Experimental Mycology 

About: Experimental Mycology is an academic journal. The journal publishes majorly in the area(s): Neurospora crassa & Germ tube. It has an ISSN identifier of 0147-5975. Over the lifetime, 764 publications have been published receiving 18448 citations.

The fungicidal effect of chitosan on fungi of varying cell wall composition

Abstract: Chitosan, a deacetylated form of chitin, inhibited the growth of many fungi, including plant and animal pathogens. All fungi tested which reportedly contain chitosan as a cell wall component were insensitive to its fungicidal effects.

Characterization of the smallest chitosan oligomer that is maximally antifungal to Fusarium solani and elicits pisatin formation in Pisum sativum

Abstract: Chitosan (β-1,4-linked glucosamine polymer) oligomers were characterized by their antifungal effect onFusarium solani f. sp.pisi andF. solani f. sp.phaseoli and their ability to elicit pisatin formation in immature pea pods. The antifungal and pisatin-inducing abilities were shown to increase as the polymer size increased. Monomer and dimer units showed no antifungal activity and induced little pisatin. Trimer through pentamer units were antifungal at high concentrations and were moderate in ability to induce pisatin formation. A sharp increase in antifungal activity and pisatin formation was noted for the hexamer unit, while the heptamer unit was maximal in both antifungal activity and formation of pisatin. Chitosan and its derivatives showed maximal activities in both antifungal action and pisatin induction, while chitin and chitin derivatives showed no antifungal activity and only weak pisatin formation activity. These findings show that high-molecular-weight chitosan fragments are more active in both antifungal and pisatin formation activity than are the intermediate and low-molecular-weight fragments. The chitosan oligomers which most effectively induce pisatin and inhibit theF. solani formae speciales are the non-acetylated heptamers.

Role of melanin in appressorium function

Abstract: Appressoria of certain pathogenic fungi appear darkly pigmented due to a discrete cell wall layer of melanin. We have studied the function of appressorial melanin using wild-type and melanin-deficient strains of the rice blast pathogen Magnaporthe grisea and the melanin biosynthesis inhibitor tricyclazole. All appressoria exhibited a single, circular, wall-less pore against the substratum. Pores in both melanized and unmelanized appressoria were circumscribed by a ring of material, the pore ring, which might function to seal the pore-substratum interface. Experimental evidence demonstrated that appressoria adhered tightly to surfaces and that melanin did not play a major role in that adhesion. Melanin-less appressoria were consistently and uniformly plasmolyzed by low solute concentrations, whereas melanized appressoria, if formed on a solid surface, were plasmolyzed only by much higher solute concentrations. In addition, the cell wall of living or heat-killed melanized, but never unmelanized, appressoria collapsed during plasmolysis due to cytorrhysis. Melanin, having a differential permeability to water and solute, allowed sealed appressoria to establish and maintain a high internal solute concentration that created a high internal hydrostatic pressure. It is that pressure, we suggest, that empowers the pathogen to penetrate the surface of a plastic coverslip as well as the host.

Vegetative incompatibility in Endothia parasitica

Abstract: Endothia parasitica , which causes a canker disease of chestnut trees, has a system of vegetative incompatibility similar to that found in other ascomycetes Incompatible interaction of strains on agar media leads to a barrage and the formation of pycnidia with conidia Twenty-eight compatibility groups have been identified among mass mycelial isolates from natural cankers from Italy, France, and North America and single ascospore clones from North America Single random ascospore and tetrad clones were tested for compatibility and the results provide new evidence that this fungus is homothallic with the ability to outcross Hypovirulent strains do not behave in a predictable manner in vitro with regard to vegetative incompatibility There is evidence for anastomoses in the host between hypovirulent and virulent strains in different compatibility groups

Neurospora from natural populations: Toward the population biology of a haploid eukaryote

Abstract: Natural populations of the ascomycete Neurospora have been sampled systematically throughout much of the world, and the haploid strains from colonies in nature have been characterized genetically in the laboratory Our findings are described in the context of a broader review of wild-collected strains, their uses, and their significance for population genetics Visible Neurospora colonies found on recently burned vegetation are usually unique in genotype More than three-fourths are pure strains originating from a single ascospore; the remainder can be purified Thus, despite the potential for clonal propagation, these colonies provide effective population samples comparable to those collected for higher plants and animals Over 3900 isolates from burned substrates have been analyzed from over 500 collection sites, mostly from tropical and subtropical regions These strains have been assigned to five species—four heterothallic species with eight-spored asci and one pseudohomothallic species with four-spored asci Each species has a unique pattern of distribution, but each overlaps with all the others in one or another part of its range All of these species are similar in vegetative morphology, with orange or yellow-orange conidia All have two homologous mating types, but the different species are reproductively isolated from one another Fertility in crosses with reference strains has provided a reliable and convenient criterion for species classification of heterothallic strains The species of a newly obtained haploid strain is determined by finding a tester strain with which it is fully fertile and produces predominantly viable ascospores Viable ascospores are extremely rare for most interspecific combinations, but genes can nevertheless be transferred by matings among all but one of the nonhomothallic species Abundant but mostly inviable ascopores are produced by some interspecific combinations Karyotypes, karyogamy, and meiotic chromosome behavior are similar for all the known Neurospora species There are seven chromosomes and a single terminal nucleolus organizer This pattern also applies to the five eight-spored homothallic Neurospora lines that were designated by their discoverers as different species on the basis of ascospore morphology These homothallic lines all lack orange pigment and are devoid of conidia They were obtained by enrichment from soil samples and would not have been obtained by our collecting methods, which rely on visibility in the field Examination of wild-collected strains of N crassa and N intermedia has revealed a wealth of intraspecific genetic variation Genetic polymorphism of isozymes in local populations is comparable to that in outbreeding higher animals and plants DNA restriction fragment length polymorphisms are also abundant, as are differences at vegetative (heterokaryon) incompatibility loci and recessive genes that adversely affect one or more stages of the sexual diplophase Chromosomally located factors, called Spore killer, act in the sexual phase to produced meiotic drive The four Spore-killer-sensitive ascospores in every ascus are killed in crosses of sensitive × killer, but all eight ascospores remain viable in crosses of killer × killer and sensitive × sensitive Mitochondrial genomes of wild strains differ in both length mutations and nucleotide substitutions Many isolates contain mitochondrial plasmids A few strains have been found to undergo senescence following insertion of a foreign element into mitochondrial DNA