In vitro selection of maize rhizobacteria to study potential biological control of Aspergillus section Flavi and aflatoxin production

A.. NESCI; R. BLUMA; M. ETCHEVERRY

EUROPEAN JOURNAL OF PLANT PATHOLOGY

Springer Science + Business Media B.V., Kluwer Academic Publishers B.V

Año: 2005 vol. 113 p. 159 - 171

0929-1873

The aims of this study were to select bacterial isolates from the non-rhizophere of maize soil and to examine their antagonistic activity against Aspergillus section Flavi strains. The first selection was made through ecophysiological responses of bacterial isolates to water activity (aw) and temperature stress. Subsequently, an Index of Dominance test (ID), ecological similarity and inhibition of the lag phase prior to growth, growth rate and aflatoxin B1 accumulation were used as criteria. From the first assay nine bacterial strains were selected. They grew well at 25 and 30ºC, with growth optima between 0.982 and 0.955 aw using 48 h of incubation. There was ecological similarity between the bacterial strains Bacillus subtilis (RCB3, RCB6), Pseudomonas solanacearum RCB5, Amphibacillus xylanus RCB27 and aflatoxigenic Aspergillus section Flavi strains at 0.982 at 25ºC. The predominant interaction between all selected bacteria and fungi in dual culture was mutual intermingling at 0.982. Mutual inhibition on contact and mutual inhibition at a distance was observed at 0.955 aw, between only four bacteria and some Aspergillus strains. Bacillus subtilis RCB55 showed antifungal activity against Aspergillus section Flavi strains. Amphibacillus xylanus RCB27, B. subtilis RCB90 and Sporolactobacillus inulinus RCB196 increased the lag phase prior to growth and decreased the growth rate of Aspergillus section Flavi strains. Bacillus subtilis strains (RCB6, RCB55, RCB90) and P. solanacearum RCB110 inhibited aflatoxin B1 accumulation at 0.982 aw. These results show that the bacterial strains selected have potential for controlling Aspergillus section Flavi over a wide range of relevant environmental conditions in the stored maize ecosystem.