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 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 ultimum Crown and Root Rot of Industrial Hemp in the United States

Plant Disease ◽  
2018 ◽  
Vol 102 (10) ◽  
pp. 2045-2045 ◽  
Author(s):  
J. Beckerman ◽  
J. Stone ◽  
G. Ruhl ◽  
T. Creswell
Keyword(s):  
United States ◽  
Root Rot ◽  
Pythium Ultimum ◽  
The United States ◽  
First Report ◽  
Crown And Root Rot ◽  
Industrial Hemp

scholarly journals First Report of Fusarium falciforme (FSSC 3+4) Causing Rot of Industrial Hemp (Cannabis sativa) in California

Plant Disease ◽  
2021 ◽  
Author(s):  
Kelley Rose Paugh ◽  
Johanna Del Castillo Múnera ◽  
Cassandra L Swett
Keyword(s):  
Root Rot ◽  
Cannabis Sativa ◽  
Negative Control ◽  
Stem Rot ◽  
Tween 20 ◽  
Post Inoculation ◽  
First Report ◽  
Fusarium Falciforme ◽  
Stem Lesions ◽  
Industrial Hemp

Industrial hemp (Cannabis sativa) is a newly legal crop in California that is grown for cannabidiol oil, fiber and seed. In August 2019, whole plant decline and root rot were observed affecting <5% of plants in two industrial fields in Fresno County, CA. Symptoms included chlorotic, collapsed foliage, stem vascular discoloration, and root rot with abundant mycelial growth. Stem and root segments (1-2 cm) from three to five diseased plants were agitated in 0.1% tween-20 and soaked in 70% ethanol for 30 s and 1% NaOCl for 2 min. After incubating for 5 to 7 days on 1:10 potato dextrose agar (PDA) amended with tetracycline, Fusarium selective medium (FSM), and PARP (pimaricin + ampicillin + rifampicin + pentachloronitrobenzene [PCNB] agar) medium, white to pale cream aerial mycelium emerged from tissue of all plants on PDA and FSM but not PARP. Isolates cultured on 0.1% potassium chloride agar formed heads of microconidia on long monophialides consistent with the Fusarium solani species complex (FSSC) (Leslie and Summerell 2008). To obtain pure cultures of two isolates (CS529 and CS530), a single-hyphal tip was excised and grown on PDA. DNA was extracted from actively growing mycelium (PrepMan Ultra kit). The translation elongation factor gene (EF-1α) was amplified via PCR using EF1/EF2 primers (O’Donnell et al. 1998). Sequences of the two isolates were identical and deposited under accession number MW892973 in GenBank. The 599 bp sequence was 99.33% identical to FSSC 3 + 4 (Fusarium falciforme) accessions FD_01443_EF-1a based on FUSARIUM-ID BLAST analysis. To evaluate pathogenicity, stems of hemp plants (cv. ‘Berry Blossom’; n=8 plants per isolate) were wounded by penetrating the epidermis in an area about 0.5-cm square by 1-mm deep and 8-inches above the soil line. A 0.5 cm-diameter plug of 7-day old F. falciforme-colonized PDA was placed against the wound. Inoculation sites were loosely wrapped with parafilm for 2 days. A negative control consisted of a sterile PDA plug (n=3). Treatments were arranged in a completely randomized design in a greenhouse. The experiment was conducted once, due to regulatory restrictions at campus facilities. At 61 days post-inoculation, external stem lesions were significantly larger in diameter (P < 0.05; Tukey’s HSD) in plants inoculated with CS529 (8 ± 1 mm) compared to the control (2 ± 0 mm), and larger but not significant for CS530 (6 ± 1 mm). Internal stem lesions (i.e., rot in stele) were observed in plants inoculated with CS529 (9 ± 3 mm); stem rot was very minor in plants treated with CS530 (1 ± 1 mm) and nonexistent for control plants. No other disease symptoms were observed. F. falciforme was isolated from stems of CS529- and C530-inoculated plants. Sequences of re-isolates matched 100% with accession MW892973. These results suggest that F. falciforme causes rot in hemp in California. These studies specifically confirm stem rot abilities; field observations of root rot indicate root rotting abilities, but further tests are needed for confirmation. This is the first report of F. falciforme causing disease in industrial hemp. FSSC was described as causing foot rot in hemp in Italy (Sorrentino et al. 2019), but these isolates belonged to phylogenetic species 5 (F. solani) not F. falciforme. In addition, F. falciforme was reported as causing root rot in hydroponically grown cannabis (Punja and Rodriguez 2018). These studies provide the foundation for development of management tools for hemp disease.

scholarly journals First Report of Crown and Root Rot Caused by Rhizoctonia solani AG-4 on Banana Passionflower (Passiflora mollissima) in Italy

Plant Disease ◽  
2011 ◽  
Vol 95 (9) ◽  
pp. 1194-1194 ◽  
Author(s):  
G. Polizzi ◽  
D. Aiello ◽  
V. Guarnaccia ◽  
A. Panebianco ◽  
P. T. Formica
Keyword(s):  
Rhizoctonia Solani ◽  
Root Rot ◽  
Disease Incidence ◽  
Morphological Characteristics ◽  
Fluorescent Light ◽  
Disease Symptoms ◽  
First Report ◽  
Pathogenicity Tests ◽  
Crown And Root Rot ◽  
Safranin O

The genus Passiflora (Passifloraceae family) contains more than 500 species and several hybrids. In Italy, some of these species and hybrids are grown as ornamental evergreen vines or shrubs. During August and September 2010, a crown and root rot was observed in a stock of approximately 6,000 potted 2-year-old plants of Passiflora mollissima (Kunth) Bailey, commonly known as the banana passionflower, in a nursery located in eastern Sicily (southern Italy). Disease incidence was approximately 20%. Disease symptoms consisted of water-soaked lesions at the crown and a root rot. Successively, older crown lesions turned light brown to brown and expanded to girdle the stem. As crown and root rot progressed, basal leaves turned yellow and gradually became necrotic and infected plants wilted and died. A fungus with mycelial and morphological characteristics of Rhizoctonia solani Kühn was consistently isolated from crown lesions and brown decaying roots when plated on potato dextrose agar (PDA) amended with streptomycin sulfate at 100 μg/ml. Fungal colonies were initially white, turned brown with age, and produced irregularly shaped, brown sclerotia. Mycelium was branched at right angles with a septum near the branch with a slight constriction at the branch base. Hyphal cells removed from 10 representative cultures grown at 25°C on 2% water agar were determined to be multinucleate when stained with 1% safranin O and 3% KOH solution (1) and examined at ×400. Anastomosis groups were determined by pairing isolates on 2% water agar in petri plates (4). Pairings were made with tester strains of AG-1, AG-2, AG-3, AG-4, AG-5, AG-6, and AG-11. Anastomosis was observed only with tester isolates of AG-4 (3). Pathogenicity tests were performed on container-grown, healthy, 3-month-old cuttings. Twenty plants of P. mollissima were inoculated near the base of the stem with five 1-cm2 PDA plugs from 5-day-old mycelial plugs obtained from two representative cultures. The same number of plants served as uninoculated controls. Plants were maintained at 25°C and 95% relative humidity with a 12-h fluorescent light/dark regimen. Wilt symptoms due to crown and root rot, identical to ones observed in the nursery, appeared 7 to 8 days after inoculation with either of the two isolates and all plants died within 20 days. No disease was observed on control plants. R. solani AG-4 was reisolated from symptomatic tissues and identified as previously described, confirming its pathogenicity. Damping-off or crown and root rot due to R. solani were previously detected on P. edulis in Brazil, Africa, India, Oceania, and Australia (2). To our knowledge, this is the first report of R. solani causing crown and root rot on P. mollissima. References: (1) R. J. Bandoni. Mycologia 71:873, 1979. (2) J. L. Bezerra and M. L. Oliveira. Fitopathol. Brasil. 9:273, 1984. (3) D. E. Carling. Page 37 in: Grouping in Rhizoctonia solani by Hyphal Anastomosis Reactions. Kluwer Academic Publishers, the Netherlands, 1996. (4) C. C. Tu and J. W. Kimbrough. Mycologia 65:941, 1973.

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 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.

scholarly journals First Report of Crown and Root Rot Caused by Pythium aphanidermatum on Tomato in Italy

Plant Disease ◽  
2021 ◽  
pp. PDIS-10-20-2246
Author(s):  
G. Gilardi ◽  
G. Tabone ◽  
V. Guarnaccia ◽  
A. Garibaldi ◽  
M. L. Gullino
Keyword(s):  
Root Rot ◽  
Pythium Aphanidermatum ◽  
First Report ◽  
Crown And Root Rot

scholarly journals First Report of a Phytopythium litorale Species Causing Crown and Root Rot on Rhododendron pulchrum in China

Plant Disease ◽  
2021 ◽  
Author(s):  
Yaxing Li ◽  
Yangfan Feng ◽  
Cuiping Wu ◽  
Junxin Xue ◽  
Binbin Jiao ◽  
...  
Keyword(s):  
Root Rot ◽  
Morphological Characters ◽  
Morphological Features ◽  
Crown Rot ◽  
Sterile Water ◽  
First Report ◽  
Inoculation Method ◽  
Platanus Orientalis ◽  
Crown And Root Rot ◽  
Root Tissues

During a survey of pathogenic oomycetes in Nanjing, China from June 2019 to October 2020, at least ten adjacent Rhododendron pulchrum plants at a Jiangjun Mountain scenic spot showed symptoms of blight, and crown and root discoloration . Symptomatic root tissues collected from three 6-year-old plants were rinsed with water, cut into 10-mm pieces, surface sterilized with 70% ethanol for 1 min, and plated onto 10% clarified V8 PARP agar (cV8A-PARP) containing pimaricin (20 mg/liter), ampicillin (125 mg/liter), rifampicin (10 mg/liter), and pentachloronitrobenzene (20 mg/liter). Four Pythium-like isolates were recovered after three days of incubation at 26°C, and purified using hyphal-tipping. Ten agar plugs (2×2 mm2) of each isolate were grown in 10 mL of 10% clarified V8 juice (cV8) in a 10 cm plate at 26°C for 3 days to produce mycelial mats, and then the cV8 was replaced with sterile water. To stimulate sporangial production, three to five drops of soil extract solution were added to each plate. Sporangia were terminal, ovoid to globose, and the size is 24 to 45.6 (mean 34.7) (n=10.8) in length x 23.6 to 36.0 (mean 29.8) (n=6.2) in width. Gametangia were not observed in cV8A or liquid media after 30 days. For colony morphology, the isolates were sub-cultured onto three solid microbial media (cV8A-PARP, potato dextrose agar, corn meal agar) . All isolates had identical morphological features in the three media. Complete ITS and partial LSU and cox2 gene regions were amplified using primer pairs ITS1/ITS4, NL1/NL4, and FM58/FM66 , respectively. The ITS, LSU, and cox2 sequences of isolate PC-dj1 (GenBank Acc. No. MW205746, MW208002, MW208003) were 100.00% (936/936 nt), 100.00% (772/772 nt), and 99.64% (554/556 nt) identical to those of JX985743, MT042003, and GU133521, respectively. We built a maximum-likelihood tree of Phytopythium species using the concatenated dataset (ITS, LSU, cox2) to observe interspecific differences. Based on the morphological characters and sequences, isolate PC-djl was identified as Phytopythium litorale . As the four isolates (PC-dj1, PC-dj2, PC-dj3 and PC-dj4) tested had identical morphological characters and molecular marker sequences, the pathogenicity of the representative isolate, PC-dj1, was tested using two inoculation methods on ten one-year-old R. pulchrum plants. For the first inoculation method, plants were removed from the pot, and their roots were rinsed with tap water to remove the soil. Each of these plants was placed in a glass flask containing 250 mL of sterile water and 10 blocks (10 x 10 mm2) of mycelial mats harvested from a three-day-old culture of P. litorale, while the other plant was placed in sterile water as a control, and incubated at 26°C. After three days, symptoms including crown rot, root rot and blight was observed on the inoculated plants whereas the control remained asymptomatic. For the second inoculation method, ten plants were dug up to expose the root ball. Ten three-day-old cV8A plugs (5×5 mm2) from a PC-dj1 culture or sterile cV8A plugs were evenly insert into the root ball of a plant before it was planted back into the original pots. Both plants were maintained in a growth chamber set at 26°C with a 12/12 h light/dark cycle and irrigated as needed. After 14 to 21 days, the inoculated plant had symptoms resembling those in the field , while the control plant remained asymptomatic. Each inoculation method was repeated at triplicate and the outcomes were identical. Phytopythium isolates with morphological features and sequences identical to those of PC-dj1 were recovered from rotted crown and root tissues of all inoculated plants. Previously, P. litorale was found causing diseases of apple and Platanus orientalis in Turkey, fruit rot and seedling damping-off of yellow squash in southern Georgia, USA. This is the first report of this species causing crown and root rot on R. pulchrum, an important ornamental plant species in China. Additional surveys are ongoing to determine the distribution of P. litorale in the city of Nanjing.

scholarly journals First report of Calonectria tunisiana causing crown and root rot on Eucalyptus globulus

2020 ◽  
Vol 102 (4) ◽  
pp. 1353-1353
Author(s):  
Dalia Aiello ◽  
Alberto Fiorenza ◽  
Giorgio Gusella ◽  
Giancarlo Polizzi
Keyword(s):  
Root Rot ◽  
Eucalyptus Globulus ◽  
First Report ◽  
Crown And Root Rot
Sign in / Sign up

Export Citation Format

Share Document