First Report of Stem Rot of Papaya Caused by Fusarium solani Species Complex in Brazil

In October 2010, 2-year-old papaya (cv. Hawaii) trees with high incidence of stem rot were observed during a survey conducted in Rio Grande do Norte state, northeastern Brazil. Stems showing reddish brown-to-dark brown symptoms were collected and small pieces (4 to 5 mm) of necrotic tissues were surface sterilized for 1 min in 1.5% NaOCl, washed twice with sterile distilled water, and plated onto potato dextrose agar (PDA) amended with 0.5 g liter–1 streptomycin sulfate. Plates were incubated at 25°C with a 12-h photopheriod for 4 days. Pure cultures with white, fluffy aerial mycelia were obtained by subculturing hyphal tips onto PDA. Identification was made using morphological characteristics and DNA based molecular techniques. Colonies grown on PDA and Spezieller Nährstoffarmer agar (SNA) for 10 days at 25°C with a 12-h photoperiod were used for morphological identification (3). The fungus produced cream sporodochia and two types of spores: microconidia were thin-walled, hyaline, ovoid, one-celled, and 6.8 to 14.6 × 2.3 to 4.2 μm; macroconidia were thick walled, hyaline, slightly curved, 3- to 5-celled, and 25.8 to 53.1 × 3.9 to 5.7 μm. Fifty spores of each type were measured. Rounded, thick-walled chlamydospores were produced, with two to four arranged together. On the basis of morphological characteristics (1), three fungal isolates (CMM-3825, CMM-3826, and CMM-3827) were identified as Fusarium solani (Mart.) Sacc. and were deposited in the Culture Collection of Phytopathogenic Fungi of the Universidade Federal Rural de Pernambuco (Recife, Brazil). Single-spore isolates were obtained and genomic DNA of the isolates was extracted and a portion of the translation elongation factor 1-alpha (EF1-α) gene of the isolates was amplified and sequenced (2). When compared with sequences available in the GenBank and Fusarium-ID databases, DNA sequences of the three isolates shared 99 to 100% sequence identity with F. solani species complex (GenBank Accession Nos. JF740784.1, DQ247523.1, and DQ247017.1). Representative sequences of the isolates were deposited in GenBank (Accession Nos. JQ808499, JQ808500, and JQ808501). Pathogenicity tests were conducted with four isolates on 3-month-old papaya (cv. Hawaii) seedlings. Mycelial plugs taken from the margin of actively growing colonies (PDA) of each isolate were applied in shallow wounds (0.4 cm in diameter) on the stem (center) of each plant. Inoculation wounds were wrapped with Parafilm. Control seedlings received sterile PDA plugs. Inoculated and control seedlings (10 each) were kept in a greenhouse at 25 to 30°C. After 2 weeks, all inoculated seedlings showed reddish brown necrotic lesions in the stems. No symptoms were observed in the control plants. The pathogen was successfully reisolated from symptomatic plants to fulfill Koch's postulates. To our knowledge, this is the first report of F. solani species complex causing papaya stem rot in Brazil. Papaya is an important fruit crop in the northeastern Brazil and the occurrence of this disease needs to be taken into account in papaya production. References: (1) C. Booth. Fusarium Laboratory Guide to the Identification of the Major Species. CMI, Kew, England, 1977. (2) D. M. Geiser et al. Eur. J. Plant Pathol. 110:473, 2004. (3) J. F. Leslie and B. A. Summerell. The Fusarium Laboratory Manual. Blackwell Publishing, Ames, IA, 2006.

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First report of Fusarium falciforme (FSSC 3+4) causing root rot on chickpea in Mexico

Plant Disease ◽

10.1094/pdis-05-21-1123-pdn ◽

2021 ◽

Author(s):

Sixto Velarde Felix ◽

Victor Valenzuela ◽

Pedro Ortega ◽

Gustavo Fierros ◽

Pedro Rojas ◽

...

Keyword(s):

Fusarium Solani ◽

Root Rot ◽

Species Complex ◽

Elongation Factor ◽

Morphological Characteristics ◽

Aerial Mycelium ◽

Pathogenicity Test ◽

Conidial Suspension ◽

Single Spore ◽

First Report

Chickpea (Cicer aretinium L.) is a legume crop of great importance worldwide. In January 2019, wilting symptoms on chickpea (stunted grow, withered leaves, root rot and wilted plants) were observed in three fields of Culiacan Sinaloa Mexico, with an incidence of 3 to 5%. To identify the cause, eighty symptomatic chickpea plants were sampled. Tissue from roots was plated on potato dextrose agar (PDA) medium. Typical Fusarium spp. colonies were obtained from all root samples. Ten pure cultures were obtained by single-spore culturing (Ff01 to Ff10). On PDA the colonies were abundant with white aerial mycelium, hyphae were branched and septae and light purple pigmentation was observed in the center of old cultures (Leslie and Summerell 2006). From 10-day-old cultures grown on carnation leaf agar medium, macroconidias were falciform, hyaline, with slightly curved apexes, three to five septate, with well-developed foot cells and blunt apical cells, and measured 26.6 to 45.8 × 2.2 to 7.0 μm (n = 40). The microconidia (n = 40) were hyaline, one to two celled, produced in false heads that measured 7.4 to 20.1 (average 13.7) μm × 2.4 to 8.9 (average 5.3) μm (n = 40) at the tips of long monophialides, and were oval or reniform, with apexes rounded, 8.3 to 12.1 × 1.6 to 4.7 μm; chlamydospores were not evident. These characteristics fit those of the Fusarium solani (Mart.) Sacc. species complex, FSSC (Summerell et al. 2003). The internal transcribed spacer and the translation elongation factor 1 alpha (EF1-α) genes (O’Donnell et al. 1998) were amplified by polymerase chain reaction and sequenced from the isolate Ff02 and Ff08 (GenBank accession nos. KJ501093 and MN082369). Maximum likelihood analysis was carried out using the EF1-α sequences (KJ501093 and MN082369) from the Ff02 and Ff08 isolates and other species from the Fusarium solani species complex (FSSC). Phylogenetic analysis revealed the isolate most closely related with F. falciforme (100% bootstrap). For pathogenicity testing, a conidial suspension (1x106 conidia/ml) was prepared by harvesting spores from 10-days-old cultures on PDA. Twenty 2-week-old chickpea seedlings from two cultivars (P-2245 and WR-315) were inoculated by dipping roots into the conidial suspension for 20 min. The inoculated plants were transplanted into a 50-hole plastic tray containing sterilized soil and maintained in a growth chamber at 25°C, with a relative humidity of >80% and a 12-h/12-h light/dark cycle. After 8 days, the first root rot symptoms were observed on inoculating seedlings and the infected plants eventually died within 3 to 4 weeks after inoculation. No symptoms were observed plants inoculated with sterilized distilled water. The fungus was reisolated from symptomatic tissues of inoculated plants and was identified by sequencing the partial EF1-α gene again and was identified as F. falciforme (FSSC 3 + 4) (O’Donnell et al. 2008) based on its morphological characteristics, genetic analysis, and pathogenicity test, fulfilling Koch’s postulates. The molecular identification was confirmed via BLAST on the FusariumID and Fusarium MLST databases. Although FSSC has been previously reported causing root rot in chickpea in USA, Chile, Spain, Cuba, Iran, Poland, Israel, Pakistan and Brazil, to our knowledge this is the first report of root rot in chickpea caused by F. falciforme in Mexico. This is important for chickpea producers and chickpea breeding programs.

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Molecular phylogeny of the Fusarium solani species complex (FSSC) isolated from soils in Iran

Botany ◽

10.1139/cjb-2014-0096 ◽

2014 ◽

Vol 92 (11) ◽

pp. 815-820 ◽

Cited By ~ 2

Author(s):

Khosrow Chehri

Keyword(s):

Dna Sequences ◽

Fusarium Solani ◽

Species Complex ◽

Agricultural Soils ◽

Sequence Data ◽

Morphological Characteristics ◽

Taxonomic Status ◽

Its Region ◽

Phylogenetic Study ◽

Fusarium Solani Species Complex

Members of Fusarium solani species complex (FSSC) are frequently isolated from soils, food, feeds, trees, and to some extent from humans and other animals. The taxonomic status of these fungi is being revised but no attempt has been made to identify those isolated in Iran, a mountainous country with a high biodiversity. The objective of the present research was to study the phylogenetic diversity of FSSC strains recovered from soils in Iran by analyzing morphological characteristics and DNA sequences. A total of 65 strains belonging to the FSSC were recovered from agricultural soils in western Iran. Based on differences in their morphological characters, 25 strains were selected for phylogenetic analysis employing translation elongation factor-1α (tef1) and internal transcribed spacer (ITS) region sequences. Comparisons of DNA sequence data revealed that all isolates belonged to Fusarium falciforme, Fusarium keratoplasticum, Fusarium petroliphilum, the unnamed species FSSC 5, and unknown species of Fusarium, which represents a new lineage within members of Clade 3. Based on morphological features and phylogenetic study, F. keratoplasticum and F. petroliphilum were reported for the first time in Iran.

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First Report of Tuber Rot Disease of Kala Zeera Caused by a Member of the Fusarium solani Species Complex in India

Plant Disease ◽

10.1094/pdis-02-12-0148-pdn ◽

2012 ◽

Vol 96 (7) ◽

pp. 1067-1067 ◽

Cited By ~ 1

Author(s):

V. Gupta ◽

D. John ◽

V. K. Razdan ◽

S. K. Gupta

Keyword(s):

Fusarium Solani ◽

Species Complex ◽

Morphological Characteristics ◽

Distilled Water ◽

Conidial Suspension ◽

Potato Dextrose Broth ◽

First Report ◽

Fusarium Solani Species Complex ◽

Rot Disease ◽

Tuber Rot

Bunium persicum (Kala zeera, also black cumin) is an economically important culinary crop that is cultivated for its seed pods and its tuberlike roots. In India, high-altitude regions of Himachal Pradesh, including the Padder valley and the Gurez area of Jammu and Kashmir, are areas of kalazeera production (3). In 2008 to 2009, tuber rot disease of kala zeera was observed during the late spring season in the Padder valley. Symptomatic plants were distributed in localized areas in the field and the symptoms included drying of foliage and rotting of tubers. White mycelia were found on the tubers at the late stages of disease development. Incidence of infection in the surveyed area was 80 to 90%. Yield losses were 50 to 60%. To isolate the causal pathogen, we cultured tissues from symptomatic tubers. Small bits of the infected tissue were surface disinfested in 0.1% mercuric chloride, followed by rinsing three times in sterile distilled water. The surface disinfested tissues were plated on potato dextrose agar (PDA) and incubated at 27°C for 4 days. Pure cultures of the mycelium from the diseased tissues were transferred to a second set of PDA for species identification. The fungus produced three types of spores: small, one-celled, oval microconidia; large, slightly curved, septate macroconidia; and rounded, thick-walled chlamydospores. Microconidia were mostly non-septate and 8.91 to 15.73 × 2.3 to 3.5 μm, whereas macroconidia were three- to five-septate and were 35.55 to 54.74 × 3.91 to 6.5 μm. On the basis of morphological characteristics (1), the fungus was identified and deposited as a member of the Fusarium solani species complex in the Indian Type Culture Collection, New Delhi (ID No. 8422.11). To confirm pathogenicity, healthy tubers were submerged for 20 min in a conidial suspension of the isolated fungus (1 × 105 cfu/ml), which was prepared in potato dextrose broth, incubated for 10 days at 27°C, and centrifuged at 140 rpm. Noninoculated controls were submerged in distilled water. Inoculated and control tubers were then planted in separate pots filled with sterilized soil and kept in a shade house. Symptoms appeared on inoculated tubers 9 to 10 days after planting. Signs of the pathogen in the form of mycelia were present. The tubers rotted and died 12 to 15 days after inoculation. Control tubers did not display any symptoms. F. solani species complex was reisolated from inoculated tubers, fulfilling Koch's postulates. F. solani has been reported to cause corm rot on gladiolus and saffron (2). To our knowledge, this is the first report of the F. solani species complex as pathogenic to tubers of kalazeera in India. References: (1) C. Booth. The Genus Fusarium. 47, 1971. (2) L. Z. Chen et al. J. Shanghai Agric. College 12:240, 1994. (3) K. S. Panwar et al. Agriculture Situation in India. 48:151, 1993.

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First Report of Mango Dieback Caused by Pseudofusicoccum stromaticum in Brazil

Plant Disease ◽

10.1094/pdis-05-11-0425 ◽

2012 ◽

Vol 96 (1) ◽

pp. 144-144 ◽

Cited By ~ 8

Author(s):

M. W. Marques ◽

N. B. Lima ◽

S. J. Michereff ◽

M. P. S. Câmara ◽

C. R. B. Souza

Keyword(s):

Uv Light ◽

Mangifera Indica ◽

Morphological Characteristics ◽

Pcr Amplification ◽

Molecular Techniques ◽

Northeastern Brazil ◽

Universal Primers ◽

Rrna Gene ◽

First Report ◽

Length Width

From September to December 2010, mango (Mangifera indica L.) stems showing dieback symptoms were collected during a survey conducted in São Francisco Valley, northeastern Brazil. Small pieces (4 to 5 mm) of necrotic tissues were surface sterilized for 1 min in 1.5% NaOCl, washed twice with sterile distilled water, and plated onto potato dextrose agar (PDA) amended with 0.5 g liter–1 streptomycin sulfate. Plates were incubated at 25°C in the dark for 14 to 21 days and colonies that were morphologically similar to species of Botryosphaeriaceae were transferred to PDA. Colonies developed a compact mycelium that was initially white, but becoming gray dark after 4 to 6 days of incubation at 25°C in darkness. Identification was made using morphological characteristics and DNA based molecular techniques. Pycnidia were obtained on 2% water agar with sterilized pine needles as substratum after 3 weeks of incubation at 25°C under near-UV light. Pycnidia were large, multilocular, eustromatic, covered with hyphae; locule totally embedded without ostioles, locule walls consisting of a dark brown textura angularis, becoming thinner and hyaline toward the conidiogenous region. Conidia were hyaline, thin to slightly thickened walled, aseptate, with granular contents, bacilliform, straight to slightly curved, apex and base both bluntly rounded or just blunt, 15.6 to 25.0 (20.8) μm long, and 2.7 to 7.9 (5.2) μm wide, length/width = 4.00. According to these morphological characteristics, three isolates (CMM1364, CMM1365, and CMM1450) were identified as Pseudofusicoccum stromaticum (1,3,4). PCR amplification by universal primers (ITS4/ITS5) and DNA sequencing of the internal transcribed spacer (ITS1-5.8S-ITS2 rRNA gene cluster) were conducted to confirm the identifications through BLAST searches in GenBank. The isolates were 100% homologous with P. stromaticum (3) (GenBank Accession Nos. AY693974 and DQ436935). Representative sequences of the isolates were deposited in GenBank (Accession Nos. JF896432, JF966392, and JF966393). Pathogenicity tests were conducted with the P. stromaticum strains on 5-month-old mango seedlings (cv. Tommy Atkins). Mycelial plugs taken from the margin of actively growing colonies (PDA) of each isolate were applied in shallow wounds (0.4 cm in diameter) on the stem (center) of each plant. Inoculation wounds were wrapped with Parafilm. Control seedlings received sterile PDA plugs. Inoculated and control seedlings (five each) were kept in a greenhouse at 25 to 30°C. After 5 weeks, all inoculated seedlings showed leaf wilting, drying out of the branches, and necrotic lesions in the stems. No symptoms were observed in the control plants. P. stromaticum was successfully reisolated from symptomatic plants to fulfill Koch's postulates. P. stromaticum was described from Acacia, Eucalyptus, and Pinus trees in Venezuela (3,4), and there are no reports of this fungus in other hosts (2). To our knowledge, this is the first report of P. stromaticum causing mango dieback in Brazil and worldwide. References: (1) P. W. Crous et al. Stud. Mycol. 55:235, 2006. (2) D. F. Farr and A. Y. Rossman. Fungal Databases. Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ , 18 May 2011. (3) S. Mohali et al. Mycol. Res. 110:405, 2006. (4) S. R. Mohali et al. Fungal Divers. 25:103, 2007.

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First Report of Anthracnose Fruit Rot Caused by Colletotrichum fioriniae on Litchi in China

Plant Disease ◽

10.1094/pdis-07-20-1539-pdn ◽

2020 ◽

Author(s):

Jin-Feng Ling ◽

Aitian Peng ◽

Zide Jiang ◽

Pinggen Xi ◽

Xiaobing Song ◽

...

Keyword(s):

Species Complex ◽

Morphological Characteristics ◽

Morphological Characterization ◽

Fruit Rot ◽

Single Spore ◽

Potential Threat ◽

First Report ◽

Fruit Cracking ◽

Pure Cultures ◽

Colletotrichum Spp

Anthracnose fruit rot of litchi (Litchi chinensis Sonn.), caused by Colletotrichum spp., has been mainly associated with the C. acutatum species complex and C. gloeosporioides species complex (Farr and Rossman 2020). In June 2010, isolates of the C. acutatum species complex were isolated together with the C. gloeosporioides species complex from anthracnose lesions on litchi fruits (cv. Nuomici) obtained from a litchi orchard in Shenzhen (N 22.36°, E 113.58°), China. The symptoms typically appeared as brown lesions up to 25 mm in diameter, causing total fruit rot and sometimes fruit cracking. Based on the number of isolates we collected, the C. acutatum species complex appears less frequently on infected fruit compared to the C. gloeosporioides species complex. Since only the C. gloeosporioides species complex has been reported in China (Qi 2000; Ann et al. 2004), we focused on the C. acutatum species complex in this study. Pure cultures of fungal isolates were obtained by single-spore isolation. The isolate GBLZ10CO-001 was used for morphological characterization, molecular and phylogenetic analysis, and pathogenicity testing. Colonies were cultured on potato dextrose agar (PDA) at 25 ℃ for 7 days, circular, raised, cottony, gray or pale orange, with reverse carmine, and 39.6 to 44.7 mm in diameter. Conidia were 13.5 to 19 × 4 to 6 µm (mean ± SD = 15.9 ± 1.1 × 5.2 ± 0.3 µm, n = 50) in size, hyaline, smooth-walled, aseptate, straight, fusiform to cylindrical with both ends acute. Appressoria were 5.5 to 13.5 × 4.5 to 7.5 µm (mean ± SD = 7.6 ± 1.6 × 6.0 ± 0.7 µm, n = 50) in size, subglobose to elliptical, sometimes clavate or irregular, smooth-walled, with entire edge, sometimes undulate, pale to medium brown. These morphological characteristics were consistent with the descriptions of several Colletotrichum species belonging to the C. acutatum species complex, including C. fioriniae (Shivas and Tan 2009; Damm et al. 2012). For molecular identification, genomic DNA was extracted and the ribosomal internal transcribed spacer (ITS), partial sequences of the β-tubulin (TUB2), actin (ACT), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), chitin synthase 1 (CHS-1), and histone3 (HIS3) genes were amplified and sequenced using the primer pairs ITS4/ITS5, T1/Bt2b, ACT512F/ACT783R, GDF1/GDR1, CHS-79F/CHS-354R, and CYLH3F/CYLH3R, respectively (White et al. 1990; Damm et al. 2012). The resulting sequences were submitted to GenBank (ITS: MN527186, TUB2: MT740310, ACT: MN532321, GAPDH: MN532427, CHS-1: MT740311, HIS3: MT740312). BLAST searches showed 98.70%-100% identity to the sequences of the C. fioriniae ex-holotype culture CBS 128517. The phylogram reconstructed from the combined dataset using MrBayes 3.2.6 (Ronquist et al. 2012) showed that isolate GBLZ10CO-001 clustered with C. fioriniae with high posterior probability. Koch’s postulates were performed in the field to confirm pathogenicity. Isolate GBLZ10CO-001 was grown on PDA (25 ℃ for 7 days) to produce conidia. In June 2014, litchi fruits (cv. Nuomici) were sprayed with conidial suspensions (106 conidia/ml), with sterile water as blank controls, and each treatment inoculated at least 15 fruits. Inoculated fruits were covered by an adhesive-bonded fabric bag until the trial ended. After 31 days, typical symptoms were observed, while control fruits remained asymptomatic. The fungus was re-isolated from diseased fruits and identified as C. fioriniae according to the methods described above. To our knowledge, this is the first report of anthracnose fruit rot on litchi caused by C. fioriniae, one species of the C. acutatum species complex, in China. For the difficulty in distinguishing anthracnose caused by C. fioriniae from the C. gloeosporioides species complex just by the symptoms, and mixed infection usually occurring in the field, further investigations are required to reliably assess the potential threat posed by C. fioriniae for litchi production in China.

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First Report of Seedling Blight of Oat (Avena sativa) Caused by Microdochium nivale in China

Plant Disease ◽

10.1094/pdis-10-19-2139-pdn ◽

2020 ◽

Author(s):

Hao Chen ◽

Gui Qiao Liu ◽

Longhai Xue ◽

Chunjie Li ◽

Guiqin Zhao ◽

...

Keyword(s):

Rna Polymerase Ii ◽

Dna Sequences ◽

Avena Sativa ◽

Morphological Characteristics ◽

Gansu Province ◽

Microdochium Nivale ◽

Seedling Blight ◽

Single Spore ◽

First Report ◽

Millet Seed

Oat (Avena sativa) is extensively planted as a fodder crop on the vast ranges of northern and northwestern China, and it has become an important supplementary feed for grazing livestock (Yang et al. 2010). Microdochium nivale has been reported associated with seedling blight in many temperate regions (Imathiu et al. 2010) and the damage can result in serious loss of oat production. In August 2018, a serious seedling blight of oat (cv. Baiyan 7; about 30-day-old) was observed in the field in Shandan County, Zhangye City, Gansu Province (38.22° N, 101.22° E). More than 20% of oat plants were severely affected. Symptoms included leaf chlorosis and wilt. The root systems of infected plants were black and severely rotted, often with only a small amount of fine root remaining after removal from the soil. Twenty isolations were made from blackened roots on potato dextrose agar (PDA) and five isolations (TM-1, TM-2, TM-3, TM-4 and TM-5) were further purified by a single-spore method (Choi et al. 1999). Each isolate was identical based on preliminary molecular analyses of their DNA sequences of ITS by blast in the NCBI GenBank. The representative isolate TM-2 was selected for sequencing of the RNA polymerase II subunit (RPB2) gene. The isolated colonies were grown on PDA and formed colonies of approximately 62 mm (diameter) in 5 days at 25 ± 1 °C. Colonies exhibited entire margins, the color varied from white to pale yellow, and the sparse aerial mycelium were villous-floccose and cottony. The conidia were falcate, straight to curved, apex pointed or obtuse to subacute, lacking basal differentiation, 0-3-septate, most one-septate, 2.2 to 3.1 × 12.3 to 22.6μm (av.= 2.8 ×17.6; n=50). These morphological characteristics were consistent with previous descriptions of Microdochium (Zhang et al. 2010). Molecular identity was confirmed by sequencing partial sequences of ITS gene (ITS1 and ITS4 primers) (White et al. 1990) and RPB2 regions (RPB2-5f2 and RPB2-7cr) (O’Donnell et al. 2010). Sequences were deposited in GenBank under accessions MN428647 (RPB2) and MN428646 (ITS). Blast search revealed that both of the ITS and RPB2 sequences to be 99% similar to the corresponding sequences of M. nivale(CBS 116205) accession numbers KP859008.1 and KP859117.1. For pathogenicity tests, millet seed-based inoculum of M. nivale was prepared using a modified procedure of Fang et al. (2011). Three-week-old healthy oat seedlings of cv. Baiyan 7 were transplanted into potting mix containing millet seed-based inoculum of M. nivale at a rate of 3%. Control seedlings for comparison were transplanted into pots containing uninoculated potting mix. After 10 days, all the inoculated plants had developed seedling blight symptoms and that were similar to those observed in the field; while control plants remained healthy. The pathogen was reisolated from inoculated plants and identified as M. nivale based on morphological characteristics and the molecular methods described above. To our knowledge, this is the first report of seedling blight of oat caused by M. nivale in China.

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First Report of Zucchini Collapse by Fusarium solani f. sp. cucurbitae Race 1 and Plectosporium tabacinum in Italy

Plant Disease ◽

10.1094/pdis-91-3-0325a ◽

2007 ◽

Vol 91 (3) ◽

pp. 325-325 ◽

Cited By ~ 7

Author(s):

S. Vitale ◽

M. Maccaroni ◽

A. Belisario

Keyword(s):

Fusarium Solani ◽

Fusarium Species ◽

Morphological Characteristics ◽

Its Region ◽

Conidial Suspension ◽

Single Spore ◽

Running Water ◽

First Report ◽

Race 1 ◽

Rot Disease

Zucchini plant collapse has been often associated with Fusarium solani f. sp. cucurbitae race 1, which is the causal agent of Fusarium crown and foot rot disease of cucurbits. In Italy, F. solani f. sp. cucurbitae race 1 has been reported on zucchini (Cucurbita pepo) in a greenhouse in the Tuscany Region (4). In spring 2005, a severe outbreak was observed on zucchini in a vast area of cultivation in the province of Venice. Isolations from necrotic vessels gave more than 20 single-spore cultures. On the basis of morphological characteristics, they were identified as F. solani (2) and Plectosporium tabacinum (3). The internal transcribed spacer (ITS) region of rDNA was amplified and sequenced. A fragment of 454 and 531 bp was 99% homologous with sequence PSU66732 and AF150472 of F. solani f. sp. cucurbitae race 1 and P. tabacinum, respectively, in the NCBI database. The nucleotide sequences have been assigned Accession No. AM408782 for F. solani f. sp. cucurbitae race 1 and AM408781 for P. tabacinum. Pathogenicity tests were conducted with four isolates of each species on 15-day-old zucchini plants and on fruit. Plants were inoculated by dipping the roots in a conidial suspension of 106 spores ml-1 for 10 min. Control plants were dipped in sterile water. Five replicates for the inoculated and control plants were used. All plants were maintained in a greenhouse at approximately 24°C. After 14 days, inoculations with F. solani f. sp. cucurbitae race 1 gave symptoms of a cortical rot at the base of the stem with a progressive yellows and wilting of leaves, while plants inoculated with P. tabacinum displayed a moderate wilting. Fruit were washed under running water, disinfected with a solution of 3% sodium hypochlorite and 5% ethanol for 1 min, and inoculated with 6-mm-diameter mycelial plugs cut from the margin of 10-day-old cultures grown on PDA. Plugs were inserted into holes (approximately 2 mm deep) made with a sterile 7-mm-diameter cork borer. Five replicates per isolate were used. Fruit were kept at room temperature (22 to 24°C) in a moist chamber. All isolates induced symptoms of fruit rotting 10 days after inoculation. All controls remained healthy. The colonies reisolated from the inoculated plants and fruit were morphologically identical to the original isolates. The results obtained proved that F. solani f. sp. cucurbitae race 1 can be considered the major pathogen in zucchini collapse, at the same time P. tabacinum may play a role in this syndrome as reported for other cucurbits (1). To our knowledge, this is the first report of zucchini plant collapse caused by F. solani f. sp. cucurbitae race 1 and P. tabacinum, and the first report of P. tabacinum on zucchini in Italy. References: (1) V. J. Garcia-Jimenez et al. EPPO Bull. 30:169, 2000. (2) P. E. Nelson et al. Fusarium Species: An Illustrated Manual for Identification. Pennsylvania State University, University Park, 1983. (3) M. E. Palm et al. Mycologia 87:397, 1995. (4) G. Vannacci and P. Gambogi. Phytopathol. Mediterr. 19:103, 1980.

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First Report of Leaf Blight of Japanese Yew Caused by Pestalotiopsis microspora in Korea

Plant Disease ◽

10.1094/pdis-08-13-0821-pdn ◽

2014 ◽

Vol 98 (5) ◽

pp. 691-691 ◽

Cited By ~ 2

Author(s):

Y. H. Jeon ◽

W. Cheon

Keyword(s):

Dna Sequences ◽

Apical Cell ◽

Morphological Characteristics ◽

Leaf Blight ◽

Economic Damage ◽

Leaf Margin ◽

Conidial Suspension ◽

First Report ◽

Pestalotiopsis Microspora ◽

Large Trees

Worldwide, Japanese yew (Taxus cuspidata Sieb. & Zucc.) is a popular garden tree, with large trees also being used for timber. In July 2012, leaf blight was observed on 10% of Japanese yew seedling leaves planted in a 500-m2 field in Andong, Gyeongsangbuk-do Province, South Korea. Typical symptoms included small, brown lesions that were first visible on the leaf margin, which enlarged and coalesced into the leaf becoming brown and blighted. To isolate potential pathogens from infected leaves, small sections of leaf tissue (5 to 10 mm2) were excised from lesion margins. Eight fungi were isolated from eight symptomatic trees, respectively. These fungi were hyphal tipped twice and transferred to potato dextrose agar (PDA) plates for incubation at 25°C. After 7 days, the fungi produced circular mats of white aerial mycelia. After 12 days, black acervuli containing slimy spore masses formed over the mycelial mats. Two representative isolates were further characterized. Their conidia were straight or slightly curved, fusiform to clavate, five-celled with constrictions at the septa, and 17.4 to 28.5 × 5.8 to 7.1 μm. Two to four 19.8- to 30.7-μm-long hyaline filamentous appendages (mostly three appendages) were attached to each apical cell, whereas one 3.7- to 7.1-μm-long hyaline appendage was attached to each basal cell, matching the description for Pestalotiopsis microspora (2). The pathogenicity of the two isolates was tested using 2-year-old plants (T. cuspidata var. nana Rehder; three plants per isolate) in 30-cm-diameter pots filled with soil under greenhouse conditions. The plants were inoculated by spraying the leaves with an atomizer with a conidial suspension (105 conidia/ml; ~50 ml on each plant) cultured for 10 days on PDA. As a control, three plants were inoculated with sterilized water. The plants were covered with plastic bags for 72 h to maintain high relative humidity (24 to 28°C). At 20 days after inoculation, small dark lesions enlarged into brown blight similar to that observed on naturally infected leaves. P. microspora was isolated from all inoculated plants, but not the controls. The fungus was confirmed by molecular analysis of the 5.8S subunit and flanking internal transcribed spaces (ITS1 and ITS2) of rDNA amplified from DNA extracted from single-spore cultures, and amplified with the ITS1/ITS4 primers and sequenced as previously described (4). Sequences were compared with other DNA sequences in GenBank using a BLASTN search. The P. microspora isolates were 99% homologous to other P. microspora (DQ456865, EU279435, FJ459951, and FJ459950). The morphological characteristics, pathogenicity, and molecular data assimilated in this study corresponded with the fungus P. microspora (2). This fungus has been previously reported as the causal agent of scab disease of Psidium guajava in Hawaii, the decline of Torreya taxifolia in Florida, and the leaf blight of Reineckea carnea in China (1,3). Therefore, this study presents the first report of P. microspora as a pathogen on T. cuspidata in Korea. The degree of pathogenicity of P. microspora to the Korean garden evergreen T. cuspidata requires quantification to determine its potential economic damage and to establish effective management practices. References: (1) D. F. Farr and A. Y. Rossman, Fungal Databases, Syst. Mycol. Microbiol. Lab. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ (2) L. M. Keith et al. Plant Dis. 90:16, 2006. (3) S. S. N. Maharachchikumbura. Fungal Diversity 50:167, 2011. (4) T. J. White et al. PCR Protocols. Academic Press, San Diego, CA, 1990.

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First Report of Alternaria Leaf Spot of Banana Caused by Alternaria alternata in the United States

Plant Disease ◽

10.1094/pdis-01-13-0007-pdn ◽

2013 ◽

Vol 97 (8) ◽

pp. 1116-1116 ◽

Cited By ~ 3

Author(s):

V. Parkunan ◽

S. Li ◽

E. G. Fonsah ◽

P. Ji

Keyword(s):

United States ◽

Alternaria Alternata ◽

Leaf Spot ◽

Morphological Characteristics ◽

The United States ◽

Its Sequencing ◽

Single Spore ◽

First Report ◽

Alternaria Leaf Spot ◽

Leaf Spots

Research efforts were initiated in 2003 to identify and introduce banana (Musa spp.) cultivars suitable for production in Georgia (1). Selected cultivars have been evaluated since 2009 in Tifton Banana Garden, Tifton, GA, comprising of cold hardy, short cycle, and ornamental types. In spring and summer of 2012, 7 out of 13 cultivars (African Red, Blue Torres Island, Cacambou, Chinese Cavendish, Novaria, Raja Puri, and Veinte Cohol) showed tiny, oval (0.5 to 1.0 mm long and 0.3 to 0.9 mm wide), light to dark brown spots on the adaxial surface of the leaves. Spots were more concentrated along the midrib than the rest of the leaf and occurred on all except the newly emerged leaves. Leaf spots did not expand much in size, but the numbers approximately doubled during the season. Disease incidences on the seven cultivars ranged from 10 to 63% (10% on Blue Torres Island and 63% on Novaria), with an average of 35% when a total of 52 plants were evaluated. Six cultivars including Belle, Ice Cream, Dwarf Namwah, Kandarian, Praying Hands, and Saba did not show any spots. Tissue from infected leaves of the seven cultivars were surface sterilized with 0.5% NaOCl, plated onto potato dextrose agar (PDA) media and incubated at 25°C in the dark for 5 days. The plates were then incubated at room temperature (23 ± 2°C) under a 12-hour photoperiod for 3 days. Grayish black colonies developed from all the samples, which were further identified as Alternaria spp. based on the dark, brown, obclavate to obpyriform catenulate conidia with longitudinal and transverse septa tapering to a prominent beak attached in chains on a simple and short conidiophore (2). Conidia were 23 to 73 μm long and 15 to 35 μm wide, with a beak length of 5 to 10 μm, and had 3 to 6 transverse and 0 to 5 longitudinal septa. Single spore cultures of four isolates from four different cultivars were obtained and genomic DNA was extracted and the internal transcribed spacer (ITS1-5.8S-ITS2) regions of rDNA (562 bp) were amplified and sequenced with primers ITS1 and ITS4. MegaBLAST analysis of the four sequences showed that they were 100% identical to two Alternaria alternata isolates (GQ916545 and GQ169766). ITS sequence of a representative isolate VCT1FT1 from cv. Veinte Cohol was submitted to GenBank (JX985742). Pathogenicity assay was conducted using 1-month-old banana plants (cv. Veinte Cohol) grown in pots under greenhouse conditions (25 to 27°C). Three plants were spray inoculated with the isolate VCT1FT1 (100 ml suspension per plant containing 105 spores per ml) and incubated under 100% humidity for 2 days and then kept in the greenhouse. Three plants sprayed with water were used as a control. Leaf spots identical to those observed in the field were developed in a week on the inoculated plants but not on the non-inoculated control. The fungus was reisolated from the inoculated plants and the identity was confirmed by morphological characteristics and ITS sequencing. To our knowledge, this is the first report of Alternaria leaf spot caused by A. alternata on banana in the United States. Occurrence of the disease on some banana cultivars in Georgia provides useful information to potential producers, and the cultivars that were observed to be resistant to the disease may be more suitable for production. References: (1) E. G. Fonsah et al. J. Food Distrib. Res. 37:2, 2006. (2) E. G. Simmons. Alternaria: An identification manual. CBS Fungal Biodiversity Center, Utrecht, Netherlands, 2007.

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