Influence of water deficit on the phytotoxicity of imazamethabenz and fenoxaprop among five wild oat populations

Abstract

Growth chamber studies were carried out on the effect of soil water deficits on the phytotoxicity of imazamethabenz and fenoxaprop in four genetically distinct lines (CS 40, SH 430, AN 51, MON 73) and one natural population of wild oat ( Avena fatua L.). In the absence of drought, SH 430 was relatively more susceptible than the other lines to imazamethabenz and fenoxaprop; MON 73, a short, abundantly tillering line, was somewhat more tolerant to fenoxaprop than the others; and CS 40, the most vigorous of the populations, was slightly more tolerant to both herbicides. Water deficits had limited adverse influence on the phytotoxicity of imazamethabenz in the populations examined. The phytotoxicity of fenoxaprop was greatly reduced by long-term water stress in all populations, but was more variable under short-term drought conditions. The differential responses among the populations to these two herbicides did not appear to be directly related to their intrinsic drought tolerance, characteristic growth habit, or to their level of seed dormancy. Such interaction may still be of adaptive significance to the survival of this troublesome weed.