First Report of Fusarium xylarioides Causing Root and Stem Rot on Aloe vera in China

Aloe vera (L.) Burm f. is a perennial herb belonging to the family liliaceae. It is widely grown for medicinal, cosmetic and vegetable use. In 2018 and 2019, a root rot disease occurred on potted A. vera plants in a nursery in the Hunan Province of China. Symptoms of the disease include water soaking lesions, brown spots on taproot or basal part of the stem. The plants were easy to pull out when the taproot is rotten or necrotic. As the disease progressed upward, leaves in the basal part of stems became red-brown and gradually fell off. In severe cases, the whole plants became rotten and wilted. For isolation purposes, diseased tissues were excised from the lesion margins, surface disinfested with 70% ethanol for 10 s, 0.1% HgCl2 for 2 min, rinsed with sterile water thrice, and then placed on potato dextrose agar (PDA) and incubated at 26°C for 3 days in the dark. When cultured on PDA, fungal strains with similar morphology were consistently isolated and purified by single spore isolation. Colonies showed thick, pink aerial mycelium with a growth rate of 1.3 cm /day. The pigmentation was more intense in the colony center and became pale orange and white at the edge of colony. When cultured on SNA (Spezieller Nährstoffarmer agar), the fungus showed less pigmentation and thinner hyphae. Microconidia were abundantly produced, clavate and oval to kidney shaped, 7.1 to 15.2 μm × 2.5 to 5.1 μm, with 0 to 1 transverse septa. Macroconidia were sickle shaped, slender, slightly incurved in apical cell and foot-shaped in the basal cell, measured 27.9 to 53.2 μm × 2.5 to 3.5 μm, with 3 to 5 septa. These morphological characteristics were similar with those of Fusarium spp. (Booth 1971). For molecular identification, genomic DNA of the fungus was extracted by cetyl trimethyl ammonium bromide method. A portion of EF-1α (translation elongation factor 1-α) and RPB1 (the largest subunit of RNA polymerase) genes were amplified and directly sequenced using the EF-1/EF-2 and Fa/G2R primers (O’Donnell et al. 2010). The EF-1α and RPB1 were deposited in the GenBank with accession numbers MT755386 and MT755387. The EF-1α and RPB1 had 97.14% (ID FD_01334) and 99.62% identity (FD_03853), respectively, to F. xylarioides strains in the Fusarium-ID database (Geiser et al. 2004). In addition, the EF1-a showed 96.825% identity to the F. lateritium CBS 119871(AM295281) (a synonym of F. xylarioides), and the RPB1 showed 99.623% identity to the F. xylarioides NRRL 25486 (JX171517.1). Accordingly, the fungus was putatively identified to be F. xylarioides. For pathogenicity assay, A.vera seedlings were pot planted using sterilized nursery soil and inoculated with conidia suspension (1 × 105 conidia/ml), which were eluted from 7-day-old PDA cultures with sterilized water, according to the method described previously (Vakalounakis et al. 2015). The collar of each potted plant was poured with 20 ml of conidia suspensions. Plants mock inoculated with sterile water were used as control. All the inoculated plants were placed in a growth chamber at 25°C under 12/12 h light/dark cycle. The inoculation assays were carried out twice, with each one had three replicated plants. After 30 days, rot symptoms seen from the roots and basal part of stems were observed on the inoculated plants, but no visible symptoms were observed on control plants. The fungus was re-isolated from the inoculated plants and identified to be F. xylarioides by morphological and molecular characteristics, thus confirming Koch’s postulates. As we know, many Fusarium species have been reported to cause root and stem rot disease in A.vera such as the F. oxysporum (Ji et al. 2007) and F. solani (Vakalounakis et al. 2015). However, to the best of our knowledge, this is the first report of F. xylarioides causing root and stem rot disease of A.vera in China. The identification of the pathogen fungus might provide a foundation for taking appropriate control strategies to this disease.

Download Full-text

First Report of Fusarium commune causing Stem Rot of Tobacco (Nicotiana tabacum) in Hunan Province, China

Plant Disease ◽

10.1094/pdis-07-20-1466-pdn ◽

2020 ◽

Author(s):

Quan Zhong ◽

Yan song Xiao ◽

Bin He ◽

Zhi Hui Cao ◽

Zhi Guo Shou ◽

...

Keyword(s):

Nicotiana Tabacum ◽

Pathogenic Fungus ◽

Morphological Characteristics ◽

Disease Diagnosis ◽

Hunan Province ◽

Stem Rot ◽

Molecular Characteristics ◽

Conidial Suspension ◽

First Report ◽

Representative Isolate

Tobacco (Nicotiana tabacum L.) is a leafy, annual, solanaceous plant grown commercially for its leaves. It is one of the most important cash crops in China. In April of 2020, tobacco stems in commercial tobacco fields developed a brown to dark brown rot, in the Hunan Province of China. Almost 20% of the plants were infected. Symptoms appeared as round water-soaked spots, then turned dark black and developed into brown necrotic lesions leading to the stem becoming girdled and rotted. Diseased stem tissue was cut and sterilized with 70% ethanol for 10 s, 0.1% HgCl2 for 2 min, rinsed with sterile distilled water three times, and then plated on potato dextrose agar (PDA) and incubated at 26°C in the dark. Six isolates with similar morphology were obtained. Colonies cultured on PDA have morphological characteristics of Fusarium spp. producing white to orange-white, densely aerial mycelium with magenta to dark violet pigmentation. Macroconidia were produced on carnation leaf agar plates (Xi et al. 2019), which were slightly curved, with apical and basal cells curved, and usually contained three or five septa, 25.50 to 41.50×3.55 to 5.80 μm (n=50). Microconidia were cylindrical, ovate-oblong, straight to slightly curved, aseptate and 5.80 to 13.75 × 3.10 to 4.10 μm (n=50). For molecular identification, the translation elongation factor 1-alpha (EF1-α), the largest subunit of RNA polymerase II gene sequences (RPB2) and the mitochondrial small subunit rDNA (mtSSU) of a representative isolate CZ3-5-6 were amplified using the primer pairs ef1/ef2 (O’Donnell et al. 1998), 5F2/7Cr (O’Donnell et al. 2010) and NMS1/ NMS2 (Li et al. 1994). The obtained EF1-α, RPB2 and mtSSU sequences (GenBank accession nos. MT708482, MT708483 and MW260121, respectively) were 99.70 %, 100% and 100% identical to strains of F. commune (HM057338.1 for EF1-α, KU171700.1 for RPB2 and MG846025 for mtSSU). Moreover, Fusarium-ID database searches revealed that the EF1-α and RPB2 were 100% identical to F. commune strains (FD_01140_EF-1a and FD_02411_RPB2). Based on the morphological and molecular characteristics of the representative isolate, the fungal species was identified as F. commune. Pathogenicity testing of a representative isolate was performed by inoculating tobacco plants, which were grown for 2.5 months in a sterile pot with autoclaved soil. Each tobacco stem was injected with 20 μl of conidial suspension (105 spores/ml). Plants inoculated with sterilized water served as control. The pathogenicity tests were performed twice using three replicate plants, and all plants were kept in humid chambers (80 × 50 × 80 cm) at 26°C with a 12-h photoperiod. After 10 days, dark brown necrotic symptoms around the inoculated site, similar to those observed in natural field, were developed in all inoculated plants, whereas no symptoms were observed on the control plants. The pathogenic fungus was re-isolated from symptomatic tissue and identified as F. commune but was not recovered from the control plants. Fusarium commune has been reported to cause root rot or stalk and stem rot on some plants, such as sugarcane (Wang et al. 2018), Gentiana scabra (Guan et al. 2016) and maize (Xi et al. 2019). However, to our knowledge, this is the first report of F. commune causing stem rot on tobacco in China. Identification of F. commune as a stem rot causing pathogen might provide important insights for disease diagnosis on tobacco caused by different Fusarium species. Overall, this disease might bring a threat to tobacco production, and appropriate control measures should be adopted to reduce losses in tobacco fields.

Download Full-text

First Report of Diaporthe hongkongensis Causing Fruit rot on Peach (Prunus persica) in China

Plant Disease ◽

10.1094/pdis-07-20-1505-pdn ◽

2021 ◽

Author(s):

Zhou Zhang ◽

Zheng Bing Zhang ◽

Yuan Tai Huang ◽

FeiXiang Wang ◽

Wei Hua Hu ◽

...

Keyword(s):

Prunus Persica ◽

Fruit Rot ◽

Hunan Province ◽

Post Inoculation ◽

Distilled Water ◽

Conidial Suspension ◽

Internal Transcribed Spacer Region ◽

First Report ◽

Representative Isolate ◽

Rot Disease

Peach [Prunus persica (L.) Batsch] is an important deciduous fruit tree in the family Rosaceae and is a widely grown fruit in China (Verde et al., 2013). In July and August 2018, a fruit rot disease was observed in a few peach orchards in Zhuzhou city, the Hunan Province of China. Approximately 30% of the fruit in more than 400 trees was affected. Symptoms displayed were brown necrotic spots that expanded, coalesced, and lead to fruit being rotten. Symptomatic tissues excised from the margins of lesions were surface sterilized in 70% ethanol for 10 s, 0.1% HgCl2 for 2 min, rinsed with sterile distilled water three times, and incubated on potato dextrose agar (PDA) at 26°C in the dark. Fungal colonies with similar morphology developed, and eight fungal colonies were isolated for further identification. Colonies grown on PDA were grayish-white with white aerial mycelium. After an incubation period of approximately 3 weeks, pycnidia developed and produced α-conidia and β-conidia. The α-conidia were one-celled, hyaline, fusiform, and ranged in size from 6.0 to 8.4 × 2.1 to 3.1 μm, whereas the β-conidia were filiform, hamate, and 15.0 to 27.0 × 0.8 to 1.6 μm. For molecular identification, total genomic DNA was extracted from the mycelium of a representative isolate HT-1 and the internal transcribed spacer region (ITS), β-tubulin gene (TUB), translation elongation factor 1-α gene (TEF1), calmodulin (CAL), and histone H3 gene (HIS) were amplified and sequenced (Meng et al. 2018). The ITS, TUB, TEF1, CAL and HIS sequences (GenBank accession nos. MT740484, MT749776, MT749778, MT749777, and MT749779, respectively) were obtained and in analysis by BLAST against sequences in NCBI GenBank, showed 99.37 to 100% identity with D. hongkongensis or D. lithocarpus (the synonym of D. hongkongensis) (Gao et al., 2016) (GenBank accession nos. MG832540.1 for ITS, LT601561.1 for TUB, KJ490551.1 for HIS, KY433566.1 for TEF1, and MK442962.1 for CAL). Pathogenicity tests were performed on peach fruits by inoculation of mycelial plugs and conidial suspensions. In one set, 0.5 mm diameter mycelial discs, which were obtained from an actively growing representative isolate of the fungus on PDA, were placed individually on the surface of each fruit. Sterile agar plugs were used as controls. In another set, each of the fruits was inoculated by application of 1 ml conidial suspension (105 conidia/ml) by a spray bottle. Control assays were carried out with sterile distilled water. All treatments were maintained in humid chambers at 26°C with a 12-h photoperiod. The inoculation tests were conducted twice, with each one having three fruits as replications. Six days post-inoculation, symptoms of fruit rot were observed on inoculated fruits, whereas no symptoms developed on fruits treated with agar plugs and sterile water. The fungus was re-isolated and identified to be D. hongkongensis by morphological and molecular methods, thus fulfilling Koch’s Postulates. This fungus has been reported to cause fruit rot on kiwifruit (Li et al. 2016) and is also known to cause peach tree dieback in China (Dissanayake et al. 2017). However, to our knowledge, this is the first report of D. hongkongensis causing peach fruit rot disease in China. The identification of the pathogen will provide important information for growers to manage this disease.

Download Full-text

First Report of Root and Stem Rot Caused by Phytophthora nicotianae on Peperomia tetraphylla in China

Plant Disease ◽

10.1094/pdis-94-9-1171c ◽

2010 ◽

Vol 94 (9) ◽

pp. 1171-1171 ◽

Cited By ~ 1

Author(s):

D. X. Zeng ◽

X. L. Wu ◽

Y. H. Li

Keyword(s):

Southern China ◽

Aerial Mycelium ◽

Its Region ◽

Soil Extract ◽

Phytophthora Nicotianae ◽

Stem Rot ◽

Molecular Characteristics ◽

Its Sequence ◽

First Report ◽

Pure Cultures

Peperomia tetraphylla, an evergreen herb, is becoming increasingly popular as a potted ornamental plant in southern China. In the summer of 2008, in some commercial flower nurseries in Shenzhen, Guangdong Province, P. tetraphylla showed extensive black stem and root rot, with leaves dropping from the rotten stem. Small pieces (approximately 3 mm2) of stems and leaves were excised from the margins of the black lesions, surface disinfected for 30 s to 1 min in 0.1% HgCl2, plated onto potato dextrose agar (PDA), and incubated at 25°C in the dark. All the plated samples yielded Phytophthora, and microscopic examination of pure cultures grown on PDA plates showed arachnoid colonies with abundant aerial mycelium, chlamydospores, and a few sporangia. Numerous sporangia were formed in sterile soil extract. Sporangia were ovoid or obpyriform, noncaducous, with prominent solitary papillae, and measured 31 to 52 μm (average 38 μm) × 21 to 34 μm (average 27 μm). Chlamydospores were spherical and 21 to 34 μm in diameter (average 28 μm). The internal transcribed spacer (ITS) region of rDNA of a single isolate was amplified using primers ITS4/ITS5 and sequenced (2). The ITS sequence, when submitted for a BLAST search in the NCBI database, showed 100% homology with the sequences of two reference isolates of Phytophthora nicotianae (Accession Nos. AY833526 and EU433396) and the consensus ITS sequence was deposited in the NCBI as Accession No. GQ499373. The isolate was identified as Phytophthora nicotianae on the basis of morphological and molecular characteristics (1). Pathogenicity of the isolate was confirmed by inoculating 1-year-old plants of P. tetraphylla growing in pots. The isolate was grown for 7 days on PDA plates and mycelial plugs, 5 mm in diameter and taken from the advancing margins of the colonies, were buried approximately 1 cm deep near the base of the stem in such a way that the mycelium on the plugs was in contact with the surface of the stem, which had been wiped earlier with 70% ethanol and gently wounded with a needle. Plants treated the same way but inoculated with sterile PDA plugs served as control plants. Three plants in each pot were inoculated and there were five replications each for the treatment and the control. All plants were kept in a greenhouse at 22 to 32°C. After 6 to 7 days, the inoculated plants showed black lesions around the mycelial plugs; symptoms of root and stem rot developed rapidly thereafter and the plants collapsed within 2 weeks. All symptoms on the inoculated plants were identical to those observed in naturally diseased plants, whereas the control plants remained healthy. The same fungus was consistently reisolated from the inoculated plants. To our knowledge, this is the first report of Phytophthora nicotianae on P. tetraphylla in China. References: (1) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society, St. Paul, MN, 1996. (2) J. B. Ristaino et al. Appl. Environ. Microbiol. 64:948, 1998.

Download Full-text

First Report of Root and Stem Rot Disease on Papaya Caused by Fusarium falciforme in India

Plant Disease ◽

10.1094/pdis-11-18-2118-pdn ◽

2019 ◽

Vol 103 (10) ◽

pp. 2676 ◽

Cited By ~ 1

Author(s):

A. K. Gupta ◽

R. Choudhary ◽

B. M. Bashyal ◽

K. Rawat ◽

D. Singh ◽

...

Keyword(s):

Stem Rot ◽

First Report ◽

Rot Disease ◽

Fusarium Falciforme

Download Full-text

First Report of Nigrospora osmanthi Causing Leaf Spot on Tartary Buckwheat in China

Plant Disease ◽

10.1094/pdis-08-20-1773-pdn ◽

2020 ◽

Author(s):

Quan Shen ◽

Xixu Peng ◽

Feng He ◽

Shaoqing Li ◽

Zuyin Xiao ◽

...

Keyword(s):

Relative Humidity ◽

Leaf Spot ◽

Plant Pathogens ◽

Hunan Province ◽

Tartary Buckwheat ◽

Tween 20 ◽

Pathogenicity Test ◽

Conidial Suspension ◽

Sterile Water ◽

First Report

Buckwheat (Fagopyrum tataricum) is a traditional short-season pseudocereal crop originating in southwest China and is cultivated around the world. Antioxidative substances in buckwheat have been shown to provide many potential cardiovascular health benefits. Between August and November in 2019, a leaf spot was found in several Tartary buckwheat cv. Pinku1 fields in Xiangxiang County, Hunan Province, China. The disease occurred throughout the growth cycle of buckwheat after leaves emerged, and disease incidence was approximately 50 to 60%. Initially infected leaves developed a few round lesions, light yellow to light brown spots. Several days later, lesions began to enlarge with reddish brown borders, and eventually withered and fell off. Thirty lesions (2×2 mm) collected from three locations with ten leaves in each location were sterilized in 70% ethanol for 10 sec, in 2% sodium hypochlorite for 30 sec, rinsed in sterile water for three times, dried on sterilized filter paper, and placed on a potato dextrose PDA with lactic acid (3 ml/L), and incubated at 28°C in the dark for 3 to 5 days. Fungal colonies were initially white and later turned black with the onset ofsporulation. Conidia were single-celled, black, smooth, spherical to subspherical, and measured 9.2 to 15.6 µm long, and 7.1 to 11.6 µm wide (n=30). Each conidium was terminal and borne on a hyaline vesicle at the tip of conidiophores. Morphologically, the fungus was identified as Nigrospora osmanthi (Wang et al. 2017). Identification was confirmed by amplifying and sequencing the ITS region, and translation elongation factor 1-alpha (TEF1-α) and partial beta-tublin (TUB2) genes using primers ITS1/ITS4 (Mills et al. 1992), EF1-728F/EF-2 (Carbone and Kohn 1999; O’Donnell et al. 1998) and Bt-2a/Bt-2b (Glass et al. 1995), respectively. BLAST searches in GenBank indicated the ITS (MT860338), TUB2 (MT882054) and TEF1-α (MT882055) sequences had 99.80%, 99% and 100% similarity to sequences KX986010.1, KY019461.1 and KY019421.1 of Nigrospora osmanthi ex-type strain CGMCC 3.18126, respectively. A neighbor-joining phylogenetic tree constructed using MEGA7.0 with 1,000 bootstraps based on the concatenated nucleotide sequences of the three genes indicated that our isolate was closely related to N. osmanthi. Pathogenicity test was performed using leaves of healthy F. tataricum plants. The conidial suspension (1 × 106 conidia/ml) collected from PDA cultures with 0.05% Tween 20 buffer was used for inoculation by spraying leaves of potted 20-day-old Tartary buckwheat cv. Pinku1. Five leaves of each plant were inoculated with spore suspensions (1 ml per leaf). An equal number of control leaves were sprayed with sterile water to serve as a control. The treated plants were kept in a greenhouse at 28°C and 80% relative humidity for 24 h, and then transferred to natural conditions with temperature ranging from 22 to 30°C and relative humidity ranging from 50 to 60%. Five days later, all N. osmanthi-inoculated leaves developed leaf spot symptoms similar to those observed in the field, whereas control leaves remained healthy. N. osmanthi was re-isolated from twelve infected leaves with frequency of 100%, fulfilling Koch’s postulates. The genus Nigrospora has been regarded by many scholars as plant pathogens (Fukushima et al. 1998) and N. osmanthi is a known leaf blight pathogen for Stenotaphrum secundatum (Mei et al. 2019) and Ficus pandurata (Liu et al. 2019) but has not been reported on F. tataricum. Nigrospora sphaerica was also detected in vegetative buds of healthy Fagopyrum esculentum Moench (Jain et al. 2012). To our knowledge, this is the first report of N. osmanthi causing leaf spot on F. tataricum in China and worldwide. Appropriate strategies should be developed to manage this disease.

Download Full-text

First Report of Stem Rot Disease of Miracle Plant (Bryophyllum pinnatum) Caused by Athelia rolfsii in Tripura, India

Plant Disease ◽

10.1094/pdis-05-20-1086-pdn ◽

2021 ◽

pp. PDIS-05-20-1086

Author(s):

D. Kamil ◽

A. Bahadur ◽

P. Debnath ◽

A. Kumari ◽

S. P. Choudhary ◽

...

Keyword(s):

Stem Rot ◽

First Report ◽

Athelia Rolfsii ◽

Rot Disease ◽

Bryophyllum Pinnatum

Download Full-text

First Report of Alternaria alternata causing fruit Rot on Tetradium ruticarpum in China

Plant Disease ◽

10.1094/pdis-08-20-1853-pdn ◽

2020 ◽

Author(s):

Miaolian Xiang ◽

Shucheng Li ◽

Fan Wu ◽

Xianyang Zhao ◽

Yinbao Wang ◽

...

Keyword(s):

Relative Humidity ◽

Alternaria Alternata ◽

Sequence Data ◽

Elongation Factor ◽

Fruit Rot ◽

Effective Control ◽

Molecular Characteristics ◽

Sterile Water ◽

First Report ◽

Initial Symptoms

Tetradium ruticarpum, previously and commonly known as Evodia rutaecarpa, is a tree that produces a fruit which is one of the most important traditional Chinese medicine herbs in China (Zhao et al. 2015). In July 2019, an investigation of diseases of T. ruticarpum was conducted in the farmland of Ruichang County (29.68° N, 115.65° E), Jiujiang City, China. An unknown fruit rot disease was observed and the incidence rate was estimated to be 60% to 70% within a 5,000 m2 area. The early symptoms appeared as small circular to irregular dark brown or black spots on the fruit, which gradually coalesced to a light brown-to-black discoloration and caused fruit rot. To identify the causal agent of the disease, 10 diseased fruits were collected and surface disinfected with 2% sodium hypochlorite for 2 min, 70% ethanol for 30 s, rinsed in sterile water and dried on filter paper. Tissues from non-symptomatic tissue as well as from the margin between healthy and affected edge were incubated on potato dextrose agar (PDA) at 25±1°C (12 h light/dark) with 90% relative humidity for 5 days. The colonies were brown to black with abundant whitish margins. Conidiophores were brown and measured 20.40 – 43.10×1.30 – 4.20 μm (25.47 × 2.35 µm on average, n=50). Conidia produced in single or branched chains, were obclavate or ovoid, approximately 9.90 – 32.80×6.50 – 14.50 μm (28.75×12.57 µm on average, n=50) with 2 to 5 transverse septa and 0 to 3 longitudinal septa. The colonies were consistent with Alternaria alternata (Simmons 2007). For molecular identification, the f partial internal transcribed spacer (ITS) regions, Glyceraldehyde-3-phosphate dehydrogenase (gapdh) genes, translation elongation factor 1-alpha (TEF) and Alternaria major allergen (Alt a1) gene of the isolate were amplified using primers ITS1/ITS4 (White et al. 1990), GDF/GDR (Templeton et al. 1992), EF1-728F/EF1-986R (Carbone and Kohn 1999) and Alt-for/Alt-rev (Hong et al. 2005). Sequence data showed 100% homology to A. alternata (GenBank accessions No.MN625176.1 (570/570 bp), MK683866.1 (618/618 bp), MK637432.1 (281/281 bp), KT315515.1 (488/488 bp)), respectively and the sequence data were deposited into GenBank with accession numbers MN897753 (ITS), MT041998 (gapdh), MT041999 (TEF), and MT042000 (Alt a1). Based on both morphological and molecular characteristics, the pathogen was identified as A. alternata. To confirm pathogenicity, 10 μl of a spore suspension (1.0 × 106 conidia/ml) obtained from 5-day-old PDA cultures of the strain were inoculated on 20 wounded (using sterile needle) and 20 nonwounded healthy T. ruticarpum fruits previously disinfected in 75% ethanol. Control fruits including 20 wounded fruits and 20 nonwounded fruits were inoculated with sterilized water. All fruits were incubated at 25±1°C (12 h light/dark) with 90% relative humidity. Four days later, all the wounded and non-wounded fruits showed the initial symptoms of black rot which was similar to that observed in the field, while the wounded and nonwounded fruits treated with sterile water remained healthy. The same pathogen was again isolated from the inoculated fruits. The pathogenicity experiment was repeated three times with the same results. As far as we know, this is the first report of A. alternata causing fruits rot on T. ruticarpum in China, and the identification of the pathogen will provide useful information for developing effective control strategies.

Download Full-text