First Report of Fusarium Wilt of Coreopsis verticillata ‘Moonbeam’ Caused by Fusarium oxysporum in a Midwestern Nursery

Disease symptoms were observed in a commercial nursery in the midwest on Coreopsis verticillata ‘Moonbeam’ during the summer of 2006. Plants in a roughly circular area in one field showed foliar necrosis, stem basal cankers, root rot, and eventually plant death. Vascular discoloration was noted in stems of affected plants. Sporulation typical of Fusarium oxysporum was observed on the surface of cankers. Five isolates of F. oxysporum (KR1, KR2, KR4, MDU, and MDL) were taxonomically identified from monosporic cultures obtained from surface-disinfested stems and roots. All five isolates were vegetatively compatible with each other. Two methods of inoculation were used. Method one (conidial drench) involved pouring 100 ml of conidial suspension (106 conidia per ml) into 10-cm pots containing one healthy 2-month-old division of the same cultivar that was obtained from a different nursery. Method two (millet infestation) involved mixing autoclaved millet seed that had been colonized by each isolate into potting mix (2.5 g/L of mix) prior to transplanting. Four plants were tested per isolate per method and controls received distilled water or autoclaved millet. After 3 months, only two isolates (KR1 and KR2) inoculated by conidial drench caused root rot, whereas all isolates inoculated by millet infestation caused wilt, root rot, and vascular discoloration, and all inoculated plants died after 3.5 months Controls remained healthy. The fungus was recovered and was vegetatively compatible with the original F. oxysporum isolates. The tef-α gene from two F. oxysporum isolates was sequenced, submitted to the Blast ID search at Pennsylvania State University (1), and found to belong to the F. oxysporum species complex. Two isolates (KR1 and KR 2) have been deposited at the Fusarium Research Center at Pennsylvania State University under deposition numbers O-2437 and O-2438. Because of the popularity of this coreopsis cultivar, this disease has the potential to cause significant economic loss in nurseries and landscape businesses. The affected nursery, however, has taken all precautions to avoid disseminating the pathogen. Reference: (1) D. M. Geiser et al. Eur. J. Plant Pathol. 110:473, 2004.

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Fusarium moniliforme and F. proliferatum Isolated from Crown and Root Rot of Asparagus and Their Association with Asparagus Decline in Argentina

Plant Disease ◽

10.1094/pdis.1998.82.12.1405a ◽

1998 ◽

Vol 82 (12) ◽

pp. 1405-1405 ◽

Cited By ~ 5

Author(s):

G. Lori ◽

S. Wolcan ◽

C. Mónaco

Keyword(s):

Root Rot ◽

Fusarium Moniliforme ◽

Fusarium Species ◽

Conidial Suspension ◽

State University ◽

Ear Rot ◽

Pennsylvania State University ◽

Close Proximity ◽

Crown And Root Rot ◽

Stem Lesions

During the summer of 1995-1996, an 80-ha field of 6-year-old asparagus plants (cv. UC 72) in Saladillo (Province of Buenos Aires) was affected by a decline syndrome (1). The plants showed a decline in vigor and approximately 60 to 70% of the plants died. The symptomatic plants were chlorotic, stunted, with stem lesions and crown and root rot. Fusarium moniliforme and F. proliferatum were isolated from vascular and epidermal tissues of roots, crowns, and stems. Identification of Fusarium to species was made by examining conidiogenous cells from colonies cultured on KCl medium (2). Microconidia were born in long and short chains and false heads. The isolates were identified based on the the presence of polyphialides in F. proliferatum and their absence in F. moniliforme, which produces monophialides only (2). In two separate trials, asparagus seeds (cv. UC 72) were surface sterilized and placed in steamed soil infested with a conidial suspension of each species. The viable propagules in the soil (CFU per g) were estimated by soil plate dilutions on Nash & Snyder-PCNB (pentachloronitrobenzene) medium. The F. moniliforme and F. proliferatum soil densities were 19.2 × 103 and 23 × 103 CFU per g of soil, respectively. The pots were placed in the greenhouse on different benches to avoid cross-contamination. After 4 months, inoculated plants showed root and crown discoloration. F. moniliforme and F. proliferatum were reisolated (64 and 75%, respectively) from discolored portions of internal and external root and crown tissues. Although the stems did not show symptoms, F. moniliforme and F. proliferatum were also recovered (27 and 38%, respectively) from asymptomatic tissues. Six months after inoculation the plants developed chlorotic symptoms with crown and root rot, and then wilted. F. moniliforme and F. proliferatum were reisolated from root systems, crowns, and stems of all inoculated plants. F. moniliforme and F. proliferatum are involved in corn stalk and ear rot in Argentina. Corn and asparagus are frequently grown in close proximity and often follow one another at a particular site. Airborne and soil debris carrying F. moniliforme and F proliferatum from corn may be an additional source of inoculum for asparagus in Argentina. The results indicate that the presence of F. moniliforme and F. proliferatum is a factor that contributes to asparagus decline in Argentina. References: (1) W. H. Elmer et al. Plant Dis. 80:117, 1996. (2) P. E. Nelson et al. Fusarium Species: An Illustrated Manual for Identification. Pennsylvania State University, University Park, 1983.

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First Report of Fusarium oxysporum f. sp. lycopersici Race 3 and F. oxysporum f. sp. radicis-lycopersici in Tomatoes in the Azapa Valley of Chile

Plant Disease ◽

10.1094/pdis-03-14-0303-pdn ◽

2014 ◽

Vol 98 (10) ◽

pp. 1432-1432 ◽

Cited By ~ 4

Author(s):

G. Sepúlveda-Chavera ◽

W. Huanca ◽

R. Salvatierra-Martínez ◽

B. A. Latorre

Keyword(s):

Fusarium Oxysporum ◽

Tap Water ◽

Universal Primers ◽

Conidial Suspension ◽

Laboratory Manual ◽

First Report ◽

Solanum Lycopersicum L ◽

Vascular Discoloration ◽

Seedling Roots ◽

Pcr Assays

Tomato (Solanum lycopersicum L.) is an important crop in the Azapa Valley (18°35′ S, 69°30′ W) in northern Chile, with approximately 600 ha of fresh tomatoes under greenhouses. Cultivars resistant to Fusarium oxysporum f. sp. lycopersici (FOL) races 1 and 2 are mainly used. However, in 2012 and 2013, Fusarium wilt incidence was 2 to 3%. Symptoms appeared unilaterally and consisted of yellowing, leaf wilting of lower leaves, dark brown vascular discoloration, and plant death. The aim of this study was to determine the causal agent of tomato wilt in seven tomato greenhouses in the Azapa Valley. Stem samples (5 × 5 mm) were obtained 10 cm of the stem base from wilted tomatoes ‘Naomi’ (BIOAMERICA S.A., Chile) or from Maxifort tomato rootstock (De Ruiter Seed, USA), both FOL resistant to races 1 and 2. Samples were washed with tap water, surface sterilized with 1% NaClO for 3 min, and incubated on sterile moist paper towels in petri plates for 5 days at 22°C. Mycelial fragments from white colonies, emerging from diseased tissues, were transferred to PDA. Six Fusarium isolates were characterized by the presence of hyaline macroconidia, mostly 3 to 5 septate, slightly curved (19.2 to 32.1 × 2.9 to 4.5 μm) and single-celled, oval to elongated microconidia (3.1 to 8.9 × 2.0 to 4.0 μm). Chlamydospores were single or in pairs. These isolates were identified as F. oxysporum (3). The identity of F. oxysporum was confirmed by PCR assays using genomic DNA of each isolated and the universal primers Uni F and Uni R that generate a 672-bp PCR product. The pathogenic form and races were determined by PCR assays using the specific primers uni, sp13, sp23, and sprl that were able to discriminate all the three FOL races as well as F. oxysporum f. sp. radicis-lycopersici (FORL) isolates (2). The sp13 and sp23 primers amplified DNA bands of 445 and 518 bp, confirming the identity of FOL race 3. However, sprl amplified a fragment of 947 bp corresponding to FORL (2). Pathogenicity tests were conducted on 25-day-old seedlings (10 seedlings per isolate) of tomato ‘Poncho Negro,’ which is susceptible to FOL and FORL. Seedling roots were cut, submerged for 5 min in conidial suspension of 2 × 106 conidia/ml, and transplanted to 250-ml plastic containers with sterile substrate (sand/peat, 1:1). Equally treated non-inoculated seedlings were left as controls. The first symptoms induced by each of the five FOL isolates appeared 8 days after incubation under greenhouse and were characterized by yellowing of older leaves, sometimes affecting one side of the plant, vascular discoloration of the stem, and eventually plant death. In contrast, all seedlings inoculated with a FORL isolate developed a necrotic lesion and vascular discoloration at the base of the stems near the soil line, followed by wilting and plant death. Control plants remained asymptomatic. F. oxysporum was re-isolated only from inoculated plants, completing Koch's postulates. FOL and FORL were reported earlier in other tomato growing areas of Chile (1), located over 1,000 km south of the Azapa Valley. However, this is the first report of FOL race 3 and FORL in the Azapa Valley and FOL race 3 is reported for the first time in Chile. References: (1) S. Acuña. Compendio de Fitopatógenos de Cultivos Agrícolas. Servicio Agrícola y Ganadero. Gobierno de Chile, 2008. (2) Y. Hirano and T. Arie. J. Gen. Plant Pathol. 72:273, 2006. (3) J. F. Leslie and B. A. Summerell. The Fusarium Laboratory Manual. Blackwell Publishing, Ames, IA, 2006.

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First Report of Fusarium Wilt of Cilantro Caused by Fusarium oxysporum in California

Plant Disease ◽

10.1094/pd-89-1130a ◽

2005 ◽

Vol 89 (10) ◽

pp. 1130-1130 ◽

Cited By ~ 3

Author(s):

S. T. Koike ◽

T. R. Gordon

Keyword(s):

Fusarium Oxysporum ◽

Fusarium Wilt ◽

Vascular Tissue ◽

Fusarium Species ◽

Wilt Disease ◽

Apium Graveolens ◽

Peat Moss ◽

State University ◽

First Report ◽

Vascular Discoloration

Cilantro, or coriander (Coriandrum sativum), is a leafy vegetable in the Apiaceae and is grown commercially in California primarily for use as a fresh herb. During 2002 and 2003 in coastal California (Santa Barbara County), commercial cilantro fields showed symptoms of a wilt disease. Affected plants grew poorly and were stunted. Lower foliage turned yellow with reddish tinges, and plants wilted during warmer times of the day. The main stem, crown, and taproot exhibited vascular discoloration that was reddish to light brown. As disease progressed, plants eventually died. For both years, the disease distribution was limited to isolated small patches (each patch measuring less than 1 m2 in area). A fungus was consistently isolated from symptomatic vascular tissue in crowns and taproots. On the basis of colony and conidial morphology, the isolates were identified as Fusarium oxysporum (2). No other fungi or bacteria were recovered from these plants. To test pathogenicity, suspensions containing 1 × 106 conidia/ml were prepared for five isolates. The roots of 30-day-old cilantro plants of four cultivars (30 plants each of Festival, Leisure, Santo, and LSO 14) were clipped and then soaked in the suspensions for 20 min. The roots of 30 plants of each cultivar were soaked in water as a control. Plants were repotted into new redwood bark + peat moss rooting medium and maintained in a greenhouse setting at 24 to 26°C. After 1 month, 95% or more of the inoculated plants showed yellowing and vascular discoloration symptoms similar to those seen in the field. F. oxysporum was reisolated from all inoculated plants. The four cilantro cultivars did not show differences in disease severity. Control plants showed no symptoms, and the fungus was not recovered from these plants. The experiment was repeated and the results were the same. Experiments also were conducted to determine if cilantro isolates could cause disease in celery (Apium graveolens var. dulce). Celery transplants and cilantro seedlings were prepared and inoculated as described above. However, after 2 months, celery plants did not show any disease symptoms, while the cilantro developed wilt symptoms and eventually died. A Fusarium wilt disease has been reported on coriander in Argentina and India where the pathogen was named F. oxysporum f. sp. coriandrii (1,3). To our knowledge, this is the first report of Fusarium wilt of cilantro in California. References: (1) M. Madia et al. Fitopatologia 34:155, 1999. (2) P. E. Nelson et al. Fusarium species: An Illustrated Manual for Identification. Pennsylvania State University Press, University Park, 1983. (3) U. S. Srivastava. Indian Phytopathol. 22:406, 1969.

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First Report of Fusarium Wilt of Lettuce Caused by Fusarium oxysporum f. sp. lactucae in Arizona

Plant Disease ◽

10.1094/pdis.2003.87.10.1265c ◽

2003 ◽

Vol 87 (10) ◽

pp. 1265-1265 ◽

Cited By ~ 23

Author(s):

M. E. Matheron ◽

S. T. Koike

Keyword(s):

Fusarium Oxysporum ◽

Root Rot ◽

The United States ◽

San Joaquin Valley ◽

Fluorescent Light ◽

Lettuce Seedling ◽

Disease Symptoms ◽

First Report ◽

Root Rot Disease ◽

Rot Disease

A new wilt and root rot disease was observed in 6 and 11 commercial fields of lettuce (Lactuca sativa) in western Arizona during the fall of 2001 and 2002, respectively. Distance between infested sites ranged from approximately 0.5 to 39 km. Five head lettuce cultivars as well as a red leaf lettuce cultivar were affected. Disease symptoms included yellowing and wilting of leaves, as well as stunting and plant death. The cortex of the crown and upper root of infected plants usually was decayed and reddish brown. Disease symptoms first appeared at the time of plant thinning and continued to develop up to plant maturity. Fusarium oxysporum was consistently isolated from symptomatic plant roots. Seeds of cv. Lighthouse were planted in nonsterile vermiculite within 3.0-cm-square × 7.0-cm-deep cells in a transplant tray and thinned to a single plant per cell. When the first true leaves were emerging, 10 individual seedlings were inoculated with a single-spore isolate of F. oxysporum recovered from diseased lettuce root cortex tissue. Inoculum was prepared by growing the fungus on potato dextrose agar in 100-mm-diameter × 15-mm-deep plastic petri dishes at 28°C with a 12-h photoperiod under fluorescent light. Once the fungus completely covered the agar surface, 50 ml of sterile distilled water was added to the dish, and the mycelia and conidia on the surface were scraped off the agar and suspended in the water. This fungal suspension was decanted, and a 2-ml aliquot containing 1.8 × 105 CFU was pipetted into the vermiculite near the stem of each lettuce seedling. Ten plants grown in noninfested vermiculite served as uninoculated controls. After inoculation, plants were maintained in a growth chamber at 28°C with a 12-h photoperiod under fluorescent light for 3 weeks. Symptoms of yellowing, wilt, vascular decay, and often plant death developed during the incubation period on all inoculated plants but not on control plants. Fusarium oxysporum was consistently reisolated from inoculated plants but not from uninoculated plants. The experiment was repeated and yielded the same results. A wilt and root rot disease of lettuce attributed to F. oxysporum f. sp. lactucae was first reported in Japan in 1967 (3) and subsequently in the United States (San Joaquin Valley of California) in 1993 (2), and Italy in 2002 (1). The researchers of the U.S. report did not cite the earlier work from Japan and described the pathogen as F. oxysporum f. sp. lactucum. The Arizona isolate used to demonstrate pathogenicity was of the same vegetative compatibility group as an isolate of the pathogen from lettuce in California reported in 1993. Several companies grow and harvest lettuce in Arizona and California. At the end of production and harvest in the fall, tractors, implements, and harvesting equipment are transported from the San Joaquin Valley in California to western Arizona. The similarity between the isolate of F. oxysporum f. sp. lactucae from western Arizona and the San Joaquin Valley of California suggest a possible introduction of the pathogen into Arizona from California, perhaps on soil adhering to farm equipment. To our knowledge, this is the first report of F. oxysporum f. sp. lactucae infecting lettuce in Arizona. References: (1) A. Garibaldi et al. Plant Dis. 86:1052, 2002. (2) J. C. Hubbard and J. S. Gerik. Plant Dis. 77:750, 1993. (3) T. Matuo and S. Motohashi. Trans. Mycol. Soc. Jpn. 8:13, 1967.

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Diversity of Airborne Fungi at Pepper Plantation Lembah Bidong, Kuala Terengganu

Borneo Journal of Resource Science and Technology ◽

10.33736/bjrst.2683.2020 ◽

2020 ◽

Vol 10 (2) ◽

pp. 147-154

Author(s):

NUR AINU FARHAH RABAE ◽

SALMAN AZIZ ◽

ASAMOAH FREDERICK OSEI ◽

SITI NORDAHLIAWATE MOHAMED SIDIQUE

Keyword(s):

Fusarium Oxysporum ◽

Fungal Pathogens ◽

Economic Loss ◽

Airborne Fungi ◽

Plant Diseases ◽

Piper Nigrum ◽

Pepper Plant ◽

Trichoderma Sp ◽

Fusarium Sp ◽

Significant Economic Loss

Piper nigrum L. is well-known as the king of spices and widely used in various field such as food and medicines. In Malaysia, 98% of pepper production comes from the state of Sarawak. The National Commodity Policy (2011-2020) targets to increase the pepper plantation area from the current 16,331 ha to 20,110 ha by year 2020. However, pepper diseases remain as a major challenge in the pepper industry. A great number of airborne fungi pathogen may contribute to a significant economic loss in pepper production. Therefore, this study aims to morphologically identify the diversity of fungi obtained from air-borne samples in a pepper planation that are capable of causing pepper plant diseases. This experiment was conducted at a pepper plantation near Lembah Bidong, Kuala Terengganu. An Andersen spore sampler was used to collect the fungi spores. Culture based identification were then made. The study resulted in the identification of four genus of fungi such as Fusarium sp, Fusarium semictectum Fusarium oxysporum, Curvularia sp., Penicillium sp. and Trichoderma sp. (Ascomycetes). Further molecular identification will confirm the species of fungal pathogens and more understanding of their population as well as severity. Keywords: Pepper, Piper nigrum L., air-borne, fungi, Andersen spore sampler

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First Report of Stem Wilt and Root Rot of Schlumbergera truncata Caused by Fusarium oxysporum f. sp. Opuntiarum in Southern Italy

Plant Disease ◽

10.1094/pdis-11-12-1092-pdn ◽

2013 ◽

Vol 97 (6) ◽

pp. 846-846 ◽

Cited By ~ 6

Author(s):

F. Lops ◽

F. Cibelli ◽

M. L. Raimondo ◽

A. Carlucci

Keyword(s):

Fusarium Oxysporum ◽

Root Rot ◽

Southern Italy ◽

Nucleotide Sequences ◽

Control Treatment ◽

Conidial Suspension ◽

Internal Transcribed Spacer Region ◽

Fungal Isolation ◽

First Report ◽

Fusarium Sp

Schlumbergera truncata (Haw.) Moran, belonging to the Cactaceae, is a very common ornamental cactus in southern Italy. In November 2011, sudden stem wilt and root rot was observed in about 45% of vegetatively propagated plants cultivated as potted ornamental plants in a commercial greenhouse in Cerignola (Foggia Province, Apulia, Italy). The roots and collars of the plants showed brown rot. Yellow sunken lesions that were similar to cortical cankers were detected at basal level of the stem. Ten plants with these symptoms were analyzed by fungal isolation techniques. Small (0.5 cm) tissue portions from root, collar, and basal stem were plated on potato dextrose agar (PDA) after disinfection with 75% ethanol for 1 to 2 min, 0.2% NaOCl for 1 to 2 min, and a wash with sterile distilled water. A fungal isolate that was morphologically similar to Fusarium sp. was isolated from 85% of these tissue samples. It had nucleotide sequences of the internal transcribed spacer region (ITS1-5.8S-ITS2) of ribosomal DNA (GenBank Accession No. KC196121) 100% identical to those of the comparable sequences of Fusarium oxysporum (HQ651161). The nucleotide sequences of its translation elongation factor 1-α (EF-1α) gene (KC196120) showed 100% identity to sequences of F. oxysporum f. sp. opuntiarum (DQ837689, AF246881) retrieved from GenBank. Pathogenicity tests were performed at 22 ± 3°C on 18 45-day-old plants of S. truncate by adding of a 5-ml aliquot of conidial suspension adjusted to 5 × 106 conidia/ml to soil of each plant. Six non-inoculated plants were used for a control treatment and sprayed with 5 ml of sterilized water. Plants were maintained in greenhouse at 22 ± 3°C. After 10 days, nine of the inoculated plants showed wilting, and after 45 days, all of them were dead, with root and collar rot and lesions on the basal stem. Control plants were symptomless. Koch's postulates were fulfilled as the pathogen was reisolated from all of the symptomatic tissues and identified as Fusarium sp. On the basis of 3-septate macroconidia (mean 31.75 × 3.21 μm; range, 26 to 35 μm long, 3.0 to 4.2 μm wide), aseptate microconidia, single chlamydospores, and monophialide conidiophores on carnation leaf agar, and molecular analyses, the fungus was identified as F. oxysporum f. sp. opuntiarum (Speg) (1,2,3). In Italy, F. oxysporum f. sp. opuntiarum was reported as basal stem rot of Echinocactus grusoni (4). To our knowledge, this is the first report of stem wilt and root rot of S. truncata caused by F. oxysporum f. sp. opuntiarum in Italy. References: (1) W. Gerlach. Phytopathol. Z. 74:197, 1972. (2) W. L. Gordon. Can. J. Bot. 43:1309, 1965. (3) P. E. Nelson et al. Fusarium Species: An Illustrated Manual for Identification. Pennsylvania State University Press, University Park, 1983. (4) G. Polizzi et al. Plant Dis. 88:85, 2004.

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First Report of Fusarium Wilt of Exacum affine Caused by Fusarium oxysporum

Plant Disease ◽

10.1094/pdis.2001.85.10.1120c ◽

2001 ◽

Vol 85 (10) ◽

pp. 1120-1120 ◽

Cited By ~ 2

Author(s):

W. Elmer ◽

E. O'Dowd

Keyword(s):

Fusarium Wilt ◽

Vascular Tissue ◽

Fusarium Species ◽

Plant Diseases ◽

State University ◽

Pennsylvania State University ◽

First Report ◽

Millet Seed ◽

Soil Mix ◽

Exacum Affine

Wilting Persian violets (Exacum affine) were observed in a Connecticut retail outlet. Diseased stems developed a dark coloration at the nodes, while the foliage turned papery, whitish tan. The vascular tissue in affected stems was reddish brown and extended from the base of the stem upward in a unilateral pattern. Fusarium grew from the discolored stem tissue when placed on Komada's medium (2). Single spores were cultured on carnation leaf agar and identified as F. oxysporum (2). Koch's postulates were completed by growing 12 2-month-old seedlings of E. affine ‘Midget’ in potting mix amended with ground dried millet seed (2.0 g/liter of soil) that had been colonized for 2 weeks by the fungus. Symptoms appeared slowly after 8 weeks, and F. oxysporum was re-isolated from the vascular tissue. Plants grown in soil mix with sterile millet remained healthy. Similar tests at different times of the year produced the same results. Other tests examined host specificity with two new isolates on seedlings of Persian violet, carnation, lisianthus, and basil. Both isolates caused symptoms only on Persian violets. Although Haematonectria haematococca (synonym Nectria haematococca, anamorph F. solani) causes Nectria canker of Persian violet (1), this is the first report of F. oxysporum causing Fusarium wilt of Persian violet. We propose the formae specialis be F. oxysporum f. sp. exaci. An isolate has been deposited at the Fusarium Research Center at The Pennsylvania State University, University Park, under Accession No. O-2282. References: (1) M. Daughtrey et al. Compendium of Flowering Potted Plant Diseases. American Phytopathological Society, St. Paul, MN, 1995. (2) Nelson et al. Fusarium species: An Illustrated Manual for Identification. The Pennsylvania State University Press, University Park, PA, 1983.

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First Report of Root Rot on Pulsatilla koreana Caused by Fusarium oxysporum in China

Plant Disease ◽

10.1094/pdis-09-12-0849-pdn ◽

2013 ◽

Vol 97 (3) ◽

pp. 425-425 ◽

Cited By ~ 1

Author(s):

D. Su ◽

J. F. Fu

Keyword(s):

Fusarium Oxysporum ◽

Root Rot ◽

Its Region ◽

Liaoning Province ◽

Conidial Suspension ◽

Single Spore ◽

Laboratory Manual ◽

First Report ◽

Medicinal Value ◽

Rot Disease

Windflowers (Pulsatilla spp.) are perennial medicinal plants in the family Ranunculaceae with high economic as well as medicinal value in China. It is commonly used as traditional Chinese medicine (1). In May 2012, a root rot disease was observed on windflower (Pulsatilla koreana Nakai) at flowering stages in fields of Liaoning Province, China. The diseased area was estimated to be over 500 ha in the province and the yield was reduced by 30% on average with up to 45% yield losses in some fields. As the disease progressed, brown lesion production extended onto lateral and main roots, and aboveground tissues shriveled and decayed; in severe cases, white mycelium was clearly visible on diseased root tissue. Isolations from symptomatic roots were made on potato dextrose agar (PDA) and single-spore cultures were obtained. Colonies were initially white, but became pale violet with age, and purple pigments were produced in the agar. Microconidia were abundant, unicellular, oval to reniform, and ranged from 5.6 to 13.1 (9.3) × 2.8 to 4.2 (3.2) μm. Macroconidia were sparse, three-septate, slightly curved, and ranged from 21.9 to 39.4 (31.2) × 3.4 to 4.5 (3.9) μm. The isolated fungus was morphologically similar to Fusarium oxysporum (2). Two isolates were selected for molecular identification, and the internal transcribed spacer (ITS) region of rDNA was amplified using the primers ITS1/ITS4 (3) and sequenced. The obtained sequences (GenBank Accession Nos. JX669525 and JX669526) showed 99% homology with the sequences of F. oxysporum in GenBank (GQ121303). For pathogenicity tests, the isolate was cultured on PDA for 10 days at 25°C. Inoculations were performed on 10 healthy P. koreana plants by spraying a conidial suspension (2.0 × 105 microconidia ml–1) on roots previously wounded with a metal needle. Ten non-treated plants used as controls were sprayed with distilled water. The inoculated plants were incubated at 25°C under conditions of 12/12 h (light and dark). After 2 weeks, root rot symptoms were similar to the original symptoms observed under field conditions. No disease was observed on water-inoculated control plants. The same fungus was reisolated from the roots of infected plants, satisfying Koch's postulates. To our knowledge, this is the first report of F. oxysporum on P. koreana in China. The disease was hitherto scarcely reported in any other countries, and may deserve more attention in the future. References: (1) S. C. Bang et al. J. Nat. Prod. 68:268, 2005. (2) J. F. Leslie and B. A. Summerell. The Fusarium Laboratory Manual. Blackwell Professional, Ames, IA, 2006. (3) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, 1990.

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Detection of Fusarium oxysporum f. sp. melonis Race 1 in Soil in Colima State, Mexico

Plant Disease ◽

10.1094/pdis.2004.88.12.1383c ◽

2004 ◽

Vol 88 (12) ◽

pp. 1383-1383 ◽

Cited By ~ 2

Author(s):

M. de Cara ◽

E. J. Fernández ◽

R. Blanco ◽

J. C. Tello Marquina ◽

F. J. Estrada ◽

...

Keyword(s):

Fusarium Species ◽

Selective Medium ◽

Soil Samples ◽

Potato Dextrose Agar ◽

Conidial Suspension ◽

State University ◽

Yield Losses ◽

Pennsylvania State University ◽

Differential Cultivars ◽

Race 1

During the winters of 2002 and 2003, a wilt occurred in melons cultivated on 1,500 ha in Colima State, Mexico. Yield losses reached 25% of final production, despite soil disinfestation with 60% methyl bromide and 40% chloropicrin. On the basis of the observation of plants with necrotic xylem, yellowing, and wilting of leaves, this disease was identified provisionally as Fusarium wilt. During February 2003, four soil samples from affected fields were plated onto a Fusarium-selective medium (1), which resulted in the detection of 2,260 ± 357, 179 ± 76, 668 ± 357, and 1,391 ± 256 CFU/g of F. oxysporum (3). Thirty-one randomly chosen isolates were used to inoculate differential cultivars of melon as described by Risser et al. (4). The cultivars were Amarillo Canario (susceptible to all races), Diana (resistant to races 0 and 2), Tango (resistant to races 0 and 1), and Vulcano (resistant to races 0, 1, and 2) (2). Ten plants of each cultivar, grown on sterilized vermiculite, were inoculated at the first true-leaf stage by drenching with 200 ml of a conidial suspension (1 × 105 CFU/ml) of each isolate. Noninoculated plants of each cultivar served as controls. Plants were maintained in a growth chamber with a 16-h photoperiod (18 × 103 lux) and temperatures at 23 to 25°C. Yellowing, wilt, and vascular discoloration symptoms developed on cvs. Amarillo Canario and Diana following inoculation with each of the 31 isolates, while noninoculated plants remained symptomless. F. oxysporum was consistently reisolated on potato dextrose agar from the affected plants. On the basis of the combination of affected cultivars, all isolates were identified as F. oxysporum f. sp. melonis race 1. To our knowledge, this is the first report of F. oxysporum f. sp. melonis race 1 in Colima State, Mexico. References: (1) H. Komada. Rev. Plant Prot. Res. 8:114, 1975. (2) J. Marín Rodríquez. Portagrano 2004. Vadmecum de Variedades Hortícolas. Agrobook, Spain. 2004. (3) P. E. Nelson et al. Fusarium Species: An Illustrated Manual for Identification. Pennsylvania State University Press, University Park, 1983. (4) G. Risser et al. Phytopathology 66:1105, 1976.

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First Report of Fusarium oxysporum f. sp. radicis-cucumerinum on Cucumber in Spain

Plant Disease ◽

10.1094/pdis.2001.85.11.1206a ◽

2001 ◽

Vol 85 (11) ◽

pp. 1206-1206 ◽

Cited By ~ 12

Author(s):

A. Moreno ◽

A. Alférez ◽

M. Avilés ◽

F. Diánez ◽

R. Blanco ◽

...

Keyword(s):

Fusarium Oxysporum ◽

Crown Rot ◽

F1 Hybrid ◽

Potato Dextrose Broth ◽

Disease Symptoms ◽

First Report ◽

Vascular Discoloration ◽

Root And Crown Rot ◽

Three Stages ◽

Stem Lesions

During December 1999, root and stem rot was observed on greenhouse-grown cucumber (cvs. Albatros, Brunex, Acapulco, and Cerrucho) plants in Almería, Spain, using rock wool cultures. The disease caused severe damage, estimated at a loss of up to 75% of the plants, in the first greenhouse affected; afterward, the disease was found in eight additional greenhouses (14 ha) in 1999 and 2000. Stem lesions extended up to 10 to 12 cm above the crown in mature plants, although no fruit damage was observed. In the advanced stages, abundant development of orange sporodochia was evident on crown and stem lesions, without vascular discoloration. Root, crown, and stem pieces that were placed on potato dextrose agar (PDA) after surface-disinfection with 5% sodium hypochlorite, rinsed, and dried resulted in pure fungal colonies. Based on morphological characteristics of conidia, phialides, and chlamydospores from the isolations, the fungus was identified as Fusarium oxysporum Schlechtend.:Fr. Pathogenicity tests were conducted on cucumber (cvs. Marketmore 76 and Cerrucho [F1 hybrid]), melon (cvs. Amarillo oro, Perlita, Piboule, Tania, and Nipper [F1]), watermelon (cvs. Sugar Baby, Sweet Marvel, Jubilee, and Pata Negra and hybrid Crimson sweet), Cucurbita maxima × Cucurbita moschata, zucchini (cv. Senator), and loofah (Luffa aegyptiaca) at several stages: (i) pregermination; (ii) 1 or 2 true leaves; and (iii) more than 10 true leaves. Five fungal isolates were grown on PDA or shaken potato dextrose broth at 25°C for 8 days. Inoculation was performed in pots (10 seeds or plants of each cultivar or hybrid and isolate) by drenching with 100 ml of a fungal suspension (104 to 106 CFU/ml). Sterile water was applied to noninoculated control plants. Tests were repeated in growth chambers at 25°C (night) and 28°C (day) with a 16-h photoperiod. Fifteen to fifty days after inoculation, cucumber and melon plants at all three stages developed symptoms of root and crown rot in 100% of inoculated plants, with no observed vascular discoloration. Fifty days after inoculation, all three stages of C. maxima × C. moschata and zucchini remained symptomless. Loofah and watermelon germinated poorly or not at all when inoculated at the pregermination stage. Fifteen to fifty days after inoculation, 100% of inoculated cucumber and melon plants developed symptoms. Watermelon plants inoculated at the 10 or more true-leaf stage did not develop disease symptoms. No symptoms developed on noninoculated control plants. F. oxysporum was reisolated from infected roots, crowns, and stems of inoculated plants, confirming Koch's postulates. The main symptoms on cucumber infected by F. oxysporum f. sp. cucumerinum are wilt, yellowing, and vascular discoloration. In contrast, based on inoculation of the host differentials and the resulting disease symptoms found in this study, the fungus was identified as F. oxysporum f. sp. radicis-cucumerinum (1). To our knowledge, this is the first report of F. oxysporum f. sp. radicis-cucumerinum causing root and crown rot in cucumber in Spain. Reference: (1) D. J. Vakalounakis. Plant Dis. 80:313, 1996.

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