Abstract
Bioactive herbicidal compounds produced by soil microorganisms might be used to creating a bioherbicide for biological weed control. A total of 1,300 bacterial strains were isolated and screened for herbicidal activity against grass and broadleaf weeds. Among primarily selected 102 strains, the herbicidal activity of bacterial fermentation broths from the following three isolates strain-101, strain-128, and strain-329 reduced the growth of D. sanguinalis by 66.7%, 78.3%, and 100%, respectively as compared with control. Phylogenetic analysis of 16S rRNA gene sequencing determined that the strain-329 has 99% similarity to Streptomyces anulatus (HBUM 174206). The potential bioherbicidal efficacy of Streptomyces strain-329 was tested on grass and broadleaf weeds for phytotoxic activity through pre- and post-emergence applications. At pre-emergence application, the phytotoxic efficacy to D. sanguinalis and S. bicolor on seed germination were 90.4% and 81.3%, respectively at the 2x concentration, whereas in the case of Solanum nigrum, 85.2% phytotoxic efficacy was observed at the 4x concentration. The efficacy of Streptomyces strain-329 was substantially higher at post-emergence application, presenting 100% control of grass and broadleaf weeds at the 1x concentration. Two herbicidal compounds coded as 329-C1 and 329-C3 were extracted and purified by column chromatography and high-performance liquid chromatography methods. The active compound 329-C3 slightly increased leaf electrolytic leakage and MDA production as concentration-dependent manner. These results suggest that new Streptomyces sp. strain-329 produced bioherbicidal metabolites and may provide a new lead molecule for production an efficient bioherbicide to regulate grass and broadleaf weeds.
Highlights
Weeds are the main problem in crop production, causing substantial losses to the yield
Researches on the development of bioherbicides and their phytotoxic metabolites have been expanded in many countries that may play a major role towards sustainability in agriculture [4]
The host range test conducted on these selected three isolates showed that strain-329 reduced growth with severe lesions and serious injury such as yellowing, leaf spots, and blight on the foliage of D. sanguinalis, which eventually led to the plant death
Summary
Weeds are the main problem in crop production, causing substantial losses to the yield. Researches on the development of bioherbicides and their phytotoxic metabolites have been expanded in many countries that may play a major role towards sustainability in agriculture [4]. Several researchers declared that naturally derived bioherbicides are effective substances for weed control, thereby provide ecological advantages and maintain sustainable agricultural production [5, 6]. Secondary metabolites produced by these species cause plant phytotoxic activities such as necrosis, chlorosis, deformation and stunting[7]. These features are prerequisite to use them as bioherbicides for weed control [8]. Weak herbicidal activity is the main constrains towards the development and large-scale use of bioherbicides [11, 12]. Recent findings revealed that phytotoxic metabolites vary in their degree of target-specificity, though weed species may differ in susceptibility to a particular toxin [14]
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