GLOSSARY

Acervulus (plural -i; from Latin acervus = heap). A layer of closely packed hyphae giving rise to short conidiophores bearing conidia.

Aeciospores (from Greek aikia = injury + sporos = seed). Binucleate spores formed from a dikaryotic mycelium following fusion of pycniospores with receptive hyphae during the life cycles of rust fungi (Uredinales).

Amino acids. Water soluble, organic nitrogenous compounds which may join together to form short chains (peptides) or long chains (polypeptides). Proteins are made up of various proportions of approximately 20 different amino acids.

Amorphous (from Greek a = without + morphe = form). Lacking shape, form or organised internal structure.

Anamorph (from Greek anamorphosis = forming anew). The asexual (non-sexual, imperfect) reproductive state of a fungus.

Antheridium (plural -ia; from Greek antheros = flowery). The male gametangium (sexual structure) in members of the Oomycota.

Apothecium (plural -ia; from Greek apotheke = storehouse). A saucer- or cup-shaped ascocarp (sexual fruiting body of the Ascomycota) bearing asci on the open surface.

Appressorium (plural -ia; from Latin apprimere = to press against). A swollen or flattened structure, formed at the end of the germ tube of a fungal pathogen and attached to the surface of the host immediately before penetration.

Arbuscule (from Latin arbor = tree). A finely branched haustorium of a vesicular-arbuscular (VA) mycorrhizal fungus.

Ascocarp (from Greek askos = skin sack + karpos = fruit). A fruiting body of a member of the Ascomycota.

Ascus (from Greek askos = skin sack). A sack-like structure in which the sexual spores of members of the Ascomycota are formed.

Ascospores (from Greek askos = skin sack + sporos = seed). Haploid, sexual spores of members of the Ascomycota.

Asexual (from Greek a = without + Latin sexus = sex). Non-sexual, as of a spore or phase of a life cycle (see also anamorph).

Aseptic (from Greek a = without + septikos = putrefy). Uncontaminated by microorganisms.

Autoecious (from Greek autos = self + oikos = home). Of a fungus (usually a rust – Uredinales) which completes its life cycle on a single host species.

Auxins. A group of plant growth regulators (hormones) which interact with other growth regulators to control such processes as cell division and enlargement, cell differentiation and apical dominance in higher plants.

Avirulent (from Greek a = without + Latin virulentus = poisonous). Used of a strain of a pathogen unable to cause disease on a resistant host.

Bacteriophage (from Greek bacterion = little stick + phagein = devour). A virus that infects prokaryotes, especially bacteria.

Bacterium (plural -ia; from Greek bacterion = little stick). Prokaryotic, usually unicellular microorganism.

Basidium (plural -ia; from Greek baseidion = small base). A cell in a member of the Basidiomycota in which nuclear fusion and meiosis occur, and on which the basidiospores (usually 4) are formed.

Basidiocarp (from Greek baseidion = small base + karpos = fruit). A fruiting body (such as a mushroom, toadstool or bracket) in the Basidiomycota in which basidia bearing basidiospores are formed.

Basidiospores (from Greek baseidion = small base + sporos = seed). Haploid spores of members of the Basidiomycota, formed on a basidium.

Callose. A structural polysaccharide made up of long chains (polymers) of glucan units, formed by plants and fungi, often in response to injury.

Cellulase. An enzyme involved in the breakdown of cellulose.

Cellulose. A structural polysaccharide made up of long chains (polymers) of glucan units; a major constituent of the cell walls of plants and members of the Oomycota.

Chemotaxis (from Greek taxis = arrangement). A response of an organism to a chemical stimulus; used to describe the swimming of zoospores or growth of hyphae towards chemicals such as sugars secreted by a plant.

Chitin (from Greek chiton = tunic). A polysaccharide containing nitrogen, with long, fibrous molecules; a major constituent of the hyphal walls of members of the Kingdom FUNGI and of the exoskeleton of insects.

Chlamydospore (from Greek chlamys = mantle + sporos = seed). A resting spore formed by thickening of the wall of a hyphal cell.

Chlorosis (from Greek chloros = green). Yellowing of green tissue, by breakdown of the green pigment chlorophyll.

Chromosozmes (from Greek chroma = colour + soma = body). Thread-like structures which occur in all living cells and carry genetic information in the form of deoxyribonucleic acid (DNA).

Cleistothecium (plural -ia; from Greek kleistos = closed + theke = case). An ascocarp in which the asci are completely enclosed by the outer wall.

Clamp connection. A specialised hyphal bridge involved in maintaining the dikaryotic condition during growth of hyphae of the Basidiomycetes.

Conidiophore (from Greek konis = dust + phorein = to bear). A specialised hypha, sometimes branched, which bears conidia.

Conidium (plural -ia; from Greek konis = dust). A non-motile, asexual spore formed at the tip of a specialised hypha.

Cultivar. A variety, produced by selection or breeding, of a cultivated plant.

Cuticle (from Latin cutis = skin). The largely ‘waterproof’ layer, mainly composed of the fatty, hydrophobic (water-repellent) polymer cutin, covering the above ground surfaces of a plant.

Cutin (from Latin cutis = skin). A fatty, hydrophobic (water-repellent) polymer that forms the major component of the plant cuticle.

Cutinase (from Latin cutis = skin). An enzyme involved in the breakdown of cutin.

Cytokinins (from Greek kutos = vessel + kinein = to move). Plant growth regulators (hormones) which, amongst other things, control cell division and differentiation in the presence of auxins, and retard senescence in higher plants.

Cytoplasm (from Greek kutos = vessel + plassein = to mould). The living contents of a plant cell, bounded by a membrane, the plasmalemma.

Digitate (from Latin digitatus = divided like fingers and toes). Divided like fingers or toes.

Dikaryon (from Greek dis = double + karyon = nut [nucleus]). A fungal cell containing two complementary haploid nuclei, usually of opposite mating type.

Diploid (from Greek diploos = double). Used of a cell or organism containing two complementary sets of chromosomes.

Dolipore-septum (plural -a; from Latin dolium = large jar + Greek poros = pore). A type of septum found in the hyphae of the Basidiomycota in which a central pore is extended into a barrel-shaped structure with open ends surrounded by membranes.

Dioecious (from Greek dis = double + oikos = home). Used of a species in which the male and female reproductive structures are formed on separate individuals.

Echinulate (from Greek echinos = hedgehog). Spiny.

Ectomycorrhiza (from Greek ektos = outside + mykes = mushroom + rhiza = root). A mutualistic symbiosis involving a fungus and the roots of a plant in which the fungus is restricted to a sheath around the outside of the root and the spaces between the surface cells.

Endomycorrhiza (from Greek endon = inside + mykes = mushroom + rhiza = root). A mutualistic symbiosis involving a fungus and the roots of a plant in which the fungus grows within the tissues of the root and may penetrate the cells.

Endophyte (from Greek endon = inside + phyton = plant). A fungus that grows within the tissues of a plant host without causing any noticeable symptoms of disease.

Enzyme. A protein that functions as a catalyst in biochemical reactions.

Epidermis (from Greek epi = upon + derma = skin). The outermost layer of cells of a plant.

Epinasty. (Of a leaf); to grow (bend) downwards from the base in response to altered levels of plant growth regulators (hormones).

Eukaryote (from Greek eu = well + karyon = nut). An organism in which the genetic material (DNA) of the cells is contained within a nucleus bounded by a membrane.

Facultative. Used of a parasite that may also grow as a saprophyte.

Flagella (sing. -um; from Latin flagellum = whip). Long, thin, whip-like structures that serve to propel motile cells such as zoospores.

Forma specialis (plural -ae; -es; abbreviated to f.sp.). A physiological form of a fungal species with a specific host range different from the host ranges of other formae speciales of the same species.

Fungistasis (from Latin fungus = mushroom + Greek stasis = standing). Prevention of germination of a fungal spore or of hyphal growth, usually by chemicals secreted by other microorganisms; if the inhibitor is removed, growth is resumed.

Fungitoxin. A chemical toxic to fungi.

Fungus (plural -i; from Latin fungus = mushroom). Used in the book to describe eukaryotic microorganisms that lack chlorophyll, usually grow as filaments (hyphae) and reproduce by means of asexual or sexual spores. See also the Kingdom FUNGI (Chapter 1).

Gametangium (plural -ia; from Greek gametes = husband). A structure which contains gametes or which functions as a gamete.

Gamete (from Greek gamete = wife, gametes = husband, gamein = to marry). A haploid cell that fuses with another complementary haploid cell during sexual reproduction to produce a diploid zygote.

Genome. All the genes contained in a single set of chromosomes of an organism.

Genotype. The genetic make-up of an organism.

Gibberellins. A group of plant growth regulators (hormones) involved in, for example, the regulation of cell expansion, stem elongation and seed germination in higher plants. Gibberellins were originally studied as products of the fungus Gibberella fujikuroi, hence the name.

Glucan. A short polymer made up of glucose molecules.

Glycoprotein. A carbohydrate linked to a protein.

Haploid (from Greek haploos = single). Used of a cell or organism containing a single set of chromosomes.

Haulm. The stems of a potato plant.

Haustorium (plural -ia; from Latin haurire = to drink dry). A specialised hyphal branch of a biotroph or hemibiotroph that penetrates the host cell wall and enters into an intimate association with the living cytoplasm of the cell. Also, a multicellular structure produced by higher plant (angiosperm) parasites that establishes an interface with the tissues of the host.

Hemibiotroph (from Greek hemi = half + bios = life + trophein = to feed). A plant pathogen exhibiting features of both biotrophy and necrotrophy, in sequence.

Hemicellulase. An enzyme involved in the breakdown of hemicelluloses.

Hemicelluloses. Complex polymers (chains) of various sugars, mainly linear but sometimes branched; major constituents of plant cell walls.

Heteroecious (from Greek heteros = other + oikos = home). Used to describe a fungus, usually a rust, that must infect two host species in order to complete its life cycle.

Heterokaryon (from Greek heteros = other + karyon = nut). A fungal mycelium containing a mixture of genetically different nuclei.

Heterothallic (from Greek heteros = other + thallos = shoot). Used of a fungus in which sexual reproduction can only occur between mycelia and nuclei that carry different, complementary genes controlling mating type.

Heterozygous (from Greek heteros = other + zygon = yoke). Having different genetic information at a particular point (locus) on the complementary chromosomes of a diploid cell.

Homothallic (from Greek homo = same + thallos = shoot). Used of a fungus which is self-fertile, without distinct mating types.

Hydrolysis. Reaction of a chemical compound with water.

Hymenium (from Hymen, Greek and Roman god of marriage). The fertile layer in an ascocarp or basidiocarp where the asci or basidia are produced.

Hypersensitive (from Greek hyper = over). Increased sensitivity of a cell to infection by a parasite, leading to rapid death.

Hyphae (sing. -a; from Greek hyphe = web). The tube-like filaments that are the basic body form of most fungi.

Hypovirulence (from Greek hupo = under + Latin virulentus = poisonous). Lower than normal virulence resulting in reduced pathogenicity.

Infection peg. An infection structure produced by the appressorium of a fungus to penetrate the host cell wall.

Imperfect. See Anamorph.

Latent. Used of a pathogen that lives within a host without causing visible symptoms of disease but may do so when conditions cnoindente.

Lesion (from Latin laesio = injury). Site of damage or injury caused by a pathogen.

Lignin (from Latin lignum = wood). A tough, three dimensional, amorphous polymer of various aromatic molecules deposited in the walls of the water-conducting and strengthening cells of plants. Wood is composed of mainly lignified cells.

Lignituber (from Latin lignum = wood + tuber = bump or tumour). A proliferation of a host cell wall that ensheaths a penetrating hypha of a fungal pathogen, thus restricting its growth.

Lipids. Fatty substances.

Macroconidium (plural -ia; from Greek makros = long + konis = dust). A large, as distinct from a small (micro), conidium.

Meiosis (from Greek meiosis = reduction). Two nuclear divisions, one after the other, resulting in the reduction of the chromosome complement of the nucleus from diploid to haploid. In meiosis one diploid nucleus gives rise to four haploid nuclei, each in a new daughter cell.

Microconidia (from Greek mikros = small + konis = dust). See Macroconidia.

Microorganism (from Greek mikros = small). An organism that is so small as to be invisible or virtually invisible to the naked eye.

Middle lamella (from Latin lamella = a thin plate). The amorphous, glue-like layer joining adjacent plant cells, dominated by pectic substances.

Mitochondria (from Greek mitos = thread). Membrane-bound, sub-cellular bodies in which respiration occurs in living cells.

Mitosis (from Greek mitos = thread). Nuclear division followed by cell division in non-sexual cells of a living organism, resulting in two identical daughter nuclei, each containing the same number of chromosomes, identical to those of the mother nucleus.

Monokaryotic (from Greek monon = alone + karyon = nut). Containing only one nucleus; used of a spore or fungal cell.

Mushroom (possibly from old French mousseron = moss). An edible toadstool.

Mutualism (from Latin mutuus = mutual or reciprocal). An interaction between two species from which both benefit.

Mycelium (from Greek mykes = mushroom). A mass of hyphae of a fungus.

Mycorrhiza (from Greek mykes = mushroom + rhiza = root). A mutually beneficial association between a fungus and the roots of a plant.

Mycoplasmas (from Greek mykes = mushroom + plassein = to mould). A group of Prokaryotes, significantly smaller than bacteria, that lack a cell wall and are thought to be the smallest living cellular organisms. Mycoplasmas that infect plants are often called phytoplasmas.

Mycostasis. Prevention of germination of a fungal spore or hyphal growth, usually by chemicals secreted by other microorganisms; if the inhibitor is removed, growth is resumed.

Necrosis (from Greek nekrosis = death). Cell or tissue death.

Necrotroph (from Greek nekros = corpse + trophe = food). A pathogen that derives its nutrients from the dead cells of its host.

Nucleic acid. A complex organic substance in living cells that consists of a chain of nucleotides. There are two types: deoxyribonucleic acid (DNA), which is the genetic material of most living organisms; and ribonucleic acid (RNA), which is involved in protein synthesis and may also contain genetic information.

Nucleus (from Latin nucleus = kernel). A membrane-bound body within a living cell that contains the chromosomes.

Obligate. Used of a parasite unable to grow saprophytically.

Oogonium (plural -ia; from Greek oon = egg + gonos = child or product). The female gametangium in members of the Oomycota.

Oospores (from Greek oon = egg + sporos = seed). The thick-walled, sexual resting spores of members of the Oomycota which develop in the oogonia following fertilisation.

Paraphyses (sing. -is; from Greek paraphysis = monstrous growth). Sterile, elongate cells or hairs within a hymenium.

Parasexual (from Greek para = beside). A process in which nuclear fusion and genetic recombination occur within the vegetative hyphae of a fungus, quite separate from the sexual cycle.

Parasite (from Greek parasitos = one who dines at another’s table). An organism that invades another (the host) and derives nutrients from it, often causing disease or debilitation.

Pathogen (from Greek pathos = suffering). A parasite that causes disease in its host.

Pathogenesis-related protein (PR-protein). An antifungal protein, usually an enzyme, produced by a host in response to invasion by a fungus.

Pathogenicity. The capacity to cause disease.

Pathology (from Greek pathos = suffering + logos = word/account/reason). The study of disease (hence ‘Plant Pathology’).

Pathotoxin (from Greek pathos = suffering). A toxin produced by a pathogen and involved in causing disease.

Pathovar (abbreviated to pv.). A form of a plant pathogen (usually a bacterium) having a different host from other morphologically identical pathovars of the same pathogen.

Pectate (from Greek pektos = congealed). An insoluble gel formed when a pectic acid combines chemically with calcium ions (Ca⁺⁺); found in the plant cell wall and middle lamella.

Pectic acid (from Greek pektos = congealed). Soluble gel composed of long chains (polymers) of acidic sugar molecules; found in the plant cell wall and middle lamella.

Pectin (from Greek pektos = congealed). A gel formed by the chemical reaction of a pectic acid with methanol; found in the plant cell wall and middle lamella.

Pectinase. An enzyme involved in the breakdown of pectic substances.

Perfect. See Teleomorph.

Perithecium (plural -ia; from Greek peri = around + theke = case). An enclosed ascocarp with a neck and pore at the top, through which the ascospores are released.

Phage. See Bacteriophage.

Phenols. Complex organic compounds containing a hydroxyl group (-OH) attached to a carbon atom in a benzene ring. Many phenolic substances are toxic to fungi and may play a role in resistance to disease.

Phloem. The tissue in which sugars are transported in a plant.

Phylloplane (from Greek phyllon = leaf + Latin planus = flat). The surface of a leaf.

Phytoalexin (from Greek phyton = plant + alexein = to ward off). A toxic chemical, produced metabolically as a response to infection by a potential pathogen and involved in resistance to that and other pathogens.

Phytotoxin (from Greek phyton = plant + toxicon = poison). A poisonous chemical, toxic to plants.

Plasmadesmata (sing. -a; from Greek plasma = moulded). Threads of cytoplasm which pass through pores in plant cell walls and connect the living contents of one cell with those of another.

Plasmalemma (from Greek plasma = moulded). The membrane enclosing the (living) cytoplasm of a plant cell.

Plasmid. A small circular piece of parasitic DNA containing genetic information, but separate from the chromosome(s) of the cell.

Plasmodium (from Greek plasma = moulded). A fungal body lacking a cell wall.

Polymer (from Greek polloi = many). A chemical molecule made up of many repeated smaller molecules.

Polyol (Polyhydric alcohol). A fungal ‘sugar’.

Polysaccharide. A polymer composed of repeated sugar molecules.

Prokaryota (from Greek pro = before + karyon = nut). A superkingdom of organisms in which the genetic material consists of a single strand of DNA not separated from the rest of the cell by a nuclear membrane.

Propagule (from Latin propagare = to spread). A part of an organism such as a spore, cell or hyphal fragment involved in dispersal and reproduction.

Protocorm. A minute cellular structure, without chlorophyll, which is the first stage in the development of an orchid from a seed.

Pseudoplasmodium (plural -ia; from Greek pseudos = falsehood + plasma = moulded). An aggregation of uninucleate fungal bodies lacking cell walls.

Punctate. Marked or studded with points or dots.

Pycnia (sing. -ium; from Greek pyknos = close-packed). Structures formed by rust fungi (Uredinales) that give rise to pycniospores and receptive hyphae.

Pycnidia (sing. -ium; from Greek pyknos = close-packed). Minute, hollow, asexual fruiting bodies, lined with conidiophores bearing conidia.

Pycniospore (from Greek pyknos = close-packed + sporos = seed). Also called a spermatium. A haploid (monokaryotic) spore of a rust fungus (Uredinales) produced in a pycnium.

Receptive hyphae (also called flexuous hyphae). Haploid, monokaryotic hyphae produced by pycnia, which fuse with pycniospores from other pycnia to restore the dikaryotic phase in the rust life cycle.

Recombination. The reassortment of genes that occurs during meiosis.

Resting spore (from Greek sporos = seed). A dormant spore capable of surviving adverse environmental conditions such as drought or lack of a host.

Reticulate (from Latin reticulum = a net). Net-like.

Rhizoid (from Greek rhiza = root). A small root-like structure.

Rhizomorph (from Greek rhiza = root + morphe = form). A mass of hyphae bound together to form an elongate, root-like structure capable of transporting water and nutrients and able to grow at the tip.

Ribosome. A small, roughly spherical body, within a cell, which is the site of protein synthesis.

Rugose (from Latin rugosus = wrinkle). Corrugated or wrinkled.

Saprophyte (from Greek sapros = rotten). An organism that obtains its nutrients by breaking down the dead tissues of other organisms.

Sclerotium (plural -ia; from Greek skleron = hard). A mass of hyphae aggregated together to form a hard structure capable of remaining dormant for long periods before germinating to form a fungal growth.

Senescent (from Latin senescere = to grow old). Old and dying.

Septa (sing. -um; from Latin saepes = fence). Cross walls dividing hyphae into compartments.

Shikimic acid pathway. A complex biochemical pathway in plants leading to the synthesis of phenols and phenolic polymers, including lignin.

Slime mould. A multinuclear saprophytic fungus lacking a cell wall.

Spermatia (sing. -ium; from Greek sperma = seed). See pycniospore.

Spinose (from Latin spinosus = thorny). With long spines.

Spiroplasmas. Helically coiled mycoplasmas.

Sporangium (plural -ia; from Greek sporos = seed + aggeion = vessel). A walled, sack-like structure, the contents of which divide to form spores.

Sporangiophore (from Greek sporos = seed + aggeion = vessel + phorein = to bear). A hypha on which a sporangium or sporangia are formed.

Spore (from Greek sporos = seed). A minute propagule of a fungus or bacterium, functioning as a seed but without a pre-formed embryo.

Sporulate. To produce spores.

Sterigma (plural -ata; from Greek sterigma = support). A small, specialised branch that supports a sporangium or spore.

Stipe (from Latin stipes = stem). The stalk of a basidiocarp such as a toadstool.

Stoma (plural -ata). A pore, which can be opened or closed, in the epidermis (surface layer) of a leaf, through which water vapour, carbon dioxide, oxygen and other gases may pass.

Striate (from Latin stria = linear marking). Furrowed or streaked.

Stroma (plural -ata; from Greek stroma = bed). A mass of hyphae on or in which spores or fruit bodies are formed.

Suberin (from Latin suber = cork). A complex, fatty, hydrophobic polymer which is the major constituent of cork.

Symbiotic (from Greek syn = together with + bios = life). Two organisms living together either in a mutualistic or parasitic relationship.

Teleomorph (from Greek telos = end + morph = form). The sexual (perfect) state of a fungus.

Teliospore (from Greek telos = end + sporos = seed). A thick-walled, diploid resting spore of a rust fungus (Uredinales) formed following fusion of haploid nuclei of a dikaryon. (Synonymous with Teleutospore).

Toadstool. A non-edible (sometimes poisonous), mushroom-shaped fruiting body (basidiocarp) of a member of the Basidiomycetes.

Tomentose (from Latin tomentum = interwoven hair covering). Covered with matted hairs.

Urediospore (from Greek urere = to burn + sporos = seed). A dikaryotic (binucleate) non-sexual dispersal spore produced by a rust fungus (Uredinales). (Synonymous with Uredospore).

Ustilospore. A spore of a smut fungus (Ustilaginales) from which the basidiospores are formed.

Vacuole (from Latin vacuus = empty). Large membrane-bound, fluid-filled space within the cytoplasm of a cell.

Vegetative (from late Latin vegetabilis = animating). The growing, non-sporing hyphae and mycelium of a fungus.

Verrucose (from Latin verruca = wart). Warty.

Vesicle. Small membrane-bound, fluid-filled space within the cytoplasm of a cell; or a swollen hypha of a vesicular-arbuscular mycorrhizal fungus.

Vesicular-arbuscular (VA) mycorrhiza. A form of endomycorrhiza in which the fungus forms specialised feeding branches called arbuscules and swollen storage hyphae called vesicles.

Viroid. A simple form of a virus which lacks a protein coat.

Virulent (from Latin virulentus = poisonous). Used to describe a strain of a pathogen capable of causing disease on a host.

Virus (from Latin virus = poison). A microorganism capable of replication, but only in association with another, more complex organism, and having no cellular structure, consisting only of nucleic acid (RNA or DNA) with a protein coat.

Xerophyte (from Greek xeros = dry + phyton = plant). An organism adapted to live and reproduce in dry conditions.

Xylem. Lignified, water-conducting and supporting tissue in plants, forming the major component of wood.

Zoosporangium (plural -ia; from Greek zoion = animal + sporos = seed). A sporangium in which zoospores are formed.

Zoospore (from Greek zoion = animal + sporos = seed). A motile, asexual spore which swims by means of a flagellum or flagella.

Zygospore (from Greek zygon = yoke + sporos = seed). A diploid, thick-walled sexual resting spore formed by the fusion of two gametangia.

Zygote (from Greek zygon = yoke). The result of the fusion of two gametes, and containing a diploid nucleus formed by the fusion of two haploid nuclei, one from each gamete.