In vitro characterization of interspecific interaction between Streptomyces spp. and aflatoxigenic Aspergillus spp. on peanut meal agar

RUFFINO, M.; PASSONE, M.A.; ETCHEVERRY, M.G.

Villa Carlos Paz, Córdoba, Argentina

Congreso; MYCO-GLOBE Advances in research on toxigenic fungi and mycotoxins in South America ensuring food and feed safety in a myco-globe context; 2006

Chulze, Dalcero, Resnik, Pacin

The goal of the present work was to select bacteria belonging to the Streptomyces genus from peanut soil with antagonistic ability on Aspergillus spp. aflatoxigenic isolated from peanut grains. To Streptomyces  isolation, soil sampling was done in peanut fields in three peanut-growing regions of Córdoba Province, Argentine: Chucul, General Cabrera and Coronel Moldes. The isolation percentages were 90.6%, 77.7% and 50%, respectively. Eleven Streptomyces isolates were selected to carry out the assays. Two Aspergillus section Flavi strains, A. flavus SE64 and A. parasiticus SE243 isolated from peanut grains were used. To establish clearly the interspecific interaction between the fungi and antagonist, the carbohydrates profiles utilization, dominance index (ID) and antibiosis were determined (La Penna, et al. 2004). The last ones were carried out at different water conditions (0.982, 0.955, 0.937 aW) and at 25°C on peanut meal agar. From niche overlap index (NOIs) were selected 9 Streptomyces isolates that showed values of NOIs between 0.91/1 and 1/1 at 0.982 aW. Four of these isolated showed antibiosis reduced considerably the sporulation in the contact zone of the A. parasiticus SE243 strains at 0.982 and 0.955 aW. The results showed that Streptomyces RC4GC, RC6GC, RC11GC and RC9CM isolates have potential competitiveness. Subsequent studies to evaluate the impact on growth and aflatoxin accumulation will be done.   References La Penna, M., Nesci, A. and Etcheverry, M. (2004) In vitro studies on the potential for biological control on Aspergillus section Flavi by Kluyveromyces spp. Letters in Applied Microbiology 38: 257-264.