scholarly journals First Report of Crown and Root Rot Caused by Pythium myriotylum on Hemp (Cannabis sativa) in Arizona

Plant Disease ◽  
2021 ◽  
Author(s):  
Jiahuai Hu
Keyword(s):  
Root Rot ◽  
Cannabis Sativa ◽  
Morphological Characteristics ◽  
Crown Rot ◽  
Pathogenicity Test ◽  
Light Cycle ◽  
Pythium Myriotylum ◽  
First Report ◽  
Leaf Chlorosis ◽  
Query Coverage

During August and September 2020, symptoms of leaf chlorosis, stunting, and wilting were observed on indoor hemp plants (Cannabis sativa L. cv. ‘Wedding Cake’) in a commercial indoor facility located in Coolidge, Arizona. Plants were grown in soilless coconut coir growing medium (Worm Factory COIR250G10), watered with 1.5 to 2.1 liters every 24 h through drip irrigation, and supplemented with 18 h of lighting. About 35% of plants displayed symptoms as described above and many symptomatic plants collapsed. To identify the causal agent, crown and root tissues from four symptomatic plants were harvested and rinsed with tap water. Tissue fragments (approx. 2 to 4 mm in size) were excised from the margins of the stem and root lesions, surface sterilized in 0.6% sodium hypochlorite for 1 min, rinsed well in sterile distilled water, blotted dry, and plated on potato dextrose agar (PDA) and on oomycete-selective clarified V8 media containing pimaricin, ampicillin, rifampicin, and pentachloronitrobenzene (PARP). Plates were incubated at room temperature (21-24 oC). Five isolates resembling Pythium were transferred after 3 days and maintained on clarified V8 media. Morphological characteristics were observed on grass blade cultures (Waterhouse 1967). Grass blades were placed on CV8 inoculated with the isolate. After a 1-day incubation at 25°C, the colonized blades were transferred to 8 ml of soil water extract in a Petri dish. Ten sporangia and oogonia were selected randomly and their diameters were measured under the microscope. Sporangia were mostly filamentous, undifferentiated or inflated lobulate, ranging from 7 to 17 µm in diameter. Knob-like appressoria were observed on branching clusters. Bulbous-like antheridia were formed on branched stalk with 1-8 antheridia per oogonium. Globose oogonia were terminal or intercalary and ranged from 21 to 33 µm in diameter. Globose oospores were mostly aplerotic and ranged from 15 to 21 μm in diameter. Based on these morphological characteristics, isolates were tentatively identified as Pythium myriotylum (Watanabe, 2002). Genomic DNA was extracted from mycelial mats of two isolates using DNeasy Plant Pro Kit (Qiagen Inc., Valencia, CA) according to the manufacturer’s instructions. The internal transcribed spacer (ITS) region of rDNA was amplified with primers ITS1/ITS4 and two identical nucleotide sequences were obtained and deposited under accession number MW380925. A BLASTn search revealed ≥ 98% query coverage and 100% match with sequences HQ237488.1, KY019264.1, and KM434129, which were isolates of P. myriotylum from palm, tobacco, and ginger, respectively. To fulfill Koch’s postulates, pathogenicity tests were conducted with 2 isolates using plants of ‘Wedding Cake’ grown in 12 1.9-liter pots filled with a steam-disinfested potting mix (Sungro Professional Growing Mix). Pots were placed in a plastic container and watered to flooding three times a week. Plants were maintained in a greenhouse with 18 h/10 h day/night supplemental light cycle (15-28 oC). Plants were fertilized weekly with Peters Professional fertilizer at 1mg/ml. Four plants were inoculated with each isolate at three weeks after seed sowing by placing two 5-mm mycelial plugs from active growing 4 days-old cultures on PDA media adjacent to the main root mass at an approximately 3 cm depth. Four plants were inoculated with blank PDA plugs as controls. Symptoms of leaf chlorosis, crown rot and wilting were observed after four weeks while control plants remained symptomless. P. myriotylum was re-isolated from necrotic roots of inoculated plants after surface-sterilization, but not from control plants. The pathogenicity test was repeated once. While P. myriotylum often occurs in warmer regions and has a wide host range of >100 host plant species including numerous economically important crops (Wang et al., 2003), there are only two reports of this pathogen on indoor hemp plants in a greenhouse in Connecticut (McGehee et al., 2019) and in Canada (Punja et al., 2019). This is the first report of P. myriotylum causing root and crown rot of indoor hemp in Arizona. A more careful water management in soilless growth medium to reduce periods of saturation would minimize the risk of Pythium root rot in indoor hemp production.

scholarly journals First Report of Rhizoctonia solani AG 4 on Lamb's Lettuce in Italy

Plant Disease ◽  
2006 ◽  
Vol 90 (8) ◽  
pp. 1109-1109 ◽  
Author(s):  
A. Garibaldi ◽  
G. Gilardi ◽  
M. L. Gullino
Keyword(s):  
Rhizoctonia Solani ◽  
Morphological Characteristics ◽  
Northern Italy ◽  
Crown Rot ◽  
Pathogenicity Test ◽  
First Report ◽  
Pathogenicity Tests ◽  
Hyphal Diameter ◽  
Wheat Kernels ◽  
Extensive Necrosis

Lamb's lettuce or corn salad (Valerianella olitoria) is increasingly grown in Italy and used primarily in the preparation of mixed processed salad. In the fall of 2005, plants of lamb's lettuce, cv Trophy, exhibiting a basal rot were observed in some commercial greenhouses near Bergamo in northern Italy. The crown of diseased plants showed extensive necrosis, progressing to the basal leaves, with plants eventually dying. The first symptoms, consisting of water-soaked zonate lesions on basal leaves, were observed on 30-day-old plants during the month of October when temperatures ranged between 15 and 22°C. Disease was uniformly distributed in the greenhouses, progressed rapidly in circles, and 50% of the plants were affected. Diseased tissue was disinfested for 1 min in 1% NaOCl and plated on potato dextrose agar amended with 100 μg/liter of streptomycin sulfate. A fungus with the morphological characteristics of Rhizoctonia solani was consistently and readily isolated and maintained in pure culture after single-hyphal tipping (3). The five isolates of R. solani, obtained from affected plants successfully anastomosed with tester isolate AG 4, no. RT 31, received from R. Nicoletti of the Istituto Sperimentale per il Tabacco, Scafati, Italy (2). The hyphal diameter at the point of anastomosis was reduced, and cell death of adjacent cells occurred (1). Pairings were also made with AG 1, 2, 3, 5, 7, and 11 with no anastomoses observed between the five isolates and testers. For pathogenicity tests, the inoculum of R. solani (no. Rh. Vale 1) was grown on autoclaved wheat kernels at 25°C for 10 days. Plants of cv. Trophy were grown in 10-liter containers (20 × 50 cm, 15 plants per container) on a steam disinfested substrate (equal volume of peat and sand). Inoculations were made on 20-day-old plants by placing 2 g of infected wheat kernels at each corner of the container with 3 cm as the distance to the nearest plant. Plants inoculated with clean wheat kernels served as controls. Three replicates (containers) were used. Plants were maintained at 25°C in a growth chamber programmed for 12 h of irradiation at a relative humidity of 80%. The first symptoms, consisting of water-soaked lesions on the basal leaves, developed 5 days after inoculation with crown rot and plant kill in 2 weeks. Control plants remained healthy. R. solani was consistently reisolated from infected plants. The pathogenicity test was carried out twice with similar results. This is, to our knowledge, the first report of R. solani on lamb's lettuce in Italy as well as worldwide. The isolates were deposited at the AGROINNOVA fungal collection. The disease continues to spread in other greenhouses in northern Italy. References: (1) D. Carling. Rhizoctonia Species: Pages 37–47 in: Taxonomy, Molecular Biology, Ecology, Pathology and Disease Control. B. Sneh et al., eds. Kluwer Academic Publishers, the Netherlands, 1996. (2) J. Parmeter et al. Phytopathology, 59:1270, 1969. (3) B. Sneh et al. Identification of Rhizoctonia Species. The American Phytopathological Society, St. Paul, MN, 1996.

scholarly journals First Report of Root Rot and Wilt Caused by Pythium myriotylum on Hemp (Cannabis sativa) in the United States

Plant Disease ◽  
2019 ◽  
Vol 103 (12) ◽  
pp. 3288-3288 ◽  
Author(s):  
C. S. McGehee ◽  
P. Apicella ◽  
R. Raudales ◽  
G. Berkowitz ◽  
Y. Ma ◽  
...  
Keyword(s):  
United States ◽  
Root Rot ◽  
Cannabis Sativa ◽  
The United States ◽  
Pythium Myriotylum ◽  
First Report

scholarly journals Morphological and Molecular Characteristics of Fungal Species Associated with Crown Rot of Strawberry in South Korea

2021 ◽  
Author(s):  
Oliul Hassan ◽  
Taehyun Chang
Keyword(s):  
South Korea ◽  
Root Rot ◽  
Species Complex ◽  
Sequence Data ◽  
Morphological Characteristics ◽  
Fungal Species ◽  
Crown Rot ◽  
Molecular Characteristics ◽  
Pathogenicity Test ◽  
Crown And Root Rot

Abstract Crown and root rot is the most important and destructive strawberry diseases in Korea as it causessubstantial economic loss. In August 2020, a severe outbreak of crown and root rot on strawberries (Fragaria×ananassa Duch.) was observed in the greenhouse at Sangju, South Korea. Infected plantlets displayed browning rot within the crown and root, stunted growth, and poor rooting. Thirty fungal isolates were procured from the affected plantlet. Isolates were identified based on morphological characteristics and pathogenicity test as well as sequence data obtained from internal transcribed spacer, large subunit ribosomal ribonucleic acid, translation elongation factor,and RNA polymerase Ⅱ-second largest subunit. Results showed that thecrown and root rot of strawberry in Korea was caused by three distinct fungal species:Fusarium oxysporum species complex, F. solani species complex, andPlectosphaerella cucumerina. To the best of our knowledge,F. solani species complex andP. cucumerinaare reported for the first time as the causal agents of the crown and root rot of strawberryin South Korea.Pathogenicity tests confirmed that these isolates are pathogenic to strawberry.Understanding the composition and biology of the pathogen population will be helpful toprovide effectivecontrol strategies for the disease.

scholarly journals First Report of Rhizoctonia solani Causing a Disease of Sunflower in India

Plant Disease ◽  
2010 ◽  
Vol 94 (4) ◽  
pp. 488-488 ◽  
Author(s):  
K. Srinivasan ◽  
S. Visalakchi
Keyword(s):  
Rhizoctonia Solani ◽  
Root Rot ◽  
Crown Rot ◽  
Pathogenicity Test ◽  
American Phytopathological Society ◽  
First Report ◽  
Leaf Yellowing ◽  
Crown Tissue ◽  
Symptomatic Tissue ◽  
White Mycelium

During the spring of 2009, symptoms including leaf yellowing and wilting, root rot, and death of plants were noted in sunflower (Helianthus annuus L.) crops in Dharmapuri District, Tamilnadu, India. In some fields, approximately 30% of the plants were affected. The disease began when plants were approximately 10 weeks old and occurred on scattered or adjacent plants. The presence of white mycelium was observed on necrotic crowns. Symptomatic tissue was surface disinfested in 70% alcohol for 30 s and 0.5% sodium hypochlorite for 1 min and plated onto potato dextrose agar (PDA) (1). One isolate (coded SV001) had near right-angle branching with basal constriction and adjacent septa and sclerotia typical of Rhizoctonia spp. (2). Cream-colored colonies produced irregular, light brown sclerotia that were 3.0 to 7.3 mm (average 3.8 mm) in diameter. Hyphae were 6.8 to 7.0 μm (average 6.9 μm) wide and multinucleate (8 to 15 nuclei per cell). On the basis of hyphal anastomosis with several known AG testers, the fungus was characterized as Rhizoctonia solani Kühn AG-IV (3). One culture was deposited at the Madras University Botany Laboratory, Center for Advanced Studies in Botany, University of Madras, Chennai, India. In a pathogenicity test, R. solani SV001 was grown on PDA for 5 days at 24°C in the dark. Five-millimeter-diameter disks were placed at the base of sunflower plants (cv. Mordan). Four sunflower plants in each of three pots were inoculated; noninoculated plants served as controls. Plants were placed in a glasshouse maintained at 25 to 27°C. Inoculated plants developed yellow foliage and crown rot and root rot symptoms after 7 to 12 days and died in 17 to 20 days. No symptoms were observed on noninoculated plants. The pathogen was reisolated from fragments of necrotic crown tissue of inoculated plants. To our knowledge, this is the first report of R. solani AG-IV causing a disease of sunflower plants in India. References: (1). R. C. Fenille et al. Plant Pathol. 54:325, 2005. (2). J. R. Parmeter et al. Phytopathology 59:1270, 1969. (3) B. Sneh et al. Identification of Rhizoctonia Species. The American Phytopathological Society, St Paul, MN, 1991.

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

Plant Disease ◽  
2021 ◽  
Author(s):  
Sixto Velarde Felix ◽  
Victor Valenzuela ◽  
Pedro Ortega ◽  
Gustavo Fierros ◽  
Pedro Rojas ◽  
...  
Keyword(s):  
Fusarium Solani ◽  
Root Rot ◽  
Species Complex ◽  
Elongation Factor ◽  
Morphological Characteristics ◽  
Aerial Mycelium ◽  
Pathogenicity Test ◽  
Conidial Suspension ◽  
Single Spore ◽  
First Report

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

scholarly journals First Report of Crown and Root Rot Caused by Pythium aphanidermatum on Industrial Hemp (Cannabis sativa) in Arizona

Plant Disease ◽  
2021 ◽  
Author(s):  
Jiahuai Hu ◽  
Robert Masson
Keyword(s):  
Root Rot ◽  
Cannabis Sativa ◽  
Tap Water ◽  
Root Bark ◽  
Distilled Water ◽  
Light Cycle ◽  
Plastic Mulch ◽  
Query Coverage ◽  
Crown And Root Rot ◽  
Industrial Hemp

During July and August 2020, symptoms of leaf yellowing and browning, sudden wilting, and death were observed on industrial hemp plants (Cannabis sativa L.) in several drip-irrigated fields in Yuma and Graham county, Arizona. About 85% of plants showed severe crown and root rot symptoms. A high percentage of affected plants collapsed under intensive heat stress. Shriveled stem tissue with necrotic lesions can often be seen at the base of the plant, extending upwards more than 5 cm. Internal tissue of main stem and branches was darkened or pinkish brown. Outer cortex of root bark was often completely rotten, exposing the white core. Cottony aerial mycelium was visible on the surface of stalk of some of the infected plants in two fields in Yuma. To identify the causal agent, a total of twenty symptomatic plants were collected from several fields across the state. Crown and root tissues from affected plants were harvested and rinsed in tap water to remove soils. Approximately 2 to 4 mm tissue fragments were excised from the margins of the affected stem and root lesions, surface sterilized in 0.6% sodium hypochlorite for 1 min, rinsed copiously in sterile distilled water, blotted dry, and plated on potato dextrose agar (PDA), and on oomycete-selective clarified V8 medium containing pimaricin, ampicillin, rifampicin, and pentachloronitrobenzene (PARP). Plates were incubated at room temperature for 2 days. Sixteen isolates were recovered and their mycelial colonies resembled the morphology of Pythium. Based on the culture morphology on V8 medium, all isolates were tentatively identified as P. aphanidermatum with fast-growing, aseptate hyphae ranging from 3 to 7 μm in width, globose oogonia ranging from 25 to 31 μm in diameter, barrel-shaped antheridia, globose oospores ranging from 15 to 21 μm in diameter (10 measurements) (Watanabe, 2002). Genomic DNA was extracted from mycelial mats of three isolates using DNeasy Plant Pro Kit (Qiagen Inc., Valencia, CA) according to the manufacturer’s instructions. The internal transcribed spacer (ITS) region of rDNA was amplified with primers ITS1/ITS4 and three nucleotide sequences were obtained. All three sequences were identical and deposited under accession number MW380253 in GenBank. A BLASTn search revealed that MW380253 had a 100% query coverage and 100% match with sequences MK611609.1, KJ162355.1, and AY598622.2, obtained from isolates of P. aphanidermatum. To fulfill Koch’s postulates, pathogenicity tests were conducted with 2 isolates using 12 seeds of a hemp line 14 sown in 12 1.9-liter pots filled with a steam-disinfested potting mix. Pots were placed in a plastic container and watered three times a week by flooding, to create waterlogged conditions. Plants were maintained in a greenhouse supplemented with artificial lighting of 14 h/10 h day/night light cycle. Plants were fertilized weekly with a 20-20-20 fertilizer at 1mg/ml. Three weeks after sowing, four plants were inoculated with each isolate by drenching each plant with 200 ml of a 1×105 zoospore/ml suspension. Four plants, serving as control, received each 200 ml of distilled water. Symptoms of leaf chlorosis, crown and root rot, and wilting were observed 3 weeks afterwards, while control plants remained asymptomatic. P. aphanidermatum were re-isolated from necrotic roots of inoculated plants, but not from control plants. P. aphanidermatum was previously detected on industrial hemp in a research plot in Indiana (Beckerman et al., 2017) and is also known to affect other crops in Arizona during the summer months as well (Olsen & Nischwitz, 2011). This report is the first publication documenting P. aphanidermatum on field grown hemp in Arizona. Industrial hemp (Cannabis sativa) is an emerging crop in Arizona. The first plantings of hemp were in June of 2019, where 5,430 acres of hemp was planted in thirteen counties in Arizona before the end of the year. The Arizona Department of Agriculture Industrial Hemp Program, 2019 Year End Report confirms that nearly one-quarter of all hemp planted in 2019 did not receive a final state inspection due to crop loss. This disease is a potential constraint to hemp production in hot, arid climates, where copious water is used in combination with plastic mulch and/or drainage is poor.

scholarly journals First report of Pythium aphanidermatum causing crown and root rot on industrial hemp in China

Plant Disease ◽  
2021 ◽  
Author(s):  
Jia Chen ◽  
Zhimin Li ◽  
Cheng Yi ◽  
Chunsheng Gao ◽  
Litao Guo ◽  
...  
Keyword(s):  
Root Rot ◽  
Cannabis Sativa ◽  
Eastern China ◽  
Pythium Aphanidermatum ◽  
Its Sequencing ◽  
Disease Symptoms ◽  
First Report ◽  
Query Coverage ◽  
Crown And Root Rot ◽  
Industrial Hemp

In July 2020, symptoms of crown and root rot were observed on about 10% of 4-month-old plants of industrial hemp Cannabis sativa cultivar Yunma-1 in Weifang City, Shandong Province in eastern China (Fig 1). During this month, the local temperature ranged from 19-32°C, and the total precipitation was 148mm. The disease symptoms included leaf chlorosis, crown and root rot, stunted growth, and wilting (Figs. 1 and 2). The diseased stem and root tissues were collected and cut into fragments of 0.5cm each. The fragments were surface-sterilized by dipping into 1% NaClO for 1 min, rinsed in sterile water and plated on potato dextrose agar (PDA) and on oomycetes-selective medium PARP (Jeffers and Martin 1986). The plates were incubated at 25°C in the dark for 3 days and 18 total single-hyphal purified isolates were obtained for further analyses with 8 from PDA and 10 from PARP. The colonies of all 18 isolates were white, had abundant aerial hyphae, and were cottony in appearance, resembling Pythium spp (Watanabe 2002). The grass-leaf method (Van Der Plaats-Niterink 1981) induced their sexual reproduction. The size and shape of hyphae, oogonia, antheridia, and oospores were all consistent with those of Pythium aphanidermatum (Fig 3). DNA was extracted from three isolates and their internal transcribed spacer (ITS) regions of rDNA were amplified and sequenced using the primers ITS1/ITS4 (White et al. 1990). The ITS sequences of all three isolates were identical to each other (GenBank accession OK091124.1) and showed a 100% query coverage and 99.88% nucleotide sequence identity with that of type strain of P. aphanidermatum (GenBank accession AY598622.2). Pathogenicity tests were performed with three isolates on hemp cultivar B1. Sterile substrates were prepared in 2L-pots containing peat soil and vermiculite in a 2:1 ratio, with test hemp plants grown from rooted stem cuttings. Plants were kept in a greenhouse at 22 to 27°C under 16 h photoperiod, watered every two days (about 200ml each time) and supplied commercial nutrient solution once a week. A month after transplanting to pots, a wound of 1 mm deep and 10 mm long (made by a sterilized needle) on the surface of the root crown area of the main stem was inoculated with an 8-mm-diameter agar disk of mycelia grown on PDA for 4 days. Six plants were tested for each isolate and three plants were inoculated with sterile agar medium without mycelia as negative controls. The experiment was repeated twice. After one month, plants inoculated with P. aphanidermatum isolates showed the same disease symptoms as observed on field plants while all negative control plants remained disease-free. P. aphanidermatum was reisolated from the diseased tissue and confirmed to be identical to those inoculated based on ITS sequencing and colony morphology. To our knowledge, this is the first report of P. aphanidermatum causing crown and root rot on hemp in China. With an estimated 66,700 hectares hemp cultivation in China producing over US$1 billion worth of hemp fiber (McGrath 2020), this pathogen represents a serious threat to the hemp industry. This pathogen has been reported on hemp in the US and Canada (Beckerman et al. 2017; Punja et al. 2018). The origin of P. aphanidermatum on hemp in China and its relationship to those in North America remain to be examined.

scholarly journals First Report of Fusarium Root Rot of Tobacco Caused by Fusarium sinensis in Henan Province China

Plant Disease ◽  
2021 ◽  
Author(s):  
Rui Qiu ◽  
Qi Li ◽  
Juan Li ◽  
Ningyu Dong ◽  
Shujun Li ◽  
...  
Keyword(s):  
Root Rot ◽  
Morphological Characteristics ◽  
Henan Province ◽  
Crown Rot ◽  
Conidial Suspension ◽  
Tobacco Plants ◽  
First Report ◽  
Agricultural Sciences ◽  
Tobacco Seedlings ◽  
Β Tubulin

Tobacco (Nicotiana tabacum L.) is an economically important crop in China, with an estimated production of 2.2 million tons every year. In June 2018, tobacco plants within the municipality of Sanmenxia (Henan, China) showed symptoms of wilting with leaf yellowing and stunting. Diseased plants exhibited severe necrosis that advanced through the main root (Figure 1 A). The symptoms were observed in nineteen surveyed tobacco fields, 60 ha in total, and approximately 25% of the plants were symptomatic. The disease resulted in a severe loss in tobacco leaf production. Five symptomatic tobacco plants were sampled. Diseased tissues from roots were surface sterilized in 75% ethanol and placed on potato dextrose agar (PDA) medium. Eighteen of the 25 diseased tissues had cultures growing from them, and all the cultures were white colonies with abundant aerial mycelium produced scarlet pigmentation on PDA. One pure culture was obtained by single-spore culturing (SL1). A 10-day-old culture grown on CLA (carnation leaf agar) produced macroconidia that were falcate, straight or slightly curved, 3-septate, 25-35×3.5-4.5 μm (average 26.8×3.7 μm) (n=50). Two types of microconidia (napiform and fusiform) were formed on CLA that were hyaline, with one to two cells. Napiform conidia were 4.5-9.3×3.8-5.9 (average 7.3×5.0 μm) (n=50); fusiform conidia were 6.9-15.8×1.8-3.1 (average 9.9×2.5 μm). Spherical chlamydospores (7-12.5 μm) (n=50) were terminal or intercalary and produced in clumps or in chains (Figure1 B-D). Morphological characteristics of the isolate were similar to the features of Fusarium sinensis previously described by Zhao and Lu (2008). Molecular identification was performed using partial sequences of EF1-α gene (primers EF1/EF2, O’Donnell et al. 1998). Maximum parsimony and maximum likelihood-based methods were fitted using MEGA 7 (Moreira et al. 2019，Figure 2). The isolate was also sequenced for β-tubulin (primers T1/Bt-2b, O’Donnell & Cigelnik 1997)，ribosomal RNA gene (LSU, LROR/LR5 primers, Vu et al. 2019) and rDNA-ITS (ITS 1/ ITS 4 primers, White et al. 1990). Sequences were deposited in GenBank under accession numbers MT947797 (EF1-α), MW484999 (β-tubulin), MW486649 (LSU) and MT907471 (ITS). The obtained EF1-α sequence was 98.10% identity with those of F. sinensis (MG670388.1) in the GenBank database, whereas the β-tubulin, LSU and ITS sequences showed 100% identities to the corresponding DNA sequences in F. sinensis (GenBank Acc. Nos. KX880370.1, NG_067454.1 and MH863232.1, respectively). Morphological and molecular results confirmed this species as F. sinensis (Zhao and Lu 2008). Pathogenicity tests were performed on tobacco seedlings grown on an autoclaved matrix (YC/T310-2009). Healthy 6-leaf stage tobacco seedlings were inoculated by pouring a 20 mL conidial suspension (1×106 conidia/mL-1) around the stem base of each plant, 30 plant were inoculated. Thirty control seedlings received sterilized water. All treatments were maintained for 30 days under greenhouse conditions with a 12-h light/dark photoperiod at 25±0.5℃ and 70% relative humidity. The assay was conducted three times. Root rot and foliage chlorosis similar to the ones observed on infected plants in the field were observed on the inoculated tobacco seedlings, whereas the control seedlings remained asymptomatic after 30 days (Figure1 E). The pathogen isolated from the inoculated plant exhibited morphological characteristics identical to F. sinensis and was identified by a partial EF1-α gene sequence. This disease has previously been reported as the causal agent of root and crown rot of wheat in China (Zhao and Lu 2008; Xu et al. 2018). To our knowledge, this is the first report of F. sinensis causing root rot on tobacco in China. Funding: Funding was provided by the Science and Technology Project of Henan Provincial Tobacco Company (2020410000270012), Independent Innovation Project of Hennan Academy of Agricultural Sciences (2020ZC18) and Research and Development project of Henan Academy of Agricultural Sciences (2020CY010). References: Moreira, G.M., et al. 2019 Plant Dis. O’Donnell, K., et al. 1998. Proc. Natl. Acad. Sci. USA 95:2011. O'Donnell, K., et al. 2008. J. Clin. Microbiol. 46:2477. Xu, F., et al. 2018. Front Microbiol. 9:1054. Zhao, Z.H., and Lu, G. Z., 2008. Mycologia, 100:746. The author(s) declare no conflict of interest. Keywords: tobacco root rot, Henan Province, Fusarium sinensis

scholarly journals First Report of Root Rot Incited by Thielaviopsis basicola on Lamb's Lettuce (Valerianella olitoria) in Europe

Plant Disease ◽  
2005 ◽  
Vol 89 (2) ◽  
pp. 205-205 ◽  
Author(s):  
A. Garibaldi ◽  
G. Gilardi ◽  
M. L. Gullino
Keyword(s):  
Root Rot ◽  
Morphological Characteristics ◽  
The United States ◽  
Northern Italy ◽  
Potato Dextrose Agar ◽  
Pathogenicity Test ◽  
Thielaviopsis Basicola ◽  
First Report ◽  
Severe Stunting ◽  
Extensive Necrosis

Lamb's lettuce (Valerianella olitoria) is increasingly grown in Italy and used in the preparation of processed salad. In the fall of 2003, plants of lamb's lettuce cvs. Trophy and Palmares showing symptoms of severe stunting were observed in several commercial plastic greenhouses near Bergamo in northern Italy. The distribution of the disease was generally uniform in the greenhouses and 10 to 30% of the plants were affected. The first symptoms, consisting of reduced growth of the plants and extensive chlorosis, developed in October at temperatures ranging between 10 and 20°C on 30-day-old plants. The roots of diseased plants showed extensive necrosis that extended to the crown of the plants. The diseased tissue was disinfested for 1 min in 1% NaOCl and plated on potato dextrose agar amended with 100 µg/l streptomycin sulfate. A fungus with the morphological characteristics of Thielaviopsis basicola was consistently and readily isolated from symptomatic tissues (1). Catenulate, cylindrical, hyaline endoconidia and catenulate, subrectangular, thick-walled chlamydospores (aleuriospores) were observed. Ten-day-old plants of cvs. Trophy and Palmares were artificially inoculated by dipping three isolates of T. basicola obtained from infected plants for 15 min in a spore suspension (1 × 106 CFU/ml). Noninoculated plants served as control treatments. Each treatment consisted of 30 plants. Plants were maintained at 20°C in a growth chamber, with 12 h of light/day. Symptoms developed 25 days after the artificial inoculation on both cultivars, and T. basicola was consistently reisolated from diseased plants. The noninoculated plants remained healthy. The pathogenicity test was carried out twice. To our knowledge, this is the first report of T. basicola on lamb's lettuce in Italy as well as in the world. The same disease was described on corn salad (Valerianella locusta) in the United States (2). References: (1) D. E. Mathre and A.V. Ravenscroft. Phytopathology 56:337, 1966. (2) M. E. Stanghellini et al. Plant Dis. 74:81, 1990.

scholarly journals First Report of white root rot of hemp (Cannabis sativa L.) caused by Dematophora necatrix in Campania region (Southern Italy)

Plant Disease ◽  
2021 ◽  
Author(s):  
Roberto Sorrentino ◽  
Gian Maria Baldi ◽  
Valerio Battaglia ◽  
Francesco Raimo ◽  
Giulio Piccirillo ◽  
...  
Keyword(s):  
Root Rot ◽  
Cannabis Sativa ◽  
Elongation Factor ◽  
Morphological Characteristics ◽  
New Host ◽  
Campania Region ◽  
First Report ◽  
History Of ◽  
Industrial Hemp ◽  
Dematophora Necatrix

Industrial hemp (Cannabis sativa L.) was cultivated in Italy until the end of the Second World War. Since then, it has been abandoned and substituted with other crops mainly due to legal restrictions and public concerns. Public legislation passed in 2016, has allowed for the production of hemp seeds, flowers and fibers (law n. 242/2016). During a 2019 survey on hemp sanitary status in the province of Naples (40°57'6"12 N, 14°22'37"56 E), hemp ‘Kompolty’ with symptoms of root rot were observed at a private farm and collected for further analysis at the phytosanitary laboratory of CREA in Caserta. Death generally occurred within 2-3 weeks after the appearance of the first symptoms, occurring on ca. 10% of plants, consisting of yellowing, canopy wilt and signs of roots covered with white mycelium and fan-like mycelium under the bark. The causal agent, was isolated from small root segments, excised from symptomatic plants, the surface was disinfected with 2% sodium hypochlorite, placed on potato dextrose agar (PDA) amended with streptomycin sulphate (100mg/L) and incubated in the dark at 25°C for 5 days. Small pieces (2-3 mm) at the edge of the resulting colonies were sub-cultured onto PDA and incubated at 25°C in the dark for one week. The mycelia from 15 isolates showed pear-shaped swellings adjacent to the septa. The conidia were aseptate, hyaline, ellipsoid to ovoid, and 3-5 × 2.5-3 µm (n=50). Based on the morphological characteristics, the fungus was identified as Rosellinia necatrix Berl. ex Prill. (Singleton et al., 1992) a fungus taxonomically revised to Dematophora necatrix R. Hartig (Wittstein et al., 2020). To confirm the identification, total DNA was extracted from five isolates using a DNeasy Plant Mini Kit (Qiagen, Hilden, Germany) and the ITS spacer was PCR-amplified with primers ITS1-ITS4 (White et al., 1990). The size-expected amplicons of 536 bp were purified and sequenced, the resulting sequence was trimmed and deposited in GenBank under the accession number MK937913. BLAST-n analysis revealed 98.83% nucleotide identity with some representative isolates of D. necatrix (MK888684.1; KT343972.1). To fulfill Koch’s postulates, the pathogenicity tests were carried out on fifteen 4-weeks-old potted hemp plants ‘Kompolty’. The inoculation was performed by adding 3 g of millet seeds inoculated with ten mycelial plugs, taken from the margins of a D. necatrix actively growing colony, per liter of sterile peat and perlite substrate in single pots. Moreover, ten hemp plants were inoculated with sterilized millet seed and served as negative controls. All plants were incubated at 25°C. After three weeks, inoculated plants exhibited foliar chlorosis, apical wilting, and death in two weeks, similar to what was observed in the field. Control plants did not show any symptoms. The fungus was isolated from the roots in all fifteen inoculated plants and confirmed to be D. necatrix based on morphological and molecular analysis, carried out with a second primer pair EF1-983F/ EF1-2218R targeting the transcription elongation factor 1- (Rehner and Buckley., 2005) (MW541068) that showed 99.67% nt in BLAST-n analysis. To our knowledge, this is the first report of D. necatrix infecting hemp in Europe. The farm where the problem arose has a history of cultivation for the production of apples for over 30 years. Therefore, an adaptation of D. necatrix to the new host is hypothesized. An in-depth knowledge on the diseases of hemp will be needed to relaunch hemp cultivation in this area.

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