Glossary

A

amphigynous : pertaining to the sexual stage in which the antheridium completely surrounds the stalk of the oogonium (cf. paragynous)

antheridium : the male gametangium; a multinucleate, swollen hyphal tip affixed firmly to the wall of the female gametangium (the oogonium)

aplerotic : pertaining to a mature oospore that does not fill the oogonium; i.e. there is room left between the oospore wall and oogonium wall (cf. plerotic)

B

basal plug : a plug protruding into a sporangium from the basal cross wall, separating it from the sporangiophore

C

caducous : pertaining to sporangia that become dislodged readily (i.e. deciduous) and separate from the sporangiophore (cf. persistent)

catenulate :

having a chain-like form

chlamydospore : an asexual spore with a thickened inner wallthat is delimited from the mycelium by a septum; may be terminal or intercalary, and survives for long periods in soil

clade : a taxonomic group of organisms classified together on the basis of homologous features traced to a common ancestor

clonal lineage : a population that is genetically identical to the ancestor from which it was derived (e.g. asexual reproduction)

close sympodium : a simple sympodium in which the sporangiophores are very short; a clustered sympodium that has short sporangiophores as well as short nodes between them (cf. lax sympodium)

coenocytic : nonseptate; referring to the fact that nuclei are present in the cytoplasm of the hyphae without separation by septa

colony : assemblage of hyphae which usually develops form a single source and grows in a coordinated way

compatibility type : molecular mechanisms that regulate compatibility in sexual reproduction in heterothallic species (also referred to as mating type); typically denoted as A1 or A2

compound sympodium : a sympodium with a branched hyphal system from which the sporangiophores initiate; can be irregular or regular (cf. simple sympodium)

D

diclinous : the hypha bearing the antheridium originated from a different hypha than that of the oogonium (cf. monoclinous)

E

electrophoresis : a technique used in laboratories to separate and analyze macromolecules (e.g. DNA or RNA) and their fragments based on size and charge.

ellipsoid : refers to a solid body that forms an ellipse in the longitudinal plane and a circle in cross section; many fungal spores are ellipsoidal or elliptic

encyst : to form a cyst or protective covering

exit pore : the opening through which zoospores pass when leaving a sporangium; papillate and semipapillate sporangia have exit pores 5 to 7 μm wide; the exit pores of nonpapillate sporangia are about 12 μm wide

extended proliferation : a type of internal proliferation in which the sporangiophore originates from inside of an empty sporangium, and continues to grow through and out of the old sporangium

external proliferation : formation of a sporangium after a sporangiophore has emerged from beneath and external to an empty sporangium that has previously emitted its zoospores (cf. internal proliferation).

F

flagellum : whip-like appendage on the zoospore used in motility; zoospore has a long whiplash flagellum with a smooth surface and a shorter tinsel flagellum on which mastigonemes (hair-like structures) occur

fusiform : spindle-shaped; wide in the middle while narrowing or tapering at each end

G

gametangium : part of hypha specialized for fusion in sexual reproduction (see antheridium and oogonium)

globose : having a rounded form resembling that of a sphere

H

heterokont : pertaining to zoospore fungi with different types of flagella; e.g., in Phytophthora species, the zoospore has both a whiplash flagellum and a tinsel flagellum

heterothallic : pertaining to sexual reproduction in which conjugation is possible only through interaction of different thalli (i.e. different mating types) (cf. homothallic)

homothallic : pertaining to sexual reproduction that can take place within a single thallus (i.e. self-fertile, non-outcrossing) (cf. heterothallic).

hypha : single, tubular filament of a fungal or oomycete thallus; the basic structural unit of a fungus or oomycete

hyphal swelling : globular swelling that forms at a branch point or within the mycelium, by definition not separated from the coenocytic mycelium by a septum (cf. chlamydospore)

I

intercalary : positioned within a hypha (cf. terminal)

internal proliferation : internal proliferation occurs when the sporangiophore continues to grow through an empty sporangium

isozyme : variant forms of an enzyme that share the same catalytic function; used for studying genetic diversity and evolution

L

lax sympodium : a sympodium in which the sporangiophores are long and loosely arranged (cf. close sympodium)

M

mating type : molecular mechanisms that regulate compatibility in sexual reproduction in heterothallic species (also referred to as compatibility type); typically denoted as A1 or A2

monoclinous : the hypha bearing the antheridium originated from the same hypha as the oogonium (cf. diclinous)

mycelium : mass of hyphae constituting the body, or thallus, of fungi and oomycetes; in Phytophthora species, mycelia is coenocytic

N

nested proliferation : a type of internal proliferation where a new sporangium develops successively inside the old sporangium after it has emptied

noncaducous : pertaining to sporangia that are not dislodged or separated (e.g. persistent) from the sporangiophore (cf. caducous)

nonpapillate : pertaining to the production of a non-distinct, or inconspicuous, papilla at the distal end of the sporangium (cf. papillate and semipapillate)

O

obovoid : inversely egg-shaped; ovoid, but with the widest part at the apex

obpyriform : inversely pear-shaped, i.e. with the widest part at the point of attachment (cf. pyriform)

oogonium : the female gametangium in which the oospore forms after fertilization by the antheridium

oospore : zygote or thick-walled spore that forms within the oogonium after fertilization by the antheridium; may be long-lived

ovoid : egg-shaped, with the widest part at the base of the sporangium and the narrow part at the apex

P

papilla : a small rounded or conic protuberance, generally translucent, on the wall of sporangia that breaks open and serves as the exit-point of zoospores

papillate : pertaining to the production of a distinct papilla at the distal end of the sporangium (cf. nonpapillate and semipapillate)

paragynous : pertaining to the sexual stage in which the antheridium is attached to the side of the oogonium (cf. amphigynous)

pedicel : the hyphal base of a sporangium that remains attached after the sporangium separates, or is shed, from the sporangiophore; the pedicel may be short (< 5 µm), medium (5–20 µm), or long (> 20 µm)

pellucid body : translucent, nucleus-containing body, two or more of which can be seen inside and near the periphery of the mature oospore (pellucid body or spot)

persistent : pertaining to sporangia that remain attached to the sporangiophore and do not separate or detach easily (cf. caducous)

plerotic : pertaining to an oospore that fills the oogonium (cf. aplerotic)

proliferation : formation of a sporangium within an empty sporangium that has previously emitted zoospores (internal or nested) or after the sporangiophore has emerged from the empty sporangium (external)

pyriform : pear-shaped, with the narrowest part at the base (cf. obpyriform)

R

reniform : kidney-shaped

RFLP : restriction fragment length polymorphism; after DNA is purified and treated with certain enzymes that react at different specific regions on the DNA molecule, the lengths of the resulting fragments are categorized by use of electrophoresis; the relative differences in fragment lengths are characteristic of genetic groups

S

semipapillate : pertaining to the production of shallow having papilla that are not well developed, shallow and less nipple-like than fully papillate structures

simple sympodium : an unbranched sympodium with a single sporangium produced externally from the base of the previous sporangium

sporangiophore : the hyphal strand on which the sporangium is formed; may be branched or unbranched to form compound sympodia or simple sympodia

sporangium : sac within which zoospores form, especially when water is cooled to about 10°C below ambient temperature; in solid substrates, sporangia usually germinate by germ tubes

sympodially : at the foot of; referring to a sporangiophore that emerges externally from the base of the previous sporangium

sympodium : a type of sporangiophore which appears simple, but where each successive sporangium develops on a branch behind and to one side of the previous apex, where growth has already ceased

T

tapered base : pertaining to the base of a sporangium or oogonium; funnel-shaped

toruloid :

having swellings at intervals

Z

zoospore : motile spore that forms within the sporangium and exits through the exit pore and is capable of swimming for several hours; it has both a tinsel flagellum and a whip-like flagellum