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Symbiotic response of patchouli (Pogostemon cablin (Blanco) Benth. to different arbuscular mycorrhizal fungi.

Introduction

Patchouli in an erect, branched, pubescent herb, with oblong-ovate coarse leaves belonging to family Lamiaceae. It is the source of patchouli oil and is a native of Philippines. The essential oil is used in perfumery industry and also as a flavour ingredient in major food products including alcoholic beverages, candies, baked goods, meat and meat products. The fresh leaves have medicinal value and are used as a decoction with other drugs to treat nausea, diarrhea, cold and headaches.

Arbuscular mycorrhizal (AM) fungi are a ubiquitous group of soil fungi colonizing the roots of plants belonging to more than 90% of plant families [8]. Enhanced plant growth due to AM association is well documented [3]. This has gained momentum in recent years because of the higher cost and hazardous effects of heavy doses of chemical fertilizers. These fungi are known to improve the nutritional status of the host, particularly that of phosphorous, and thereby enhance their growth, development and yield [6,4].

The extramatrical hyphae produced by AM fungi act as extensions of roots and increase the surface area of the root system, making it more efficient for absorption of water and diffusion limited nutrients, this effect being more pronounced in P-deficient soils [5]. Other beneficial effects are in the biological control of root pathogens, biological nitrogen fixation, hormone production and increased ability to withstand water stress. Though not host specific, earlier studies have indicated host preferences of mycorrhizal fungi [23,27], thus suggesting the need for selecting efficient AM fungi for a particular host [1,12]. Hence in the present investigation it was envisaged to screen and select an efficient AM fungus that can be used for inoculating patchouli, in the nursery.

Materials and methods

A green house experiment was conducted to evaluate the response of patchouli to inoculation with various AM fungi. The soil used in this study was collected from an uncultivated field from a depth of 0-15 cm and has been classified as fine, kaolinitic, isohyperthermic, kanhaplustalfs. The soil had a pH of 5.6 (1: 10 soil to water extract ratio), and it contained 2.7 ppm available phosphorus (extractable N[H.sub.4]F+HCl) and an indigenous AM mycorrhizal population of 58 spores /50 g of soil.

The patchouli seedlings, one month old, were procured from CIMAP Resource Centre, Bangalore. The seedlings were transplanted to polythene bags of size 25x12 cm holding 4 kg of substrate. The substrate used was sand: soil: vermicompost mixture in 1: 1: 0.25 v/v/v ratio.

The AM fungal species used in this study were either isolated or obtained from different places as mentioned in Table 1. These fungi were multiplied using sterilized sand: soil mix (1:1 v/v) as the substrate and Rhodes grass as the host. After 80 days of growth, shoot of Rhodes grass was severed and the substrate containing hyphae, spores and root bits was air dried and used as inoculum. The inoculum potential (IP) of each culture was estimated adopting the most probable number (MPN) method [26]. The mycorrhizal inoculum (12,500 IP) was applied to the planting hole at a depth of about 5 cm just before transplanting. The uninoculated treatment received 5 ml of the washings of AM inoculum suspension passed through 45 micro meter sieve which contained associated microorganisms but not the AM propagules

The experimental design was completely randomized design with 20 replications for each treatment. The plants were maintained in a green house under 50% shade net and watered whenever necessary. Ruakura plant nutrient solution without phosphorus was applied @ 50 ml /plant at 30 days interval. A spray of bavistin 1ml/L was sprayed at an interval of 60 days to prevent wilt disease.

The plant parameters like plant height (measured from soil surface to the growing tip of the plant), number of branches and spread (both in east west and north south directions) were recorded at 30 days interval after planting (DAP). However, only observations recorded on 150 DAP are presented in this paper. The plants were harvested 150 DAP. Shoot and root dry weights were determined after drying the plant samples at 60[degrees]C to a constant weight o in a hot air oven.

The phosphorus content of the shoot and root was determined by the vanado--molybdate phosphoric acid yellow color method outlined by Jackson [16]. The essential oils in the aromatic plants were separated and estimated after steam distillation [13]. The extracted oil was subjected to GC analysis and the per cent patchouli alcohol was estimated [18].

The soil samples collected from the root zone were air dried and spore population of AM fungi were estimated by following wet sieving and decantation method described by Gerdemann and Nicolson [10]. The fine terminal feeder roots were removed from the root, washed thoroughly, and stained with trypan blue [25]. The per cent mycorrhizal root colonization was determined by grid line intersect method [11].

The data were analyzed using the completely randomized design, with the help of the computer (microvex system VAX/VMS, version 5.4, Digital Equipment Corporation, USA). The means were compared by Duncan's multiple range test at 5 % level.

Results and discussion

Results

In general, mycorrhizal inoculation resulted in a significant increase in plant height, number of branches, biomass and P content of patchouli plants.

Plant height was highest in plants inoculated with Glomus etunicatum, Glomus intraradices and Glomus macrocarpum all the 3 being on par and differing significantly from other treatments and the least being in the uninoculated control plants (Table 1). Plants inoculated with Glomus etunicatum showed significantly higher number of branches compared to all other treatments. Maximum spread in east-west direction was observed in plants inoculated with Glomus intraradices and Glomus macrocarpum followed by Glomus etunicatum, all the three being on par with each other. The least spread was observed in plants treated with Scutellospora calospora. Similar results were also obtained for plant spread in the north-south direction.

Highest plant biomass was observed in plants inoculated with Glomus etunicatum followed by Glomus intraradices both being statistically on par with each other and differing significantly from other treatments. Plants inoculated with S. calospora had significantly the least plant biomass compared to all other inoculated treatments (Table 1).

All the inoculation treatments showed higher shoot P content and differed significantly among each other. The highest shoot P content was observed in plants inoculated with G. etunicatum and the least P content was observed in uninoculated plants. Similarly in roots, maximum P content was observed in plants treated with G. etunicatum and the least in uninoculated plants (Table 2).

Regarding the essential oil content (which is a measure of the quantity of oil produced), though most of the inoculation treatments had higher oil content, except Scutellospora calospora, the differences were not statistically different compared to the uninoculated treatment. The only treatment in which the essential oil content was significantly higher compared to uninoculated control was the treatment in which plants were inoculated with Glomus etunicatum (Table 2).

The per cent patchouli alcohol (which is a measure of the quality of oil produced), in all the inoculation treatments including uninoculated plants was in the range 30-60%. (Table 2).

In this study highest mycorrhizal colonization was observed in plants treated with G. intraradices, which was statistically on par with the treatment G. leptotichum, (Table 2). Highest number of mycorrhizal spores in the root zone soil was also observed in G. intraradices and G. etunicatum treated plants, both not differing significantly from other inoculation treatments. Least number of spores occurred in the root zone of uninoculated plants.

Discussion

Patchouli plants varied in their response to inoculation with different mycorrhizal fungi. Most of the AM fungi resulted in significant increase in plant height, number of branches, plant spread, plant biomass and P content of patchouli. Host preference among AM fungi has been reported by earlier workers [22,12], hence, the need for inoculating different mycotrophic plants has been stressed [17,4].

Plant height, number of branches and plant spread were significantly greater in plants inoculated with Glomus etunicatum, when compared with uninoculated plants. The next best fungus was Glomus intraradices. Improved plant height, branching and spread because of AM fungal inoculation has been reported in other medicinal plants like coleus [7] and kalmegh [29]. The plant biomass is an important parameter for selecting a fungus for its symbiotic efficiency. Plant biomass (shoot + root) was enhanced by 33.64% due to G. etunicatum inoculation compared with uninoculated plants. The increase in plant biomass because of inoculation with G. intraradices was 33.53% compared with uninoculated plants. Increased plant biomass because of inoculation with AM fungi has been reported in aromatic plants like palmarosa [14], eucalyptus [24], bergamot mint [19] and sweet basil [9].

Increased plant growth due to AMF inoculation is mainly through improved uptake of diffusion limited nutrients such as P [20,21,12]. AM fungi improving plant biomass were also good in increasing the P content of the host, significantly highest being in plants inoculated with G. etunicatum. The increase in shoot P content was 68.69% and root P content was 50.71% respectively in G. etunicatum inoculated plants. Selected efficient fungi enhancing plant biomass and P uptake has been reported in other plants by several workers [30,31]. Such higher P content in AMF inoculated plants is attributed to higher influx of P into the plant system through AM fungi which explores the soil volume beyond P depletion zone [6,15,28]. The essential oil content of patchouli was significantly more only in G. etunicatum plants compared to the uninoculated treatment. Increase in essential oil content in some aromatic plants like rosemary and sweet basil has been reported by earlier workers [2,9]. The per cent patchouli alcohol which is a measure of quality of oil produced was in the range of 30 to 60 (the normal standard prescribed) indicating that the extracted oil is of good quality in all the treatments. The enhancement in growth and nutritional status was also related to mycorrhizal root colonization and spore numbers in the root zone soil. This upholds the observations made by earlier workers on other plants [12,29].

Conclusion

By giving emphasis to parameters like essential oil and plant biomass, and not neglecting the other characteristics Glomus etunicatum is considered to be the most promising symbiont for inoculating patchouli. The nursery technology using AM fungus being simple can easily be adopted by farmers for cultivating this aromatic crop.

References

[1.] Abbott, L.K. and A.D. Robson, 1982. The role of vesicular-arbuscular mycorrhizal fungi and selection of fungi for inoculation. Australian Journal of Agricultural Research, 33: 389-408.

[2.] Anuradha, M.N, 2003. Influence of biofertilizers on growth, yield and quality of essential oil in rosemary (Rosmarinus officinalis. L.) Ph.D Thesis UAS GKVK Bangalore India.

[3.] Bagyaraj, D. J, 1984. Biological interactions with VA mycorrhizal fungi. In: VA Mycorrhiza. Eds., Powell, C.L. and D.J. Bagyaraj. CRC Press, Boca Raton, FL, USA, pp: 131-153.

[4.] Bagyaraj, D.J, 2007. Arbuscular mycorrhizal fungi and their role in Horticulture. In: Recent trends in horticultural biotechnology. Eds., Keshavchandran, R et al., pp: 53-58.

[5.] Bagyaraj, D.J. and B.J.D. Reddy, 2000. Arbuscular mycorrhizas in sustainable agriculture. In: Microbial biotechnology for sustainable development and productivity. Ed., Rajak, R.C. Scientific Pub., Jodhpur, India, pp: 43-53.

[6.] Bagyaraj, D.J. and A. Varma, 1995. Interactions between arbuscular mycorrhizal fungi and plants: their importance in sustainable agriculture in arid and semiarid tropics. Advances in Microbial Ecology, 14: 119-142.

[7.] Boby, V.U. and D.J. Bagyaraj, 2003. Biological control of root-rot of Coleus forskholii Briq. using microbial inoculants. World Journal of Microbiology and Biotechnology, 19: 175-180.

[8.] Brundett, M., 1991. Mycorrhizas in natural ecosystems. Advances in Ecological Research, 21: 171-313.

[9.] Copetta, A., G. Lingua, L. Bardi, G. Masoero, G. Berta, C. Cruz, H. Egsgaard and Trujillo, 2007. Influence of arbuscular mycorrhizal fungi on growth and essential oil composition in Ocimum basilicum var. Genovese. Caryologia, 60: 106-110.

[10.] Gerdemann, J.W. and T.H. Nicolson, 1963. Spores of mycorrhizal Endogone species extracted from soil by wet-sieving and decanting. Transactions of the British Mycological Society, 46: 235-244.

[11.] Giovannetti, M. and B. Mosse, 1980. An evaluation of technologies for measuring vesicular arbuscular mycorrhizal infection in roots. New Phytologist, 84: 489-500.

[12.] Gracy, L. Sailo. and D.J. Bagyaraj, 2005. Influence of different AM fungi on growth, nutrition and forskolin content of Coleus forskohlii. Mycological Research, 109: 795-798.

[13.] Guenther, E., 1949. The Essential Oils, vol-3. D. Von Nostrand and Co. Inc., New York, pp: 552-575.

[14.] Gupta, M.L. and K.K. Janardhanan, 1991. Mycorrhizal association of Glomus aggregatum with palmarosa enhances growth and biomass. Plant and Soil, 131: 261-264.

[15.] Hattingh, M.J., L.E. Gray and L.W. Gerdemann, 1973. Uptake and translocation of [sup.32.P] labeled phosphate to onion roots by mycorrhizal fungi. Soil Science, 116: 383-387.

[16.] Jackson, M.L., 1973. Soil Chemical Analysis. New Delhi: Prentice Hall (India) Pvt. Ltd. pp: 239-241.

[17.] Jeffries, P., 1987. Use of mycorrhizae in agriculture. CRC Critical Review of Biotechnology. 5: 319-357.

[18.] Koul, G.L and S.S. Nigam, 1966. Studies on Indian essential oils Part-1, Chromatography. Perfume and Essential Oil Record, 57: 91-97.

[19.] Kothari, S.K., Saudan Singh, U.B. Singh and Sushil Kumar, 1999. Response of bergamot mint (Mentha citrata) to vesicular arbuscular mycorrhizal fungi and phosphorus supply. Journal of Medicinal and Aromatic Plant Sciences, 21: 990-995.

[20.] Krishna, K.R. and D.J. Bagyaraj, 1991. Role of vesicular arbuscular mycorrhiza in the uptake of micronutrients by ground nut plants. Current Research, 20: 173-175.

[21.] Lambert, D.H., D.E. Baker and H. Cole, 1979. The role of mycorrhizae in the interaction of phosphorus with zinc, copper and other elements. Soil Science Society American Journal, 43: 976-980.

[22.] McGraw and N.C. Schenck, 1981. Effects of two species of vesicular arbuscular mycorrhizal fungi on the development of Fusarium wilt of tomato. Phytopathology, 7: 894-897.

[23.] Miller, R.M., A.G. Jarstfer and J.K. Pillai, 1987. Biomass allocation in an Agropyron smithi- Glomus symbiosis. American Journal of Botany, 74: 114-122.

[24.] Oliveria, V.L.F., L. De Zambolin., J.C.L. Nenes and V.L. De Oliveria, 1995. Growth of eucalyptus seedlings inoculated with mycorrhizal fungi, Fitopatologia Brasilar, 20: 164-168.

[25.] Philips, J.H. and 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.

[26.] Porter, W.M, 1979. The most probable number method for enumerating infective propagules of vesicular-arbuscular mycorrhizal fungi in soil. Australian Journal of Soil Research, 17: 515-519.

[27.] Rajan, S.K., B.J.D. Reddy and D.J. Bagyaraj, 2000. Screening of arbuscular fungi for their symbiotic efficiency with Tectona grandis. Forest Ecology and Management, 126: 91-95.

[28.] Sanders, F.E. and P.B. Tinker, 1971. Mechanism of absorption of phosphate from soil by Endogone mycorrhizas. Nature, 233: 278-279.

[29.] Tharun, C., D.J. Bagyaraj and C.S.P. Patil, 2006. Response of Andrographis paniculata to different arbuscular mycorrhizal fungi. Journal of Agricultural Technology, 2: 221-228.

[30.] Ulfath Jaiba, J., A.N. Balakrishna., D.J. Bagyaraj and J. Arpana, 2006. Screening of an efficient AM fungus for inoculating Piper longum Linn. Journal of Soil Biology and Ecology, 26: 109-116.

[31.] Vasanthakrishna, M., D.J. Bagyaraj and J.P. Nirmalnath, 1995. Selection of efficient VA mycorrhizal fungi for Casuarina equisetifolia--Second screening. New Forests, 9: 157-162.

(1) J. Arpana, (2) D.J. Bagyaraj, (2) E.V.S. Prakasa Rao,

(2) T.N. Parameswaran and (3) B. Abdul Rahiman

(1) Centre for Natural Biological Resources and Community Development, No. 41, RBI Colony, Anand Nagar, Bangalore--560 024. India

(2) Central Institute of Medicinal and Aromatic Plants, Resource Centre, Allalasandra, GKVK PO, Bangalore-560 065. India

(3) Dept. of P.G Studies & Research in Biotechnology, Kuvempu University,Shankaraghatta- 577 451, Shimoga. India.

Corresponding Author

Bagyaraj, D.J., Centre for Natural Biological Resources and Community Development, No. 41, RBI Colony, Anand Nagar, Bangalore--560 024. India.
Table 1: Effect of AM fungi on growth parameters of Patchouli at
150 DAP.

 Plant spread
 cm)
Treatments Plant Number of branc East-west
 height branches/ direction
 (cm) plant

Uninoculated [63.79.sup.c] [10.08.sup.de] [52.25.sup.e]
Acaulospora
 laevis [64.33.sup.c] [10.75.sup.bcd] [52.58.sup.e]
Gigaspora
 margarita [73.67.sup.b] [9.50.sup.e] [54.33.sup.de]
Glomus
 bagyarajii [74.63.sup.b] [10.25.sup.cde] [55.75.sup.cde]
Glomus
 etunicatum [84.58.sup.a] [12.67.sup.a] [61.33.sup.ab]
Glomus
 fasciculatum [71.04.sup.b] [11.25.sup.bc] [54.42.sup.de]
Glomus
 intraradices [81.17.sup.a] [11.67.sup.b] [63.25.sup.a]
Glomus
 leptotichum [76.08.sup.b] [11.08.sup.bcd] [56.42.sup.cd]
Glomus
 macrocarpum [81.75.sup.a] [11.33.sup.bc] [62.83.sup.a]
Glomus
 monosporum [71.85.sup.b] [10.67.sup.bcd] [58.00.sup.bc]
Glomus
 mosseae [74.42.sup.b] [11.33.sup.bc] [58.50.sup.bc]
Scutellospora
 calospora [57.50.sup.d] [10.08.sup.de] [48.50.sup.f]

 Plant spread (cm) Dry weight/plant (g)
Treatments North-south Shoot Root
 direction

Uninoculated [40.17.sup.g] [13.17.sup.cd] [4.78.sup.de]
Acaulospora
 laevis [45.75.sup.ef] [14.58.sup.b] [5.20.sup.cd]
Gigaspora
 margarita [47.75.sup.de] [14.83.sup.b] [5.30.sup.cd]
Glomus
 bagyarajii [49.67.sup.cd] [13.83.sup.bc] [5.37.sup.cd]
Glomus
 etunicatum [57.00.sup.a] [16.67.sup.a] [7.32.sup.a]
Glomus
 fasciculatum [48.00.sup.de] [14.67.sup.b] [5.90.sup.bc]
Glomus
 intraradices [54.08.sup.ab] [17.33.sup.a] [6.64.sup.ab]
Glomus
 leptotichum [47.00.sup.def] [14.33.sup.b] [5.38.sup.cd]
Glomus
 macrocarpum [52.08.sup.bc] [16.33.sup.a] [5.26.sup.cd]
Glomus
 monosporum [48.75.sup.de] [14.92.sup.b] [4.94.sup.d]
Glomus
 mosseae [47.33.sup.de] [14.50.sup.b] [6.42.sup.b]
Scutellospora
 calospora [43.83.sup.f] [12.25.sup.d] [4.11.sup.e]

Means with the same superscript in each column do not differ
significantly at P= 0.05 level by Duncan's Multiple Range Test
DAP--Days after planting

Table 2: Effect of AM fungi on plant P content, essential oil
content, percent patchouli alcohol, percent mycorrhizal root
colonization and spore number in the root zone soil of Patchouli
at 150 DAP.

 P content
 (mg/plant) Oil content
Treatments Shoot P Root P (ml/40g shoot
 sample)

Uninoculated [8.69.sup.k] [4.11.sup.h] [1.46.sup.b]
Acaulospora
 laevis [11.66.sup.h] [5.61.sup.d] [1.55.sup.ab]
Gigaspora
 margarita [13.05.sup.e] [5.51.sup.e] [1.55.sup.ab]
Glomus
 bagyarajii [11.33.sup.i] [5.47.sup.e] [1.62.sup.ab]
Glomus
 etunicatum [14.66.sup.a] [8.34.sup.a] [1.75.sup.a]
Glomus
 fasciculatum [12.92.sup.f] [6.60.sup.c] [1.62.sup.ab]
Glomus
 intraradices [14.53.sup.b] [6.64.sup.c] [1.70.sup.ab]
Glomus
 leptotichum [12.03.sup.g] [5.38.sup.f] [1.55.sup.ab]
Glomus
 macrocarpum [14.37.sup.c] [5.36.sup.f] [1.68.sup.ab]
Glomus
 monosporum [13.12.sup.d] [4.94.sup.g] [1.62.sup.ab]
Glomus
 mosseae [11.31.sup.i] [7.06.sup.b] [1.66.sup.ab]
Scutellospora
 calospora [10.78.sup.j] [4.02.sup.i] [1.23.sup.c]

 Patchouli Colonization Spore number
Treatments alcohol (%) (%) /50 g soil

Uninoculated [46.45.sup.ab] [7.49.sup.e] [67.00.sup.b]
Acaulospora
 laevis [46.25.sup.ab] [37.62.sup.abc] [159.8.sup.ab]
Gigaspora
 margarita [43.72.sup.b] [27.40.sup.cd] [151.6.sup.ab]
Glomus
 bagyarajii [46.65.sup.ab] [31.06.sup.cd] [145.6.sup.ab]
Glomus
 etunicatum [46.67.sup.ab] [46.16.sup.a] [220.4.sup.a]
Glomus
 fasciculatum [45.77.sup.ab] [32.42.sup.bcd] [144.2.sup.ab]
Glomus
 intraradices [46.00.sup.ab] [48.66.sup.a] [221.6.sup.a]
Glomus
 leptotichum [47.32.sup.ab] [46.04.sup.a] [181.4.sup.ab]
Glomus
 macrocarpum [48.15.sup.ab] [46.28.sup.a] [205.6.sup.a]
Glomus
 monosporum [47.57.sup.ab] [45.18.sup.ab] [210.6.sup.a]
Glomus
 mosseae [49.92.sup.a] [45.12.sup.ab] [209.0.sup.a]
Scutellospora
 calospora [43.05.sup.b] [24.14.sup.d] [120.2.sup.ab]

Means with the same superscript in each column do not differ
significantly at P= 0.05 level by Duncan's Multiple Range Test
DAP-Days after planting
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Title Annotation:Original Article
Author:Arpana, J.; Bagyaraj, D.J.; Rao, E.V.S. Prakasa; Parameswaran, T.N.; Rahiman, B. Abdul
Publication:Advances in Environmental Biology
Article Type:Report
Date:Jan 1, 2008
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