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KMID : 0379119990270040283
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Korean Journal of Mycology
1999 Volume.27 No. 4 p.283 ~ p.288
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Impact of Environmental Factors on in vitro Interactions and Niche Overlap between Aspergillus ochraceus and other Storage Fungi
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Magan, Naresh
이향범/유승헌/Lee, Hyang Burm/Yu, Seung Hun
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Abstract
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The effect of water activity (a_w, 0.9∼0.995) and temperature (18∼30℃) on in vitro growth and interactions between ochratoxin-producing Aspergillus ochraceus and six other fungi (Alternaria alternata, Aspergillus candidus, A. flavus, A. niger, Eurotium amstelodami, E. rubrum) isolated from maize grain were investigated. A. ochraceus and each six other species were paired and their interactions given a numerical score to obtain an index of dominance (I_D) for each species. Generally A. ochraceus was very competitive and dominant against other fungi. It was, however, dominanted by Alternaria alternata and A. niger at high a_w (0.995 a_w), and mutually antagonistic when paired with E. amstelodami and E. rubrum at low a_w (0.9 a_w). The growth rates of each species were also calculated under the same range of environmental conditions. They were markedly influenced by a_w and temperature. At high temperature (30℃), A. ochraceus grew most rapidly under slightly drier conditions (0.95 a_w), while A. alternata, A. flavus and A. niger did at high water availability level (0.995 a_w). At 18℃ and 25℃, and high a_w level (0.995 a_w), A. alternata grew fastest, while A. candidus, E. amstelodami and E. rubrum grew very slowly. Using Biolog plates the effect of a_w and temperature on utilization patterns of carbon sources in maize was evaluated. The niche overlap index (NOI) relative to A. ochraceus was determined and compared with that of each interacting species. Under high water available condition (0.995 a_w) the NOI of A. ochraceus was often $gt;0.9, indicative of the coexistence with other interacting species. However, against E. amstelodami and E, rubrum at 18℃, the species had NOI $lt;0.8, indicative of occupation of different niches. At low a_w (0.95 a_w), NOI for A. ochraceus was $lt;0.8 when paired with A. alternata and A. niger also suggested the occupation of different niches.
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