Browsing by Person "Voegele, Ralf T."

Now showing 1 - 2 of 2

First report on the emergence of Neopestalotiopsis rosae as a severe economic threat to strawberry production in Germany
(2024) Schierling, Tom E.; Voegele, Ralf T.; El-Hasan, Abbas; Gonçalves, Micael F. M.
Strawberries hold significant economic importance in both German and global agriculture. However, their yield is often adversely affected by fungal diseases. This study describes Neopestalotiopsis rosae as a newly emerging pathogen responsible for leaf blight and fruit rot in strawberries in Germany. Infected plants were observed in Hohenheim, Germany. A combination of morphological and molecular analyses, along with pathogenicity tests, confirmed the identity of N. rosae as the causal agent. Morphological examination of conidia and mycelium revealed key characteristics including the presence of versicolorous median cells, conidial appendages, black spherical conidiomata formation as well as changing colony color and fluffy texture. These properties align with the established descriptions for the species. Molecular analysis, particularly the sequencing of the internal transcribed spacer and β-tubulin regions allowed the precise identification of the pathogen. Artificial inoculation of healthy strawberry plants with conidial suspension derived from the isolated strain resulted in the development of characteristic symptoms, including necrotic leaf spots and water-soaked fruit lesions, similar to those observed on the original infected plants. To our knowledge, this study presents the first documented occurrence of N. rosae in Germany, highlighting its emergence as a significant threat to strawberry production in Europe.
New approaches to manage Asian soybean rust (Phakopsora pachyrhizi) using Trichoderma spp. or their antifungal secondary metabolites
(2022) El-Hasan, Abbas; Walker, Frank; Klaiber, Iris; Schöne, Jochen; Pfannstiel, Jens; Voegele, Ralf T.
Attempts have been made to determine the in vitro and in planta suppressive potential of particular Trichoderma strains (T16 and T23) and their secondary metabolites (SMs) against Asian soybean rust (ASR) incited by Phakopsora pachyrhizi. Aside from the previously identified SMs 6-pentyl-α-pyrone (6PAP) and viridiofungin A (VFA), the chemical structures of harzianic acid (HA), iso-harzianic acid (iso-HA), and harzianolide (HZL) were characterized in this study. Our results indicate that exposure of urediospores to 200 ppm 6PAP completely inhibits germination. A slightly higher dosage (250 ppm) of HZL and VFA reduces germination by 53.7% and 44%, respectively. Germ tube elongation seems more sensitive to 6PAP than urediospore germination. On detached leaves, application of conidia of T16 and T23 results in 81.4% and 74.3% protection, respectively. Likewise, 200 ppm 6PAP recorded the highest ASR suppression (98%), followed by HZL (78%) and HA (69%). Treatment of undetached leaves with 6PAP, HA, or HZL reduces ASR severity by 84.2%, 65.8%, and 50.4%, respectively. Disease reduction on the next, untreated trifoliate by T23 (53%), T16 (41%), HZL (42%), and 6PAP (32%) suggests a translocation or systemic activity of the SMs and their producers. To our knowledge, this study provides the first proof for controlling ASR using antifungal SMs of Trichoderma. Our findings strongly recommend the integration of these innovative metabolites, particularly 6PAP and/or their producers in ASR management strategies.