Potential bio-herbicide from Streptomyces sp. KR0005 to control weeds in a horticultural field

ABSTRACT Herbicidal active metabolites obtained from actinomycetes provide valuable sources in the search for new candidates. They might be striking alternatives to synthetic herbicides. In the present study, actinobacteria strains were isolated from soil samples and their herbicidal activities were screened. In the screening, Streptomyces sp. strain KR0005 broth culture exhibited the highest phytotoxic activity. Thus, it was selected for further studies. The herbicidal active compound purified from this selected strain was identified as cycloheximide (MW, 281.; C15H23NO4) based on 1H-NMR, 13C-NMR, 2D-NMR, and high-resolution electrospray ionisation mass spectrometry analyses. Dose–response experiments revealed that the GR50 value of Digitaria ciliaris was 1.37 g L−1 to Streptomyces sp. strain KR0005 culture filtrate. In general, the inclusion of v/v 0.1% of LES270 (Alcohols, (C12-14), ethoxylated, mono ethers with sulphuric acid, sodium salts) and SF90 (Alcohols, C12-14-secondary, ethoxylated) surfactants resulted in a 14.3% decrease and a 24.1% increase in herbicidal activity, respectively, compared with Tween-20 (Polyoxyethylene sorbitan monolaurate). Mode of action experiments revealed that the KR0005 culture filtrate acted as both photosynthesis and cell membrane integrity inhibitors in a dose-dependent manner. However, further studies such as mutation and/or specific culture conditions are needed to increase the herbicidal activity of this selected strain.