''Albugo'' is a
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
of plant-parasitic
oomycete
Oomycota forms a distinct phylogenetic lineage of fungus-like eukaryotic microorganisms, called oomycetes (). They are filamentous and heterotrophic, and can reproduce both sexually and asexually. Sexual reproduction of an oospore is the resul ...
s. Those are not true fungi (
Eumycota
A fungus (plural, : fungi or funguses) is any member of the group of Eukaryote, eukaryotic organisms that includes microorganisms such as yeasts and Mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified ...
), although many discussions of this organism still treat it as a fungus. The
taxonomy
Taxonomy is the practice and science of categorization or classification.
A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...
of this genus is incomplete, but several
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
are
plant pathogens
Plant pathology (also phytopathology) is the scientific study of diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Organisms that cause infectious disease include fungi, oomyc ...
. ''Albugo'' is one of three genera currently described in the
family
Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...
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 is the taproot portion of a beet plant, usually known in North America as beets while the vegetable is referred to as beetroot in British English, and also known as the table beet, garden beet, red beet, dinner beet or golden beet ...
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. The leaf vegetables are typically 1.5–4.0 cm (0.6–1.6 in) in diameter and resemble miniature cabbages ...
s,
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.&nb ...
s,
Chinese cabbage
Chinese cabbage (''Brassica rapa'', subspecies ''pekinensis'' and ''chinensis'') can refer to two cultivar groups of leaf vegetables often used in Chinese cuisine: the Pekinensis Group (napa cabbage) and the Chinensis Group (bok choy).
These ...
,
cauliflower,
collards
Collard is a group of certain loose-leafed cultivars of '' Brassica oleracea'', the same species as many common vegetables including cabbage ( Capitata group) and broccoli ( Italica group). Collard is a member of the Viridis group of ''Brassic ...
,
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 Germanic ''cresso'' which means sharp, spicy), is a rather fast-growing, edible herb. ...
,
kale,
lettuce
Lettuce (''Lactuca sativa'') is an annual plant of the family Asteraceae. It is most often grown as a leaf vegetable, but sometimes for its stem and seeds. Lettuce is most often used for salads, although it is also seen in other kinds of food, ...
,
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 raphanistrum'' subsp. ''sativus'') is an edible root vegetable of the family Brassicaceae that was domesticated in Asia prior to Roman times.
Radishes are grown and consumed throughout the world, being mostly eaten raw ...
,
horseradish
Horseradish (''Armoracia rusticana'', syn. ''Cochlearia armoracia'') is a perennial plant of the family Brassicaceae (which also includes mustard, wasabi, broccoli, cabbage, and radish). It is a root vegetable, cultivated and used worldwide ...
,
rapeseed
Rapeseed (''Brassica napus ''subsp.'' napus''), also known as rape, or oilseed rape, is a bright-yellow flowering member of the family Brassicaceae (mustard or cabbage family), cultivated mainly for its oil-rich seed, which naturally contains a ...
,
salsify (black or white),
spinach
Spinach (''Spinacia oleracea'') is a leafy green flowering plant native to central and western Asia. It is of the order Caryophyllales, family Amaranthaceae, subfamily Chenopodioideae. Its leaves are a common edible vegetable consumed either f ...
,
sweet potatoes,
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. The word ''turnip'' is a compound of ''turn'' as in turned/rounded on a lathe and ...
s,
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 Europe and Asia. It is one of the oldest known leaf v ...
, 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 in the family Cronartiaceae that causes the disease white pine blister rust. Other names include: (French), (German), (Spanish).
''Cronartium ribicola'' is native to China, and was subseque ...
, Chrysanthemum white rust or any fungal rusts, 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 type of cultivated plant that people have selected for desired traits and when propagated retain those traits. Methods used to propagate cultivars include: division, root and stem cuttings, offsets, grafting, tissue culture, ...
s, proper irrigation
Irrigation (also referred to as watering) is the practice of applying controlled amounts of water to land to help grow Crop, crops, Landscape plant, landscape plants, and Lawn, lawns. Irrigation has been a key aspect of agriculture for over 5,00 ...
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. It reduces reliance on one set of nutrients, pest and weed pressure, and the probability of developing resistant ...
, 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, ) is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. Virtually all plants, fungi, and many other lineages form sporangia at some point in their life cyc ...
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"](_blank)
(PDF), RPD No. 960, Univ. of Illinois Extension, uiuc.edu, September 1990.
Disease cycle
White rust is an obligate 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 sporangia
A sporangium (; from Late Latin, ) is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. Virtually all plants, fungi, and many other lineages form sporangia at some point in their life cyc ...
) in a many-stage (polycyclic) disease cycle.
The thick-walled oospores are the main overwintering structures, but the mycelium
Mycelium (plural mycelia) is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Fungal colonies composed of mycelium are found in and on soil and many other substrates. A typical single spore germinates ...
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 sporangiophores that become so tightly packed within the leaf that they rupture the epidermis and are consequently spread by the wind. The liberated sporangia in turn can either germinate directly with a germ tube
A germ tube is an outgrowth produced by spores of spore-releasing fungi during germination.
The germ tube differentiates, grows, and develops by mitosis to create somatic hyphae.C.J. Alexopolous, Charles W. Mims, M. Blackwell, ''Introductory My ...
or begin to produce biflagellate
A flagellate is a cell or organism with one or more whip-like appendages called flagellum, flagella. The word ''flagellate'' also describes a particular construction (or level of organization) characteristic of many prokaryotes and eukaryotes ...
motile zoospore
A zoospore is a motile asexual spore that uses a flagellum for locomotion. Also called a swarm spore, these spores are created by some protists, bacteria, and fungi to propagate themselves.
Diversity Flagella types
Zoospores may possess one or ...
s. These zoospores then swim in a film of water to a suitable site and each one produces a germ tube - like that of the sporangium - that penetrates the stoma. When the oomycete has successfully invaded the host plant, it grows and continues to reproduce.
Environment
Favorable conditions for the dispersal and consequent infection of white rust from diseased to healthy plants are most common in the autumn and spring seasons. This pathogen prefers cool, moist conditions for the spread and formation of new infections. Conversely, it rarely infects in warm, dry conditions. ''Albugo'' is very temperature sensitive, with the optimal temperature range for infection between . The likelihood of germination and infection is considerably lower if temperatures deviate too far outside this optimum range.[
Light rain or irrigation lasting for extended periods of time is also ideal for disease development. Leaf surfaces need to remain wet for at least 2 to 3 hours to ensure infection by the pathogen. White rust ranges worldwide and is able to survive varying weather conditions due to its production of multiple spore types.][
]
Management
Controlling white rust is very difficult due to the nature of the ''Albugo'' pathogen. The method of control is tailored to specific crops and production systems. This is why identification of specific hosts (crops and possible weeds) is necessary to determine range and location of control methods.
''Albugo'' proliferates in wet and moist conditions so movement through infected fields should be limited after spore maturation in these conditions to limit spread. Minimizing irrigation in cool and moist seasons as well as eliminating windbreak
A windbreak (shelterbelt) is a planting usually made up of one or more rows of trees or shrubs planted in such a manner as to provide shelter from the wind and to protect soil from erosion. They are commonly planted in hedgerows around the edges ...
s to allow faster leaf drying can be beneficial. When infection is recognized, systemically infected plant material (including culled crops) should be completely removed and destroyed. Fields should be inspected every 7–14 days to remove additional material and monitor spread. On root crops, infected leaf removal either by mowing or plowing prior to harvest will limit the spread of the pathogen during harvest. Any susceptible plants or weeds should be mowed or eliminated to reduce spread.[
Both conventional and organic fungicides are available and could be used to limit spread and yield losses during the spring, early summer and fall on crops and susceptible neighboring plants. Each of the 17 specific races of the white rust pathogen affects different plants so monitoring is essential as much as possible to limit overuse and cost of fungicide treatments. Common OMRI fungicides include sulphur, ]copper oxide Copper oxide is a compound from the two elements copper and oxygen.
Copper oxide may refer to:
* Copper(I) oxide (cuprous oxide, Cu2O)
* Copper(II) oxide
Copper(II) oxide or cupric oxide is an inorganic compound with the formula CuO. A black so ...
, rosemary oil
''Salvia rosmarinus'' (), commonly known as rosemary, is a shrub with fragrant, evergreen, needle-like leaves and white, pink, purple, or blue flowers, native to the Mediterranean region. Until 2017, it was known by the scientific name ''Rosmar ...
, and azadirachtin
Azadirachtin, a chemical compound belonging to the limonoid group, is a secondary metabolite present in neem seeds. It is a highly oxidized tetranortriterpenoid which boasts a plethora of oxygen-bearing functional groups, including an enol ether, ...
products. Common conventional fungicides include mefenoxam
Metalaxyl is an acylalanine fungicide with systemic function. Its chemical name is methyl N-(methoxyacetyl)-N-(2,6-xylyl)-DL-alaninate. It can be used to control ''Pythium'' in a number of vegetable crops, and ''Phytophthora'' in peas. Metalaxy ...
and fosetyl-aluminum products.
There are some resistant and partially resistant varieties which are necessary in landscapes where white rust is present. Long-term white rust persistence in fields is not an issue with all crops or in all states; however, non-susceptible crop rotation in infected fields for at least three years is widely recommended to limit establishment and wider dispersal of this pathogen from plant debris, soil, and perennial root material. This pathogen can eliminate viable production of susceptible crops in specific fields indefinitely if infection is widespread over many years.[
]
Importance
White rust can be a devastating disease on many important agricultural crops throughout the world. Seventeen races of white rust have been identified worldwide, each with a high level of host specificity. White rust is an economically important foliar disease, causing substantial yield losses and eventual death of various crops. Yield losses of up to 20 percent have been recorded in canola fields, and white rust is considered the most important foliar disease of Brassicaceae
Brassicaceae () or (the older) Cruciferae () is a medium-sized and economically important family of flowering plants commonly known as the mustards, the crucifers, or the cabbage family. Most are herbaceous plants, while some are shrubs. The leav ...
species in Australia
Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
.
See also
* Plant pathology
Plant pathology (also phytopathology) is the scientific study of diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Organisms that cause infectious disease include fungi, oomy ...
References
External links
Albuginaceae and other families of plant parasitic oomycetes, taxonomy partly outdated
"White Rusts of Vegetables"
(pathology), University of Illinois
Pest and Pathogen Management Database
{{Taxonbar, from=Q4749920
Water mould genera
Albuginaceae