Abstract: The diversity of Aspergillus from soil of teak dominated kusmi forest an Indian subtropical teak forest of Gorakhpur, has been studied and compared with earlier reports. The nine species of Aspergillus namely A. aculeatus, A. carbonarius, A. deflectus, A. fischeri, A. niger, A. phoenicis, A. puniceus, A. sparsus and A. wentii were unaffected and uniformly distributed over the time period. There has been substantial loss of 12 species of Aspergillus namely A. carneus, A. deflectus, A. melleus, A. panamensis, A. petrakii, A. puniceus, A. quardilineatus, A. rugulosus, A. sparsus, A. subolivaceus, A. sulphureus and A. terricola which were reported in earlier study. A total of four species namely A. flavor-furcatis, A. oryzae, A. tubingensis and A. zonatus were supposed to be new because none of literature have reported earlier about those four. The shift in the diversity of Aspergillus might be due to changes in the vegetation of the forest over the time.
INTRODUCTION
Soil is a rich habitat for the growth of microorganisms with fungi as one of the dominant group. Fungi live, multiply and die or disintegrate in the soil and thus they provide rich organic matter, which could be recycled as plant nutrition. Members of the genus Aspergillus have been of interest for centuries because of their positive impact as fermenting agents, metabolite producer and because of their negative impact as degraders of agricultural products, their toxicity and their pathogenicity. Recent scientific interests in biogeography and biodiversity, as well as the increasing importance of Aspergilli as causal agents of mammalian toxicity and disease have led to an increased need to understand where these fungi occur in nature. Most published work on the global distribution of Aspergilli in soils has been descriptive, based on the knowledge and experience of the individual authors (Waksman, 1916; Raper and Fennell, 1965). There have been several studies done on diversity of fungi isolated from different forest soils in India (Kamal and Bhargava, 1972, 1973; Manoharachary, 1977; Rao and Manoharachary, 1981; Rao et al., 1984; Reddy et al., 1987; Manoharachary et al., 1989, 1990; Mohanty and Panda, 1994; Ananda and Sridhar, 2004; Rane and Gandhe, 2006; Tangjang et al., 2009), which complies the diversity and distribution of fungi in India, while diversity of filamentous soil fungi from worldwide have also studied by several workers for evaluation of different factors responsible for distribution of these fungi (Stanlake, 1977; Klich, 2002; Suhail et al., 2007; Donner et al., 2009; Kostadinova et al., 2009). The diversity of Aspergillus from soil of kusmi forest, District Gorakhpur, (26°45’N and 83°24’20”E India) has been extensively studied earlier (Gupta, 1975). The present study provides a comparative account of shift in the diversity of Aspergillus from soil of kusmi forest with the earlier reports.
MATERIALS AND METHODS
Study Sites
The site for the present study was an area of about ten hectares of kusmi
forest in District Gorakhpur, (26°45’N and 83°24’20”E
India). This present study is an serious effort carried between September 2004
to January 2007. The forest is the result of purely planned afforestation scheme
with a dominant teak (Tectona grandis) vegetation along with certain
annual and seasonal vegetation. The soil is alluvial, coarse-sandy and friable
in nature. The color of the soil is dark brown to yellow depending on the site
and type of vegetation.
Sampling
For sampling a 15 cm deep pits were bored at the site of soil collection
by means of soil auger. Half a centimeter soil from the ground surface was removed
so as to eliminate litter and other fallen materials. A total of 10 different
soil samples covering the entire area were subjected to air dry at room temperature
for 5 days prior to isolation of Aspergillus.
Culture Conditions
The different isolates of Aspergillus from the collected soil samples
were isolated by plating method on standard Potato Dextrose Agar (PDA) media.
The characterization of different isolates of Aspergillus was carried
out on Czapek Dox agar Medium (Raper and Fennel, 1965).
Characterization of Aspergillus Isolates
The different isolates of Aspergillus were identified and grouped
in genera and species based on standard morphological (macroscopic and microscopic)
and cultural features (Raper and Fennel, 1965).
Documentation and Computer Analysis
The diversity of Aspergillus isolates were statistically evaluated
using SPSS window 12.0 version software.
RESULTS
The site for the present study has experienced drastic changes in the vegetation including trees and annuals as reported earlier (Gupta, 1975). The comparative account of the status of tree vegetation over the time is shown in Table 1 with dominant teak vegetation presently, instead of teak there are 15 tree species was found during the time of earlier study carried by Gupta (1975). The present vegetation is enriched with Delbergia sissoo and Shorea robusta while there has been total loss of 15 tree species which were observed in earlier study (Gupta, 1975). There have been variations in the population of different annuals observed in both studies with significant loss of many of the species and inclusion of different annuals in the present time. The status of 72 annuals has been compared in the present study (Table 2) revealing a significant loss of several annuals over the time.
| Table 1: | Comparative account of the tree vegetation |
| Table 2: | Comparative account of the annual vegetation |
A loss of 37 annuals and inclusion of 22 new annuals were observed in the present study while the status of 13 annuals remained same (Table 3). The changes in the vegetation have direct influence in the microflora of soil (Klich, 2002).
| Table 3: | One-sample statistics analysis of diversity of Aspergillus using SPSS software |
The Aspergillus isolates from different soil samples have been compared with the earlier reports revealing a significant shift in the diversity of Aspergillus in terms of number of species. The diversity of Aspergillus based on one way sample statistical analysis and test of significant t-test with 5% degree of freedom is provided in Table 3 and 4, respectively. The statistical analysis revealed the uniform presence of nine species namely A. aculeatus, A. carbonarius, A. deflectus, A. fischeri, A. niger, A. phoenicis, A. puniceus, A. sparsus and A. wentii in the present study similar to what has been reported earlier. There has been substantial loss of 12 species of Aspergillus namely A. carneus, A. deflectus, A. melleus, A. panamensis, A. petrakii,A. puniceus, A. quardilineatus, A. rugulosus, A. sparsus, A. subolivaceus, A. sulphureus and A. terricola when compared with earlier reports (Table 4).
| Table 4: | One-sample t-test analysis for diversity of Aspergillus using SPSS software |
The diversity of Aspergillus in the present study further revealed the occurrence of four species namely A. flavor-furcatis, A. oryzae, A. tubingensis and A. zonatus not reported earlier (Gupta, 1975). The diversity of Aspergillus in terms of number of strains of different species revealed A. flavus to be the dominant species as compared to A. niger in the earlier report (Gupta, 1975) as shown in Table 4.
DISCUSSION
The comparative account of diversity of Aspergillus isolated from soil of same forest reveals the influence of vegetation in distribution of micorflora of soil. The monoculture teak vegetation of the forest during the recent time resulted in shift in the diversity of Aspergillus as this group of fungi being saprotrophs is directly influenced by litter and humus composition of the soil (Ananda and Sridhar, 2004). Further it has been reported that there exists strong relation between litter and humus composition with type of vegetation on the same soil (Bardgett and Shine, 1999; Klich, 2002; Samson and Hong, 2006). The present study clearly indicates the shift in the diversity of Aspergillus isolated from soil samples of kusmi forest as compared to earlier studies revealing the direct influence of vegetation on the population of microflora of a particular soil as suggested in earlier reports (Mohanty and Panda, 1994; Rane and Gandhe, 2006; Tangjang et al., 2009). The monoculture teak vegetation of kusmi forest in the recent past has resulted in changes in the diversity of Aspergillus with elimination of some species and occurrence of some new species and also in terms of frequency of occurrence of different species when compared with earlier study carried out at same site. It is quite obvious that since there has been shift in the vegetation of study site, the soil also undergoes changes in the composition of microbial flora as a result of which a drastic changes in the Aspergillus population is observed (Klich, 2002).
The present investigation on comparative account of the biodiversity of indigenous isolates of Aspergillus provides interesting out comes as discussed above. Loss of some species Aspergillus from this region is a serious issue concerning with conservation of microbes diversity, such type of losses can’t be recovered. The change in composition of diversity of Aspergilli especially in occurrence of frequency of species and their shift may cause the harm to other microflora as well as microfauna which also need to be investigated further. The present study is a basic research in compositional shifting of Aspergilli in respect of change in higher vegetations, which certainly open so many aspects to think and work in the direction of microbial conservation and typing for further biological and biotechnological applications.
ACKNOWLEDGMENTS
The authors are thankful to Head, Department of Biotechnology, D.D.U. Gorakhpur University, Gorakhpur, India for providing infrastructural facilities. One of Author V.K. Morya is thankful to CSIR, New Delhi for financial assistance as Senior Research Fellowship.