''Albugo'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of plant-parasitic

oomycete The Oomycetes (), or Oomycota, form a distinct phylogenetic lineage of fungus-like eukaryotic microorganisms within the Stramenopiles. They are filamentous and heterotrophic, and can reproduce both sexually and asexually. Sexual reproduction o ...

s. Those are not true fungi (

Eumycota A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as one of the tradi ...

), although many discussions of this organism still treat it as a fungus. The

taxonomy image:Hierarchical clustering diagram.png, 280px, Generalized scheme of taxonomy Taxonomy is a practice and science concerned with classification or categorization. Typically, there are two parts to it: the development of an underlying scheme o ...

of this genus is incomplete, but several

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

are

plant pathogens Plant diseases are diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Organisms that cause infectious disease include fungi, oomycetes, bacteria, viruses, viroids, virus-like orga ...

. ''Albugo'' is one of three genera currently described in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Albuginaceae Albuginaceae is a family of oomycetes. Genera and species Albuginaceae contains the following subtaxa: *'' Albugo'' **'' Albugo achyranthis'' **'' Albugo aechmantherae'' **'' Albugo arenosa'' **'' Albugo austroafricana'' **''Albugo candida'' ...

, the taxonomy of many species is still in flux. This organism causes white

rust Rust is an iron oxide, a usually reddish-brown oxide formed by the reaction of iron and oxygen in the catalytic presence of water or air moisture. Rust consists of hydrous iron(III) oxides (Fe2O3·nH2O) and iron(III) oxide-hydroxide (FeO(OH) ...

or white blister diseases in above-ground plant tissues. While these organisms affect many types of plants, the destructive aspect of infection is limited to a few agricultural crops, including:

beet The beetroot (British English) or beet (North American English) is the taproot portion of a '' Beta vulgaris'' subsp. ''vulgaris'' plant in the Conditiva Group. The plant is a root vegetable also known as the table beet, garden beet, dinner ...

s (garden and sugar),

Brussels sprout The Brussels sprout is a member of the Gemmifera cultivar group of cabbages (''Brassica oleracea''), grown for its edible buds. Etymology Though native to the Mediterranean region with other cabbage species, Brussels sprouts first appeared i ...

cabbage Cabbage, comprising several cultivars of '' Brassica oleracea'', is a leafy green, red (purple), or white (pale green) biennial plant grown as an annual vegetable crop for its dense-leaved heads. It is descended from the wild cabbage ( ''B.& ...

Chinese cabbage Chinese cabbage (''Brassica rapa'', subspecies ''pekinensis'' and ''chinensis'') is either of two cultivar groups of leaf vegetables often used in Chinese cuisine: the Pekinensis Group (napa cabbage) and the Chinensis Group (bok choy). These v ...

cauliflower Cauliflower is one of several vegetables cultivated from the species '' Brassica oleracea'' in the genus '' Brassica'', which is in the Brassicaceae (or mustard) family. Cauliflower usually grows with one main stem that carries a large, rou ...

collards Collard is a group of loose-leafed cultivars of ''Brassica oleracea'' (the same species as many common vegetables like cabbage and broccoli). Part of the acephala cultivar group (or kale group), collard is also classified as the variety ''B.& ...

garden cress Cress (''Lepidium sativum''), sometimes referred to as garden cress (or curly cress) to distinguish it from similar plants also referred to as cress (from Old English ''cresse''), is a rather fast-growing, edible herb. Garden cress is genetica ...

kale Kale (), also called leaf cabbage, belongs to a group of cabbage (''Brassica oleracea'') cultivars primarily grown for their Leaf vegetable, edible leaves; it has also been used as an ornamental plant. Its multiple different cultivars vary quite ...

lettuce Lettuce (''Lactuca sativa'') is an annual plant of the family Asteraceae mostly grown as a leaf vegetable. The leaves are most often used raw in Green salad, green salads, although lettuce is also seen in other kinds of food, such as sandwiche ...

, mustards,

parsnip The parsnip (''Pastinaca sativa'') is a root vegetable closely related to carrot and parsley, all belonging to the flowering plant family Apiaceae. It is a biennial plant usually grown as an annual. Its long taproot has cream-colored skin an ...

radish The radish (''Raphanus sativus'') is a flowering plant in the mustard family, Brassicaceae. Its large taproot is commonly used as a root vegetable, although the entire plant is edible and its leaves are sometimes used as a leaf vegetable. Origina ...

horseradish Horseradish (''Armoracia rusticana'', syn. ''Cochlearia armoracia'') is a perennial plant of the family Brassicaceae (which also includes Mustard plant, mustard, wasabi, broccoli, cabbage, and radish). It is a root vegetable, cultivated and us ...

rapeseed Rapeseed (''Brassica napus'' subsp. ''napus''), also known as rape and oilseed rape and canola, is a bright-yellow flowering member of the family Brassicaceae (mustard or cabbage family), cultivated mainly for its oil-rich seed, which naturall ...

, salsify (black or white),

spinach Spinach (''Spinacia oleracea'') is a leafy green flowering plant native to Central Asia, Central and Western Asia. It is of the order Caryophyllales, family Amaranthaceae, subfamily Chenopodioideae. Its leaves are a common vegetable consumed eit ...

sweet potato The sweet potato or sweetpotato (''Ipomoea batatas'') is a dicotyledonous plant in the morning glory family, Convolvulaceae. Its sizeable, starchy, sweet-tasting tuberous roots are used as a root vegetable, which is a staple food in parts of ...

es,

turnip The turnip or white turnip ('' Brassica rapa'' subsp. ''rapa'') is a root vegetable commonly grown in temperate climates worldwide for its white, fleshy taproot. Small, tender varieties are grown for human consumption, while larger varieties a ...

watercress Watercress or yellowcress (''Nasturtium officinale'') is a species of aquatic flowering plant in the cabbage family, Brassicaceae. Watercress is a rapidly growing perennial plant native to Eurasia. It is one of the oldest known leaf vegetabl ...

, and perhaps water-spinach.

Summary

White rust plant diseases caused by ''Albugo'' fungal-like pathogens should not be confused with

white pine blister rust ''Cronartium ribicola'' is a species of rust (fungus), rust fungus in the family Cronartiaceae that causes the disease white pine blister rust. Other names include: (French), (German), (Spanish). Origin ''Cronartium ribicola'' is native to C ...

Chrysanthemum white rust Chrysanthemums ( ), sometimes called mums or chrysanths, are flowering plants in the Asteraceae family. They are native to East Asia and northeastern Europe. Most species originate from East Asia, and the center of diversity is in China. Coun ...

or any

fungal rust Rusts are fungal plant pathogens of the order Pucciniales (previously known as Uredinales) causing plant fungal diseases. An estimated 168 rust genera and approximately 7,000 species, more than half of which belong to the genus ''Puccinia'', are ...

s, all of which are also plant diseases but have completely different symptoms and causal pathogens. Symptoms of white rust caused by ''Albugo'' typically include yellow lesions on the upper leaf surface and white pustules on the underside of the leaf. The pathogen is spread by wind, water, and insects. Management includes use of resistant

cultivar A cultivar is a kind of Horticulture, cultivated plant that people have selected for desired phenotypic trait, traits and which retains those traits when Plant propagation, propagated. Methods used to propagate cultivars include division, root a ...

s, proper

irrigation Irrigation (also referred to as watering of plants) is the practice of applying controlled amounts of water to land to help grow crops, landscape plants, and lawns. Irrigation has been a key aspect of agriculture for over 5,000 years and has bee ...

practices,

crop rotation Crop rotation is the practice of growing a series of different types of crops in the same area across a sequence of growing seasons. This practice reduces the reliance of crops on one set of nutrients, pest and weed pressure, along with the pro ...

, sanitation, and chemical control. White rust is an important economic disease, causing severe crop losses if not controlled.

Hosts and symptoms

White rust pathogens create

chlorotic In botany, chlorosis is a condition in which leaves produce insufficient chlorophyll. As chlorophyll is responsible for the green color of leaves, chlorotic leaves are pale, yellow, or yellow-white. The affected plant has little or no ability to ...

(yellowed) lesions and sometimes galls on the upper leaf surface and there are corresponding white blister-like dispersal pustules of

sporangia A sporangium (from Late Latin, ; : sporangia) is an enclosure in which spores are formed. It can be composed of a unicellular organism, single cell or can be multicellular organism, multicellular. Virtually all plants, fungus, fungi, and many ot ...

on the underside of the leaf. Species of the Albuginaceae deform the branches and flower parts of many host species. Host species include most if not all plants in the family Brassicaceae, common agricultural weeds, and those specified below."White Rusts of Vegetables"
(PDF), RPD No. 960, Univ. of Illinois Extension, uiuc.edu, September 1990. White rust symptoms

Disease cycle

White rust is an

obligate parasite An obligate parasite or holoparasite is a parasitic organism that cannot complete its life-cycle without exploiting a suitable host. If an obligate parasite cannot obtain a host it will fail to reproduce. This is opposed to a facultative parasite, ...

. This means it needs a living host to grow and reproduce. The Albuginaceae reproduce by producing both sexual spores (called

oospore An oospore is a thick-walled sexual spore that develops from a fertilized oosphere in some algae, fungi, and oomycetes. They are believed to have evolved either through the fusion of two species or the chemically induced stimulation of mycelia ...

s) and asexual spores (called

) in a many-stage (polycyclic) disease cycle. The thick-walled oospores are the main overwintering structures, but the

mycelium Mycelium (: mycelia) is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Its normal form is that of branched, slender, entangled, anastomosing, hyaline threads. Fungal colonies composed of mycelium are fo ...

can also survive in conditions where all the plant material is not destroyed during the winter. In the spring the oospores germinate and produce sporangia on short stalks called

sporangiophore {{Short pages monitor thumb , right , A photomicrograph of a sporangiophore