AUXIN PRODUCTION AND ANTIFUNGAL ACTIVITY OF BACILLUS SPP. PROMOTING THE GROWTH OF HELIANTHUS ANNUUS L.

Abstract

The rhizobacterial strains were evaluated for auxin production and their effectiveness in improving the growth of Helianthus annuus L. Colorimetric analysis of bacterial auxin showed that MS-1, MS-6, and MS-2 produced 51, 32, and 21.5 µg/mL of auxin respectively at 1000 µg/mL concentration of L-tryptophan. Fourier Transform Infrared Spectroscopy (FTIR) was also performed to detect bacterial auxin production. The ability of bacterial isolates to produce ammonia and hydrogen cyanide was tested. All the strains produced ammonia. In the hydrogen cyanide test, except the MS-10 strain all gave positive results. The biocontrol potential of bacterial strains was also evaluated by performing antifungal assay against Fusarium oxysporum. The strains MS-6 and MS-10 showed significant antifungal activity against F. oxysporum. The pot trials were performed by inoculating the seeds of H. annuus in single and mixed cultures under natural conditions. This inoculation greatly improved the plant growth by increasing the shoot length, fresh and dry weight. The strain MS-6 increased the shoot length by 33.6% when compared with the control. Compared to the control, MS-2 elevated the fresh and dry weight by 58% and 77% respectively. Results showed that rhizobacterial strains have the potential to enhance plant growth and control fungal pathogens in laboratory trials.