Glossary of phytopathology

This is a glossary of some of the terms used in phytopathology.

Phytopathology is the study of plant diseases. It is a multi-disciplinary science since prerequisites for disease development are the presence of a susceptible host species, a pathogen and the appropriate environmental conditions. This is known as the disease triangle. Because of this interaction, the terminology used in phytopathology often comes from other disciplines including those dealing with the host species ( botany / plant science, plant physiology), the pathogen (bacteriology, mycology, nematology, virology), the environment and disease management practices (agronomy, soil science, meteorology, environmental science, ecology, plant breeding, pesticides, entomology), and areas of study that apply to both the host and pathogen (molecular biology, genetics, molecular genetics). The result is that most phytopathological glossary include terms from these other disciplines in addition to terms (disease incidence, horizontal resistance, gene-for-gene relationship, blast, scab and so on) that are specific to, or which have a unique meaning in phytopathology. This glossary is no exception. However, for the sake of brevity, it has, for the most part, restricted terms from other disciplines to those that pertain to the pathogen. At some point, these terms should be moved to other glossaries (e.g. glossary of mycology, glossary of nematology, and so on).

A
 abiotic 
 * Disease not caused by living organisms

 acceptable daily intake 

 acervulus (pl. acervuli) 
 * The acervulus is an erumpent, cushionlike fruiting body bearing conidiophores, conidia, and sometimes setae. It is distinguished from a stroma in not having a peridium or covering of fungal tissue of any kind.

 acid precipitation 

 acid rain 

 acropetal 

 Actinomycetes 
 * The Actinobacteria or Actinomycetes are a group of Gram-positive bacteria.

 acute 

 acute toxicity 

 aeciospore 

 aecium 

 aflatoxin 

 agar 

 aggressiveness 

 air pollution 

 alkaloids 

 allele 

 allelopathy 

 alternate host 

 alternative hosts 

 alternation of generations 

 amphid 

 amphigynous 

 amphimixis 

 amphimobile 

 anaerobic 

 anamorph (adj. anamorphic; syn. imperfect state) 

 anastomosis (pl. anastomoses) 

 anthracnoes 

 antibiotic 

 antibody 

 antigen 

 antiseptic 

 apothecium 
 * The apothecium is an open, cuplike, or saucer-shaped sexual fungal fruiting body (ascocarp) containing asci.

 antiseptic 

 appressorium (pl. appressoria) 

 arbuscular mycorrhiza (abbr. AM; syn. endomycorrhiza) 

 arbuscule 

 ascocarp (syn. ascoma) 

 ascogenous 

 ascogonium (pl. ascogonia) 

 ascoma (pl. ascomata; syn. ascocarp) 

 Ascomycetes 

 asci 

 ascospore 

 ascostroma (pl. ascostromata) 

 ascus (pl. asci) 

 aseptate 

 asexual 

 asexual reproduction 

 atrophy 

 AUDPC (abbr. for Area Under Disease Progress Curve) 

 autotroph 

 avirulence (avr) gene 

 avirulent (syn. nonpathogenic) 

 axenic 

 autoecious 

B
 bacilliform 

 bacterial streaming 

 bactericide 

 bacteriocin 

 bacteriophage 

 bacterium (pl. bacteria) 

 bactericide 

 basal knob (syn. stylet knob) 

 basidiocarp (syn. basidioma) 

 Basidiomyctes 
 * The Division Basidiomycota is a large taxon within the Kingdom Fungi that includes those species that produce spores in a club-shaped structure called a basidium.

 basidiospore 

 basidium (pl. basidia) 

 basidiospore 

 basidium (pl. basidia; adj. basidial) 

 binary fission 

 binucleate 

 bioassay 

 biocide 

 biocontrol (syn. biological control) 

 biotic 
 * A disease caused by a living organism

 biotroph (syn. obligate parasite) 

 biotype 

 bitunicate 

 blasting 

 blight 

 blotch 

 breaking 

 broadcast application 

 brooming 

 brown rot (of wood) 

 

 burn 

 bursa 

C
 canker 

 capsid (syn. coat protein) 

 carcinogen 

 carrier 

 casting 

 causal agent 

 certification 

 cfu (abbr. for colony forming unit) 

 chemotaxis (syn. chemotropism) 

 chemotherapy 

 chlamydospore 

 chlamydospore 
 * A chlamydospore is the thick-walled big resting spore of several kinds of fungi.

 chlorosis 

 chronic toxicity 

 chytridiomycetes 

 circulative-propagative transmission (syn. propagative transmission) 

 circulative transmission (syn. persistent transmission) 

 cirrus 

 cleistothecium 

 clamp connection 

 clavate (or claviform) 

 coalesce 

 coat protein (syn. capsid) 

 coccus (pl. cocci) 

 coelomycetes 

 colonization 

 colony 

 colony forming unit (abbr. cfu) 

 compartmentalization 

 conidiogenesis 

 conidiogenous 

 conidioma (pl. conidiomata) 

 conidiophore 

 conidium (pl. conidia) 

 conjugation 

 conk 

 constitutive 

contact fungicide (syn. protectant fungicide) 

 coremium (pl. coremia; syn. synnema) 

 cross-protection 

 crozier 

 cryptobiosis (hidden life) 

 curl 

 cyst 

 cytopathology 

D
 damping-off 

 days to harvest 

 decay 

 degree-day 

 demicyclic 

 deuteromycetes (syn. Fungi Imperfecti) 

 diagnostic 

 antigen 

 diploid 
 * Diploid (2x) cells have two copies (homologs) of each chromosome, usually one from the mother and one from the father.

 diapause 

 dieback (v. die back) 

 differential host (syn. differential cultivar) 

 differential medium 

 differentiation 

 dikaryon (adj. dikaryotic) 

 dilution plating 

 dilution streaking 

 dimorphic 

 direct penetration 

 Discomycetes 

 disease 

 disease cycle 

 disease incidence 

 disease progress curve 

 disease pyramid 

 disease severity 

 disease triangle 

 disinfect 

 disinfest 

 dispersal (syn. dissemination) 

 dissemination (syn. dispersal) 

 dolipore septum 

 dormancy (adj. dormant) 

 downy mildew 

 drift (of pesticides) 

 drought 

 durable resistance 

 dwarfing 

E
 echinulate 

 economic threshold 

 ectomycorrhiza (pl. ectomycorrhizae) 

 ectoparasite 

 ectotrophic 

 elicitor 

 enation 

 encapsidate 

 encyst 

 endemic 

 endogenous 

 endophytic 

 endoconidium (pl. endoconidia) 

 endomycorrhiza (pl. endomycorrhizae; syn. arbuscular mycorrhiza) 

 endoparasite 

 endospore 

 epidemic 

 epidemiology 

 epinasty 

 epiphytotic 
 * The epidemic condition of a disease, in a plant population. Compare with enphytotic

 eradicant 

 eradication 

 ergot 

 ergotism 

 erumpent 

 escape 

 etiolation 

 etiology 

 exclusion 

 exogenous 

 exudate 

F
''' f. sp. (abbr. for forma specialis) '''

 facultative parasite 

 facultative saprotroph 

 fasciation 

 fastidious 

 filamentous (syn. filiform) 

 flagellum 

 flagging 

 fleck 

 focus (pl. foci) 

 forest decline 

 forma specialis (abbr. f.sp.; pl. formae speciales) 

 fructification 

 fruiting body 

fumigant (v. fumigate) 

 Fungi Imperfecti (syn. Deuteromycetes 

 fungicide (adj. fungicidal) 
 * Chemical designed to kill fungi

 fungus (pl. fungi) 

 fungistat (adj. fungistatic) 
 * Inhibits growth of some fungi.

 fungistasis 

 fusiform 

G
 gall 

 gametangium (pl. gametangia) 

 gametophyte 

 gene-for-gene hypothesis 

 general resistance (syn. horizontal resistance, race non-specific resistance) 

 genotype 

 germ theory 

 giant cell 

 girdle 

 giant cells 

 gram-negative 
 * Gram-negative bacteria are those that do not retain crystal violet dye in the Gram staining protocol.

 gram-positive 
 * Gram-positive bacteria are classified as bacteria that retain a crystal violet dye during the Gram stain process.

 gram stain 

 growth regulator (syn. hormone) 

 gummosis (pl. gummoses) 

H
 haploid 

 hardiness 

 haustorium (pl. haustoria) 
 * The haustorium is the hyphal tip of a parasitic fungus

 hemiparasite 

 hermaphrodite (adj. hermaphroditic) 

 heteroecious 

 heterokaryon (adj. heterokaryotic) 

 heterothallic 

 heterotroph 

 holomorph 

 holoparasite 

 homokaryon (adj. homokaryotic) 

 homothallism (adj. homothallic) 

 horizontal resistance (syn. general resistance, race non-specific resistance) 

 host plant 

 host range 

 hyaline 

 hymenium 

 hyperparasite 

 hyperplasia 

 hypertrophy 

 hypersensitive 

 hypersensitive reaction and pathogenicity (hrp) gene 

 hypersensitive response (HR) 

 hypha 

 hyphal sheath (syn. mantle) 

 hyphomycetes 

 hyphopodium 

 hypoplasia 

 hypovirulence 
 * hypovirulence is reduced virulence of a pathogen. Hypovirulence in fungi can be caused by a virus within the fungus. The virus reduces virulence and sporulation. A hypovirus-fungus can be used in biological control.

I
 immune 

 immunity 

 imperfect fungi (syn. Fungi Imperfecti, deuteromycetes) 

 imperfect state (syn. anamorph)   in planta 

 in situ 

 in vitro 

 in vivo 

 incubation period 

 indicator plant 

 indirect penetration 

 induced 

 induced systemic resistance (ISR) 

 infection court 

 infection cushion 

 infection focus 

 infection peg (syn. penetration peg) 

 infection period 

 infectious 

 infective 

infest (n. infestation)  

 initial inoculum (syn. primary inoculum) 

 injury 

 inoculate (n. inoculation) 

 inoculum (pl. inocula) 

 inoculum density 

 integrated pest management (abbr. IPM) 

intumescence (syn. edema or oedema) 

 IPM (abbr. for integrated pest management) 

 isolate 

K
 klendusity  The disease-escaping ability of plants.

 Koch's postulates 

 knot 

L
 latent infection 

 latent period 

 leaf dip 

 leaf spot 

 leafroll 

 lesion 

 life cycle 

 lignification 

 local lesion 

 local necrosis 

 lodge 

M
 macerate 

 macroconidium (pl. macroconidia) 

 macrocyclic 

 macronutrient 

 mantle (syn. hyphal sheath) 

 mating types 

 mechanical injury 

 mechanical transmission 

 medium (pl. media) 

 melanin 

 microbial 

 microclimate 

 microconidium (pl. microconidia) 

 microcyclic 

 microflora 

 micronutrient 

 microorganism (syn. microbe) 

 microsclerotium 

 mildew 

MLO (syn. mycoplasmalike organism) 

 mold 

 mollicute 

 monocyclic 

 monoecious 

 monogenic 

 monogenic resistance (syn. single gene resistance) 

 monotrichous 

 monoxenic culture 

 mosaic 

 motile 

 mottle 

 movement protein 

 multigenic resistance (syn. polygenic resistance) 

 multiline 

 multinucleate 

 multiparticulate virus 

 multipartite virus 

 multiseptate 

 mummification 

 mummy 

 mushroom 

 mutagen 

 Mycelia sterilia 

 mycelium (pl. mycelia) 
 * Mycelium is the vegetative part of a fungus consisting of a mass of branching, threadlike hyphae that exists below the ground or within another substrate.

 mycology 

 mycoparasite 

 mycoplasmalike organism (syn. MLO) 

 mycorrhiza (pl. mycorrhizae; adj. mycorrhizal) 

 mycotoxin 

 mycovirus 

 Myxomycetes (syn. slime molds) 

N
 necrosis (adj. necrotic) 

 necrotroph 

 needle cast (of conifers) 

 nematicide 
 * A nematicide is a type of chemical pesticide used to kill parasitic nematodes.

 nematode 
 * Nematodes are unsegmented, bilaterally symmetric and triploblastic protostomes with a complete digestive system.

 nitrogen oxides 

 noninfectious disease 

 nonpathogenic (syn. avirulent) 

 nonpersistent transmission (syn. stylet-borne transmission) 

 nonseptate 

O
 obligate parasite (syn. biotroph) 

 occlusion 

 oedema (also edema; syn. intumescence) 

 oligogenic resistance 

 oogonium (pl. oogonia) 
 * An oogonium is a female gametogonium.

 oomycetes (adj. oomycetous) 

 oospore 

 ooze 

 ostiole (adj. ostiolate) 

 overwinter 

P
 pandemic 

 papilla 

 paragynous 

 parasexualism 

 parasite (adj. parasitic) 

 parasitism 

 parthenogenesis (adj. parthenogenetic) 

 partial resistance 

 pasteurization 

 pathogen (adj. pathogenic) 

 pathogenesis-related (PR) proteins 

 pathogenicity 

 pathology 

 pathotype 

 pathovar (abbr. pv.) 

 penetration 

 penetration peg (syn. infection peg) 

 perfect (see teleomorph) 

 perithecium (pl. perithecia) 

 peritrichate 

 persistent transmission (syn. circulative transmission) 

 pest 

 pesticide 

 phenological synchrony 

 phenotype 

 phloem necrosis 

 Phycomycete 

 phyllody 

 phylloplane-competent 

 physiogenic disease 

 phytoalexin 

 phytopathogenic 

 phytopathology (syn. plant pathology) 

 phytoplasma (syn. mycoplasmalike organism, MLO) 

 phytosanitary certificate 

 phytotoxic 

 plant pathology (syn. phytopathology) 

 plasmodiophoromycetes 

 plasmodium (pl. plasmodia) 

 polycyclic 

 polyetic 

 polygenic resistance (syn. multigenic resistance) 

 polymorphism 

 polyprotein 

 powdery mildew 

 predispose (n. predisposition) 

 primary inoculum (syn. initial inoculum) 

 proinhibitin 

 prokaryote 

 promycelium (pl. promycelia) 

 propagative transmission (syn. circulative propagative transmission) 

 propagule 

 protectant 

 protectant fungicide (syn. contact fungicide) 

 pseudothecium (pl. pseudothecia) 

 Puccinia pathway 

 pustule 

''' pv. (abbr. for pathovar) '''

 pycnidiospore 

 pycnium (pl. pycnia; syn. spermagonium) 

 

 

Q
 qualitative resistance 

 quantitative resistance 

 quarantine 

 quiescent 

 quiescent 

 dormant or inactive 

 quorum sensing 

R
 race 

 race non-specific resistance (syn. general resistance, horizontal resistance) 

 receptive hypha 

 reniform 

 resinosis 

resistant (n. resistance)  

 rhizomorph 

 rhizosphere 

 rhizosphere-competent 

 ringspot 

 rosette 

 rot 

 roundworm 

 rugose 

 russet 

 rust 

S
 sanitation 

 sap transmission 

saprobe (syn. saprotroph) 

 saprotroph 
 * A saprotroph (or saprobe) is an organism that obtains its nutrients from non-living organic matter, usually dead and decaying plant or animal matter, by absorbing soluble organic compounds.

 scab 

 scald 

 sclerenchyma (adj. sclerenchymatous) 

 sclerotium (pl. sclerotia) 
 * A sclerotium is a compact mass of hardened mycelium (as an ergot) stored with reserve food material that in some higher fungi becomes detached and remains dormant until a favorable opportunity for growth occurs.

 scorch 

 secondary infection 

 secondary inoculum 

 secondary metabolite 

 secondary organism 

 seed treatment 

 seedborne 

 selective medium 

 septate 

 serrate 

 sessile 

 seta (pl. setae) 

 

 sexual spore 

 sexually compatible 

 shot-hole 

 sign 

 single gene resistance (syn. monogenic resistance) 

 slime molds (syn. Myxomycetes) 

 smut 

 soft rot 

 soil drench 

 soilborne 

 soil pasteurization 

 soil sterilization 

 solarization 

 sooty mold 

 sorus (pl. sori) 

''' sp. (abbr. for species; pl. spp.) '''

 species 

 specific resistance (syn. vertical resistance) 

 spermagonium (pl. spermagonia; syn. pycnium for rust fungi) 

 spermatium (pl. spermatia; syn. pycniospore for rust fungi) 

 spicule 

 spiroplasma – helical, motile, cell wall-less bacterium; member of genus Spiroplasma in class Mollicutes 

 sporangiophore 

 sporangiospore 

 sporangium (pl. sporangia) 

 spore 

 sporidium (pl.sporidia) 

 sporocarp 

 spore-bearing fruiting body 

 sporodochium (pl.sporodochia) 

 sporogenous 

 sporophore 

 sporophyte 

 sporulate 

 spot 

 stabilizing selection 

 staghead 

 stem pitting 

 sterigma (pl. sterigmata) 

 sterilant 

 sterile fungus 

 sterilization (adj. sterilized) 

 stippling 

 strain 

 streak 

 striate (n. striations) 

 stroma (pl. stromata) 

 stunting 

 stylet knob (syn. basal knob) 

 stylet-borne transmission (syn. nonpersistent transmission) 

 subspecies 

 substrate 

 sunscald or sunburn 

 suppressive soil 

susceptible (n. susceptibility) 

 symptom 

 symptomless carrier 

 syncytium (pl. syncytia) 

 synergism (adj. synergistic) 

 synnema (pl. synnemata; syn. coremium) 

 systematics 

 systemic 

 systemic acquired resistance (SAR) 

 systemic fungicide 

T
 teleomorph (syn. perfect state) 

 teliospore (sometimes called teleutospore, teleutosporodesm) 
 * Teliospore (sometimes called teleutospore) is the thick-walled resting spore of some fungi (rusts and smuts), from which the basidium arises.

 telium (pl. telia) 

 temporary wilt 

 thallus 

 thermotherapy 

tolerance (adj. tolerant) 

 toxicity 

 toxin 

 transmit (n. transmission) 

 trap crop 

 transmit (n. transmission) 

 trenching 

tumor (syn. gall) 

 type 

U
 urediniospore (also urediospore, uredospore) 

 uredinium (also uredium; pl. uredinia) 

V
 vascular wilt disease 

 vector 

 vein banding 

 vein clearing 

 vermiform 

 vertical resistance (syn. specific resistance) 

 viable (n. viability) 

 virescence 

 virion 

 viroid 

 viroplasm 

 virulence 

 virulent 

 viruliferous 

 virus-laden, usually applied to insects or nematodes as vectors 

 virus 
 * A virus is a microscopic particle (ranging in size from 20 – 300 nm) that can infect the cells of a biological organism.

 viscin 

W
 walling-off 

 water-soaked 

white rot (of wood) 

 white rust 

 wild type 

 wilt 

 winterburn 

 witches' broom 

 wound 

X
XLB (xylem-limited fastidious bacteria) 

xylem-limited fastidious bacteria (XLB) 

Y
 yellowing 

 yellows 

Z
 zonate 

 zoosporangium 

 zoospore 
 * A zoospore is a motile asexual spore utilizing a flagellum for locomotion.

 Zygomycetes 

 zygospore 
 * A zygospore is a sexual part of a fungus, a chlamydospore that is created by the nuclear fusion of haploid hyphae of different mating types.