First Report of Pod and Stem Blight and Seed Decay caused by Diaporthe longicolla on Soybean in Western Canada

In Oct. 2019, soybean plants (Glycine max) (cv. 24-10RY, R7 growth stage) with dry rot, necrosis, reddish-brown lesions, and small black fruiting bodies in linear rows were collected from fields in Manitoba (Carman, St. Adolph, Dauphin), Canada. The pods and seeds were shrivelled, small and some seeds were covered with whitish mycelium. Symptoms began as brown lesions, which darkened, elongated, causing wilt of the above stems then plant death. Microscopy showed that the fruiting bodies were pycnidia. Symptomatic stems were cut into 1-2 cm pieces and seeds surface-sterilized in 0.5% NaOCl, rinsed twice in sterilized H2O, air-dried on sterilized filter paper, and plated on PDA medium amended with 100 mg/L streptomycin sulfate at room temperature with 12-h fluorescent light/12-h dark for 3 days. The emerging hyphae were transferred using the hyphal tip method to new PDA petri dishes and incubated for 21 days (room T°). Mycelia of 20 isolates were dense, white and floccose with occasional green-yellow areas. Black stromata in concentric patterns or scattered as large masses were visible on the cultures’ back. Pycnidia formed solely or aggregated after 4-5 weeks of incubation on PDA. Alpha conidia emanated from pycnidia in creamy-to-yellowish drops and were hyaline, non-septate, ellipsoid to fusiform, and biguttulate. The average length and width of Alpha conidia were 5.5 μm and 1.5 μm, respectively (n = 30). No perithecia were seen. The cultures’ morphology was consistent with Phomopsis longicolla’s description (Hobbs et al., 1985). Seven isolates were selected for molecular characterization to confirm their identity by amplifying the ITS region with universal primers ITS4/ITS5 (White et al. 1990). All PCR amplicons were analyzed by electrophoresis through 1.5 % agarose gels and the size of PCR amplicons estimated using 1-kb plus DNA ladder (Thermo Fisher Sci., ON, Canada). PCR amplicons (~650 bp) were purified and sequenced in two directions by Psomagen Inc. (Rockville, MD, USA). ITS sequences were identical for all isolates, and GenBank searches (BLASTn: Altschul et al. 1990) confirmed species identity. ITS sequences (accessions MW466183-MW466189) were deposited in GenBank and matched the type sequence of Diaporthe longicolla strain ATCC 60325 (accession NR_144924) from G. max in USA with identities = 473/475 (99.6%) and gaps = 0/475 (0%). To confirm the pathogenicity of the seven isolates, the stems of V4-stage (four open trifolilates) soybean plants (cv. 24-10RY) were excised using a sterile scalpel. Mycelial plugs (9 mm in diameter) from 1-week-old culture of each isolate were placed over the wounded stems (Abdelmagid et al., 2019). Sterile PDA plugs were used on control plants. Six plants were used per isolate and control. Plugs of both treatments were wrapped with parafilm to avoid drying. The plants were incubated in a humidity chamber for 4 days and then in a greenhouse at 24:16°C day/night, 13:11-h light/dark cycle, and 70-80% relative humidity, and were irrigated as needed. Symptoms similar to those observed in the field were seen on the stems and seeds of all artificially-infected plants approx. 8 weeks after inoculation. Pods and seeds of inoculated plants were shrivelled and small. No symptoms were observed on control plants. Diaporthe longicolla was re-isolated only from the diseased plants and seeds. To our knowledge, this is the first report following Koch’s postulates to identify the causal pathogen of soybean pod and stem blight and seed decay in Western Canada. This will be instrumental in determining the causes of stem decay and contribute in properly dealing with soybean seed issues in Western Canada in the future.

Download Full-text

First Report of Soybean Stem Blight Caused by Phomopsis longicolla in Guangdong Province, Southern China

Plant Disease ◽

10.1094/pdis-10-12-1003-pdn ◽

2013 ◽

Vol 97 (6) ◽

pp. 844-844

Author(s):

X. Chen ◽

R. Pan ◽

D. Xu ◽

C. Ji ◽

M. Deng

Keyword(s):

Southern China ◽

Disease Incidence ◽

Guangdong Province ◽

Fluorescent Light ◽

Width Ratio ◽

Fruiting Bodies ◽

Phomopsis Longicolla ◽

First Report ◽

Stem Blight ◽

Seed Decay

In October 2011, a disease resembling stem blight of soybean was found in Zengcheng City, Guangdong Province, southern China. Symptoms began as a brown fusiform lesions on the stems, usually at the nodes. The lesions then darkened, elongated, and often girdled the stems, causing wilt of the above stems. The whole plant eventually died. There were many small, black, raised fruiting bodies in the lesions. The disease incidence was about 20%. Lesions with typical symptoms were sampled from diseased plants. Microscopic examination revealed that the fruiting bodies were pycnidia in which alpha-conidia were common but beta-conidia were rare. Alpha-conidia were hyaline, ellipsoidal to fusiform, guttulate, and measured 7.0 (4.3 to 10.0) × 3.0 (1.8 to 4.3) μm. The length/width ratio of alpha-conidia was 2.3 (1.4 to 4.5). Beta-conidia were hyaline, filiform, hamate, and measured 28.7 (18.2 to 35.7) × 1.8 (1.2 to 2.8) μm. A fungus was consistently isolated from the lesions on acidified potato dextrose agar (APDA, pH 4.5) at 25°C under intermittent fluorescent light (12 h daily). The colonies were floccose, dense, and white, with occasional green-yellow areas; the reverse was colorless with large, black stromata. To induce the production of fruiting bodies, autoclaved soybean stems were placed on the colonies growing on water agar at 25°C in darkness. Pycnidia with long beaks were observed on the stems 7 days later. The fungus was identified as Phomopsis longicolla (2). The rDNA internal transcribed spacer (ITS) region of the fungus was amplified with universal primers ITS4/ITS5 and sequenced (4). The sequences of two isolates were submitted to GenBank (Accession Nos. JX827608 and JX827609). BLASTn analysis showed that there was 99 to 100% similarity with sequences of P. longicolla deposited in GenBank (EF026104, AY857868, HQ130441, JF309198, JF309199, and AF132796). Pathogenicity tests were conducted on 14-day-old seedlings (cv. Huaxia 3) inoculated by placing mycelial plugs (5 mm in diameter and 4 days old) on slight cuts made on the lower stems (six replicates). The plugs were covered with a piece of wet cotton to maintain moisture. The control seedlings were treated the same but without mycelial plugs. All treated plants were incubated in 25°C in humid champers. Typical brown lesions with black raised pycnidia on the stems were observed 14 days after inoculation and P. longicolla was reisolated from these stem lesions. No disease was observed on control plants. To further verify that the fungus can cause seed decay, seeds were disinfected by 0.02% sodium hypochlorite and inoculated by putting them on the surface of the fungal colonies grown on APDA (pH 4.5) at 25°C. The control seeds were treated the same but without fungal colonies. All of the inoculated seeds decayed within 30 days whereas the control seeds maintained healthy. P. longicolla has been described as a pathogen causing serious stem blight and seed decay on soybean (3). The disease has been previously reported in Heilongjiang Province, northern China, but it was not known elsewhere in China (1). To our knowledge, this is the first report of P. longicolla on soybean in Guangdong Province, southern China. The pathogen may pose a serious threat to the production of soybean in this region of China. References: (1) Y. Cui et al. Plant Pathol. 58:779, 2009. (2) T. W. Hobbs et al. Mycologia 77:535, 1985. (3) S. Li et al. Plant Dis. 94:1035, 2010. (4) A. W. Zhang et al. Plant Dis. 81:1143, 1997.

Download Full-text

First Report of Colletotrichum boninense Causing Anthracnose on Pepper in China

Plant Disease ◽

10.1094/pdis-04-12-0403-pdn ◽

2013 ◽

Vol 97 (1) ◽

pp. 138-138 ◽

Cited By ~ 7

Author(s):

Y. Z. Diao ◽

J. R. Fan ◽

Z. W. Wang ◽

X. L. Liu

Keyword(s):

Internal Transcribed Spacer ◽

Severe Disease ◽

Causal Agent ◽

Its Sequences ◽

Universal Primers ◽

Pathogenicity Test ◽

Conidial Suspension ◽

Single Spore ◽

First Report ◽

Species Specific

Anthracnose, caused by Colletotrichum spp., is a severe disease and results in large losses in pepper (Capsicum frutescens) production in China (4). Colletotrichum boninense is one of the Colletotrichum species in pepper in China. In August 2011, anthracnose symptoms (circular, sunken lesions with orange to black spore masses) were observed on pepper fruits in De-Yang, Sichuan Province, China. Three single-spore isolates (SC-6-1, SC-6-2, SC-6-3) were obtained from the infected fruits. A 5-mm diameter plug was transferred to potato dextrose agar (PDA); the isolates formed colonies with white margins and circular, dull orange centers. The conidia were cylindrical, obtuse at both ends, and 10.5 to 12.6 × 4.1 to 5.0 μm. The colonies grew rapidly at 25 to 28°C, and the average colony diameter was 51 to 52 mm after 5 days on PDA at 25°C. Based upon these characters, the causal agent was identified as C. boninense. To confirm the identity of the isolates, the internal transcribed spacer (ITS) regions were amplified with the ITS1/ITS4 universal primers (1). The internal transcribed spacer (ITS) sequences (Accession No. JQ926743) of the causal fungus shared 99 to 100% homology with ITS sequences of C. boninense in GenBank (Accession Nos. FN566865 and EU822801). The identity of the causal agent as C. boninense was also confirmed by species-specific primers (Col1/ITS4) (2). In a pathogenicity test, five detached ripe pepper fruits were inoculated with 1 μl of a conidial suspension (106 conidia/mL) or five fruits with 1 μl of sterile water were kept as control. After 7 days in a moist chamber at 25°C, typical anthracnose symptoms had developed on the five inoculated fruits but not on control fruits. C. boninense was reisolated from the lesions, and which was confirmed by morphology and molecular methods as before. There have reports of C. boninense infecting many species of plants, including pepper (3). To our knowledge, this is the first report of C. boninense causing anthracnose on pepper in China. References: (1) A. K. Lucia et al. Phytopathology 93:581, 2002. (2) S. A. Pileggi et al. Can. J. Microbiol. 55:1081, 2009. (3) H. J. Tozze et al. Plant Dis. 93:106, 2009. (4) M. L. Zhang. J. Anhui Agri. Sci. 2:21, 2000.

Download Full-text

Aggressiveness of Phomopsis longicolla and Other Phomopsis spp. on Soybean

Plant Disease ◽

10.1094/pdis-94-8-1035 ◽

2010 ◽

Vol 94 (8) ◽

pp. 1035-1040 ◽

Cited By ~ 34

Author(s):

Shuxian Li ◽

Glen L. Hartman ◽

Deborah L. Boykin

Keyword(s):

Soybean Seed ◽

Poor Quality ◽

Stem Length ◽

Lesion Length ◽

Phomopsis Longicolla ◽

Phomopsis Seed Decay ◽

Stem Lesion ◽

Seed Decay ◽

Geographic Origins ◽

Soybean Plants

Phomopsis seed decay of soybean is a major cause of poor-quality soybean seed. The disease is caused primarily by the fungal pathogen Phomopsis longicolla. Aggressiveness of isolates of P. longicolla from soybean and other Phomopsis spp. from other hosts were compared by inoculating 2-week-old soybean plants of cv. Williams 82. There were significant (P ≤ 0.0001) differences among isolates based on stem length and stem lesion length. The P. longicolla soybean isolate PL16, from Mississippi, caused the shortest stem length while the non-soybean isolate P9, from Illinois, caused the greatest stem lesion length. The type isolate of P. longicolla, PL31 (Fau 600), was one of the 3 most aggressive isolates among all 48 isolates tested. The velvetleaf isolate P9 was the most aggressive among 13 isolates from non-soybean hosts. This study provided the first evaluation of aggressiveness of P. longicolla isolates from different geographic origins and the first demonstration that Phomopsis spp. isolated from cantaloupe, eggplant, and watermelon infected soybean. Knowledge about the variability of the pathogen is important for selecting isolates for breeding soybean lines with broad-based resistance to Phomopsis seed decay.

Download Full-text

First Report of Root Rot of Soybeans Caused by Corynespora cassiicola in Wisconsin

Plant Disease ◽

10.1094/pdis.1999.83.7.696b ◽

1999 ◽

Vol 83 (7) ◽

pp. 696-696 ◽

Cited By ~ 5

Author(s):

S. J. Raffel ◽

E. R. Kazmar ◽

R. Winberg ◽

E. S. Oplinger ◽

J. Handelsman ◽

...

Keyword(s):

Root Rot ◽

Growth Stage ◽

Lateral Roots ◽

Seedling Emergence ◽

Fluorescent Light ◽

Corynespora Cassiicola ◽

First Report ◽

Seedling Roots ◽

Symptomatic Tissue ◽

Soybean Plants

Corynespora cassiicola (Berk. & M. A. Curtis) C. T. Wei was isolated from diseased soybean plants (Glycine max) collected in two fields near Racine and Arlington, WI. Plants sampled at seedling emergence (VC), late vegetative (V5), and mid-reproductive (R5) stages exhibited reddish to dark brown longitudinal lesions on the exterior of the tap root extending vertically on the hypocotyl to the soil line, and extensive necrosis of lateral roots. Sample size at each growth stage was 144 plants per site. Roots were surface sterilized in 0.5% sodium hypochlorite for 2 min and sections of symptomatic tissue placed on water agar (12 g/liter) containing 100 μg of streptomycin per ml. Sporulation occurred on lesions and on mycelium that had grown out from the plant tissue onto the water agar following a 2-week incubation at 24°C under fluorescent light (280 μmol s-1 m-2). Incidence of isolation of C. cassiicola at both sites was 40% of plants sampled at growth stage VC, 67% at V5, and 78% at R5. Conidia characteristic of C. cassiicola were particularly abundant on the surface of necrotic lateral root tissue. Elongated conidia produced on water agar were 151 ± 5 μm × 15 ± 0.5 μm with an average of 13 ± 0.4 cells separated by hyaline pseudosepta (1). To confirm pathogenicity, a 1-cm lateral slice into each of four 5-day-old soybean seedling roots was made and a plug of agar taken from the margin of a colony of C. cassiicola grown on potato dextrose agar was placed in each wound and incubated for 14 days at 24°C in a growth chamber. Symptoms similar to those of diseased field plants were observed and C. cassiicola was reisolated from all plants inoculated with C. cassiicola; all controls treated with agar alone had no symptoms and C. cassiicola was recovered from none of the noninoculated controls. This is the first report of root rot caused by C. cassiicola on soybean in Wisconsin. Reference: (1) W. L. Seaman and R. A. Shoemaker. Can. J. Bot. 43:1461, 1965.

Download Full-text

First Report of Dieback Disease on Cedars Caused by Diplodia seriata in China

Plant Disease ◽

10.1094/pdis-03-14-0309-pdn ◽

2014 ◽

Vol 98 (9) ◽

pp. 1279-1279 ◽

Cited By ~ 3

Author(s):

Z. J. Jiao ◽

Y. C. Kan ◽

S. L. Huang

Keyword(s):

Morphological Characteristics ◽

Its Sequences ◽

Fluorescent Light ◽

Foeniculum Vulgare ◽

Diplodia Seriata ◽

First Report ◽

Rdna Its ◽

Rdna Its Sequences ◽

Dieback Disease ◽

Pinus Spp

Cedars (Cedrus deodara (Roxb.) G. Don) are well known as evergreen ornamental trees widely used in horticulture in temperate climates. In March 2013, dieback symptoms were found on cedar trees in different locations (including the campus of Nanyang Normal University) in Nanyang (33°01′ N, 112°29′ E), a southwestern city of Henan Province, China. Characteristic symptoms included needle discoloration and defoliation, canker formation and gummosis on trunks and branches, browning and tissue necrosis under the bark as well as dieback of branches/trunks. Of 873 cedar trees investigated, 139 (16%) were symptomatic. A total of 21 Diplodia sp. isolates were obtained from 102 tissue pieces randomly sampled from the lesion margins of 31 affected trees with a conventional method for isolation of culturable fungal species from plant tissues. Monohyphal cultures were isolated from actively growing edges of colonies to purify the isolates. The purified isolates were grown on 2% water agar with sterilized stems of Foeniculum vulgare to induce their colonies to form pycnidia (4). Unmatured conidia were hyaline, aseptate, and turned light to dark brown with maturity. Mature conidia were aseptate (rarely uniseptate), ovoid with truncated or rounded base and obtuse apex, externally smooth, roughened on the inner surface, and 8 to 11 × 23 to 26 μm (n = 50). These morphological characteristics of the isolates agreed with those of Diplodia seriata (the anamorph of Botryosphaeria obtusa) (5). The rDNA-ITS sequences of two representative isolates (xs-01 and xs-06) were amplified with primers ITS1 and ITS4. PCR products were purified and ligated with PMD-19T vector for sequencing. The rDNA-ITS sequences were submitted to GenBank with accession nos. KJ463386 and KJ549774 for isolates xs-01 and xs-06, respectively, showing 100% identity with multiple isolates of D. seriata (HQ660463, KC461297, and KF535906). Koch's postulates were fulfilled in greenhouse tests on 2-year-old cedar plantlets inoculated by the two isolates. Ten plantlets were used for the inoculation tests for each of the isolates, and their trunks were wounded to a 2 mm depth with a sterilized cork borer (3 mm diameter). The wounds were inoculated by mycelial plugs cut from 7-day-old colonies grown on potato dextrose agar (PDA) plates and wrapped with Parafilm, and those inoculated with pure PDA plugs served as control. Inoculated plantlets were incubated in a greenhouse with alternating cycles of 14 h fluorescent light/10 h darkness under moist conditions for 30 to 60 days at 28°C. Nine of 20 inoculated plantlets developed needle discoloration and shoot blight symptoms similar to those observed on naturally infected cedar trees. The control plantlets remained symptomless during the incubation period. D. seriata cultures were constantly recovered from each diseased plantlet, indicating that the isolated D. seriata isolates were responsible for the disease. D. seriata has been reported as a phytopathogen causing dieback diseases worldwide on multiple woody plant species such as olive (4), mulberry (1), Pinus spp., and Picea glauca (2,3). To our knowledge, this is the first report of D. seriata causing dieback disease on cedars in China. References: (1) M. Arzanlou et al. Arch. Phytopathol. Plant Protect. 46:682, 2013. (2) T. Burgess et al. Appl. Environ. Microbiol. 67:354, 2001. (3) G. Hausner et al. Can. J. Plant Pathol. 21:256, 1999. (4) J. Kaliterna et al. Plant Dis. 96:290, 2012. (5) A. J. L. Phillips et al. Fungal Divers. 25:141, 2007.

Download Full-text

First Report of Nectria haematococca Causing Stem Rot of Soybean in China

Plant Disease ◽

10.1094/pdis-07-11-0626 ◽

2012 ◽

Vol 96 (3) ◽

pp. 457-457 ◽

Cited By ~ 1

Author(s):

Y. Gai ◽

R. Pan ◽

D. Xu ◽

M. Deng ◽

W. Chen ◽

...

Keyword(s):

Elongation Factor ◽

Morphological Characteristics ◽

Its Region ◽

Stem Rot ◽

Universal Primers ◽

Conidial Suspension ◽

Fruiting Bodies ◽

Nectria Haematococca ◽

First Report ◽

Soybean Seedlings

In October 2010, soybean (Glycine max) plants growing in commercial soybean fields in Zengcheng City, Guangdong Province developed symptoms consisting of stem and root rot, yellowing, and defoliation of leaves. Reddish, spherical fruiting bodies appeared in lesions that developed on stems. Plants with symptoms were sampled from fields. Fruiting bodies were excised from diseased tissues. Microscopic examination revealed that they were perithecia, globose to pyriform, and measured 197 to 260 μm in diameter and 226 to 358 μm long. When squeezed gently, cylindrical to clavate asci, 7.2 to 9.6 μm in diameter and 75.4 to 92.0 μm long, containing eight ascospores were exuded from the perithecia. Ascospores were ellipsoid to obovate, two celled, slightly constricted at the septum, had longitudinal striations, and measured 4.9 to 6.0 μm in diameter and 10.6 to 15.0 μm long. The fungus was isolated from the basal stem tissues of diseased soybean plants and cultured on potato dextrose agar (PDA) medium amended with streptomycin sulfate. On PDA, the culture developed into blue-pigmented colonies with whitish mycelium that produced oval to cylindrical microconidia. Microconidia had 0 to 1 septum, ranged from 2.5 to 5.2 × 7.6 to 29.4 μm, and were produced on monophialides. Macroconidia were cylindrical to falcate, thick walled, 2 to 5 septa, and 3.5 to 6.0 × 25.4 to 66.8 μm. Chlamydospores were present and ranged from 6.8 to 13.6 × 5.5 to 9.5 μm. Orange-to-reddish perithecia were readily formed in old culture. These morphological characteristics were consistent with descriptions of Nectria haematococca (anamorph Fusarium solani) (1). The rDNA internal transcribed spacer (ITS) region and the fragment of translation elongation factor 1-alpha (EF1-α) genes of the fungus were amplified, respectively, with universal primers ITS1/ITS4 and ef1/ef2 primers and sequenced. BLAST searches showed that the ITS sequences of three isolates (GenBank Accession Nos. JN015069, JN190942, and JN190943) had 99% similarity with those of N. haematococca(GenBank Accession Nos. DQ535186, DQ535185, and DQ535183) and the EF1-α sequences of three isolates (GenBank Accession Nos. JN874641, JN874642, and JN874643) had 100% similarity with those of F. solani (GenBank Accession Nos. DQ247265 and DQ247327). Completion of Koch's postulates confirmed the pathogenicity of the isolates in a replicated experiment. Thirty-day-old soybean seedlings of cultivar Huaxia No. 3 were inoculated by soaking their root systems in a conidial suspension (106 conidia per ml) for 30 min and then transplanted in plastic pots (20 cm in diameter) and incubated at 25 ± 2°C in a greenhouse. Control plants were treated with sterile water in the same way. There were four plants per pot and there were six replicates for each treatment. Within 3 weeks, more than 70% of the inoculated plants exhibited symptoms of leaf yellowing, stem rot, and root rots while control plants were symptomless. N. haematococca was reisolated from the diseased plants. To our knowledge, this is the first report of N. haematococca causing stem rot of soybean in China and the first description of sexual reproduction of F. solani causing soybean stem rot in nature. This pathogen may pose a serious threat to soybean production in China where soybean is a main crop. Reference: (1) C. Booth. The Genus Fusarium. CAB International, Wallingford, UK, 1971.

Download Full-text

First Report of Diaporthe novem, D. foeniculina, and D. rudis Associated With Soybean Seed Decay in Serbia

Plant Disease ◽

10.1094/pdis-03-16-0353-pdn ◽

2016 ◽

Vol 100 (11) ◽

pp. 2324-2324 ◽

Cited By ~ 4

Author(s):

K. Petrović ◽

L. Riccioni ◽

M. Vidić ◽

V. Đorđević ◽

S. Balešević-Tubić ◽

...

Keyword(s):

Soybean Seed ◽

First Report ◽

Seed Decay

Download Full-text

First Report of Twig Canker on Peach Caused by Phomopsis amygdali in China

Plant Disease ◽

10.1094/pdis-04-11-0321 ◽

2012 ◽

Vol 96 (2) ◽

pp. 288-288 ◽

Cited By ~ 4

Author(s):

F. M. Dai ◽

R. Zeng ◽

J. P. Lu

Keyword(s):

Control Strategies ◽

Morphological Characteristics ◽

Universal Primers ◽

Effective Control ◽

Fluorescent Light ◽

First Report ◽

Ctab Method ◽

Pcr Products ◽

Dna Fragment ◽

Potato Sucrose Agar

During May and June of 2009, canker and twig dieback were observed with 30 to 40% incidence in trees in one peach orchard in Nanhui of Shanghai (cv. YuLu juicy peach) and one orchard (cv. JingXiu yellow peach) in Jiaxin of Zhejiang Province, China. Cankers were generally centrally positioned on the nodes at the base of shoots with sunken, reddish brown/tan-to-silver symptoms. Blight was also observed on a few shoots (1). Five samples were collected from each orchard and isolations were conducted on potato sucrose agar (PSA). Ten isolates were obtained and all had white mycelia on PSA. Black pycnidia, formed in culture, produced two types of conidia: hyaline, fusiform alpha conidia and hyaline, string-like beta conidia. Alpha conidia varied from 5.0 to 6.3 × 1.5 to 2.5 μm and beta conidia ranged from 20 to 25 × 1.2 to 1.5 μm. Morphological characteristics suggested the identity of the fungal isolates to be Phomopsis amygdali. To confirm pathogenicity, an inoculum suspension was made from one isolate (106 conidia/ml) and was sprayed until runoff onto five twigs with buds. Inoculated twigs were maintained at 26°C and 100% relative humidity in a growth chamber with a 12-h period of fluorescent light daily. Twigs inoculated with sterilized water were included as noninoculated controls. After 4 days, dark brown lesions appeared around buds on inoculated twigs. No symptoms were observed on the control twigs. Constriction cankers were reproduced and P. amygdali was reisolated from the lesions. To confirm the identity of the pathogen, total genomic DNA was extracted with the cetyltrimethylammoniumbromide (CTAB) method from the mycelia of two isolates from YuLu juicy peach and Jinxiu yellow peach (2). PCR was performed with universal primers ITS1 (5′-TCCGTAGGTGAACCTGCGG-3′) and ITS4 (5′-TCCTCCGCTTATTGATATGC-3′) to amplify a DNA fragment of approximately 550 bp. The PCR products were purified and sequenced in both directions (Sangon Biotech (Shanghai) Co., Ltd., China). The sequences (GenBank Accession Nos. HQ632013 and HQ632014) shared 98.9% identity with each other (MegAlign software; DNASTAR, Madison, WI). A comparison of these two sequences with those in GenBank showed that the sequences had the highest nucleotide similarity (99%) with P. amygdali isolate FAU1052 from peach in the southeastern United States (Accession No. AF102998). To our knowledge, this is the first report of P. amygdali causing twig canker on peach in China and will provide useful information for developing effective control strategies. References: (1) D. F. Farr et al. Mycologia 91:1008, 1999. (2) M. A. Saghai-Maroof et al. Proc. Natl. Acad. Sci. USA. 81:8014, 1984.

Download Full-text

First Report of a Rust Disease on Ohia Caused by Puccinia psidii in Hawaii

Plant Disease ◽

10.1094/pd-90-0524c ◽

2006 ◽

Vol 90 (4) ◽

pp. 524-524 ◽

Cited By ~ 65

Author(s):

J. Uchida ◽

S. Zhong ◽

E. Killgore

Keyword(s):

Native Hawaiian ◽

Rust Fungus ◽

Its Region ◽

Psidium Guajava ◽

Universal Primers ◽

Fluorescent Light ◽

Rust Disease ◽

Puccinia Psidii ◽

First Report ◽

The Family

Several species of Metrosideros (Myrtaceae), referred to as ohia in Hawaii, are endemic trees that comprise as much as 80% of the native Hawaiian forests. For centuries, these trees have provided niches for many indigenous and endangered plants and animals and are treasured by Hawaiians for their beauty and role in folklore and legends. During April 2005, a cultivated ohia plant was diagnosed by the Agricultural Diagnostic Service Center at the University of Hawaii at Manoa as infected by a rust fungus. Rust pustules containing abundant urediniospores were observed on leaves, stems, and sepals, causing discolored spots and severe deformity of young leaves and growing tips. By July 2005, a similar rust disease was observed on other plants in the family Myrtaceae; namely Syzygium jambos (L.) Alston, Eugenia koolauensis Degener, E. reinwardtiana (Blume) DC, and Psidium guajava L. Microscopic examination of the uredinia and urediniospores showed that the rust was morphologically similar to Puccinia psidii, which is reported as the guava or eucalyptus rust in Florida and Central and South America (1,2). To confirm the identity of this fungus, DNA was extracted from urediniospores of two isolates collected from ohia plants, and their nuclear ribosomal internal transcribed spacer (ITS) was amplified with two universal primers, ITS4 and ITS5 (3). Sequences of the ITS region of these isolates from ohia were identical to the P. psidii isolates provided by A. Alfenas in Brazil and M. Rayachhetry in Florida. Koch's postulate of the isolates, obtained from ohia, was performed using 1 × 108 spores/ml of urediniospores suspension in distilled water. The suspension was sprayed onto 6-month-old ohia seedlings. These inoculated seedlings were placed in clear plastic chambers maintained at 100% relative humidity and 22°C with a combination of 10-h fluorescent light period and a 14-h dark period. After 48 h of incubation, the seedlings were removed from the chambers and transferred to a greenhouse where the ambient temperature ranged from 20 to 24°C. Rust pustules appeared after 1 to 2 weeks of incubation. Symptoms first appeared as tiny, bright yellow, powdery eruptions that developed into circular, uredinial pustules on the stem and foliage. These pustules later expanded, coalesced, and became necrotic, spreading over the entire leaf and stem surfaces, and then leaves and stems were deformed and tip dieback ensued. These symptoms were the same as those observed on the naturally infected cultivated ohia plant mentioned above. P. psidii is reported to be native to South and Central America that later spread to some Myrtaceous plants in the Caribbean countries (1). It has a very wide host range within the family Myrtaceae (2). To our knowledge, this is the first report of P. psidii in Hawaii. This rust disease may pose a formidable threat to Myrtaceous species that make up the native Hawaiian forests and are grown as ornamental plants or for the production of wood chips. References: (1) T. A. Coutinho et al. Plant Dis. 82:819. 1998. (2) M. B. Rayachhetry et al. Biol. Control 22:38. 2001. (3) T. J. White et al. Page 315 in: PCR Protocols. M. A. Innis et al., eds. 1990.

Download Full-text

First Report of the Cyst Nematode (Heterodera elachista) on Rice in Hunan Province, China

Plant Disease ◽

10.1094/pdis-07-11-0576 ◽

2012 ◽

Vol 96 (1) ◽

pp. 151-151 ◽

Cited By ~ 7

Author(s):

Z. Ding ◽

J. Namphueng ◽

X. F. He ◽

D. L. Peng ◽

W. K. Huang

Keyword(s):

Body Length ◽

Leaf Length ◽

Rice Fields ◽

Its Sequences ◽

Hunan Province ◽

Universal Primers ◽

Molecular Characteristics ◽

Cyst Nematodes ◽

Lateral Field ◽

First Report

During a survey for the cyst nematodes (Heterodera elachista) from May to June of 2011, cyst nematodes were detected in hilly rice fields in five counties (Changsha, Pingjiang, Hengdong, Shaoyang, and Xiangxiang) of Hunan Province, China. Cyst nematodes obtained from soil samples and harvested rice root samples at these five locations had uniform morphological and molecular characteristics. Cysts (n = 20) had the following characteristics: spherical to lemon shaped, vulval cone ambifenestrate, vulval bridge narrow, medium sized underbridge, with a few dark brown bullae, body length (not including the neck) ranging from 354 to 586 μm (mean = 438.9 μm, st. dev. = 63.7); body width ranged from 283 to 495 μm (354.5, 60.1); fenestrate length of 30 to 50 μm (37.4, 5.0) and width of 25 to 47.5 μm (35.1, 7.1); underbridge length from 70 to 95 μm (83.4, 8.2); and vulval slit length from 30.3 to 55.5 μm (40.3, 9.1). J2 (n = 20) had the following characteristics: body length ranging from 404 to 525 μm (mean of 461.6 μm, st. dev. = 34.5); stylet length from 20 to 25 μm (22.5, 1.1) with rounded knob; tail length of 60 to 87.5 μm (67.3, 6.9); and hyaline terminal tail ranged from 30 to 50 μm (37.5, 6.4); lateral field with three lines. The mean and range of J2 were longer than those reported for H. elachista by Nobbs et al. (1) and Tanha et al. (4), but other morphological character values were within the range of those reported (4). DNA from a single cyst was extracted, the rDNA-internal transcribed spacer (ITS) and D2/D3 fragments of the 28S RNA were amplified with universal primers TW81 and AB28, D2A and D3B, respectively. Five ITS sequences (JN202913, JN202914, JN202915, JN202916, and JN202917) and five D2/D3 sequences (JN202918, JN202919, JN202920, JN202921, and JN202922) from nematode samples collected in Changsha, Hengdong, Shaoyang, Pingjiang, and Xiangxiang, respectively, were submitted to GenBank. These ITS sequences were remarkably similar to each other and exhibited 98.6 to 99.3% similarity with that of H. elachista isolate from Iran (AF498391), and 98.8 to 99.4% similarity with that of H. elachista isolates from Ningxia Province, China (HM560778 and HM560779). The D2/D3 sequences exhibited 99.7 to 100% similarity with that of H. elachista isolates from Ningxia Province, China (HM560842 and HM560843). These characteristics indicated that the five populations were H. elachista belonging to the ‘cyperi’ group (1,2). In glasshouse evaluations of the pathogenicity of these isolates, 500 second-stage juveniles were inoculated onto five 20-day-old seedlings of rice (Weiyou No.227) in 4.5-cm diameter 30-cm high tubes with six replicates. After 8 weeks, stunting and reduction of leaf length were observed and cysts were extracted from dried soil of each tube using sieves. Brown cysts (92 to 204) and white females (14 to 40) were obtained from inoculated rice from each tube. H. elachista can decrease yield by 7 to 19% and has the most severe impact during the later stages of plant growth (3). H. elachista has been previously identified from rice fields in Japan and Iran (3). To our knowledge, this is the first report of H. elachista on rice in Hunan Province, China. References: (1) J. M. Nobbs et al. Fundam. Appl. Nematol. 15:551, 1992. (2) S. A. Subbotin et al. Mol. Phylogenet. Evol. 21:1, 2001. (3) S. A. Subbotin et al. Systematics of Cyst Nematodes (Nematoda: Heteroderinae). Volume 8 Part B. Brill, Leiden, the Netherlands, 2010. (4) M. Z. Tanha et al. Nematology 5:99, 2003.

Download Full-text