Soil bacteria as selective biological control agents of winter annual grass weeds in winter wheat

Abstract

Many winter annual grass weeds, such as downy brome ( Bromus tectorum L.) and jointed goatgrass Aegilops cylindrica Host.), are difficult to control selectively in winter wheat ( Triticum aestivum L.) grown in the central and western US. The difficulty is due partially to a lack of selective chemical herbicides. Bacteria were isolated from soil and plant roots and evaluated for inhibition of germination and root and shoot growth of both weeds and wheat. Laboratory bioassays identified 162, 202, and 129 isolates that inhibited root growth of downy brome, Japanese brome ( B. japonicus Thunb. ex. Murr.), and jointed goatgrass, respectively. Nine isolates inhibited downy brome shoot and root growth in soil in pot studies. In a field study established in the fall of 1990 under adverse environmental conditions (high temperature/low moisture), application of two isolates increased winter wheat yields as compared to untreated wheat ( P = 0.10).