scholarly journals First Report of Puccinia xanthii on Sunflower in North America

Plant Disease ◽  
2002 ◽  
Vol 86 (5) ◽  
pp. 564-564 ◽  
Author(s):  
T. J. Gulya ◽  
L. D. Charlet
Keyword(s):  
South Africa ◽  
North America ◽  
Helianthus Annuus ◽  
Leaf Surface ◽  
Rust Fungi ◽  
First Report ◽  
Abaxial Leaf Surface ◽  
University Of Arizona ◽  
Plant Pathol ◽  
Size And Morphology

Puccinia xanthii Schwein., commonly known as cocklebur rust, is circumglobal on species of Xanthium and Ambrosia. This microcyclic rust has only been observed on oilseed sunflower (Helianthus annuus L.) in Australia (1) and on ornamental sunflowers in South Africa (4). In September 1999, large (4 to 10 mm), raised, chlorotic pustules were observed on the adaxial leaf surface of oilseed sunflower plants (Dekalb 3790) near Hettinger, ND. Telia were associated with the pustules on the abaxial leaf surface. No cocklebur (X. strumarium L.) plants were found in the field, but rust-infected cocklebur plants were collected several kilometers away. Approximately 10% of sunflower plants in the field were affected, and generally only one or two pustules were observed on one or two leaves per plant. In contrast, numerous leaves of cockleur plants were infected with 12 or more pustules. Teliospores from sunflower were brown, two-celled, and averaged 49 × 17 μm, with a distinctly thicker wall at the spore apex and a persistent pedicel averaging 40 μm long. Teliospores from cocklebur were morphologically similar to those from sunflower and averaged 46 × 16 μm. Size and morphology of teliospores from both hosts fit the description of P. xanthii (2). P. xanthii can be distinguished easily from the ubiquitous P. helianthi Schwein. because the latter has smaller telia (1 to 2 mm diameter) and produces wider teliospores (21 to 30 μm diameter). P. xanthii was not found in surveys of 20 other sunflower fields in southwestern North Dakota nor in 45 fields in eastern ND in 1999, nor was P. xanthii found in this or any other sunflower field in 2000 or 2001. To our knowledge, this is the first report of P. xanthii on cultivated or wild sunflower in North America. The relatively few pustules observed on oilseed sunflower agree with the observation that oilseed sunflowers are much less susceptible to P. xanthii (3) than Xanthium spp. References: (1) J. L. Alcorn and J. K. Kochman. Austral. Plant Pathol. Soc. Newsl. 5:33, 1976. (2) G. B. Cummins. Rust Fungi on Legumes and Composites in North America. University of Arizona Press, Tucson, 1978. (3) J. B. Morin et al. Can. J. Bot. 71:959, 1993. (4) Z. A. Pretorius et al. Plant Dis. 84:924, 2000.

scholarly journals First Report of Powdery Mildew of Kenaf Caused by Leveillula taurica in South Africa

Plant Disease ◽  
2001 ◽  
Vol 85 (8) ◽  
pp. 923-923
Author(s):  
W. J. Swart ◽  
J. Terblanche
Keyword(s):  
South Africa ◽  
Powdery Mildew ◽  
Seed Quality ◽  
Leaf Surface ◽  
Hibiscus Cannabinus ◽  
First Report ◽  
Leveillula Taurica ◽  
Abaxial Leaf Surface ◽  
Extensive Growth ◽  
Northwest Province

Kenaf (Hibiscus cannabinus L.) is a fast-growing, bamboo-like annual plant belonging to the Malvaceae. The stem, which ranges from 1.5 to 4 m, presents a source of high-quality cellulose fibers. The plant is being investigated in South Africa with a view to commercial production. In April 2001, at least 50% of 4- to 5-month-old kenaf plants grown from seed in trials near Rustenburg, Northwest Province, South Africa, were observed as having powdery mildew. Signs included extensive growth of white, superficial mycelium and emergent conidiophores on the abaxial leaf surface, followed by partial defoliation. On older leaves, the abaxial leaf surface was completely covered by powdery mildew, and chlorotic and necrotic patches were clearly visible on the adaxial surface. Symptoms were observed on all five planted cultivars (Everglades 41, Cuba 108, El Salvador, SF459, and Tainung 2), and no difference in disease severity was noted among cultivars. Leveillula taurica (Lév.) Arnaud (anamorph Oidiopsis taurica [Lév.] Salmon) was subsequently identified by the presence of endophytic mycelia, often branched conidiophores, and dimorphic conidia borne singly or in short chains (1). In 100 measurements of each type, pyriform conidia averaged 69 ± 5 × 18 ± 2 μm and cylindrical conidia averaged 62 ± 6 × 16 ± 2 μm. The teleomorph was not observed. The source of L. taurica for this reported outbreak is unknown, and powdery mildew was not observed in a field of mature cotton (Gossypium hirsutum L.) growing within 10 m of the kenaf plot. L. taurica was reported on kenaf in Texas in 1992 (2) and in Italy in 1995 (3). The pathogen can cause significant losses in seed yield and reduce seed quality in susceptible kenaf cultivars. Although L. taurica has been reported from Hibiscus sabdariffa in Egypt (4), to our knowledge this is the first report of the pathogen occurring on kenaf in Africa. References: (1) H. J. Boesewinkel. Bot Rev. 46:167, 1980. (2) C. G. Cook and J. L. Riggs. Plant Dis. 79:968, 1995. (3) S. Frisullo et al. Inf. Fitopatol. 45:37–41, 1995. (4) M. Khairy, et al. Phytopathol. Medit. 10:269–271, 1971.

scholarly journals First Report of Melampsora larici-populina on Populus spp. in Eastern North America

Plant Disease ◽  
2004 ◽  
Vol 88 (1) ◽  
pp. 85-85 ◽  
Author(s):  
L. Innes ◽  
L. Marchand ◽  
P. Frey ◽  
M. Bourassa ◽  
R. C. Hamelin
Keyword(s):  
North America ◽  
Ribosomal Rna ◽  
Leaf Surface ◽  
Hybrid Poplar ◽  
Western United States ◽  
Eastern North America ◽  
First Report ◽  
Melampsora Medusae ◽  
Abaxial Leaf Surface ◽  
Forest Biology

In September 2002, yellow spots were observed on the leaf surface of a hybrid poplar (Populus maximowiczii Henry × P. balsamifera L.) grown at the Berthier forest nursery (46°2′N, 73°11′W) in the St. Lawrence Valley (Lanaudière Region, Québec, Canada). Disease severity was low, but the pathogen was present on a hybrid that was previously thought to be resistant to Melampsora medusae Thuem, the only reported poplar rust in eastern North America. Uredinia typical of a Melampsora sp. were observed on the abaxial leaf surface. The observed urediniospores were longer (32 to 48 μm) than the expected range for M. medusae (23 to 35 μm) and possessed an apical bald spot; thick paraphyses were also observed. These characteristics are diagnostic of M. larici-populina Kleb (2). Samples were deposited in the National Mycological Herbarium of Canada (DAOM 232107 and 232108) and in the Quebec Forest Biology Herbarium (QFB14703 and 14704). DNA was extracted from uredinia, and the internal transcribed spacer (ITS) of the ribosomal RNA gene was amplified and sequenced (GenBank Accession Nos. AY429656 and AY429657). There was a 100% match between the two sequences obtained and that of M. larici-populina (GenBank Accession No. AY375267), but there was approximately 12% divergence with the ITS sequence of M. medusae (GenBank Accession No. AY375273-5). This is the first report of M. larici-populina in eastern North America. This fungus was reported on P. trichocarpa × P. deltoides hybrids in the western United States in the early 1990s (1). It appears that M. larici-populina can overwinter in Québec because it was observed again at the nursery in September 2003. The occurrence of M. larici-populina in eastern North America has direct implications for the poplar industry since the host specificities of M. medusae and M. larici-populina differ; P. balsamifera and P. maximowiczii are sensitive to M. larici-populina (3). Hybrids with P. balsamifera or P. trichocarpa components may be particularly at risk. References: (1) G. Newcombe and G. A. Chastagner. Plant Dis. 77:532, 1993. (2) J. Pinon. Eur. J. For. Pathol. 3:221, 1973. (3) J. Pinon. Silvae Genet. 41:25, 1992.

scholarly journals First Report of Phragmidium violaceum Infecting Himalaya and Evergreen Blackberries in North America

2005 ◽  
Vol 6 (1) ◽  
pp. 25 ◽  
Author(s):  
N. Osterbauer ◽  
A. Trippe ◽  
K. French ◽  
T. Butler ◽  
M. C. Aime ◽  
...  
Keyword(s):  
South Africa ◽  
Biological Control ◽  
New Zealand ◽  
North America ◽  
Biological Control Agent ◽  
Control Agent ◽  
First Report ◽  
Official Report

Phragmidium violaceum occurs on several species of Rubus, including R. armeniacus, R. fruticosus agg., and R. laciniatus, in Europe, South Africa, Iran, and Iraq, and has been introduced as a biological control agent for invasive blackberries in Australia, New Zealand, and Chile. To our knowledge, this is the first official report of P. violaceum infecting Himalaya and evergreen blackberries in North America. Accepted for publication 16 September 2005. Published 23 September 2005.

scholarly journals White Rust of Echinacea angustifolia and E. purpurea in North America Caused by a Pustula Species

Plant Disease ◽  
2014 ◽  
Vol 98 (6) ◽  
pp. 856-856
Author(s):  
L. J. du Toit ◽  
M. L. Derie
Keyword(s):  
North America ◽  
Plant Species ◽  
Leaf Surface ◽  
Consensus Sequence ◽  
Spore Suspension ◽  
Thick Wall ◽  
Echinacea Angustifolia ◽  
White Rust ◽  
Plastic Bags ◽  
Abaxial Leaf Surface

In 2012 and 2013, foliar symptoms were observed in certified organic, 2- to 4-ha crops of Echinacea angustifolia and E. purpurea in Grant and Klickitat counties, WA. White pustules were predominant on the abaxial leaf surface, increased in number, and coalesced on E. angustifolia, with 100% infection by the end of the season; in contrast, symptoms remained sparse on E. purpurea. Symptomatic leaves of each species were collected in May 2013 in Grant Co. Sori and sporangia were typical of those of white rust on Asteraceae caused by Pustula obtusata (1), originally named Albugo tragopogonis, then P. tragopogonis (4). Hyaline sporangia (n = 50) averaged 21 ± 2 × 20 ± 2 μm (16 to 25 × 16 to 24 μm) with a 2.6 ± 0.8 μm (1.0 to 4.0 μm) thick wall. Honey-colored to dark brown oospores were embedded in the abaxial leaf surface surrounding sori on older leaves. Oospores (n = 50) averaged 75 ± 7 × 63 ± 6 μm (60 to 96 × 52 to 76 μm) and 52 ± 4 × 51 ± 4 μm (44 to 65 × 44 to 60 μm) with (including protruberances) and without the hyaline outer wall, respectively. Sori were excised and shaken in 100 ml cold (4°C), deionized water at 400 rpm for 15 min on a gyrotory shaker. DNA extracted from the resulting spore suspension was subjected to a PCR assay using oomycete specific primers (2) to amplify the cytochrome oxidase subunit II (cox2) region of mtDNA (3). The 511-nt consensus sequence of the PCR product (GenBank Accession No. KF981439) was 98% identical to a cox2 sequence of A. tragopogonis from sunflower (Helianthus annuus) (AY286221.1), and 96% identical to cox2 sequences of P. tragopogonis (GU292167.1 and GU292168.1) (= P. obtusata) (1,2,4). Pathogenicity of the white rust isolate was confirmed by inoculating 49-day-old plants of E. angustifolia and E. purpurea with a spore suspension prepared as described above. One plant/species was placed in each of six clear plastic bags in a growth chamber at 18°C with a 12-h day/12-h night cycle for 48 h. Five replicate sets of one plant/species were each inoculated with 2.2 × 105 spores/ml on the adaxial and abaxial leaf surfaces using an airbrush (8 psi). One plant/species was sprayed with water as a control treatment. The plants were resealed in the bags for 48 h. After 7 days, white pustules were observed on at least one plant species. The plants were placed in plastic bags again overnight, and re-inoculated with 2.9 × 105 spores/ml. In addition, two sunflower plants at the 4-true-leaf stage were incubated in each of two plastic bags overnight, and inoculated with the spore suspension. Two additional sunflower plants were treated with water as control plants. All plants were removed from the bags after 48 h. White rust sori with sporangia developed on all inoculated Echinacea plants within 10 days, but not on control plants of either species, nor inoculated and non-inoculated sunflower plants, verifying that the pathogen was not P. helianthicola (1,2). Since the cox2 sequence was closest to that of a sunflower white rust isolate, the pathogen appears to be closer to P. helianthicola than P. obtusata, and may be a new Pustula species. To our knowledge, this is the first documentation of white rust on E. angustifolia and E. purpurea in North America. The severity of white rust on E. angustifolia highlights the need for effective management practices. References: (1) C. Rost and M. Thines. Mycol. Progress 11:351, 2012. (2) O. Spring et al. Eur. J. Plant Pathol 131:519, 2011. (3) S. Telle and M. Thines. PloS ONE 3(10):e3584, 2008. (4) M. Thines and O. Spring. Mycotaxon 92:443, 2005.

scholarly journals First Report of Powdery Mildew of Greenhouse Pepper Caused by Leveillula taurica in Canada

Plant Disease ◽  
1999 ◽  
Vol 83 (8) ◽  
pp. 781-781 ◽  
Author(s):  
R. F. Cerkauskas ◽  
J. Brown ◽  
G. Ferguson ◽  
S. Khosla
Keyword(s):  
Powdery Mildew ◽  
Leaf Surface ◽  
Morphological Characteristics ◽  
Chili Pepper ◽  
Width Ratio ◽  
Old Field ◽  
First Report ◽  
Leveillula Taurica ◽  
Plastic Bags ◽  
Abaxial Leaf Surface

In 1999, powdery mildew on cvs. Oberon and Triple 4 of greenhouse pepper (Capsicum annum L.) and cv. FireFlame of chili pepper was reported simultaneously in two commercial greenhouses at two separate locations, Leamington and Vineland, geographically separated by 290 km, in southern Ontario. Losses of 10 to 15% each in the 2 and 3.1 ha greenhouse pepper operations were noted. The greenhouse pepper industry in Canada consists of 89.4 ha with sales of $43.6 million (Canadian). Lesions appeared as a white, powdery coating on the abaxial leaf surface only, generally on the lower foliage of pepper plants, while diffuse chlorotic spots were present at corresponding locations on the adaxial surface. In chili pepper, this chlorosis was restricted to interveinal tissue, causing the leaves to have a somewhat netted appearance. In some cases, pale yellow spots appeared on the adaxial portion of the affected foliage during later stages of disease development. No cleistothecia were observed. Pyriform and cylindrical, hyaline, single-celled conidia were present in equal numbers. Both conidia had a network of crests and granules containing tiny, thornlike projections on the surface. These projections were also evident on the lower half of conidiophores. Pyriform conidia ranged in length from 61.6 to 84.0 μm (mean = 70.8, SE = 0.7) and in width from 14.0 to 25.8 μm (mean = 21.1, SE = 0.4, n = 50), with a mean length to width ratio of 3.4. Cylindrical conidia ranged in length from 54.9 to 80.1 μm (mean = 66.3, SE = 0.9) and in width from 15.7 to 24.1 μm (mean = 18.6, SE = 0.3, n = 50), with a mean length to width ratio of 3.1. Short conidial chains borne on conidiophores consisted of a pyriform conidium first followed by cylindrical conidium. Stomatal penetration and extensive endophytic mycelial growth in the mesophyll layer were evident in foliar tissue cleared with glacial acetic acid:EtOH (1:2) and stained with lactophenol cotton blue. To confirm pathogenicity, conidia from infected pepper leaves were dusted onto the water-misted abaxial leaf surface of 41-day-old greenhouse pepper cvs. Cubico and Edison, and onto the similarly treated adaxial leaf surface of 58-day-old field pepper cv. Renegade. Plants were enclosed in plastic bags for 24 h on a bench. Control plants were treated identically but not inoculated. Inoculated plants developed foliar powdery mildew symptoms, including sporulation similar to that of naturally infected plants. Occurrence of the fungus on the abaxial surface of pepper foliage, presence of endophytic mycelium, and the morphological characteristics of the imperfect state confirm the identity of the fungus. This is the first report of Leveillula taurica (Lév.) G. Arnaud on pepper in Canada. Reference: J. Palti. Bot. Rev. 54:423, 1988.

scholarly journals First Report of Powdery Mildew on Tomato Caused by Oidium neolycopersici in Venezuela

Plant Disease ◽  
2007 ◽  
Vol 91 (7) ◽  
pp. 910-910 ◽  
Author(s):  
J. O. Montilla ◽  
M. S. González ◽  
D. Renaud
Keyword(s):  
Powdery Mildew ◽  
Leaf Surface ◽  
Distinct Species ◽  
Oidium Neolycopersici ◽  
First Report ◽  
Physalis Peruviana ◽  
Infected Tomato ◽  
White Mycelium ◽  
Foliar Tissue ◽  
Plant Pathol

During 2004 and 2005, a powdery mildew was observed in tomato (Lycopersicon esculentum Mill. cv. Rio Grande) fields in several states in Venezuela. Symptoms included development of patches of dense white mycelium, predominantly on the upper leaf surface. Leaves in the middle and lower canopies were the most affected. Similar symptoms sometimes were observed on stems. The foliage of infected plants turned yellow and showed necrosis followed by desiccation and rapid defoliation. Microscopic examination revealed the presence of typical structures of the Oidium genus. Hyphae were hyaline and septate. Conidiophores were unbranched, erect, measured 51 to 108 (80) μm, and consisted of 3 or 4 cells. Conidia were hyaline, ellipsoidal to ovoidal, and measured 16 to 43 (30) × 12 to 22 (16) μm. Conidia were produced singly, without fibrosin bodies. Conidial polar germination was common. Appressoria were lobed. The sexual stage was not found. The fungus was identified as Oidium neolycopersici, recently recognized as a distinct species (1,2). Conidia from infected tomato leaves were shaken onto leaves of 10 plants of L. esculentum and L. pimpinellifolium (Jusl.) Mill. and five plants of a weed (Physalis peruviana L.). Noninoculated plants served as a control. Symptoms that developed on all inoculated plants were similar to those of plants naturally infected. Within 7 to 8 days, symptoms in L. esculentum consisted of small colonies that quickly covered large portions of foliar tissue. L. pimpinellifolium showed small and localized symptoms after 10 days and P. peruviana showed symptoms after 15 days. To our knowledge, this is the first report of O. neolycopersici in Venezuela. References: (1) H. Jones et al. Mol. Plant Pathol. 2:303, 2001. (2) L. Kiss et al. Mycol. Res. 105:684, 2001.

scholarly journals First Report of Pseudonectria buxi Causing Volutella Blight on Boxwood (Buxus sp.) in Beijing, China

Plant Disease ◽  
2014 ◽  
Vol 98 (9) ◽  
pp. 1282-1282 ◽  
Author(s):  
F. Shi ◽  
T. Hsiang
Keyword(s):  
North America ◽  
Room Temperature ◽  
Infection Process ◽  
Fusarium Spp ◽  
Adaxial Surface ◽  
First Report ◽  
Plastic Bags ◽  
Plant Pathol ◽  
Beijing China ◽  
Acta Botanica

Pseudonectria buxi (also called Volutella buxi) is a fungal pathogen that causes a disease of boxwood (Buxus spp.). This disease has been reported in several countries in Europe and North America, and has been traditionally considered the primary cause of boxwood decline (1), although box blight caused by Cylindrocladium buxicola has claimed notoriety because of its recent introduction to North America. In August 2013, symptoms resembling Volutella blight were observed at a park in Haidian District, Beijing, China, on leaves and stems of Korean boxwood (B. sinica var. insularis). The plants were still alive, but diseased leaves and twigs were yellowed and showed dieback. Symptoms were common on boxwood throughout this park, and the disease was also seen in other nearby areas. Pink sporodochia were observed on some yellowed leaves and stems. Diseased tissues (stems and leaves) were collected, cut into 1 mm2 pieces, surface sterilized in 1% sodium hypochlorite for 1 min, and placed on potato dextrose agar. After 3 days of incubation at room temperature, white fluffy mycelia were seen. The middle of the colonies turned pink by 7 days, and conidia produced on verticillately branched conidiophores in these pink areas were elliptical, 6 to 9 × 2 to 2.5 μm. DNA was extracted from one colony containing spores and mycelium, and a portion of the beta-tubulin gene was amplified using primers designed from highly conserved regions (5′-AACAACTGGGCCAAGGGTC, 5′-GAAGAGTTCTTGTTCTGGA) (3). The 676-bp amplicon was sequenced (GenBank Accession No. KJ755987), and the top matches were two isolates of P. buxi (KC819609 and DQ522522) with identities of 566/567 bp (99.8%) and 551/567 bp (97.2%), respectively. The next best matches were at 92% for Fusarium spp. For inoculation, four pots of 2-year-old healthy B. sinica var. insularis × B. sempervirens cv. Green Velvet were used. As wounds are required for the infection process (2,3), two parallel light scratches were made using needles on adaxial surface of three leaves per plant. One plant was only sprayed with water until runoff, while the other three plants were sprayed with a spore suspension (106 spores/ml) of P. buxi until runoff, covered with plastic bags, and placed at 25°C. After 3 days, pink sporodochia were observed on inoculated wounded leaves, but not on non-wounded leaves. By 10 days, inoculated wounded leaves turned yellow and became covered with sporodochia all over the adaxial surface, and on wound sites on the adaxial surfaces. No signs or symptoms were observed on either non-wounded inoculated leaves or on plants sprayed only with water. P. buxi was re-isolated from the diseased leaves but not the water-treated leaves, to successfully complete Koch's postulates. To the best of our knowledge, this is the first report of P. buxi causing Volutella blight on boxwood in China. References: (1) J. L. Bezerra. Acta Botanica Neerlandica 12:58, 1963. (2) B. Henricot et al. Plant Pathol. 49:805, 2000. (3) F. Shi and T. Hsiang. Eur. J. Plant Pathol. 138:763, 2014.

scholarly journals First Report of Pyrenophora tritici-repentis Race 5 from North America

Plant Disease ◽  
1999 ◽  
Vol 83 (6) ◽  
pp. 591-591 ◽  
Author(s):  
S. Ali ◽  
L. J. Francl ◽  
E. D. De Wolf
Keyword(s):  
United States ◽  
North America ◽  
North Africa ◽  
The United States ◽  
Tan Spot ◽  
Research Station ◽  
First Report ◽  
Pyrenophora Tritici Repentis ◽  
Virulence Pattern ◽  
Plant Pathol

Tan spot, caused by Pyrenophora tritici-repentis, is an important foliar disease of wheat worldwide. The fungus produces two distinct symptoms, necrosis (nec) and chlorosis (chl), on susceptible wheat genotypes. Fungal isolates have been grouped into five races based on their ability to induce necrosis and/or chlorosis on differentials Glenlea, Katepwa, 6B365, and Salamouni (1). Moreover, the isolates were designated on their ability to induce necrosis and chlorosis as follows: nec+chl+ (necrosis and chlorosis), nec+chl- (necrosis only), nec-chl+ (chlorosis only), and nec-chl- (neither symptom). Races 3 and 5 induce extensive chlorosis (nec-chl+) on 6B365 and Katepwa, respectively. Race 5 was reported on durum from North Africa. Races 1 to 4 were described from North America (1,2). During 1998, a survey of durum fields was conducted in the primary durum-growing area of North Dakota to assess the virulence pattern of P. tritici-repentis. Fifty-two single-spore isolates were obtained from diseased leaves. The isolates were evaluated for their virulence by inoculating them individually onto 15 seedlings of each wheat differential in the greenhouse. Forty-nine of 52 isolates were grouped as race 1 (nec+chl+) and three isolates, obtained from the Langdon Experiment Research Station, were grouped as race 5 (nec-chl+). Race 5 isolates were evaluated three times and consistently induced extensive chlorosis on Katepwa. This is the first report of the occurrence of race 5 outside of North Africa. This race may threaten wheat in the United States, so cultivars and germplasm should be evaluated for resistance. More isolates are under investigation to obtain a comprehensive virulence pattern of the pathogen population in the United States. References: L. Lamari and C. C. Bernier. Can. J. Plant Pathol. 11:49, 1989; (2) L. Lamari et al. Can. J. Plant Pathol. 17:312, 1995

scholarly journals First Report of White Rust of Gerbera Caused by Albugo tragopogonis in North America

Plant Disease ◽  
1997 ◽  
Vol 81 (2) ◽  
pp. 228-228 ◽  
Author(s):  
G. L. Vazquez ◽  
M. J. Aquino ◽  
M. T. Norman ◽  
F. A. Martinez ◽  
R. V. Sandoval ◽  
...  
Keyword(s):  
New Zealand ◽  
North America ◽  
New Disease ◽  
Gerbera Jamesonii ◽  
Common Ragweed ◽  
First Report ◽  
White Rust ◽  
Leaf Surfaces ◽  
Plant Pathol ◽  
Puccinia Horiana

In October, 1995, in Villa Guerrero, Mexico, white erumpent sori were detected on the undersurfaces of leaves of a bed of African daisy (Gerbera jamesonii H. Bolus ex J. D. Hook.). The white sori on the undersurfaces of leaves corresponded to chlorotic spots on the upper leaf surfaces. All gerbera plants examined were severely diseased. The gerbera planting was adjacent to a planting of chrysanthemums with symptoms of white rust caused by Puccinia horiana Henn. Symptoms on the leaves of the two crops looked similar, and therefore P. horiana was suspected of causing both diseases. However, when subepidermal sori (pustules) on Gerbera plants were examined microscopically, erumpent chains of round to cylindrical, hyaline to pale yellow sporangiospores borne on short club-shaped sporangiophores were found. The sporangiospores are typical of Albugo tragopogonis (Pers.) S. F. Gray, and it was concluded that the white rust found on gerbera in Villa Guerrero, Mexico, was caused by A. tragopogonis. This disease was reported on gerbera from Australia and New Zealand in 1965 (1) and from Spain in 1977 (2). Other hosts of A. tragopogonis include members in the genera Pericallis (cineraria), Centaurea (dusty miller, basket flower, cornflower, bachelor's-buttons), Ambrosia (common ragweed), Tragopogon (salsify), Antennaria (everlasting, pussytoes), Artemisia (wormwort, mugwort), Cirsium (thistle), Matricaria (false chamomile, pineapple weed), Iva (marshelder), Parthenium (guayule, American feverfew), and Xanthium (common cocklebur, spiny cocklebur). This is the first report of white rust of gerbera caused by A. tragopogonis in North America, and may represent a new disease problem for species of important floral crops in the future. References: (1) R. F. Doepel. J. Agric. West. Aust. Ser. 4 6:439, 1965. [Rev. Appl. Mycol. 45:80, 1966] (2) H. P. Plate and H. Kruber. Nachrichtenbl. Dtsch. Pflanzen-schutzdienst (Berlin) 29(11):169, 1977. [Rev. Plant Pathol. 57:204, 1978]

scholarly journals First Report of Uromyces striatus on White Sweetclover in Kansas

Plant Disease ◽  
2002 ◽  
Vol 86 (12) ◽  
pp. 1404-1404 ◽  
Author(s):  
D. L. Stuteville
Keyword(s):  
North America ◽  
Medicago Sativa ◽  
Plant Introduction ◽  
The United States ◽  
First Report ◽  
Medicago Lupulina ◽  
University Of Arizona ◽  
Causal Fungus ◽  
Pathogenicity Tests ◽  
Longitudinal Pattern

Rust was observed on leaves and stems of Melilotus alba Medik. plants in Riley County, Kansas, in November 1999. Rust reoccurred during the summers of 2000 and 2001. Uredinia were orange to reddish brown and predominately hypophyllous. Infected leaves wilted and abscised prematurely. Urediniospores were one-celled, globoid or broadly ellipsoid, and measured 20 to 25 × 18 to 22 μm. Walls were 1.0 to 1.2 μm thick, echinulate, and with three to five (mostly four) pores. Pores were equatorial, or nearly so, in approximately one half of the spores examined and scattered in the other half. Telia occurred in the fall, were sparse, amphigenous, exposed, and much darker than uredinia. Teliospores were single-celled, ovoid, subglobose or ellipsoidal, and measured 18 to 25 × 15 to 21 μm. Wall thickness was 1.3 to 2 μm. Walls had ridges approximately 1 μm wide, 2 μm apart, and arranged in a longitudinal pattern as shown in photographs of Uromyces striatus (2). Pedicels were hyaline, fragile, and short. Pathogenicity tests were conducted in growth chambers (4) with monouredinial isolate K-SC-R1 from M. alba. Pots containing plants of 80 USDA Plant Introduction (PI) core accessions representing 18 Melilotus spp. were evaluated. Total accessions tested per species were: 22 M. alba, 2 M. altissimus, 3 M. dentata, 2 M. elegans, 1 M. hirsutus, 4 M. indica, 2 M. infestus, 2 M. italica, 25 M. officinalis, 2 M. polonicus, 2 M. segetalis, 2 M. siculus, 2 M. speciosus, 2 M. spicatus, 1 M. suaveolens,2 M. sulcatus, 2 M. tauricus, and 2 M. wolgicus. Various amounts of rust developed on plants of 79 accessions; no plants of M. indica PI 234674 exhibited signs of rust. A host range study of an isolate of U. striatus from alfalfa (4) included these 18 Melilotus species; 10 were hosts. Therefore, the reactions of Medicago accessions to isolate K-SC-R1 were evaluated. These included nine alfalfa germ plasm sources representing the diversity in North American alfalfas and the cvs. Saranac and Moapa 69, which are commonly used susceptible controls in alfalfa rust evaluations. No rust resulted on any entry of Medicago sativa subsp. sativa. A few scattered, small, open uredinia occurred on plants of Medicago sativa subsp. falcata (‘WISFAL’ PI 560533). Of 11 Medicago lupulina PI accessions inoculated, rust resulted only on a few plants of PI 269926. All M. alba plants included as susceptible controls in all tests became heavily rusted. The causal fungus fits U. striatus Schroet. as described by uredinologists who disregard urediniospore pore position in this species. For example, illustrations of U. striatus urediniospores by Savulescu (3) show scattered pores, however, descriptions of U. striatus Schroet. in North America (1,2) specify equatorial pores. To my knowledge, this is the first report of scattered pores in U. striatus urediniospores in the United States. However, an examination of urediniospores from heavily rusted alfalfa plants collected in 2001 near Manhattan, KS and from isolate KR1 (4) also revealed urediniospores with variously distributed pores. U. striatus was reported on M. alba in Florida in 2001. References: (1) G. B Cummins. Rust Fungi on Legumes and Composites in North America. University of Arizona Press, Tucson, 1978. (2) J. A. Parmelee. Can. J. Bot. 40:491, 1962. (3) T. Savulescu. Monografia Uredinalelor din Republica Populara Romana. II. Acad. Repub. Pop. Rom. 1953. (4) D. Z. Skinner and D. L. Stuteville. Plant Dis. 79:456, 1995.

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