scholarly journals First report of soft rot of Aconitum carmichaelii caused by Pectobacterium brasiliense in China

Plant Disease ◽  
2021 ◽  
Author(s):  
Hao Zhang ◽  
Yang Xu ◽  
Dan Zhao ◽  
Yuwen Yang ◽  
Tingchang Zhao ◽  
...  
Keyword(s):  
Cell Suspension ◽  
Lateral Roots ◽  
Soft Rot ◽  
Negative Control ◽  
Likelihood Method ◽  
Pathogenicity Test ◽  
Sterile Water ◽  
First Report ◽  
Carotovorum Subsp ◽  
Aconitum Carmichaelii

Aconitum carmichaelii Debx. is a Chinese traditional medicine herb, and is widely planted in China. The processed lateral roots of A. carmichaelii is known as Fuzi, and is used for the treatment of pain and inflammation in the joints (Zhou et al., 2015). In July 2019, a high incidence (approximately 50-100%) of soft rot of A. carmichaelii was observed in several commercial fields in Jiangyou County of Szechuan Province of China. Soft rot brownish lesions developed on infected stems, leading to collapse and wilting of entire plants. From symptomatic plants, the margins between the diseased and healthy areas were cut into pieces (5 × 5 mm), which were surface sterilized using 75% ethanol for 30 s and 2% NaOCl for 1 min, followed by three rinses with sterile water. The sterilized sections were macerated in drops of sterile water, and the extract was streaked onto King’s B (KB) agar medium and incubated for 48 h at 30°C. Single colonies that are round, convex and creamy on the plates after 2 days were streaked on KB agar plates. Ten bacterial strains were isolated, and the strain Fuzi915 was chosen for further analyses. The 16S rDNA gene sequence (GenBank accession MZ881946) amplified by primer pair 27F/1492R (Monciardini et al., 2002) showed 99.85% identity to the sequence of Pectobacterium brasiliense (syn. Pectobacterium carotovorum subsp. brasiliense, Pcb) strain HNP201736 (MN393938.1) and P. carotovorum subsp. carotovorum strain PJP201706 (MN394020.1), respectively, and also showed 99.78% identity to P. brasiliense strain SX309 (CP020350.1). To further identify the Fuzi915 strain, the PCR assay was carried out using primer pairs Y1/Y2, EXPCCF/EXPCCR and BR1f/L1r (De Boer and Ward, 1995; kang et al., 2003; Duarte et al., 2004), specific to P. carotovorum, P. carotovorum subsp. carotovorum and P. carotovorum subsp. brasiliense (Pcb), respectively. Specific fragments of 434 bp and 322 bp were amplified by the Y1/Y2 and BR1f/L1r primer sets, receptively, but there was no amplification by the EXPCCF/EXPCCR primer set, indicating that the Fuzi915 strain belongs to Pcb (Onkendi and Moleleki, 2014). Additional phylogenetic trees based on two housekeeping genes mdh (MZ892962) and gapA (MZ892963) were constructed using Maximum-likelihood method with 1000 bootstraps. The Fuzi915 strain clustered with all P. brasiliense strains including type strain P. brasiliense BC1. Further, a pathogenicity test was conducted on healthy A. carmichaelii roots and seedlings maintained in a growth chamber at 25°C and 95% humidity. Root inoculation was followed by drenching 107 CFU/ml of the cell suspension of Fuzi915 strain in soil surrounding the A. carmichaelii roots. Ten roots were inoculated with cell suspension while 10 roots were drenching inoculated with sterile water as negative control. Stem inoculation was followed by injecting 103 CFU/ml of the cell suspension in the stem of 10 A. carmichaelii seedlings, while 10 were injected with sterile water as negative control. After 5 days, Pcb-inoculated roots became brown and soft, and Pcb-inoculated seedlings became wilted and water soaked and started to collapse, similar to symptoms observed in the field. No symptoms were observed on the control plants inoculated with sterile water. The strain was re-isolated successfully from symptomatic A. carmichaelii and was identified as P. brasiliense by using PCR with the same primers to complete Koch’s postulates. To our knowledge, this is the first report of the soft rot of A. carmichaelii caused by P. brasiliense in China.

scholarly journals First Report of Bipolaris oryzae Causing Leaf Spot on Cultivated Wild Rice (Oryza rufipogon) in China

Plant Disease ◽  
2021 ◽  
Author(s):  
Yue Lian Liu ◽  
Jian Rong Tang ◽  
Ya Li ◽  
Hong Kai Zhou
Keyword(s):  
Leaf Spot ◽  
Wild Rice ◽  
Morphological Characteristics ◽  
Oryza Rufipogon ◽  
Likelihood Method ◽  
Leaf Spot Disease ◽  
Pathogenicity Test ◽  
Sterile Water ◽  
Bipolaris Oryzae ◽  
First Report

Wild rice (Oryza rufipogon) has been widely studied and cultivated in China in recent years due to its antioxidant activities and health-promoting effects. In December 2018, leaf spot disease on wild rice (O. rufipogon cv. Haihong-12) was observed in Zhanjiang (20.93 N, 109.79 E), China. The early symptom was small purple-brown lesions on the leaves. Then, the once-localized lesions coalesced into a larger lesion with a tan to brown necrotic center surrounded by a chlorotic halo. The diseased leaves eventually died. Disease incidence was higher than 30%. Twenty diseased leaves were collected from the fields. The margin of diseased tissues was cut into 2 × 2 mm2 pieces, surface-disinfected with 75% ethanol for 30 s and 2% sodium hypochlorite for 60 s, and then rinsed three times with sterile water before isolation. The tissues were plated on potato dextrose agar (PDA) medium and incubated at 28 °C in the dark for 4 days. Pure cultures were produced by transferring hyphal tips to new PDA plates. Fifteen isolates were obtained. Two isolates (OrL-1 and OrL-2) were subjected to further morphological and molecular studies. The colonies of OrL-1 and OrL-1 on PDA were initially light gray, but it became dark gray with age. Conidiophores were single, straight to flexuous, multiseptate, and brown. Conidia were oblong, slightly curved, and light brown with four to nine septa, and measured 35.2–120.3 µm × 10.3–22.5 µm (n = 30). The morphological characteristics of OrL-1 and OrL-2 were consistent with the description on Bipolaris oryzae (Breda de Haan) Shoemaker (Manamgoda et al. 2014). The ITS region, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and translation elongation factor (EF-1α) were amplified using primers ITS1/ITS4, GDF1gpp1/GDR1 gdp2 (Berbee et al. 1999), and EF-1α-F/EF-1α-R EF-1/EF-2 (O’Donnell 2000), respectively. Amplicons of OrL-1 and OrL-2 were sequenced and submitted to GenBank (accession nos. MN880261 and MN880262, MT027091 and MT027092, and MT027093 and MT027094). The sequences of the two isolates were 99.83%–100% identical to that of B. oryzae (accession nos. MF490854，MF490831，MF490810) in accordance with BLAST analysis. A phylogenetic tree was generated on the basis of concatenated data from the sequences of ITS, GAPDH, and EF-1α via Maximum Likelihood method, which clustered OrL-1 and OrL-2 with B. oryzae. The two isolates were determined as B. oryzae by combining morphological and molecular characteristics. Pathogenicity test was performed on OrL-1 in a greenhouse at 24 °C to 30 °C with 80% relative humidity. Rice (cv. Haihong-12) with 3 leaves was grown in 10 pots, with approximately 50 plants per pot. Five pots were inoculated by spraying a spore suspension (105 spores/mL) onto leaves until runoff occurred, and five pots were sprayed with sterile water and used as controls. The test was conducted three times. Disease symptoms were observed on leaves after 10 days, but the controls remained healthy. The morphological characteristics and ITS sequences of the fungal isolates re-isolated from the diseased leaves were identical to those of B. oryzae. B. oryzae has been confirmed to cause leaf spot on Oryza sativa (Barnwal et al. 2013), but as an endophyte has been reported in O. rufipogon (Wang et al. 2015).. Thus, this study is the first report of B. oryzae causing leaf spot in O. rufipogon in China. This disease has become a risk for cultivated wild rice with the expansion of cultivation areas. Thus, vigilance is required.

scholarly journals First Report of Leaf Spots caused by Nigrospora oryzae on Wild Rice in China

Plant Disease ◽  
2021 ◽  
Author(s):  
Yue Lian Liu ◽  
Jian Rong Tang ◽  
Ya Li ◽  
Hong Kai Zhou
Keyword(s):  
Leaf Spot ◽  
Wild Rice ◽  
Morphological Characteristics ◽  
Oryza Rufipogon ◽  
Its Sequences ◽  
Likelihood Method ◽  
Pathogenicity Test ◽  
Sterile Water ◽  
First Report ◽  
Nigrospora Oryzae

In recent years, wild rice (Oryza rufipogon Griff) has been widely cultivated because of its health-promoting effects. In May 2019, leaf spot lesions on cv. Haihong-12 were observed in Zhanjiang (20.93N, 109.79E), China. Leaf symptoms were yellow-to-brown, oval or circular with a very distinctive, large yellow halo. Black spores appeared on the leaves with advanced symptoms. The lesions coalesced, causing the entire leaf to become blighted and die. Disease incidence reached approximately 10% in the fields (8 ha) surveyed. Twenty leaves with symptoms were collected and cut into pieces of 2 ×2 cm in size. They were surface-disinfected with 75% ethanol for 30 s and 2% sodium hypochlorite (NaOCl) for 60 s, rinsed three times with sterile water, blotted dry on sterile paper, plated on potato dextrose agar (PDA) medium, and incubated at 28°C in the dark for 4 days. Ten pure cultures were obtained by transferring hyphal tips to new PDA plates, and monosporic cultures were obtained from three isolates (Nos-1, Nos-2, and Nos-3). Those isolates exhibited very similar morphological characteristics on PDA. Colony of isolate Nos-1 was white at the early stage and became dark gray after 7 days. Conidia were produced from clusters of conidiophores, single celled, black, smooth, spherical, and 9.5 to 14.2 µm (average 10.6 µm ± 0.42) in diameter. Morphological characteristics of the isolates matched the description of Nigrospora oryzae Petch (Wang et al. 2017). The ITS region was amplified using primers ITS1 and ITS4 (White et al. 1990). Nucleotide sequences of isolates Nos-1, Nos-2, and Nos-3 deposited in GenBank under acc. nos. MW042173, MW042174, and MW042175, respectively, were 100% identical to N. oryzae (acc. nos. KX985944, KX985962; and KX986007). A phylogenetic tree generated based on the ITS sequences and using a Maximum Likelihood method with 1,000 bootstraps showed that these three isolates from wild rice were grouped with other N. oryzae isolates downloaded from GenBank (bootstrap = 100%) but away from other Nigrospora spp. Pathogenicity test was performed with these three isolates in a greenhouse at 24 to 30°C. Approximately 50 seedling of wild rice cv. Haihong-12 were grown in each pot. At the 3-leaf stage, plants in three pots were inoculated with each isolate by spraying a spore suspension (105 spores/ml) until runoff. Three pots sprayed with sterile water served as the controls. Each 3-pot treatment was separately covered with a plastic bag. The test was conducted three times. Diseased symptoms were observed on the inoculated leaves after 10 days while no disease was observed in the control plants. Morphological characteristics and the ITS sequences of fungal isolates re-isolated from the diseased leaves were identical to those of N. oryzae. N. oryzae has been reported to cause leaf spot on O. sativa (Wang et al. 2017), but not on O. rufipogon. Thus, this is the first report of N. oryzae causing leaf spot of O. rufipogon in China. The finding provides the information important for further studies to develop management strategies for control of this disease.

scholarly journals First Report of Bacterial Soft Rot of Horn Lian (Typhonium giganteum) Caused by Pectobacterium carotovorum subsp. carotovorum in Jilin Province of China

Plant Disease ◽  
2014 ◽  
Vol 98 (9) ◽  
pp. 1268-1268 ◽  
Author(s):  
J. Gao ◽  
N. Nan ◽  
Y. N. Liu ◽  
B. H. Lu ◽  
W. Y. Xia ◽  
...  
Keyword(s):  
Cell Suspension ◽  
16S Rdna ◽  
Soft Rot ◽  
Rdna Sequence ◽  
Jilin Province ◽  
Pectobacterium Carotovorum ◽  
Bacterial Soft Rot ◽  
16S Rdna Sequence ◽  
First Report ◽  
Carotovorum Subsp

Horn lian (Typhonium giganteum) is a perennial herb of the family Aracea and is commonly used for expelling phlegm and as an antispasmodic treatment. In August 2012, horn lian grown in Changchun, Jilin Province of China, exhibited soft rot disease with ~60% incidence and experienced great losses. Water-soaked and dark green lesions on leaves expanded along main veins. Semitransparent, water-soaked, and sunken lesions on stems expanded rapidly and caused the whole plant to collapse with a foul smell. Nine representative strains were isolated from infected leaves and stems on nutrient agar (NA) medium after 36 h incubation at 28°C (1). Colonies were round, shiny, grayish white, and convex on NA medium. All strains were gram-negative, non-fluorescent on King's B medium (KB), facultatively anaerobic, motile with three to six peritrichous flagella (observed by electron transmission microscope), positive for catalase and pectolytic activity test on potato slices, but negative for oxidase, urease, and lecithinase. Strains grew at 37°C and in yeast salts broth medium containing 5% NaCl. They also liquefied gelatin and reduced nitrate, but did not reduce sucrose. Strains were also negative for starch hydrolysis, malonate utilization, gas production from glucose and indole. Results were variable for the Voges-Proskauer test. The strains utilized sucrose, arabinose, fructose, D-galactose, D-glucose, inositol, lactose, D-mannose, D-mannitol, melibiose, rhamnose, salicin, trehalose, maltose, raffinose, glycerol, D-xylose, and cellobiose as carbon sources, but not melezitose, α-CH3-D-gluconate, sorbitol, or dulcitol. Species identity was confirmed by molecular characterization of one of the nine strains, DJL1-2. DNA GC content indicated by high performance liquid chromatography (HPLC) was 51.7%. The 16S rDNA sequence (KC07897) of DJL1-2 showed 99% identity to that of a Pectobacterium carotovorum subsp. carotovorum (Pcc) strain (CP001657) and the sequence of the 16S-23S rDNA spacer region (KJ623257) was 93% similar to that of another known strain of Pcc (CP003776). As a result, the strains were identified as Pcc (2). Pathogenicity of the nine strains was evaluated by spraying 1 ml of bacterial cell suspension (108 CFU/ml) onto healthy leaves and injecting 0.1 ml of cell suspension into stems of 3-year-old horn lian plants with a sterile pipette tip. Three seedlings were used for each strain and sterilized water served as negative controls. Pcc SMG-2 reference strain (from milk thistle) was also inoculated into horn lian leaves and stems. Inoculated plants were covered with plastic bags for 24 h in a greenhouse at 28 to 30°C. After 72 h, water-soaked lesions similar to the naturally infected plants were observed on leaves and stems inoculated by the nine isolated strains and Pcc SMG-2, while negative control plants remained symptomless. Biochemical tests and 16S rDNA sequence analysis confirmed that the re-isolated bacteria were Pcc. To our knowledge, this is the first report of Pcc causing bacterial soft rot of horn lian in Changchun, Jilin Province, China. References: (1) Z. D. Fang. Research Method of Phytopathology. China Agricultural Press, 1998. (2) N. W. Schaad, et al. Laboratory Guide for Identification of Plant Pathogenic Bacteria, 3rd ed. American Phytopathological Society, St. Paul, MN, 2001.

scholarly journals First Report of Pectobacterium wasabiae Causing Soft Rot of Cabbage in Malaysia

Plant Disease ◽  
2013 ◽  
Vol 97 (8) ◽  
pp. 1110-1110 ◽  
Author(s):  
E. Golkhandan ◽  
K. Sijam ◽  
S. Meon ◽  
Z. A. M. Ahmad ◽  
A. Nasehi ◽  
...  
Keyword(s):  
16S Rrna ◽  
Dna Sequences ◽  
Acid Production ◽  
Soft Rot ◽  
Economic Losses ◽  
Economic Damage ◽  
Bacterial Suspension ◽  
Pathogenicity Test ◽  
First Report ◽  
Carotovorum Subsp

Soft rot of cabbage (Brassica rapa) occurs sporadically in Malaysia, causing economic damage under the hot and wet Malaysian weather conditions that are suitable for disease development. In June 2011, 27 soft rotting bacteria were isolated from cabbage plants growing in the Cameron Highlands and Johor State in Malaysia where the economic losses exceeded 50% in severely infected fields and greenhouses. Five independent strains were initially identified as Pectobacterium wasabiae based on their inability to grow at 37°C, and elicit hypersensitive reaction (HR) on Nicotiana tabaccum and their ability to utilize raffinose and lactose. These bacterial strains were gram-negative, rod-shaped, N-acetylglucosaminyl transferase, gelatin liquefaction, and OPNG-positive and positive for acid production from D-galactose, lactosemelibiose, raffinose, citrate, and trehalose. All strains were negative for indole production, phosphatase activity, reducing sucrose, and negative for acid production from maltose, sorbitol, inositol, inolin, melezitose, α-methyl-D-glucoside, and D-arabitol. All the strains exhibited pectolytic activity on potato slices. PCR assays were conducted to distinguish P. wasabiae from P. carotovorum subsp. brasiliensis, P. atrosepticum, and other Pectobacterium species using primers Br1f/L1r (2), Eca1f/Eca2r (1), and EXPCCF/EXPCCR, respectively. DNA from strains did not yield the expected amplicon with the Br1f/L1r and Eca1f/Eca2r, whereas a 550-bp amplicon typical of DNA from P. wasabiae was produced with primers EXPCCF/EXPCCR. ITS-RFLP using the restriction enzyme, Rsa I, produced similar patterns for the Malaysian strains and the P. wasabiae type strain (SCRI488), but differentiated it from P. carotovora subsp. carotovora, P. atrosepticum, P. carotovorum subsp. brasiliensis, and Dickeya chrysanthemi type strains. BLAST analysis of the 16S rRNA DNA sequence (GenBank Accession No. KC445633) showed 99% identity to the 16S rRNA of Pw WPP163. Phylogenetic reconstruction using concatenated DNA sequences of mdh and gapA from P. wasabiae Cc6 (KC484657) and other related taxa (4) clustered Malaysian P. wasabiae strains with P. wasabiae SCRI488, readily distinguishing it from other closely related species of Pectobacterium. Pathogenicity assays were conducted on leaves and stems of four mature cabbage plants for each strain (var. oleifera) by injecting 10 μl of a bacterial suspension (108 CFU/ml) into either stems or leaves, and incubating them in a moist chamber at 80 to 90% relative humidity at 30°C. Water-soaked lesions similar to those observed in the fields and greenhouses were observed 72 h after injection and bacteria with similar characteristics were consistently reisolated. Symptoms were not observed on water-inoculated controls. The pathogenicity test was repeated with similar results. P. wasabiae was previously reported to cause soft rot of horseradish in Japan (3). However, to our knowledge, this is the first report of P. wasabiae infecting cabbage in Malaysia. References: (1) S. H. De Boer and L. J. Ward. Phytopathology 85:854, 1995. (2) V. Duarte et al. J. Appl. Microbiol. 96:535, 2004. (3) M. Goto and K. Matsumoto. Int. J. Syst. Bacteriol. 37:130, 1987. (4) B. Ma et al. Phytopathology 97:1150, 2007.

scholarly journals Occurrence of Dickeya fangzhongdai Causing Soft Rot of Banxia (Pinellia ternata) in China

Plant Disease ◽  
2021 ◽  
Author(s):  
Fanfan Wang ◽  
Tao Tang ◽  
ting Mao ◽  
Jie Guo ◽  
XiaoLiang Guo ◽  
...  
Keyword(s):  
16S Rdna ◽  
Soft Rot ◽  
Negative Control ◽  
Reca Gene ◽  
Bacterial Suspension ◽  
Herbaceous Plant ◽  
Pathogenicity Test ◽  
Sterile Water ◽  
Pinellia Ternata ◽  
Traditional Chinese Herbal Medicine

Banxia [Pinellia ternata (Thunb.) Breit., Araceae] is a perennial herbaceous plant, where the tuber is commonly used in traditional Chinese herbal medicine. In the summer of 2020, an outbreak of soft rot of Banxia was observed in Zhugentan Town (30°50′N, 112°91′E), Qianjiang City, Hubei Province, with about 56% percentage of infected plants. Symptomatic plants initially appeared with small water-soaked spots on leaves that progressed into extensive translucent spots when facing a light source. The bacteria further spread to the stems and tubers. Infected tubers appeared normal, but inner macerated inclusions exuded when touched. The whole plant was macerated and collapsed within a few days. Ten leaves with typical symptoms were obtained from a diseased field, by surface sterilizing in 75% ethanol for 30 s and 0.3% NaClO for 5 min, washing the tissue sections three times in sterile water. Small pieces of tissue (5 × 5 mm) were removed from lesion borders, plated on nutrient ager medium, and cultivated at 37 ℃ for 48 h. Five representative isolates were selected for further identification. Colonies were all smooth and transparent. In addition, these strains were Gram-negative, and had the ability to reduce D-arabinose, melibiose, galactose, raffinose, rhamnose, inositol, and mannitol, but not reduce 5-keto-D-gluconate, L-xylose, amygdalin, and sorbitol. Genomic DNA was extracted from isolate stain ZG5. The 16S rDNA gene, recombinase A (recA) gene, and DNA polymerase III subunits gamma and tau (dnaX) were amplified by PCR with the primers 27f/1492r (Weisburg et al. 1991), recF/recR (Waleron et al. 2002), and dnaXf/dnaXr (Sławiak et al. 2009), respectively. The PCR products were sequenced, then submitted to GenBank (GenBank MW332472, MW349833, MW349834, respectively). BLAST search showed that the sequences of 16S rDNA, recA, and dnaX respectively matched ≥99% with D. fangzhongdai strains DSM 101947 (CP025003), QZH3 (CP031507), and PA1 (CP020872). Pathogenicity tests were performed on 10 healthy, 3-month-old P. ternate plants. Five plants were injected with 20 μl of bacterial suspension (108 CFU/ml) of isolate ZG5, and other plants were injected with sterile water as a negative control. All tested plants were incubated at 28 ℃ and individually covered with a plastic bag. After 24 h, soft rot symptoms all appeared on the pathogen-inoculated leaves, whereas no symptoms on the control leaves. The pathogenicity test was repeated three times and obtained same results. Koch’s postulates were fulfilled by reisolating D. fangzhongdai from inoculated plants. Meanwhile, PCR were performed on the reisolated bacteria as above described, and the pathogen was identified and confirmed as D. fangzhongdai. Here we report that D. fangzhongdai causes soft rot of P. ternata in China. The disease progressed very rapidly, and reduced the yield and quality of tubers. Thus, more research is needed to implement effective strategies to manage this disease.

scholarly journals First Report of Bacterial Soft Rot of Konnyaku Caused by Dickeya dadantii in China

Plant Disease ◽  
2014 ◽  
Vol 98 (5) ◽  
pp. 682-682 ◽  
Author(s):  
J.-F. Wei ◽  
J.-H. Wei
Keyword(s):  
Rural Areas ◽  
Soft Rot ◽  
Positive Control ◽  
Sterile Water ◽  
Dickeya Dadantii ◽  
First Report ◽  
Carotovorum Subsp ◽  
Species Specific ◽  
Important Cash Crop ◽  
Tuber Rot

Konnyaku (Amorphophallus rivieri Durieu) is grown in some rural areas of China as an important cash crop. In 2011, there was a serious outbreak of Konnyaku soft rot in Xuanwei District of Yunnan Province of China. The disease was characterized by partial or complete tuber rot. At its anaphase, the soft rot may move up the stem, causing the caudex to decay and the whole plant to collapse. If the stem is strong or big enough, the soft rot may develop on one side of the stem, leaving the other side healthy for several days. In this case, the stem does not collapse, and etiolation may be observed on the rotten tissue. In serious cases, up to 80% of the plants were infected. The disease is even more serious if Konnyaku is grown continuously in the same field for more than one year. At its worst, the disease can wipe out the whole crop. In 2012 and 2013, we isolated 46 strains of bacteria from 60 Konnyaku tuber samples with soft rot symptoms from Xuanwei District. All strains grew on CVP medium, and produced iridescent, cross-hatched translucent colonies in deep, cuplike depressions or pits. All strains were facultatively anaerobic, gram-negative, straight rod-shaped cells with peritrichous flagella. All strains were catalase-positive, but oxidase-negative. They were able to ferment glucose, reduce nitrate, produce β-galactosidase and H2S, and they utilized L-arabinose, D-galactose, D-glucose, glycerol, D-mannose, D-ribose, and sucrose, but did not produce urease, or acid from adonitol. Pectobacterium carotovorum subsp. carotovorum (syn. Erwina carotovora subsp. carotovora) has been commonly accepted as the causal agent of Konnyaku soft rot in Japan and China (1,3). Our studies also confirmed that P. carotovorum subsp. carotovorum caused Konnyaku soft rot, but the colony morphology and physiological and biochemical characteristics of these bacteria differed greatly from those of P. carotovorum subsp. carotovorum and other pectolytic Pectobacterium species. They grew at 37°C, caused potato soft rot, produced acid from melibiose, citrate, raffinose, and lactose, but did not produce acid from sorbitol and arabitol. The strain also utilized malonate but not keto-methyl glucoside as the sole carbon source. All strains were positive for phosphatase. Forty-one of 46 strains were sensitive to erythromycin. Thirty-seven of 46 strains produced indole. All tests were conducted with P. carotovorum subsp. carotovorum standard strain C2 isolated from Chinese cabbage as a positive control. Healthy Konnyaku tubers were inoculated with suspensions of the strains with a concentration of 108 CFU/ml in sterile water to confirm pathogenicity. After ~48 h, tuber rot symptoms were observed on all inoculated Konnyaku tubers. In comparison, there were no symptoms on tubers inoculated with sterile water. The bacterium was re-isolated from the infected Konnyaku tubers and identified as Dickeya dadantii, in accordance with Koch's postulates. All strains were confirmed by using the species-specific primers ERWFOR/CHRREV (2), which amplified a 450-bp DNA fragment by PCR assay. To our knowledge, this is the first report of Konnyaku soft rot caused by D. dadantii in China. References: (1) N. Hayashi. Gunma J. Agric. Res. A (Genera1) 5:25, 1988. (2) E. J. Smid et al. Plant Pathol. 44:1058, 1995. (3) J. Y. Tang et al. J. Yunnan Agric. Univ. 16:185, 2001.

scholarly journals First Report of Pectobacterium carotovorum subsp. brasiliense Causing Soft Rot on Squash and Watermelon in Serbia

Plant Disease ◽  
2019 ◽  
Vol 103 (10) ◽  
pp. 2667-2667 ◽  
Author(s):  
N. Zlatković ◽  
A. Prokić ◽  
K. Gašić ◽  
N. Kuzmanović ◽  
M. Ivanović ◽  
...  
Keyword(s):  
Soft Rot ◽  
Pectobacterium Carotovorum ◽  
First Report ◽  
Carotovorum Subsp

scholarly journals First Report of Dickeya solani Causing Soft Rot in Imported Bulbs of Hyacinthus orientalis in China

Plant Disease ◽  
2015 ◽  
Vol 99 (1) ◽  
pp. 155-155 ◽  
Author(s):  
X. F. Chen ◽  
H. L. Zhang ◽  
J. Chen
Keyword(s):  
16S Rrna ◽  
The Netherlands ◽  
Bacterial Pathogen ◽  
Soft Rot ◽  
Potato Production ◽  
Sterile Water ◽  
First Report ◽  
Hyacinthus Orientalis ◽  
Dickeya Solani ◽  
Negative Controls

A bacterial pathogen, Dickeya solani, emerged as a major threat to potato (Solanum tuberosum) production in Europe in 2004 and has spread to many potato-growing regions via international trade. In December 2013, soft rot symptoms were observed in hyacinth (Hyacinthus orientalis) bulbs imported from the Netherlands into China at Ningbo Port. Diseased bulbs gave off an offensive odor. The base and internal parts of diseased bulbs rotted, and the margins of diseased tissues showed brown discoloration. Isolation on nutrient agar glucose (NAG) medium resulted in dominating colonies of characteristic “fried egg” morphology (1). One colony was chosen for further investigation and tentatively named “isolate 6165-3.” Under microscopic visualization after gram stain, the cells of isolate 6165-3 were gram-negative, motile, and rod shaped. The isolate was then identified as a member of genus Dickeya using the Biolog GN microplate. The 16S rRNA, recA, and dnaX sequences of isolate 6165-3 were subsequently determined and deposited in GenBank with accession numbers KM405240, KM405241, and KM405242, sharing 99% (16S rRNA), 100% (recA), and 100% (dnaX) nucleotide identity with those of known D. solani isolates, respectively. By this means, the isolate 6165-3 was identified as D. solani (1,2). To confirm the pathogenicity of the isolate, four plants each of 30-day-old hyacinth, 14-day-old potato, and 60-day-old moth orchid (Phalaenopsis amabilis) were inoculated with suspensions of the isolate with a concentration of 108 CFU/ml in sterile water by stabbing. Plants were incubated in a climate chamber at 28°C during the day and 24°C during the night with a relative humidity of 93% and a photoperiod of 12/12 h. Plants inoculated with sterile water were included as negative controls. After 2 or 3 days, typical symptoms such as water-soaked lesions and soft rot developed around the inoculation point, while the negative controls remained symptomless. Koch's postulates were fulfilled by re-isolating bacteria from lesions, which had identical sequence and morphology characters with the inoculated isolate. This is the first report of intercepted D. solani on hyacinth bulbs imported from the Netherlands into China, indicating that D. solani can spread via hyacinth. Further spread of the pathogen into potato production might lead to immeasurable economic consequences for China. References: (1) P. F. Sarris et al. New Dis. Rep. 24:21, 2011. (2) J. M. van der Wolf et al. Int. J. Syst. Evol. Microbiol. 64:768, 2014.

scholarly journals First Report of Fusarium pernambucanum Causing Fruit Rot of Muskmelon in China

Plant Disease ◽  
2021 ◽  
Author(s):  
Xianping Zhang ◽  
Jiwen Xia ◽  
Jiakui Liu ◽  
Dan Zhao ◽  
Lingguang Kong ◽  
...  
Keyword(s):  
Phylogenetic Analyses ◽  
Apical Cell ◽  
Morphological Characteristics ◽  
Fruit Rot ◽  
Likelihood Method ◽  
Correct Identification ◽  
Pathogenicity Test ◽  
First Report ◽  
The Core ◽  
Representative Isolate

Muskmelon (Cucumis melo L.) is one of the most widely cultivated and economically important fruit crops in the world. However, many pathogens can cause decay of muskmelons; among them, Fusarium spp. is the most important pathogen, affecting fruit yield and quality (Wang et al. 2011). In May 2017, fruit rot symptoms were observed on ripening muskmelons (cv. Jipin Zaoxue) in several fields in Liaocheng of Shandong Province, China. Symptoms appeared as brown, water-soaked lesions, irregularly circular in shape, with the lesion size ranging from a small spot (1 to 2 cm) to the decay of the entire fruit. The core and the surface of the infected fruit were covered with white to rose-reddish mycelium. Two infected muskmelons were collected from each of two fields, 10 km apart. Tissues from the inside of the infected fruit were surface disinfected with 75% ethanol for 30 s, and cultured on potato dextrose agar (PDA) at 25 °C in the dark for 5 days. Four purified cultures were obtained using the single spore method. On carnation leaf agar (CLA), macroconidia had a pronounced dorsiventral curvature, falcate, 3 to 5 septa, with tapered apical cell, and foot-shaped basal cell, measuring 19 to 36 × 4 to 6 μm. Chlamydospores were abundant, 5.5–7.5 μm wide, and 5.5–10.5 μm long, ellipsoidal or subglobose. No microconidia were observed. These morphological characteristics were consistent with the descriptions of F. pernambucanum (Santos et al. 2019). Because these isolates had similar morphology, one representative isolate was selected for multilocus phylogenetic analyses. DNA was extracted from the representative isolate using the CTAB method. The nucleotide sequences of the internal transcribed spacers (ITS) (White et al. 1990), translation elongation factor 1-α gene (TEF1), RNA polymerase II second largest subunit gene (RPB2), calmodulin (CAM) (Xia et al. 2019) were amplified using specific primers, sequenced, and deposited in GenBank (MN822926, MN856619, MN856620, and MN865126). Based on the combined dataset of ITS, TEF1, RPB2, CAM, alignments were made using MAFFT v. 7, and phylogenetic analyses were processed in MEGA v. 7.0 using the maximum likelihood method. The studied isolate (XP1) clustered together with F. pernambucanum reference strain URM 7559 (99% bootstrap). To perform pathogenicity test, 10 μl of spore suspensions (1 × 106 conidia/ml) were injected into each muskmelon fruit using a syringe, and the control fruit was inoculated with 10 μl of sterile distilled water. There were ten replicated fruits for each treatment. The test was repeated three times. After 7 days at 25 °C, the interior of the inoculated muskmelons begun to rot, and the rot lesion was expanded from the core towards the surface of the fruit, then white mycelium produced on the surface. The same fungus was re-isolated from the infected tissues and confirmed to fulfill the Koch’s postulates. No symptoms were observed on the control muskmelons. To our knowledge, this is the first report of F. pernambucanum causing of fruit rot of muskmelon in China. Considering the economic value of the muskmelon crop, correct identification can help farmers select appropriate field management measures for control of this disease.

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