First Report of Rust Caused by Puccinia nakanishikii on Lemongrass, Cymbopogon citratus, in Florida.

Lemongrass, Cymbopogon citratus (DC.) Stapf. (Poaceae), is grown widely in the tropics and subtropics as an ornamental, flavoring ingredient in Asian cooking, and for tea and fragrant oil (3). In February 2013, rust symptoms were observed on lemongrass in several gardens in Miami-Dade County, Florida. Symptoms began as small chlorotic flecks on both leaf surfaces that became crimson and enlarged to streaks ~1 cm in length. On the abaxial side of leaves, erumpent streaks ruptured to produce pustules in which urediniospores formed. Eventually, streaks coalesced to produce large patches of tan to purplish necrotic tissue that blighted most of the leaf surface and was often surrounded by chlorotic borders. These symptoms, fungal morphology, and nuclear ribosomal large subunit (28S) DNA analysis were used to identify the pathogen as Puccinia nakanishikii Dietel. Urediniospores were pyriform to globose, orange to crimson, slightly echinulate, and somewhat longer than a previous report (32.1 ± 3.4 (27 to 42) × 23.3 ± 2.4 (21 to 27) µm vs. 22 to 28 × 22 to 25 µm) (2). Uredinia contained clavate paraphyses, but teliospores were not observed. No aecial host is known for this pathogen. A 28S DNA sequence that was generated with the NL1 and LR3 primers (1,4) was deposited in GenBank under accession no. KC990123; it shared 99% identity with GenBank accession GU058002, which came from a specimen of P. nakanishikii in Hawaii. Voucher specimens of affected leaves of lemongrass have been deposited at the Arthur Herbarium, Purdue University. Although this disease has been reported in California, Hawaii, New Zealand, and Thailand, this is believed to be the first report from Florida (2). Based on rainfall and temperature conditions that are conducive to its development in South Florida, it has the potential to significantly reduce the health and production of this plant in area gardens. References: (1) C. P. Kurtzman and C. J. Robnett. Antonie Van Leeuwenhoek 73:331. 1998. (2) S. Nelson. Rust of Lemongrass. Univ. Hawaii PD-57, 2008. (3) USDA, ARS, GRIN Online Database. URL: http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?12797 , accessed 25 April 2013. (4) R. Vilgalys and M. Hester. J Bacteriol. 172:4238, 1990.

First Report of a Leaf Spot Disease of Golden Dewdrop (Duranta erecta) Caused by Pseudomonas cichorii and a Xanthomonas Species in Florida.

Duranta erecta (Verbenaceae) is used extensively in southern states as an ornamental shrub and has replaced boxwood as the most common short hedge accenting flower beds. Over the past 2 years, during warm wet periods, dark necrotic leaf spots have been observed on golden dewdrop plants in Florida. Isolations from these spots on Difco nutrient agar (NA) consistently yielded two types of bacterial colonies that were not always simultaneously present: 1) round butyrous, bright yellow and 2) flat cream-colored. Both were 2 mm in size after 48 h, gram-negative, and produced a hypersensitivity reaction (HR) on tobacco cv Hicks. Yellow colony bacteria were oxidase negative and non-fluorescent on King's medium B (KMB) (1). Cream-colored colony bacteria were oxidase positive and fluorescent on KMB. Three isolates of both types were selected for further study. Partial 16S rDNA sequencing and fatty acid analysis (FAME) MIDI Microbial Identification System (Microbial ID, Inc., Newark, DE) were used for identification of strains. The 16S rDNA primers used were; forward primer AMB14 5'-TCCAGCAATGCCGCGTGTGT-3' and reverse primer AMB13 5'-CATCCACCGCTTGTGCGGGT-3'. The PCR program consisted of an initial denaturing cycle of 95°C for 2 min followed by 30 cycles of denaturing at 95°C for 30 s, annealing at 60°C for 40 s and extension at 72°C for 1 min and one final extension at 72°C for 10 min. Using FAME analysis, the three strains of the cream-colored colony type were identified as Pseudomonas cichorii with high similarity values (0.907, 0.961, 0.819) and this corresponded well with the 16S rDNA sequences where 99% sequence identity was observed with P. cichorii strain JBC1 16S ribosomal RNA gene, partial sequence GenBank Accession No. JF951725. Two of the three yellow colony strains were identified by MIDI FAME profiles as Xanthomonas axonopodis pv. manihotis with similarity coefficients of 0.767 and 0.826. The third strain had a low similarity match to X. a. pv. carotae (0.541). The 16S rDNA sequencing of these strains showed 98% sequence identity to X. citri subsp. citri strain SA1 16S ribosomal RNA gene only, partial sequence identity JQ890091.1, thus indicating a possible undescribed X. axonopodis pathovar. To satisfy Koch's postulates, three golden dewdrop 'Golden Mound' plants were sprayed with a suspension of 108 CFU/ml of a 2-day NA culture of each strain, bagged for 24 h to raise humidity, and placed in a greenhouse. A strain of P. cichorii (P409) isolated from chrysanthemum was used as a positive control when comparing cream-colored strains. A saline buffered control was used as a negative control. Within 3 weeks, leaf spots developed on plants sprayed with each of the six strains, including positive control strain of P. cichorii. Reisolations yielded the same type of colony as the originally inoculated strain. Inoculation experiments were repeated three times with a minimum of three plants per isolate with similar results. To our knowledge, this is the first report in the United States of bacterial leaf spot caused by P. cichorii and X. axonopodis on golden dewdrop. An earlier morphological and physiological description of a Xanthomonas sp. was done on Duranta in India in 1962 (2). Due to the difficulty in controlling bacterial diseases and the popularity of Duranta spp. in the landscape, these diseases may present a problem in ornamental trade. References: (1) E. O. King et al. J. Lab. Clin. Med. 44:301, 1954. (2) M. C. Srinivasan et al. Proc. Indian Acad. Sci. 56:88, 1962.

Severe Outbreak of Downy Mildew Caused by Plasmopara obducens on Impatiens walleriana in Florida.

Impatiens, Impatiens walleriana Hook.f., are grown as an ornamental crop in greenhouse and shade house production in Florida and other regions of the United States. Downy mildew on impatiens was detected from numerous landscapes (Manatee, Hillsborough, Collier, Hendry, Broward, Palm Beach, and Miami-Dade counties) in the winter of 2012. Incidence reached nearly 100% on many affected landscape plantings. Symptoms initially appeared as yellowing on the lower leaves and were typically vein-delineated, although in some cases the entire leaf was affected. Diseased plants later wilted and infected leaves abscised from the stem. A white, downy growth was apparent on the abaxial leaf surface. Microscopic observation revealed coenocytic mycelium with sporangiophores that were hyaline, thin-walled, and had slightly swollen bases. Branches of sporangiophores were monopodial and formed right angles to the supporting branches. Sporangia were hyaline and obvoid with a single pore on the distal ends that was mostly flat. Sporangia measured 19 to 22.5 × 13 to 17 µm. Oospores were observed in stem and leaf tissue. Leaves of 10 potted impatiens plants, I. walleriana 'Super Elfin XP Coral' and 'Super Elfin XP White,' were inoculated with a suspension containing 1 × 105 sporangia/ml and sprayed till runoff (approximately 20 ml per plant) with a handheld pressurized Ulva sprayer. Plants were maintained outside in a shade house under 73% shade where the daytime temperatures averaged 24°C and RH averaged 74% and nighttime temperature averaged 18°C with an average of 91% RH. Ten non-inoculated impatiens plants served as controls. After 10 days, symptoms typical of downy mildew occurred on 100% of the inoculated impatiens plants and sporulation was confirmed microscopically. The non-inoculated control plants remained healthy. The 5' end of the large ribosomal subunit gene (762 bp) from two isolates, one collected in Hillsborough County and one from Miami-Dade County, was amplified by PCR (primers NL1-GCATATCAATAAGCGGAGGAAAAG and NL4-GGTCCGTGTTTCAAGACGG) and sequenced bi-directionally (1,2,3). The consensus sequence from both isolates was identical and it was deposited into GenBank (Accession No. JX217746). Sequence data matched (99% homology) with Plasmopara obducens reported on I. walleriana in Europe and Australia (1,2). To our knowledge, this is the first report of downy mildew on I. walleriana in Florida (4). The disease has made a major impact on impatiens in landscapes throughout Florida and will likely continue to affect future production. References: (1) A. Bulajic et. al. Plant Dis. 95:491, 2011. (2) J. H. Cunnington et. al. Plant Pathol. 57:371, 2008. (3) K. O'Donnell. Curr. Genet. 22:213, 1992. (4) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, 1989.

First Report of Phytophthora palmivora Causing Foliar Blight of Pachira aquatica in Florida.

Pachira aquatica Aubl. is a member of the Bombaceae, indigenous to Central America and northern South America. Known as the money tree within the ornamental plant industry, this tropical species is well adapted to landscapes in south Florida, Hawaii, and milder areas in southern California. Recently, it's become more popular as a potted plant for use in the interiorscape. During August 2011, several local nurseries submitted P. aquatica samples to the Florida Extension Plant Diagnostic Clinic in Homestead, FL. The foliage exhibited dark brown to black water soaked spots that became papery as the disease progressed, and rapidly enlarged and coalesced, resulting in severe leaf blight. Both young and mature leaves were affected. Phytophthora was initially confirmed by serological testing with a commercially available ImmunoStrip test (Agdia, Elkhart, IN). On closer examination, the pathogen was further identified as Phytophthora palmivora by the presence of numerous papillate, deciduous, ellipsoidal to ovoid sporangia with short pedicels. The sporangia averaged 53 × 32 µm with ranges of 48 to 59 × 29 to 35 µm (1). Phytophthora species-specific primers (pal1s and pal2a) targeting part of the 18S rRNA gene, the ITS 1, the 5.8S rRNA gene, and the ITS 2 resulted in a PCR product of 648 bp, testing positive for P. palmivora (2). The PCR product was cleaned (Qiagen Purification Kit) and sequenced (GenBank Accession No. JQ354937). The sequence from our isolate was nearly identical (exhibited 99% nucleotide identity) to an isolate of P. palmivora (GenBank Accession No. HE580280) collected from diseased cassava in China. To further support identification, phylogenetic analysis by the maximum likelihood method (Tamura-Nei model) was performed using the obtained sequence and several other Phytophthora and Pythium species from GenBank (MEGA 5.05). Our isolate grouped with other P. palmivora isolates with high support (100% bootstrap values, 1,000 replicates). Pathogenicity of the sequenced isolate was evaluated in shade house experiments. Six-month-old Pachira aquatica plants were inoculated with sporangial suspensions (1 × 106 conidia/ml) of P. palmivora. Inoculum or autoclaved water was sprayed over the foliage until runoff. Six plants were sprayed per treatment, and the experiment was repeated twice. Inoculated plants were placed in a shade house (70% shade) when temperatures ranged from 25 to 32°C with 78 to 98% relative humidity. Plants were observed for disease development, which occurred within 7 days of inoculation. No symptoms developed on the control plants. Foliar lesions closely resembled those observed in the affected nurseries and P. palmivora was reisolated from symptomatic leaf tissue. To our knowledge, on the basis of serological testing, molecular analysis, and distinguishing morphological characters, this is the first report of P. palmivora causing foliar blight of Pachira aquatica in Florida. The high incidence and severity of this disease may seriously influence local tropical foliage producers in the future. References: (1) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. American Phytopathological Society, St Paul, MN, 1996. (2) Tsai et al. Botanical Studies 47:379, 2006.

First Report of Colletotrichum sansevieriae Causing Anthracnose of Sansevieria trifasciata in Florida.

Sansevieria Thunberg, a member of the Agavaceae, contains around 60 species indigenous to Africa, Arabia, and India. Several species and their cultivars are commercially produced for use as interior and landscape foliage plants. During August 2010, several local nurseries submitted Sansevieria trifasciata samples to the Florida Extension Plant Diagnostic Clinic in Homestead. Leaves had round, water-soaked lesions and as the disease progressed, lesions rapidly enlarged and coalesced, resulting in severe leaf blight. Both young and mature leaves were affected. Closer examination of mature lesions revealed numerous brownish black acervuli that were produced in concentric rings, which is characteristic of anthracnose. The fungus was identified as Colletotrichum sansevieriae Nakamura based on typical cultural characteristics, conidial and appressoria morphology (1). Conidia were straight, cylindrical, obtuse at the apex, slightly acute at the base with a truncate attachment point, and 12.5 to 33 (18.4) × 4 to 8.9 (6.5) µm (n = 50). Hyphopodia were ovate, dark brown, single celled, and 6.2 to 8.7 (7.7) × 6.3 to 7.5 (7.3) µm (n = 25). Colonies on potato dextrose agar (PDA) were grayish white, felted with aerial mycelium, reverse gray to dark olivaceous gray, and partly cream in color. Sequences of the rDNA internal transcribed spacer (ITS) regions of two isolates (GenBank Accession Nos. JF911349 and JF911350) exhibited 99% nucleotide identity to an isolate of C. sansevieriae (GenBank Accession No. HQ433226) collected from diseased sansevieria in Australia. In addition, a maximum parsimony analysis (MEGA v.5.0) indicates that the two C. sansevieriae isolates from Florida are monophyletic (86% bootstrap support) with the type species from Japan (SA-1-2 AB212991; SA-1-1 AB212990) and the Australian isolate. Pathogenicity of our sequenced isolates was evaluated in greenhouse experiments. Twelve- to fourteen-week-old sansevieria plants were inoculated with conidial suspensions (1 × 106 conidia/ml) of C. sansevieriae. Inoculum or autoclaved water was sprayed over the foliage until runoff. Four plants of each of two economically important cultivars, Laurentii and Moonshine, were sprayed per treatment and the experiment was repeated twice. Inoculated plants were placed in a greenhouse at 29°C with 70 to 85% relative humidity. Plants were observed for disease development, which occurred within 10 days of inoculation for both cultivars. No symptoms developed on the control plants. Foliar lesions closely resembled those observed in the affected nurseries. C. sansevieriae was consistently reisolated from symptomatic tissue collected from greenhouse experiments. On the basis of molecular phylogenetics and distinguishing morphological characters, Nakamura et al. erected C. sansevieriae as a novel species that appears to be restricted to the host sansevieria (1). To our knowledge, this is the first report of C. sansevieriae causing anthracnose of sansevieria in Florida. Reference: (1) M. Nakamura et al. J. Gen. Plant Pathol. 72:253, 2006.

Bacterial Soft Rot of Oncidium Orchids Caused by a Dickeya sp. (Pectobacterium chrysanthemi) in Florida.

Oncidium orchids have been subjected to extensive cultivation in the pot-plant and cut flower industries because of their attractive and numerous flowers. In August 2008, approximately 50 Oncidium 'Gower Ramsey' orchids were discovered at a commercial orchid nursery in South Florida with brown, macerated leaves typical of soft rot disease reported in other orchids. Ten plants were selected, and sections were removed from the edge of symptomatic tissue and bacteria were isolated according to the method described by Schaad et al. (3). All isolates were gram negative, anaerobic, degraded pectate, grew at 37°C, produced blue-to-brown pigment on nutrient agar-glycerol-manganese chloride (NGM) medium (1), were sensitive to erythromycin, oxidase negative, and positive for phosphatase and indole production. Further analyses were performed on four of the isolates. MIDI analysis (Sherlock version TSBA 4.10; Microbial Identification, Newark, DE) identified the isolates as Erwinia chrysanthemi (SIM 0.880 to 0.929). Polymerase chain reactions were performed with the 16S primers 27f and 1495r (4) and 1,423 bp of the 16S rDNA gene showed 98 to 99% sequence identity to Pectobacterium chrysanthemi (GenBank Accession No. FM946179). Sequences were deposited in GenBank (Nos. HQ287572-HQ287575). Pathogenicity tests were performed by injecting 10 Oncidium 'Gower Ramsey' orchids with 100 µl of a bacterial suspension at 1 × 108 CFU/ml. Ten plants were inoculated with 100 µl of sterile water as controls. Plants were placed in a greenhouse at 26.0°C to 30.0°C and 50 to 83% relative humidity. Soft rot symptoms were observed on all inoculated plants within 24 h while control plants appeared normal. A Dickeya sp. was reisolated and identified according to the method described above. Oncidium orchids are known to be highly susceptible to P. carotovora (= E. carotovora) and soft rot caused by P. carotovora is known to occur frequently on Oncidium orchids (2). Although, an Erwinia sp. has been reported to cause soft rot symptoms on Oncidium aureum, to our knowledge, this is the first report of a Dickeya sp. (= P. chrysanthemi) causing soft rot symptoms on Oncidium orchids grown in large-scale commercial production in the United States. References: (1) Y. A. Lee and C. P. Yu. J. Microbiol. Methods 64:200, 2006. (2) C. H. Liau et al. Transgenic Res. 12:329, 2003. (3) N. W. Schaad et al. Erwinia soft rot group. Page 56 in: Laboratory Guide for Identification of Plant Pathogenic Bacteria. 3rd ed. N. W. Schaad et al., eds. The American Phytopathological Society, St. Paul, MN, 2001. (4) W. G. Weisburg et al. J. Bacteriol. 173:697, 1991.

First Report of a Leaf Spot on Basella alba Caused by a Bipolaris sp. in Florida.

Malabar spinach (Basella alba L.) is a fast-growing, perennial vegetable crop grown largely in the tropics of Asia and Africa. This crop is widely used in the cuisine of different regions for its thick, semisucculent leaves, mild flavor, and mucilaginous texture. Leaf spots were observed on both surfaces of symptomatic leaf samples received from a home garden in Homestead, FL in November 2009. The necrotic lesions (up to 2 mm in diameter) were round, semicircular, or irregular-shaped with grayish centers surrounded by dark brown borders. A fungus was consistently isolated from symptomatic tissues on clarified V8 (CV8) agar. Fungal colonies on CV8 agar were black and velvet-like with minimal mycelial growth and conidiophores were dark brown, simple, borne singly or in groups upon the substrate. Conidia were straight, pale to medium golden brown, rounded at the ends with three to six septa, and on average measured 75 × 15 µm (48 to 97 × 9 to 18 µm). Cultural and conidial characteristics of the isolates were closely similar to those of a Bipolaris sp. (1). The internal transcribed spacer (ITS) region (~570 bp) of rDNA was amplified using the primers ITS1/ITS4 and sequenced bidirectionally (GenBank Accession No. JF506092). Subsequent database searches by the BLASTN program indicated that the resulting sequence had a 95% identity over 531 bp with the corresponding gene sequence of Bipolaris portulacae (GenBank Accession No. AY004778.1), a fungal pathogen reported to cause leaf spot on purslane (Portulaca oleracea) (2,3). However, our isolate has consistently smaller conidia and does not match descriptions of B. portulacae (BPI 871173, U.S. National Fungus Collections). The pathogenicity was confirmed through inoculation of healthy Malabar spinach plants with conidia of the isolate reproduced on CV8. Six Malabar spinach plants were inoculated with a suspension containing 1 × 106 conidia per ml and sprayed until runoff (approximately 15 ml per plant) with a handheld pressurized canister. Another six noninoculated plants served as a control. Immediately after inoculation, plants were covered with plastic bags for 24 h to maintain high relative humidity and maintained in a greenhouse under ambient conditions. Ten days after inoculation, the symptoms described above were observed on leaves of all inoculated plants, whereas symptoms did not develop on the control plants. A Bipolaris sp. was reisolated and identified by the above methods, fulfilling Koch's postulates. This pathogenicity test was carried out three times. To our knowledge, this is the first report of a Bipolaris sp. affecting Malabar spinach in Florida. Further work should be conducted to confirm identity of these isolates. Because of limited plantings of Malabar spinach, the economic importance of this disease in Florida is currently not known. Nevertheless, this pathogen poses a threat to the growing market of continuously produced oriental vegetables in Florida. References: (1) J. L. Alcorn. Mycotaxon 39:361, 1990. (2) S. A. Alfieri, Jr. et al. Bull. 14. Index of Plant Diseases in Florida (Revised). Florida Dep. Agric. Consumer Serv., Div. Plant Ind., 1984. (3) D. F. Farr and A. Y. Rossman. Fungal Databases. Systematic Mycology and Microbiology Laboratory. ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ , 25 January 2010.

First Report of Fruit Rot on Hylocereus undatus Caused by Bipolaris cactivora in South Florida.

Pitahaya (Hylocereus undatus (Haw.) Britton & Rose), a cactus grown for its edible fruit, is gaining popularity in South Florida as part of the specialty tropical fruit market. In July 2009, flowers and fruit were discovered with an uncharacterized rot. Small, circular, light brown, depressed lesions expanded to form large areas of rot on flowers and fruit in 7 to 10 days. The lesions produced large amounts of dark fungal spores. Single-spore isolates were identified morphologically and by aligning internal transcribed spacer (ITS) and glyceraldehyde-3-phosphate dehydrogenase (gpd) DNA sequences from the isolates with previously published sequences of Bipolaris, Drechslera, and Cochliobolus species. Conidia from the dark, blackish brown colonies were formed at the tips of pale golden brown, straight to flexuous conidiophores, 99 (184) 313 × 3 (6) 8 µm and slightly swollen at the apex and base. Conidia were pale-to-medium golden brown, smooth and clavate with a protuberant hilum, 24 (40) 51 × 9 (10) 13 µm, and two to four distoseptate. The isolates closely match descriptions of Bipolaris cactivora (= Drechslera cactivora) (3,4), although isolates from pitahaya had smaller conidia (30 to 65 µm) than previously reported. Conidial characteristics from a B. cactivora herbarium specimen BPI 431621 (U.S. National Fungus Collections) closely matched (29 (36) 50 × 8 (9) 11 µm, two to four distoseptate) our isolates. ITS (GenBank Accession Nox. HM598677-79) sequences aligned most closely (99.7% homology) with another B. cactivora isolate from China (GU390882), and both ITS and gpd (GenBank Accession Nos. HM598680-82) sequences indicate a close relationship to Bipolaris indica. Wounded or nonwounded mature pitahaya fruit and mature stems were inoculated with either a mycelia plug or a 15-µl 0.3% agar drop containing 105 conidia ml-1. Lesion diameters were measured after 7 days at 25°C, the fungus was reisolated on potato dextrose agar (PDA) and its identity was confirmed. Mean lesion diameters on mature fruit were 6.0 to 10.8 mm, depending on the inoculation method, and sporulation began 6 days after inoculation. On mature plant stems, wound-inoculated treatments formed 1.8 to 3.4 mm lesions, but nonwounded inoculations and controls were negative. Lesions were light tan, circular, and did not sporulate. To our knowledge, this is the first report of fruit rot caused by B. cactivora on pitahaya in Florida. The same pathogen causes stem rot of the Cactaceae in Europe and the United States (2) and a fruit rot on pitahaya in Japan (4). In Florida, it has been reported as causing a leaf spot on Portulaca oleracea (1). Our results indicate that B. cactivora causes flower and fruit rot on pitahaya, but does not seriously affect mature plant stems. The flower rot does not appear to significantly increase incidence but may provide inoculum for the fruit rot. The high incidence of fruit rot affecting commercial operations in Miami-Dade County over the past 2 years requires an effective disease management strategy. References: (1) S. A. Alfieri, Jr. et al. Bull. 14. Index of Plant Diseases in Florida (Revised). Florida Dep. Agric. Consumer Serv., Div. Plant Ind., 1984. (2) R. D. Durbin et al. Phytopathology 45:509, 1955. (3) M. B. Ellis. Page 432 in: Dematiaceous Hyphomycetes. Commonwealth Mycological Institute, Kew, England. 1971. (4) S. Taba et al. J. Gen. Plant Pathol. 73:374, 2007.

First Report of Sclerotium rolfsii on Ascocentrum and Ascocenda Orchids in Florida.

Southern blight caused by Sclerotium rolfsii is known to occur on several economically important orchid hosts, including Vanda species and hybrids (1-3). In the summer and fall of 2008, an outbreak of southern blight on Vanda orchids was seen in several commercial nurseries and landscapes throughout South Florida. More than a dozen orchids were affected at one of the locations, and symptoms of S. rolfsii were observed on Ascocentrum and Ascocenda orchids, which are also common in the trade and demand a resale value ranging from $20 to $150 for specimens in bloom. Affected Ascocentrum and Ascocenda orchids were found severely wilted at the apex, while around the base of the plants, tan, soft, water-soaked lesions were present. As the lesions progressed, leaves around the base of the plants began to fall off, leaving the stems bare. After 2 days, white, flabellate mycelium was seen progressing up the stem and numerous, tan-to-brown sclerotia were present. Leaves and portions of the stems were plated on acidified potato dextrose agar (APDA) and grown at 25°C. White, flabellate mycelium and tan sclerotia approximately 2 mm in diameter were produced in culture and microscopic examination revealed the presence of clamp connections. The fungus was identified as S. rolfsii and a voucher specimen was deposited with the ATCC. A PCR was performed on the ITS1, 5.8S rDNA, and ITS2 and the sequence was deposited in GenBank (Accession No. GQ358518). Pathogenicity of an isolate was tested by placing 6-mm plugs taken from APDA plates directly against the stem of five different Ascocentrum and Ascocenda orchids. Five Ascocentrum and Ascocenda orchids were inoculated with 6-mm plugs of plain APDA and five were untreated controls. Plants were housed under 50% shade, 60 to 95% humidity, and temperatures ranging from 75 to 88°F. Within 7 days, all inoculated plants developed symptoms that were identical to those observed on original plants and S. rolfsii was consistently reisolated from symptomatic tissue. Ascocentrum and Ascocenda were previously reported under miscellaneous orchid species and hybrids as hosts for S. rolfsii (1). However, this report was highly ambiguous and the most current edition does not report the host fungus combination (2). To our knowledge, this is the first report of S. rolfsii affecting Ascocentrum and Ascocenda orchids. References: (1) S. A. Alfieri, Jr., et al. Diseases and Disorders of Plants in Florida. Bull. No. 11. Division of Plant Industry, Gainesville, FL, 1984. (2) S. A. Alfieri, Jr., et al. Diseases and Disorders of Plants in Florida. Bull. No. 14. Division of Plant Industry, Gainesville, FL, 1994. (3) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St. Paul, MN, 1989.

First Report of a Bacterial Soft Rot on Tolumnia Orchids Caused by a Dickeya sp. in the United States.

Tolumnia orchids are small epiphytic orchids grown for their attractive flowers. In the fall of 2008, approximately 100 Tolumnia orchids with soft, brown, macerated leaves were brought to the University of Florida Extension Plant Diagnostic Clinic in Homestead. Ten plants were randomly selected and bacteria were isolated from the margins of symptomatic tissues of each of the 10 plants on nutrient agar according to the method described by Schaad et al. (2). Four reference strains were used in all tests, including the molecular tests: Erwinia carotovora subsp. carotovora (obtained from J. Bartz, Department of Plant Pathology, University of Florida, Gainesville), E. chrysanthemi (ATCC No. 11662), Pectobacterium cypripedii (ATCC No. 29267), and Acidovorax avenae subsp. cattleyae (ATCC No. 10200). All 10 of the isolated bacteria were gram negative, grew at 37°C, degraded pectate in CVP (crystal violet pectate) medium, grew anaerobically, produced brown pigment on NGM (nutrient agar-glycerol-manganese chloride) medium (1), were sensitive to erythromycin, and produced phosphatase. Three of the strains were submitted for MIDI analysis (Sherlock version TSBA 4.10; Microbial Identification, Newark DE) (SIM 0.732 to 0.963), which identified them as E. chrysanthemi. A PCR assay was performed on the 16S rRNA gene with primers 27f and 1495r described by Weisburg et al. (3) from two of the isolates and a subsequent GenBank search showed 99% identity of the 1,508-bp sequence to that of Dickeya chrysanthemi (Accession No. FM946179) (formerly E. chrysanthemi). The sequences were deposited in GenBank (Accession Nos. GQ293897 and GQ293898). Pathogenicity was confirmed by injecting approximately 100 µl of a bacterial suspension at 1 × 108 CFU/ml into leaves of 10 Tolumnia orchid mericlones. Ten plants were also inoculated with water as controls. Plants were placed in a greenhouse at 29°C with 60 to 80% relative humidity. Within 24 h, soft rot symptoms appeared on all inoculated leaves. The water controls appeared normal. A Dickeya sp. was reisolated and identified using the above methods (biochemical tests and MIDI), fulfilling Koch's postulates. To our knowledge, this is the first report of a soft rot caused by a Dickeya sp. on Tolumnia orchids. Although 16S similarity and MIDI results suggest the isolated bacteria are D. chrysanthemi because of its close similarity with other Dickeya spp., these results are not conclusive. Further work should be conducted to confirm the identity of these isolates. Through correspondence with South Florida Tolumnia growers, it appears this disease has been a recurring problem, sometimes affecting international orchid shipments where plant losses have been in excess of 70%. References: (1) Y. A. Lee and C. P. Yu. J. Microbiol. Methods 64:200, 2006. (2) N. W. Schaad et al. Erwinia soft rot group. Page 56 in: Laboratory Guide for Identification of Plant Pathogenic Bacteria. 3rd ed. N. W. Schaad et al., eds. American Phytopathological Society. St. Paul, MN, 2001. (3) W. G. Weisburg et al. J. Bacteriol. 173:697, 1991.

First Report of Downy Mildew Caused by a Peronospora sp. on Basil in Florida and the United States.

Basil is grown as a specialty crop in greenhouse and field production in Florida and other regions of the United States. Downy mildew on basil (Ocimum basilicum) was detected from four production sites (Collier, Hendry, Miami-Dade, and Palm Beach counties) in south Florida in the fall of 2007, and within months, it was also found in west-central north Florida (Hillsborough County). Incidence reached nearly 100% on some of the affected crops and caused complete yield losses on basil grown both in the field for fresh market and potted herbs market. Symptoms developed during transit on basil that appeared symptomless at harvest. Symptoms initially appeared as yellowing on the lower leaves that was typically delineated by the veins, although in some cases the entire leaf area of the leaf surface was affected. A gray, fuzzy growth was apparent on the abaxial leaf surface. Microscopic observation detected dichotomous branching, hyaline sporangiophores (220 to 750 × 4 to 9 µm) bearing single sporangia. Sporangia were light brown, ovoid to slightly ellipsoid, and measured 14 to 15 × 15 to 18 µm. Oospores were not observed. Leaves of potted basil plants and coleus (Solenostemon scutellarioides) were inoculated with a suspension containing 1 × 105 sporangia/ml and sprayed till runoff (approximately 15 ml per plant) with a hand-held pressurized aerosol canister. Plants were covered with a plastic bag for 24 h and maintained in the greenhouse under ambient conditions. Noninoculated plants served as controls. After 7 days, symptoms typical of downy mildew occurred only on the inoculated basil plants and sporulation was confirmed microscopically. The internal transcribed spacer regions of an isolate collected in Hendry County were sequenced bidirectionally. The consensus sequence was deposited into GenBank (Accession No. FJ346561). Sequence data matched (100% homology) with a Peronospora sp. reported on sweet basil in Switzerland (GenBank Accession No. AY884605) and was similar (99% homology) to an isolate (GenBank Accession No. DQ523586) reported on coleus, although inoculation to coleus failed to confirm pathogenicity on this host. The sequence data also distinguished the isolate from P. lamii (87% homology) previously reported to occur on basil. The pathogen was identified as a Peronospora sp. based on morphological characteristics and sequencing homology (1-3). References: (1) L. Belbahri et al. Mycol. Res. 109:1276, 2005. (2) S. Francis. CMI Descriptions of Pathogenic Fungi and Bacteria. No. 688. CMI, Kew, England, 1981. (3) A. McLeod et al. Plant Dis. 90:1115, 2006.

First Report of Uredo manilensis in the Western Hemisphere.

Crepe jasmine, Tabernaemontana divaricata (L.) R. Br. ex Roem. & Schult. (Apocynaceae), is a popular flowering shrub in South Florida. A native of Southeast Asia, it is one of approximately 100 ornamental species in the genus. In December 2007, rust was observed on the leaves of landscape plants in Key West and Miami. The rust has become prevalent and severely affects young and old leaves of plants in the landscape and in commercial nurseries. Leaf lesions begin as chlorotic flecks that expand into necrotic spots with orange-to-reddish brown, subepidermal uredinia; brown telia develop on the abaxial side of leaves. Urediniospores are one-celled, initially hyaline, minutely echinulate and spherical, turn dark orange, and measure (22) 24 to 29 (32) × (19) 21 to 24 (26) µm. Teliospores are (26) 29 to 36 (38) × (20) 22 to 26 (28) µm, two-celled, ellipsoidal to ovoid, echinulate, constricted at the septum, reddish brown, and have 0.8-µm thick spore walls; pedicels are 25 × 5.6 µm, persistent, and hyaline. Attributes for urediniospores are consistent with those from the original description of Uredo manilensis Syd. & P. Syd. on T. coronariae in Manila (2); however, there are no reports of a telial stage for this rust. Attributes for urediniospores of the South Florida fungus were also consistent with those on herbarium specimens of U. manilensis from the U.S. National Fungus Collection, also collected in Manila but from T. polygama (BPI Accession Nos. 0155269 and 0155270). Notably, these specimens contained telia that matched those found in South Florida. Subsequent comparisons were made with herbarium specimens of the three Puccinia spp. that have been reported on Tabernaemontana spp. (the U.S. National Fungus Collection or the Arthur Herbarium, Purdue University, West Lafayette, IN). Puccinia engleriana (five specimens from India, New Guinea, and the Philippines) differs from the BPI specimens of U. manilensis and the South Florida fungus by its bigger teliospores (32) 35 to 41 (45) × (21) 22 to 24 µm. P. tabernaemontana (six specimens from Uganda) has bigger urediniospores ([45] 34 to 41 × [34] 26 to 32 µm) and yellow-brown, poorly echinulated to almost smooth teliospores. The revised material of P. morobensis (type) was poor, but according to the original description (1) and notes found in the herbarium specimen, the teliospores (24 to 29 × 33 to 45 µm) and urediniospores are larger (23 to 28 × 29 to 35 µm) and the teliospores walls are finely and sparsely echinulated to sometimes smooth, and the pedicels are very short and fragile. A specimen of the South Florida fungus was deposited with the U.S. National Fungus Collections (BPI Accession No. TBA). To our knowledge, this is the first report of U. manilensis in the Western Hemisphere and the first time a telial stage (provisionally P. manilensis) has been recognized for the fungus. This disease has become a concern in South Florida for gardeners as well as producers who must now treat the crop with fungicides. References: (1) G. B. Cummins. Mycologia. 33:148, 1941. (2) H. Sydow, and P. Sydow. Ann. Mycol. 8:36, 1910.

First Report of Tar Spot on Orange Geiger, Cordia sebestena, Caused by Diatractium cordianum in Florida.

In July 2007, tar spot symptoms were observed on the leaves of orange Geiger, Cordia sebestena L. (Boraginaceae), in the landscape and a commercial nursery in Homestead, FL. The disease appears to be spreading and is locally severe. Symptoms were circular, slightly hypertrophied spots approximately 5 to 8 cm in diameter, which were slightly chlorotic on the abaxial surface and had numerous circular blackened stroma, 0.2 to 0.4 mm in diameter, on the adaxial surface. As leaves aged and yellowed, the areas around the spots remained pale green. Embedded in the stroma were numerous perithecia, 173 to 312 µm in diameter, circular to irregular in shape, with lateral necks as much as 200 µm long and 73 to 104 µm in diameter. Asci, 77 to 92 × 11 to 13 µm, contained elongate, two-celled ascospores, 50 to 61 × 3 to 5 µm that had a conspicuous constriction at the dividing cell wall. These dimensions and the pathogen's appearance matched closely with those published for Diatractium cordianum (Ellis & Kelsey) Syd (1). Young, symptomless leaves of C. sebestena were sprayed to runoff with a suspension of ascospores approximately 104 ml-1 that were harvested from affected leaves. Inoculated leaves were placed on water-saturated paper towels in petri plates and maintained in a growth chamber at 25°C with fluorescent light at 10 h day-1. Symptoms similar to those observed on affected trees in the landscape began to develop after 21 days and perithecia were evident after 28 days. An ITS 1, ITS 2, and 5.8s rDNA sequence was deposited in GenBank (Accession No. EU541488). A herbarium specimen was deposited at the U.S. National Fungus Collections (BPI No. 878441). This is a new host record for D. cordianum and is the first time the pathogen has been reported in the United States. Previous records were from Venezuela and several Caribbean islands, including Cuba and Jamaica. Symptoms of this disease have not been observed on Texas wild olive, Cordia boissieri, in close proximity to affected C. sebestena. P. F. Cannon (1) indicated that the disease had no economic impact. However, the conspicuous nature of symptoms on C. sebestena and the importance of this tree in the South Florida ornamental trade (2) suggest that this disease may become significant on the latter host. References: (1) P. F. Cannon. Mycol. Res. 92:327, 1989. (2) E. F. Gilman and D. G. Watson. Fact Sheet ST-182. Univ. Fla, Fla Coop Ext. Serv., 1993.

First Report of Bacterial Soft Rot on Vanda Orchids Caused by Dickeya chrysanthemi (Erwinia chrysanthemi) in the United States.

Vanda orchids are epiphytes grown for their attractive flowers by commercial producers and hobbyists throughout Florida. In August 2007, five Vanda hybrids, with an economic value of $150 each, were found at a nursery in central Florida with leaves that were macerated, brown, and water soaked. According to the growers, the plants were normal the previous day but symptoms developed rapidly. The plants were immediately removed from the greenhouse to prevent potential disease spread. Bacteria were isolated according to the method of Schaad et al. (1). Isolated bacteria grew at 37°C, were gram negative, degraded pectate, and produced phosphatase. MIDI (Sherlock version TSBA 4.10; Microbial Identification 16 System, Newark, DE) (SIM 0.906) identified the bacteria as Erwinia chrysanthemi (Dickeya chrysanthemi Burkholder et al. 1953) Samson et al. 2005. PCR was performed on the 16S rRNA gene (GenBank Accession No. EU526397) with primers 27f (5'-GAGAGTTTGATCCTG GCTCAG-3') and 1495r (5'-TACGGCTACCTTGTTACGA-3') (2). Subsequent DNA sequencing and GenBank search showed the isolated strain is 99% identical to that of Dickeya chrysanthemi. Four leaves each of six Vanda hybrids were inoculated by injecting approximately 150 µl of a bacteria suspension at 1 × 108 CFU/ml into each leaf. One plant was inoculated with water in each of four leaves. Plants were enclosed in plastic bags and returned to the greenhouse under 50% shade at 29°C day and 17°C night temperatures. Within 24 h, soft rot symptoms appeared on inoculated leaves. The water control appeared normal. D. chrysanthemi was reisolated and identified with the above method, thus Koch's postulates were fulfilled. To our knowledge, this is the first report of a soft rot caused by D. chrysanthemi on Vanda hybrids. Because of the popularity and high value of Vanda orchids, proper identification of this rapidly progressing bacterial disease is of great importance for the commercial producer and homeowner alike. References: (1) N. W. Schaad et al. Erwinia soft rot group. Page 56 in: Laboratory Guide for Identification of Plant Pathogenic Bacteria. 3rd ed. N. W. Schaad et al., eds. American Phytopathological Society. St. Paul, MN, 2001. (2) W. G. Weisburg. J. Bacteriol. 173:697, 1991.

First Occurrence of Anthracnose Caused by Colletotrichum gloeosporioides on Pitahaya.

Pitahaya, Hylocereus undatus Britt. & Rose, is a columnar, climbing cactus that produces a commercially important fruit. In December 2004, a new disease was found on the crop in Miami-Dade County, FL. Reddish brown lesions with conspicuous chlorotic haloes developed concentrically on the edges of vine ribs. Lesion centers became white and coalesced to rot much of the vine column, and in severe cases, only the vascular column in the vine center was not diseased. Salmon-colored spores and waxy, subepidermal acervuli, typically with setae and simple, short, erect conidiophores, were observed in lesion centers. Tissue from lesion margins was surface disinfested and plated on potato dextrose agar (PDA; Difco Laboratories, Detroit, MI). Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. was isolated from all samples. Colonies produced abundant conidia that were hyaline, one celled, straight, cylindrical, and averaged 14.7 × 5.0 µm with ranges of 12.5 to 17.5 × 3.8 to 7.5 µm (1). Cultural and morphological characteristics of isolates matched those for C. gloeosporioides except for appressoria and hyphopodia (1,2); pitahaya isolates had a spherical rather than lobed hyphopodia reported for C. gloeosporioides and averaged 10.9 (8.5 to 12.7) × 9.1 (7.1 to 10.3) µm. Internal transcribed spacer sequences for the pitahaya isolates were nearly identical (98% homology) to those for C. gloeosporioides isolates occurring on Euphatorium thymifolia in Thailand (GenBank Accession No. AY266393). Koch's postulates were examined in greenhouse trials at the Tropical Research and Education Center, Homestead, FL. Treatments consisted of a noninoculated control, four C. gloeosporioides isolates, and an Alternaria sp. All isolates came from symptomatic pitahaya tissue collected in Miami-Dade County. Fungi were grown on PDA for 7 days at 27°C. A sterile dissecting needle was used to gently pinprick the epidermis of the stem and 2-mm-diameter plugs of C. gloeosporioides, an Alternaria sp., or clean PDA were placed over wounds. Plants were placed in a plastic tent in a greenhouse where the temperature was held at 25°C, and free moisture was maintained on plant surfaces with a household humidifier for 48 h following inoculation. Two isolates of C. gloeosporioides were shown, in repeated greenhouse experiments, to cause reddish brown lesions with conspicuous chlorotic haloes that coalesced to rot much of the vine column, and Koch's postulates were completed with the reisolation of isolates that were used to inoculate plants. The age of vine segments had no significant effect on lesion development. To our knowledge, this is the first report of C. gloeosporioides as a pathogen of pitahaya. References: (1) J. A. Bailey and M. J. Jeger. Colletotrichum: Biology, Pathology and Control. CAB International, Wallingford, UK, 1992. (2) M. Du et al. Mycologia 97:641, 2005.

First Report of Fusarium Wilt Caused by Fusarium oxysporum on Roselle in the United States.

Roselle, Hibiscus sabdariffa var. sabdariffa, is an annual that is grown primarily for its inflated calyx, which is used for drinks and jellies. It is native from India to Malaysia, but was taken at an early date to Africa and is now widely grown in the tropics and subtropics (2). In late 2005, dying plants were noted by a producer in South Florida. Plants wilted, became chlorotic, and developed generally unthrifty, sparse canopies. Internally, conspicuous vascular discoloration was evident in these plants from the roots into the canopy. After 5 days on one-half-strength potato dextrose agar (PDA), salmon-colored fungal colonies grew almost exclusively from surface-disinfested 5 mm2 pieces of vascular tissue. On banana leaf agar, single-spored strains produced the following microscopic characters of Fusarium oxysporum: copious microconidia on monophialides, infrequent falcate macroconidia, and terminal and intercalary chlamydospores. Partial, elongation factor 1-α (EF1-α) sequences were generated for two of the strains, O-2424 and O-2425, and compared with previously reported sequences for the gene (3). Maximum parsimony analysis of sequences showed that both strains fell in a large, previously described clade of the F. oxysporum complex (FOC) that contained strains from agricultural hosts, as well as human clinical specimens (2; clade 3 in Fig. 4); many of the strains in this clade have identical EF1-α sequences. Strains of F. oxysporum recovered from wilted roselle in Egypt, O-647 and O-648 in the Fusarium Research Center collection, were distantly related to the Florida strains. We are not aware of other strains of F. oxysporum from roselle in other international culture collections. Roselle seedlings were inoculated with O-2424 and O-2425 by placing a mycelial plug (5 mm2, PDA) over a small incision 5 cm above the soil line and then covering the site with Parafilm. Parafilm was removed after 1 week, and plants were incubated under ambient temperatures (20 to 32°C) in full sun for an additional 5 weeks (experiment 1) or 7 weeks (experiment 2). Compared with mock-inoculated (wound + Parafilm) control plants, both O-2424 and O-2425 caused significant (P < 0.05) vascular disease (linear extension of discolored xylem above and below wound site) and wilting (subjective 1 to 5 scale); both isolates were recovered from affected plants. F. oxysporum-induced wilt of roselle has been reported in Nigeria (1) and Malaysia (4) where the subspecific epithet f. sp. rosellae was used for the pathogen. We are not aware of reports of this disease elsewhere. To our knowledge, this is the first report of F. oxysporum-induced wilt of roselle in the United States. Research to determine whether the closely related strains in clade 3 of the FOC are generalist plant pathogens (i.e., not formae speciales) is warranted. References: (1) N. A. Amusa et al. Plant Pathol. J. 4:122, 2005. (2) J. Morton. Pages 81-286 in: Fruits of Warm Climates. Creative Resource Systems, Inc., Winterville, NC, 1987. (3) K. O'Donnell et al. J. Clin. Microbiol. 42:5109, 2004. (4) K. H. Ooi and B. Salleh. Biotropia 12:31, 1999.

Frequency and diversity of fungi colonizing tissues of upland cotton.

A study of the mycoflora of upland cotton in Alabama was conducted throughout the 2000 and 2001 growing seasons. Plants were sampled at seedling, first bloom, full bloom, and maturity stages of development. Thirty-seven genera representing 58 species of fungi were isolated, including 9 species of Fusarium. Fusarium oxysporum, F. solani, and F. equiseti were the most common members of this genus occurring at all four sampling stages in both years. Eight species accounted for 67% of the total fungi isolated during the two-year study. Alternaria alternata was the most common fungus encountered, accounting for 19 and 10% of the total fungi isolated in 2000 and 2001, respectively. Twenty species of fungi are reported for the first time colonizing upland cotton tissues.

Interaction of Rotylenchulus reniformis with Seedling Disease Pathogens of Cotton.

The impact of 10 Fusarium species in concomitant association with Rotylenchulus reniformis on cotton seedling disease was examined under greenhouse conditions. In experiment 1, fungal treatments consisted of Fusarium chlamydosporum, F. equiseti, F. lateritium, F. moniliforme, F. oxysporum, F. oxysporum f.sp. vasinfectum, F. proliferatum, F. semitectum, F. solani, and F. sporotrichioides; Rhizoctonia solani; and Thielaviopsis basicola. The experimental design was a 2 x 14 factorial consisting of the presence or absence of R. reniformis and the 12 fungal treatments plus two controls in autoclaved field soil. In experiment 2, the same fungal and nematode treatments were examined in autoclaved or non-autoclaved soil. This experimental design was a 2 x 2 x 14 factorial consisting of field or autoclaved soil, presence or absence of R. reniformis, and the 12 fungal treatments plus two controls. In both tests, Fusarium oxysporum f. sp. vasinfectum, F. solani, R. solani, and T. basicola consistently displayed extensive root and hypocotyl necrosis that was more severe (P

Occurrence of Nigrospora Lint Rot Caused by Nigrospora oryzae on Cotton in Alabama.

During 2000 and 2001, a lint rot of cotton bolls (Gossypium hirsutum L.) was reported in the coastal region of Alabama when precipitation was 55% lower than the 5-year average. Bolls at an early stage of opening contained gray mycelium within the locules. At maturity, the lint within the infected locules was discolored, and the fibers were compact resulting in the characteristic "gray lock" sign and symptom attributed to Nigrospora oryzae (Berk. & Broome) Petch. Roots, petioles, leaves, and bolls when present were sampled at the seedling, first bloom, full bloom, and maturity stages of cotton development. A total of 640 sections of tissue (approximately 5 mm2) were surface sterilized for 20 s in 95% ethanol followed by 60 s in 0.525% NaOCl and aseptically plated on potato dextrose agar. Plates were incubated in the dark at 25°C for 3 to 10 days. N. oryzae was isolated at low frequencies from all plant tissues beginning at first bloom. Developing bolls at full bloom were colonized at a frequency of 48%. N. oryzae conidiophores were branched, flexuous, and pallid to brown with smooth walls 4 to 7 (5) µm thick. Conidiogenous cells were monoblastic, single, and 6 to 9 (7.5) µm in diameter. Conidia were single, smooth, broadly ellipsoidal, dark brown to black, single-celled, and 11 to 16 (14) µm in diameter (2). Principal component analysis was used to examine the relationship between disease incidence and weather parameters. Weather data was obtained from Auburn University Mesonet located in fields where the samples were collected. Principal components from weather data were ambient and soil maximum, minimum, and average temperature, maximum, minimum, and average relative humidity and precipitation. The first principal component, which is temperature, accounted for 61% of total joint variation among original observations. The second principal component, which was related to the moisture variables, accounted for 19% of the variation. The abundance of N. oryzae was correlated with the principal component factor moisture (r = -0.78**). The dry conditions experienced in this region were conducive to N. oryzae lint rot of cotton. This disease has been reported on cotton primarily in arid climates typical of the southwestern United States (1). To our knowledge, this is the first report of N. oryzae lint rot in the southeastern United States. References: (1) W. E. Batson. Boll rots. Pages 36-38 in: Compendium of Cotton Diseases. T. L. Kirkpatrick and C. S. Rothrock, eds. The American Phytopathological Society, St. Paul, MN. 2001. (2) M. B. Ellis. Dematiaceous Hyphomycetes, CAB, Kew, Surrey, England, 1971.

Temperature Effects on Race Determination in Heterodera glycines.

Currently there are 16 possible races for Heterodera glycines, and these are differentiated based on ability of a nematode population to develop on a set of four differential soybean genotypes. Because results are based on numbers of nematode females that develop to a specific stage rather than on the reproductive capability of these females, race determinations based on female indices may not represent results obtained after several reproductive cycles of H. glycines. Counting numbers of eggs and juveniles, and then developing corresponding indices, would allow reproduction to be considered in making race determinations. Our objectives were to compare the present race identification scheme for H. glycines based on female indices with those using egg and juvenile indices and to examine the effect of temperature on race designations using female, egg, and juvenile indices. Race designations for H. glycines populations from two locations in Illinois were determined at 20, 27, and 30 degrees C in a water bath. The numbers of females, eggs, and juveniles (at 19 days) were recorded, and an index based on each life stage was calculated. Race determinations based on female, egg, or juvenile indices were inconsistent when conducted at 20 degrees C, which demonstrates that this temperature is not suitable for identifying races of H. glycines. However race designations at 27 and 30 degrees C were consistent for all three indices. This indicates that counting females, eggs, or juveniles should be equally reliable when race determinations are conducted at these two temperatures, and choice of method would depend on investigator preference or research objective.