First report of fruit blight caused by Alternaria alternata on sesame in Northeast China

Sesame (Sesamum indicum L.) is an important oilseed crop in China and it is also used in food and health products. In August of 2019, a blight sesame fruit was observed in a field of Liaoyang city, Liaoning province of China. Initial disease symptoms consisted of brown or dark brown spots on fruit. With time, lesions coalesced and the whole fruit turned dark brown or black. Most of the diseased fruit had thin and small, deformed, necrotic, hardened cracked epidermal lesions. Lesions were also produced on stem and petioles leading to leaf abscission. The disease results in premature fruit death, and in turn, considerable yield losses. To determine the causal agent, symptomatic fruit with developing lesions were collected, and surface sterilized in 2% NaClO for 3 min, rinsed three times in distilled water, and plated onto PDA medium. After incubation at 25°C for 5 days, a dark olivaceous fungus with abundant, branched, brown to black, and septate hyphae was consistently isolated. Twenty single spores were separated with an inoculation needle under stereomicroscope. The conidia were in chains, brown, obclavate, ovoid or ellipsoid, with 1-6 transverse septa and 0-4 longitudinal or oblique septa 12.5 to 45 × 6.5 to 14.5 μm in size. Conidiophores were septate, light brown to olive brown, measuring 22-60 μm × 2-4 μm. The morphological characteristics of the 20 isolates all matched the description of Alternaria alternata (Simmons, 2007). The internal transcribed spacer (ITS) region of rDNA of 15 isolates was amplified using primers ITS1/ITS4 (White et al. 1990) and EF1-728F/EF1-986R (Carbone et al. 1999) and sequenced. Identical sequences were obtained and the sequence of the isolate ZMHG12 was submitted to GenBank (Accession no. MW418181 and MW700316). BLAST analysis of the sequences of the isolates of ZMHG12 showed 100% to A. alternata (KP739875 and LC132712). In pathogenicity tests, a conidial suspension (2.5 × 105 conidia per ml) was prepared from 7 days-old cultures of isolate ZMHG12 grown on PDA at 25°C. Fruit of 10 two-month-old potted sesame plants (Variety “Liaozhi 8”) were sprayed with the conidia suspension until runoff. Another 10 plants sprayed with distilled water to served as non-inoculated controls. All plants were maintained for 48 h in a humid chamber with a temperature of 25°C to 26°C, and then moved to a greenhouse. Ten days after inoculation, all fruit of inoculated plants exhibited symptoms similar to those observed in the field and non-inoculated control plants remained symptomless. The experiment was repeated twice with similar results. A. alternata has been reported as a pathogen caused leaf blight disease of sesame in Pakistan (Nayyar et al. 2017). To our knowledge, this is the first report of A.alternata causing fruit blight of sesame in China. To date, we have observed the disease on sesames in fields of Fuxin, Chaoyang and Tieling city in Liaoning Province, and Tongliao city in Inner Mongolia of China, and it has become an important disease in sesame production of China. References : Simmons E. G. 2007. Alternaria: An identification manual. CBS Fungal Biodiversity Center, Utrecht, Netherlands. White T. J., et al. 1990. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego. Carbone I., et al. 1999. Mycologia, 91: 553-556. Nayyar, B. G., et al. 2017. Plant Pathology Journal, 33 (6): 543-553.

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First Report of Nigrospora Leaf Blight on Tea Caused by Nigrospora sphaerica in India

Plant Disease ◽

10.1094/pdis-05-14-0545-pdn ◽

2015 ◽

Vol 99 (3) ◽

pp. 417-417 ◽

Cited By ~ 11

Author(s):

J. Dutta ◽

S. Gupta ◽

D. Thakur ◽

P. J. Handique

Keyword(s):

Camellia Sinensis ◽

West Bengal ◽

Morphological Characteristics ◽

Its Region ◽

Causative Organism ◽

Distilled Water ◽

Conidial Suspension ◽

Tea Leaves ◽

First Report ◽

Initial Symptoms

Tea [Camellia sinensis (L.) O. Kuntze] is an economically important non-alcoholic caffeine-containing beverage crop widely cultivated for leaves in India, especially in the Darjeeling district of West Bengal. In May 2012, distinct blight symptoms were observed on leaves of popular tea cultivars AV-2, Tukdah 78, Rungli Rungliot 17/144, and Bannockburn 157 in commercial tea estates of the Darjeeling district. This disease reduces yield and quality of the leaves. The initial symptoms were frequently observed on the young leaf margins and apices. Foliar symptoms are characterized by grayish to brown, semicircular or irregular shaped lesions, often surrounded by pale yellow zones up to 9 mm in diameter. The lesions later expand and the affected leaves turn grayish to dark brown and eventually the dried tissue falls, leading to complete defoliation of the plant. The disease causes damage to leaves of all ages and is severe in young leaves. A portion of the symptomatic leaf tissues were surface sterilized in 70% ethanol for 30 s, then in 2% NaClO for 3 min, rinsed three times in sterile distilled water, and plated onto potato dextrose agar (PDA). The fungal colonies were initially white and then became grayish to brown with sporulation. Conidia were spherical to sub spherical, single-celled, black, 19 to 21 μm in diameter, and were borne on a hyaline vesicle at the tip of each conidiophore. Morphological characteristics of the isolates were concurring to those of Nigrospora sphaerica (1). Moreover, the internal transcribed spacer (ITS) region of the ribosomal RNA was amplified by using primers ITS1 and ITS4 and sequenced (GenBank Accession No. KJ767520). The sequence was compared to the GenBank database through nucleotide BLAST search and the isolate showed 100% similarity to N. sphaerica (KC519729.1). On the basis of morphological characteristics and nucleotide homology, the isolate was identified as N. sphaerica. Koch's postulates were fulfilled in the laboratory on tea leaves inoculated with N. sphaerica conidial suspension (106 conidia ml−1) collected from a 7-day-old culture on PDA. Six inoculated 8-month-old seedlings of tea cultivars AV-2 and S.3/3 were incubated in a controlled environment chamber at 25°C and 80 to 85% humidity with a 12-h photoperiod. In addition, three plants of each cultivar were sprayed with sterile distilled water to serve as controls. Twelve to 14 days after inoculation, inoculated leaves developed blight symptoms similar to those observed on naturally infected tea leaves in the field. No symptoms were observed on the control leaves. The pathogen was re-isolated from lesions and its identity was confirmed by morphological characteristics. It was reported that N. sphaerica is frequently encountered as a secondary invader or as a saprophyte on many plant species and also as a causative organism of foliar disease on several hosts worldwide (2,3). To our knowledge, this is first report of N. sphaerica as a foliar pathogen of Camellia sinensis in Darjeeling, West Bengal, India, or worldwide. References: (1) M. B. Ellis. Dematiaceous Hyphomycetes. CMI, Kew, Surrey, UK, 1971. (2) D. F. Farr and A. Y. Rossman. Fungal Databases, Syst. Mycol. Microbiol. Lab., ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ July 01, 2013. (3) E. R. Wright et al. Plant Dis. 92:171, 2008.

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First report of panicle rot caused by Fusarium asiaticum on foxtail millet in China

Plant Disease ◽

10.1094/pdis-04-21-0856-pdn ◽

2021 ◽

Author(s):

Fanxin Kong ◽

Haijin Zhang ◽

Zhi Liu ◽

Guoqiu Chen ◽

Jing Xu

Keyword(s):

Foxtail Millet ◽

Morphological Characteristics ◽

Aerial Mycelium ◽

Its Region ◽

Liaoning Province ◽

Pathogenicity Test ◽

Conidial Suspension ◽

Dark Cycle ◽

First Report ◽

Fusarium Asiaticum

Foxtail millet [ Setaria italica (L.) P. Beauv.] is one of the most important nutritious food crops. It is used for wine and health products in China. In August of 2019, panicle rot symptoms with up to 85% of panicles infected were observed on foxtail millet (cultivar Chaogu 8) in a commercial field located in Chaoyang city of Liaoning Province, China. Typical disease symptoms included brown spots on spikelets at early stages and brown-colored withering and rot of whole panicles at late stages, with the symptoms being more severe at the tip of the panicles. Under high humidity conditions, pink or salmon-colored molds developed on panicles. Symptomatic spikelet pieces were surface-disinfested with 70% ethanol for 1 min followed by 2% NaOCl for 3 min, rinsed with sterilized water for three times, and placed on potato dextrose agar (PDA) medium at 25°C. After 5 days, colonies turned pink to dark red with fluffy aerial mycelium and pigmentation with the age. Ten pure cultures were obtained from single conidia of mycelium grown on carnation leaf agar (CLA) medium at 25°C under a 12-h light-dark cycle using an inoculation needle under stereomicroscope. Macroconidia were hyaline, falcate with foot cells, 3–5 septate and size: 28.5- 44.0 μm × 3.8 - 4.9 μm. Chlamydospores were globose to subglobose (5.4 to 13.8 μm). No microconidia were produced on CLA. Black, ostiolate subglobose perithecia were formed on CLA after one month of incubation at 20°C under a 12-h light-dark cycle. Morphological characteristics of the fungus were in agreement with the description of Fusarium asiaticum (O’Donnell et al. 2004; Leslie and Summerell 2006). To validate this identification, partial translation elongation factor 1 alpha (TEF1-a) gene, and rDNA internal transcribed spacer (ITS) region of five isolates were amplified and sequenced (O’Donnell et al. 2015; White et al.1990). Identical sequences were obtained, and the sequence of one representative isolate (JGF-3) was submitted to GenBank. BLASTn analysis of both TEF sequence (MW685833) and ITS sequence (MW423687), revealed 100% sequence identity with F. asiaticum KT380120 and MT322117, respectively. Pathogenicity test were conducted on cultivar Chaogu 8 of foxtail millet. Inoculum was prepared from the culture of JGF-3 incubated in 2% mung beans juice on a shaker (140 rpm) at 25°C for 48 h. Conidial suspension (5 × 105 conidia per ml) was prepared and sprayed onto the panicles of 20 plants at the initial flowering stage and 20 additional plants that were sprayed with distilled water served as the non-inoculated controls. Treated plants were covered with plastic bags for 48 h and maintained at a greenhouse with day and night temperatures of 26 and 24°C, respectively. Two weeks after inoculation, all inoculated panicles exhibited symptoms similar to the syptoms observed in the field. No symptoms were observed in the non-inoculated control plants. The experiment was repeated twice with similar results. F. asiaticum was reisolated from the inoculated plants and its morphological characteristics matched those of the original isolates; the fungus was not reisolated from the non-inoculated plants. To our knowledge, this is the first report of F. asiaticum causing panicle rot of foxtail millet in China. To date, the disease has been observed to be present in Fuxin and Tieling city of Liaoning Province. Panicle rot can become an important disease in foxtail millet in China. References: O’Donnell, K., et al. 2004. Fungal Genetics and Biology 41: 600. Leslie, J. F., and Summerell, B. A. 2006. The Fusarium laboratory manual. Blackwell Publishing, Ames, pp 176-179. O’ Donnell, K., et al. 2015. Phytoparasitica 43: 583. White, T. J., et al. 1990. Academic Press, San Diego, CA, pp 315-322.

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First report of root rot of Schisandra chinensis caused by Fusarium acuminatum in Northeast China

Plant Disease ◽

10.1094/pdis-05-21-1052-pdn ◽

2021 ◽

Author(s):

Baoyu Shen ◽

Wensong Sun ◽

Kun Liu ◽

Jing Tian Zhang

Keyword(s):

Root Rot ◽

Apical Cell ◽

Morphological Characteristics ◽

Liaoning Province ◽

Effective Control ◽

Distilled Water ◽

Conidial Suspension ◽

Schisandra Chinensis ◽

First Report ◽

Fusarium Acuminatum

Wuweizi [Schisandra chinensis（Turcz.）Baill.] is used for traditional medicine in northeastern China. In August of 2019, root rot of S. chinensis with an incidence of 30%-50% was observed in a commercial field located in Liaozhong city (41º29’57” N, 122º52’33” E) in the Liaoning province of China. The diseased plants were less vigorous, stunted, and had leaves that turned yellow to brown. Eventually, the whole plant wilted and died. The diseased roots were poorly developed with brown lesion and eventually they would rot. To determine the causal agent, symptomatic roots were collected, small pieces of root with typical lesions were surface sterilized in 2% NaOCl for 3 min, rinsed three times in distilled water, and then plated onto PDA medium. After incubation at 26°C for 5 days, whitish-pink or carmine to rose red colonies on PDA were transferred to carnation leaf agar (CLA). Single spores were isolated with an inoculation needle using a stereomicroscope. Five single conidia isolates obtained from the colonies were incubated at 26°C for 7 days, abundant macroconidia were formed in sporodochia. Macroconidia were falcate, slender, with a distinct curve to the latter half of the apical cell, mostly 3 to 5 septate, measuring 31.3 to 47.8 × 4.8 to 7.5µm (n=50). Microconidia were oval and irregular ovals, 0-1 septate, measuring 5.0 to 17.5 × 2.5 to 17.5µm (n=50). Chlamydospores formed in chains on within or on top of the mycelium. Morphological characteristics of the isolates were in agreement with Fusarium acuminatum (Leslie and Summerell, 2006). To confirm the identity, the partial sequence of the translation elongation factor 1 alpha (TEF1-á) gene of five isolates was amplified using the primers EF-1(ATGGGTAAGGARGACAAG) and EF-2 (GGARGTACCAGTSATCATGTT) (O’Donnell et al. 2015 ) and sequenced. The rDNA internal transcribed spacer (ITS) region for the five isolates was also amplified using the primers ITS1 (TCCGTAGGTGAACCTGCGG) and ITS4 (TCCTCCGCTATTGATATGC) (White et al.1990) and sequenced. The identical sequences were obtained, and one representative sequence of isolate WW31-5 was submitted to GenBank. BLASTn analysis of the TEF-á sequence (MW423624) and ITS sequence (MZ145386), revealed 100%（708/685bp, 563/563bp）sequence identity to F. acuminatum MH595498 and MW560481, respectively. Pathogenicity tests were conducted in greenhouse. Inoculums of F. acuminatum was prepared from the culture of WW31-5 incubated in 2% mung beans juice on a shaker (140 rpm) at 26°C for 5 days. Ten roots of 2-years old plants of S. chinensis were immersed in the conidial suspension (2 × 105 conidia/ml) for 6 hours, and another ten roots immersed in sterilized distilled water in plastic bucket for 6 hours. All these plants were planted into pots with sterilized field soil (two plants per pot). Five pots planted with inoculated plants and another five pots planted with uninoculated plants served as controls. All ten pots were maintained in a greenhouse at 22-26°C for 21 days and irrigated with sterilized water. The leaves of the inoculated plants became yellow，gradually dried up, eventually finally all the aboveground parts died. The roots of the inoculated plants were rotted. Non-inoculated control plants had no symptoms. F. acuminatum was reisolated from the roots of inoculated plants and had morphology identical to the original isolate. The experiment was repeated twice with similar results. F. acuminatum has been reported as a pathogen caused root rot of ginseng (Wang et al. 2016) and not reported on Wuweizi in China. To our knowledge, this is the first report of root rot of S. chinensis caused by F. acuminatum. We have also observed the disease at Benxi city of Liaoning Province in 2020 and it has become an important disease in production of S. chinensis and the effective control method should be adopted to reduce losses.

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Nigrospora sphaerica Causing Leaf Blight Disease on Sesame in Pakistan

Plant Disease ◽

10.1094/pdis-03-21-0460-pdn ◽

2021 ◽

Author(s):

Abdul Rehman ◽

Muhammad Waqar Alam ◽

Saira Mehboob ◽

Sumera Naz ◽

Rubina Mushtaq ◽

...

Keyword(s):

Management Practices ◽

Elongation Factor ◽

Its Region ◽

Molecular Data ◽

Leaf Blight ◽

Oilseed Crop ◽

Distilled Water ◽

Conidial Suspension ◽

Wide Range ◽

Blight Disease

Sesame (Sesamum indicum L.) commonly known as ‘til’ is the most ancient and widely grown oilseed crop of Pakistan. During 2020, field survey conducted in various research fields of Faisalabad (31°26′00.2″N, 73°04′25.4″E) revealed the occurrence of characteristic leaf blight disease with an incidence of 10 to 13%. The symptoms were characterized by yellow-brown and irregular lesions. At later stages, the lesions expanded and the affected leaves turned grayish to dark-brown and finally became wilted. Symptomatic leaves (both the diseased and healthy tissue) were cut into approximately 2 × 2 mm pieces, surface sterilized with 1% sodium hypochlorite for 30 s, 70% ethanol for 30 s, and finally, three times in sterile distilled water prior to culturing on Potato Dextrose Agar (PDA) and incubated at 25 °C under a 12-h photoperiod for 7 days. To obtain pure cultures, hyphal tips of growing mycelia from leaf tissues were carefully isolated and transferred onto fresh PDA plates. Fungal colonies of 11 isolates were initially white, becoming light to dark-gray. The conidia were black, spherical to subspherical, and single-celled (12 to 14 × 18 to 20 μm) in diameter, which were borne on a hyaline vesicle at the tip of the conidiophore. Further, to identify the pathogen to the species level, genomic DNA was extracted using a modified CTAB protocol described by (Guo et al. 2000). The internal transcribed spacer (ITS) region of the ribosomal DNA and translation elongation factor 1-alpha (TEF1-α) gene were amplified using ITS1/ITS4 (White et al. 1990) and EF1-728F/EF1-986R primer sets (Carbone and Kohn 1999), respectively. The sequences were submitted to GenBank (accession no. MW287214 for ITS and MW325222 for TEF1. The sequences comparison revealed 99% and 100% similarity to multiple sequences of N. sphaerica (GenBank accessions KX834822 and MN995332). On the basis of cultural features, conidial morphology and molecular data, the fungus was identified as Nigrospora sphaerica (Sacc.) Mason (Wang et al. 2017; Chen et al. 2018). To test the pathogenicity, fresh and healthy leaves of ten 6-week-old growth stage sesame plants were spray inoculated with a conidial suspension (105 conidia/ml), collected from a 7-day-old culture on PDA. In addition, 10 plants sprayed with sterile distilled water served as controls. Inoculated plants were covered with polyethylene bags to maintain high humidity and kept at 28°C, and observations were made at regular intervals. After 8-10 days of inoculation, leaves developed blight symptoms similar to those observed on naturally infected leaves, whereas control leaves remained asymptomatic. The pathogen was re-isolated from the inoculated leaves, and its identity was confirmed by morphological and molecular (ITS and TEF1) means, thus fulfilling Koch's postulates. N. sphaerica is distributed on a wide range of hosts and has been reported from different host genera including monocotyledonous and dicotyledonous (Wang et al. 2017). Previously, N. sphaerica has been reported to cause leaf blight of Cunninghamia lanceolata in China (Xu and Liu, 2016). To the best of our knowledge, this is the first report of Nigrospora sphaerica as the causal agent of leaf blight of sesame in Pakistan. Because sesame is an important oilseed crop of Pakistan, appropriate disease management practices should be developed and implemented.

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First Report of Postharvest Fruit Rot Disease of Hardy Kiwifruit Caused by Diaporthe eres in China

Plant Disease ◽

10.1094/pdis-08-20-1705-pdn ◽

2021 ◽

Author(s):

Jian Liu ◽

Xiaomei GUO ◽

Hui Zhang ◽

Yue Cao ◽

QUN SUN

Keyword(s):

Northeast China ◽

Morphological Characteristics ◽

Fruit Rot ◽

Liaoning Province ◽

Economic Losses ◽

Initial Symptom ◽

Distilled Water ◽

Conidial Suspension ◽

First Report ◽

Rot Disease

Hardy kiwifruit (Actinidia arguta), as an economically important fruit crop growing in Northeast China with thin, hairless and smooth skin, is susceptible to postharvest decay. In September 2018, infected cultivar Kwilv fruits were obtained from a commercial farm in Liaoning province, northeastern China. The occurring incidence of the rot disease varied from 20% to 90% according to the fruit number in each box during a 7-day-long storage at room temperature, and the initial symptom included a small, soft, chlorosis to light brown lesion and later watery brown lesions. Pure cultures of the same characteristics were obtained from the isolated strains in four rotten fruits on PDA medium. The isolates grew into transparent radial mycelium on PDA in the first two days followed by abundant white, fluffy aerial mycelium. After 14 days, colonies formed white to light brown aerial mycelial mats with gray concentric rings, and they produced gray and embedded pycnidia. Alpha conidia of 4.4 to 8.8 µm × 1.4 to 3.3 µm (n = 50) were abundant in culture, hyaline, aseptate, ellipsoidal to fusiform, while Beta conidia at 20.5 to 28.6 µm × 1.0 to 1.4 µm (n = 50) were hyaline, long, slender, curved to hamate. These morphological characteristics were similar to Diaporthe species (anamorph: Phomopsis spp.) (Udayanga et al. 2014). For identification, DNA was extracted from three single isolates respectively , and the internal transcribed spacer (ITS) region, β-tubulin (BT), and histone (HIS) H3 gene were amplified by using primers ITS1/ITS4 (White et al. 1990), T1/T22 (O'Donnell et al. 1997) and HIS1F/HISR (Gao et al. 2017), respectively. The three isolates produced identical sequences across all three gene regions, which were submitted to NCBI (Genbank accession numbers MT561361, MT561360 and MT855966). Nucleotide BLAST analysis revealed that the ITS sequence shared 99% homology with those of ex-type Diaporthe eres in NCBI GenBank (MG281047.1 and KJ210529.1), so did the BT sequence that had 98% identity to D. eres (MG281256.1 and KJ420799.1) and the HIS 99% identity to D. eres (MG28431.1 and MG281395.1) (Hosseini et al. 2020, Udayanga et al. 2014). Pathogenicity was tested by wound inoculation on the cv. Kwilv fruits. Five mature and healthy fruits were surface-sterilized with 1% NaClO solution, rinsed in sterile distilled water and dried. Every fruit was wounded by penetrate the peel 1-2 mm with a sterile needle, and inoculated with mycelium plugs (5 mm in diameter) of the isolate on PDA, with five inoculated with sterile PDA plugs as controls. Treated fruits were kept in sterilized transparent plastic cans separately under high humidity (RH 90 to 100%) at 28°C. After five days, the same rot symptoms were observed on all fruits inoculated with mycelium while the control remained symptomless. The fungi was re-isolated from the lesions of inoculated fruits and identified as D. eres by sequencing, thus fulfilling Koch's postulates. The pathogenicity experiment was re-performed using D. eres conidial suspension (107 conidia/ml) in sterile distilled water in October 2019 and the same results were obtained. D. eres was recently reported to cause European pear rot in Italy (Bertetti et al. 2018). To our knowledge, this is the first report of D. eres causing a postharvest rot in hardy kiwifruit in China, leading to severe disease and thus huge economic losses in Northeast China. Accordingly, effective measures should be taken to prevent its spreading to other production regions in China.

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First Report of Foliar and Stem Blight on Sunflower Caused by Alternaria helianthiinficiens in Croatia

Plant Disease ◽

10.1094/pdis-05-12-0512-pdn ◽

2012 ◽

Vol 96 (11) ◽

pp. 1698-1698 ◽

Cited By ~ 1

Author(s):

K. Vrandečić ◽

D. Jurković ◽

J. Ćosić ◽

I. Stanković ◽

A. Vučurović ◽

...

Keyword(s):

Disease Incidence ◽

Pathogenic Fungus ◽

Morphological Characteristics ◽

Its Region ◽

Nucleotide Identity ◽

Oilseed Crop ◽

Conidial Suspension ◽

First Report ◽

Stem Blight ◽

Detached Leaves

Sunflower (Helianthus annus L.) is the most important oilseed crop in Croatia. In August 2009, in six localities of eastern Croatia, severe foliar and stem blight symptoms were observed on several genotypes with disease incidence ranging from 10 to 50%. At the initial stage of the infection, irregular to oval, brown spots different in size, surrounded by a chlorotic halo, appeared on the leaves that gradually became enlarged and coalesced, and whole leaves turned yellow and necrotic, followed by defoliation. Lesions on the stems were light to dark brown, randomly distributed, rounded and tapered on the ends; later becoming large and elongated causing stem breakage. Tissue within the lesion was reddish on the cross section. To determine the causal agent, small pieces of symptomatic leaves and stem tissue of sunflower were surface disinfested and placed on potato dextrose agar. A total of 17 isolates from leaves as well as six from stems were obtained and all formed cottony, dark olivaceous to black colonies under 12 h of fluorescent light per day. All isolates formed uniform solitary, pale brown to brown, long ovoid conidia with five to eight transverse and one to two longitudinal septa. The conidia of all isolates were slightly constricted at the transverse septa, measuring 55 to 90 × 14 to 20 μm. Based on the morphological characteristics, the pathogen was identified as Alternaria helianthiinficiens E.G. Simmons, Walcz & R.G. Roberts (4). The pathogenicity was tested with one representative isolate (Alt5) by injection of a conidial suspension (106 conidia/ml) into stems of 20 healthy sunflower seedlings and by spraying 20 non-wounded detached leaves with a suspension of spores. Small necrotic spots on all inoculated seedlings and leaves formed 5 and 9 days after inoculation, respectively. The control sunflower seedlings and detached leaves, inoculated with sterile water, showed no reactions. The identity of isolate Alt5 was futher confirmed by amplification and sequencing of the internal transcribed spacer (ITS) region of rDNA. Because there are no available corresponding ITS sequences of A. helianthiinficiens in the GenBank, reference type strain CBS 208.86 (publicly purchased, CBS, Utrecht, Netherlands) was also sequenced in this study. Total DNA was extracted directly from fungal mycelium and PCR amplification and sequencing were performed with primers ITS1F/ITS4. Sequence analysis of ITS region revealed 100% nucleotide identity between isolate Alt5 (GenBank Accession No. JX101648) and isolate CBS 208.86 (GenBank Accession No. JX101649). The nucleotide identity of both isolates compared with A. helianthi (HM449991), another sunflower pathogenic fungus, was only 80%. A. helianthiinficiens has previously been reported on sunflower in Hungary and the USA (3), Serbia (1), and Korea (2). However, to our knowledge, this is the first report of A. helianthiinficiens occurrence in Croatia as a new and harmful parasite of sunflower, illustrating an expansion of its geographical range and underscoring the need for phytosanitary control because it is a seedborne fungus. References: (3) M. Aćimović and N. Lačok. Helia 14:129, 1991. (4) H. S. Cho and S. H. Yu. Plant Pathol. J. 16:331, 2000. (2) E. G. Simmons. Mycotaxon 25:203, 1986. (1) E. G. Simmons. Alternaria: An Identification Manual. CBS Fungal Biodiversity Centre, Utrecht, the Netherlands, 2007.

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First report of Coniella castaneicola causing leaf blight on blueberry (Vaccinium virgatum) in China

Plant Disease ◽

10.1094/pdis-05-21-1122-pdn ◽

2021 ◽

Author(s):

Jiahao Lai ◽

Guihong Xiong ◽

Bing Liu ◽

Weigang Kuang ◽

Shuilin Song

Keyword(s):

Molecular Identification ◽

Morphological Characteristics ◽

Leaf Blight ◽

Yield Potential ◽

Effective Control ◽

Economic Losses ◽

Distilled Water ◽

First Report ◽

Fungal Isolates ◽

Blight Disease

Blueberry (Vaccinium virgatum), an economically important small fruit crop, is characterized by its highly nutritive compounds and high content and wide diversity of bioactive compounds (Miller et al. 2019). In September 2020, an unknown leaf blight disease was observed on Rabbiteye blueberry at the Agricultural Science and Technology Park of Jiangxi Agricultural University in Nanchang, China (28°45'51"N, 115°50'52"E). Disease surveys were conducted at that time, the results showed that disease incidence was 90% from a sampled population of 100 plants in the field, and this disease had not been found at other cultivation fields in Nanchang. Leaf blight disease on blueberry caused the leaves to shrivel and curl, or even fall off, which hindered floral bud development and subsequent yield potential. Symptoms of the disease initially appeared as irregular brown spots (1 to 7 mm in diameter) on the leaves, subsequently coalescing to form large irregular taupe lesions (4 to 15 mm in diameter) which became curly. As the disease progressed, irregular grey-brown and blighted lesion ran throughout the leaf lamina from leaf tip to entire leaf sheath and finally caused dieback and even shoot blight. To identify the causal agent, 15 small pieces (5 mm2) of symptomatic leaves were excised from the junction of diseased and healthy tissue, surface-sterilized in 75% ethanol solution for 30 sec and 0.1% mercuric chloride solution for 2 min, rinsed three times with sterile distilled water, and then incubated on potato dextrose agar (PDA) at 28°C for 5-7 days in darkness. Five fungal isolates showing similar morphological characteristics were obtained as pure cultures by single-spore isolation. All fungal colonies on PDA were white with sparse creeping hyphae. Pycnidia were spherical, light brown, and produced numerous conidia. Conidia were 10.60 to 20.12 × 1.98 to 3.11 µm (average 15.27 × 2.52 µm, n = 100), fusiform, sickle-shaped, light brown, without septa. Based on morphological characteristics, the fungal isolates were suspected to be Coniella castaneicola (Cui 2015). To further confirm the identity of this putative pathogen, two representative isolates LGZ2 and LGZ3 were selected for molecular identification. The internal transcribed spacer region (ITS) and large subunit (LSU) were amplified and sequenced using primers ITS1/ITS4 (Peever et al. 2004) and LROR/LR7 (Castlebury and Rossman 2002). The sequences of ITS region (GenBank accession nos. MW672530 and MW856809) showed 100% identity with accessions numbers KF564280 (576/576 bp), MW208111 (544/544 bp), MW208112 (544/544 bp) of C. castaneicola. LSU gene sequences (GenBank accession nos. MW856810 to 11) was 99.85% (1324/1326 bp, 1329/1331 bp) identical to the sequences of C. castaneicola (KY473971, KR232683 to 84). Pathogenicity was tested on three blueberry varieties (‘Rabbiteye’, ‘Double Peak’ and ‘Pink Lemonade’), and four healthy young leaves of a potted blueberry of each variety with and without injury were inoculated with 20 μl suspension of prepared spores (106 conidia/mL) derived from 7-day-old cultures of LGZ2, respectively. In addition, four leaves of each variety with and without injury were sprayed with sterile distilled water as a control, respectively. The experiment was repeated three times, and all plants were incubated in a growth chamber (a 12h light and 12h dark period, 25°C, RH greater than 80%). After 4 days, all the inoculated leaves started showing disease symptoms (large irregular grey-brown lesions) as those observed in the field and there was no difference in severity recorded between the blueberry varieties, whereas the control leaves showed no symptoms. The fungus was reisolated from the inoculated leaves and confirmed as C. castaneicola by morphological and molecular identification, fulfilling Koch’s postulates. To our knowledge, this is the first report of C. castaneicola causing leaf blight on blueberries in China. The discovery of this new disease and the identification of the pathogen will provide useful information for developing effective control strategies, reducing economic losses in blueberry production, and promoting the development of the blueberry industry.

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First Report of Leaf Spot of Sweet Basil Caused by Cercospora guatemalensis in Korea

Plant Disease ◽

10.1094/pdis-05-12-0436-pdn ◽

2012 ◽

Vol 96 (10) ◽

pp. 1580-1580

Author(s):

J. H. Park ◽

K. S. Han ◽

J. Y. Kim ◽

H. D. Shin

Keyword(s):

Leaf Spot ◽

Morphological Characteristics ◽

Its Region ◽

Culture Collection ◽

Distilled Water ◽

First Report ◽

Sweet Basil ◽

Organic Farm ◽

Leaf Spots ◽

Close Phylogenetic Relationship

Sweet basil, Ocimum basilicum L., is a fragrant herb belonging to the family Lamiaceae. Originated in India 5,000 years ago, sweet basil plays a significant role in diverse cuisines across the world, especially in Asian and Italian cooking. In October 2008, hundreds of plants showing symptoms of leaf spot with nearly 100% incidence were found in polyethylene tunnels at an organic farm in Icheon, Korea. Leaf spots were circular to subcircular, water-soaked, dark brown with grayish center, and reached 10 mm or more in diameter. Diseased leaves defoliated prematurely. The damage purportedly due to this disease has reappeared every year with confirmation of the causal agent made again in 2011. A cercosporoid fungus was consistently associated with disease symptoms. Stromata were brown, consisting of brown cells, and 10 to 40 μm in width. Conidiophores were fasciculate (n = 2 to 10), olivaceous brown, paler upwards, straight to mildly curved, not geniculate in shorter ones or one to two times geniculate in longer ones, 40 to 200 μm long, occasionally reaching up to 350 μm long, 3.5 to 6 μm wide, and two- to six-septate. Conidia were hyaline, acicular to cylindric, straight in shorter ones, flexuous to curved in longer ones, truncate to obconically truncate at the base, three- to 16-septate, and 50 to 300 × 3.5 to 4.5 μm. Morphological characteristics of the fungus were consistent with the previous reports of Cercospora guatemalensis A.S. Mull. & Chupp (1,3). Voucher specimens were housed at Korea University herbarium (KUS). An isolate from KUS-F23757 was deposited in the Korean Agricultural Culture Collection (Accession No. KACC43980). Fungal DNA was extracted with DNeasy Plant Mini DNA Extraction Kits (Qiagen Inc., Valencia, CA). The complete internal transcribed spacer (ITS) region of rDNA was amplified with the primers ITS1/ITS4 and sequenced. The resulting sequence of 548 bp was deposited in GenBank (Accession No. JQ995781). This showed >99% similarity with sequences of many Cercospora species, indicating their close phylogenetic relationship. Isolate of KACC43980 was used in the pathogenicity tests. Hyphal suspensions were prepared by grinding 3-week-old colonies grown on PDA with distilled water using a mortar and pestle. Five plants were inoculated with hyphal suspensions and five plants were sprayed with sterile distilled water. The plants were covered with plastic bags to maintain a relative humidity of 100% for 24 h and then transferred to a 25 ± 2°C greenhouse with a 12-h photoperiod. Typical symptoms of necrotic spots appeared on the inoculated leaves 6 days after inoculation, and were identical to the ones observed in the field. C. guatemalensis was reisolated from symptomatic leaf tissues, confirming Koch's postulates. No symptoms were observed on control plants. Previously, the disease was reported in Malawi, India, China, and Japan (2,3), but not in Korea. To our knowledge, this is the first report of C. guatemalensis on sweet basil in Korea. Since farming of sweet basil has recently started on a commercial scale in Korea, the disease poses a serious threat to safe production of this herb, especially in organic farming. References: (1) C. Chupp. A Monograph of the Fungus Genus Cercospora. Ithaca, NY, 1953. (2) D. F. Farr and A. Y. Rossman. Fungal Databases. Systematic Mycology & Microbiology Laboratory, ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ , May 5, 2012. (3) J. Nishikawa et al. J. Gen. Plant Pathol. 68:46, 2002.

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First Report of Leaf Blight Caused by Septoria allii on Garlic Chives in Korea

Plant Disease ◽

10.1094/pdis-08-12-0809-pdn ◽

2013 ◽

Vol 97 (1) ◽

pp. 147-147

Author(s):

J. H. Park ◽

S. E. Cho ◽

K. S. Han ◽

H. D. Shin

Keyword(s):

Disease Incidence ◽

Morphological Characteristics ◽

Its Region ◽

Leaf Blight ◽

Plant Diseases ◽

Cultivated Plants ◽

Sequence Information ◽

Conidial Suspension ◽

Korean Society ◽

First Report

Garlic chives, Allium tuberosum Roth., are widely cultivated in Asia and are the fourth most important Allium crop in Korea. In June 2011, a leaf blight of garlic chives associated with a Septoria spp. was observed on an organic farm in Hongcheon County, Korea. Similar symptoms were also found in fields within Samcheok City and Yangku County of Korea during the 2011 and 2012 seasons. Disease incidence (percentage of plants affected) was 5 to 10% in organic farms surveyed. Diseased voucher specimens (n = 5) were deposited at the Korea University Herbarium (KUS). The disease first appeared as yellowish specks on leaves, expanding to cause a leaf tip dieback. Half of the leaves may be diseased within a week, especially during wet weather. Pycnidia were directly observed in leaf lesions. Pycnidia were amphigenous, but mostly epigenous, scattered, dark brown to rusty brown, globose, embedded in host tissue or partly erumpent, separate, unilocular, 50 to 150 μm in diameter, with ostioles of 20 to 40 μm in diameter. Conidia were acicular, straight to sub-straight, truncate at the base, obtuse at the apex, hyaline, aguttulate, 22 to 44 × 1.8 to 3 μm, mostly 3-septate, occasionally 1- or 2-septate. These morphological characteristics matched those of Septoria allii Moesz, which is differentiated from S. alliacea on conidial dimensions (50 to 60 μm long) (1,2). A monoconidial isolate was cultured on potato dextrose agar (PDA). Two isolates have been deposited in the Korean Agricultural Culture Collection (Accession Nos. KACC46119 and 46688). Genomic DNA was extracted using the DNeasy Plant Mini DNA Extraction Kit (Qiagen Inc., Valencia, CA). The internal transcribed spacer (ITS) region of rDNA was amplified using the ITS1/ITS4 primers and sequenced. The resulting sequence of 482-bp was deposited in GenBank (JX531648 and JX531649). ITS sequence information was at least 99% similar to those of many Septoria species, however no information was available for S. allii. Pathogenicity was tested by spraying leaves of three potted young plants with a conidial suspension (2 × 105 conidia/ml), which was harvested from a 4-week-old culture on PDA. Control leaves were sprayed with sterile water. The plants were placed in humid chambers (relative humidity 100%) for the first 48 h. After 7 days, typical leaf blight symptoms started to develop on the leaves of inoculated plants. S. allii was reisolated from the lesions of inoculated plants, confirming Koch's postulates. No symptoms were observed on control plants. The host-parasite association of A. tuberosum and S. allii has been known only from China (1). S. alliacea has been recorded on several species of Allium, e.g. A. cepa, A. chinense, A. fistulosum, and A. tuberosum from Japan (4) and A. cepa from Korea (3). To the best of our knowledge, this is the first report of S. allii on garlic chives. No diseased plants were observed in commercial fields of garlic chives which involved regular application of fungicides. The disease therefore seems to be limited to organic garlic chive production. References: (1) P. K. Chi et al. Fungous Diseases on Cultivated Plants of Jilin Province, Science Press, Beijing, China, 1966. (2) P. A. Saccardo. Sylloge Fungorum Omnium Hucusque Congnitorum. XXV. Berlin, 1931. (3) The Korean Society of Plant Pathology. List of Plant Diseases in Korea, Suwon, Korea, 2009. (4) The Phytopathological Society of Japan. Common Names of Plant Diseases in Japan, Tokyo, Japan, 2000.

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First Report of Curvularia Leaf Blight on Curcuma wenyujin Caused by Curvularia clavata in China

Plant Disease ◽

10.1094/pdis-04-12-0392-pdn ◽

2013 ◽

Vol 97 (1) ◽

pp. 138-138 ◽

Cited By ~ 4

Author(s):

X. Y. Chen ◽

J. D. Feng ◽

Z. Su ◽

C. Sui ◽

X. Huang

Keyword(s):

Morphological Characteristics ◽

Its Region ◽

Leaf Blight ◽

Hainan Province ◽

Continuous Cropping ◽

Single Spore ◽

Chinese Medicinal Herb ◽

First Report ◽

Causal Pathogen ◽

Blight Disease

Curcuma wenyujin Y.H. Chen & C. Ling is a traditional Chinese medicinal herb in the Zingiberaceae family. Commonly known as Wen yujin, the root is widely used for alleviating pain and protecting the liver. A severe leaf blight disease was observed in three C. wenyujin farms in Hainan Province of China in October 2010. The obvious symptoms of leaf blight, yellow to brown irregular lesions (1 to 20 cm) on C. wenyujin, usually began at the tips of leaves and the main veins. This disease, especially severe from August to October, caused heavy damage and 100% of mature plants (10 months old) in farms were infected. The disease was most severe when continuous cropping was performed and showed slight improvement when rotation was adopted. Farmers usually sprayed carbendazim (50% WP) and thiophanate-methyl (70% WP) to control this disease, but these treatments were not effective. To isolate the causal pathogen, diseased plants were collected in October 2010 from a field of the Hainan Branch Institute of Medicinal Plant Development in Hainan Province. Lesion tissue was removed from the border between symptomatic and healthy tissue, surface sterilized in 75% ethanol for 1 min, washed in three changes of sterile distilled water, transferred to potato dextrose agar (PDA) plates, and incubated at 28°C for 7 days. Single spore cultures of five isolates were obtained and identified as Curvularia clavata based on morphological characteristics (1). Conidia measured 20 to 29 × 7.5 to 10.5 μm (n = 100), were curved, 3-septate, and the third cell from the base was larger and darker than the others. Mycelia of single spore cultures growing on PDA for 5 days were used for DNA extraction using a plant genomic DNA kit (TIANGEN, Beijing). The internal transcribed spacer (ITS) region of the rDNA was amplified using primers ITS1 and ITS4. The amplicons were 562 bp in length (GenBank Accession No. JQ730852) and had 99% nucleotide identity with the GenBank Accession No. JN021115 and AF071336 of C. clavata. Pathogenicity tests were conducted using fresh and healthy detached Curcuma wenyujin leaves. Mycelial discs (10 mm) removed from a 5-day-old colony on PDA were used for inoculation. Each isolate was inoculated on three distinct leaves (two distinct inoculations per leaf). Three additional leaves inoculated with sterile PDA discs were used as control. Inoculated leaves were covered with a polythene film to maintain high humidity. Leaves in trays were kept in a growth chamber at 28°C and observed for symptom appearance every day. Five days after inoculation, inoculated leaves developed blight symptoms similar to those observed on naturally infected leaves. No symptoms were observed on non-inoculated leaves. C. clavata was reisolated from the inoculated leaves, thus fulfilling Koch's postulates. C. clavata has been previously reported to be economically important on a number of other hosts (2). To our knowledge, this is the first report of Curvularia leaf blight on Curcuma wenyujin caused by C. clavata in China. References: (1) A. M Mandokhot et al. Eur. J. Plant Pathol.78:65, 1972. (2) T. Y. Zhang et al. Flora fungorum sinicorum: Beijing, China, 2010.

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