A comparative study of the efficiency of several sources of induced resistance to powdery mildew (Blumeria graminis f. sp. tritici) in wheat under field conditions

In comparison with untreated controls, both synthetic and biologically sourced inducers of resistance significantly decreased the severity of powdery mildew in a 3-year, small-plot experiment which included other cultivars with varying resistance to powdery mildew as reference, on the susceptible winter wheat cultivar, Kanzler. The most prominent effects were observed following treatments with benzothiadiazole, extracts made of ginger (Zingiber officinale Roscoe) and curcuma (Curcuma longa L.) rhizomes, and giant knotweed (Reynoutria sacchaliensis L.) leaves, which were highly efficient in all 3 years of the experiment. Other inducers such as oak bark (Quercus robur L.) extract, salicylic acid as well as a solution of glycine betaine were also effective. All inducers under study had halted disease progress by 27 d after application. The induced resistance was long-lasting and the severity of the disease, when compared with the untreated control, was decreased to between 2% and 53%, depending upon the year.