scholarly journals First Report of Fusarium Wilt on Hebe sp. in Italy and Europe

Plant Disease ◽  
2000 ◽  
Vol 84 (6) ◽  
pp. 705-705 ◽  
Author(s):  
A. Garibaldi ◽  
A. Minuto ◽  
G. Gilardi ◽  
M. L. Gullino
Keyword(s):  
Fusarium Wilt ◽  
Vascular System ◽  
The United States ◽  
Selective Medium ◽  
Artificial Inoculation ◽  
Infested Soil ◽  
Single Spore ◽  
First Report ◽  
Single Spore Isolate ◽  
Whole Plants

Hebe (showy speedwell), an increasingly important crop in the Riviera Ligure (northern Italy), is cultivated in greenhouses and open fields. During summer 1999, a serious wilt of hybrids (Hebe speciosa × H. franciscana cvs. Paula, Linda, and Heidi) grown in plastic pots (14 to 16 cm diameter) in a peat/pomix/clay (70:20:10, vol/vol) substrate was observed. Symptoms appeared on one side of the plant or on a single branch. Affected plants showed only slight yellowing before wilting. Wilting progressed acropetally. Eventually, affected plants were completely wilted, and stems showed dark blue-black necrosis, often covered by mycelia. An intense brown discoloration of the vascular system was evident shortly after the appearance of the first symptoms. In some cases, whole plants suddenly wilted. Infected plants generally were stunted and eventually died. Fusarium oxysporum was isolated consistently from diseased plants on Komada's (1) Fusarium-selective medium. One single-spore isolate of F. oxysporum, freshly isolated from wilted plants, was used for artificial inoculation of healthy plants to complete Koch's postulates. Rooted cuttings were transplanted in soil artificially infested with 1 × 103 CFU/ml of soil. Inoculation was performed on 20 plants belonging to two cultivars (Paula and Heidi). Noninoculated plants of each cultivar served as controls. Plants were maintained in a glasshouse at 25°C. The first symptoms developed 20 days after transplanting in infested soil. Symptoms resulting from artificial inoculation were similar to those observed on naturally infected plants. F. oxysporum was consistently reisolated from inoculated plants. Fusarium wilt of Hebe is favored by temperatures higher than 20°C. Symptoms did not develop on inoculated plants maintained in the open field during the month of October nor in the greenhouse at temperatures lower than 18°C. This is the first report of Fusarium wilt on Hebe sp. in Italy and Europe. A similar wilt on H. buxifolia and other Hebe spp. has been reported by Raabe in the United States (2,3). References: (1) H. Komada. Rev. Plant Prot. Res 8:114, 1975. (2) R. D. Raabe. Phytopathology 47:532, 1957. (3) R. D. Raabe. Plant Dis. 69:450, 1985.

scholarly journals First Report of Fusarium oxysporum on Lettuce in Europe

Plant Disease ◽  
2002 ◽  
Vol 86 (9) ◽  
pp. 1052-1052 ◽  
Author(s):  
A. Garibaldi ◽  
G. Gilardi ◽  
M. L. Gullino
Keyword(s):  
Fusarium Oxysporum ◽  
Vascular System ◽  
The United States ◽  
Selective Medium ◽  
Northern Italy ◽  
Infested Soil ◽  
Pathogenicity Test ◽  
First Report ◽  
Vascular Tissues ◽  
Brown Discoloration

In spring 2001, plants of the lettuce cv. Salad Bowl showing symptoms of a wilt disease were observed in several commercial plastic greenhouses near Bergamo, in northern Italy. Wilted plants were first observed during the spring and summer of 2001 when temperatures were between 26 and 35°C. Symptoms were observed in the same area and the same farms in March 2002, in concomitance with a period of high temperatures. Although the distribution of the disease was generally uniform, symptoms were more severe in the central part of the greenhouses where temperatures were warmest. Symptoms were first observed at thinning, when seedlings (30 days old) appeared wilted. Vascular tissues of affected seedlings appeared red or brown. Affected plants were stunted and developed yellow leaves and brown or black streaks in the vascular system. The vascular streaks in the yellow leaves extended from the crown and were continuous with a red-brown discoloration in the vascular system of the crown and upper taproot. Symptoms were typically not visible on the outside of the crowns or roots. Fusarium oxysporum was consistently and readily isolated from symptomatic vascular tissues on a Fusarium-selective medium (2). Seeds of cv. Salad Bowl were planted in steam-sterilized soil artificially infested with 1 × 104 CFU/g soil of each of two isolates of F. oxysporum obtained from infected plants. Plants grown in noninfested soil served as noninoculated control treatments. Plants (25 per treatment) were grown at 25 to 28°C in growth chambers. Wilt symptoms and vascular discoloration of the roots, crown, and veins developed 20 days after seeding for all plants grown in the infested soil, and F. oxysporum was consistently reisolated from infected plants. The pathogenicity test was conducted twice. To our knowledge, this is the first report of F. oxysporum on lettuce in Europe. A wilt of lettuce attributed to F. oxysporum f. sp. lactucae was reported in Japan in 1967 (3) and in the United States in 1993 (1), in the latter case the incitant organism was described as F. oxysporum f. sp. lactucum. References: (1) J. C. Hubbard and J. S. Gerik. Plant Dis. 77:750, 1993. (2) H. Komada. Rev. Plant Prot. Res. 8:114, 1975. (3) T. Matuo and S. Motohashi. Trans. Mycol. Soc. Jpn. 8:13, 1967.

scholarly journals First Report of Armillaria tabescens Causing Armillaria Root Rot of Pindo Palm in South Carolina

Plant Disease ◽  
2006 ◽  
Vol 90 (8) ◽  
pp. 1106-1106 ◽  
Author(s):  
G. Schnabel ◽  
P. K. Bryson ◽  
M. A. Williamson
Keyword(s):  
South Carolina ◽  
Selective Medium ◽  
Plant Diseases ◽  
Universal Primers ◽  
Its2 Region ◽  
Palm Tree ◽  
Single Spore ◽  
First Report ◽  
Single Spore Isolate ◽  
Palm Trees

A Pindo palm tree (Butia capitata) declined in a commercial landscape setting in Georgetown, SC during June of 2005. In the spring, after looking healthy the previous year, the entire canopy collapsed with leaves attached. The canopy defoliated shortly thereafter. A cross section through primary and secondary roots of the wilting plant revealed necrotic areas with the presence of white mycelial fans. Diseased roots containing mycelial fans were collected and small sections were transferred to benomyl dichloran streptomycin (BDS) selective medium. Fungal cultures grew approximately 1 mm in diameter per day and developed aeriel mycelium first. Later, cultures developed mainly crustose mycelium with some parts being aerial. Ribosomal internal transcribed spacer (ITS) regions 1 and 2 were polymerase chain reaction amplified with universal primers ITS1-F and ITS4 and sequenced (GenBank Accession No. DQ109806). A BLAST search in GenBank of the ITS1-5.8S-ITS2 region identified the pathogen as Armillaria tabescens (Scop.) Emel (synonym Clitocybe tabescens (Fr.) Bres) with 98% sequence homology to A. tabescens single-spore isolate ss23 from South Carolina (Accession No. AY695408). The diploid culture from the roots of the Pindo palm was compatible with haploid tester strains of A. tabescens as indicated by diploidization of the haploid mycelium. The disease has been reported on Pindo palm in Florida (1), but to our knowledge, this is the first report of A. tabescens causing disease on Butia species in South Carolina. Our findings indicate that Pindo palm trees could be at risk for infection and should not be cultivated in soils containing pathogenic Armillaria species. Reference: (1) S. A. Alfieri, Jr. et al. Index of Plant Diseases in Florida (Revised). Fla. Dep. Agric. Consum. Serv. Div. Plant Ind. Bull. 11:389, 1984.

scholarly journals First Report of Fusarium Wilt on Paris Daisy (Argyranthemum[Dendranthema] frutescens)

Plant Disease ◽  
1998 ◽  
Vol 82 (12) ◽  
pp. 1403-1403 ◽  
Author(s):  
A. Garibaldi ◽  
A. Minuto ◽  
M. L. Gullino
Keyword(s):  
Fusarium Oxysporum ◽  
Fusarium Wilt ◽  
Vascular System ◽  
Northern Italy ◽  
Artificial Inoculation ◽  
Rooted Cuttings ◽  
First Report ◽  
Soil Inoculation ◽  
Brown Discoloration ◽  
Dark Blue

Paris daisy (Argyranthemum frutescens) is an economically important crop on the Riviera Ligure (Northern Italy), where approximately 10 million plants per year are produced for export. In September 1997, a serious wilt of plants (cv. Camilla) grown in plastic pots (14 to 18 cm in diameter) was observed. The leaves of the affected plants turned yellow unilaterally and eventually wilted. Both yellowing and wilting progressed acropetally. Eventually, affected plants were completely wilted and the stems showed dark blue-black necrosis. An intense brown discoloration of the vascular system was evident, particularly after yellowing of the foliage was visible. Fusarium oxysporum was consistantly isolated from diseased plants on Komada's medium (1). Two monoconidial isolates of F. oxysporum freshly isolated from A. frutescens wilted plants were used for artificial inoculation of healthy cv. Camilla plants in order to complete Koch's postulates. Rooted cuttings were inoculated by a root dip (for 30 s, with 5 × 107 CFU per ml) and by infesting soil (1 × 103 CFU per ml of soil). Inoculation was carried out on 20 plants belonging to five cultivars. Noninoculated plants of each cultivar served as control. Plants were maintained in a glasshouse at 22 to 23°C. Symptoms developed 13 to 14 days after and were similar to those observed on naturally infected plants. F. oxysporum was consistantly reisolated from artificially inoculated plants. Fusarium wilt of A. frutescens is favored by temperatures higher than 20°C. To our knowledge, this is the first report of Fusarium wilt on A. frutescens. Reference: (1) H. Komada. Rev. Plant Prot. Res. 8:114, 1975.

scholarly journals First Report of Fusarium oxysporum f. sp. palmarum in Texas Causing Fusarium Wilt of Washingtonia robusta

Plant Disease ◽  
2013 ◽  
Vol 97 (11) ◽  
pp. 1511-1511 ◽  
Author(s):  
M. Giesbrecht ◽  
M. McCarthy ◽  
M. L. Elliott ◽  
K. L. Ong
Keyword(s):  
Fusarium Oxysporum ◽  
Fusarium Wilt ◽  
Sequence Similarity ◽  
The United States ◽  
Plant Sample ◽  
Post Inoculation ◽  
Single Spore ◽  
Diagnostic Laboratory ◽  
First Report ◽  
Foliar Tissue

Fusarium wilt of palms occurs worldwide, caused by different Fusarium oxysporum ff. spp. including F. oxysporum f. sp. elaeidis, F. oxysporum f. sp. canariensis, and F. oxysporum f. sp. albedinis (3). Prior to 2010, F. oxysporum f. sp. canariensis was the only palm infecting species known to occur in the United States. In 2010, isolates of F. oxysporum were reported from dying Syagrus romanzoffiana and Washingtonia robusta in Florida. Based on morphological and molecular data, as well as the unique host species affected by the pathogen, this fungus was determined to be a new forma specialis of F. oxysporum, designated f. sp. palmarum (1). The pathogen infects foliar tissue, causing complete necrosis of the crown and leading to tree death within 2 to 3 months. In June 2012, the Texas Plant Disease Diagnostic Laboratory (TPDDL) received a plant sample from a dying W. robusta palm, exhibiting reddish-brown stripes on the petiole with chlorotic and necrotic leaves, from an established palm in the landscape from Harris County, Texas. Fungal cultures were obtained from symptomatic foliar tissue and identified as F. oxysporum based on morphology. Microconidia were oval to reniform, 1- to 2-septate, measuring 5 to 18 × 2.5 to 5 μm. Phialides were short with microconidia produced in false heads. Macroconidia were curved and slender with a foot-shaped basal cell, usually 3-septate, and 22 to 37 × 2.5 to 5 μm. Chlamydospores were roundish and ranged from 7 to 13 μm in diameter. Fungal colonies had white to purple mycelia when grown on potato dextrose agar. DNA from a single spore culture was extracted, amplified by PCR using primers corresponding to a segment of the translation elongation factor 1α (EF-1α) gene, and the PCR product sequenced (2). Using the sequence alignment tool (BLASTn) in GenBank, the TPDDL's sequence (GenBank Accession No. KC897693) was aligned with EF-1α regions from F. oxysporum f. sp. palmarum isolates previously entered into the database ([1]; accessions GQ154455[=NRRL53544] and GQ154456[=NRRL46589]), revealing 100% homology between the isolates. Based on host source and sequence similarity, the fungus was tentatively identified as F. oxysporum f. sp. palmarum. Pathogenicity tests were performed on three leaf seedlings of W. robusta and W. filifera. Fifteen plants of each species were inoculated with the suspect isolate (designated KB2012) and 10 control plants were mock-inoculated as described by (1). Plants were grown in a greenhouse for 8 weeks post-inoculation. During this time, 83% of inoculated plants developed foliar lesions and died or severely declined, and all control plants remained healthy. F. oxysporum was recovered in culture from 100% of the symptomatic plants. DNA was extracted from fungal cultures, and EF-1α was amplified by PCR and sequenced, as described above. The amplicon was determined to share 100% homology with known F. oxysporum f. sp. palmarum isolates, confirming this fungus as the cause of disease in W. robusta. This is the first report of this pathogen in Texas, as well as the first report outside of Florida. This is also the first documentation of W. filifera as a host of this pathogen. References: (1) M. L. Elliott et al. Plant Dis. 94:31, 2010. (2) D. M. Geiser et al. Eur. J. Plant Pathol. 110:473, 2004. (3) G. W. Simone. Pages 17-19 in: Compendium of Ornamental Palm Diseases and Disorders, M. L. Elliott et al., eds. The American Phytopathological Society, St. Paul, MN, 2004.

scholarly journals First Report of Fusarium oxysporum Causing Wilt on Jade Plant (Crassula ovata) in Italy

Plant Disease ◽  
2011 ◽  
Vol 95 (9) ◽  
pp. 1191-1191 ◽  
Author(s):  
A. Garibaldi ◽  
D. Bertetti ◽  
P. Pensa ◽  
A. Poli ◽  
M. L. Gullino
Keyword(s):  
Fusarium Oxysporum ◽  
Vascular System ◽  
Apical Cell ◽  
Aerial Mycelium ◽  
Selective Medium ◽  
Fluorescent Light ◽  
Pathogenicity Test ◽  
Conidial Suspension ◽  
Single Spore ◽  
First Report

During summer 2010, symptoms of a wilt disease were observed in a commercial farm in northern Italy on Crassula ovata (jade plant). First symptoms consisted of chlorosis and premature drop of still turgid leaves. As the disease progressed, leaves turned yellow and wilted before dropping off and the stem wilted, bent, and eventually rotted starting from the base. In some cases, the stem broke or the basal portion of the leaf rotted. Brown discolorations were observed in the vascular system. Of 10,000 plants, 65% (cv. Mini) and 5% of 600 plants (cv. Magical Tree) were affected. Premature dropping of leaves was more frequent on cv. Magical Tree. Using the Komada's Fusarium-selective medium, a fungus was consistently and readily isolated from symptomatic vascular tissues of plants belonging to both cultivars. Isolates obtained from both cultivars were purified, subcultured on potato dextrose agar (PDA), and single-spore cultures were obtained. On PDA, both isolates produced pale violet, abundant, aerial mycelium, felted in old cultures, with purple pigments in the agar. The isolates were grown on Spezieller Nährstoffarmer agar for characterization of macroconidia and microconidia (1). Both isolates produced sparse, 3 to 5 septate, nearly straight macroconidia measuring 30 to 56 × 3 to 5 (average 40 × 4) μm with a short apical cell and a foot-shaped basal cell. Sporodochia were not observed. Unicellular, oval-elliptical microconidia measuring 5 to 13 × 3 to 4 (average 8 × 3) μm were produced on short monophialides. Chlamydospores were abundant, single and sometime in pairs, terminal and intercalary, rough walled, and measured 6 to 9 μm. Such characteristics are typical of Fusarium oxysporum (3). The ITS region (internal transcribed spacer) of rDNA was amplified with primers ITS1/ITS4 (4) and sequenced. BLASTn analysis of an isolate from C. ovata cv. Mini (515 bp, Accession No. HQ682196) and C. ovata cv. Magical Tree (509 bp, Accession No. HQ682197) showed an E-value of 0.0 with F. oxysporum. For these sequences, pairwise alignment of EMBOSS (E.B.I. - The European Bioinformatics Institute) revealed identity and similarity of 99.0%. To confirm pathogenicity, tests were conducted on 5-month-old plants of cvs. Mini and Magical Tree. Plants (three per treatment) were inoculated by dipping roots in a 1 × 106 CFU/ml conidial suspension of the two isolates of F. oxysporum prepared from 10-day-old cultures grown on casein liquid medium (2), shaken (90 rpm) for 10 days at 24°C ± 1 (12-h fluorescent light, 12-h dark). Inoculated plants were transplanted into pots filled with steamed mix (sphagnum peat/perlite/pine bark/clay; 50:20:20:10) and maintained in a plant growth chamber at 25 ± 1°C under a regimen of 12 h per day of fluorescent light. Inoculated plants belonging to both cultivars showed typical first symptoms of Fusarium wilt after 13 days. In the following days, leaves dropped, stems wilted, and plants died. Noninoculated plants remained healthy. F. oxysporum was reisolated from inoculated plants. The pathogenicity test was conducted twice. This is, to our knowledge, the first report of F. oxysporum on C. ovata in Italy or worldwide. References: (1) J. F. Leslie and B. A. Summerell. The Fusarium Laboratory Manual. Blackwell Professional, Ames, IA, 2006. (2) A. Minuto et al. Phytoparasitica 36:294, 2008. (3) B. A. Summerell et al. Plant Dis. 87:117, 2003. (4) T. J. White et al. PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al., eds. Academic Press, San Diego, 1990.

scholarly journals First Report of Armillaria mellea on a Fern from Italy

Plant Disease ◽  
2000 ◽  
Vol 84 (5) ◽  
pp. 592-592 ◽  
Author(s):  
S. Grasso ◽  
A. Pane ◽  
S. O. Cacciola
Keyword(s):  
Pure Culture ◽  
Late Summer ◽  
The United States ◽  
Selective Medium ◽  
Mount Etna ◽  
Washington Dc ◽  
First Report ◽  
Reference Isolate ◽  
Ornamental Foliage Plants ◽  
Electrophoretic Patterns

Several perennial species of rhizomatous herbaceous ferns are cultivated as ornamental foliage plants. During late summer 1999, in a garden at the foot of Mount Etna, eastern Sicily (Italy), we noted a fern hedge showing patches of withered or stunted plants. The fern was identified as Cyrtomium falcatum (L.f.) C. Presl. (=Polystichum falcatum (L.f.) Diels), a house holly fern or Japanese holly fern, which is an ornamental fern native to East and South Asia. Other woody plants in the immediate vicinity had died over the last few years, including apricot and cedar trees whose stumps had not been removed. A close examination of uprooted ferns revealed the presence of creamy white fan-shaped mycelial mats with an odor typical of Armillaria species that were intermixed with the felt-like tangle formed by the rhizomes and roots of the ferns. In autumn, clumps of honey mushrooms with an annulus grew around patches of the withered fern hedge and in other parts of the same garden. The spore print of the basidiocarp was light cream. Basidiospores (8 to 9 × 5 to 6.5 µm) examined under a microscope were hyaline and apiculate. The fungus was isolated in pure culture from infected rhizomes with the selective medium of Kulman and Hendrix (3). In pure culture on 2% malt agar, the fungus formed ribbon-shaped, contorted, fast-growing rhizomorphs that branched profusely. Mycelial proteins of the isolate were analyzed by both polyacrylamide slab gel and starch gel electrophoreses, as described by Bragaloni et al. (1). The electrophoretic patterns of five isozymes (esterase, glutamic oxalacetic transaminase, phospho-glucomutase, alcohol dehydrogenase, and polygalacturonase) of the isolate from fern were identical to those of the reference isolate of A. mellea (Vahl:Fr.) Kumm. from grapevine. Conversely, the patterns were clearly distinct from those of reference isolates from other species, including A. ostoyae (Romagnesi) Herink, A. bulbosa (Barla) Kile et Watling, and A. cepistipes Velenovsky. Thus, on the basis of cultural, morphological, and biochemical characteristics, the species infecting the fern was identified as A. mellea. This pathogen, very common and widespread on wooded or previously wooded sites, has an extremely wide host range, encompassing both woody and herbaceous plants (2,4). However, this is the first report of A. mellea on a fern in Italy. References: (1) M. Bragaloni and N. Anselmi. Eur. J. For. Pathol. 27:147, 1997. (2) D. F. Farr et al. 1989. Fungi on Plants and Plants Products in the United States. The American Phytopathological Society, St. Paul, MN. (3) E. G. Kulman and F. F. Hendrix. Phytopathology 52:1310, 1962. (4) C. G. Shaw and G. A. Kile. 1991 Armillaria root disease. Agric. Handb. No 691. U.S. Department of Agriculture Forest Service, Washington, DC.

scholarly journals First Report of Alternaria Leaf Spot of Banana Caused by Alternaria alternata in the United States

Plant Disease ◽  
2013 ◽  
Vol 97 (8) ◽  
pp. 1116-1116 ◽  
Author(s):  
V. Parkunan ◽  
S. Li ◽  
E. G. Fonsah ◽  
P. Ji
Keyword(s):  
United States ◽  
Alternaria Alternata ◽  
Leaf Spot ◽  
Morphological Characteristics ◽  
The United States ◽  
Its Sequencing ◽  
Single Spore ◽  
First Report ◽  
Alternaria Leaf Spot ◽  
Leaf Spots

Research efforts were initiated in 2003 to identify and introduce banana (Musa spp.) cultivars suitable for production in Georgia (1). Selected cultivars have been evaluated since 2009 in Tifton Banana Garden, Tifton, GA, comprising of cold hardy, short cycle, and ornamental types. In spring and summer of 2012, 7 out of 13 cultivars (African Red, Blue Torres Island, Cacambou, Chinese Cavendish, Novaria, Raja Puri, and Veinte Cohol) showed tiny, oval (0.5 to 1.0 mm long and 0.3 to 0.9 mm wide), light to dark brown spots on the adaxial surface of the leaves. Spots were more concentrated along the midrib than the rest of the leaf and occurred on all except the newly emerged leaves. Leaf spots did not expand much in size, but the numbers approximately doubled during the season. Disease incidences on the seven cultivars ranged from 10 to 63% (10% on Blue Torres Island and 63% on Novaria), with an average of 35% when a total of 52 plants were evaluated. Six cultivars including Belle, Ice Cream, Dwarf Namwah, Kandarian, Praying Hands, and Saba did not show any spots. Tissue from infected leaves of the seven cultivars were surface sterilized with 0.5% NaOCl, plated onto potato dextrose agar (PDA) media and incubated at 25°C in the dark for 5 days. The plates were then incubated at room temperature (23 ± 2°C) under a 12-hour photoperiod for 3 days. Grayish black colonies developed from all the samples, which were further identified as Alternaria spp. based on the dark, brown, obclavate to obpyriform catenulate conidia with longitudinal and transverse septa tapering to a prominent beak attached in chains on a simple and short conidiophore (2). Conidia were 23 to 73 μm long and 15 to 35 μm wide, with a beak length of 5 to 10 μm, and had 3 to 6 transverse and 0 to 5 longitudinal septa. Single spore cultures of four isolates from four different cultivars were obtained and genomic DNA was extracted and the internal transcribed spacer (ITS1-5.8S-ITS2) regions of rDNA (562 bp) were amplified and sequenced with primers ITS1 and ITS4. MegaBLAST analysis of the four sequences showed that they were 100% identical to two Alternaria alternata isolates (GQ916545 and GQ169766). ITS sequence of a representative isolate VCT1FT1 from cv. Veinte Cohol was submitted to GenBank (JX985742). Pathogenicity assay was conducted using 1-month-old banana plants (cv. Veinte Cohol) grown in pots under greenhouse conditions (25 to 27°C). Three plants were spray inoculated with the isolate VCT1FT1 (100 ml suspension per plant containing 105 spores per ml) and incubated under 100% humidity for 2 days and then kept in the greenhouse. Three plants sprayed with water were used as a control. Leaf spots identical to those observed in the field were developed in a week on the inoculated plants but not on the non-inoculated control. The fungus was reisolated from the inoculated plants and the identity was confirmed by morphological characteristics and ITS sequencing. To our knowledge, this is the first report of Alternaria leaf spot caused by A. alternata on banana in the United States. Occurrence of the disease on some banana cultivars in Georgia provides useful information to potential producers, and the cultivars that were observed to be resistant to the disease may be more suitable for production. References: (1) E. G. Fonsah et al. J. Food Distrib. Res. 37:2, 2006. (2) E. G. Simmons. Alternaria: An identification manual. CBS Fungal Biodiversity Center, Utrecht, Netherlands, 2007.

scholarly journals First Report of Phytophthora hydropathica Causing Wilting and Shoot Dieback on Viburnum in Italy

Plant Disease ◽  
2014 ◽  
Vol 98 (11) ◽  
pp. 1582-1582 ◽  
Author(s):  
S. Vitale ◽  
L. Luongo ◽  
M. Galli ◽  
A. Belisario
Keyword(s):  
Natural Infection ◽  
Morphological Characteristics ◽  
Leaf Tissue ◽  
The United States ◽  
Selective Medium ◽  
Phytophthora Species ◽  
Phytophthora Ramorum ◽  
Width Ratio ◽  
Morphological Identification ◽  
First Report

The genus Viburnum comprises over 150 species of shrubs and small trees such as Laurustinus (Viburnum tinus L.), which is one of the most widely used ornamental plants in private and public gardens. Furthermore, it commonly forms stands of natural woodland in the Mediterranean area. In autumn 2012, a survey was conducted to determine the presence of Phytophthora ramorum on Viburnum in commercial nurseries in the Latium region where wilting, dieback, and death of twigs were observed on 30% of the Laurustinus plants. A Phytophthora species was consistently recovered from soil rich in feeder roots from potted Laurustinus plants showing symptoms. Soil samples were baited with rhododendron leaves. Small pieces of leaf tissue cut from the margin of lesions were plated on P5ARPH selective medium (4). Pure cultures, obtained by single-hypha transfers on potato dextrose agar (PDA), were petaloid. Sporangia formation was induced on pepper seeds (3). Sporangia were almost spherical, ovoid or obpyriform, non-papillate and non-caducous, measuring 36.6 to 71.4 × 33.4 to 48.3 μm (average 53.3 × 37.4 μm) with a length/width ratio of 1.4. Chlamydospores were terminal and 25.2 to 37.9 μm in diameter. Isolates were considered heterothallic because they did not produce gametangia in culture or on the host. All isolates examined had 30 to 35°C as optimum temperatures. Based on these morphological characteristics, the isolates were identified as Phytophthora hydropathica (2). Morphological identification was confirmed by internal transcribed spacer (ITS), and mitochondrial partial cytochrome oxidase subunit 2 (CoxII) with BLAST analysis in the NCBI database revealing 99% identity with ITS and 100% identity with CoxII. The sequences of the three isolates AB234, AB235, and AB236 were deposited in European Nucleotide Archive (ENA) with the accession nos. HG934148, HG934149, and HG934150 for ITS and HG934151, HG934152, and HG934153 for CoxII, respectively. Pathogenicity tests were conducted in the greenhouse on a total of six 1-year-old shoots cut from V. tinus plants with two inoculation points each. Mycelial plugs cut from the margins of actively growing 8-day-old cultures on PDA were inserted through the epidermis into the phloem. Controls were treated as described above except that sterile PDA plugs replaced the inoculum. Shoots were incubated in test tubes with sterile water in the dark at 24 ± 2°C. After 2 weeks, lesions were evident at the inoculation points and symptoms were similar to those caused by natural infection. P. hydropathica was consistently re-isolated from the margin of lesions, while controls remained symptomless. In the United States in 2008, P. hydropathica was described as spreading from irrigation water to Rhododendron catawbiense and Kalmia latifolia (2). This pathogen can also attack several other horticultural crops (1), but to our knowledge, this is the first report of P. hydropathica causing wilting and shoot dieback on V. tinus. References: (1) C. X. Hong et al. Plant Dis. 92:1201, 2008. (2) C. X. Hong et al. Plant Pathol. 59:913, 2010. (3) E. Ilieva et al. Eur. J. Plant Path. 101:623, 1995. (4) S. N. Jeffers and S. B. Martin. Plant Dis. 70:1038, 1986.

scholarly journals Suppression of Fusarium Wilt Caused by Fusarium oxysporum f. sp. niveum Race 2 on Grafted Triploid Watermelon

Plant Disease ◽  
2014 ◽  
Vol 98 (10) ◽  
pp. 1326-1332 ◽  
Author(s):  
Anthony P. Keinath ◽  
Richard L. Hassell
Keyword(s):  
Fusarium Oxysporum ◽  
Fusarium Wilt ◽  
Disease Incidence ◽  
The United States ◽  
Infested Soil ◽  
Marketable Yield ◽  
Race 1 ◽  
Susceptible Control ◽  
Triploid Watermelon ◽  
Race 2

Fusarium wilt of watermelon, caused by the soilborne fungal pathogen Fusarium oxysporum f. sp. niveum race 2, is a serious, widespread disease present in major watermelon-growing regions of the United States and other countries. ‘Fascination,’ a high yielding triploid resistant to race 1, is grown in southeastern states in fields that contain a mixture of races 1 and 2. There is some benefit to using cultivars with race 1 resistance in such fields, even though Fascination is susceptible to Fusarium wilt caused by race 2. Experiments in 2012 and 2013 were done in fields infested primarily with race 2 and a mixture of races 1 and 2, respectively. Fascination was grafted onto four rootstock cultivars: bottle gourd (Lagenaria siceraria) ‘Macis’ and ‘Emphasis’ and interspecific hybrid squash (Cucurbita maxima× C. moschata) ‘Strong Tosa’ and ‘Carnivor.’ Nongrafted and self-grafted Fascination were used as susceptible control treatments. In both experiments, mean incidence of plants with symptoms of Fusarium wilt was ≥52% in the susceptible control treatments and ≤6% on the grafted rootstocks. Disease incidence did not differ between rootstock species or cultivars. In both years, Fascination grafted onto Strong Tosa and Macis produced more marketable-sized fruit than the susceptible control treatments. Grafted Emphasis and Carnivor also produced more fruit than the control treatments in 2012. The cucurbit rootstocks suppressed Fusarium wilt caused by race 2 and increased marketable yield of triploid watermelon grown in infested soil.

scholarly journals First Report of Alternaria tenuissima Causing Postharvest Decay on Apple Fruit from Cold Storage in the United States

Plant Disease ◽  
2014 ◽  
Vol 98 (5) ◽  
pp. 690-690 ◽  
Author(s):  
L. P. Kou ◽  
V. L. Gaskins ◽  
Y. G. Luo ◽  
W. M. Jurick
Keyword(s):  
United States ◽  
South Africa ◽  
Cold Storage ◽  
Fungal Pathogens ◽  
The United States ◽  
Apple Fruit ◽  
Conidial Suspension ◽  
Single Spore ◽  
Alternaria Tenuissima ◽  
First Report

Apples are grown and stored for 9 to 12 months under controlled atmosphere conditions in the United States. During storage, apples are susceptible to various fungal pathogens, including several Alternaria species (2). Alternaria tenuissima (Nees) Wiltshire causes dry core rot (DCR) on apples during storage and has recently occurred in South Africa (1). Losses range widely, but typically occur at 6 to 8% annually due to this disease (2). In February 2013, ‘Nittany’ apples with round, dark-colored, dry, spongy lesions were obtained from wooden bins in a commercial cold storage facility located in Pennsylvania. Symptomatic fruits were transported to the lab, rinsed with sterile water, and the lesions were sprayed with 70% ethanol until runoff and wiped dry. The skin was aseptically removed with a scalpel, and asymptomatic tissue was placed onto potato dextrose agar (PDA) and incubated at 25°C. Two single-spore isolates were propagated on PDA and permanent cultures were maintained as slants and stored at 4°C. The fungus produced a cottony white mycelium that turned olive-green to brown with abundant aerial hyphae and had a dark brown to black reverse on PDA. Isolates were identified as Alternaria based on conidial morphology as the spores were slightly melanized and obclavate to obpyriform catentulate with longitudinal and transverse septa attached in unbranched chains on simple short conidiophores. Conidia ranged from 10 to 70 μm long (mean 27.7 μm) and 5 to 15 μm wide (mean 5.25 μm) (n = 50) with 1 to 6 transverse and 0 to 2 longitudinal septa. Conidial beaks, when present, were short (5 μm or less) and tapered. Mycelial genomic DNA was extracted, and a portion of the histone gene (357 bp) was amplified via gene specific primers (Alt-His3-F/R) using conventional PCR (Jurick II, unpublished). The forward and reverse sequences were assembled into a consensus representing 2× coverage and MegaBLAST analysis showed that both isolates were 100% identical to Alternaria tenuissima isolates including CR27 (GenBank Accession No. AF404622.1) that caused DCR on apple fruit during storage in South Africa. Koch's postulates were conducted using 10 organic ‘Gala’ apple fruit that were surface sterilized with soap and water, sprayed with 70% ethanol, and wiped dry. The fruit were aseptically wounded with a nail to a 3 mm depth, inoculated with 50 μl of a conidial suspension (1 × 104 conidia/ml), and stored at 25°C in 80 count boxes on paper trays for 21 days. Mean lesion diameters on inoculated ‘Gala’ apple fruit were 19.1 mm (±7.4), water only controls (n = 10 fruit) were symptomless, and the experiment was repeated. Symptoms observed on artificially inoculated ‘Gala’ apple fruit were similar to the decay observed on ‘Nittany’ apples from cold storage. Based on our findings, it is possible that A. tenuissima can cause decay that originates from wounded tissue in addition to dry core rot, which has been reported (1). Since A. tenuissima produces potent mycotoxins, even low levels of the pathogen could pose a health problem for contaminated fruit destined for processing and may impact export to other countries. To the best of our knowledge, this is the first report of alternaria rot caused by A. tenuissima on apple fruit from cold storage in the United States. References: (1) J. C. Combrink et al. Decid. Fruit Grow. 34:88, 1984. (2) M. Serdani et al. Mycol. Res. 106:562, 2002. (3) E. E. Stinson et al. J. Agric. Food Chem. 28:960, 1980.

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