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Department of Botany, Kumaun University, Nainital-263002 India
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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Eighteen species of aquatic hyphomycetes were recorded as root endophytes in roots of living plants including grasses and pteridophytes from wet fields near ravine areas. Alatospora acuminata, A. pulchella, Acaulopage tetraceros, Anguillospora crassa, Campylospora chaetocladia, Lemonniera cornuta, L. pseudofloscula, L. terrestris, Pestalotiopsis submersus and Tetrachaetum elegans were found for the first time as root endophytes. A. longissima, Campylospora purvula, Clavariopsis aquatica, Cylindrocarpon aquaticum, Heliscus lugdunensis, Lunulospora curvula, Tetracladium marchalianum and T. setigerum, which were known previously as root endophytes, are reported here on new hosts. Maximum occurrence was found in November and December.
Key words: aquatic hyphomycetes, mycorrhizae, root endophytes
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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, 1990; Petrini 1986; Petrini et al 1992a, b; Bernstein and Carroll 1977; Carroll and Carroll 1978; Fisher and Petrini 1992; Wilson and Carroll 1984). Endophytes occupy unique ecological niches and can influence the distribution, ecology, physiology and biochemistry of plants (Sridhar and Raviraja 1995). In addition, endophytic hyphomycetes may provide products useful in biotechnology and agriculture (Bills and Polishok 1992, Petrini 1991, Dreyfuss and Chapela 1992).
Ingold (1942) described aquatic hyphomycetes as colonizers of submerged substrates in well aerated waters. Waid (1954) first reported aquatic hyphomycetes from root surfaces. Numerous reports since have been made of aquatic hyphomycete endophytes from aquatic and terrestrial roots, and evidence exists that species can be specialized for this role (Fisher et al 1986, Fisher et al 1991, Gourley 1969, Marvanova and Fisher 1991, Marvanova et al 1992, Nemec 1969, Park 1974, Parkinson and Thomas 1969, Sridhar and Barlocher 1992, Watanabe 1975).
Our study was carried out to investigate endophytic aquatic hyphomycetes occurring in association with roots of plant species near two freshwater streams of Kumaun Himalaya, India.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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) growing in the riparian area of Jageshwar (1775 m elevation) and Jeoli (1150 m elevation) located respectively at 102 km and 20 km from Nainital, Kumaun Himalaya (India), were collected at monthly intervals for 2 yr. Samples in five replicates each were taken from living and healthy plant species at both sites. Roots ca. 25 cm long were removed with a sharp sterile knife and washed with sterile water. These root samples were kept in sterile polyethylene bags, taken to the laboratory and processed. Two culture methods were employed to identify endophytic fungi.
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Agar plating.— –
As described by Fisher et al (1991) and Sridhar and Barlocher (1992), root samples were immersed in 0.01% sodium hypochlorite 3–6 min and again in 96% ethanol for up to 30 s for surface sterilization. Root samples were cut into small segments of 1–2 cm and rinsed with sterile water. These segments were placed in Petri dishes containing 2% malt-extract agar (MEA) supplemented with either streptomycin and penicillin or tetramycine (250 mg/L) and incubated 5–20 d at 20±2 C. Agar blocks with mycelium were transferred to sterile water in Petri dishes for sporulation and identification. Occurrence of endophytic fungi in different root samples was recorded as % frequency, calculated by noting the presence of species in 24 monthly samples.
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RESULTS AND DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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). Ten species (viz. Alatospora acuminata, A. pulchella, Acaulopage tetraceros, Anguillospora crassa, Campylospora chaetocladia, Lemonniera cornuta, L. pseudofloscula, L. terrestris, Pestalotiopsis submersus and Tetrachaetum elegans) are reported here for the first time as endophytic aquatic hyphomycetes. The remaining eight species, reported previously as endophytes, were recorded here on new hosts (TABLE I). Anguillospora longissima, Tetracladium marchalianum and T. setigerum, reported earlier from strawberry roots (Nemec 1969, Watanabe 1975), were recorded obtained from Lyonia ovalifolia and other diverse plants including pteridophytes. Campylospora purvula, Heliscus lugdunensis, Lunulospora curvula, Clavariopsis aquatica and Cylindrocarpon aquaticum have been reported as root endophytes in association with Alnus species or conifers (Fisher and Petrini 1989, 1990; Fisher et al 1991; Sridhar and Barlocher 1992a, b). In our study, these species were found in association with other plant species (TABLE I). Cylindrocarpon aquaticum was the most common species and was isolated in each sample collected over 2 yr (Table I).
We have summarized monthly occurrence and frequency values for the endophytic hyphomycetes from Jageshwar and Jeoli streams (TABLES II and III). The maximum occurrence was in November and December, when temperatures were low relative to other months. At the Jageshwar site, which is the higher of the two sites (1775 m), Cylindrocarpon aquaticum showed maximum frequency of occurrence (100%), followed by Tetracladium marchalianum and T. setigerum (75% and 62.5% respectively). Anguillospora crassa and Clavariopsis aquatica had 16.7% frequency of occurrence followed by Acaulopage tetraceros, Alatospora pulchella, Campylospora chaetocladia and Lunulospora curvula, which had 12.5% frequency of occurrence and 2.1% relative frequency (TABLE II).
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). The two most frequent species were Tetracladium marchalianum and Anguillospora longissima (87.5% and 62.5% respectively). The minimum frequency of occurrence was recorded for Anguillospora crassa, Campylospora purvula, Lemonniera cornuta L. pseudofloscula, Pestalotiopsis submersus and Tetrachaetum elegans (12.5–8.3%).
Of 18 species recorded in this study, 12 species (viz. Alatospora acuminata, Anguillospora crassa, A. longissima, Campylospora purvula, Heliscus lugdunensis, Lemonniera cornuta, L. pseudofloscula, Lunulospora curvula, Pestalotiopsis submerses, Tetrachaetum elegans, Tetracladium marchalianum and T. setigerum) were common at both sites. This diversity might be due to the altitude of the study area. A positive correlation between diversity of aquatic hyphomycetes and altitude has been reported by Raviraja et al (1998).
In our study it was interesting to note that at the later stages of incubation, when the roots became highly colonized by bacteria, certain fungi (viz. Alatospora acuminata, Campylospora purvula, Tetracladium marchalianum and T. setigerum) were observed more frequently. This suggests that endophytic hyphomycetes that are tolerant of such contamination could help to reduce infection by plant pathogenic bacteria through competition, as has been suggested (Bills and Polishok 1992; Petrini et al 1992; Fisher et al 1984a, b).
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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1 Corresponding author.
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LITERATURE CITED |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONLITERATURE CITED |
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———. 1990. Fungal endophytes of grasses. Ann Rev Ecol Syst 21:275–297.[CrossRef]
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