Herbicidal activity of Beauveria sp. from Tibetan Plateau biome against Avena fatua L.

Avena fatua L. is the most persistent weed faced by Chinese farmers, and it accounts for serious losses in several cereal crops. To study the effects of secondary metabolites of microorganisms on A. fatua, experiments were conducted on their herbicidal activity both in vitro and in vivo. In this study, a total of nine strains were isolated from saline-alkaline soil. Among these, the inhibitory effect of culture filtrate from isolate NO.6 on A. fatua seed germination reached 91%, which was similar to that of quizalofop-p-ethyl in vitro test. At 1.5 mg mL(-1) extract concentration of isolate NO.6, plant height and shoot fresh weight of A. fatua was reduced by 100% and 90%, respectively, compared with the control in vivo test. Using chromatography technology, the purified component from NO.6 presented 87.7% reduction of plumule length and 93.2% reduction of radicle length, which was identified as beauverine. The host range test was conducted on plants from the families Poaceae, Fabaceae, Brassicaceae, Apiaceae, Solanaceae, and Amaranthaceae, and the beauverine at a concentration of 1 mg mL(-1) exhibited 66-82% selective inhibition against the first family only, when assayed. Code NO.6 microorganism was identified as a strain of Beauveria sp. based on morphological characteristics and ITS-rDNA analysis. The results proposed that the metabolites of isolate NO.6 inhibited the germination of A. fatua seeds and the growth of seedlings, and its herbicidal effects are selective for monocotyledons while being safe for dicotyledons.