Biology subjects

von Tiedemann, A.

Publications and source records attributed to von Tiedemann, A..

5 recordsLinked to original sources

bioRxiv2025

Effect of fungicides and cultivar on cereals to T. afroharzianum ear infection in the field related to fungicide treatment and crop cultivar

Members of the genus Trichoderma are widely recognized as beneficial fungi and frequently applied as biocontrol agents. However, recent studies have identified Trichoderma afroharzianum as a pathogenic species, capable of infecting maize, wheat, and barley under greenhouse conditions. Its pathogenic potential in small-grain cereals under field conditions, however, has been so far unexplored. To evaluate its pathogenic potential, two-year field trials (2023 and 2024) were conducted using ten wheat, five barley, two rye, and one triticale cultivar. Artificial inoculation was carried out at full flowering using a spray inoculation with pathogenic T. afroharzianum isolates obtained from maize and water as control. Three fungicides were applied: untreated control, foliar treatment before inoculation, and ear application after inoculation. Disease development was assessed based on colonization rate of harvested kernels, and thousand kernel weight (TKW). The results showed significant differences in susceptibility between and within cereal species. T. afroharzianum was able to colonize wheat and barley ears under field conditions, with some cultivars showing significant reduction in TKW and high colonization rate. In contrast, rye and triticale exhibited much lower infection rates. Fungicide treatments had varying levels of efficacy. Ear application after flowering was most effective in reducing colonization and preventing yield loss, whereas early foliar treatment showed limited effect. These findings indicate that T. afroharzianum may represent a relevant pathogen in cereal production adding a new ear disease in cereals and requiring monitoring and enhanced fungicide applications in the future, unless less susceptible cultivars are identified and utilized in practice.

pathology↗

bioRxiv2025

Partial cross-resistance of oats to different Fusarium species and the role of trichomes in susceptibility

Resistance of oats to FHB, caused by different Fusarium species, is important for grain quality and yield. In this study, 25 oat genotypes were evaluated for resistance to Fusarium graminearum (FG), F. sporotrichioides (FS) and F. poae (FP) in field trials across Germany to assess the presence of cross-resistance and to analyse the role of trichomes on the hulls during Fusarium infection. Infection severity was quantified by Fusarium species-specific qPCR and showed the highest fungal biomass for FP, followed by FS and FG. Variability due to environmental effects was very high, resulting in rather low heritabilities for FG (0.50) and FS (0.36), and no significant genotype effect for FP. A significant positive correlation was found between FP and FS infection, whereas FG infection was not correlated with either FP or FS. Microscopic analyses revealed important genotype-specific differences in trichome size and density on lemma and palea with very high heritability (0.97). FG biomass was positively correlated with trichome size and density, and FG hyphae were observed in close interaction with trichomes and stomata. These results indicate the presence of partial cross-resistance in addition to mostly species-specific resistance and suggest a role for trichomes in susceptibility to FG.

plant biology↗

bioRxiv2024

Phylogenetic analysis of pathogenic and non-pathogenic Trichoderma isolates from plants, soil and commercial bio products Short titel: Phylogenetic analysis of pathogenic and non-pathogenic Trichoderma isolates

Fungi of the genus Trichoderma are found worldwide in various types of soil, plant rhizospheres, and plant materials. Several Trichoderma spp. are used in crop health management to promote growth and control plant diseases. Although widely considered beneficial, some members have been reported to be pathogenic to maize, causing a disease called Trichoderma ear rot. Since 2018, T. afroharzianum has caused significant infections of maize cobs in Germany, France and Italy. This study aimed to investigate the pathogenicity and phylogenetic relationships among different Trichoderma strains from diverse sources and geographical origins. Species identification and phylogenetic analysis were performed by sequencing internal transcribed spacer (ITS), translation elongation factor 1- (TEF1-) and RNA polymerase II subunit B (RBP2) genes, and pathogenicity was tested by artificially inoculating maize cobs under controlled greenhouse conditions. A total of 131 isolates were analyzed and assigned to 20 Trichoderma species. Among these, 39 isolates from six species were pathogenic, causing symptoms of green spore layers between kernels and husk leaves. While previous studies primarily identified T. afroharzianum as the main species causing Trichoderma ear rot, this study found that isolates of T. asperellum, T. atroviride and T. guizhouense also exhibit pathogenicity on maize cobs. Additionally, Trichoderma strains from commercial biocontrol products displayed unexpected pathogenicity inducing up to 92% disease severity on maize cobs. Most T. afroharzianum strains induced high levels of disease severity, although some isolates of the same species did not cause any disease, indicating a large heterogeneity in pathogenicity within the species. Notably, phylogeny reconstruction based on the TEF1- and RBP2 genes, did not result in any discernible clustering between pathogenic and non-pathogenic isolates. A further novel finding is the isolation of pathogenic Trichoderma isolates from soil, demonstrating that soil can serve as a reservoir for pathogenic species. This study highlights the need for careful selection and monitoring of Trichoderma strains for agricultural use, considering their beneficial and pathogenic potential. Author SummaryIn this study, we explored the ability of different Trichoderma species to infect maize plants. Trichoderma is a group of fungi known for its beneficial role in agriculture, often used as a biological pesticide to control fungal plant diseases. However, some species within this group can also act as pathogens, causing infections in crops like maize. We found that one species, T. afroharzianum, is particularly aggressive, capable of infecting maize without the plant being wounded first. This makes it a potentially serious threat to crop health. In contrast, other species, such as T. atroviride and T. asperellum, only caused infections when the maize was already damaged. Our research suggests that pathogenic Trichoderma species not only effectively infect plants but can also survive well in soil, making their control difficult. These findings highlight the need for better understanding of how these fungi operate in order to manage the risks they pose to important crops like maize, while still taking advantage of their beneficial uses in agriculture.

microbiology↗

bioRxiv2022

Fusarium culmorum produces NX-2 toxin simultaneously with deoxynivalenol and 3-acetyl-deoxynivalenol or nivalenol

Fusarium culmorum is a major pathogen of grain crops. Infected plants accumulate deoxynivalenol (DON), 3-acetyl-deoxynivalenol (3-ADON), or nivalenol (NIV), which are mycotox-ins of the trichothecene B group. These toxins are also produced by F. graminearum species complex. New trichothecenes structurally similar to trichothecenes B but lacking the carbonyl group on C-8, designated NX toxins, were recently discovered in atypical isolates of F. graminearum from North America. Only these isolates and a few strains of a yet to be characterized Fusarium species from South Africa are known to produce NX-2 and other NX toxins. Here we report that among 20 F. culmorum strains isolated from maize, wheat, and oat in Europe and Asia over a period of 70 years, 18 strains produced NX-2 simultaneously with 3-ADON and DON or NIV. Rice cultures of strains producing 3-ADON accumulated NX-2 in amounts corresponding to 2-8% of 3-ADON (1.2 - 36 mg/kg). A strain producing NIV accumulated NX-2 and NIV at comparable amounts (13.6 and 10.3 mg/kg, respectively). In F. graminearum, producers of NX-2 possess a special variant of cytochrome P450 monooxygenase encoded by TRI1 that is unable to oxidize C-8. In F. culmorum, producers and non-producers of NX-2 possess identical TRI1; the reason for the production of NX-2 is unknown. Our results indicate that production of NX-2 simultaneously with trichothecenes B is a common feature of F. culmorum. Key resultIsolates of Fusarium culmorum obtained from different hosts at different locations over several dec-ades produced NX-2, which is a type A trichothecene structurally related to 3-ADON.

microbiology↗

bioRxiv2020

Population history of the Northern corn leaf blight fungal pathogen Setosphaeria turcica in Europe

Modern agricultural practices and the climate change foster the rapid spread of plant pathogens like the maize fungal pathogen Setosphaeria turcica, which causes Northern corn leaf blight and expanded into Central Europe since the 1980s. To investigate the rapid expansion of S. turcica we sequenced 121 isolates from Europe and Kenya. Population genomic inference revealed a single genetically diverse cluster in Kenya and three clonal lineages with low diversity and one cluster of multiple clonal sublineages in Europe. Phylogenetic dating suggests that all European lineages originated by sexual reproduction outside Europe and subsequently were subsequently introgressed multiple times. In contrast to Kenyan isolates, European isolates did not show sexual recombination despite the presence of both MAT1-1 and MAT1-2 mating types. Coalescent analysis of the geographically most widespread European lineage supported a neutral, strongly exponential population growth model over models with natural selection caused by host defence resistance or environmental adaptation. Within clonal lineages, we observed phenotypic variation in virulence to different monogenic resistances that may originate from repeated mutations in virulence genes. Association mapping between genetic clusters did not identify genomic regions associated with pathogen races but uncovered strongly differentiated genomic regions between clonal lineages that harbor putative effector genes. In conclusion, the expansion and population growth of S. turcica in Europe was mainly driven by the expansion of maize cultivation area and not by rapid adaptation. Significance statementThe geographic expansion and plant pathogens caused by modern agricultural practices and climate change is a major problem in modern agriculture. We investigated the rapid spread of the maize fungal pathogen Setosphaeria turcica by whole genome sequencing of isolates from Kenya and Europe and demonstrated that the rapid expansion in Central Europe since the 1980s mainly reflects the rapid growth of the maize cultivation area in this region and not a rapid adaptation to resistant maize varieties. Our analyses show that by monitoring whole genome sequence diversity of plant pathogens and their invasion history, agricultural management and breeding strategies can be developed to control the evolution and future spread of plant pathogens.

evolutionary biology↗