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Division of Plant Pathology and Microbiology, Department of Plant Sciences, The University of Arizona, Tucson, Arizona 85721
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSTAXONOMYRESULTSDISCUSSIONLITERATURE CITED |
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A species of Labyrinthula that causes ‘rapid blight’ and death of turfgrass has been isolated and studied. We name this new species Labyrinthula terrestris and briefly summarize morphological characteristics and growth patterns of this pathogen of turfgrass.
Key words: Chromista, Labyrinthulaceae, Labyrinthulales, Labyrinthulomycetes, rapid blight
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSTAXONOMYRESULTSDISCUSSIONLITERATURE CITED |
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). This unique group has been classified in many ways over the past century (Barr 1992). In the last two decades protistologists have placed the genus in the Kingdom Protista (Levine et al 1980, Corliss 1984). Based on 18s rRNA region data, Cavalier-Smith et al (1994) reorganized the kingdom, placing Labyrinthula in the phylum Heterokonta, subphylum Labyrinthista, with the Thraustochytrids. After comparing their 18S ribosomal gene sequence data, Honda et al (1999) concluded that "currently used taxonomic criteria might need serious reconsideration". The classification of Labyrinthula probably will continue to be revisited as new morphological and molecular data are gathered.
Characteristics of the genus Labyrinthula were first described and named by Cienkowski (1867). He first isolated Labyrinthula from marine algae and referred to it as a marine slime or net-slime mold. It produces motile cells that move on a net-like extracellular matrix secreted by a specialized organelle, the sagenogenetosome (Perkins 1972). The terms sagenogen (Olive 1975) or alternatively, bothrosome (Porter 1969), also have been used for this organelle. The ectoplasmic net produced by these organelles enables the cell to move singly or glide through networks previously produced by other cells (Porter 1969, 1972; Moss 1985). Labyrinthula cells can move up to 150 µm min–1 on an agar plate medium (Young 1943) and up to 175 µm min–1 in a liquid medium (Muehlstein et al 1991).
Ten species of Labyrinthula have been described (Muehlstein et al 1991, Porter 1990). The only proven pathogenic species of Labyrinthula, L. zosterae D. Porter & Muehlst., described by Muehlstein et al (1988, 1991), was implicated earlier in wasting disease of eelgrass, Zostera marina L., by Renn (1934, 1935), Young (1937, 1943) and Short et al (1986) in North America and by Armiger (1964) in eelgrass near New Zealand.
All previously described Labyrinthula species have been found in marine or hypersaline conditions except for Labyrinthula cienkowski Zopf, isolated from Vaucheria sessilis, a freshwater alga (Zopf 1892). Aschner (1958) cultured Labyrinthula macrocystis Cienk. from soil around roots of a diseased Carica papaya in Israel. According to Aschner (1961) the soil substrate from which L. macrocystis was isolated was saline (irrigation water in the Jordan River Valley was 250 ppm chloride). Amon (1978b) isolated a species of Labyrinthula from material collected at a frozen beachside near Antelope Island, Great Salt Lake, Utah where the water salinity was 1000 ppm. Labyrinthula was isolated by pollen baiting, using sterilized artificial seawater or by direct plating of plant materials, sand, water, or feather fragments on Vishniac’s medium (Fuller et al 1964).
An organism similar to that described was first diagnosed in dying turfgrass in 1995 in California and had been described in nine other states by 2002 (Martin et al 2002). The symptomatic state of the turfgrass was termed "rapid blight", but the cells observed in leaf blade tissues associated with the disease were not identified. This apparent wide distribution is similar to the situation reported by Vergeer and den Hartog (1994) concerning Labyrinthula species associated with specific seagrasses.
In Nov 2002, symptoms of rapid blight were observed in turfgrass from a golf course near Litchfield, Arizona. Cells similar to those described by Martin et al (2002) were observed in symptomatic tissue, identified as Labyrinthula, and Koch’s postulates were fulfilled by inoculating grasses and recovering the organism from symptomatic tissue (Olsen et al 2003). Subsequently, Labyrinthula has been observed in turfgrass from six golf courses in Arizona.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSTAXONOMYRESULTSDISCUSSIONLITERATURE CITED |
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). The medium was prepared using irrigation water (EC = 4.0 dS/m at 25 C) from a golf course with a history of disease and subsequently labeled SIA+. Cultures were incubated at room temperature. Maintenance cultures were grown on SIA+ or KMV (Amon 1978a) (using irrigation water) on Petri plates or slants, transferred to sterile irrigation water amended with 1% horse serum broth and refrigerated (Porter 1987). Light microscopy.— – Labyrinthula cultures were isolated from Poa trivialis or Lolium perenne on SIA+. Individual cells were measured on the second to third d of growth from the advancing margins of the colonies. Cells were mounted on glass slides in sterile irrigation water and viewed on an Olympus BX60 system microscope using phase contrast resolution. Fifty cells were measured using the Olympus ocular previously checked for accuracy with a Leitz-Wetzlar micrometer.
Electron microscopy.— –
Labyrinthula isolated on SIA+ from inoculated ryegrass L. perenne after 3 d was fixed in 4% formaldehyde, 1% glutaraldehyde in 0.1 M cacodylate buffer (pH 7.4) plus 0.01% CaCl (modified from Trump 1978), 0.075% ruthenium red (Hayat 1993), microwaved 2 min at 150 watts, then cooled 2 min, repeated, and allowed to sit 1 h at room temperature. Samples were rinsed three times in 0.1 M cacodylate buffer (pH 7.4) plus 0.01% CaCl, 0.075% ruthenium red postfixed in 1.0% osmium tetroxide in deionized water with 0.075% ruthenium red for one h and rinsed in deionized water. The cells then were dehydrated through a standard ethanol series (Hayat 2000) and infiltrated in Epon, heated 15 min in the microwave at 35 C, then incubated 4–8 h room temperature. Samples were cut at 100 µm, stained with saturated aqueous uranyl acetate and Reynolds lead citrate (Reynolds 1963), and observed at 80 Kv on a Jeol 100 CX II transmission electron microscope.
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TAXONOMY |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSTAXONOMYRESULTSDISCUSSIONLITERATURE CITED |
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Specimens examined. – 0001, 0002, 0005, 0006, 0007, 0008, 0009. USA, Arizona, golf course, Litchfield, Poa trivialis L., Lolium perenne L., M.W. Olsen, 0001, ARIZ, 20 Feb 2003. USA, Arizona, golf course, Litchfield, nursery plot # 56, Poa trivialis L., M.W. Olsen, 0008, 12 Jan 2004. USA, Arizona, golf course, Maricopa, Poa trivialis L., M.W. Olsen, 0002, ARIZ, 26 May 2003 USA, Arizona, golf course, Phoenix, Poa trivialis L., P. Burgess, 0005, ARIZ, 12 Nov 2003. USA, Arizona, golf course, Phoenix, Poa trivialis L., D. Glinski, 0006, ARIZ, 11 Dec 2003 USA, Arizona, golf course, Glendale, Poa trivialis L., T. Allen, 0007, ARIZ, 8 Jan 2004. USA, Arizona, golf course, Phoenix, Poa trivialis L., M. W. Olsen, 0009, ARIZ, 17 Jan 2004.
Vegetativae cellulae fusiformes, (13.4–)15.3(–17.1) x (4.5–)5.5(–6.6) µm, divisio transversalis et longitudinalis, hyalinae vel atrolutens in massa in cultura agari; vacuolae in frequenter adsunt cellulae; numerosus lipidae guttulae adsunt; ectoplasmicum reticulum ramificans et anastomosans; caespes aggregatus ex cellulis fusiformis ex cellulis fusiformis usque ad 0.1–0.5 mm diam, nullus sorus factus; nullae reproductivae cellulae adsunt evidentes; segregata solum ex necroticis areas in foliis Poa trivialis et Lolium perenne ubi aqua irriguus 1.5– 4.0 dS/m. Descriptio ex observatione cellularum in culturis puris in agaro, in liquido et cellulae consociatae cum infectus foliis graminis.
Holotype; M. W. Olsen 0001, 20 Feb 2003, from L. perenne, golf course, Litchfield, Maricopa County, Arizona, 20 Feb 2003 (ATCC MYA-3074).
Vegetative cells fusiform, (13.4–)15.3(–17.1) x (4.5–)5.5(–6.6) µm, division transverse and longitudinal, sometimes oblique, hyaline to dark yellow in mass in agar culture, containing vacuoles and numerous lipid droplets; ectoplasmic network branching and anastomosing; clumped aggregates of cells 0.1–0.5 mm diam; no sorus formed; no reproductive cells evident; isolated from necrotic areas of Poa trivialis and Lolium perenne where irrigation water had been 1.5–4.0 dS/m. Description from cells seen in agar culture, liquid culture and cells seen within infected grass leaf blades.
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSTAXONOMYRESULTSDISCUSSIONLITERATURE CITED |
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). Fusiform-shaped vegetative cells can be seen in the grass leaf-blade epidermis of the plant (FIG. 2), and grow from infected leaf tissue on agar medium to form irregularly shaped digitate colonies (FIG. 3). In each case vegetative cells from symptomatic grass grow out from leaf pieces within 1–2 d on SIA+. Trophic cells flow out from host tissue, are motile and move through slime networks (FIG. 3). On SIA+ medium, colonies from inoculated grass grow out and expand to 4 mm in 24 h. Within 1–2 wk, cells clump in an aggregation on SIA+ or KMV plates. Aggregates are hyaline to yellow, are generally rounded and are 0.1–0.5 mm diam (FIG. 4). No sorus or sporulating structures have been observed under any conditions. Chemically fixed cells viewed by transmission electron microscopy contain varying amounts of dense granular bodies, vacuoles and lipid droplets. Also, note mitochondrial tubular cristae, characteristic of the kingdom Chromista (Taylor 1999) (FIG. 5). Labyrinthula terrestris cells are seen in infected rye-grass using transmission electron microscopy (FIGS. 5, 6).
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSTAXONOMYRESULTSDISCUSSIONLITERATURE CITED |
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. Muehlstein et al (1991) used these characters to delineate L. zosterae.
The following characters differ in L. terrestris compared to those of L. zosterae: Cells of the two species differ in size and shape. L. terrestris cells in agar culture are 13.4–17.1 µm x 4.5–6.6 µm and ellipsoid-fusiform. Cells of L. zosterae are 15.5–19.5 x 3.5–5.0 and linear-fusiform. In culture, cells of L. terrestris are hyaline to dark yellow in mass. Cells of L. zosterae are hyaline to pale yellow in mass. The known habitat for L. terrestris is terrestrial in turf-grass where irrigation water ranges from 1.5– 4.0 dS/m. The habitat for L. zosterae is marine in eelgrass, at salinity levels up to 36
. These two species differ from other Labyrinthula species in being the only species proven to have isolates that are pathogenic on plants.
Since Martin et al (2002) published their abstract, the total number of states where Labyrinthula has been seen in symptomatic turfgrass has risen to 11 (website by L. J. Stowell and W. Gelernter PACE Insights Vol. 9 No. 3 www.pace-tri.com) with occurrences at over 100 golf courses. It is probable that Labyrinthula is well established as a terrestrial inhabitant but has been overlooked, probably because of the distinctive medium necessary to isolate the organism. Its emergence as a pathogen of turfgrass may coincide with the increased acreage of turf and changes in cultural practices such as increased use of high salinity water or reclaimed water for irrigation and increased frequency of mowing combined with decreased mowing heights. Diseased turf invariably is associated with poor quality irrigation water, particularly with a salinity greater than 1.5 dS/m. As an important emerging plant pathogen in turfgrass, L. terrestris is a potential problem in turfgrass wherever high saline irrigation water or effluent is used for irrigation.
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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1 Corresponding author. E-mail: dbigelow{at}ag.arizona.edu
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LITERATURE CITED |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSTAXONOMYRESULTSDISCUSSIONLITERATURE CITED |
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———. 1978b. Thraustochytrids and Labyrinthulids of terrestrial, aquatic and hypersaline environments of the Great Salt Lake, USA. Mycologia 70:1299–1301.[CrossRef]
Armiger LC. 1964. An occurrence of Labyrinthula in New Zealand Zostera. NZ J Bot 2:3–9.
Aschner M. 1958. Isolation of Labyrinthula macrocystis from soil. Bull Res Counc Israel 6D:174–179.
———. 1961. A note on the genus Labyrinthula in Israel. Bull Res Counc Israel 10D:126–129.
Barr DJS. 1992. Evolution and kingdoms of organisms from the perspective of a mycologist. Mycologia 84:1–11.[CrossRef]
Cavalier-Smith T, Allsopp MTEP, Chao EE. 1994. Thraustochytrids are chromists, not Fungi: 18s rRNA signatures of Heterokonta. Phil Trans Roy Soc Lond B 346:387–397.[CrossRef]
Cienkowski L. 1867. Ueber den Bau und die Entwicklung der Labyrinthuleen. Arch Mikr Anat 3:274–310.
Corliss JO. 1984. The kingdom Protista and its 45 phyla. Biosystems 17:87–126.[CrossRef][Medline]
Fuller MS, Fowles BE, McLaughlin DJ. 1964. Isolation and pure culture study of marine phycomycetes. Mycologia 56:745–756.[CrossRef]
Hayat MA. 2000. Principles and Techniques of Electron Microscopy; Biological Applications. New York: Cambridge University Press. 543 p.
———. 1993. Stains and Cytochemical Methods. New York, New York: Plenum Press. 455 p.
Honda D, Yokochi T, Nakahara T, Raghukumar S, Nakagiri A, Schaumann K, Higashihara T. 1999. Molecular phylogeny of Labyrinthulids and Thraustochytrids based on the sequencing of 18S ribosomal RNA gene. J Eukaryot Microbiol 46:637–647.[Medline]
Kirk PM, Cannon PF, David JC, Stalpers JA. 2001. Ainsworth and Bisby’s Dictionary of the Fungi. 9th ed. Oxford, England: CAB International. 655 p.
Levine ND, Corliss JO, Cox FEG, Deroux G, Grain J, Honigberg BM, Leedale GF, Loeblich AR, Lom J, Lynn D, Merinfeld EG, Page FC, Poljansky G, Sprague J, Vavra J, Wallace FG. 1980. A newly revised classification of the protozoa. J Protozool 27:37–58.[Medline]
Martin SB, Stowell LJ, Gelernter WD, Alderman SC. 2002. Rapid blight: a new disease of cool season turfgrasses. Phytopathology 92:S52.
Moss ST. 1985. An ultrastructural study of taxonomically significant characters of the Thraustochytriales and the Labyrinthulales. J Linn Soc Lond Bot 91:329–357.
Muehlstein LK, Porter D, Short FT. 1988. Labyrinthula sp., a marine slime mold producing the symptoms of wasting disease in eelgrass, Zostera marina. Marine Bio 99: 465–472.[CrossRef]
Muehlstein LK, Porter D. 1991. Labyrinthula zosterae sp. nov., the causative agent of wasting disease of eelgrass, Zostera marina. Mycologia 83(2):180–191.[CrossRef]
Olive LS. 1975. The Mycetozoans. New York: Academic Press. 293 p.
Olsen MW, Bigelow DM, Gilbertson RL, Stowell LJ, Gelernter WD. 2003. First report of a Labyrinthula sp. causing rapid blight disease of rough bluegrass and perennial ryegrass. Plant Dis 87:1267.
Perkins FO. 1972. The ultrastructure of holdfasts, "rhizoids" and "slime tracks" in thraustochytriaceous fungi and Labyrinthula spp. Arch Mikrob 84:95–118.[CrossRef]
Porter D. 1969. Ultrastructure of Labyrinthula. Protoplasma 67:1–19.
———. 1972. Cell division in the marine slime mold, Labyrinthula sp., and the role of the bothrosome in extracellular membrane production. Protoplasma 74: 427–448.[CrossRef]
———. 1987. Labyrinthulomycetes. In: Fuller MS, Jaworski A, eds. Zoosporic fungi in teaching and research. Athens, Georgia: Southeastern Publishing Corporation. p 110–113.
———. 1990. Labyrinthulomycota. In: Margulis L, Corliss J, Melkonian M, Chapman D, eds. Handbook of Protoctista. Boston, Massachusetts: Jones and Bartlett Publishers. p 388–398.
Renn CE. 1934. Wasting disease of Zostera in American waters. Nature 134:416.
———. 1935. A mycetozoan parasite of Zostera marina. Nature 135:544–545.
Reynolds ES. 1963. The use of lead citrate at high pH as an electron-opaque stain in electron microscopy. J Cell Biol 17:208.
Short FT, Mathieson AC, Nelson JI. 1986. Recurrence of the eelgrass wasting disease at the border of New Hampshire and Maine, USA. Mar Ecol Prog Ser 29: 89–92.[CrossRef]
Taylor FJR. 1999. Ultrastructure as a control for protistan molecular phylogeny. Amer Nat 154:125–136.[CrossRef]
Trump BF, Jones RT. 1978. Diagnostic Electron Microscopy. Vol 1. New York, New York: John Wiley & Sons Inc. 346 p.
Vergeer LHT, den Hartog C. 1994. Omnipresence of Labyrinthulaceae in seagrasses. Aquat Bot 48:1–20.[CrossRef]
Young EL. 1937. Notes on the Labyrinthula parasite of eelgrass Zostera marina. Bull Mt Desert Isl Biol Lab. p 33–35.
———. 1943. Studies on Labyrinthula; the etiologic agent of the wasting disease of eel-grass. Am J Bot 30:586–593.[CrossRef]
Zopf W. 1892. Zur Kenntniss der Labyrinthuleen, einer Familie der Mycetozoen. Beit Physiol Morph Nied Organ 2:36–48.
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