scholarly journals First Report on the Presence of Leptosphaeria maculans Pathogenicity Group-3, the Causal Agent of Blackleg of Canola in Manitoba

Plant Disease ◽  
2003 ◽  
Vol 87 (10) ◽  
pp. 1268-1268 ◽  
Author(s):  
W. G. D. Fernando ◽  
Y. Chen
Keyword(s):  
Leptosphaeria Maculans ◽  
Fluorescent Light ◽  
Sodium Hypochlorite Solution ◽  
Distilled Water ◽  
Brassica Napus L ◽  
First Report ◽  
Pure Cultures ◽  
Pathogenic Variability ◽  
Serious Disease ◽  
Highly Virulent

Blackleg, caused by Leptosphaeria maculans (Desmaz.) Ces. & De Not. (anamorph = Phoma lingam) (Tode:Fr.) Desmaz.), is an economically important and serious disease of canola (Brassica napus L.) in Australia, Europe, and Canada. L. maculans isolates can be categorized into four pathogenicity groups (PGs) on the basis of the interaction phenotypes (IP) on the differential canola cvs. Westar, Glacier, and Quinta (1) by using a standard screening protocol in the greenhouse. PG1 isolates are weakly virulent and PG2, PG3, and PG4 isolates are highly virulent. In Manitoba, L. maculans population consists mainly of PG2 (virulent on cv. Westar; avirulent on cvs. Glacier and Quinta) and a few PG1 isolates (avirulent on all three differentials). The Oilseed Pathology Lab in the Department of Plant Science, University of Manitoba examines the pathogenic variability of blackleg isolates obtained from Manitoba each year. In 2002, the blackleg-resistant cv. Q2, was found to be severely infected in Roland, Manitoba. The canola stubble collected from a coop trial plot (Roland, Manitoba) and a farm in East Selkirk (60 km northeast of Winnipeg, Manitoba) was isolated for the blackleg fungus. Small pieces of stubble were cut from the pseudothecia forming section and surface sterilized with 1% sodium hypochlorite solution for 3 to 5 min and then rinsed in sterile distilled water. V8 agar medium containing 1% streptomycin sulphate was used to culture the isolates under continuous cool-white fluorescent light for 14 days. Pure cultures of the pathogen were isolated and characterized as L. maculans by means of colony morphology, pycnidia, and microscopic observations of pycnidiospores. Pycnidiospores that formed on V8 plates were flooded with 10 ml of sterile distilled water and then harvested by filtering through sterilized Miracloth and kept at -20°C. The isolates were passed once through cv. Westar to maintain their virulence. The PG test was performed with the three differential cultivars. Two additional cultivars, Q2 (resistant to PG2 isolates) and Defender (moderately resistant to PG2 isolates), were included for comparisons. Twelve 7-day-old cotyledons of each differential cultivar grown in Metro Mix were wound inoculated with a 10-μl droplet of pycnidiospore suspension (1 × 107 pycnidiospores per ml). Inoculated cotyledons were maintained in the greenhouse (16/21°C night/day and a 16-h photoperiod). The experiment was repeated twice. Disease severity on cotyledons was assessed 12 days postinoculation by using a 0 to 9 scale (2). All five isolates from Roland and East Selkirk were highly virulent on Glacier (6.4 to 7.7), Q2 (7.1 to 8.2), and Defender (7.2 to 8.4), but intermediately virulent on Quinta (4.5 to 5.4). This clearly indicated that these isolates were of PG3. Isolates of PG2 have been predominant in Manitoba for the past 25 years, and highly virulent isolates belonging to PG3 had not been detected previously. To our knowledge, this is the first report of the presence of PG3 in L. maculans in Manitoba. References: (1) A. Mengistu et al. Plant Dis. 75:1279, 1991. (2) P. H. Williams. Crucifer Genetics Cooperatives (CrGC) Resource Book, University of Wisconsin—Madison, 1985.

scholarly journals First Report of Canola Blackleg Caused by Pathogenicity Group 4 of Leptosphaeria maculans in Manitoba

Plant Disease ◽  
2005 ◽  
Vol 89 (3) ◽  
pp. 339-339 ◽  
Author(s):  
Y. Chen ◽  
W. G. D. Fernando
Keyword(s):  
Leptosphaeria Maculans ◽  
Evolutionary Potential ◽  
Brassica Napus L ◽  
Pathology Laboratory ◽  
Canadian Prairies ◽  
First Report ◽  
Pure Cultures ◽  
Plant Pathol ◽  
High Level ◽  
Highly Virulent

Leptosphaeria maculans (Desmaz.) Ces. & de Not., causal agent of blackleg of canola (Brassica napus L.), was initially placed in several pathogenicity groups (PG) on the basis of the interaction phenotypes (IP) of L. maculans isolates on the differential canola cvs. Westar (W), Glacier (G), and Quinta (Q) (4). PG1 isolates are weakly virulent and PG2, PG3, and PG4 isolates are highly virulent. In Manitoba, the L. maculans population consists mainly of PG2 isolates (virulent on W and avirulent on G and Q), a few PG1 isolates (avirulent on W, G, and Q), and PGT (virulent on W and Q, but avirulent on G) (3). Since the blackleg fungus is known to have a high level of evolutionary potential, the Oilseed Pathology Laboratory at the University of Manitoba, Winnipeg, Canada, examines the pathogenic variability of L. maculans isolates from the Canadian Prairies and North Dakota each year. During 2002, the presence of PG3 (virulent on W and G and avirulent on Q) was reported in Manitoba (1). During 2003, a canola field located at La Riviere, Manitoba, 200 km southwest of Winnipeg, was found to be severely affected by blackleg. Stubble from this field was arbitrarily collected in mid-April 2004, and 98 single-pycnidia pure cultures were obtained by isolating fungi from surface-sterilized (2% sodium hypochlorite), infested residue, cultured on V8 agar at room temperature under cool-white florescent light for 24 h. Pycnidiospores were harvested after 14 days of incubation using the Miracloth filtering method (1). PG testing was performed using the three differential cultivars in the greenhouse. Known PG2, 3, and 4 isolates, 86-12, Liffole-6, and PL30.2, respectively, were included as positive controls. For each of the 98 isolates, 12 7-day-old cotyledons of each differential cultivar grown in Metro Mix were wound-inoculated with 10 μl of a pycnidiospore suspension (1 × 107 per ml) (1). Inoculated plants were maintained in the greenhouse (16/21°C night/day and a 16-h photoperiod with cool-white florescent light). The experiment was repeated three times. Disease severity on cotyledons was assessed 12 days after inoculation with a 0 to 9 scale (0 to 2 = resistant; 3 to 6 = intermediate; and 7 to 9 = susceptible). Of the 98 isolates tested, five were PG1, 51 were PG2, 24 were PG3, 13 were PGT, and five were PG4. The isolates classified as PG4 gave IP reactions of 7 to 9, 7 to 9, and 6.6 to 8.2, on W, G, and Q, respectively. PG3 was reported one year ago, but highly virulent isolates belonging to PG4 have not been previously detected in Manitoba. To our knowledge, this is the first report of the occurrence of PG4 isolates of L. maculans, and the first report of PG4 causing canola blackleg in Manitoba. The appearance of PG4 may be evidence of pathogen population changes occurring under high-selection-pressure exerted by resistance genes in commercial cultivars (2), or through importation of PG4 isolates with canola seed. References: (1) W. G. D. Fernando and Y. Chen. Plant Dis. 87:1268, 2003. (2) B. J. Howlett. Can. J. Plant Pathol. 26:245, 2004. (3) M. Keri et al. Can. J. Plant Pathol. 23:199, 2001. (4) A. Mengistu et al. Plant Dis. 75:1279, 1991.

scholarly journals First Report of Pathogenicity Groups 3 and 4 of Leptosphaeria maculans on Canola in North Dakota

Plant Disease ◽  
2005 ◽  
Vol 89 (7) ◽  
pp. 776-776 ◽  
Author(s):  
C. A. Bradley ◽  
P. S. Parks ◽  
Y. Chen ◽  
W. G. D. Fernando
Keyword(s):  
North Dakota ◽  
Leptosphaeria Maculans ◽  
Fluorescent Light ◽  
Western Canada ◽  
Brassica Napus L ◽  
Virulent Strains ◽  
Differential Cultivar ◽  
Screening Protocol ◽  
Weakly Virulent ◽  
Highly Virulent

Blackleg, caused by Leptosphaeria maculans (Desmaz) Ces. & de Not (anamorph = Phoma lingam), is an economically important disease of canola (Brassica napus L.) worldwide and was first detected in North Dakota in 1991 (3). L. maculans can be categorized into one of several pathogenicity groups (PGs) on the basis of the interaction phenotypes in differential canola cvs. Westar, Glacier, and Quinta by using a standard screening protocol in the greenhouse (4). With this system, PG1 strains are weakly virulent and PG2, PG3, and PG4 are highly virulent. The predominant strains of L. maculans in North Dakota are PG1 and PG2 (3). In cooperation with the Oilseed Pathology Lab in the Department of Plant Science, University of Manitoba, blackleg-infested canola stubble was collected arbitrarily from fields in North Dakota during August and September of 2003. Isolates of the pathogen were obtained by plating surface-sterilized (2% NaOCl), collected stubble on V8 agar containing 0.03% chloramphenicol at 22°C under continuous cool-white fluorescent light. Pycnidiospores were harvested from single pycnidia after 14 days of incubation with the Miracloth filtering method (2) and stored at -20°C. Each isolate was passed once through cv. Westar to maintain virulence. Isolates were confirmed as being L. maculans by the presence of characteristic pink pycnidia formed on V8 agar and the characteristic symptoms caused on inoculated cotyledons of cv. Westar. The PG test was performed using a standard screening protocol (4) and was repeated three times for each isolate. For each isolate, 12 7-day-old cotyledons of each differential cultivar were wound inoculated with 10 μl of a pycnidiospore suspension (1 × 107 per ml). Disease severity on cotyledons was assessed 12 days after inoculation with a 0 to 9 scale (0 to 2 = resistant; 3 to 6 = intermediate; and 7 to 9 = susceptible). A total of 106 isolates were obtained from the stubble collected from 47 fields. Of these isolates, three were characterized as PG1, 94 as PG2, six as PG3, and one as PG4; two isolates could not be characterized according to the PG system as described (4). PG3 isolates originated from two fields in Cavalier County and one field in Ward County. The PG4 isolate was from Cavalier County. To our knowledge, this is the first time highly virulent strains of PG3 and PG4 have been detected in North Dakota. PG3 and PG4 strains of L. maculans were found only recently in western Canada (1,2). The discovery of these PGs in North Dakota and western Canada has immense implication to canola breeding programs and blackleg control, since these PGs may cause greater levels of blackleg severity on canola cultivars that are resistant to only PG2 type isolates. References: (1) Y. Chen and W. G. D. Fernando. Plant Dis. 89:339, 2005. (2) W. G. D. Fernando and Y. Chen. Plant Dis. 87:1268, 2003. (3) H. A. Lamey and D. E. Hershman. Plant Dis. 77:1263, 1993. (4) A. Mengistu et al. Plant Dis. 75:1279, 1991.

scholarly journals First Report of Pathogenicity Group-3 of Leptosphaeria maculans on Winter Rape in Hungary

Plant Disease ◽  
2006 ◽  
Vol 90 (5) ◽  
pp. 684-684 ◽  
Author(s):  
Sz. Szlávik ◽  
T. Barasits ◽  
W. G. D. Fernando
Keyword(s):  
Leptosphaeria Maculans ◽  
Fluorescent Light ◽  
Single Spore ◽  
Winter Rape ◽  
Brassica Napus L ◽  
Current Time ◽  
First Report ◽  
Culture Characteristics ◽  
Pathogenicity Group ◽  
Group 3

Blackleg, caused by Leptosphaeria maculans, is an increasing threat to winter rape (Brassica napus L.) in Hungary. The winter rape acreage has been increasing, and the occurrence and severity of the disease has become widespread in all rapeseed-growing regions throughout Hungary in a very short time. The blackleg-infected rape stubbles were collected in the autumn of 2003 in Ikervár, County Vas where the disease was severe. Ascospores were obtained from pseudothecia growing on infected rape stubble (susceptible cvs. GK Helga and Aladin). Three single-spore cultures were grown on V8 agar medium at room temperature and fluorescent light. The culture characteristics fit the type culture description for L. maculans. Pycnidiospores that formed on V8 plates were flooded with 10 ml of sterile distilled water. Seeds of cvs. Westar, Glacier, and Quinta obtained from the Department of Plant Science, University of Manitoba, Canada were sown in plastic pots containing peat mix. Seedlings were maintained in a growth chamber at 24°C with 90% relative humidity and a 16-h photoperiod. Seven days after sowing, cotyledons were wound inoculated with a 10-μl droplet of pycnidiospore suspension (1.5 × 107 spores ml-1). Interaction phenotypes (IP) were scored 10 days after inoculation using a 0 to 9 scale (1). All three isolates from Ikervár were highly virulent on cvs. Westar (8.8 to 8.9) and Glacier (8.1 to 8.3) and avirulent on cv. Quinta (0.8 to 0.9). The IP ratings indicated that these isolates belonged to pathogenicity group-3 (PG-3). To our knowledge, this is the first report of the presence of L. maculans PG-3 in Hungary. At the current time, PG-3 has caused at least 30% yield losses in susceptible cultivars of winter rape. Reference: (1) A. Mengistu et al. Plant Dis. 75:1279, 1991.

scholarly journals First Report of Seedborne Fusarium thapsinum and its Pathogenicity on Soybean (Glycine max) in the United States

Plant Disease ◽  
2014 ◽  
Vol 98 (12) ◽  
pp. 1745-1745 ◽  
Author(s):  
R. Pedrozo ◽  
C. R. Little
Keyword(s):  
United States ◽  
The United States ◽  
Soybean Plant ◽  
Sodium Hypochlorite Solution ◽  
Distilled Water ◽  
Seedling Mortality ◽  
Beta Tubulin ◽  
First Report ◽  
Significant Difference ◽  
Germinated Seeds

A three-year survey from 2010 to 2012 was conducted in Kansas to investigate the identity and diversity of seedborne Fusarium spp. in soybean. A total of 408 soybean seed samples from 10 counties were tested. One hundred arbitrarily selected seeds from each sample were surface-sterilized for 10 min in a 1% sodium hypochlorite solution to avoid contaminants and promote the isolation of internal fusaria. Seeds were rinsed with sterile distilled water and dried overnight at room temperature (RT). Surface-sterilized seeds were plated on modified Nash-Snyder medium and incubated at 23 ± 2°C for 7 days. Fusarium isolates were single-spored and identified by morphological characteristics on carnation leaf agar (CLA) and potato dextrose agar (PDA) (3). From 276 seedborne Fusarium isolates, six were identified as F. thapsinum (2). On CLA, F. thapsinum isolates produced abundant mycelium and numerous chains of non-septate microconidia produced from monophialides. Microconidia were club-shaped and some were napiform. No chlamysdospores were found. On PDA, three of the isolates presented characteristic dark yellow pigmentation and three were light violet. Confirmation of the isolates to species was based on sequencing of an elongation factor gene (EF1-α) segment using primers EF1 and EF2 and the beta-tubulin gene using primers Beta1 and Beta2 (1). Sequence results (~680 bp, EF primers; ~600 bp, beta-tubulin primers) were confirmed by using the FUSARIUM-ID database (1). All isolates matched F. thapsinum for both genes sequenced (Accession No. FD01177) at 99% identity. Koch's postulates were completed for two isolates of F. thapsinum under greenhouse conditions. Soybean seeds (Asgrow AG3039) were imbibed with 2.5 × 105 conidia ml−1 for 48 h. After inoculation, seeds were dried for 48 h at RT. One isolate each of F. equiseti and F. oxysporum were used as the non-pathogenic and pathogenic inoculation controls, respectively. In addition, non-inoculated seeds and seeds imbibed in sterile distilled water (mock) were also used. Twenty-five seeds from each treatment were planted in pots (500 ml) with autoclaved soil and vermiculite (1:1). The experiment was a completely randomized design with three replicates (pots) per isolate. The entire experiment was repeated three times. After 21 days, aggressiveness of both F. thapsinum isolates was assessed using initial stand (%), final stand (%), and seed mortality (% of non-germinated seeds). Both seedborne F. thapsinum isolates caused reduced emergence and final stand, and increased seedling mortality when compared to the non-inoculated and F. equiseti controls (P< 0.0001). No significant difference was observed between F. thapsinum isolates and F. oxysporum. F. thapsinum isolates were re-isolated from wilted seedlings and non-germinated seeds, but not from the control treatments. Typically, F. thapsinum is considered a pathogen of sorghum, but it has also been recovered from bananas, peanuts, maize, and native grasses (3). However, its presence on soybean plant tissues and its pathogenicity has never been reported. To our knowledge, this is the first report of seedborne F. thapsinum and its pathogenicity on soybean in the United States. References: (1) D. M. Geiser et al. Eur. J. Plant Pathol. 110:473, 2004. (2) C. J. R. Klittich et al. Mycologia 89:644, 1997. (3) J. F. Leslie and B. A. Summerell. The Fusarium Laboratory Manual. Blackwell Publishing, Oxford, UK, 2006.

scholarly journals Identification of Leptosphaeria maculans Pathogenicity Group 4 Causing Blackleg on Winter Canola in Oklahoma

Plant Disease ◽  
2011 ◽  
Vol 95 (5) ◽  
pp. 614-614 ◽  
Author(s):  
L. E. del Río Mendoza ◽  
A. Nepal ◽  
J. M. Bjerke ◽  
M. Boyles ◽  
T. Peeper
Keyword(s):  
Leptosphaeria Maculans ◽  
Morphological Characteristics ◽  
The Other ◽  
Distilled Water ◽  
Brassica Napus L ◽  
Winter Canola ◽  
Group 4 ◽  
Pathogenicity Group ◽  
Garfield County ◽  
Relative Prevalence

Winter canola (Brassica napus L.) is a relatively new crop to Oklahoma and other southern U.S. states where it is considered a desirable rotation crop with wheat. In 2009, approximately 15,000 ha of winter canola were harvested in Oklahoma (3); that area is expected to almost double in 2010. Blackleg, a potentially devastating canola disease, was detected in Oklahoma in 2009. Blackleg is caused by Leptosphaeria maculans (Desmaz.) Ces. & de Not (anamorph = Phoma lingam (Tode:Fr.) Desmaz.). In early 2010, leaf samples showing typical symptoms of blackleg were collected from four canola fields near the town of Enid in Garfield County, OK. Small portions of infected tissues were surface disinfested in an aqueous solution of NaOCl (0.5% a.i.) for 1 min, rinsed twice in sterile distilled water, and plated on V8 medium. Seven colonies were isolated and when grown in pure culture, all produced 2 × 4.5 μm guttulate, unicellular, hyaline spores in pycnidia that ranged from 200 to 480 μm in diameter. These morphological characteristics correspond with those of P. lingam (1). To verify the pathogenic nature of the isolates and establish the pathogenicity group (PG) to which they belong, a standard inoculation protocol was followed on a set of three differential cultivars, Quinta, Glacier, and Westar (2). Briefly, for each isolate, tiny puncture wounds were made with sterile needles on the cotyledons of six 10-day-old plants of each differential and a 10-μl aliquot of a pycnidiospore suspension (1 × 107 spores ml–1) was deposited on the wounds. Also, a set of differentials were inoculated with distilled water (mock inoculation). Inoculated plants were incubated overnight in a misting chamber at 21°C in the dark and returned the next day to the greenhouse. Disease severity was recorded 10 days after inoculation using a 0 to 9 scale in which 0 to 2 = resistant, 3 to 6 = intermediate, and 7 to 9 = susceptible. This process was repeated three times. Two of the seven isolates evaluated were highly virulent on all three differentials, an indication they belong to pathogenicity group 4 (2). The other five isolates produced small lesions on Westar (resistant reaction) but failed to develop symptoms on the other two differentials. This phenotypic reaction has been associated with strains of PG-1. Mock-inoculated plants did not develop lesions. To our knowledge, this is the first time blackleg isolates from Oklahoma have been identified to the PG level. While this information will assist breeders in the development of both spring and winter canola lines with resistance to blackleg, additional studies are necessary to determine the relative prevalence and diversity of the various PG in Oklahoma. References: (1) G. H. Boerema. Trans. Br. Mycol. Soc. 67:289, 1976. (2) A. Mengistu et al. Plant Dis. 75:1279, 1991. (3) USDA. National Agricultural Statistics Service. Retrieved from http://www.nass.usda.gov/Statistics_by_State/Ag_Overview/ AgOverview_OK.pdf , September 20, 2010.

scholarly journals First Report of Calonectria hongkongensis Causing Fruit Rot of Rambutan (Nephelium lappaceum)

Plant Disease ◽  
2013 ◽  
Vol 97 (8) ◽  
pp. 1117-1117 ◽  
Author(s):  
L. M. Serrato-Diaz ◽  
E. I. Latoni-Brailowsky ◽  
L. I. Rivera-Vargas ◽  
R. Goenaga ◽  
P. W. Crous ◽  
...  
Keyword(s):  
Mycelial Growth ◽  
Elongation Factor ◽  
Type Specimen ◽  
Fruit Rot ◽  
Fluorescent Light ◽  
Mycelium Growth ◽  
Tropical Fruit ◽  
First Report ◽  
Nephelium Lappaceum ◽  
Pure Cultures

Fruit rot of rambutan is a pre- and post-harvest disease problem of rambutan orchards. In 2011, fruit rot was observed at USDA-ARS orchards in Mayaguez, Puerto Rico. Infected fruit were collected and 1 mm2 tissue sections were surface disinfested with 70% ethanol followed by 0.5% sodium hypochlorite. Infected fruit were rinsed with sterile, deionized, double-distilled water and transferred to acidified potato dextrose agar (APDA). Plates were incubated at 25 ± 1°C for 6 days. Three isolates of Calonectria hongkongensis (Cah), CBS134083, CBS134084, and CBS134085, were identified morphologically using taxonomic keys (2,3). In APDA, colonies of Cah produced raw sienna to rust-colored aerial mycelial growth. Conidiophores of Cah had a penicillate arrangement of primary to quaternary branches of 2 to 6 phialides. Conidia (n = 50) were cylindrical, hyaline, 1-septate, rounded at both ends, and 44 to 52 μm × 3.5 to 4.5 μm. Conidiophores produced terminal and lateral stipe extensions with terminal sphaeropedunculate vesicles that were 8 to 12 μm wide. Subglobose to ovoid perithecia, 300 to 500 μm × 200 to 350 μm and orange to red-brown, were produced in groups of 3. Asci were clavate and contained 8 ascospores aggregated at the top of the ascus. Ascospores (n = 50) were hyaline, guttulate, fusoid with rounded ends, straight to curved, 1-septate with constriction at the septum, and 28 to 36 μm × 4 to 7 μm. For molecular identification, the ITS rDNA, fragments of β-tubulin (BT), histone H3 (HIS3), and elongation factor (EF1-α) genes were amplified by PCR, sequenced, and compared using BLASTn with Calonectria spp. submitted to the NCBI GenBank. The sequences of Cah submitted to GenBank include accessions KC342208, KC342206, and KC342207 for ITS; KC342217, KC342215, and KC342216 for BT; KC342211, KC342209, and KC342210 for HIS3; and KC342214, KC342212, and KC342213 for EF1α. The sequences were >99% or identical with the ex-type specimen of Cah CBS 114828 for all genes used. Pathogenicity tests were conducted on 5 healthy superficially sterilized fruits per isolate. Both scalpel-wounded and unwounded fruit tissues were inoculated with 5-mm mycelial disks from 8-day-old pure cultures grown in APDA. Untreated controls were inoculated with APDA disks only. Fruits were kept in a humid chamber for 8 days at 25°C under 12 h of fluorescent light. The test was repeated once. Three days after inoculation (DAI), white mycelial growth was observed on the fruit. Five DAI, the fruit changed color from red to brown and yellowish mycelia colonized 50 to 62% of the fruit surface. Eight DAI, all the fruit turned brown, the mycelium growth covered the entire fruit, and conidiophores were produced on spinterns (hairlike appendages). Fruit rot of spinterns, exocarp (skin), endocarp (aril), and light brown discoloration were observed inside the fruit. Untreated controls showed no symptoms of fruit rot and no fungi were reisolated from tissue. Cah was reisolated from diseased tissue, fulfilling Koch's postulates. Calonectria spp. (or their Cylindrocladium asexual states) have been associated with lychee decline syndrome in North Vietnam (1). Both fruits belong to the Sapindaceae family. To our knowledge, this is the first report of Cah causing fruit rot of rambutan. References: (1) L. M. Coates et al. Diseases of Longan, Lychee and Rambutan. Pages 307-325 in: Diseases of Tropical Fruit Crops. R. C. Ploetz, ed. CABI Publishing, Cambridge, MA, 2003. (2) P. W. Crous. Taxonomy and Pathology of Cylindrocladium (Calonectria) and Allied Genera. APS Press, St Paul, MN, 2002. (3) P. W. Crous, et al. Stud. Mycol. 50:415, 2004.

scholarly journals First Report of Brown Blight Disease Caused by Colletotrichum gloeosporioides on Camellia sinensis in Anhui Province, China

Plant Disease ◽  
2014 ◽  
Vol 98 (2) ◽  
pp. 284-284 ◽  
Author(s):  
M. Guo ◽  
Y. M. Pan ◽  
Y. L. Dai ◽  
Z. M. Gao
Keyword(s):  
Camellia Sinensis ◽  
Colletotrichum Gloeosporioides ◽  
Tea Plant ◽  
Anhui Province ◽  
Molecular Characteristics ◽  
Fluorescent Light ◽  
Distilled Water ◽  
Conidial Suspension ◽  
First Report ◽  
Twig Blight

Yellow Mountain fuzz tip, a cultivar of Camellia sinensis (L.) Kuntze, is commonly grown in the Yellow Mountain region in Anhui Province of China. During 2011 to 2012, leaf and twig blight on tea plants occurred from July to September in growing regions. Symptoms of blight on leaves of infected plants were detected in 30 to 60% of the fields visited and up to 500 ha were affected each year. Symptoms began as small, water-soaked lesions on young leaves and twigs and later became larger, dark brown, necrotic lesions, 1 to 3 mm in diameter on leaves and 2 to 5 mm long on twigs. To determine the causal agent, symptomatic leaf tissue was collected from plants in Gantang and Tangkou townships in September 2012. Small pieces of diseased tea leaves and twigs were surface-disinfested in 2% NaClO for 3 min, rinsed twice in distilled water, plated on potato dextrose agar, and incubated at 28°C for 5 days. Eleven isolates were recovered and all cultures produced white-to-gray fluffy aerial hyphae and were dark on the reverse of the plate. The hyphae were hyaline, branching, and septate. Setae were 2- to 3-septate, dark brown, acicular, and 78.0 to 115.0 μm. Conidiogenous cells were hyaline, short, branchless, cylindrical, and 11.3 to 21.5 × 4.2 to 5.3 μm. Conidia were hyaline, aseptate, guttulate, cylindrical, and 12.5 to 17.3 × 3.9 to 5.8 μm. Appresoria were ovate to obovate, dark brown, and 8.4 to 15.2 × 7.8 to 12.9 μm. DNA was amplified using the rDNA-ITS primer pair ITS4/ITS5 (3), glyceraldehyde-3-phosphate dehydrogenase gene (GAPDH) primer pair GDF/GDR (2) and beta-tubulin 2 gene (Tub2) primer pair Btub2Fd/Btub4Rd (4). Sequences (GenBank Accession Nos. KC913203, KC913204, and KC913205) of the 11 isolates were identical and revealed 100% similarity to the ITS sequence of strain P042 of Colletotrichum gloeosporioides (EF423527), 100% identity to the GAPDH of isolate C07009 of C. gloeosporioides (GU935860), and 99% similarity to Tub2 of isolate 85 of C. gloeosporioides (AJ409292), respectively. Based on the above data, the 11 isolates were identified as C. gloeosporioides (Penz.) Penz. & Sacc. To confirm pathogenicity, Koch's postulate was performed and 4 ml of conidial suspension (1 × 105 conidia/ml) of each of the 11 isolates was sprayed on five leaves and five twigs per plant on four 12-month-old Yellow Mountain fuzz tip plants. Control plants were sprayed with distilled water. The inoculated plants were maintained at 28°C in a greenhouse with constant relative humidity of 90% and a 12-h photoperiod of fluorescent light. Brown necrotic lesions appeared on leaves and twigs after 7 days, while the control plants remained healthy. The experiments were conducted three times and the fungus was recovered and identified as C. gloeosporioides by both morphology and molecular characteristics. Tea plant blight caused by C. gloeosporioides was identified in Brazil (1), but to our knowledge, this is the first report of C. gloeosporioides causing tea leaf and twig blight on Yellow Mountain fuzz tip plants in Anhui Province of China. References: (1) M. A. S. Mendes et al. Page 555 in: Embrapa-SPI/Embrapa-Cenargen, Brasilia, 1998. (2) M. D. Templeton et al. Gene 122:225, 1992. (3) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, 1990. (4) J. H. C. Woudenberg et al. Persoonia 22:56, 2009.

scholarly journals First Report of Phaeoacremonium mortoniae Associated with Grapevine Decline in Iran

Plant Disease ◽  
2011 ◽  
Vol 95 (8) ◽  
pp. 1034-1034 ◽  
Author(s):  
H. Mohammadi
Keyword(s):  
Fungal Pathogens ◽  
Vascular Tissue ◽  
Sodium Hypochlorite Solution ◽  
Malt Extract ◽  
Fars Province ◽  
Distilled Water ◽  
Conidial Suspension ◽  
Single Spore ◽  
First Report ◽  
Grapevine Decline

In July 2009, a survey was conducted in individually owned rooted vineyards in Iran to determine fungal pathogens associated with grapevine decline. Symptoms of grapevine decline such as slow dieback, stunted growth, small chlorotic leaves, and reduced foliage were observed on 7-year-old grapevines (cv. Askari) in Bavanat (Fars Province, southwestern Iran). Internal wood symptoms such as black spots and dark brown-to-black vascular streaking were observed in cross and longitudinal sections of stems and trunks. Wood samples were collected from symptomatic trunks and cordons. The bark of each fragment was removed and 10 thin cross sections (2 to 3 mm thick) were cut from symptomatic vascular tissue of the samples. These disks were immersed in 1.5% sodium hypochlorite solution for 4 min, washed thrice with sterile distilled water, and plated onto malt extract agar (MEA) supplemented with 100 mg liter–1 of streptomycin sulfate. Plates were incubated at 25°C in darkness. All colonies were transferred to potato dextrose agar (PDA) and incubated at 25°C. Five isolates of a Phaeoacremonium sp. were obtained. Single-spore isolates were transferred to PDA, MEA, and oatmeal agar (OA) media and incubated at 25°C for 8 to 16 days in the dark (2). Colonies reached a radius of 9.5 to 12 mm after 8 days of incubation. Colonies were flat and yellowish white on PDA and OA and white-to-pale gray after 16 days of incubation on MEA. Conidiophores were short and unbranched, 14 to 38.5 (23.5) μm long, and often ending in a single terminal phialide. Phialides were terminal or lateral and mostly monophialidic. Conidia were hyaline, oblong to ellipsoidal or reniform, 2 to 6.5 (4.9) μm long, and 1.1 to 1.7 (1.4) μm wide. On the basis of these characteristics, the isolates were identified as Phaeoacremonium mortoniae (1,2). Additionally, identity of the PMH1 isolate was confirmed by sequencing a fragment of the -tubulin gene with primers T1 and Bt2b (GenBank Accession No. JF831449). The sequence of this isolate was identical to the sequence of P. mortoniae (GenBank Accession No. HM116767). Pathogenicity tests were conducted on 2-month-old grapevine seedlings of cv. Askari by watering the roots with 25 ml of a conidial suspension (107 conidia ml–1) harvested from 21-day-old cultures grown on MEA. Controls were inoculated with 25 ml of sterile distilled water. Fifteen replicates were used for each isolate with an equal number of noninoculated plants. All plants were grown under greenhouse conditions (25 to 30°C). Two months after inoculation, inoculated seedlings showed reduced growth, chlorotic leaves, epinasty, severe defoliation, and finally wilting, while control seedlings remained healthy. The fungus was reisolated from internal tissues of the stems of inoculated seedlings. To my knowledge, this is the first report of P. mortoniae causing grapevine decline in Iran. References: (1) M. Groenewald et al. Mycol. Res. 105:651, 2001. (2) L. Mostert et al. Stud. Mycol. 54:1, 2006.

scholarly journals First Report of the Pathogenicity of Rhizoctonia solani on Salvinia molesta and S. minima in Florida

Plant Disease ◽  
2002 ◽  
Vol 86 (7) ◽  
pp. 813-813
Author(s):  
M. B. Rayachhetry ◽  
T. R. Center ◽  
T. D. Center ◽  
P. Tipping ◽  
P. D. Pratt ◽  
...  
Keyword(s):  
Rhizoctonia Solani ◽  
Native Species ◽  
Tap Water ◽  
Tween 80 ◽  
Fluorescent Light ◽  
Distilled Water ◽  
Salvinia Molesta ◽  
Potato Dextrose Broth ◽  
First Report ◽  
Mycelial Suspension

Salvinia molesta Mitchell (giant salvinia) and S. minima Baker (common salvinia) are exotic aquatic ferns that have invaded drainage basins in Texas, Louisiana, Alabama, Arizona, California, Florida, Georgia, Hawaii, Mississippi, North Carolina, and Oklahoma (2). These ferns rapidly colonize bodies of water and form thick mats, displace native species, disrupt recreational activities like boating and fishing, block drainage and irrigation intakes, interfere with electricity generation, and degrade water quality (1). Patches of water-soaked lesions were observed on the pinnules and rachises of screenhouse-grown S. molesta plants in Florida. Mycelia spread centrifugally from these patches and caused diseased plants to disintegrate and sink. Brown-to-black sclerotia were formed on and around the disintegrated plants. A fungus was consistently isolated from symptomatic tissues of S. molesta plants. Seven-day-old cultures turned buff-colored and produced sclerotia on potato dextrose agar, while cultures on water agar were hyaline and produced black sclerotia. Both types of sclerotia were not differentiated into rind and medulla. The mycelia branched at right angles from the main hyphae, were constricted at the base of the angle, and had a septum after the constriction. Vegetative cells were multinucleate. The fungus was identified as Rhizoctonia solani Kühn (3,4). Koch's postulates were performed to confirm pathogenicity on S. molesta and S. minima. Seven-day-old cultures of R. solani that were grown in potato dextrose broth were filtered through four layers of cheesecloth and washed with distilled water. Fourteen grams of the mycelial residue was suspended in 28 ml of distilled water and macerated in a small blender for 30 s to obtain a mycelial suspension. Healthy S. molesta and S. minima plants grown in screenhouse-tanks were immersed in tap water supplemented with 1 drop per 4 liters of surfactant (Tween 80), rinsed thoroughly, and approximately 40 g of the plants was floated in plastic jars (18.5 cm diameter × 7.5 cm high) filled to a depth of 5 cm with tap water. Three jars each of S. molesta and S. minima were misted with 1.5 ml of the mycelial suspension. Individual jars were covered with a clear plastic lid with a 2.5-cm-diameter hole in the center for ventilation. These jars were placed in a growth chamber maintained at 28 (+1)°C and 12-h fluorescent light cycles. Typical water-soaked lesions appeared on pinnules within 3 to 7 days, spread rapidly, and resulted in disintegration of pinnules and rachises. R. solani was consistently reisolated from symptomatic tissues of both Salvinia species. To our knowledge, this is the first report confirming pathogenicity of R. solani on S. molesta and S. minima. This fungus should be further evaluated as a potential mycoherbicide for control of Salvinia species. References: (1) K. L. S. Harley and D. S. Mitchell. J. Aust. Inst. Agric. Sci. 47:67, 1981. (2) C. C. Jacono et al. Castanea 66:214, 2001. (3) B. Sneh et al. Identification of Rhizoctonia Species. The American Phytopathological Society, St. Paul, MN, 1991. (4) C. C. Tu and J. W. Kimbrough. Bot. Gaz. 139:454, 1978.

scholarly journals First Report of Gray Mold Disease of Sponge Gourd (Luffa cylindrica) Caused by Botrytis cinerea in Taiwan

Plant Disease ◽  
2007 ◽  
Vol 91 (9) ◽  
pp. 1199-1199 ◽  
Author(s):  
Y. Ko ◽  
K. S. Yao ◽  
C. Y. Chen ◽  
C. H. Lin
Keyword(s):  
Botrytis Cinerea ◽  
Gray Mold ◽  
Spore Suspension ◽  
Fluorescent Light ◽  
Distilled Water ◽  
Luffa Cylindrica ◽  
First Report ◽  
Sponge Gourd ◽  
Plastic Bag ◽  
Central Taiwan

A disease of sponge gourd (Luffa cylindrica (L.) Roem., family Cucurbitaceae) has become a serious threat to sponge gourd production since 2003 in central Taiwan. Initially, symptoms appear as small, brown spots on the flower petals that spread to the entire flower and cause blossom blight within 2 to 3 days. Subsequently, the pathogen develops abundant mycelium and moves from the petals onto the fruits causing blossom end rot and fruit stem rot. Severely infected fruits become completely rotten and desiccate. Tissues were excised from diseased sponge gourd fruits (sampled from Fongyuan, located at 24.25°N, 120.72°E in Taichung County), immersed in a solution containing 3% sodium hypochlorite and 70% ethanol for 1 min, washed three times with sterile water, and then cultured on potato dextrose agar (PDA) medium. A fungus, identified as Botrytis cinerea, produced abundant mycelium on PDA medium when incubated under constant fluorescent light 185 ± 35 μE·m–2·s–1 at 24°C. The conidia were smooth, hyaline, and globoid or slightly ellipsoid. The conidia measured 9.5 to 19.3 μm (average 13.8 μm) long and 6.0 to 17.8 μm (average 10.1 μm) wide, dimensions that are similar to the descriptions of B. cinerea (11 × 11 to 15 μm) that causes gray mold of strawberry (2). The identity of B. cinerea was also confirmed by the production of numerous black sclerotia on PDA plates incubated either in the dark or under light at 20 to 24°C for 9 to 10 days. Koch's postulates were fulfilled by using 3-day-old mycelial agar discs of the fungus or a spore suspension containing 105 conidia per milliliter of distilled water as inoculum. Shallow (2 × 2 × 2 mm) incisions were made on fresh sponge gourd fruits with a sterile scalpel and inoculated with either a 5-mm mycelial disc or 0.5 ml of the spore suspension. Inoculated areas were covered with moist sterile cotton, and the fruits were enclosed in a plastic bag and incubated at 20 to 24°C for 3 days. Wounded fruits inoculated with PDA discs or sterile distilled water alone served as controls. Pathogenicity tests were performed three times using five fruits in each trial. Symptoms and signs of the disease similar to those described above were observed in all (100%) the inoculated fruits, while no symptoms developed in the control fruits. Reisolation from the inoculated fruits consistently yielded B. cinerea. Reciprocal inoculations on sponge gourd, guava, and strawberry with mycelial discs or spore suspensions of a B. cinerea isolate obtained from sponge gourd, guava, and strawberry showed cross pathogenicity among isolates and hosts. Important groups of plants that are attacked by B. cinerea are vegetables, small berry fruits, ornamentals, and bulbs (1). Though 80 species of host plants, mostly shrubs and nursery plants, were reported to be the host of B. cinerea in Taiwan (3), to our knowledge, this is the first report of gray mold disease affecting sponge gourd in Taiwan. References: (1) G. N. Agrios. Plant Pathology. Academic Press. San Diego, 2005. (2) J. L. Mass, ed. Page 56 in: Compendium of Strawberry Diseases. The American Phytopathological Society. St. Paul, MN, 1984. (3). Y. Ko et al. Plant Prot. Bull. (Taiwan) 37:439, 1995.

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