scholarly journals First Report of New Postharvest Rot in Ginger Rhizome by Aspergillus parvisclerotigenus in Pakistan

Plant Disease ◽  
2014 ◽  
Vol 98 (8) ◽  
pp. 1158-1158
Author(s):  
N. Akhtar ◽  
Z. A. Awan ◽  
A. Shoaib
Keyword(s):  
Nucleotide Sequence ◽  
Spore Suspension ◽  
Growth Media ◽  
Fungal Culture ◽  
Koch’S Postulates ◽  
First Report ◽  
Its Sequence Analysis ◽  
Initial Symptoms ◽  
Ginger Rhizome ◽  
Koch's Postulates

Ginger (Zingiber officinale) rhizome is widely used in Pakistan as a spice. During the summer of 2013, several ginger sellers in a local vegetable market of Lahore, Pakistan, reported a green powdery mass of an unidentified pathogen that rotted a considerable quantity of ginger in its packaging. As far as we know, this disease was limited to stored rhizomes and not reported in fields. A survey was conducted in August to September of 2013 in three different vegetable markets in Lahore to collect infected samples. From each of three survey points from individual markets, 20 bags (10 kg each) were selected randomly. Average incidence of decay (by weight) was found to be 45%. Initial symptoms appeared as discoloration, soft and slippery skin with abundant green sporulation. Ten samples (rhizomes) from each market were brought to the laboratory for further studies. Isolation of the causal agent was carried out on two growth media: malt extract agar (MEA) and Czapek Dox agar (CZA). Inoculation was carried out by direct transfer of visible green spores as well as transferring a small fragment of surface sterilized infected rhizome to the media. Inoculated media plates were incubated at 25°C for 3 to 4 days. Emerging fungal colonies were sub-cultured to get pure cultures. The fungal colony was powdery, green, 3.5 to 4 cm in diameter, and without zonation after 7 days of incubation. Sclerotia were brown to black and globose. Conidial heads were columnar and biseriate, occasionally unseriate. Conidiophores were 1 to 2.5 mm long. Vesicles were sub-globose to globose and 25 to 30 μm wide. Metulae were 12 to 18 μm high and phialides were 6 to 12 μm. Conidia were globose to sub-globose, green, and 4 to 5 μm in diameter. Based on morphology, the fungus was identified as Aspergillus parvisclerotigenus (1). The identity of the pathogen was confirmed by ITS sequence analysis of two different isolates. For this, ITS1-5.8S-ITS2 nucleotide sequence of ~560 bp was amplified using total fungal genomic DNA as a template and ITS1 forward (5′-TCCGTAGGTGAACCTGCGG-3′) and ITS4 reverse primer (5′-TCCTCCGCTTATTGATATGC-3′) (2). Sequences from both isolates were 100% similar with each other. A BLAST search showed that this sequence had 99% homology with that A. parvisclerotigenus CBS 121.62 (EF409240.1). A culture of the fungus was deposited in First Fungal Culture Bank of Pakistan (FCBP1352) and the nucleotide sequence of ITS region to GenBank (KJ445022). For completion of Koch's postulates, a spore suspension (105 spores/ml) from a 1-week-old culture was prepared. Ten surface-disinfested, air-dried ginger rhizomes were placed on sterilized wet blotting papers in a glass beaker and inoculated by spore suspension using a hand sprayer. Similarly, 10 control rhizomes were sprayed with sterile distilled water. Rhizomes were incubated at 25°C for 7 days. The experiment was replicated three times. The same symptoms noticed in the vegetable markets were observed in 80% of the inoculated rhizomes while control rhizomes remained healthy. Re-isolation of the pathogen from symptomatic rhizomes fulfilled Koch's postulates. Poor hygiene is thought to be the main cause of rotting; therefore, this disease is not a threat to ginger if stored properly. To our knowledge, this is the first report of postharvest ginger rhizome rot from Pakistan caused by A. parvisclerotigenus. References: (1) J. Varga et al. Stud. Mycol. 69:57, 2011. (2) T. J. White et al. In: PCR Protocols: A Guide to Methods and Applications, page 315. Academic Press, San Diego, CA, 1990.

scholarly journals First Report of a Leaf Spot Disease of Tobacco Caused by Pseudomonas cichorii in China

Plant Disease ◽  
2021 ◽  
Author(s):  
Dayu Lan ◽  
Fangling Shu ◽  
Yanhui Lu ◽  
Anfa Shou ◽  
Wei Lin ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Leaf Spot ◽  
Leaf Spot Disease ◽  
Pathogenicity Test ◽  
Pseudomonas Cichorii ◽  
Koch’S Postulates ◽  
First Report ◽  
Initial Symptoms ◽  
Wide Range ◽  
Koch's Postulates

Tobacco (Nicotiana tabacum L.), one of the chief commercial crops, is wildly cultivated worldwide. In June 2020 and 2021, an unknown bacterial leaf spot on tobacco was found in Hezhou and Hechi City, Guangxi, China. 30% of the tobacco were affected and the rate of diseased leaves reached about 10% in the field under high temperature and rainstorm. The disease mainly damaged the middle and top leaves of tobacco plants at vigorous growing stage. The initial symptoms were water-soaked spots on the frontal half of a leaf, and then expanded into circular to irregular spots with a yellow halo at the edge. The spots mostly appeared dark brown at high air humidity, while yellow brown at low humidity and exhibited a concentric pattern. In severe cases, the lesions coalesced and the whole leaf was densely covered with lesions, resulting in the loss of baking value. A bacterium was consistently isolated from diseased leaf tissues on nutrient agar (NA). Growth on NA was predominantly grayish white circular bacterial colonies with smooth margins, and the bacterium is rod-shaped, gram-negative and fluorescent on King’s B medium. Seven isolates (ND04A-ND04C and ZSXF02-ZSXF05) were selected for molecular identification and pathogenicity tests. Genomic DNA of the bacterium was extracted and the housekeeping gene of cts (encoding citrate synthase) was amplified with the primers cts-Fs/cts-Rs (forward primer cts-Fs: 5’-CCCGTCGAGCTGCCAATWCTGA-3’; reverse primer cts-Rs: 5’-ATCTCGCACGGSGTRTTGAACATC-3’) (Berge et al. 2014; Sarkar et al. 2004). 409-bp cts gene sequences were deposited in the GenBank database for seven isolates (accession no. OK105110-OK105116). Sequence of seven isolates shared 100% identity with several Pseudomonas cichorii strains within the GenBank database (accession no. KY940268 and KY940271), and the phylogenetic tree of cts genes of the seven isolates clustered with the phylogroup 11 of Pseudomonas syringae (accession no. KJ877799 and KJ878111), which was classified as P.cichorii. To satisfy Koch’s postulates, a pathogenicity test was tested by using a needle to dip a suspension of the bacterium (108 CFU/ml) and pricking three holes in the tobacco leaf. The control plants leaves were needled with sterile water. Each tobacco plant was inoculated with three leaves, and the test was repeated three times. All plants were placed in transparent plastic boxes and incubated in a greenhouse at 25 ± 3°C. The water-soaked spots appeared 24h after inoculation and quickly expanded through leaf veins. Three days after inoculation, all the inoculated leaves showed symptoms similar to those observed in the field. Control plants remained healthy. Only P. cichorii was successfully re-isolated from the lesions, confirming Koch’s postulates. Pseudomonas cichorii can infect eggplant, lettuce, tomatoand other crops, and has a wide range of hosts (Timilsina et al. 2017; Ullah et al. 2015). To our knowledge, this is the first report of P. cichorii causing leaf spot on tobacco in China.

scholarly journals First Report of Aspergillus niger Causing Root Rot of Peanut in China

Plant Disease ◽  
2015 ◽  
Vol 99 (2) ◽  
pp. 284-284 ◽  
Author(s):  
M. L. Xu ◽  
J. G. Yang ◽  
J. X. Wu ◽  
Y. C. Chi ◽  
L. H. Xie
Keyword(s):  
Aspergillus Niger ◽  
Root Rot ◽  
Genomic Dna ◽  
Dense Layer ◽  
Causal Organism ◽  
Centraalbureau Voor ◽  
Koch’S Postulates ◽  
First Report ◽  
Initial Symptoms ◽  
Koch's Postulates

Peanut (Arachis hypogaea) is one of the most important oil crops and food legumes worldwide. China sows approximately 3.5 million hectares each year and produces 40% of the world's peanuts. Fungal diseases are among the main biotic stresses affecting peanut production. Root rot is a serious disease caused by several fungi. Pythium spp., Fusarium spp., and Rhizopus spp. are some of the root rot fungi that have been reported in China. In 2012 and 2013, root rot symptoms were observed in several fields in Laixi District, Qingdao City, Shandong Province, China. The first symptoms appeared in July. Initial symptoms of the disease were brown spots on the stem base and root. Affected plants were stunted, with leaf chlorosis, reduced growth, or sudden wilting. As disease progressed, the infected tissues showed brown discoloration and rot, and abundant dark brown and black powdery spores were visible on the surfaces of affected parts. Eventually, affected plants collapsed and died. To isolate the causal organism, roots and stems were cut into sections, which were surface-disinfected with 70% ethanol solution (v/v) for 20 s, soaked in 0.1% mercuric chloride solution for 50 s, rinsed with sterilized water three times, dried, placed on Czapek's Dox agar supplemented with chloramphenicol (100 μg/ml), and incubated at 28°C for 7 days. Fungal colonies were white initially and then covered with a dense layer of dark brown or black conidial heads. The conidial head was radiate; vesicles were nearly spherical and covered with irregular metulae and phialides. Conidia were globose or subglobose (3.0 to 5.5 μm in diameter), dark brown to black, with rough cell walls. Total genomic DNA was extracted from mycelia using the EasyPure Genomic DNA Kit (TransGEN, Beijing, China). The rDNA-ITS region was amplified using PCR with the universal fungal primers ITS1 and ITS4 (2). The purified products were separately sequenced in both directions using the same primer pair. The sequences (GenBank Accession No. KJ848716) obtained were 99% similar to the ITS sequence of isolates of Aspergillus niger. This, together with the morphological characters (1) described above, suggested that the microorganism we had isolated was A. niger. Koch's postulates were completed in the laboratory by inoculating peanut. Thirty Huayu20 peanut seeds were placed in a 500-ml sterile pot with 300 g of autoclaved soil. Twenty days after seedling emergence, 15 peanut plants were wounded with a needle and inoculated with 5 ml of conidia suspension (106 ml−1). The same number of peanuts were similarly wounded and inoculated with 5 ml of sterile distilled water to serve as controls in the same pot. All peanuts were kept in a randomized complete block design at 30°C under a 12-h photoperiod. After 7 days, disease symptoms similar to those observed in the field appeared in all inoculated but not in non-inoculated peanuts. The tests were repeated three times in the greenhouse. Koch's postulates were satisfied after re-isolating the A. niger from inoculated peanuts using the method described above. To our knowledge, this is the first report of A. niger causing root rot in peanut in China. References: (1) M. A. Klich. Page 12 in: Identification of Common Aspergillus Species. Centraalbureau voor Schimmelcultures, Utrecht, The Netherlands, 2002. (2) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, CA, 1990.

scholarly journals First Report of Sclerotinia Stem and Twig Blight Caused by Sclerotinia sclerotiorum on Citrus volkameriana Rootstock in Italy

Plant Disease ◽  
2011 ◽  
Vol 95 (8) ◽  
pp. 1030-1030 ◽  
Author(s):  
G. Polizzi ◽  
D. Aiello ◽  
G. Scuderi ◽  
G. Cirvilleri
Keyword(s):  
Relative Humidity ◽  
Sclerotinia Sclerotiorum ◽  
Aesthetic Quality ◽  
Koch’S Postulates ◽  
First Report ◽  
Volkamer Lemon ◽  
Initial Symptoms ◽  
Twig Blight ◽  
Citrus Volkameriana ◽  
Koch's Postulates

Volkamer lemon (Citrus volkameriana Ten. & Pasq., Rutaceae family) is the most commonly used rootstock for some ornamental citrus (oval kumquat and calamondin), improving the aesthetic quality of the plants and their marketable value. During the winter of 2011, symptoms of stem blight were observed on approximately 10% of 12,000 1-year-old potted C. volkameriana seedlings grown in different blocks in a commercial nursery near Catania (eastern Sicily, Italy). In the same nursery, only 1% of 15,000 older seedlings (2-year-old) showed disease symptoms. Initial symptoms included gray lesions on stems and occasionally on twigs. Later, buff lesions and gum exude appeared. Symptomatic stems and twigs were usually girdled and killed. In the lesions, irregular, dark gray sclerotia (1.0 to 5 × 1.0 to 7.0 mm, average 2.5 × 3.9 mm) were produced. In high relative humidity, cottony, white mycelia on the bark surface of infected tissues were also observed. Isolations were performed by transferring approximately 300 fragments of symptomatic tissues from 15 C volkameriana seedlings, surface-sterilized with 1% NaClO for 1 min, on potato dextrose agar (PDA) amended with 100 mg/liter of streptomycin sulfate. Sclerotinia sclerotiorum (Lib.) de Bary was recovered from all infected plants. Colony type, morphology, and dimensions of sclerotia were examined on PDA at 22 ± 1°C after 10 days in the dark. Sclerotia produced on PDA measured 2.0 to 7.0 × 1.5 to 4.0 mm (average 5.6 × 2.6 mm). DNA isolation was performed with the DNA Purification Kit (Puragene-Gentra, Minneapolis, MN) following the manufacturer's instructions. Amplification and sequencing of the internal transcribed spacer (ITS) region of rDNA was performed with primers ITS1/ITS4 (2). BLAST analysis of the 550-bp segment showed a 98% homology with S. sclerotiorum strain ms85 (GenBank Accession No HQ833450.1), thus confirming identification based on morphology. Koch's postulates were fulfilled by pathogenicity tests carried out on 20 1-year-old potted C. volkameriana seedlings. Each seedling was inoculated with five mycelial agar plugs (6 mm in diameter) and five sclerotia from the edge of 10-day-old colonies on PDA and placed in wounds made with a sterile blade in the bark of stem and twigs. Inoculated wounds (10 for each plant) were wrapped with Parafilm. The same number of control plants were wounded and inoculated with sterile PDA plugs. All inoculated plants were incubated in a growth chamber at 22°C with 80 to 90% relative humidity for 14 days. Blight symptoms and lesions on the stem and twigs identical to those observed in the nursery developed on all plants with both types of inoculum. Noninoculated control plants remained symptomless. S. sclerotiorum was reisolated from all symptomatic tissues and identified by morphology as previously described, completing Koch's postulates. To our knowledge, this is the first report of S. sclerotiorum stem and twig blight on C. volkameriana. Worldwide, Sclerotinia stem and twig blight is considered a minor disease on citrus (1), but this evidence suggests that in eastern Sicily, S. sclerotiorum may be an important pathogen of young C. volkameriana seedlings in nurseries. References: (1) J. A. Menge. Page 35 in: Compendium of Citrus Diseases. 2nd ed. The American Phytopathological Society, St. Paul, MN, 2000. (2) T. J.White et al. Page 315in: PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al., eds. Academic Press, San Diego, 1990.

scholarly journals First Report of Leaf Spot Caused by Didymella americana on Cassia nomame in China

Plant Disease ◽  
2021 ◽  
Author(s):  
Weiming Sun ◽  
Lina Feng ◽  
Xiaolei Wen ◽  
Bojia Han ◽  
Danrun Xing ◽  
...  
Keyword(s):  
Sequence Analysis ◽  
Leaf Spot ◽  
Disease Incidence ◽  
Morphological Characteristics ◽  
Rrna Gene ◽  
Pathogenicity Test ◽  
Koch’S Postulates ◽  
First Report ◽  
Initial Symptoms ◽  
Koch's Postulates

Cassia nomame (Sieb.) Kitagawa is an annual plant in the Leguminousae family. The aerial parts of C. nomame have been used as tonic and diuretic in Korea and Japan (Syed et al. 2019). A leaf spot was observed on the leaves of a 1-year-old C. nomame landrace in Changli County (39.42°N, 119.10°E), Qinhuangdao City, Hebei Province during August to October in 2018. In many fields (n≥3), the disease incidence over 80% in the middle and late stage of plant growth. Symptoms on leaves in one field began with many small, dark necrotic spot lesions. Later, the lesions spread to round-to-oval, slightly sunken in the center, and large necrotic patches with indefinite margins. Finally, lesions coalesced and resulted in defoliation. Lesions were occasionally observed on the pods. Symptoms on the pods were initially small, dark spots and then expanded to large necrotic patches with irregular edges. Symptomatic tissues (n=32) from pods and leaves were cut into 3 to 8 mm2 squares, surface disinfested with 75% ethanol for 10 s, rinsed with sterile distilled water, then placed on potato dextrose agar (PDA) at 28℃. After 3 days, ten isolates with consistent characteristics were obtained with a frequency 52.6%. The isolates on PDA were round, initially pale and had little aerial mycelium, gradually turned olive green and had dense wool-like dense aerial mycelia after 3 days. Conidia were hyaline, smooth, solitary, and elliptical. The conidia measured 5.4 to 8.2 μm × 2.5 to 3.8 μm (n=50), and has two oil bodies positioning at opposite poles. Pigmented chlamydospores were spherical or nearly pear-shaped, and solitary. Black fructifications (pycnidia) were produced profusely on PDA after subculture for 3 days. All the isolates were similar to Didymella sp. in morphology (Aveskamp et al. 2009). Choice three isolates YSGUO8 YSGGUO8-a and YSGGUO8-b to be further characterized by sequencing of the internal transcribed spacer (ITS), actin gene, and 28S large subunit of the nuclear rRNA gene (LSU) (Zhang et al. 2017). The sequences of three strains (MK836417 MZ484072 and MZ484073 for ITS, MK837604 MZ593675 and MZ593676 for actin, MK843781 MZ836208 and MZ836207 for LSU, respectively) showed 99% to 100% similarity with Didymella americana K-004 (KY070279 for ITS,KY070285 for LSU), Phoma americana CBS 256.65 (FJ426973 for ITS, FJ426871 for actin, MH870196 for LSU) and P. americana CBS 185.85 (FJ426972 for ITS, FJ426870 for actin, GU237990 for LSU) in GenBank. The fungi were identified as D. americana (formerly P. americana or Peyronellaea americana) on the basis of morphological characteristics and sequence analysis. A pathogenicity test was conducted with three times on 1-year-old C. nomame strain at the 4 to 6 compound leaf stage. Conidia were obtained from 7-day-old PDA cultures grown at 28℃ with a 12-h photoperiod. Koch’s postulates were fulfilled by spray inoculating ten healthy young plants with 106 conidia per milliliter of D. americana strain YSGUO8, and sterile water as the control. After inoculation, the plants were managed at 28℃, 60% relative humidity and a 12-h photoperiod. After 5 to 8 days, the inoculated leaves developed small and dark spots lesions similar to those observed on the leaves with initial symptoms in the field. The control leaves remained symptomless. The same fungi were re-isolated from infected leaves by morphology observation and sequence analysis, confirming Koch's postulates. D. americana has caused leaves spot on Table Beet in New York (Vaghefi et al. 2016). To our knowledge, this is the first report of D. americana causing leaf spot of C. nomame in China.

First Report of Pathogenicity of Fusarium sporotrichioides and Fusarium acuminatum on Sunflowers in the United States

2010 ◽  
Vol 11 (1) ◽  
pp. 42 ◽  
Author(s):  
F. Mathew ◽  
B. Kirkeide ◽  
T. Gulya ◽  
S. Markell
Keyword(s):  
United States ◽  
Helianthus Annuus ◽  
The United States ◽  
Fusarium Sporotrichioides ◽  
Charcoal Rot ◽  
Koch’S Postulates ◽  
First Report ◽  
Fusarium Acuminatum ◽  
Helianthus Annuus L ◽  
Koch's Postulates

Widespread infection of charcoal rot was observed in a commercial sunflower field in Minnesota in September 2009. Based on morphology, isolates were identified as F. sporotrichioides and F. acuminatum. Koch's postulates demonstrated pathogencity of both species. To our knowledge, this is the first report of F. sporotrichoides and F. acuminatum causing disease on Helianthus annuus L. in the United States. Accepted for publication 23 August 2010. Published 15 September 2010.

scholarly journals First Report of Stemphylium botryosum Causing Leaf Blight of Kiwi in the Province Imathia, Northern Greece

Plant Disease ◽  
2008 ◽  
Vol 92 (4) ◽  
pp. 650-650 ◽  
Author(s):  
T. Thomidis ◽  
T. J. Michailides
Keyword(s):  
Apical Cell ◽  
Morphological Characteristics ◽  
Leaf Blight ◽  
Width Ratio ◽  
Northern Greece ◽  
Cell Width ◽  
Koch’S Postulates ◽  
First Report ◽  
Stemphylium Botryosum ◽  
Koch's Postulates

In Greece, kiwi (Actinidia deliciosa) is mostly found in the northern part of the country where approximately 440,000 ha are grown. In the summer of 2006, a Stemphylium sp. was frequently isolated from leaves of kiwi (cv. Hayward) grown in the province of Imathia. Symptomatic leaves were covered with irregular, necrotic, brown areas. Lesions had a distinct margin that, in some cases, covered a wide part of the diseased leaves. Intense symptoms were frequently observed and associated with defoliation. This Stemphylium sp. was consistently isolated from diseased leaves onto potato dextrose agar (PDA) after surface sterilization with 0.1% chlorine solution. On the basis of morphological characteristics of mycelia, dimensions (length 20 to 29 μm and width 14 to 21 μm) and mean length/width ratio (1.42 μm) of conidia, and width and apical cell width of condiophores, the fungus was identified as Stemphylium botryosum (Wallr.) (2,3) Koch's postulates were completed in the laboratory by inoculating leaves of kiwi (cv. Hayward) with an isolate of S. botryosum originated from a symptomatic leaf of a Hayward kiwi. Twenty leaves were surface sterilized by dipping them into 0.1% chlorine solution for 2 to 3 min, washing in sterile distilled water, and allowing them to dry in a laminar flow hood. A leaf was then placed into a petri plate containing a wet, sterilized paper towel. Inoculation was made by transferring a 5-mm-diameter mycelial disc from the margins of a 7-day-old culture onto the center of each leaf surface. Petri plates were closed and incubated at 25°C with 12 h of light for 6 days. Koch's postulates were satisfied when the same S. botryosum was reisolated from 100% of inoculated leaves that developed symptoms similar to those observed in the vineyards. Leaves inoculated with a PDA plug alone (with no S. botryosum) did not develop any symptoms. Previously, Alternaria alternata was reported as the causal agent of a leaf spot pathogen of kiwi (1,4). To our knowledge, this is the first report of the occurrence of S. botryosum causing leaf blight of kiwi in Greece and worldwide. This pathogen can cause a high level of defoliation in diseased plants. References: (1) L. Corazza et al. Plant Dis. 83:487, 1999. (2) M. B. Ellis. Dematiaceous Hyphomycetes. Mycology Institute. London, England, 1971. (3) E. G. Simmons. Mycologia 61:1, 1969. (4) C. Tsahouridou and C. C. Thanassoulopoulos. Plant Dis. 84:371, 2000

scholarly journals First report of Pestalotiopsis diospyri causing canker on persimmon trees

2011 ◽  
Vol 33 (3) ◽  
pp. 1019-1022 ◽  
Author(s):  
Giselda Alves ◽  
Francineia Silva Verbiski ◽  
Themis J. Michaelides ◽  
Louise Larissa May-de Mio
Keyword(s):  
Diospyros Kaki ◽  
Southern Brazil ◽  
Severe Damage ◽  
Santa Catarina ◽  
Koch’S Postulates ◽  
Canker Disease ◽  
First Report ◽  
Koch's Postulates

During 2006 to 2009 season symptoms of a canker disease were observed on twigs and branches of young and mature persimmon trees (Diospyros kaki L.) cv. Fuyu in the States of Santa Catarina and Paraná in the Southern Brazil. The cankers result in severe damage and reduced production. Isolations from the margins of these cankers revealed a genus of Pestalotiopsis. Koch's postulates were confirmed using two isolates of the pathogen which was identified as Pestalotiopsis diospyri.

scholarly journals First Report of Wilt of Rubber Tree Caused by Chalaropsis thielavioides in China

Plant Disease ◽  
2020 ◽  
Author(s):  
Xue Li ◽  
Jie Li ◽  
Hua Yong Bai ◽  
Kecheng Xu ◽  
Ruiqi Zhang ◽  
...  
Keyword(s):  
Rubber Tree ◽  
Morphological Characteristics ◽  
Spore Suspension ◽  
Malt Extract ◽  
Pathogenicity Test ◽  
Distilled Water ◽  
Ceratocystis Fimbriata ◽  
First Report ◽  
Mould Fungus ◽  
Its Sequence Analysis

Rubber tree (Hevea brasiliensis (Willd. ex Adr. Juss) Müll. Arg.) is used for the extraction of natural rubber and is an economically and socially important estate crop commodity in many Asian countries such as Indonesia, Malaysia, Thailand, India, Sri Lanka, China and several countries in Africa (Pu et al, 2007). Xishuangbanna City and Wenshan City are the main rubber cultivation areas in Yunnan Province, China. In November 2012, rubber tree showing typical wilt symptoms (Fig. 1 A) and vascular stains (Fig. 1 B) were found in Mengla County, Xishuangbanna City. This disease was destructive in these trees and plant wilt death rate reached 5%. The diseased wood pieces (0.5cm long) from trunk of rubber was surface disinfected with 75% ethanol for 30s and 0.1% mercuric chloride (HgCl2) for 2min, rinsed three times with sterile distilled water, plated onto malt extract agar medium (MEA), and incubated at 28℃. After 7 days, fungal-like filaments were growing from the diseased trunk. Six cultures from 6 rubber trunk were obtained and incubated on MEA at 28℃, after 7 days to observe the cultural features. The mycelium of each culture was white initially on MEA, and then became dark green. Cylindrical endoconidia apices rounded, non-septate, smooth, single or borne in chains (8.9 to 23.6 × 3.81 to 6.3μm) (Fig. 1 C). Chlamydospores (Fig. 1 D) were abundant, thick walled, smooth, forming singly or in chains (11.1 to 19.2 × 9.4 to 12.0μm). The mould fungus was identifed as Chalaropsis based on morphology (Paulin-Mahady et al. 2002). PCR amplification was carried out for 3 isolates, using rDNA internal transcribed spacer (ITS) primer pairs ITS1F and ITS4 (Thorpe et al. 2005). The nucleotide sequences were deposited in the GenBank data base and used in a Blast search of GenBank. Blast analysis of sequenced isolates XJm8-2-6, XJm8-2 and XJm10-2-6 (accessions KJ511486, KJ511487, KJ511489 respectively) had 99% identity to Ch. thielavioides strains hy (KF356186) and C1630 (AF275491). Thus the pathogen was identified as Ch. thielavioides based on morphological characteristics and rDNA-ITS sequence analysis. Pathogenicity test of the isolate (XJm8-2) was conducted on five 1-year-old rubber seedlings. The soil of 5 rubber seedlings was inoculated by drenching with 40 ml spore suspension (106 spores / ml). Five control seedlings were inoculated with 40 ml of sterile distilled water. All the seedlings were maintained in a controlled greenhouse at 25°C and watered weekly. After inoculated 6 weeks, all the seedlings with spore suspension produced wilt symptoms, as disease progressed, inoculated leaves withered (Fig. 1 E) and vascular stains (Fig. 1 F) by 4 months. While control seedlings inoculated with sterile distilled water remained healthy. The pathogen re-isolated from all inoculated symptomatic trunk was identical to the isolates by morphology and ITS analysis. But no pathogen was isolated from the control seedlings. The pathogenicity assay showed that Ch. thielavioides was pathogenic to rubber trees. Blight caused on rubber tree by Ceratocystis fimbriata previously in Brazil (Valdetaro et al. 2015), and wilt by Ch. thielavioides was not reported. The asexual states of most species in Ceratocystis are “chalara” or “thielaviopsis” (de Beer et al. 2014). To our knowledge, this is the first report of this fungus causing wilt of rubber in China. The spread of this disease may pose a threat to rubber production in China.

Red Crown Rot of Hop in Oregon Caused by Phomopsis tuberivora

2013 ◽  
Vol 14 (1) ◽  
pp. 52
Author(s):  
David H. Gent ◽  
George Mueller-Warrant ◽  
Joanna L. Woods ◽  
Melodie L. Putnam ◽  
Megan C. Twomey
Keyword(s):  
Crown Rot ◽  
Management Implications ◽  
Koch’S Postulates ◽  
First Report ◽  
Red Crown Rot ◽  
Weak Growth ◽  
Koch's Postulates

During July 2007, symptoms including weak growth and death of plants of cultivar Fuggle were reported by a hop grower in Marion Co., OR. Phomopsis tuberivora H.T. Güssow & W.R. Foster 1932 was consistently recovered from affected plants. Koch's postulates were fulfilled with three isolates of the fungus, establishing the pathogen and the disease red crown rot as the cause of the damage. This is the first report of red crown rot on hop in Oregon, which may have important management implications for affected hop yards and farms. Accepted for publication 19 March 2013. Published 24 June 2013.

First Report of Phytophthora ramorum Infecting Grand fir in California

2011 ◽  
Vol 12 (1) ◽  
pp. 37
Author(s):  
Kathleen L. Riley ◽  
Gary A. Chastagner ◽  
Cheryl Blomquist
Keyword(s):  
Phytophthora Ramorum ◽  
Christmas Tree ◽  
Native Range ◽  
Tree Plantation ◽  
Koch’S Postulates ◽  
First Report ◽  
Stem Lesions ◽  
Koch's Postulates

Phytophthora ramorum was detected on grand fir in 2003 and 2005 in a Christmas tree plantation near Los Gatos, CA, in association with infected California bay laurel. Isolates derived from stem lesions were used to inoculate grand fir seedlings in two tests. Isolations from lesions on inoculated plants were positive for P. ramorum in both tests. This work provides the completion of Koch's postulates to establish grand fir as a host of P. ramorum. The potential for grand fir to be infected within its native range is unknown. Accepted for publication 1 February 2011. Published 1 April 2011.

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