Environmental factors, <e1>in vitro</e1> interactions, and niche overlap between <e1>Fusarium moniliforme</e1>, <e1>F. proliferatum</e1>, and <e1>F. graminearum</e1>, <e1>Aspergillus</e1> and <e1>Penicillium</e1> species from maize grain (Sonia Marín and others)

The effects of temperature and water availability on growth and interactions between fumonisin-producing isolates of <e1>Fusarium moniliforme</e1> and <e1>F. proliferatum</e1> and seven other fungi from maize grain were determined <e1>in vitro</e1>. The type of interaction and index of dominance (<e1>I</e1><inf>D</inf>) between species were markedly influenced by temperature and <e1>a</e1><inf>w</inf>. Generally, <e1>F. moniliforme</e1> and <e1>F. proliferatum</e1> were very competitive and dominant against the <e1>Penicillium</e1> spp. and <e1>A. flavus</e1>. They were in turn dominated by <e1>A. niger</e1>, but mutually antagonistic when paired with <e1>F. graminearum</e1> and <e1>A. ochraceus</e1>. Under slightly drier conditions (&lt;0·98 <e1>a</e1><inf>w</inf>) <e1>A. ochraceus</e1> became more competitive and dominant over the fumonisin-producing species. <e1>A. flavus</e1> was dominant only at 30°C and &lt;0·96 <e1>a</e1><inf>w</inf>. <e1>F. moniliforme</e1> and <e1>F. proliferatum</e1> demonstrated dominance against all species over a range of temperatures and 0·994 to 0·96 <e1>a</e1><inf>w</inf>. At lower <e1>a</e1><inf>w</inf> levels they were less competitive. The growth rate of the two fumonisin-producing species was significantly reduced by <e1>F. graminearum</e1>, regardless of <e1>a</e1><inf>w</inf>. <e1>F. moniliforme</e1> and <e1>F. proliferatum</e1> reduced growth of <e1>Penicillium</e1> and <e1>Aspergillus</e1> spp., especially at >0·96 <e1>a</e1><inf>w</inf>. At &lt;0·96 <e1>a</e1><inf>w</inf>, growth of these species was unaffected. Using Biolog plates the effect of <e1>a</e1><inf>w</inf> and temperature on utilization patterns of carbon sources in maize were evaluated for the first time. The niche overlap indices relative to <e1>F. moniliforme</e1> and <e1>F. proliferatum</e1> were determined and compared with that of each interacting species. NOIs for <e1>F. moniliforme</e1> and <e1>F. proliferatum</e1> were >0·90 at >0·96 <e1>a</e1><inf>w</inf> and 25 and 30°, indicative of co-existence with other species. Most of species had NOIs >0·90, except in some cases when paired with <e1>F. moniliforme</e1>, where NOIs &lt;0·80 suggested the occupation of different niches. Although there was no significant correlation between the I<inf>D</inf> and NOI methods both suggested that the niche overlap between species was in a state of flux and significantly influenced by both temperature and water availability. This suggests that interpretation of <e1>I</e1><inf>D</inf>, or NOIs carried out under one set of environmental conditions may be misleading when considering interactions between species and also where screening for biocontrol potential is being considered.