AN INTRODUCTION-DISEASES OF WHEAT

Abstract

On average, about 20% of the global wheat production is lost due to diseases and pests every year. In 2021, these losses amounted to about 165 million tons, equivalent to about $35 billion. Fungal pathogens like rusts (Puccinia sp.), Septoria leaf blotch (Septoria sp.), powdery mildew (Blumeria graminis) and Fusarium species are ranked among the top ten of the most important fungal pathogens. Historical and current sources report epidemics leading to sometimes devastating yield losses in wheat caused by these pathogens. In regions with low productivity where no seed dressing is conducted, smuts and bunts are also important pathogens. Furthermore, in specific wheat-growing areas, fungal pathogens such as Pyrenophora tritici-repentis causing tan spot, Oculimacula spp. causing eye spot of wheat or Cochliobolus sativus are of importance. one option to avoid yield losses caused by these pathogens is the application of fungicides. However, the repeated use of fungicides induces a considerable selection pressure on respective pathogens resulting in fungicide resistance or tolerance, which has been detected already in B. graminis, Septoria spp. or Fusarium spp. The application of fungicides also depends to some extent on grain prices, fungicide costs and the possibility of applying these at the right time. Hence, cultivars carrying resistances are the most environment-friendly and cost-effective way of preventing yield losses in wheat. In particular, resistances against leaf rust, stripe rust, stem rust and powdery mildew infections result in complete resistance, but are at risk to be overcome by virulent isolates due to the extensive spore production of these pathogens.