Vesicular-arbuscular mycorrhizal fungal sporocarps associated with Pennisetum pedicillatum

Size: px

Start display at page:

Download "Vesicular-arbuscular mycorrhizal fungal sporocarps associated with Pennisetum pedicillatum"

Raymond Stevenson
5 years ago
Views:

Proc. lndian Acad. Sci. (Plant Sci.), Vol. 96, No. 2, June 1986, pp. 153--158. 9 Printed in India.

1 Proc. lndian Acad. Sci. (Plant Sci.), Vol. 96, No. 2, June 1986, pp Printed in India. Vesicular-arbuscular mycorrhizal fungal sporocarps associated with Pennisetum pedicillatum K AMMANI, K VENKATESWARLU and A S RAO Department of Botany, Nagarjuna University, Nagarjunanagar , India MS received 26 November 1985 Abstract. Sporocarps of vesicular-arbuscular myeorrhizal fungi occurring in the rhizosphere and roots of Pennisetum pedicillatum, growing in a red late soil were studied. The characteristic features of the sporocarps of each endophyte ate described. Keywords. Pennisetum pedicillatum" sporocarps; Glomus spp.; Sclerocystis spp. 1. Introduction Members of Endogonaceae are at present receiving increased attention because of their propensity to form mycorrhizae (Hall 1983) and most ofthem have been described and identified on the basis of morphology of their sporocarp and/or spores (Gerdemann and Trappe 1974; Hall 1983). Generic separation within chlamydospo taxa is based on sporocarp morphology (Trappe and Schenck 1982). While engaged in a survey for vesicular-arbuscular mycorrhizal association in grasses, different types of sporocarps associated with the roots and rhizosphere soil samples ofpennisetum pedicillatum Trin. were noticed. This paper describes the qualitative and quantitative aspects of sporocarpic populations associated with this host. 2o Materials and methods The host plants were growing naturally on a late soil (ph 8.1) in the university campus. Root samples, collected at the flowering stage of the plant, were washed gently and stained with trypan blue (Phillips and Hayman 1970). Sporocarps from the rhizosphere soil were recovered by wet-sieving and decanting method (Gerdemann and Nicolson 1963). Large samples of soil, collected at different times, were used as some species tend to fruit only at certain times of the year. 3. Observations In all, sporocarps of two VAM genera, viz Sclerocystis and Glomus were noticed and they were identified by referring to the slide collection along with index provided by Hall and Abbott (1981). The quantitative characteristics of sporocarpic populations of different endophytes associated with the root system and the rhizosphere of the host are presented in table 1. Of the 3 species of Glomus and two species ofsclerocystis that occurred, G.fasciculatum was the most predominant endophyte while S. clavispora was less frequent. 153

154 K Ammani, K Venkateswarlu and A S Rao Tabk 1. Sporocarpic populations of VAM fungÿ in the rhizosphere and roots of P. pedicillatum. Mycorrhizal species No. of sporocarps No.

2 154 K Ammani, K Venkateswarlu and A S Rao Tabk 1. Sporocarpic populations of VAM fungÿ in the rhizosphere and roots of P. pedicillatum. Mycorrhizal species No. of sporocarps No. of sporocarps No. of sporocarps No. of spores external to the within the per I00 g in each root root rhizosphere soii sporoearp S. sinuosa S. clavispora G. fasciculatum G. fasciculatum E G. macrocarpura Glomus spp Sclerocystis sinuosa Gerdemann and Bakshi The sporocarps of this species were found associated externally with the root through extramatrical mycelium and intemally within the root. In cleared roots all the stages of development of the sporocarp were evident. In the first stage, spores were arranged around a central plexus of hyphae without a pe (figure 1). Later, cortical cells of the host were disrupted and the sporocarp occupied the cortex on one side of the stele. Finally; the sporocarp was tightly enclosed by a peridium with thickwalled sinuous hyphae. AII thestages were observed within a single root segrnent with 3 sporocarps connected by the intemal mycelium. This type of phenomenon was reported only once from Central Florida (Nicolson and Schenck 1979). Sporocarps of this fungus collected from the rhizosphere were yellowish-brown, subglobose to pulvinate with spores radiating in a single layer. Each chlamydospore was obovate to fusiform, elliptical with walls thickest near the spore base (figure 2). A peridium composed of thick-walled sinuous hyphae tightly enclosing the spores (figure 3) confirms the identity of this species as described by Gerdemann and Bakshi (1976). 3.2 Sclerocystis clavispora Trappe Sporocarps of this species were perfectly globose, rarely subglobose, brownish-black to black, very hard with more than 80 chlamydospores. ActuaUy, each sporocarp looked like a single large spore with a smooth outline and the nature and distribution of the chlamydospores was revealed only after breaking the outer hard pe The arrangement of chlamydospores inside the sporocarp was radial around a central plexus of hyphae, composed of slightly interwoven light brown coloured, thin-walled hypha (figure 4). Chlamydospores were brown coloured, very long, clavate with numerous oil globules ofdifferent sizes and with characteristic wall thickenings. Spore wall I~m thick on the side and I~m thick at the apex (figure 5). However, in the early stages, the spores showed homogenous contents with uniformly thin walls. The narrowly clavate spores and the unique pattern of spore wall thickening confirms the identity of this species in its resemblance to the type species (Trappe 1977) in almost all aspects, except for the presence of a prominent and well developed peridium. The present report ofa peridial forro of S. clavispora is probably new to the literature.

VAM fungi on P. pedicillatum 155!iiiii~ 4 Figures 1--4. 1. Sporocarp of S. sinuosa within the root cortex x 100). 2. Single chlamydospore of S.

3 VAM fungi on P. pedicillatum 155!iiiii~ 4 Figures Sporocarp of S. sinuosa within the root cortex x 100). 2. Single chlamydospore of S. sinuosa with walls thickest near the spore base ( x 640). 3. Surface view of S. sinuosa sporocarp showing sinuous peridium (x I000). 4. A part of S. clavispora showing central plexus of hyphae, radially arranged clavate spores enclosed by peridium ( t 60).

156 K Ammani, K Venkateswarlu and A S Rao : 6 / :7 i 8 Figures 5-8. 5. Single spore of S.

A typical Ioose aggregate of spores in the sporocarp of G. fasciculatum ( x I00). 7.

4 156 K Ammani, K Venkateswarlu and A S Rao : 6 / :7 i 8 Figures Single spore of S. clavispora showing wall thickenings ( x 1600). 6. A typical Ioose aggregate of spores in the sporocarp of G. fasciculatum ( x I00). 7. Sporocarp of G.fasciculatum strain E3 showing loose cluster of spores (x 160). 8. Sporocarp of G. macrocarpum showing randomly arranged spores without a peridium ( x 100).

5 VAM fungi on P. pedicillatum Glomus fasciculatum (Thaxter sensu Gerdemann) Gerdemann and Trappe Sporocarps of this cosmopolitan endophyte were found associated with the root and in rhizosphere soil, but these were not uniform in size or structure. Sporocarps isolated from the soil were in the typical form of loose aggregates with more than 280 spores (figure 6). These spores were light yellowish-brown to brown, spherical to elliptical, rarely irregular having a distinct wall of two layers, an outer hyaline and ah inner yellowish layer. Subtending hyphae are simple and single or occasionally more than one. The size, shape and morphology of r varied considerably but it did not significantly depart from that of G. fasciculatum described by Gerdemann and Trappe (1974). The identity ofthis species was confirmed in a pot culture experiment using the sporocarps as inoculum. 3.4 G. fasciculatum (Thaxter) Gerdemann and Trappe strain E3 The sporocarp consisted of a loose cluster of more than 90 spores without a peridium (figure 7). Chlamydospores were perfectly globose, gm with two layered wau and simple subtending hyphae. The endophyte is similar to that described by Hayman (1982). The ingrowths ofthe wall layers observed in few spores might have been formed due to the parasitic attack. 3.5 Glomus macrocarpum Tul. and Tul. This species was most frequently found in the rhizosphere soil. The sporocarps contained about 25 chlamydospores and were yellowish-brown without any peridium (figure 8). Chlamydospores globose to subglobose, gm with two distinct wall layers, outer being thin and hyaline and inner yellowish. Attachments were not clearly observed. Most of the features resemble those reported from Libya (EI-Ghiami et al 1976) and India (Singh and Verma 1981) except for the large number (3 times more) of chlamydospores in the sporocarp. Sporocarps of two other species of Glomus were isolated but not in sufficient numbers for confÿ the species identifÿ The observations in the present study indicate that mycorrhizal formation, involving a wide variety of endophytes, is widespread in a tropical red laterite soil. Attempts ate being made to obtain axenic cultures of the above endophytes in order to determine their efficacy on phosphorus nutrition of important agricultural crops of this area. Acknowledgement The authors are thankful to Dr I R Hall, Invermay Agricultural Research Centre, New Zealand for help in confirming the identity of some sporocarps. References El-Giahmi A A, Nicolson T H and Daft M J 1976 Endomycorrhiza! fungi from Libyan soils; Trans. Br Mycol. Soc

158 K Ammani, K Venkateswarlu and A S Rao Gerdemann J W and Nicolson T H 1963 Spores of mycorrhizal Endogone species extracted from soil by wetsieving and decanting; Trans. Br. Mycol. Soc.

6 158 K Ammani, K Venkateswarlu and A S Rao Gerdemann J W and Nicolson T H 1963 Spores of mycorrhizal Endogone species extracted from soil by wetsieving and decanting; Trans. Br. Mycol. Soc Gerdemann J W and Trappe J M 1974 The Endogonaceae in the Pacific North-West; Mycol. Mero Gerdemann J W and Bakshi B K 1976 Endogonaceae of India: Two new species; Trans. Br. Mycol. Soc Hall I R and Abbott L K 1981 Photographic slide collections illustratingfeatures of the Endogonaceae Technical Report No. 14, New Zealand Ministry of Agricutture and Fisheries, pp Hall I R 1983 Taxonomy of Vesicular-arbuscular mycorrhizal fungi; in VA Mycorrhiza (eds) C L Powell and D J Bagyaraj (Florida: CRC Press) pp Hayman D S 1982 Practical aspects of Vesicular-arbuscular mycorrhiza; in Advances in Agricultural Microbiology (ed) N S Subba Rao (Oxford: IBH Pub. Co.) pp Nicolson T H and Schenck N C 1979 Endogonaceous mycorrhizal endophytes in Florida; Mycologia Phillips J H and Hayman D S 1970 Improved procedures for clearing roots and staining parasitic and vesicular-arbuscular mycorrhizal fungi for rapid assessment of infection; Trans. Br. Mycol. Soc Singh K and Varma A K 1981 Endogonaceous spores associated with xerophytic plants in northern India; Trans. Br. Mycol. Soc Trappe J M 1977 Three new Endogonaceae: Glomus constrictus, Sclerocystis clavispora and Acaulospora scorbiculata; M'ycotaxon Trappe J M and Schenck N C 1982 Taxonomy of fungi forming endomycorrhizae; in Methods and Principles ofmycorrhizal research (ed) N C Schenck~(St. Paul: American Phytopathological Society) pp 1-6

Vesicular-arbuscular mycorrhizal associations of sesamum

Proc. lndian Acad. Sci. (Plant Sci.), Vol. 98, No. 1, February 1988, pp. 55-59. 9 Printed in India. Vesicular-arbuscular mycorrhizal associations of sesamum M VIJAYALAKSHMI and A S RAO Department of Botany,