Influence of iron depletion on interactions between peach bark fungi in vitro

Iron requirements for growth, siderophore production and the interactions between predominant fungal epiphytes (Aureobasidium pullulans, Alternaria alternata, Epicoccum purpurascens, Coniothyrium olivaceum and Cladosporium herbarum) from peach bark were studied in vitro using different levels of iron availability at 15 and 26 C. Growth of these fungi on iron-limiting agar medium amended with the synthetic chelator, EDDHA was reduced. Production of siderophores by Au. pullulans, E. purpurascens and Co. olivaceum was determined by growth and color changes on Czapek's agar supplemented with chromazural-S. The greatest degree of antagonism was observed between pairings with E. purpurascens, CI. herbarum and Co. olivaceum. Aureobasidium pullulans and Al. alternata were the least antagonistic fungi tested. Antagonistic interactions resulting in a deadlock occurred in 25% of interactions. Iron limitation resulted in a significant increase in antagonistic interactions between these fungi. There were no significant differences between the levels of antagonism at 15 C and 26 C.