Alternaria spp. associated with leaf blight of maize in Heilongjiang Province, China

Plant Disease ◽  
2021 ◽  
Author(s):  
Xi Xu ◽  
Li Zhang ◽  
Xilang Yang ◽  
Hanshui Cao ◽  
Jingjing Li ◽  
...  
Keyword(s):  
Rna Polymerase Ii ◽  
Disease Incidence ◽  
Morphological Characteristics ◽  
Population Expansion ◽  
Leaf Blight ◽  
Economic Losses ◽  
Heilongjiang Province ◽  
Maize Leaves ◽  
Alternaria Species ◽  
Alternaria Sp

Maize is a major economic crop worldwide. Maize can be infected by Alternaria species causing leaf blight that can result in significant economic losses. In this study, 168 Alternaria isolates recovered from symptomatic maize leaves were identified based on morphological characteristics, pathogenicity, and multi-locus sequence analyses of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), the internal transcribed spacer of ribosomal DNA (rDNA ITS), the RNA polymerase II second largest subunit (RPB2), and histone 3 (HIS3). Maize isolates grouped to four Alternaria species including Alternaria tenuissima, A. alternata, A. burnsii, and Alternaria sp. Notably, A. tenuissima (71.4%) was the most prevalent of the four isolated species, followed by A. alternata (21.5%), Alternaria sp. (4.1%), and A. burnsii (3.0%). Pathogenicity tests showed that all four Alternaria species could produce elliptic to nearly round, or strip lesions on leaves of maize, gray white to dry white in the lesions center and reddish brown in the edge. The average disease incidence (58.47%) and average disease index (63.55) of maize leaves inoculated with A. alternata were significantly higher than levels resulting from A. tenuissima (55.28% and 58.49), Alternaria sp. (55.34% and 58.75), and A. burnsii (56% and 55). Haplotype analyses indicated that there were 14 haplotypes of A. tenuissima and 5 haplotypes of A. alternata in Heilongjiang province and suggested the occurrence of a population expansion. Results of the study showed that Alternaria species associated with maize leaf blight in Heilongjiang province are more diverse than those have been previously reported. This is the first report globally of A. tenuissima, A. burnsii, and an unclassified Alternaria species as causal agents of leaf blight on maize.

Morphological and Molecular Characterization of Alternaria Species Causing Leaf Blight on Watermelon in China

Plant Disease ◽  
2021 ◽  
Vol 105 (1) ◽  
pp. 60-70 ◽  
Author(s):  
Guoping Ma ◽  
Shuwen Bao ◽  
Juan Zhao ◽  
Yuan Sui ◽  
Xuehong Wu
Keyword(s):  
Rna Polymerase Ii ◽  
Disease Incidence ◽  
Disease Index ◽  
Leaf Blight ◽  
Economic Losses ◽  
Rdna Its ◽  
Detached Leaves ◽  
Alternaria Species ◽  
Alternaria Sp ◽  
The One

Watermelon is an economically important crop in China and is commonly affected by Alternaria-like leaf blight that can result in significant economic losses. In this study, 830 Alternaria isolates, recovered from symptomatic watermelon leaves, were identified based on morphological traits, pathogenicity, and multilocus sequence analyses of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), histone 3 (HIS3), the internal transcribed spacer of ribosomal DNA (rDNA ITS), and the RNA polymerase II second largest subunit (RPB2). Watermelon isolates grouped to five Alternaria species and one unclassified Alternaria species. They were A. tenuissima, A. alternata, A. cucumerina, A. infectoria, A. gaisen, and Alternaria sp. Notably, A. tenuissima was the most prevalent (73.5%) of the six isolated species, followed by A. alternata (25.0%), A. cucumerina (1.1%), Alternaria sp. (0.2%), A. infectoria (0.1%), and A. gaisen (0.1%). Pathogenicity tests demonstrated that all six Alternaria species could produce brown necrotic lesions on detached leaves of watermelon. The average disease incidence (75.1%) and average disease index (60.8) of watermelon resulting from inoculation of leaves with A. cucumerina were significantly higher than levels resulting from A. alternata (52.9% and 37.2) and A. tenuissima (47.5% and 30.8). Inoculation with Alternaria sp. resulted in a disease incidence (70.0%) and disease index (51.5), which were lower than those of A. cucumerina. The disease incidence and disease index in watermelon leaves inoculated with the one isolate of A. infectoria and the one isolate of A. gaisen present in the inoculated leaves were 28.9% and 16.4, and 48.9% and 31.4, respectively. Results of the study indicate that Alternaria species associated with watermelon leaf blight in China are more diverse than that has been previously reported. This is the first report globally of A. infectoria, A. gaisen, and an unclassified Alternaria species as causal agents of leaf blight on watermelon.

scholarly journals Alternaria spp. implicated in a disease complex of onion leaf blight in the tropics.

1969 ◽  
Vol 95 (1-2) ◽  
pp. 57-78
Author(s):  
Jessie Fernández ◽  
Lydia I. Rivera-Vargas ◽  
Irma Cabrera-Asencio ◽  
Sharon A. Cantrell
Keyword(s):  
Culture Media ◽  
Disease Incidence ◽  
Leaf Blight ◽  
Western Hemisphere ◽  
Molecular Characteristics ◽  
Growing Seasons ◽  
Rdna Its ◽  
Alternaria Species ◽  
Alternaria Sp ◽  
Plant Life Cycle

Alternaria isolates were collected from onion foliage at different stages of the plant life cycle. Incidence of Alternaria species in cultivars 'Mercedes' and 'Excallbur' was determined during two consecutive growing seasons in fields located In southern Puerto Rico. Leaves showing purple to brown sunken elliptical lesions with chlorotic halos were taken at random. Five leaf sections (0.5 cm) from each sample were superficially disinfested, transferred to culture media and incubated, and isolations were documented. Disease incidence ranged from 25 to 52% in 60- to 100-day-old plants. An increase in Alternaria incidence was observed in response to high relative humidity in the fields. A total of 280 isolates were obtained, and 35 were selected for morphological, pathogenic and molecular characterization. A complex of five different Alternaria species is associated with onion leaf blight on the island. Alternaria destruens, A. tenuissima, A. palandui, A. allii and a group of small-spore Alternaria sp., belonging to a taxonomically undescribed group, were identified. Sixty-two percent of selected isolates belong to this group having an A. arborescens intermediate sporulation pattern. Alternaria destruens and A. palandui have not been previously reported as associated with onions in the Caribbean or in the Western Hemisphere. Pathogenicity tests showed that A. allii, A. tenuissima and Alternaria sp. were pathogenic to onion foliage, with A. allii as the most virulent. Molecular characteristics of the isolates were determined by using the ITS of the rDNA gene. Phylogenetic relationships based on rDNA ITS sequences from Alternaria isolates and other Pleosporaceae distinguished three clades. The first clade of large filiform-beaked spores included A. allii from this study, as well as isolates from the GenBank (A. porri, A. solani, A. macrospora, A. zinniae and A. sesamicola). These formed a monophyletic group, discrete from other members of the genus. The second clade included a diverse group of smallspore Alternaria: A. tenuissima, A. alternata, A. palandui, A. destruens and Alternaria sp.; the third clade included Stemphylium spp.

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

Plant Disease ◽  
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.

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

Plant Disease ◽  
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.

scholarly journals First Report of Fusarium thapsinum Causing Maize Stalk Rot in China

Plant Disease ◽  
2021 ◽  
Author(s):  
Jie Zhang ◽  
Yanyong Cao ◽  
Shengbo Han ◽  
Laikun Xia ◽  
Zhendong Zhu ◽  
...  
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Disease Incidence ◽  
Apical Cell ◽  
Morphological Characteristics ◽  
Post Inoculation ◽  
Average Growth ◽  
First Report ◽  
Stalk Rot ◽  
Fusarium Thapsinum

Maize (Zea mays L.) is the most widely grown crop in China, which was planted 41.28 million hectares in 2019 (http://data.stats.gov.cnw/easyquery.htm?cn=C01&zb=A0D0F&sj=2019). Several fungal diseases of maize are reported in which stalk rot has become one of the most destructive diseases in China. The average yield losses affected by the disease are estimated at 10% to 20% (Yu et al. 2016). From 2017 to 2019, a survey was conducted to determine the population diversity of Fusarium species associated with maize diseases in 18 cities across Henan province. Fusarium stalk rot of maize with disease incidence more than 25% was observed in two continuous maize fields at Xuchang city. The diseased stem tissues from junctions in health and disease were chopped into small pieces (3 × 8 mm), superficially disinfected (70% ethyl alcohol for 1 min), placed onto potato dextrose agar (PDA) amended with L-(+)-Lactic-acid (1 g/L), poured in petri plates and incubated at 25°C for 4 days. Mycelia showing morphological characteristic of Fusarium spp. were sub-cultured from single conidium. The pure fungal isolates produced fluffy colonies, white aerial mycelium with yellow pigment in agar. The radial mycelial growth was measured and calculated at an average growth rate 10.9 mm/day at 25°C (Fig. 1A; 1B). Macroconidia produced on carnation leaf agar (CLA) were relatively slender, slightly curved and thick-walled, mostly 3 to 5 marked septa, with a curved and tapering apical cell and poorly developed foot cell, 46.9 ± 5.6 µm × 4.9 ± 0.2 µm (Fig. 1C). Microconidia formed abundantly and were generally oval on CLA, 8.2 ± 0.5 µm × 3.4± 0.1 µm (Fig. 1D). No chlamydospores were observed. Morphological characteristics of the isolates matched the description of Fusarium thapsinum (Leslie and Summerell 2006). To further get the phylogenetic evidence, TEF1-α (translation elongation factor), RPB1 (the largest subunit of RNA polymerase II) and RPB2 (the second largest subunit of RNA polymerase II) were amplified with primer pairs EF1/EF2 (O'Donnell et al. 1998), thapR1F (5′-TTTTCCTCACAAAGGAGCAAATCATG-3′)/thapR1R (5’-GTTCACCCAAGATATGGTCGAAAGCC-3’), and thapR2F (5′-ACTCTTTCACATTTGCGCCGAAC-3′)/thapR2R (5′-CGGAGCTTTCGTCCAGTGTGAC-3′), and sequenced, respectively. The BLAST search of the sequences of EF1-α, RPB1 and RPB2 shared 99.87% to 100% identity with those of F. thapsinum strains deposited in the GenBank (Supplementary Table 1). Sequences from two isolates (XCCG-3-B-1 and XCCG-3-A-1) were deposited in GenBank (Accession No. MT550014, MT997082 for EF-1α; MT550011, MT997087 for RPB1 and MT550008, MT997091 for RPB2). The phylogenetic relationships based on analysis of the partial sequences showed the representive isolates clustered together with F. thapsinum at 96% bootstrap values (Fig. 2). Combined with the results of morphological characteristics and phylogenetic analysis, the strain designated as Fusarium thapsinum. To complete Koch’s postulates, the pathogenicity of the isolates was tested using the silking-stage plants in a greenhouse based on previously described method with modification (Zhang et al. 2016). An 8 mm in diameter wound hole was created at the second or third internode of the plant above the soil surface and injected with 0.5 ml of mycelia plug. The inoculated stalk exhibited internal dark brown necrotic regions and the brown area elongated obviously around the insertion at 14 dpi (days post inoculation). At 30 dpi, the stalks turned soft, hollow and even lodging of the plants for those severe ones, which are similar to those observed on naturally infected maize plants in the field (Fig. 1F). When the roots of the three-leaf-stage seedlings were inoculated with 1×106 macroconidia solution (Ye et al. 2013), the root rot and leaf wilting symptoms were observed (Fig. 1E). While the control plants that were inoculated with only sterile water showed no disease symptoms. The pathogen was re-isolated from the inoculated tissues and the identity was confirmed by the morphological characters. Fusarium thapsinum had been described as causal agent of maize stalk rot in Pakistan (Tahir et al. 2018). To our knowledge, this is the first report of F. thapsinum associated with maize stalk rot in China. The discovery will strengthen the theoretical foundation of maize stalk rot disease management.

scholarly journals First Report of Fusarium proliferatum Causing Fruit Rot on Muskmelon (Cucumis melo L.) in China

Plant Disease ◽  
2021 ◽  
Author(s):  
Xiaoyan Yu ◽  
Jing Zhang ◽  
Lifeng Guo ◽  
Aoran Yu ◽  
Xiangjing Wang ◽  
...  
Keyword(s):  
Rna Polymerase Ii ◽  
Phylogenetic Trees ◽  
Salvia Miltiorrhiza ◽  
Disease Incidence ◽  
Morphological Characteristics ◽  
Fusarium Proliferatum ◽  
Fruit Rot ◽  
Single Spore ◽  
Effective Prevention ◽  
First Report

Muskmelon is an economically important crop in the world, especially in China, the largest producer of muskmelon with an annual output up to 12.7 million tonnes (Gómez-García et al. 2020). Since 2018, fruit rot was observed on muskmelon in Malianzhuang Base, the main muskmelon producing area in Shandong Province, whose disease incidence was about 25-30%. Water-soaked dark brown spots were initially appeared on the side of the fruit near the ground, then gradually expanded and covered with white mold with time. To isolate the pathogens, ten muskmelon fruits with typical symptoms were collected from different greenhouses in the base. Small tissues taken from the edge of the diseased and healthy tissues were immersed in 1% NaClO for 2 min, then soaked in 75% ethanol for 30 s, and rinsed 3 times with sterile distilled water (SDW). The sterilized tissues were naturally dried and placed on potato dextrose agar (PDA) amended with streptomycin sulfate (50 mg/L) for 7 days at 28℃. The emerging fungal mycelia were transferred to fresh PDA using the hyphal tip technology. Ten colonies were purified by single spore method and cultured on PDA for 7 days at 28℃ in the dark for morphological and molecular analyses. All colonies were flocculent with abundant white to light purple aerial hyphae, and the undersides of the colonies were observed to be from white to purple over time. Microconidia produced on PDA were hyaline, fusiform, ovoid, single cell without septum, and 4.5 to 12.7 × 2.0 to 3.6 μm in size (n=50). Macroconidia produced on carboxymethylcellulose agar (CMC) were slightly curved at both ends with three to five septa, and 17.6 to 35.7 × 2.8 to 4.0 μm in size (n=30). According to the morphological characteristics, these isolates were preliminarily identified as Fusarium sp. (Leslie and Summerell 2006). To further identify these isolates, genomic DNA of five isolates was extracted by CTAB method (Wu et al. 2001). The internal transcribed spacer (ITS) region of ribosomal DNA, translation elongation factor 1-α (TEF1) region, and the RNA polymerase II second largest subunit (RPB2) were amplified by PCR amplification with primers ITS1/ITS4, EF-1/EF-2, and RPB2-5F2/fRPB2-7cR, respectively (White et al. 1990; O’Donnell et al. 2008; Liu et al. 1999). Sequences of the five isolates were identical. The ITS, EF1-α, and RPB2 gene sequences of isolate NEAU-Mf-10-2 were submitted to NCBI GenBank with accession numbers of MZ950914, MZ960928, and MZ960929, respectively, having 100% similarity to those of Fusarium proliferatum (MK372368, MK952799 and MN245721). Phylogenetic trees were constructed based on the concatenated sequences of EF1-α and RPB2 genes using neighbour-joining and maximum-likelihood algorithms with MEGA 7.0. Two similar tree topologies both showed isolate NEAU-Mf-10-2 clustered with F. proliferatum NRRL 43665. Therefore, isolate NEAU-Mf-10-2 was identified as F. proliferatum based on morphological characteristics and phylogenetic analysis. To fulfill Koch’s postulates, ten muskmelon fruits (var. Tianbao) were soaked in 2% NaClO for 2 min, and then washed three times with SDW. Muskmelon fruits were inoculated by injecting conidia suspension (200 μL, 1×106 spores/mL) with a sterile injector. Ten other surface sterilized muskmelon fruits inoculated with sterile water were used as control. The fruits were placed in a light incubator at 28℃ with 12h light cycles for 7 days. All inoculated fruits showed symptoms highly similar to those of infected muskmelon fruits observed in the field. No symptoms were observed on fruits used as control. The Fusarium isolates were successfully re-isolated from the symptomatic fruits, and identified based on above morphological and molecular biological methods. Previous studies have reported that F. proliferatum can infect Polygonatum cyrtonema, Salvia miltiorrhiza, Allium cepa, A. sativum, and so on. To our knowledge, this is the first report of F. proliferatum causing fruit rot on muskmelon in China, which will provide basic information for designing effective prevention and control strategies on this disease.

scholarly journals Incidence of Alternaria Species Associated with Watermelon Leaf Blight in Korea

2021 ◽  
Vol 37 (4) ◽  
pp. 329-338
Author(s):  
Oh-Kyu Kwon ◽  
A-Ram Jeong ◽  
Yong-Jik Jeong ◽  
Young-Ah Kim ◽  
Jaekyung Shim ◽  
...  
Keyword(s):  
Rna Polymerase Ii ◽  
Histone H3 ◽  
Its Region ◽  
Leaf Blight ◽  
Alternaria Leaf Blight ◽  
Brown Leaf Spot ◽  
Brown Leaf ◽  
Amplicon Size ◽  
Alternaria Species ◽  
His3 Gene

Alternaria leaf blight is one of the most common diseases in watermelon worldwide. In Korea, however, the Alternaria species causing the watermelon leaf blight have not been investigated thoroughly. A total of 16 Alternaria isolates was recovered from diseased watermelon leaves with leaf blight symptoms, which were collected from 14 fields in Korea. Analysis of internal transcribed spacer (ITS) region, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and RNA polymerase II second largest subunit (RPB2) were not competent to differentiate the Alternaria isolates. On the contrary, analysis of amplicon size of the histone H3 (HIS3) gene successfully differentiated the isolates into three Alternaria subgroups, and further sequence analysis of them identified three Alternaria spp. Alternaria tenuissima, A. gaisen, and A. alternata. Representative Alternaria isolates from three species induced dark brown leaf spot lesions on detached watermelon leaves, indicating that A. tenuissima, A. gaisen, and A. alternata are all causal agents of Alternaria leaf blight. Our results indicate that the Alternaria species associated watermelon leaf blight in Korea is more complex than reported previously. This is the first report regarding the population structure of Alternaria species causing watermelon leaf blight in Korea.

scholarly journals First report of Alternaria alternata causing brown leaf spot on wild rice (Oryza rufipogon) in China

Plant Disease ◽  
2021 ◽  
Author(s):  
Fei Teng Zhong ◽  
Yue Lian Liu ◽  
Dianfeng Zheng ◽  
Shili Lu
Keyword(s):  
Rna Polymerase Ii ◽  
Alternaria Alternata ◽  
Leaf Spot ◽  
Wild Rice ◽  
Disease Incidence ◽  
Morphological Characteristics ◽  
Oryza Rufipogon ◽  
Sterile Water ◽  
Brown Leaf Spot ◽  
Brown Leaf

Oryza rufipogon Griff is a wild rice germplasm that might contain genes valuable for rice breeding. In May to June 2019, a leaf disease on wild rice (O. rufipogon cv. ‘Haihong-12’) was observed in a 3.3 ha field in Zhanjiang (20.93° N, 109.79° E), Guangdong, China. Early symptoms were yellow spots from the tip of leaves. Later, the spots gradually expanded downward the entire leaf to turn brown in turn. Symptoms were found in the tillering to the grain-filling stages (Supplementary Figure 1). The disease incidence on plants was between 10% and 40%. Twenty diseased leaves were collected from the field. The margin of the diseased tissues was cut into 2 mm × 2 mm pieces, surface-disinfected with 75% ethanol and 2% sodium hypochlorite for 30 s and 60 s, respectively, and rinsed three times with sterile water before isolation. The tissues were plated onto potato dextrose agar (PDA) medium and incubated at 28 °C. After 5-day incubation, grayish fungal colonies appeared on PDA. Single-spore isolation method was used to recover pure cultures for three isolates (Aas-1, Aas-2, and Aas-3). The colonies first produced light-grayish aerial mycelia, which turned dark grayish upon maturity. Conidiophores were branched. Conidia were two to four in chains, dark brown, ovoid or ellipsoid, and mostly beakless; had one to four transverse and zero to three longitudinal septa; and measured within 7.0–18.5 (average = 12.5) × 3.0–8.8 (average = 4.5) μm (n = 30). Morphological characteristics of the isolates were consistent with the description of Alternaria alternata (Fr.) Keissler (Simmons 2007). The internal transcribed spacer (ITS) region, partial RNA polymerase II largest subunit (RPB2) gene, translation elongation factor, and glyceraldehyde-3-phosphate dehydrogenase were amplified with primers ITS1/ITS4, RPB2-6F/RPB2-7R, EF-1α-F/EF-1α-R, and GDF1/GDR1, respectively (Woudenberg et al. 2015). Amplicons were sequenced and submitted to GenBank (accession nos. MW042179 to MW042181, MW090034 to MW090036, MW090046 to MW090048, and MW091450 to MW091452, respectively). The sequences of the three isolates were 100% identical (ITS, 570/570 bp; RPB2, 1006/1006 bp; TEF, 254/254 bp and GADPH, 587/587 bp) with those of CBS 479.90 (accession nos. KP124319, KP124787, KP125095, and KP124174) through BLAST analysis. The sequences were also concatenated for phylogenetic analysis by maximum likelihood. The isolates clustered with A. alternata CBS 479.90 (Supplementary Figure 2). The fungus associated with brown leaf spot on wild rice was thus identified as A. alternata. Pathogenicity tests were done in a greenhouse at 24 °C–30 °C with 80% relative humidity. Individual rice plants (cv. ‘Haihong-12’) with three leaves were grown in 10 pots, with around 50 plants per pot. Five pots were inoculated by spraying a spore suspension (105 spores/mL) onto leaves until runoff occurred, and another five pots were sprayed with sterile water to serve as controls. The test was done three times. Disease symptoms were found on the leaves after 7 days. The tips of the leaves turned yellow and spread downward. Then, the whole leaf turned brown and dried out, but the controls stayed healthy. The pathogen was re-isolated from infected leaves and phenotypically identical to the original isolate Aas-1 to fulfill Koch’s postulates. To our knowledge, this report is the first one on A. alternata causing brown leaf spot on wild rice (O. rufipogon). The pathogen has the potential to reduce wild rice yields and future breeding should consider resistance to this pathogen.

Phylogenetic, Morphological, and Pathogenic Characterization of Alternaria Species Associated with Fruit rot of Mandarin in California

Plant Disease ◽  
2020 ◽  
Author(s):  
Fei Wang ◽  
Seiya Saito ◽  
Themis Michailides ◽  
Chang-Lin Xiao
Keyword(s):  
Phylogenetic Analysis ◽  
Rna Polymerase Ii ◽  
Dna Sequences ◽  
Phylogenetic Analyses ◽  
Morphological Characteristics ◽  
Central Valley ◽  
Fruit Rot ◽  
Postharvest Diseases ◽  
Plasma Membrane Atpase ◽  
Alternaria Species

Alternaria rot caused by Alternaria species is one of the major postharvest diseases of mandarin fruit in California. The aims of this study were to identify these Alternaria species using phylogenetic analyses and morphological characteristics and test their pathogenicity to mandarin. Decayed mandarin fruit exhibiting Alternaria rot symptoms were collected from three citrus fruit packinghouses in the Central Valley of California. In total, 177 Alternaria isolates were obtained from decayed fruit and preliminarily separated into three groups representing three species (A. alternata, A. tenuissima and A. arborescens) based on the colony characterization and sporulation patterns. To further identify these isolates, phylogenetic analysis was conducted based on DNA sequences of the second largest subunit of RNA polymerase II (RPB2), plasma membrane ATPase (ATPase) and Calmodulin gene regions in combination with morphological characters. Of the 177 isolates, 124 isolates (70.1%) were identified as A. alternata and 53 isolates (29.9 %) were A. arborescens. The isolates initially identified as A. tenuissima based on the morphological characteristics could not be separated from those of A. alternata in phylogenetic analysis and thus considered A. alternata. Pathogenicity tests showed that both Alternaria species were pathogenic on mandarin fruit at both 5°C and 20°C. Our results indicated that two Alternaria species, A. alternata and A. arborescens, were responsible for Alternaria rot of mandarin fruit in California with A. arborescens causing fruit rot on mandarin being reported for the first time.

scholarly journals First Report of Leaf Blight Caused by Phomopsis ipomoeae-batatas on Sweet Potato in Korea

Plant Disease ◽  
2012 ◽  
Vol 96 (11) ◽  
pp. 1701-1701 ◽  
Author(s):  
J. H. Park ◽  
M. J. Park ◽  
K. S. Han ◽  
H. D. Shin
Keyword(s):  
Sweet Potato ◽  
Ipomoea Batatas ◽  
Morphological Characteristics ◽  
Leaf Blight ◽  
Economic Losses ◽  
Minor Importance ◽  
Conidial Suspension ◽  
First Report ◽  
Close Phylogenetic Relationship ◽  
Two Samples

Ipomoea batatas (L.) Lam., belonging to the Convolvulaceae, is widely cultivated and used as an industrial resource as well as for food and feed worldwide (2). In September 2010, an unknown leaf blight was observed on leaves in Hoengseong County and Jecheon City in Korea. Symptoms were mostly observed in older leaves as cream to tan-brown lesions surrounded by purplish brown-to-dark brown margin. Each lesion was circular to irregular, not exceeding 10 mm, but coalesced to form larger lesions. Necrotic tissue fell out giving rise to shot-holes. A number of black pycnidia were present in the lesions of diseased leaves. The same symptoms were observed at several localities in Korea during 2010 and 2011 seasons. The voucher specimens (n = 5) were preserved in the Korea University Herbarium (KUS). Two isolates were obtained from the two samples (KUS-F25274 and KUS-F25361) and deposited in the Korean Agricultural Culture Collection (Accession Nos. KACC45680 and KACC45702). Pycnidia were amphigenous, but mostly epigenous, scattered, dark brown-to-rusty brown, globose, embedded in host tissue or partly erumpent, 110 to 170 μm in diameter, and with an ostiole of 25 to 40 μm in diameter. Alpha conidia were aseptate, lageniform, biguttulate, hyaline, and 5.5 to 8.0 × 3.5 to 4.5 μm. Beta conidia were absent. Based on the morphological characteristics, the fungus was consistent with Phomopsis ipomoeae-batatas Punith. (1,3). Preliminary identification of the fungal isolate was confirmed by molecular data. Genomic DNA was extracted from the two isolates. The D1/D2 region of 28S rDNA was amplified using the primers LROR and LR7, and sequenced. The resulting sequences of the two isolates were identical to each other, and were deposited in GenBank (Accession Nos. JX157848 and JX157849). A BLAST search showed that there was no matching sequence of P. ipomoeae-batatas. Therefore, these were the first 28S sequences for the species submitted to GenBank. The present sequences showed >98% similarity with 24 entries of Phomopsis spp. and Diaporthe spp. (teleomorph of Phomopsis spp.), indicating their close phylogenetic relationship. Pathogenicity was tested by spraying leaves of three potted plants with a conidial suspension (2 × 106 conidia/ml), which was harvested from a 3-week-old culture on potato dextrose agar. Control leaves were sprayed with sterile water. The plants were placed in a dew chamber at 24°C in darkness and continuous dew for the first 24 h and then moved to a greenhouse bench. After 10 days, leaf blight symptoms that were identical to those observed in the field started to develop on the leaves inoculated with the fungus. No symptoms were observed on control plants. P. ipomoeae-batatas was reisolated from the lesions of inoculated plants, confirming Koch's postulates. Occurrence of leaf blight caused by P. ipomoeae-batatas on sweet potato has been reported in many countries (1,3). To our knowledge, this is the first report of the disease in Korea. The economic losses are of minor importance, because the disease is mostly present toward the end of growing season; however, attention must be paid considering that the pathogen may reduce the quality of vines used as fodder. References: (1) C. A. Clark and J. W. Moyer. Compendium of Sweet Potato Diseases. The American Phytopathological Society. St. Paul, MN, 1988. (2) I. G. Mok et al. J. Plant Biotechnol. 36:202, 2009. (3) E. Punithalingam. Phomopsis ipomoeae-batatas. IMI Descriptions of Fungi and Bacteria. Sheet 739, 1982.

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