European Journal of Experimental Biology Open Access

Key words

Sugarcane field, Biodiversity, Fungal population, Phycomycetes.

Introduction

Soil is a complex ecosystem, delimited by physicochemical parameters that hold enormous number of living organisms. Nevertheless, microbes are the least unstated mechanism of soil by both agronomists and soil practitioners. On the farm several soil organisms offer benefits to crop growing in an ecosystem, but are not well understood. The soil microbes decompose the plant and animal residues entering the soil and convert them into soil organic matter, which influences on soil physical, chemical and biological properties and on creating a complimentary medium for biological reactions and life support in the soil environment. Nonetheless, enhanced site-specific diversity typically results in higher levels of below ground microbial diversity and production (Olson et al., 2000).

Large quantities of readily decomposable organic matter are added to agricultural soils every year as crop residues or animal wastes and have a significant outcome on soil microbial commotion. The plant species growing on the soil also equally influence the population and species composition of the soil fungi. (Hackle et al., 2000).

Microfungi play a focal role in nutrient cycling by regulating soil biological activity (Arunachalam et al., 1997). However, the rate at which organic matter is decomposed by the microbes is interrelated to the chemical composition of the substrate as well as environmental conditions. There have been a number of studies on the distribution of soil microfungi in agricultural field. Some studies dealt with the influence of plant community (Chung et al., 1997) and others attempted to examine seasonal trends (Kennedy et al., 2005).

This study deals with the seasonal variations in soil fungal population of traditional agricultural field in South India.

Materials and Methods

Collection of soil samples

About eight soil samples were collected from the two villages, viz Orathanadu, Pattukottai in Thanjavur District – Tamil Nadu. The soil samples were taken during the four seasons in sugarcane field.

Sampling Schedule

Soil sample was collected in each sampling station seasonally for a period of one year from January 2009 to December 2009. The climate is monsoonic and the calendar year has been divided into four season viz., Post monsoon (January - March), Summer (April - June), Pre monsoon (July - September) and Monsoon (October- December).

Soil Analysis

The mechanical and chemical analysis of the soils were made with the help of Lamotte’s soil testing outfit, Nitrogen and Organic, etc., were estimated as outlined in piper’s book (1950).

Isolation of Soil Mycoflora

Dilution Plating Method

Dilution technique described by Warcup (1950) was used to isolate the fungi from soil sample weighting 1 g was diluted in 10 ml of distilled water. One ml. of the diluted sample was poured and spread on petriplates containing sterilized PDA medium (Extract from 250g of potato (boiled and filtered), dextrose 20g, agar 15 g and distilled water 1000 ml pH 7.0) in replicates. The inoculated plates were incubated in a dust free cupboard at the room temperature for 3 days. One percent streptomycin solution was added to the medium before pouring into petriplates for preventing bacterial growth.

Observation

The colonies growing on PDA plates with different morphology were counted separately. A portion of the growing edge of the colony was picked up with the help of a paw of needles and mounted on a clean slide with lactophenol cotton blue stain. The slide was gently heated in a sprit lamp so as to facilitate the staining and remove air bubbles, if any. The excess stain was removed with the help of tissue paper and then the cover slip was sealed with transparent nail polish. The slide was observed under a compound microscope.

Microphotography of the individual fungal species was also taken using Nikon phase contrast microscope, Japan.

Identification

Colony colour and morphology were noted besides hyphal structure, spore size, shapes and spores bearing structures. They were compared with the standard works of Raper and Thom (1949), Van Arx (1974). Ainsworth et al., (1973); Raper and Fennell (1965) and Ellis (1976) among others for identification of the species.

Presentation of Data

Number of species is referred as species diversity. Populations density expressed in terms of colony forming unit (CFU) per gram of soil with dilution factors.

In order to arrers the dominance of individual species in species site percentage contribution was worked out as follows

Results and Discussion

Fungal Diversity in Sugarcane Soils

Altogether eight soil samples from 2 different stations representing the entire Thanjavur District were examined for fungal diversity. The study resulted the presence of 49 species of fungi in all of them 3 species belonging to two genera were Phycomycetes and the remaining 46 species belonging to 17 genera were assignable to Deuteromycetes.

Table 1

Table 2: Total number of colonies, mean density and percentage contribution of fungi recorded during different season from Thanjavur District (Jan 2009 – Dec 2009)
Station 1 – (Orathanadu)

Table 3: Total number of colonies, mean density and percentage contribution of fungi recorded during different season from Thanjavur District (Jan 2009 – Dec 2009)Station 2 – (Pattukkottai)

Stationwise Occurence

Altogether 27 species belong to 11 genera (1 Phycomycetes, 26 Deuteromycetes) were identified from Orathanadu and 32 species belong to 13 genera (2 Phycomycetes, 30 Deuteromycetes) were identified from Pattukottai.

Species Composition

Among the 17 genera recorded, the genus Aspergillus was considered by more number of (24 species) followed by Trichoderma (4 species) Fusarium and Penicillum (3 species each). All other genera were represented one species each (Table 1).

Species Diversity

Altogether 49 species to 17 genera (3 Phycomycetes, 46 Deuteromycetes) were identified from the station. (Orathanadu, Pattukottai).

In the present investigation the survey was conduct to find out the fungal diversity in two different stations such as Orathanadu and Pattukottai totally 49 species isolated belonging 17 genera from the soil of sugarcane field. Number of Deuteromycetes were representing by 46 species remaining 3 species are Phycomycetes. The dominant species were Aspergillus niger, A. flavus followed by Botrytis cinera, Trichoderma viride, T.harzianum, Penicillium chrysogenum, T.koeningii, T.glaucum, and P.citrinum from the sugarcane field soils of Orathanadu in various seasons whereas, in Pattukottai soils the dominant species were A.niger, Botrytis cinera followed by A.oryzae, Fusarium oxysporum, Gliocladium virens, P.chrysogenum and T.viride respectively.

Recentely Kalai selvi and Panneerselvam (2011) studied that seasonal and depthwise variation of soil fungal population in Thanjavur dist, Tamilnadu viz Nadur, Orathanadu, Punnainallur and Tholkappiyar Square totally 30 different species belonging to Ascomycetes and Phycomycetes were isolated by using PDA medium. The dominant species were Aspergillus niger, Cunninghamella sp. followed by Trichoderma viride. During rainy season maximum fungal count was recorded in sub soil layer.

Evendentely Madhan raj et al., (2010) reported that 45 soil samples were collected from 8 different station along the entire Tamilnadu coast and examined by dilution plating method to access the fungal diversity and their population density. Totally 24 fungal species representing 12 genera recorded Aspergillus was constituted by more number of (9 species) followed by Penicillium (3species) Fusarium and Monodictys (2species each).

Acknowledgement

The authors are grateful to Sri Gowri Biotech Research Academy, Thanjavur for providing laboratory facilities.

References

1. Ainsworth, G.C., Sparrow, F.K. and Sussman, A.S., The fungi – An advanced treatise: A taxonomic review with keys. In : Ascomycetes and fungi Imperfecti. New York; Academic Press, 1973,4(A) : 621pp.
2. Arunachalam, K., Arunachalam, R.S., Tripathi and Pandey, H.N., Trop.Ecol., 1997,38:333- 341.
3. Chung, H., D.R. Zak, P.B. Reich and D.S. Ellsworth., Gobal changeBiol., 2007,13:980-989.
4. Ellis, M.B., More dematiaceous Hyphomycetes. Common wealth mycological institute, Pub., Kew, Survey, England, 1976.
5. Hackel, E.,G. Bachmann and S. Boltenstern-Zechmeister, Phyton, 2000,48:83-90.
6. Kennedy, N.M., D.E. Gleeson, J.Connolly and N.J.W. Clipson, FEMS Microb. Ecol., 2005,53:329-337.
7. Madhan raj, P., Manorajan, S., Nadimuthu, N., and Panneerselvam, A., Advances in Applied Science Research, 2010,1(3):160-167.
8. Olson, R.K., M.M.Schoenherger and S.G. Aschmann, American Society of Agronomy, Madison, Wisconsin, USA., 2000,PP:987-1057.
9. Raper, K.B. and Thom, C., A manual penicillia Baltimore: The Williams and Wilkins Co., 1949,875pp.
10. Selvaraj Kalaiselvi and Annamalai Panneerselvam, Der Chemica Sinica, 2011,2(2):9-19.
11. Raper, K.B. and Fennell, D.I., The genus Aspergillus, Baltimore: The Williams and Wilkins Co., 1965,686pp.
12. Von Arx, J.A., The genera of fungi sporulating in pure culture 2nd edn., Vaduz Germany: A.R. Ganter Verlag, K.G. FL – 9490, 1974,375pp.
13. Warcup, J.H., Nature, 1950,117 – 118.