A Preliminary Enumeration of Grass Endophytes in West Central England

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Zoologisch-Botanische Datenbank/Zoological-Botanical Database

Digitale Literatur/Digital Literature

Zeitschrift/Journal: Sydowia

Jahr/Year: 1992

Band/Volume: 44

Autor(en)/Author(s): White jr, J. F., Baldwin N. A.

Artikel/Article: A prliminary enumeration of grass endophytes in west central England. 78-84 ©Verlag Ferdinand Berger & Söhne Ges.m.b.H., Horn, Austria, download unter www.biologiezentrum.at

A preliminary enumeration of grass endophytes in west central England

J. F. White, Jr.1 & N. A. Baldwin2

•Department of Biology, Auburn University at Montgomery, Montgomery, Ala- bama 36117, U.S.A. 2The Sports Turf Research Institute, Bingley, West Yorkshire, BD16 1AU, U. K.

White, J. F., Jr. & N. A. Baldwin (1992). A preliminary enumeration of grass endophytes in west central England. - Sydowia 44: 78-84. Presence of endophytes was assessed at 10 different sites in central England. Stromata-producing endophytes were commonly encountered in populations of Agrostis capillaris, A. stolonifera, Dactylis glomerata, and Holcus lanatus. Asymp- tomatic endophytes were detected in Bromus ramosus, Festuca arundinacea, F ovina var. hispidula, F. pratensis, F. rubra, and Festulolium loliaceum. Endophytes were isolated from several grasses and identified. Keywords: Acremonium, endophyte, Epichloe typhina, grasses.

Over the past several years endophytes related to the ascomycete Epichloe typhina (Pers.) Tul. have been found to be "widespread in predominantly cool season grasses (Clay & Leuchtmann, 1989; Latch & al., 1984; White, 1987). While most of the endophytes do not produce stromata on host grasses, their colonies on agar cultures, conidiogenous cells and often conidia are similar to those of E. typhina (Leuchtmann & Clay, 1990). These cultural expressions of E. typhina and other putative Epichloe species have been classified in the anamorph genus Acremonium Link sect. Albo-lanosa Morgan- Jones & W. Gams (Morgan-Jones & Gams, 1982). Acremonium endophytes exhibit three alternative life cycle variations. In type-I associations the endophyte produces stromata on all infected tillers of a host grass, so that infected plants are frequently sterilized by the endophytes and seed transmission does not occur (Bradshaw, 1959; White, 1988). In the type-II life cycle variation, where both stroma formation and seed transmission occur, some individuals in the grass population show stroma formation and seed transmission simul- taneously on different culms (Sampson, 1933; White & Chambless, 1991). In type-III associations the endophytes do not produce stromata on plants, and are instead exclusively seed transmitted (Bacon & al., 1977; White & al., 1991). The type-I variation is infre- quently encountered in the Southern United States, instead type-II and -III associations are commonly observed (White, 1987; White &

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al., 1991). Research conducted by Bradshaw (1959) and Kirby (1961) suggested that the type-I life cycle variation is common in England. To examine distribution and ecological variation of endophytes in British grasses, studies were conducted during June and July, 1991 at the Sports Turf Research Institute in Bingley, Great Britain.

Materials and methods To assess distribution of endophytes, grasses were collected at 10 sites in west central England. Collection sites included: (A) Currer Laithe Farm, Long Lee, Keighley, West Yorkshire, (B) Coppice Lake, St. Ives Estate, Bingley, West Yorkshire, (C) Formby Golf Course, Formby, Lancashire, (D) Haworth, West Yorkshire, (E) Heswall Golf Course, Heswall, Lancashire, (F) Hoylake Golf Course, Hoylake, Lancashire, (G) Malham Cove, Malham, North Yorkshire, (H) Reakin Golf Course, Telford, Shropshire, (I) Ridge North, Cumbria, and (J) Windmere Lake, Cumbria. All grasses collected, identified, and microscopically assessed for endophytes are listed below, with each species followed by letters A - J, indicating collection sites, and number of specimens examined in parenthesis. Grasses assessed include: Agropyron junceiforme (A. & D. Love) A. & D. Love C(2); A. re-pens (L.) Beauv. A(2), C(l), D(2), E(l), F(l), G(l), H(l), 1(2); Agrostis capillaris L. A(30), B(10), C(l), D(l), E(l), F(l), J(5); A. stolonifera L. A(10), G(l); Alopecurus pratensis L. H(l); Ammophila arenaria (L.) Link F(l), C(2); Anthoxanthum odoratum L. B(l); Arrhenatherum elatius Beauv. A(3), C(l), E(l), G(l), H(l), 1(2); Avena fatua L. B(l); Avenula pubescens (Huds.) Durmort. G(l); Bromus inermis Leyss. B(l); B. hordeaceus L. A(2); B. ramosus Huds. B(2), G(2), H(2), J(l); B. sterilis L. F(l), G(l); B. tectorum L. 1(1); Cynosurus cristatus L. A(3), J(l); Dactylis glomerata L. A(8), C(l), F(l), G(l), 1(1), J(l); Deschampsia caespitosa (L.) Beauv. A(2), D(l), G(l), H(l), J(l); D. flexuosa (L.) Trin. A(2), B(l), C(l), D(l), H(l), J(l); Elymus caninus (L.) L. G(5), H(2), 1(3); Festuca arundinacea Schreb. G(3), J(l); F. ovina L. A(6), G(3), J(2); F. ovina var. hispidula (Hack.) Hack. G(7); F. pratensis Huds. A(8), J(2); F. rubra L. A(15), C(2), D(5), E(7), F(3), G(10), H(l), 1(3), J(2); Festulolium loliaceum (Huds.) P. Fourn. A(13); Glyceria fluitans (L.) R. Br. A(2); Holcus lanatus L. A(2), B(10), D(l), E(l), F(l), G(l), 1(1), J(l); H. mollis L. B(3), C(l), D(l), H(2), 1(1); Hordeum murinum L. E(l), F(l); Lolium multiflorum Lam. B(l), G(l), 1(3); L. perenne L. A(17), B(l), C(l), D(3), E(l), F(l), 1(2), J(l); Milium effusum L. H(l); Melica uniflora Retz. H(l); Nardus stricta L. A(2); Phalaris arundinacea L. B(l); Phleumpratense L. A(2), F(l), 1(1), J(l); Poa annua L. B(l), D(l), F(l); P. nemoralis L. B(l); P. trivalis L. A(4), C(2), G(l), H(l), 1(1); Puccinellia maritima (Huds.) Pari. E(l);

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Trisetum flavescens (L.) Beauv. A(2), E(l), G(l); Triticum aestivum L. B(2); Vulpia myuros (L.) C. C. Gmel. C(l), 1(1). Examination of asymptomatic grasses for endophytic fungi was made by scraping out tissues of leaf sheaths or culms, staining with aniline blue (0.1% aqueous), and examining for the presence of typical longitudinally-oriented intercellular mycelium using a com- pound light microscope (Clark & al., 1983). Infection sites exhibiting stromata were measured and reported as mean diameter and stan- dard deviation (SD). To verify that seed transmission was not occur- ring around type-I populations, 5-10 culms, each from plants without stromata, were selected at regular intervals around the perimeter of each population of stroma-bearing plants and examined as above for the presence of endophytic hyphae. To isolate endophytes, culm segments approximately 5 mm long, with or without stromata, were surface disinfected by continuous agitation in 50% Chlorox solution for 5 minutes, rinsed in sterile distilled water, and plated on potato dextrose agar (Difco). Plates were sealed with parafilm, incubated at ca. 25 C, and examined periodically for characteristic mycelium emerging from culm segments. To identify endophytes, morphological, physiological, and ecological criteria distinguishing species and varieties, outlined in White (1992) and Gams & al. (1990), were employed (Tab. 1).

Tab. 1. - Collection information and isolate identification for grasses infected with Acremonium sect. Albo-lanosa endophytes.

Host Life cycle Location of Isolate Identification of variation populations sites endophyte Agrostis capillaris Type-I A, B, J A, B A. typhinum var. bulluformum A. stolonifera Type-I A A A. typhinum var. bulluformum Bromus ramosus Type-Ill B, G, H, J G A. typhinum var. typhinum Dactylis glomerata Type-I A A A. typhinum var. fasciculatum Festuca Type-Ill G, J G Not Isolated arundinacea F. ovina var. Type-Ill G G A. typhinum var. hispidula bulluformum F. pratensis Type-Ill A, J A A. uncinatum F. rubra Type-Ill E, G, J E A. typhinum var. typhinum Festulolium Type-Ill A A A. uncinatum loliaceum Holcus lanatus Type-I B, E B A. typhinum var. fasciculatum

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Results and discussion

Grass species found to bear stromata or endophytic mycelium are listed in Tab. 1. Agrostis capillaris, A. stolonifera, Dactylis glomerata, and Holcus lanatus were occasionally infected with endophytes showing the type-I life cycle variation. Infection sites, as evidenced by clusters of stromata, were most common on A. capillaris L., where 18 different clusters, measuring on average 1.7 m (SD 1.0) in diameter, were located. Two different infection sites of A. stolonifera were found, averaging 1.5 m (SD 1.3) in diameter. Two areas of H. lanatus were found infected with choke. One area measured 4 m in diameter, the other was irregular and ranged 26 - 38 m in diameter. A single infected population of D. glomerata was located, consisting of only two stromata-bearing plants, each com- pletely choked by stromata, in proximity to several plants entirely free of infection. Examination of flowering culms surrounding stromatal clusters and occasional seed-producing plants within clusters demonstrated absence of endophytic mycelium. This suggests absence of seed transmission of these endophytes, since all infected culms bear stromata preventing seed formation. Isolation of endophytes from stromata-bearing Agrostis species reveal a fungus, identified as Acremonium typhinum Morgan-Jones & W. Gams var. bulluformum White, that is morphologically and physiologically dis- tinct from isolates obtained from D. glomerata and H. lanatus, identified as A. typhinum var. fasciculatum White (Tab. 1; White, 1992). Grasses shown to harbor endophytes exhibiting the type-III variation of life cycle include Bromus ramosus, Festuca arundinacea, F. ovina var. hispidula, F. pratensis, F. rubra, and Festulolium loliaceum. Bromus ramosus was sampled from 4 widely separated locations and found to be infected in each sampling. Isolates from this grass were identified as Acremonium typhinum var. typhinum (Tab. 1). Festuca pratensis and F. arundinacea were collected at only two sites each, however, no endophyte-free individuals were detected at either site. Festuca pratensis and Lolium perenne had hybridized at one site, and numerous progeny, Festulolium loliaceum, were evident. Seventeen specimens of L. perenne were examined from this site and all were free of infection. Of the twelve specimens of Festulolium examined, only half were infected. Isolations of endophytes from F. pratensis and Festulolium yielded Acremonium uncinatum Gams & al. (Gams & al., 1990). Whether a particular hybrid bears the fungus may depend on whether the maternal parent was endophyte-infected F. pratensis or endophyte-free L. perenne. Festuca ovina was collected from several sites and usually found to be free of endophyte. Festuca ovina var. hispidula (sensu Hubbard, 81 ©Verlag Ferdinand Berger & Söhne Ges.m.b.H., Horn, Austria, download unter www.biologiezentrum.at

1984) contained typical endophytic mycelium of A. t. var. bulluformum (Tab. 1). Similarly, red fescue, Festuca rubra, was observed to be spora- dically infected. Forty-eight specimens were examined at 9 sites, however, endophytes were detected at only 3 sites (Tab. 1) where 9 of a total of 19 plants examined contained mycelium. A previous study of endophytes in fescue and ryegrass (White & Cole, 1985) demonstrated a similarly low occurrence of endophytic mycelium in red fescue plants collected from various locations in North America. Twenty-seven collections of Lolium perenne from 8 sites were free of endophytic mycelium. This is consistent with a previous study (Lewis & Clements, 1986) where infrequent occurrence of endophytes was reported in this grass in England. In contrast, in other countries, e.g. New Zealand and the United States, this species appears to be normally infected with various endophytic fungi (Latch & al., 1984; Prestidge & al., 1982). An explanation for this inconsistency may be found in environmental differences between regions. England has a cool, moist climate. In New Zealand and the United States, frequent summer droughts and insects may give infected grasses a survival advantage over endophyte-free lines due to increased drought tolerance and insect resistance (Clay, 1988; Funk & al., 1983; West & al., 1990) and perhaps fungus disease resistance (Stovall & Clay, 1991). In this respect, it is of interest that the English Festulolium hybrids of F. pratensis and L. perenne contained endophytic mycelium, thus demonstrating a mechanism by which type-Ill endophytes may be transferred between grass species. Although that hybrid is known to be sterile (Hubbard, 1984), occasional fertile hybrids might provide a low level of infection that under sufficient environmental selection may increase. Whether such a process can account for endophytes in L. perenne or other grasses is yet to be evaluated. Environmental conditions in England may also account for the relative abundance of type-I associations there. For example, varieties of Acremonium endophytes that form abundant stromata on grasses may be selected against in drier regions where evaporative losses of water from the mycelium of stromata severely compromise either survival of infected hosts or stromata themselves (White, unpubl. data). However, in the moist climate of England, evaporation of water from stromata may have little effect on survival of host plants and stromata.

Acknowledgments

The senior author is grateful to Dr. C. R. Funk (Crop Sciences Department, Cook College, Rutgers University) and the New Jersey Agricultural Experiment Station, for a grant that made possible field studies in England. Gratitude is also expressed for

assistance provided by Dr. Peter Hayes (The Sports Turf Research Institute, Bingley, West Yorkshire, England) in making available laboratory space, facilities, and sup- plies, at the S.T.R.I, for use by the senior author. This research was funded, in part, by the National Science Foundation BSR-8922157.

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(Manuscript accepted 11th December 1991)