Antifungal activity of indigenous Bacillus spp. isolated from soil

Abstract

Biocontrol using plant growth-promoting rhizobacteria (PGPR) represents an alternative approach to disease management, since PGPR are known to promote growth and reduce diseases in various crops. Among the different PGPR, members of the genus Bacillus are prefered for most biotechnological uses due to their capability to form extremely resistant spores and produce a wide variety of metabolites with antimicrobial activity. The objective of this research was to identify antagonistic bacteria for management of the plant diseases. Eleven isolates of Bacillus spp. were obtained from the soil samples collected from different localities in the Province of Vojvodina. The antifungal activity of bacterial isolates against five fungal species was examined using a dual plate assay. Bacillus isolates exhibited the highest antifungal activity against Fusarium proliferatum, Fusarium oxysporum f. sp. cepae and Alternaria padwickii, while they had the least antagonistic effect on Fusarium verticillioides and Fusarium graminearum. Molecular identification showed that effective bacterial isolates were identified as Bacillus safensis (B2), Bacillus pumilus (B3, B11), Bacillus subtilis (B5, B7) and Bacillus megaterium (B8, B9). The highest antagonistic activity was exhibited by isolates B5 (from 39% to 62% reduction in fungal growth) and B7 (from 40% to 71% reduction in fungal growth). These isolates of B. subtilis could be used as potential biocontrol agents of plant diseases.

Biokontrola fitopatogena predstavlja alternativu primeni pesticida, s obzirom da bakterije označene terminom PGPR (Plant Growth Promoting Rhizobacteria) stimulišu biljni rast i štite biljke od bolesti. Zahvaljujući sposobnosti da formiraju veoma rezistentne endospore i produkuju širok spektar antimikrobnih supstanci, vrste roda Bacillus su veoma zastupljene u zemljištu i pogodne za primenu u biotehnologiji. Cilj istraživanja bio je da se utvrdi antifungalna aktivnost jedanaest Bacillus spp. izolata iz zemljišta s različitih lokaliteta u Vojvodini. Sposobnost bakterijskih izolata da inhibiraju rast pet izolata gljiva ispitana je metodom dvojne kultivacije. Izolati Bacillus spp. ispoljili su najveću antifungalnu aktivnost prema Fusarium proliferatum, Fusarium oxysporum f. sp. cepae, i Alternaria padwickii, dok je najmanji antagonistički efekat utvrđen prema Fusarium verticillioides i Fusarium graminearum. Efektivni izolati identifikovani su kao Bacillus safensis (B2), Bacillus pumilus (B3, B11), Bacillus subtilis (B5, B7) i Bacillus megaterium (B8, B9). Najveću antifungalnu aktivnost ispoljili su izolati B. subtilis B5 (39-62%) i B7 (40-71%). Ovi izolati mogu se koristiti kao potencijalni agensi za biološku kontrolu biljnih bolesti.