Microflora of wheat (Triticum aestivum L.) in Buenos Aires Province (Argentina) and its possible significance in biological control of foliar pathogens

Micro-organisms on the leaf surface of Triticum aestivum L. were examined. The wheat leaves were collected from experimental fields in six localities of Buenos Aires Province (Argentina). Thirteen mycelial fungi, two yeasts a nd a bacterium belonging to the genus Bacillus (Bw/97) were isolated from w heat foliage and evaluated for effectiveness in suppressing Alternaria trit icimaculans, Bipolaris sorokiniana, Drechslera tritici-repentis and Septori a tritici under controlled conditions. Antagonistic activity was examined w ith the dual cultures method on potato dextrose agar media among 10 of thes e microorganisms against the four foliar pathogens. Mycelial growth inhibit ion and colony interactions in all possible paired combinations were evalua ted. The results are discussed in relation to the biological control of the se cereal pathogens. In this work, the importance of indigenous antagonists in wheat disease suppression and the possibility of managing ecosystem con ditions in order to enhance natural biological control is suggested. In our assays, Aspergillus niger, Bw/97 and Nigrospora sphaerica showed a strong inhibitory effect in vitro against the average of the four necrotrophic fun gi tested and justify further evaluation for biocontrol of wheat foliar pat hogens. The others antagonists ranked variably among the assays. Greenhouse bioassays and field evaluations using these isolates are currently under i nvestigation.