Fungal Structures, Reproduction, and Disease Management: Mycology Key Terms

**Hypha

The basic thread-like structural unit of a fungus.**

Mycelium

The overall vegetative body formed by a diffuse, branched mass of hyphae.**

Coenocytic Hyphae

Hyphae that are nonseptate (lacking cross walls), appearing as hollow, multinucleate tubes.**

Septate Hyphae

Hyphae containing cross walls or divisions.**

Haustorium

A specialized fungal structure that penetrates a host cell wall to absorb nutrients without immediately killing the cell.**

Appressorium

A swollen, flattened portion of a fungal filament that adheres to the host surface to anchor the fungus before penetration.**

Apical Elongation

The process where fungal growth is concentrated only at the tip of the hyphae.**

Clamp Connection

A bridge-like protrusion formed at the septum of Basidiomycete hyphae to maintain the dikaryotic (n+n) state during cell division.**

Mitosis

The cell division process used to produce asexual spores (clones) for rapid reproduction and dispersal.**

Meiosis

The nuclear division process essential for sexual reproduction, resulting in genetic diversity.**

Ascospore

The sexual spore of Ascomycetes, typically found in groups of eight inside an ascus.**

Perithecium

The flask-shaped sexual fruiting body (ascocarp) of Ascomycetes, with an opening (ostiole) for spore release.**

Teliospore

The sexual survival spore of rusts and smuts, which undergoes meiosis to produce basidiospores.**

Urediniospore

The dikaryotic, rust-colored spore of rust fungi; it is the repeating stage that drives polycyclic epidemics.**

Basidiospore

The haploid sexual spore produced externally on a basidium.**

Zygospore

The sexual survival spore of Zygomycetes, formed by the fusion of gametangia.**

Oomycetes

Fungus-like organisms (Kingdom Chromista) defined by diploid vegetative hyphae, cellulose cell walls, and motile zoospores.**

Zoospore

The motile, asexual spore of Oomycetes and Chytridiomycota that uses flagella for movement in water.**

Indirect Germination

The mode of Oomycete sporangium development, favored by cooler temperatures, that releases multiple motile zoospores.**

Plasmodiophoromycota

Phylum (Kingdom Protozoa) causing diseases like club root of cabbage (Plasmodiophora brassicae), characterized by forming a plasmodium inside host cells.**

Biotroph

An obligate parasite that requires a living host to survive and obtain nutrients (e.g., Rusts, Downy Mildews).**

Hypovirulence

The biological control phenomenon where the pathogen is weakened by a mycovirus, reducing its disease-causing ability.**

Thigmotropism

Directional growth guided by touch or contact with a physical cue (e.g., detecting stomata on a leaf surface).**

Chemotropism

Directional growth guided by a chemical stimulus (e.g., growing toward nutrient exudates from a host root).**

Autotropism

Directional growth guided by members of the same species (e.g., growing toward a compatible hypha for sexual fusion).**

Vertical Resistance

Specific resistance against certain pathogen races, typically conferred by a single gene, but often unstable (boom-and-bust cycle).**

Horizontal Resistance

General resistance conferred by many genes that provides partial resistance against all races of a pathogen species.**

Bordeaux Mixture

The first widely used fungicide, composed of Copper Sulfate (active agent) and Lime (to reduce phytotoxicity).**