Potential of a rhizobacterium Bacillus subtilis (Bbv 57) on Fusarium oxysporum f. sp. gerberae and Meloidogyne incognita infecting Gerbera grown in protected cultivation

Abstract

Ninety five bacterial strains were isolated from the rhizosphere and soils of flower crops, specifically gerbera, carnation and tuberose, were preliminarily screened against Fusarium oxysporum f. sp. gerberae in vitro along with five elite strains Bbv 57, EPCO 16, EPC 5, EPC 8 and Pf 1 obtained from Department of Plant Pathology, TNAU, Coimbatore, India. The results revealed that the strain Bbv 57 had highest inhibition of 50.00% and showed the maximum value for the assays that is siderophore, hydrogen cyanide, IAA, GA3 and salicylic acid production (3.68 O.D. value; 14.05 µg ml-1; 44.40 µg ml-1; 25.28 µg ml-1 and 19.25 µg ml-1 respectively). It also showed resistance to antibiotics namely ampicillin, erythromycin, clindamycin. The highest exopolysaccharides, biofilm production was observed and had lowest protease production clearly indicated that it is non - pathogenic to plants. Further, the polymerase chain reaction using16S rRNA intervening sequencing showed 100% homology to Bacillus subtilis (KF718836) and showed positive for quorum sensing regulator genes of aiiA and comQ. Additionally, the culture filtrate assay also produced significant reduction in egg hatching capacity and juvenile mortality of root-knot nematode Meloidogyne incognita. Further, the HPLC study showed 91.69 µg µl-1 of surfactin with the retention time of 2.304 min and 0.453 µg µl-1 of Iturin with the retention time of 8.739 min at 205 nm. Whereas, GCMS analysis has detected the aliphatic hydrocarbons responsible for antifungal, antibacterial and nematicidal activity.