Avena fatua L. escapes and delayed emergence in wheat (Triticum aestivum L.) crops of Argentina

Abstract Avenafatua (L.) is one of the most important weed grasses in wheat crops on the most important wheat ( Triticum aestivum L.) production area of Argentina. It is present in 60% of the fields of an area of 750,000 ha not only reducing crop yields but also contaminating the wheat and barley ( Hordeum vulgare L.) grain. The most frequent practice for its control is the application of ACCase inhibitors or ALS inhibitors herbicides. However, the presence of wild oat is frequent in wheat crops at harvest even in those fields where herbicides were applied and thus, regarded as resistant individuals. Thus, the objective of this study was to identify the processes that explain the persistence of wild oat individuals during the crop cycle. Seeds from cultivated and from uncultivated areas were harvested and then the response to ACCase inhibitors and ALS inhibitors herbicides was studied over 20 selected populations from different areas of both conditions (cultivated and uncultivated). Emergence dynamic from seeds of both conditions was also studied and in addition, the effect of mature environment on seeds germination was also assessed. The results indicate that none of the populations were resistant to herbicides studied. However, emergence dynamic was different depending on the seeds coming from agricultural fields or not cropping condition. Seeds from cultivated areas had higher dormancy and emerged later in the field than those from no cropped areas. The ripening environment did not modify the emergence pattern suggesting differences in emergence dynamic are based on genetic nature. These results show dormancy levels and therefore germination and establishment dynamic on the field was hierarchically more important than response to herbicides to favor the persistence of this weed in wheat production systems. Thus, it is still possible to apply proactive agronomic strategies with the aim of avoiding the growth of wild oat populations resistance to herbicides.