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

Plant Disease ◽  
2004 ◽  
Vol 88 (12) ◽  
pp. 1383-1383 ◽  
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.

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

Plant Disease ◽  
1998 ◽  
Vol 82 (12) ◽  
pp. 1405-1405 ◽  
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.

scholarly journals First Report of Walnut Canker Caused by Fusarium incarnatum from India

Plant Disease ◽  
2011 ◽  
Vol 95 (12) ◽  
pp. 1587-1587
Author(s):  
B. Singh ◽  
C. S. Kalha ◽  
V. K. Razdan ◽  
V. S. Verma
Keyword(s):  
Fusarium Species ◽  
Juglans Regia ◽  
Infected Plant ◽  
Distilled Water ◽  
Conidial Suspension ◽  
State University ◽  
Single Spore ◽  
Jammu And Kashmir ◽  
First Report ◽  
Branch Dieback

While screening newly introduced cultivars of walnut (Juglans regia) at Bhaderwah (Mini Kashmir), Jammu and Kashmir, India in September 2008, 60% of grafted plants were found to be dying because of a cankerous growth observed on seedling stems. Later, these symptoms extended to lateral branches. In the surveyed nurseries, cvs. SKU 0002 and Opex Dachaubaria were severely affected by the disease. Cankers were also observed in all walnut nurseries in the area with several wild seedlings also being observed to be exhibiting similar cankerous symptoms on stem and branches. Necrotic lesions from cankerous tissues on seedling stems were surface disinfested with 0.4% NaOCl for 1 min and these disinfected cankerous tissues were grown on potato dextrose agar (potato-250 g, dextrose-15 g, agar-15 g, distilled water-1 liter). A Fusarium sp. was isolated consistently from these cankerous tissues, which was purified using single-spore culture. Carnation leaf agar was used for further culture identification (2,3). The fungal colony was floccose, powdery white to rosy in appearance when kept for 7 days at 25 ± 2°C. Macroconidia were straight to slightly curved, four to eight septate and 30 to 35 × 3.5 to 5.7 μm. These are characteristics consistent with Fusarium incarnatum (3). Pathogenicity was confirmed by spraying a conidial suspension (1 × 106 conidia/ml) onto bruised branches of 1-year-old walnut plants (cv. Opex Dachaubaria) while sterile distilled water sprays were used for the controls. Inoculated plants were incubated at 20 ± 2°C and 85% relative humidity for 48 h. Fifty days following inoculation, branch dieback followed by canker symptoms developed on inoculated plants. Control plants remained healthy with no symptoms of canker. F. incarnatum (Roberge) Sacc. was repeatedly isolated from inoculated walnut plants, thus satisfying Koch's postulates. Infected plant material has been deposited at Herbarium Crytogamae Indiae Orientalis (ITCC-6874-07), New Delhi. To our knowledge, this is the first report of walnut canker caused by F. incarnatum (Roberge) Sacc. from India. This fungus was previously reported to be affecting walnut in Italy (1) and Argentina (4). References: (1) A. Belisario et al. Informatore Agrario 21:51, 1999. (2) J. C. Gilman. A Manual of Soil Fungi. The Iowa State University Press, Ames, 1959. (3) P. E. Nelson et al. Fusarium Species. An Illustrated Manual for Identification. The Pennsylvania State University Press, University Park, 1983. (4) S. Seta et al. Plant Pathol. 53:248, 2004.

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

Plant Disease ◽  
2007 ◽  
Vol 91 (11) ◽  
pp. 1519-1519 ◽  
Author(s):  
W. H. Elmer ◽  
M. Daughtrey ◽  
K. Rane ◽  
M. M. Jimenez-Gasco
Keyword(s):  
Fusarium Oxysporum ◽  
Root Rot ◽  
Economic Loss ◽  
Conidial Suspension ◽  
State University ◽  
Pennsylvania State University ◽  
Disease Symptoms ◽  
Vascular Discoloration ◽  
Millet Seed ◽  
Significant Economic Loss

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.

Bioassay and baiting methods for determining occurrence of races of Phytophthora clandestina in soil

1996 ◽  
Vol 36 (7) ◽  
pp. 815 ◽  
Author(s):  
A Purwantara ◽  
SP Flett ◽  
PJ Keane
Keyword(s):  
Disease Severity ◽  
Root Rot ◽  
Subterranean Clover ◽  
Soil Samples ◽  
Field Soil ◽  
Flooded Soil ◽  
Aphanomyces Euteiches ◽  
Differential Cultivars ◽  
Pure Cultures ◽  
Race 1

The method currently used for determining races of Phytophthora clandestina requires isolation of pure cultures of the pathogen and testing of their pathogenicity on a range of differential cultivars. To date, the pathogen has not been isolated directly from soil and isolation of the pathogen from naturally infected seedlings is laborious. A bioassay involving the planting of differential cultivars in soil samples in small planting trays was developed to identify races of P. clandestina in soil. The specific races of the pathogen in the soil were determined by assessing the disease severity and the extent of sporulation of the pathogen on the roots of the differential cultivars. A more rapid baiting method using cotyledons of differential cultivars in flooded soil samples was also developed to determine the presence of different races in the samples. Both bioassays were used to confirm the presence of race 0 and race 1 in separate paddocks at Rutherglen, northern Victoria, over 4 seasons. The presence in field soil of another root rot pathogen of subterranean clover, Aphanomyces euteiches, was also detected using these techniques.

scholarly journals Crown Rot of Zucchini Squash Caused by Fusarium solani f. sp. cucurbitae in Almería Province, Spain

Plant Disease ◽  
2008 ◽  
Vol 92 (7) ◽  
pp. 1137-1137 ◽  
Author(s):  
J. Gómez ◽  
J. M. Guerra-Sanz ◽  
M. C. Sánchez-Guerrero ◽  
Y. Serrano ◽  
J. M. Melero-Vara
Keyword(s):  
Fusarium Solani ◽  
Morphological Characteristics ◽  
Crown Rot ◽  
State University ◽  
Pennsylvania State University ◽  
Its1 Region ◽  
5.8S Rdna ◽  
Race 1 ◽  
Petri Plate ◽  
The One

Cucumber, melon, watermelon, and zucchini are intensively cropped in the southern part of Spain where approximately 20,000 ha of the crops are grown in greenhouses. In the spring of 2007, zucchini plants (Cucurbita pepo) at the fruit-bearing stage in three commercial plastichouses in Almería exhibited necrosis on the basal stem, wilt, and death. The incidence of dead plants was 20 to 30%. Fusarium solani was consistently isolated from the basal stems of symptomatic plants on potato dextrose agar (PDA). Cultures of six single-hyphal transfers were identified on the basis of molecular sequences and morphological characteristics (2). Sequences of ribosomal DNA from ITS1 region, 5.8S rDNA, and ITS2 were identical for all six isolates of F. solani. The rDNA sequence of isolate Fscl-3 of F. solani was deposited as GenBank Accession No. AM940070. The pathogenicity of these six isolates of F. solani was tested in two experiments conducted in one plastichouse in Almería. Pregerminated seeds of zucchini cv. Consul were sown in 1-liter containers filled with vermiculite on 21 May and 22 June, 2007 (experiments 1 and 2, respectively). Plants at the one- to two-true-leaf stage or younger were inoculated with a soil drench of 2.0 to 8.4 × 105 propagules per ml). One colonized PDA petri plate of each isolate was blended and homogenized in 500 ml of distilled water. Inoculum (50 ml per plant) was poured around the stem of zucchini plants growing in vermiculite. The experimental design was a randomized complete block with three replicates with each plot comprising four plants (one plant per container). In both experiments, 12 uninoculated plants of the same cultivar served as controls. Plants were maintained for 1 month following inoculation in a greenhouse with mean temperatures ranging between 20.7 and 24.6°C and 23.3 to 29.8°C for experiments 1 and 2, respectively. Wilting first occurred 9 days after inoculation, and 14 days later, all plants inoculated with the F. solani isolates died. Inoculated plants exhibited lesions on the stem base without rot of secondary roots. At the end of the experiment, the uninoculated plants remained asymptomatic. Results of experiment 2, with higher temperatures, were similar. The pathogen was consistently recovered from symptomatic plants in both experiments, fulfilling Koch's postulates. Although F. solani f. sp. cucurbitae race 1 was reported in field squash (C. maxima) in the province of Valencia of east-central Spain (1), to our knowledge, this is the first report of F. solani as the causal agent of crown rot of zucchini plants in plastichouses in the Almería Province of Spain, one of the world's largest concentrations of greenhouses. References: (1) J. García-Jiménez et al. Plant Dis. 81:1216, 1997. (2) C. M. Messiaen and R. Cassini. Taxonomy of Fusarium. Page 427 in: Fusarium: Diseases, Biology, and Taxonomy. P. E. Nelson et al., eds. Pennsylvania State University, University Park, 1981.

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

Plant Disease ◽  
2001 ◽  
Vol 85 (10) ◽  
pp. 1120-1120 ◽  
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.

scholarly journals First Report of a Wilt Disease of Hiemalis Begonias Caused by Fusarium foetens in the United States

Plant Disease ◽  
2004 ◽  
Vol 88 (11) ◽  
pp. 1287-1287 ◽  
Author(s):  
W. H. Elmer ◽  
C. Vossbrinck ◽  
D. M. Geiser
Keyword(s):  
Elongation Factor ◽  
Aerial Mycelium ◽  
The United States ◽  
Wilt Disease ◽  
Potato Dextrose Agar ◽  
State University ◽  
Rare Occurrence ◽  
Pennsylvania State University ◽  
Fusarium Spp ◽  
Fusarium Foetens

During 2003, 10% of the Hiemalis begonias (Begonia × hiemalis Fotsch) developed wilt symptoms in a commercial greenhouse in Connecticut. Foliage turned a dull green, and stems developed a dark watersoaked discoloration near the soil line and had vascular discoloration. Stems, petioles, and leaves collapsed and became covered with sporodochia of a Fusarium spp. Single conidia were isolated from sporodochia and cultured on carnation leaf agar (CLA) and potato dextrose agar for 10 days. Isolates resembled Fusarium oxysporum, but the profuse sporulation with minimal aerial mycelium and the rare occurrence of polyphialides was consistent with the description of F. foetens (2). A comparison of a partial sequence of the 1-α elongation factor gene showed a 100% match with F. foetens. Inocula from five isolates were grown on CLA, washed from the plate, and adjusted to 106 conidia per ml. Suspension (50 μl) was injected into stems of healthy 6-week-old Hiemalis begonias cv. Barkos (one plant per isolate). Controls received distilled water. After 4 weeks, all inoculated plants turned dark and collapsed, and the same fungus was reisolated from these plants. Control stems remained healthy. An isolate (O-2348) has been deposited at the Fusarium Research Center at Pennsylvania State University, University Park. F. foetens has recently been described in association with a new disease of Hiemalis begonias in Europe (1). References: (1) R. Schrage, Phytomedizinischen Gesellschaft 33:68, 2003. (2) H.-J. Schroers et al. Mycologia 96:393, 2004.

scholarly journals Yield Comparison of Hybrid Agaricus Mushroom Strains as a Measure of Resistance to Trichoderma Green Mold

Plant Disease ◽  
2001 ◽  
Vol 85 (7) ◽  
pp. 731-734 ◽  
Author(s):  
M. G. Anderson ◽  
D. M. Beyer ◽  
P. J. Wuest
Keyword(s):  
Agaricus Bisporus ◽  
Yield Loss ◽  
State University ◽  
Yield Losses ◽  
Pennsylvania State University ◽  
Trichoderma Spp ◽  
Green Mold ◽  
Spawning Time ◽  
Significant Yield ◽  
Mold Resistance

Commercially available strains of hybrid white, hybrid off-white, and brown Agaricus bisporus mushrooms were compared for resistance to green mold caused by Trichoderma harzianum biotype 4 (Th4). Seven mushroom spawn strains were assessed for total weight of mushrooms (grams per 0.1 m2) with or without the addition of an aqueous Th4 spore suspension added at spawning time. Cropping studies were conducted at the Mushroom Research Center (Pennsylvania State University) to emulate commercial growing operations. Excessive spawn handling had no significant effect on development of green mold. Severity of green mold was related to time between infestation and green mold appearance, with more significant yield losses occurring when green sporulation was detected early in production. Significant differences in yield were measured among mushroom strains in response to Th4 infestation. Hybrid white strains were extremely susceptible, with a mean yield loss of 96%. Hybrid off-white strains exhibited intermediate susceptibility, with mean yield losses of 56 to 73%. Brown strains were highly resistant, with mean yield losses of 9 to 16%. From these findings, we report the existence of green mold resistance, with a continuum of resistance among spawn strains. The findings suggest use of brown strains to manage green mold outbreaks, particularly where benomyl resistance in Trichoderma spp. is a threat.

scholarly journals First Report of Fusarium proliferatum Causing Rot of Garlic Bulbs in Spain

Plant Disease ◽  
2010 ◽  
Vol 94 (2) ◽  
pp. 277-277 ◽  
Author(s):  
D. Palmero ◽  
M. De Cara ◽  
C. Iglesias ◽  
M. M. Moreno ◽  
N. González ◽  
...  
Keyword(s):  
Produced Water ◽  
Fusarium Species ◽  
Fusarium Proliferatum ◽  
Plant Production ◽  
State University ◽  
Pennsylvania State University ◽  
First Report ◽  
Pathogenicity Tests ◽  
Fusarium Sp ◽  
The University

In October of 2008, decayed garlic bulbs (Allium sativum L. cv. Blancomor de Vallelado) were received from a producer in Segovia, Spain. In November of 2009, similar symptoms were observed on stored bulbs (cvs. Blancomor de Vallelado and Garcua) from each of 30 municipalities in northwest Segovia and Valladolid. A minimum of one sample was collected from 12 localities. Pieces of symptomatic bulbs were surface disinfested for 2 to 3 min in 0.5% NaOCl and transferred to potato dextrose agar (PDA) and Komada's media. Colonies had catenate microconidia and curved macroconidia that were usually three to five septate. Microconidia were club shaped with a flattened base, aseptate, and were produced on both mono- and polyphialides. On the basis of morphological features, the fungus was identified as Fusarium proliferatum (T. Matsushima) Nirenberg (2,3). Pathogenicity tests were conducted with 12 isolates of the fungi following the method of Dugan et al. (1). Each assay with an isolate consisted of six cloves (cv. Blancomor de Vallelado) disinfested in 0.5% NaOCl for 45 s, rinsed with sterile water, and injured to a depth of 4.5 mm with a probe 1 mm in diameter. The wound was filled with PDA colonized by the appropriate isolate. Six cloves for each tested isolate received sterile agar as a control. The cloves were incubated at 25°C for 5 weeks. The test was repeated once with cv. Garcua. All isolates produced water-soaked, tan lesions. An isolate of the fungus was deposited in the collection of the Plant Production Department of the University of Almeria. No fungi were recovered from the control cloves. F. proliferatum has been reported on garlic in the northwestern United States (1) and Serbia (4). To our knowledge, this is the first report of a Fusarium sp. in the section Liseola attacking garlic in Spain. The fungus seems to be well established on this host in Spain. References: (1) F. M. Dugan et al. Phytopathology 155:437, 2007. (2) P. E. Nelson et al. Fusarium Species: An Illustrated Manual for Identification. Pennsylvania State University Press, University Park, 1983. (3) H. Nirenberg et al. Mycologia 90:434, 1998. (4) S. Stankovic et al. Eur. J. Plant Pathol. 118:165, 2007.

scholarly journals Fusarium Wilt of Tomato Caused by Fusarium oxysporum f. sp. lycopersici Race 3 in Baja California Sur, Mexico

Plant Disease ◽  
2005 ◽  
Vol 89 (12) ◽  
pp. 1360-1360 ◽  
Author(s):  
R. J. Holguín-Peña
Keyword(s):  
Baja California ◽  
Fusarium Species ◽  
Restriction Enzymes ◽  
The State ◽  
Molecular Techniques ◽  
Conidial Suspension ◽  
Baja California Sur ◽  
La Paz ◽  
Vascular Discoloration ◽  
Race 1

Vascular wilting diseases have become one of the most serious diseases of tomato (Lycopersicon esculentum) throughout the Baja California Peninsula. Since the winter of 2004, a disease with symptoms characteristic of those caused by a Fusarium species has been observed in commercial fields near La Paz and Todos Santos in the state of Baja California Sur (BCS). Symptoms include typical one-sided wilting and dark brown vascular discoloration. Upper stem tissues and wilted seedlings were disinfested by immersion in a 1.0% aqueous solution of sodium hypochlorite for 2 min, rinsed in sterile water, and placed on Komada's medium (pH 6.8) at 22 ± 3°C. After 72 h, hyphal growth was recovered and subcultured on carnation leaf agar and potato dextrose agar and incubated at 25°C in 12-h light/dark cycles. Identification was based on colony morphology, conidial characteristics, and molecular techniques. White cottony mycelium, reddish coloration of the medium, ovoid two-celled macroconidia, and large macroconidia, all characteristic of F. oxysporum, were observed (2). Polymerase chain reaction and restriction fragment length polymorphisms with restriction enzymes EcoRI, RsaI, and HaeIII were used to characterize 24 isolates (sampled during January 2005) from La Paz (Fol-LaP) as formae speciales lycopersici and assigned to vegetative compatibility group 0030 (1). Confirmation of pathogenicity and race determination for the Fol-LaP isolates were as described previously (3). Mexican isolates of races 2 and 3 (one each) were included as positive controls. Conidial suspensions of 7 × 105 CFU/ml were used to inoculate differential tomato cvs. Bonny Best (Millington Co., universally susceptible), Tequila F1 (Vilmorin, race 1 resistant), Rio Grande (Harris Moran, race 1 and 2 resistant), and Sebring (Rogers, race 1, 2, and 3 resistant). Plants at the first true-leaf stage were inoculated by dipping their roots in the conidial suspension. Inoculated seedlings were transplanted into pots containing a sterile 5:1:1 mixture of sand/vermiculite/soil (v/v/v) and maintained in the greenhouse at 25 to 28°C under natural daylight. An equal number of plants of each cultivar dipped in water were used as controls. The experimental design was a completely randomized type with six replications (pots) containing four seedlings per pot. The test was done twice. The most susceptible plants inoculated by root-dipping developed typical symptoms of wilt, slight vein clearing on outer leaflets, stunting, dark brown vascular discoloration, and death. F. oxysporum was recovered from all symptomatic plants, whereas noninoculated tomato seedlings showed no symptoms. According to differential infection and symptomatology observed on infected cultivars, 62.5% of the isolated strains were identified as race 2, 25% as race 3, and 12.5% as an undetermined race isolated from Sebring. The presence of race 3 in BCS has important epidemiological implications since it has been reported on tomato in Sinaloa (4). The potential spread of the pathogen on introduced transplants represents a risk to tomato crops on the peninsula. To our knowledge, this is the first report of F. oxysporum f. sp. lycopersici race 3 in the state of BCS, Mexico. References: (1) G. Cai et al. Phytopathology 93:1014, 2003. (2) P. E. Nelson et al. Fusarium species. Pennsylvania State University Press, University Park, 1983. (3) B. A. Summerell et al. Plant Dis. 87:117, 2003. (4) J. G. Valenzuela-Ureta et al. Plant Dis. 80:105, 1996.

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