Claviceps species affecting Paspalum spp. are a serious problem, as they infect forage grasses such as Paspalum dilatatum and P. plicatulum, producing the ergot disease. The ascomycete C. paspali is known to be the pathogen responsible for this disease in both grasses. This fungus produces alkaloids, including ergot alkaloids and indole-diterpenes, that have potent neurotropic activities in mammals. A total of 32 isolates from Uruguay were obtained from infected P. dilatatum and P. plicatulum. Isolates were phylogenetically identified using partial sequences of the genes coding for the second largest subunit of RNA polymerase subunit II (RPB2), translation elongation factor 1-α (TEF1), β-tubulin (TUB2), and the nuc rDNA 28S subunit (28S). Isolates were also genotyped by randomly amplified polymorphic DNA (RAPD) and presence of genes within the ergot alkaloid (EAS) and indole-diterpene (IDT) biosynthetic gene clusters. This study represents the first genetic characterization of several isolates of C. paspali. The results from this study provide insight into the genetic and genotypic diversity of Claviceps paspali present in P. dilatatum and suggest that isolates from P. plicatulum could be considered an ecological subspecies or specialized variant of C. paspali. Some of these isolates show hypothetical alkaloid genotypes never reported before.

Paspalum L. is a genus of the Poaceae family, with many species serving as well-adapted forage plants in subtropical climates and continuous grazing systems. However, Claviceps paspali, an ascomycete of the order Hypocreales, represents a major threat to the Paspalum species. This fungus induces ergot disease, characterized by the replacement of infected flower seeds with sclerotia, which adversely affects seed production and animal health through mycotoxin production. Although ergot disease is reported in many countries, no totally resistant Paspalum cultivars have been reported for commercial use. This study comparatively evaluated disease development in six Paspalum species under greenhouse conditions with three specific isolates of C. paspali, along with field trials. In addition, field isolates of C. paspali were analyzed for phenotypic characteristics and phylogenetic relationships. Greenhouse evaluation revealed variable susceptibility among Paspalum species, with P. malacophyllum, P. notatum, and P. umbrosum being the most resistant. In field trials P. dilatatum showed the highest severity index, and P. umbrosum and P. malacophyllum were less affected. The phenotypic characterization of 22 C. paspali isolates showed variability in pigmentation and growth rates, with potato dextrose agar being the culture medium in which the highest growth rate was observed. Phylogenetic analysis of the isolates identified two well-supported lineages between C. paspali species. This research reports an ergot resistance gradient among Paspalum species, identifying genuine sources of resistance. In addition, virulent isolates of C. paspali potentially useful for rapid screening of accessions or crosses in Paspalum breeding programs were identified. [ ] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

The ability of entomopathogenic fungi, such as Beauveria bassiana, to infect insects by penetrating their cuticle is well documented. However, some insects have evolved mechanisms to combat fungal infections. The red flour beetle (Tribolium castaneum), a major pest causing significant economic losses in stored product environments globally, embeds antifungal compounds within its cuticle as a protective barrier. Previous reports have addressed the contributions of non-cuticular infection routes, noting an increase in mortality in beetles fed with conidia. In this study, we further explore the progression and dynamics of oral exposure in the gut of T. castaneum after feeding with an encapsulated B. bassiana conidia formulation. First, we characterized the formulation surface using atomic force microscopy, observing no significant topological differences between capsules containing and not containing conidia. Confocal microscopy confirmed uniform conidia distribution within the hydrogel matrix. Then, larvae and adult insects fed with the conidia-encapsulated formulation exhibited B. bassiana distributed throughout the alimentary canal, with a higher presence of conidia before the pyloric chamber. More conidia were found in the larval midgut and hindgut compared to adults, but no germinated conidia were observed in the epithelium. These results suggest that the presence of conidia obstructs the gut, impairing the insect’s ability to ingest, process, and absorb nutrients. This disruption may weaken the host, increasing its susceptibility to infections and, ultimately, leading to death. By providing the first direct observation of fungal conidia within the alimentary canal of T. castaneum, this study highlights a novel aspect of fungal–host interaction and opens new avenues for advancing fungal-based pest control strategies by exploiting stage-specific vulnerabilities.

Ergot disease (Claviceps paspali) and sterility have the potential to reduce seed yield in bahiagrass (Paspalum notatum Flüggé). Our objective was to determine the genotypic and environmental effects on seed yield, and the levels of ergot and sterility. Seventeen genotypes were evaluated in three locations across two years for seed yield, ergot severity, and total seed fractions (percentage of full seeds, ergot sclerotia and empty seeds). The percentage of full seeds and total seed yield were correlated (r = 0.52) but both were negatively correlated with the percentage of ergot sclerotia (r = −0.81 and −0.51). Empty seeds were negatively correlated with full seeds (r = −0.39), but not with ergot sclerotia and total seed yield. The genotype effect was significant for total seed yield and severity of infection with large heritabilities (H² = 0.92 and 0.86) but had no effect on the percentage of the seed fractions. Location and the interaction with genotype explained most of the variation in the percentage of the seed fractions and their weight. Ergot and sterility were significant detrimental factors, genotype was a major determinant of ergot levels and seed yield, while non-genetic factors were co-determinants in constructing the seed yield potential but were the main determinants of the yield potential realization.