Curcuma bhatii (R.M. Sm.) Skornickova & M. Sabu (Zingiberaceae) and its mycorrhizal association

P.P. Rajeshkumar¹, V.B. Hosagoudar² & Mathew Dan¹

^1,2Tropical Botanic Garden and Research Institute, Palode, Thiruvananthapuram, Kerala 695562, India

Email: ²vbhosagoudar@rediffmail.com (corresponding author)

Date of publication (online): 26 June 2011

Date of publication (print): 26 June 2011

ISSN 0974-7907 (online) | 0974-7893 (print)

Editor: Richard Mibey

Manuscript details:

Ms # o2580

Received 23 September 2010

Final revised received 13 May 2011

Finally accepted 01 June 2011

Citation: Rajeshkumar, P.P., V.B. Hosagoudar & M. Dan (2011). Curcuma bhatii (R.M. Sm.) Skornickova & M. Sabu (Zingiberaceae) and its mycorrhizal association. Journal of Threatened Taxa 3(6): 1882–1884.

Copyright: © P.P. Rajeshkumar, V.B. Hosagoudar & Mathew Dan 2011. Creative Commons Attribution 3.0 Unported License. JoTT allows unrestricted use of this article in any medium for non-profit purposes, reproduction and distribution by providing adequate credit to the authors and the source of publication.

Acknowledgements:We thank Dr. A. Subramoniam, Director, TBGRI, Palode for the facilities and Dr. R. Rejukrishnan for locating its new populations.

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Curcuma bhatii (R.M. Sm.) Skornickova & M. Sabu (Paracautleya bhatii R.M. Sm.) (Zingiberaceae) is an endemic, threatened plant (Nayar & Sastry 1988). It is the smallest southern Indian Zingiberaceae with a height of 12–15 cm (Sabu 2006) (Image 1a), having short rhizomes. It grows in the crevices of laterite rocks. It is found in a few scattered populations in Udupi District, Karnataka State, which is its type locality. The plant goes under dormancy for about six months by withering its aerial portion. Since, it is difficult to establish it in ex situ, it prompted us to study its microbial association which plays an important role in the nutrition of the plants. This plant was collected from its natural habitat for the mycorrhizal study and the voucher specimen is deposited in TBGRI (Mathew Dan no. 67521).

Methods: The rhizosphere soil sample of the plant was collected for isolation of arbuscular mycorrhizal spore by wet sieving and decanting method (Gerdemann & Nicolson 1963). Root hairs were cut into small pieces (ca. 1cm), decolourised by boiling them in 10% KOH for one hour, cooled to room temperature, washed thoroughly in distilled water, stained with Lactophenol-cotton-blue to study the presence of vesicles and arbuscules (Philips & Hayman 1970).

The percentage of mycorrhizal colonization was calculated as: (No. of mycorrhizal root segments / Total no. of root segments observed) x 100

The relative frequency of spores was calculated as: (No. of isolate for each species / Total no. of isolates) x 100

Fungal spores were identified on the basis of spore morphology (Schenk & Perez 1990).

Result: Root colonization and AM spore count were determined. Curcuma bhatiirevealed 95% infection (based on the above formula) and showed about 290 spores per 100g soil. Vesicles and hyphae were present in the roots. The mycorrhizal infection restricted to the epidermis and did not penetrate in to endodermis. Hyphae 2–7 µm broad. Vesicles globose to elongate, 25–50 x 17–20 µm, present in both intercellular and intracellular layer of cortical cells. Spores isolated from the rhizosphere soil belonged to Glomus aggregatum, G. glomerulatum, G. multicaule and Sclerocystis pachycaulis. The spores of Glomus aggregatum and Sclerocystis pachycaulis showed maximum relative frequency (Table 1).

Glomus aggregatum Schenck & Smith, 1982

Mycologia 74 (1): 80, 1982.(Image 1 b,c)

Material examined: 24.vii.2010, spores isolated from the rhizosphere soil of Curcuma bhatii (R.M. Sm.) Skornickova & M. Sabu (Zingiberaceae), Udupi District, Karnataka, coll. P.P. Rajeshkumar, Slide no. TBGT 141.

Chlamydospores formed in loose clusters or in sporocarps without peridium. Sporocarps are of variable size ranging from 800–1000 µm, hyaline to light yellow with a greenish tint in transmitted light. Chlamydospores globose, subglobose, obovate, irregular, 40–50 x 40–50 µm, hyaline to yellow; wall yellow to yellowish-brown, 1–3µm thick, outer wall slightly thicker and lighter in colour than the inner wall. Hyphae at the point of attachment to spore up to 8µm wide. Spore contents continuous with hyphal contents in young spores but get separated from the hyphal content in older spores by the inner spore wall; pore not occluded by hyphal wall thickening. Hyphal attachment straight to recurved sharply at the base of the spores.

Glomus glomerulatum Sieverding

Mycotaxon 29: 74, 1987 (Image 1d)

Material examined: 24.vii.2010, spores isolated from the Rhizosphere soil of Curcuma bhatii (R.M. Sm.) Skornickova & M. Sabu (Zingiberaceae), Udupi District, Karnataka, coll. P.P. Rajeshkumar, Slide no. TBGT 144.

Chlamydospores globose, yellowish-brown, up to 64µm in diam. Composite spore wall composed of two wall layers (wall 1 & 2) in one group (group A); wall 1 is yellow to brown, laminate and up to 3µm thick, on the surface of this wall a layer of hyphae is adherent but normally the spore surface is smooth; wall 2 is hyaline, membranous, up to 0.5µm thick and normally adherent to wall 1. Chlamydospores have two attached hyphae, yellow, straight to recurved. The pore of the hyphal attachment 1.6µm in diam. The pore is closed by second wall. Spore content hyaline, oily.

Glomus multicaule Gerdmann & Bakshi, 1976

Trans. Brit Mycol. Soc. 66 (2): 340, 1976 (Image 1e)

Material examined: 24.vii.2010, spores isolated from the Rhizosphere soil of Curcuma bhatii (R.M. Sm.) Skornickova& M. Sabu (Zingiberaceae), Udupi District, Karnataka, coll. P.P. Rajeshkumar, Slide no. TBGT 142.

Sporocarps not seen. Chlamydospores dark brown, 167–200 µm in diam., subglobose with four hyphal attachments, attachments generally occur at opposite ends of the spore. Spore wall up to 15µm thick, thickest at the point of hyphal attachments, rounded projections up to 1.6µm, regularly distributed over the wall surface.

Sclerocystis pachycaulis Wu & Chen, 1985

Taiwania 31: 74, 1986 (Image 1f)

Sporocarp yellowish-brown, globose, 200–280 µm, consisting of terminal chlamydospore arranged on a central plexus of hyphae. Peridium not seen. Chlamydospores yellow to yellowish-brown, ovoid to ellipsoid, 32–40 x 22–27 µm, wall yellowish-brown, up to 3µm thick, with hyaline, separable outer layer, <1µm thick, usually chlamydospore content separated by 1–2 adventure septa below the spore attachment of attached hyphae. Attached hyphae up to 6.5µm with thick wall. Wall thickness of attached hyphae extending down for some distance, usually thicker than the chlamydospore wall.

Discussion

The plants grow on the shallow deep soil on rocks and crevices where the soil appears to be poor in nutrients, a condition which favours mycorrhizal fungi. Soil analysis study may prove this statement. Presence of characteristic mycorrhizal association points out the habitat specificity of this narrowly endemic species.

References

Gerdemann, J.W. & T.H. Nicolson (1963).Spores of mycorrhizal Endogonespecies extracted from soil by wet sieving and decanting. Transactions of the British Mycological Society46: 235–244.

Nayar, M.P. & A.R.K. Sastry (1988). Red Data Book of Indian Plants.BSI, Calcutta, 250-251pp.

Phillips, J.M. & D.S. Hayman (1970). Improved procedures for clearing roots and staining parasitic and vesicular-arbuscular mycorrhizal fungi for rapid assessment of infection. Transactions of the British Mycological Society 55: 158–161.

Sabu, M. (2006). Zingiberaceae and Costaceae of South India.Indian Association for Angiosperm Taxonomy, Calicut University, India, 144pp.

Schenk, N.C. & Y. Perez (1990). Manual for the Identification of VA Mycorrhizal Fungi. Synergistic Publications, USA, 1–286pp.