil drops. The fungus was identified as Mucor racemosus f. sphaerosporus (Hagem) Schipper based on the morphological characteristics and growth at low temperature (3). To conduct molecular analyses, genomic DNA was extracted with DNeasy Plant Mini Kits (Qiagen Inc., Valencia, CA). The primers ITS1/ITS4 and NL1/LR3 were used to amplify the internal transcribed spacer (ITS) region of rDNA and the D1/D2 region of the large subunit (4). The resulting 595-bp ITS sequences and 678 bp D1/D2 sequences were deposited in GenBank (Accession Nos. KJ769665 and KF769666). BLAST searches revealed that both the ITS sequences and D1/D2 sequences showed more than 99% similarity with those of M. racemosus f. sphaerosporus, respectively (JN939201 and AJ878775). To perform a pathogenicity test, a suspension of sporangiospores (1 × 105 spores/ml) was sprayed over 10 chestnuts cv. Hyogo57 wounded with a sewing needle and kept in plastic containers (0°C, 100% RH). Another 10 chestnuts wounded with a sewing needle and treated with sterile water served as controls. After 5 days, typical rots appeared on the inoculated chestnuts, whereas no symptoms were observed on controls. Koch's postulates were fulfilled with the re-isolation of M. racemosus from inoculated chestnuts. The pathogenicity test was carried out twice with similar results. M. hiemalis and M. mucedo have been recorded on chestnuts as postharvest pathogens in Switzerland (2) and Chile (1). To our knowledge, this is first report of postharvest rot of chestnut caused by M. racemosus f. sphaerosporus worldwide as well as in Korea. Further studies are necessary for control measures during cold storage of fresh chestnuts. References: (1) D. F. Farr and A. Y. Rossman. Fungal Databases. Syst. Mycol. Microbiol. Lab., online publication, ARS, USDA, Retrieved May 23, 2014. (2) M. Jermini et al. J. Sci. Food Agric. 86:877, 2006. (3) M. A. A. Schipper. Stud. Mycol. 12:1, 1976. (4) G. Walther et al. Persoonia 30:11, 2013.

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First Report of Powdery Mildew Caused by Golovinomyces ambrosiae on Verbena bonariensis in Korea

Plant Disease ◽

10.1094/pdis-02-21-0349-pdn ◽

2021 ◽

Author(s):

In-Young Choi ◽

Ho-Jong Ju ◽

Kui-Jae Lee ◽

Hyeon-Dong Shin

Keyword(s):

Powdery Mildew ◽

Large Subunit ◽

Morphological Characteristics ◽

Morphological Characterization ◽

Control Measures ◽

Width Ratio ◽

Infected Leaf ◽

Voucher Specimen ◽

First Report ◽

Pcr Products

Verbena bonariensis L., named as purple-top vervain or Argentinian vervain, is native to tropical South America. It is cultivated worldwide as an ornamental plant. During summer and autumn of 2020, over 50% of the leaves of V. bonariensis were found infected with powdery mildew in a flower garden in Seoul (37°35'19"N 127°01'07"E), Korea. White, superficial mycelia developed initially on the leaves and subsequently covered surfaces of leaves and stems, are resulting in leaf discoloration, early defoliation, and shoots distortion. Heavily infected plants lost ornamental value. A representative voucher specimen was deposited in the Korea University herbarium (KUS-F32168). Morphological characterization and measurements of conidiophores and conidia were carried out using fresh samples. Microscopic observation showed that aAppressoria on the superficial hypha were nipple-shaped, but rarely found or nearly absent. Conidiophores (n = 30) were cylindrical, 110 to 220 × 10 to 12 µm, and produced 2 to 5 immature conidia in chains with a sinuate outline, followed by 2 to 3 short cells. Foot-cells of conidiophores were straight, cylindrical, and 46 to 90 μm long. Conidia (n = 30) were hyaline, ellipsoid to doliiform, 28 to 40 × 18 to 24 μm with a length/width ratio of 1.3 to 2.0, and contained small be like oil-like drops, but without distinct fibrosin bodies. Primary conidia were apically rounded and sub-truncate at the base. Germ tubes were produced at perihilar position of the conidia. Chasmothecia were not observed. These morphological characteristics were typical of the conidial stage of the genus Golovinomyces (Braun and Cook 2012, Qiu et al. 2020). To identify the fungus, rDNA was extracted from the voucher sample. PCR products were amplified using the primer pair ITS1F/PM6 for internal transcribed spacer (ITS), and PM3/TW14 for the large subunit (LSU) of the rDNA (Takamatsu and Kano 2001). The resulting sequences were registered to GenBank (MW599742 for ITS, and MW599743 for LSU). Using Blast’n search of GenBank, sequences showed 100% identity for ITS and LSU with G. ambrosiae (MT355557, KX987303, MH078047 for ITS, and AB769427, AB769426 for LSU), respectively. Thus, based on morphology and molecular analysis, the isolate on V. bonariensis in Korea was identified as G. ambrosiae (Schwein.) U. Braun & R.T.A. Cook. Pathogenicity tests were carried out by touching an infected leaf onto healthy leaves of disease-free pot-grown plants using a replication of five plants, with five non-inoculated plants used as controls. After 7 days, typical powdery mildew colonies started to appear on the inoculated leaves. The fungus on inoculated leaves was morphologically identical to that originally observed in the field. All non-inoculated control leaves remained symptomless. On different global Verbena species, tThere have been many reports of Golovinomyces powdery mildews including G. cichoracearum s.lat., G. longipes, G. monardae, G. orontii s.lat., and G. verbenae (Farr and Rossman 2021). In China, G. verbenae was recorded on V.erbena phlogiflora (Liu et al. 2006). Golovinomyces powdery mildew has not been reported on Verbena spp. in Korea. Powdery mildew has been reported on V. bonariensis in California, but identity of the causal agent had not been reported. To our knowledge, this is the first report on the identity of the powdery mildew caused by G. ambrosiae on V. bonariensis in Korea. Since heavily infected plants lost ornamental value, appropriate control measures should be developed.

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First Report of Alternaria Brown Spot of Citrus Caused by Alternaria alternata in Yunnan Province, China

Plant Disease ◽

10.1094/pdis-94-3-0375c ◽

2010 ◽

Vol 94 (3) ◽

pp. 375-375 ◽

Cited By ~ 7

Author(s):

X. F. Wang ◽

Z. A. Li ◽

K. Z. Tang ◽

C. Y. Zhou ◽

L. Yi

Keyword(s):

Alternaria Alternata ◽

Yunnan Province ◽

Morphological Characteristics ◽

Control Measures ◽

Brown Spot ◽

Control Treatment ◽

Infected Leaf ◽

Conidial Suspension ◽

First Report ◽

Alternaria Brown Spot

Brown spot of citrus is considered a major problem on the fruit of many citrus cultivars grown for fresh markets including tangerines (Citrus reticulata) and their hybrids. It causes lesions on leaves, stems, and fruit and reduces yield and fruit quality (2). In 2003 in southern Wenshan Municipality, Yunnan Province in China, sporadic occurrence of Alternaria brown spot was observed on Tangfang mandarin, a local citrus cultivar identified preliminarily as a kind of mandarin hybrid. From 2006 to 2008, nearly 80% of local orchards were infected with the disease. Fruit symptoms typical of Alternaria brown spot ranging from light brown, slightly depressed spots to circular and dark brown areas were observed. Leaves showed small, brown, circular spots and irregular blighted areas with characteristic yellow halos. Tissues from the margin of fruit spots or infected leaf parts of eight different trees were surface sterilized in 1.5% sodium hypochlorite for 1 min, plated on potato dextrose agar (PDA), and then incubated at 27°C in the dark for 1 week. Dark brown mycelia and pigmented septate conidia with lengths of 10 to 35 μm and widths of 5 to 13 μm were produced. On the basis of conidial morphological characteristics, the pathogen was identified as Alternaria alternata (Fr.:Fr.) Keissl (1). Detached young healthy leaves of ‘Minneola’ tangelo (C. reticulata × C. paradisi) were sprayed with a conidial suspension of 105 conidia per ml and incubated in a moist chamber at 27°C. A control treatment with an equal number of leaves was sprayed with distilled water only. After 48 h, seven of these isolates caused necrotic lesions on detached leaves, characteristic of the disease, whereas there were no symptoms on leaves of the water control. Pure cultures were recovered on PDA from symptomatic tissues and the morphological characteristics of the conidia closely fit the description of A. alternata, confirming Koch's postulates. Currently, the distribution of Alternaria brown spot of citrus is confined to southern Wenshan Municipality in Yunnan Province where it is a serious disease problem on the most important commercial cultivar in this region. The identification of the pathogen now allows for appropriate field management and control measures. To our knowledge, this is the first report of Alternaria brown spot of citrus in China. References: (1) Z. Solel. Plant Pathol. 40:145, 1991. (2) J. O. Whiteside. Plant Dis. Rep. 60:326, 1976.

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First Report of a Bionectria sp. Associated with a Stem Rot of Cardon Cactus (Pachycereus pringlei) in Baja California Sur, Mexico

Plant Disease ◽

10.1094/pdis-08-11-0698 ◽

2012 ◽

Vol 96 (2) ◽

pp. 292-292 ◽

Cited By ~ 2

Author(s):

R. J. Holguín-Peña ◽

L. G. Hernández-Montiel ◽

H. Latisnere ◽

E. O. Rueda-Puente

Keyword(s):

Gulf Of California ◽

Baja California ◽

Morphological Characteristics ◽

Potato Dextrose Agar ◽

Control Measures ◽

World Heritage Site ◽

Stem Rot ◽

Baja California Sur ◽

First Report ◽

Pachycereus Pringlei

Giant cardon (Pachycereus pringlei ((S.Watson) Britton & Rose) is the most common cactus in northwestern Mexico and is endemic to the Baja California Peninsula and Sonora Desert. A large part of the peninsula (El Vizcaino Biosphere Reserve and Gulf of California) now consists of protected areas and is classified as a World Heritage site by UNESCO ( http://whc.unesco.org/en/list/1182 ). Cardon cactus is an important ecological resource for indigenous people and is used as feed for range cattle. Since 2000, in the central and southern part of the State of Baja California Sur, an apical stem rot has spread to ~17% of the natural cardon population around San Pedro (23°29′N, 110°12′W), La Paz (24°08′N, 110°18′W), and El Comitán (24°05′N, 110°21′W). Affected cacti display necrosis of apical branches, dry rot, cracks in the stem and branches, bronzing of mature spines surrounding the affected area, and reddish brown gummy exudate. Thirty samples from the edges of symptomatic lesions were surface disinfected for 2 min in 0.8% (wt/vol) NaOCl and ethanol (70%), rinsed in sterile, distilled water, and grown on potato dextrose agar at 27°C. A cottony, brownish fungus was consistently isolated from affected tissues. Koch's postulates were performed in pots of 10 cm in diameter with 5-year-old cacti inoculated (9-day-old mycelia) and incubated (15 days) at room temperature (26°C). The rough, dry, brownish, circular lesions that appeared were the same as those observed in the field. Healthy cacti inoculated with potato dextrose agar plugs were symptomless. The fungus was always reisolated from infected cacti and morphological examinations (2) were performed: one-septate, olive-green, smooth, ellipsoidal conidium and two-celled ascospores (15 to 20 × 5 to 7 μm) were present. Also present were conidial masses from monomorphic, penicillate conidiophores in sporodochia. Cottony and white-to-light yellow PDA colonies were observed. Genomic DNA was extracted from lyophilized hyphae using the method described by O'Donnell (1) or with a DNeasy Plant Mini Kit (Qiagen, Hilden, Germany). The internal transcribed spacer (ITS) regions 1 and 2 of the 5.8, 18, and 28S ribosomal RNA genes were amplified with the primer pairs ITS1 and ITS4 (3). The expected amplicon of 571 bp was sequenced and compared with fungal sequences available from the GenBank-EMBL database using the BlastN and CLUSTAL programs (MegAlign, DNASTAR, Madison, WI). The closest nucleotide similarity had 99% identity with a Bionectria sp. (GenBank Accession No. HM849058.1). To our knowledge, on the basis of morphological characteristics, DNA comparisons, and pathogenicity tests, this is the first report of a Bionectria sp. causing an apical stem rot disease in cardon cacti in Mexico. Since there are no control measures in Mexico there is a permanent risk that the disease will spread to healthy areas. References: (1) K. O'Donell et al. Mycologia 92:919, 2000. (2) H. J. Schroers. Stud. Mycol. 46:1, 2001. (3) T. J. White et al. PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, 1990.

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First Report of Late Blight Caused by Phytophthora infestans on Cape Gooseberry (Physalis peruviana) in Colombia

Plant Disease ◽

10.1094/pdis-91-4-0464b ◽

2007 ◽

Vol 91 (4) ◽

pp. 464-464 ◽

Cited By ~ 5

Author(s):

A. M. Vargas ◽

A. Correa ◽

D. C. Lozano ◽

A. González ◽

A. J. Bernal ◽

...

Keyword(s):

Late Blight ◽

Phytophthora Infestans ◽

Morphological Characteristics ◽

Control Measures ◽

Distilled Water ◽

First Report ◽

Physalis Peruviana ◽

Potato Slice ◽

Solanaceae Family ◽

Cape Gooseberry

Late blight caused by Phytophthora infestans is the most limiting disease for several species of the Solanaceae family in Colombia. A potential host for P. infestans is Cape gooseberry (Physalis peruviana), a species belonging to the Solanaceae family. Its center of origin is the highlands of Peru and it is grown at approximately 1,500 to 3,000 m above sea level. Cape gooseberry has become an important export fruit in Colombia. Consequently, in the last few years, the area cultivated with Physalis peruviana has increased dramatically. P. infestans was isolated from this crop in the province of Cundinamarca, Colombia. Symptoms caused by this oomycete appeared initially on the leaf margins as small, irregular, necrotic spots that expanded and merged, increasing the necrotic area. These spots had a soft texture resulting from the degradation of plant tissue by the pathogen. On old lesions, white mycelia and sporangia were observed. Affected plants were rarely killed, but under favorable conditions, severe symptoms were observed in leaves and yield was reduced. Ten isolates were obtained from infected tissue by placing a lesion directly on a potato slice in a moist chamber (2). Mycelia grown on the potato slice were then transferred to rye agar. Identification of the pathogen was performed based on morphological characteristics, specifically, sporangiophores of P. infestans are compoundly branched and develop sympodially, with swellings at the points where sporangia were attached (1). Further confirmation was obtained by sequencing the internal transcribed spacer (ITS) regions (GenBank Accession Nos. EF173467-EF173476). Koch's postulates were completed in the laboratory by spray inoculating detached leaves of Cape gooseberry with a zoospore suspension obtained from each of the 10 isolates. Inoculum was prepared by flooding 10-day-old cultures with sterile distilled water to obtain a 104/ml sporangial suspension followed by zoospore induction at 4°C. Leaves were sprayed with this suspension, placed in moist chambers, and incubated at 20°C in the dark. Control leaves were sprayed with sterile distilled water. Two separate leaves were inoculated with each isolate. The pathogen was reisolated from leaf lesions in all cases. The period between infection and the appearance of symptoms ranged from 5 to 7 days. To our knowledge, this is the first report of P. infestans causing damage on Cape gooseberry in Colombia. Chemical control measures are to some extent successfully applied in most regions where solanaceous crops are grown in Colombia. Nevertheless, suitable disease management for Physalis peruviana has not been achieved and further studies on the epidemiology of the disease on this new host are needed. References: (1) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society. St. Paul, MN, 1996. (2) G. A. Forbes et al. Phytopathology 87:375, 1997.

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First Report of a Canker Disease of Walnut Caused by Botryodiplodia theobromae in Egypt

Plant Disease ◽

10.1094/pdis-91-2-0226b ◽

2007 ◽

Vol 91 (2) ◽

pp. 226-226 ◽

Cited By ~ 4

Author(s):

W. M. Haggag ◽

M. S. M. Abou Rayya ◽

N. E. Kasim

Keyword(s):

Morphological Characteristics ◽

Fungal Growth ◽

Research Centre ◽

Botryodiplodia Theobromae ◽

Outer Bark ◽

Canker Disease ◽

First Report ◽

Plant Foliage ◽

Affected Tissue ◽

And Control

Botryodiplodia spp. are known to produce cankers and dieback of several woody hosts. Botryodiplodia diseases were observed in 7-year-old orchards in Rhafah, north of Sinai, Egypt, in July 2005 and 2006. Symptoms appeared as dieback and cankers with dead leaves that were covered mostly with grayish white fungal growth; black pycnidia appeared on the surface of the infected branches. Plant foliage was discolored and partially or completely dry. When the outer bark was removed, the affected tissue appeared dark brown, in contrast to the yellowish green of healthy inner bark. On the basis of morphological characteristics (3), these fungi were identified as Botryodiplodia theobromae Pat. by the Plant Pathology Department, National Research Centre. Sporulating lesions were black and had a rough surface caused by the erumpent, confluent arrangement of pycnidia formed in infected tissue. The pycnidia were smallest in naturally infected twigs in nutritionally rich medium such as oatmeal agar (190 to 887 × 155 to 705 μm). Conidia were initially hyaline and unicellular, subovoid to ellipsoidal with a granular content. Mature conidia were two-celled, cinnamon to light brown, and often with longitudinal striations. Conidia measured 20 to 30 × 12 to 15 μm. Pathogenicity of isolates from symptomatic branches was determined by branch inoculations on rooted cuttings made from 7-year-old walnut trees growing in plastic pots. One isolate was inoculated on wounded and unwounded twigs using 100 μl of a suspension of 5 × 105 conidia per ml. Control branches were sprayed with water. All inoculated and control plants were kept in a greenhouse and watered as needed. There were three replicate plants for each isolate and inoculation technique that was used. After 3 weeks, cankers and grayish necrotic lesions developed on all inoculated plants. Samples of tissue from 10 infected walnut branches were plated on water agar. B. theobromae was recovered from all sampled plants. Control plants did not display any symptoms. B. theobromae has been reported on species of walnut from the Hermosillo Coast of Mexico (1) and India (2). To our knowledge, this is the first report of walnut dieback and canker caused by this pathogen in Egypt. References: (1) J. A. Arredondo. Rev. Mex. Fitopatol. 12:138, 1994. (2) B. Kusum. Indian J. Mycol. Plant Pathol. 21:295, 1991. (3). S. Masilamani and J. Muthumary. Mycol. Res. 100:1383, 1996.

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First Report of Fusarium mangiferae Causing Mango Malformation in China

Plant Disease ◽

10.1094/pdis-12-11-1030 ◽

2012 ◽

Vol 96 (5) ◽

pp. 762-762 ◽

Cited By ~ 8

Author(s):

R.-L. Zhan ◽

S.-J. Yang ◽

F. Liu ◽

Y.-L. Zhao ◽

J.-M. Chang ◽

...

Keyword(s):

Mangifera Indica ◽

Elongation Factor ◽

Morphological Characteristics ◽

Fungal Growth ◽

Aerial Mycelium ◽

Laboratory Manual ◽

First Report ◽

Normal Number ◽

Mango Malformation ◽

Fusarium Mangiferae

Mango (Mangifera indica L.) malformation caused by Fusarium mangiferae has been reported in many mango-growing regions of the world (3). The disease was also observed in Yunnan and Sichuan provinces of China (1). Typical symptoms in seedlings included loss of apical dominance, hyperplasia and hypertrophy of vegetative buds, shortened internodes, and leaves that were more brittle than those of healthy plants. Inflorescences were abnormally branched and thickened, with panicles producing as much as two to five times the normal number of flowers. Flowers in the malformed inflorescence were much more enlarged and crowded than the generally hypertrophied axes of the panicle, thus producing no fruit or aborting early. To identify the pathogen, samples of malformed and healthy mango seedlings were collected from the affected plantings. For isolation, portions of stems were cut into 3- to 4-mm segments, surface disinfested, dried, and then plated on potato dextrose agar and incubated at 25°C. Within 5 days, white, fluffy, aerial mycelium developed. With the aid of an inverted microscope, single conidia were transferred to carnation leaf agar (CLA) medium. After 10 days of incubation, morphological characteristics were found to be identical to those of F. mangiferae (4). Aerial mycelium was white with no pigmentation observed on potato sucrose agar. Pigmentation on rice medium was pink. On CLA medium, conidia grew in branched conidiophores with false heads bearing monophialides or polyphialides. No conidiospores in chains were observed. Microconidia were ovate to long and oval, 0 to 1 septate, and 3.1 to 10.2 × 1.5 to 2.2 μm. Macroconidia are falculate, 3 to 5 septate, and 18 to 38 × 1.8 to 2.4 μm. Chlamydospores were not observed. Pathogenicity studies were conducted with 7-month-old asymptomatic mango seedlings. These seedlings, except for the controls, were inoculated by injection of the isolated fungus in the axillary or apical bud position. A 1-ml spore suspension (1 × 106 spores/ml) was injected slowly into the stems using a microsyringe with three buds per seedling, for a total of 10 seedlings. Typical malformation symptoms developed within 3 to 4 months, and none of the plants inoculated with sterile water resulted in malformation symptoms. Reisolations from the induced malformed shoots yielded the same fungus, and no fungal growth was observed to be growing from the control plants. To confirm identity of the causal fungus, the gene encoding translation elongation factor 1 alpha (EF-1α) was amplified and sequenced (2). The EF-1α sequence was 660 bp long. The sequence (GenBank Accession No. HM068871) was 99.68% similar to sequences of FD_01167 in the Fusarium ID database. On the basis of symptoms, fungal morphology, the EF-1α region sequence, and pathogenicity testing, this fungus was identified as F. mangiferae. To our knowledge, this is the first report of F. mangiferae causing mango malformation in China. This report will establish a foundation for further study of F. mangiferae and effectively addressing the disease. References: (1) X. H. Chen. Pract. Technol. (in Chinese) 6:5, 1992. (2) D. M. Geiser et al. Eur. J. Plant Pathol. 110:473, 2004. (3) J. Kumar et al. Annu. Rev. Phytopathol. 31:217, 1993. (4) J. F. Leslie and B. A. Summerell. The Fusarium Laboratory Manual. Blackwell Publishing, Ames, IA, 2006.

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First Report of Cherry Stem Rot and Leaf Necrosis Disease Caused by Phytophthora nicotianae in Yantai, China

Plant Disease ◽

10.1094/pdis-05-14-0489-pdn ◽

2015 ◽

Vol 99 (2) ◽

pp. 284-284

Author(s):

X. L. Yu ◽

X. Q. Liu ◽

P. S. Wang ◽

Y. Z. Wang

Keyword(s):

Average Length ◽

Morphological Characteristics ◽

Its Region ◽

Phytophthora Species ◽

Phytophthora Nicotianae ◽

Control Measures ◽

Stem Rot ◽

Economic Losses ◽

First Report ◽

Leaf Necrosis

Cherry (Cerasus avium (Linn.) Moench) is the third most economically important fruit in Yantai, Shandong Province, China. In August 2012, brown spots or necrosis on cherry seedling leaves, with an incidence of 8.2 to 34.3%, were observed in some fields of cherry seedlings in Yantai. Our survey indicated that the economic losses could reach up to 15.3% if disease conditions, such as a cool rainy summer season, were favorable. Conspicuous watery lesions on the stems turned to brown streaks; the leaves all wilted; and finally the plants collapsed. Diseased stem and leaf samples were surface-disinfected in 1% sodium hypochlorite for 1 min, rinsed three times in sterile water, which was absorbed with filter paper, and then transferred to 10% V8 juice agar medium containing 50 μg/ml ampicillin and 5 μg/ml carbendazim (1). The plates were incubated at 22°C in the dark for 5 days. The colonies consisted of white, loose, fluffy aerial mycelia. Eight isolates were obtained, and all were identified as Phytophthora nicotianae based on morphological characteristics and the sequence of the internal transcribed spacer (ITS) region of rDNA. The sporangia were ovoid/spherical, obturbinate with rounded bases and prominent papillae that were 37.5 to 62.5 × 30 to 50 μm (average 46.4 × 37.8 μm, n = 100) in size, with an average length-to-breadth ratio of 1.2. Chlamydospores were terminal, intercalary, and measured 19 to 42 μm (average 30.4 μm), which is typical of P. nicotianae (2). The genomic DNA of the eight isolates was extracted from mycelia. The ITS region of all eight isolates was amplified using primers ITS1 and ITS4, producing specific products that were directly sequenced. The sequence of a representative isolate P1401 (895 bp) was submitted to GenBank (Accession No. KJ754387). It was 100% similar to P. nicotianae strains NV-20T and TARI 22073 (KC768775 and GU111667). To confirm the pathogenicity, at least 10 cherry leaves and new stems were inoculated with mycelial plugs (5 × 5 mm) from each isolate. Necrosis of leaves and stems was observed 4 and 7 days after inoculation, respectively. No symptoms were observed on the control leaves and stems that were inoculated with blank agar plugs. P. nicotianae was re-isolated from the infected leaves, and the ITS sequence was analyzed to confirm its identity. Phytophthora species, such as P. cambivora, P. megasperma, and P. drechsleri, had been previously isolated from cherry (3), but to the best of our knowledge this is the first report of stem rot and leaf necrosis disease caused by P. nicotianae on cherry. Since the economic loss caused by this disease could reach 15% if an outbreak occurred in a rainy summer, control measures should be implemented. References: (1) Y. Balci et al. Mycol. Res. 112:906, 2008. (2) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society, St Paul, MN, 1996. (2) S. M. Mircetich and M. E. Matheron. Phytopathology 66:549, 1976.

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