2018 ASHS Annual Conference

Herbicides are used to control weeds in agricultural systems and to beneficially shift the competition between crops and weeds. Despite their importance, few new mechanisms of action have been elucidated in recent decades. Here, we describe the identification of a bio-derived herbicidal mixture from an endophytic bacterium named MS79. The MS79 strain was isolated from switchgrass tissue. A preparation of concentrated cellular material disturbs the biosynthesis cellulose in plants exposed to the mixture. Accordingly, isolation with XAD18 resin to purify metabolites results in a herbicidal mixture with similar activity against cellulose biosynthesis. The application of the MS79 to a range of plant genera suggests that it caused substantial reduction in cellulose content Sorghum bicolor L and other monocotylenous plants. However, Solanaceous broad leaf crops, for instance Nicotiana tobaccum and Solanum lycopersicum, are less sensitive. The genome of MS79 was sequenced, revealing the presence of plant-microbe association genes and several genes encoding proteins capable of binding to or degrading plant cell wall carbohydrates. Thus, we propose that MS79 is a Class L herbicide, with specificity towards grass control in Solanaceous crops.