scholarly journals First Report of Root-Knot Nematode Meloidogyne enterolobii on Cockscomb (Celosia argentea var. cristata) in Taiwan

Plant Disease ◽  
2021 ◽  
Author(s):  
Jo Tzu Ho ◽  
Che-Chang Liang ◽  
P. Janet Chen
Keyword(s):  
United States ◽  
18S Rdna ◽  
The United States ◽  
Root Knot Nematode ◽  
First Report ◽  
Meloidogyne Enterolobii ◽  
Celosia Argentea ◽  
Pathogenicity Tests ◽  
Primer Sets ◽  
Coii Region

Cockscomb (Celosia argentea) is commonly found in subtropical and temperate zones of Africa, South America and South East Asia, and is a popular ornamental plant in the family Amaranthaceae. Cockscomb has been known to contain antiviral proteins, betalains, and anthocyanin, which can be applied in beneficial ways (2). In September 2020, a cockscomb plant (Celosia argentea var. cristata) showing typical galling root symptoms likely infected by root-knot nematodes (Meloidogyne sp.) was collected from a garden in Taichung, Taiwan, and a quick exam of several individuals using MK7F/R primers (7) indicating they were M. enterolobii. Nematode population was established from a single egg mass and was later used for species identification and pathogenicity tests. Five perineal patterns of mature females from the single female population show round to oval shapes with weak lateral lines. Dorsal arches are moderate to high, almost squared, with the smooth ventral striae. Second-stage juveniles are vermiform and have a slender tail, tapering to rounded tip with distinct hyaline region at the tail terminus. Morphological measurements of 28 J2s revealed body length = 457.2 ± 20.6 (416.1-506.9) μm, body width = 16.0 ± 2.0 (13.4-20.3) μm, stylet length = 14.7 ± 0.5 (13.9-15.9) μm, dorsal gland orifice to the stylet base = 4.0 ± 0.5 (2.0-4.8) μm, and tail length = 56.0 ± 3.8 (47.4-60.3) μm. Female perineal patterns and morphometric data are similar to the original description of Meloidogyne enterolobii (9). DNA purified from approximately 1500 juveniles using GeneMark Tissue & Cell Genomic DNA Purification Kit (GeneMark, Taiwan) was used to amplify 18S rDNA fragment, D2-D3 expansion segments of 28S rDNA, and a COII region on mtDNA with primer sets 1A/MelR, D2A/D3B, and C2F3/1108, respectively (4,5,6). The 18S rDNA sequence (OK076893) of this study shares 99.94% nucleotide identity with those of M. enterolobii isolated from the United States (KP901058) and China (MN832688). D2D3 sequence of haplotype 1 (OK076898) shows 100% identity to those of M. enterolobii from China (MT193450) and Taiwan (KP411230). Sequence of haplotype 2 (OK076899) shows 99.86% identity to those of M. enterolobii from the United States (MN809527) and China (MN269945). Sequence of the COII region (OK086042) show 99.86% identity to that of M. enterolobii from China (MN269945). Phylogenetic trees of the three gene sequences were plotted following Ye et al.(10), revealing that the newly described root-knot nematode on Cockscomb is grouped with other M. enterolobii isolates. DNA fragment amplified by primer sets Me-F/R(3) and MK7F/R specifically targeting of M. enterolobii yielded 236 bp and 520 bp, respectively. Pathogenicity tests were assayed, from July to September 2021, on three-week-old nematode-free cockscomb plant directly germinated from seeds of SkyStar® (ASUSA SPIKE SEEDS, Taipei, Taiwan) planted in a 10.5 cm diameter pot filled with 600 ml sterilized peat moss: sand (1:1, v/v) soil in a 28℃walk-in chamber. Nematode eggs were extracted using 0.05% NaoCl as described by Vrain(8), and cockscomb plants (n=3) were inoculated by adding 6000 eggs (10 eggs/ cm3). Cockscomb plants treated with water were used as mock controls. Rf value of the inoculated plants were determined by the method of Belair and Benoit (1) 45 days after inoculation, and the average was 4.13. No galls were observed on the roots of control plants. The results confirmed that cockscomb is the new host of M. enterolobii. To the best of our knowledge, this is the first report of M. enterolobii on Celosia argentea var. cristata in Taiwan.

scholarly journals First Report of Root-Knot Nematode Meloidogyne enterolobii on Poinsettia ‘Luv U Pink’ in Taiwan

Plant Disease ◽  
2021 ◽  
Author(s):  
Che-Chang Liang ◽  
P. Janet Chen
Keyword(s):  
United States ◽  
18S Rrna ◽  
The United States ◽  
18S Rrna Gene ◽  
Rrna Gene ◽  
First Report ◽  
Meloidogyne Enterolobii ◽  
Mock Control ◽  
Haplotype 1 ◽  
Coii Region

Poinsettia (Euphorbia pulcherrima Willd. ex Klotzsch.), originated in southern Mexico and northern Guatemala, is the most valuable potted flowering plant in the spurge family (Euphorbiaceae). The European Union and the United States are two biggest poinsettia markets (Taylor et al. 2011), with a wholesale value of $153 million in the United States in 2019. Root knot galls of poinsettia ‘Luv U Pink’ were collected from a production greenhouse located in Nantou County, Taiwan in March 2021. No aboveground symptoms were observed. A nematode population was established from a single female and used for identification and the Koch’s postulate. The perineal patterns of randomly picked 5 females are round or ovoid with moderate to high dorsal arches, but no distinct lateral lines, ventral striae are fine and smooth. The Morphometric characters of second-stage juvenile include: a vermiform body shape, tail narrow and tapering with rounded tail tips, and a distinct hyaline tail end. Measurements of 20 J2 are as follows: body length, 430 (398 - 473) μm; body width, 15.4 (13.4 - 17.8) μm; stylet length,13.4 (13.0 - 14.0) μm; dorsal esophageal gland orifice to basal knob, 3.4 (2.8 - 3.9) μm; tail length, 52.9 (47.6 - 62.2) μm. All morphometric data were consistent with the original description of Meloidogyne enterolobii (Yang and Eisenback 1983). Nematode DNA was extracted using GeneMark Tissue & Cell Genomic DNA Purification Kit (GeneMark, Taiwan) from approximately 1500 J2 and used for amplification of 18S rRNA gene, a D2-D3 region of 28S rRNA gene, and a mtDNA COII region with primer sets 1A/MelR, D2A/D3B, and C2F3/1108, respectively (Power and Harris 1993, Subbotin et al. 2006, Tigano et al. 2005). The sequence of 18S rRNA gene (accession no. MZ948800 haplotype 1 and MZ955998 haplotype 2), haplotype 1 shared 100% identity with that of M. enterolobii from the United States (KP901058) and China (MN832688); haplotype 2 shared 99.8% identity with that of KP901058 and MN832688. The sequence of the D2-D3 region (MZ955995) shared 99% identity with that M. enterolobii from the United States (KP901079). Sequence of the COII region (MZ964625) also shared 99% identity with that of M. enterolobii from the United States (AY446975) and China (MN840970). Phylogenetic trees of the three gene sequences plotted as described by Ye et al. (2021) revealed that the newly described nematode was grouped with M. enterolobii. Sequence analysis of two fragments: 236 bp and 520 bp amplified with gene specific primers Me-F/R and MK7F/R, respectively (Long et al. 2006, Tigano et al. 2010) also confirmed the identity of M. enterolobii. To measure the reproductive factor (Rf), the Poinsettia ‘Luv U Pink’ seedlings with eight true leaves were transplanted into three 12-cm diameter pots each containing 6000 eggs or water (mock control). Forty-five days after inoculation, the average Rf value of three inoculated plants was 6, and no galls were observed on mock control plant roots, confirming that poinsettia is the host of M. enterolobii. M. enterolobii has been reported in several Euphorbia species, including E. heterophylla, E. prostrata, E. punicea and E. tirucalli (Han et al. 2012, Rich et al. 2009). To the best of our knowledge, this is the first report of M. enterolobii infecting E. pulcherrima ‘Luv U Pink’. 

scholarly journals First Report of Web Blight on Yellow-Sage (Lantana camara) Caused by Rhizoctonia solani in Europe

Plant Disease ◽  
2003 ◽  
Vol 87 (7) ◽  
pp. 875-875 ◽  
Author(s):  
A. Garibaldi ◽  
A. Minuto ◽  
D. Bertetti ◽  
R. Nicoletti ◽  
M. L. Gullino
Keyword(s):  
United States ◽  
Rhizoctonia Solani ◽  
The United States ◽  
The Philippines ◽  
Lantana Camara ◽  
First Report ◽  
Leaf Spots ◽  
Entire Plant ◽  
Pathogenicity Tests ◽  
Web Blight

Lantana camara is increasingly grown in northern Italy as a potted plant and contributes to the diversification of offerings in the ornamental market. During the spring of 2001, selections of L. camara cuttings growing at a commercial farm located at Albenga (Riviera coast) exhibited tan leaf spots of irregular size and shape. Spots were at first isolated, 4 to 8 mm in diameter, and later coalesced and affected the entire plant. Heavily infected leaves, stems, and branches became blighted and were killed. Infected rooted cuttings also eventually died. Diseased cuttings showed a progressive reduction (to less than 20%) in rooting ability. Isolations from infected leaves and stems on potato dextrose agar (PDA), supplemented with 100 mg/liter of streptomycin sulphate, consistently yielded a fungus with mycelial and cultural characteristics resembling Rhizoctonia solani. The fungal isolates were further characterized as R. solani Kühn AG-4 based on hyphal anastomoses with several AG-4 tester isolates. Pathogenicity tests were performed by placing 5-day-old-fungal mycelial plugs, grown on PDA, at the base of five healthy yellow-sage stems and holding plants in a dew chamber at 18 to 22°C. After 2 days, foliage blight appeared on leaves of inoculated plants, and after 3 days, stems also became infected and entire plants wilted. Five noninoculated plants remained healthy. The fungal pathogen was reisolated from all inoculated plants. R. solani has been observed on L. camara in the United States (1) and the Philippines (2). To our knowledge, this is the first report of R. solani on L. camara in Europe. References: (1) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St. Paul, MN, 1989. (2) F. T. Orillo and R. B. Valdez. Philipp. Agric. A. 42:292, 1958.

scholarly journals First Report of Postharvest Fruit Rot in Persimmon Caused by Phacidiopycnis washingtonensis in Italy

Plant Disease ◽  
2010 ◽  
Vol 94 (6) ◽  
pp. 788-788 ◽  
Author(s):  
A. Garibaldi ◽  
D. Bertetti ◽  
M. T. Amatulli ◽  
M. L. Gullino
Keyword(s):  
United States ◽  
Its Region ◽  
The United States ◽  
Fruit Rot ◽  
Diospyros Kaki ◽  
Pathogenicity Test ◽  
Conidial Suspension ◽  
First Report ◽  
Pathogenicity Tests ◽  
Phacidiopycnis Washingtonensis

Persimmon (Diospyros kaki L.) is widely grown in Italy, the leading producer in Europe. In the fall of 2009, a previously unknown rot was observed on 3% of fruit stored at temperatures between 5 and 15°C in Torino Province (northern Italy). The decayed area was elliptical, firm, and appeared light brown to dark olive-green. It was surrounded by a soft margin. The internal decayed area appeared rotten, brown, and surrounded by bleached tissue. On the decayed tissue, black pycnidia that were partially immersed and up to 0.5 mm in diameter were observed. Light gray conidia produced in the pycnidia were unicellular, ovoid or lacriform, and measured 3.9 to 6.7 × 2.3 to 3.5 (average 5.0 × 2.9) μm. Fragments (approximately 2 mm) were taken from the margin of the internal diseased tissues, cultured on potato dextrose agar (PDA), and incubated at temperatures between 23 and 26°C under alternating light and darkness. Colonies of the fungus initially appeared ash colored and then turned to dark greenish gray. After 14 days of growth, pycnidia and conidia similar to those described on fruit were produced. The internal transcribed spacer (ITS) region of rDNA was amplified using the primers ITS4/ITS6 and sequenced. BLAST analysis (1) of the 502-bp segment showed a 100% similarity with the sequence of Phacidiopycnis washingtonensis Xiao & J.D. Rogers (GenBank Accession No. AY608648). The nucleotide sequence has been assigned the GenBank Accession No. GU949537. Pathogenicity tests were performed by inoculating three persimmon fruits after surface disinfesting in 1% sodium hypochlorite and wounding. Mycelial disks (10 mm in diameter), obtained from PDA cultures of one strain were placed on wounds. Three control fruits were inoculated with plain PDA. Fruits were incubated at 10 ± 1°C. The first symptoms developed 6 days after the artificial inoculation. After 15 days, the rot was very evident and P. washingtonensis was consistently reisolated. Noninoculated fruit remained healthy. The pathogenicity test was performed twice. Since P. washingtonensis was first identified in the United States on decayed apples (2), ‘Fuji’, ‘Gala’, ‘Golden Delicious’, ‘Granny Smith’, ‘Red Chief’, and ‘Stark Delicious’, apple fruits also were artificially inoculated with a conidial suspension (1 × 106 CFU/ml) of the pathogen obtained from PDA cultures. For each cultivar, three surface-disinfested fruit were wounded and inoculated, while three others served as mock-inoculated (sterile water) controls. Fruits were stored at temperatures ranging from 10 to 15°C. First symptoms appeared after 7 days on all the inoculated apples. After 14 days, rot was evident on all fruit inoculated with the fungus, and P. washingtonensis was consistently reisolated. Controls remained symptomless. To our knowledge, this is the first report of the presence of P. washingtonensis on persimmon in Italy, as well as worldwide. The occurrence of postharvest fruit rot on apple caused by P. washingtonensis was recently described in the United States (3). In Italy, the economic importance of the disease on persimmon fruit is currently limited, although the pathogen could represent a risk for apple. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) Y. K. Kim and C. L. Xiao. Plant Dis. 90:1376, 2006. (3) C. L. Xiao et al. Mycologia 97:473, 2005.

scholarly journals First Report of Clubroot on Canola Caused by Plasmodiophora brassicae in North Dakota

Plant Disease ◽  
2014 ◽  
Vol 98 (10) ◽  
pp. 1438-1438 ◽  
Author(s):  
K. Chittem ◽  
S. M. Mansouripour ◽  
L. E. del Río Mendoza
Keyword(s):  
United States ◽  
North Dakota ◽  
Plasmodiophora Brassicae ◽  
The United States ◽  
Soil Samples ◽  
Pcr Analysis ◽  
Infested Soil ◽  
First Report ◽  
Resting Spores ◽  
Pathogenicity Tests

North Dakota leads the United States in canola (Brassica napus L.) production (4). A canola field with a distinct patch of dead plants spreading over an area of approximately 0.4 ha was detected in Cavalier County, North Dakota, in early September 2013. Numerous spots within the patch had plant mortalities >80%. Dead plants pulled from the soil had roots with severe galling and clubbing. Clubbed roots were brittle and disintegrated easily when pressed between fingers. Root and soil samples collected at several locations within and outside the affected patch were pooled in separate groups. All plants collected in the patch were symptomatic but those collected outside were not. In the lab, total genomic DNA from three symptomatic and two healthy root samples was extracted using standard procedures and freehand slices were prepared for observation with a compound microscope. Also, DNA from pooled soil samples was extracted using FastDNA Spin Kit for Soil (MP Biomedicals, Solon, OH). Round resting structures ranging from 2.2 to 4.2 μm in diameter were observed by microscopic examination of symptomatic root tissues. These structures resembled those typically produced by Plasmodiophora brassicae Woronin. This initial identification was later confirmed through PCR analysis using the species specific primers TC1F/R and TC2F/R (1). PCR products of 548 bp (TC1F/R) and 519 bp (TC2F/R) were produced in the three symptomatic and two infested soil samples, confirming the presence of P. brassicae. PCR amplicons were not detected in healthy root and soil samples. Pathogenicity tests were conducted in greenhouse to fulfill Koch's postulates. Briefly, five square plastic pots (10 × 10 × 13 cm) were filled with a 10-cm layer of Sunshine Mix #1 potting mix (Fison Horticulture, Vancouver, BC, Canada) and then 1 g of ground root galls (approximately 5 × 105 resting spores) was spread evenly on its surface and covered with 2 cm of soilless mix. A similar number of pots were filled only with soilless mix and used as controls. All pots were planted with two seeds of canola cv. Westar and incubated in greenhouse conditions at 21°C and 16 h light daily. The experiment was conducted twice. Four weeks after planting, all plants in the inoculated pots had developed galls while plants in control pots were symptomless. Presence of P. brassicae resting spores in the newly developed galls was confirmed by microscopic observations and PCR. Based on the symptoms, morphology of resting spores, PCR reactions, and pathogenicity tests, we confirm the presence of P. brassicae on canola. While P. brassicae has been reported as widespread in North America (2), to our knowledge, this is the first report of clubroot on canola in North Dakota and the United States. Clubroot became the most important disease affecting canola production in central Alberta, Canada, within 5 years of its discovery in 2003 (3); since then, the disease has been detected in Saskatchewan and Manitoba (3), Canadian provinces that share borders with North Dakota. Considering the difficulties in management of clubroot, measures should be initiated to limit the spread of the disease before it could pose a threat to United States canola production. References: (1) T. Cao et al. Plant Dis. 91:80, 2007. (2) G. Dixon J. Plant Growth Regul. 28:194, 2009. (3) S. Strelkov and S. Hwang. Can. J. Plant Pathol. 36(S1):27, 2014. (4) USDA-NASS, Ag. Statistics No. 81, 2012.

scholarly journals First Report of the Root-Knot Nematode (Meloidogyne incognita) on Curcuma longa in the United States

Plant Disease ◽  
2017 ◽  
Vol 101 (10) ◽  
pp. 1826-1826
Author(s):  
M. Hall ◽  
K. Lawrence ◽  
W. Groover ◽  
D. Shannon ◽  
T. Gonzalez
Keyword(s):  
United States ◽  
Meloidogyne Incognita ◽  
Curcuma Longa ◽  
The United States ◽  
Root Knot Nematode ◽  
First Report

scholarly journals Recent Outbreak of Soybean Sudden Death Syndrome Caused by Fusarium virguliforme and F. tucumaniae in Argentina

Plant Disease ◽  
2004 ◽  
Vol 88 (9) ◽  
pp. 1044-1044 ◽  
Author(s):  
M. Scandiani ◽  
D. Ruberti ◽  
K. O'Donnell ◽  
T. Aoki ◽  
R. Pioli ◽  
...  
Keyword(s):  
United States ◽  
Phylogenetic Analyses ◽  
The United States ◽  
Positive Control ◽  
Koch’S Postulates ◽  
First Report ◽  
Molecular Phylogenetic ◽  
Soil Infestation ◽  
Pathogenicity Tests ◽  
Koch's Postulates

Sudden death syndrome (SDS) of soybean was detected initially in Argentina during 1991-1992 in the Pampas Region and 1992-1993 in the Northwest Region. The first report of the fulfillment of Koch's postulates of SDS caused by Fusarium solani f. sp. glycines in Argentina was published in 2003 (3). Subsequently, analyses have shown that F. solani f. sp. glycines represents several morphologically and phylogenetically distinct species, including F. tucumaniae in Argentina and F. virguliforme in the United States (1). Isolations were made from plants that exhibited typical SDS symptoms (interveinal foliar chlorosis and necrosis leading to defoliation of the leaflets but not the petioles) from fields in Santa Fe and Buenos Aires provinces in 2001, 2002, and 2003. To determine which species are responsible for SDS in Argentina, cultures of eight slow growing isolates that developed bluish pigmentation and produced abundant macroconidia in sporodochia on potato dextrose agar were subjected to morphological and molecular phylogenetic analyses and pathogenicity tests. Morphological analyses demonstrated that three of the isolates were F. virguliforme and five were F. tucumaniae. Isolates of F. tucumaniae produced long and narrow sporodochial conidia while F. virguliforme produced diagnostic comma-shaped conidia. Molecular phylogenetic analyses of DNA sequences from multiple loci confirmed morphology-based identifications and showed that the soybean SDS pathogen in the United States, F. virguliforme, was also present in Argentina. To our knowledge, this is the first report of F. virguliforme in Argentina and of this pathogen outside the United States. Five isolates of F. tucumaniae and three isolates of F. virguliforme were used for pathogenicity tests. F. virguliforme isolate 171 provided by J. Rupe (University of Arkansas, Fayetteville) was used as a positive control. Soybean cultivars Ripley, RA 702, Pioneer 9492RR, Spencer, and A-6445RG were inoculated with each of the isolates tested in a greenhouse assay using soil infestation and toothpick methods (2). All eight isolates produced typical foliar SDS symptoms 15 to 25 days after inoculation. Severity of foliar symptoms averaged 3.3 for F. virguliforme, 2.6 for F. tucumaniae, and 3.3 for the positive control using a disease severity scale in which 1 = no symptoms and 5 = severely infected or dead plants. Under these conditions, F. virguliforme appeared to be more virulent than F tucumaniae. Noninoculated plants remained symptomless. Koch's postulates were confirmed with soybean cultivars RA 702 and A6445RG. Isolates recovered from symptomatic plants inoculated by the soil infestation and toothpick methods were identical to those used to inoculate the plant. Strains were recovered at frequencies of 100 and 60% from plants inoculated by the toothpick and soil infestation methods, respectively. To our knowledge, this is the first report of the fulfillment of Koch's postulates for F. tucumaniae and F. virguliforme in Argentina. References: (1) T. Aoki et al. Mycologia 95:660, 2003. (2) K. W. Roy et al. Plant Dis. 81:1100, 1997 (3) M. Scandiani et al. Plant Dis. 87:447, 2003.

Identification of Sweetpotato Germplasm Resistant to Pathotypically Distinct Isolates of Meloidogyne enterolobii from the Carolinas

Plant Disease ◽  
2021 ◽  
Author(s):  
William Rutter ◽  
Phil Wadl ◽  
John David Mueller ◽  
Paula Agudelo
Keyword(s):  
United States ◽  
Ipomoea Batatas ◽  
Germplasm Collection ◽  
Resistance Breeding ◽  
The United States ◽  
Root Knot Nematode ◽  
Breeding Programs ◽  
Nematode Reproduction ◽  
Pathogenic Variants ◽  
Meloidogyne Enterolobii

Meloidogyne enterolobii (syn. mayaguensis) is an emergent species of root-knot nematode that has become a serious threat to sweetpotato (Ipomoea batatas) production in the southeastern United States. The most popular sweetpotato cultivars grown in this region are highly susceptible to M. enterolobii. As a result, this pest has spread across most of the sweetpotato growing counties in the Carolinas, threatening the industry as well as other crops in the region. The development and release of new sweetpotato cultivars with resistance to M. enterolobii would help to manage and slow the spread of this pest. To support sweetpotato resistance breeding efforts, 93 accessions selected from the USDA germplasm collection and breeding programs in the United States were screened to identify 19 lines with strong resistance to M. enterolobii. The resistance in these accessions was tested against two M. enterolobii isolates that were collected from sweetpotato production fields in the Carolinas. These isolates were found to have distinct pathotypes, with galling and nematode reproduction differences observed on cotton as well as sweetpotato. This study is the first report of intraspecific pathotypic variation in M. enterolobii and identifies sweetpotato germplasm with resistance against both pathogenic variants of this nematode.

scholarly journals First Report of Downy Mildew Caused by Peronospora lamii on Salvia splendens and Salvia coccinea

Plant Disease ◽  
2000 ◽  
Vol 84 (10) ◽  
pp. 1154-1154 ◽  
Author(s):  
G. E. Holcomb
Keyword(s):  
United States ◽  
Downy Mildew ◽  
Pathogenic Fungi ◽  
The United States ◽  
Commonwealth Mycological Institute ◽  
First Report ◽  
Leaf Spots ◽  
Salvia Splendens ◽  
Leaf Surfaces ◽  
Pathogenicity Tests

Angular chlorotic spots were observed on adaxial leaf surfaces of Salvia splendens (scarlet sage cvs. Empire Purple, Empire White, Red Pillar, and Red Hot Sally) and S. coccinea (scarlet or Texas sage cv. Lady in Red) in early May in Baton Rouge area nurseries. Leaf spots sometimes became necrotic and resulted in leaf drop. Abaxial leaf surfaces contained scattered patches of white mycelia with brown spores. Microscopic examination of mycelia revealed irregular dichotomously branched conidiophores with pointed tips and brown oval conidia. Conidiophores averaged 485 × 9 µm and conidia averaged 21 × 18 µm (16 to 26 × 15 to 23 µm) in dimensions. The fungus was identified as Peronospora lamii A. Braun (= P. swinglei Ellis & Everh.) based on these characters and its known occurrence on Salvia spp. and five other genera in the family Lamiaceae (2). Pathogenicity tests were performed by washing conidia from infected leaves into distilled water and mistinoculating S. coccinea cv. Lady in Red and S. splendens cv. Empire Purple with 50,000 spores/ml. Plants were held in a dew chamber at 20°C for 3 days, then moved to a greenhouse where temperatures ranged from 18 to 32°C. Typical angular chlorotic leaf spots developed on inoculated plants within 6 to 8 days and noninoculated plants remained healthy. The fungus did not sporulate under these greenhouse temperatures, but infected leaves that were removed and placed in a moist chamber at 25°C produced conidiophores and brown conidia typical of P. lamii within 2 to 3 days. P. lamii has been reported previously on S. officinalis (3) and S. reflexa (1) in the United States. This is the first report of downy mildew on S. coccinea and S. splendens. Appearance of the disease in retail nurseries that obtained plants from out of state (Arkansas) suggests a widespread occurrence of the disease on these host plants. References: (1) D. F. Farr et al. 1989. Fungi on Plants and Plant Products in the United States. American Phytopathological Society, St. Paul, MN. (2) S. M. Francis. 1981. Peronospora lamii. Descriptions of Pathogenic Fungi and Bacteria No. 688. Commonwealth Mycological Institute, Kew, England. (3) R. T. McMillan and W. R. Graves. Plant Dis. 78:317, 1994.

scholarly journals First Report of Collar and Stem Rot Caused by Pythium aphanidermatum on Figmarigold (Lampranthus sp.) in Italy

Plant Disease ◽  
2009 ◽  
Vol 93 (6) ◽  
pp. 672-672 ◽  
Author(s):  
A. Garibaldi ◽  
D. Bertetti ◽  
P. Pensa ◽  
M. L. Gullino
Keyword(s):  
United States ◽  
Its Region ◽  
The United States ◽  
Pythium Aphanidermatum ◽  
Peat Moss ◽  
Fluorescent Light ◽  
Rooted Cuttings ◽  
First Report ◽  
Light Yellow ◽  
Pathogenicity Tests

Lampranthus sp. N.B. Brown (figmarigold) of the Aizoaceae family is used as groundcover in gardens. In October of 2008, severe outbreaks of a previously unknown rot were observed in a nursery located in Liguria, near Savona (northern Italy), on 35-day-old rooted cuttings grown in a peat substrate. Approximately 50% of rooted cuttings of red-flowered cultivars were affected. Lesions on collars and young stems were brown, water soaked, and soft. Plants eventually collapsed as roots rotted. Thin, aerial hyphae were visible on the surface of the stems and substrate. Later, a thick, light yellow, mycelial mat surrounded infected plants. Tissue fragments were excised from the margins of the lesions, dipped in a solution containing 1% sodium hypochlorite, and plated on potato dextrose agar and a medium selective for Oomycetes (4). Plates were incubated under constant fluorescent light at 23 ± 1°C for 4 to 5 days. Hyphae of five isolates grown on V8 medium were aseptate and 4.2 to 7.9 (average 6.2) μm wide. Sporangia consisted of complexes of swollen hyphal branches. Oogonia were globose, smooth, and 23.5 to 28.0 (average 25.9) μm in diameter. Antheridia were barrel shaped, intercalary, and diclinous. Oospores were globose and 19.4 to 23.6 (average 21.4) μm in diameter. The internal transcribed spacer (ITS) region of rDNA of a single isolate (DB24112008) was amplified with primers ITS4/ITS6 and sequenced. A BLAST analysis (1) in GenBank of the 1,074-bp segment showed a 100% homology with the sequence of Pythium aphanidermatum (Accession No. EU245039). The nucleotide sequence has been assigned the GenBank Accession No. FJ492745. Pathogenicity tests were performed twice on a red-flower cultivar of a Lampranthus sp. grown in 1-liter pots containing a peat moss substrate infested with wheat and hemp kernels colonized with one isolate of P. aphanidermatum at a rate of 20 g/liter. Ten plants were grown in infested media and 10 plants were grown in noninfested media. Greenhouse temperatures were 18 to 24°C. The first symptoms of stem and root rot developed 15 days later, while control plants remained healthy. P. aphanidermatum was consistently reisolated from the lesions. To our knowledge, this is the first report of P. aphanidermatum on a Lampranthus sp. in Italy. The disease has been reported in Japan (3) in 2008, while in the United States, a Pythium sp. was reported on L. aureus and L. glomeratus (2). Currently, the economic importance of Pythium rot on figmarigold in Italy is still limited. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) D. F. Farr et al. Fungi on Plants and Products in the United States. The American Phytopathological Society, St Paul, MN, 1989. (3) H. Kawarazachi et al. J. Gen. Plant Pathol. 74:94, 2008. (4) H. Masago et al. Phytopathology, 67, 425, 1977.

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