Towards a better understanding of ash dieback Scientists of the TU Braunschweig discover phytotoxic substance from the ash pathogen

Scientists of the Technische Universität Braunschweig made a significant contribution to the understanding of the European Ash dieback by isolating a previously unknown substance from the pathogen and investigating its destructive character. The metabolite proved to have a germination inhibiting effect towards ash and causes necroses in the plant tissue. The results of their studies were published in the current issue of the journal „Angewandte Chemie“.

One step closer to the understanding of Ash Dieback
The pathogen of ash dieback, the fungus Hymenoscyphus pseudoalbidus, was discovered only a few years ago. This fungus currently invades from Asia and causes effects that are visible since almost two decades. Since the 1990’s a significant part of the ash population in Europe was devastated by the fungus. An important contribution for the revalation of the pathogenicity of this organism was now made by scientists from the Institutes of Organic Chemistry and Microbiology from the TU Braunschweig.

The German scientists around Dr. Jeroen Dickschat and Dr. Barbara Schulz investigated the largely unknown secondary metabolism of the pathogenic fungus. They discovered a volatile lactone (3,4-dimethylpentan-4-olide) in the headspace of agar plate cultures of the fungus for which they used special equipment for headspace analysis (closed-loop stripping apparatus). The Institute of Organic Chemistry is one of the few institutions that have access to and experience with this method, explains Dr. Dickschat.

Biologists then testet the bioactivity of the volatile lactone against seeds of the ash tree. The lactone exhibited a strong germination inhibition towards ash seeds and caused necroses on the seedlings. By this agressive property, the fungus destroys its own host and habitat, comments Dr. Dickschat. The scientists came to the conclusion that only the European Ash is attacked by the lactone, whereas its Japanese sister species seems to be immune.

„We assume that the phytotoxic lactone plays a main role in the pathogenicity of the fungus“, says Dr. Dickschat, „but there are likely more factors involved that may originate from the plant itself.“ The scientists from Braunschweig hope to lay the ground for further work to understand the pathogenicity mechanisms of H. pseudoalbidus and probably pave the way to a control of the disease.