Ascospore release and discharge distances of Fusarium graminearum under controlled temperature and relative humidity

López-Giráldez

et al. 2019

mBio

Fungal diversity has amazed evolutionary biologists for decades. One societally important aspect of this diversity manifests in traits that enable pathogenicity. The opportunistic pathogen Chaetomium globosum is well adapted to a high-humidity environment and produces numerous secondary metabolites that defend it from predation. Many of these chemicals can threaten human health. Understanding the phases of the C. globosum life cycle in which these products are made enables better control and even utilization of this fungus. Among its intriguing traits is that it both is self-fertile and lacks any means of propagule-based asexual reproduction. By profiling genome-wide gene expression across the process of sexual reproduction in C. globosum and comparing it to genome-wide gene expression in the model filamentous fungus N. crassa and other closely related fungi, we revealed associations among mating-type genes, sexual developmental genes, sexual incompatibility regulators, environmentally responsive genes, and secondary metabolic pathways.

Section: Discussionsupporting

confidence: 89%

Integrative Activity of Mating Loci, Environmentally Responsive Genes, and Secondary Metabolism Pathways during Sexual Development of Chaetomium globosum

López-Giráldez

et al. 2019

mBio

“…Sutton (1982) and Paulitz (1996) found that wet conditions during evening and night are optimal for ascospore release and dispersal. Persistent wetness is associated with a higher number of perithecia on host tissues and plant debris under natural conditions (Sutton, 1982; David et al, 2016; Manstretta and Rossi, 2016).…”

Section: Discussionmentioning

confidence: 99%

Screening of Oat Accessions for Fusarium Head Blight Resistance Using Spawn‐Inoculated Field Experiments

et al. 2018

Use of resistant cultivars is one of the most important measures to reduce the risk of Fusarium head blight (FHB, caused by various Fusarium spp.) and mycotoxins in cereals. Research on resistance to FHB has mainly focused on wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) and is very limited in oat (Avena sativa L.). In Norway, routine testing of cultivars and breeding lines has been performed in spawn‐inoculated field experiments with Fusarium graminearum Schwabe as part of a concerted research and breeding effort to improve FHB resistance in oat. Data on FHB symptom, days to flowering, and plant height have been collected during the field seasons. Together with the field data, deoxynivalenol (DON) content and germination capacity of harvested kernels are used to score resistance levels of genotypes. In this paper, results are presented from a combined analysis of data from 9 yr of field trials from 2008 to 2016. Consistent and highly significant differences in DON content and germination capacity were documented among the current oat cultivars on the Norwegian market. These two negatively correlated parameters are used as selection criteria in breeding since they are relevant for the different end uses of the grains: DON content for use as food and feed, and germination capacity for seed production. In the paper, we discuss the pros and cons of the various screening methods and parameters used in assessing FHB resistance in oat and present the progress made in resistance breeding based on an established field testing methodology.

Fungal Genetics and Biology

“…It has been shown in both field investigations (David et al, 2016a;Inch et al, 2005;Paulitz, 1996) and laboratory studies (Trail et al, 2002;Tschanz et al, 1976) that meteorological parameters such as light (Schmale III et al, 2005b;Schmale III et al, 2006;Trail et al, 2002), relative humidity (David et al, 2016a;Paul et al, 2007;Paulitz, 1996), and temperature (Del Ponte et al, 2009;Fernando et al, 2000;Paulitz, 1996;Sutton, 1982) may be required at specific levels to trigger ascospore release events. The active release of ascospores from an opening in the ascus has been associated with high levels of relative humidity (David et al, 2016a;David et al, 2016b;Paulitz, 1996;Reis, 1990). The impact of relative humidity, along with other meteorological parameters, on the required compression forces on perithecia warrants future investigation.…”

Section: Discussionmentioning

confidence: 99%

“…High levels of relative humidity (Inch et al, 2005;Paul et al, 2007;Paulitz, 1996;Trail et al, 2002) and low air temperature (Del Ponte et al, 2009;Fernando et al, 2000;Sutton, 1982) have been correlated with F. graminearum ascospore discharge. Additionally, several meteorological conditions have been identified as causal agents of ascospore release (David et al, 2016a), and the numbers and distances of ascospore release have been investigated using 3D-printed discharge devices indicating differences based on temperature and relative humidity (David et al, 2016b). A laboratory-based study of ascospore discharge identified forces of 870,000 g during ascospore release and suggested that fluctuations in Cland K + ions may play a role in ascospore release (Trail et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Compression tests of Fusarium graminearum ascocarps provide insights into the strength of the perithecial wall and the quantity of ascospores

David

Reinisch

Trail

et al. 2016

Self Cite

The plant pathogenic ascomycete Fusarium graminearum produces perithecia on corn and small grain residues. These perithecia forcibly discharge ascospores into the atmosphere. Little is known about the relationship among the strength of the perithecial wall, the age of the perithecium, and the quantity of ascospores produced. We used a mechanical compression testing instrument to examine the structural failure rate of perithecial walls from three different strains of F. graminearum (two wild type strains, and a mutant strain unable to produce asci). The force required to compress a perithecium by one micrometer (the mean perithecium compression constant, MPCC) was used to determine the strength of the perithecial wall. Over the course of perithecial maturation (5-12days after the initiation of perithecial development), the MPCC was compared to the number of ascospores contained inside the perithecia. The MPCC increased as perithecia matured, from 0.06Nμm at 5d to 0.12Nμm at 12d. The highest number of ascospores was found in older perithecia (12d). The results indicated that for every additional day of perithecial aging, the perithecia become more resilient to compression forces. Every additional day of perithecial aging resulted in ∼900 more ascospores. Knowledge of how perithecia respond to external forces may provide insight into the development of ascospores and the accumulation of turgor pressure. In the future, compression testing may provide a unique method of determining perithecial age in the field, which could extend to management practices that are informed by knowledge of ascospore release and dispersal.