''Puccinia porri'' (previously known as ''Puccinia allii'') is a species of

rust fungus 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 ...

that causes leek rust. It affects

leek A leek is a vegetable, a cultivar of ''Allium ampeloprasum'', the broadleaf wild leek (synonym (taxonomy), syn. ''Allium porrum''). The edible part of the plant is a bundle of Leaf sheath, leaf sheaths that is sometimes erroneously called a "s ...

garlic Garlic (''Allium sativum'') is a species of bulbous flowering plants in the genus '' Allium''. Its close relatives include the onion, shallot, leek, chives, Welsh onion, and Chinese onion. Garlic is native to central and south Asia, str ...

onion An onion (''Allium cepa'' , from Latin ), also known as the bulb onion or common onion, is a vegetable that is the most widely cultivated species of the genus '' Allium''. The shallot is a botanical variety of the onion which was classifie ...

, and

chives Chives, scientific name ''Allium schoenoprasum'', is a species of flowering plant in the family Amaryllidaceae. A perennial plant, ''A. schoenoprasum'' is widespread in nature across much of Eurasia and North America. It is the only spe ...

, and usually appears as bright orange spots on infected plants.

Fungus

''Puccinia porri'' is

autoecious A heteroecious parasite is one that requires at least two Host (biology), hosts. The ''primary host'' is the host in which the parasite spends its adult life; the other is the ''secondary host''. Both hosts are required for the parasite to compl ...

, meaning that all stages of its life cycle occur on the host plant. While ''P. porri'' and ''P. mixta'' were originally thought to be separate species, by 1984 they were all generally categorized under ''P. allii''. The fungus causes leek rust, but it also affects

, and

. In 2016, Alistair McTaggart and colleagues used

molecular phylogenetic Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...

analysis to sort out collections of fungi labeled as ''Puccinia allii'' occurring in Australia, and placed this name in

synonymy A synonym is a word, morpheme, or phrase that means precisely or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are a ...

with ''Puccinia porri''.

Conditions for growth

Leek rust appears seasonally, starting in the middle of August. It develops more quickly in warmer weather, so conversely, cold spells can reduce the onset of symptoms. If a leek reaches maturation closer to winter, it is more susceptible to infection, whereas a leek that matures earlier in the fall must be wet to endure a heavy attack. According to the

Royal Horticultural Society The Royal Horticultural Society (RHS), founded in 1804 as the Horticultural Society of London, is the UK's leading gardening charity. The RHS promotes horticulture through its five gardens at Wisley (Surrey), Hyde Hall (Essex), Harlow Carr ...

, there are no

fungicide Fungicides are pesticides used to kill parasitic fungi or their spores. Fungi can cause serious damage in agriculture, resulting in losses of yield and quality. Fungicides are used both in agriculture and to fight fungal infections in animals, ...

s approved for use by amateur gardeners to combat leek rust. However, in practice there are different fungicides that are recommended for use in different countries, depending on the ''Allium'' crop. For example, in Ethiopia, the fungicides

mancozeb Mancozeb is a dithiocarbamate non-systemic agricultural fungicide with multi-site, protective action on contact. It is a combination of two other dithiocarbamates: maneb and zineb. The mixture controls many fungal diseases in a wide range of fi ...

propiconazole Propiconazole is a triazole fungicide, also known as a DMI, or demethylation inhibiting fungicide due to its binding with and inhibiting the Lanosterol 14 alpha-demethylase, 14-alpha demethylase enzyme from demethylating a precursor to ergosterol. ...

tebuconazole Tebuconazole is a triazole fungicide used agriculturally to treat plant pathogenic fungi. Environmental hazards Though the U.S. Food and Drug Administration considers this fungicide to be safe for humans, it may still pose a risk. It is listed as ...

azoxystrobin Azoxystrobin is a broad spectrum systemic fungicide widely used in agriculture to protect crops from fungal diseases. It was first marketed in 1996 using the brand name Amistar and by 1999 it had been registered in 48 countries on more than 50 cr ...

are approved for use to control the fungus. They will control the rust if sprayed on the plant at 10-day intervals.

Symptoms of infection

On leeks, ''P. porri'' manifests as bright orange or yellow pustules on the upper parts of the leaves, usually between veins. Sometimes, the pustules grow to network with each other and spread to the base of the leaf. The aeciospores are between 19 and 28

micrometer Micrometer can mean: * Micrometer (device), used for accurate measurements by means of a calibrated screw * Micrometre The micrometre (English in the Commonwealth of Nations, Commonwealth English as used by the International Bureau of Weights ...

s in diameter, with yellow walls 1 to 2 micrometers in length. The

urediniospores Urediniospores (or uredospores) are thin-walled spores produced by the uredium, a stage in the life-cycle of rusts. Development ''Urediniospores'' develop in the uredium, generally on a leaf's under surface. Morphology *Urediniospores usually ...

are more elliptical in shape, with a major axis diameter of 22–32 micrometers and a minor axis diameter of 20–26 micrometers. The

teliospores Teliospore (sometimes called teleutospore) is the thick-walled resting spore of some fungi ( rusts and smuts), from which the basidium arises. Development They develop in '' telia'' (sing. ''telium'' or ''teliosorus''). The telial host is the p ...

are also elliptical, with a major axis diameter of 28–45 micrometers and a minor axis diameter of 20–26 micrometers.

Economic damage

An infected leek's discolouring can cause it to lose market value, as there is an expectation the vegetables do not have visual defects or flaws. The infection can also slow and reduce the growth of the plant. In addition, Uma (1984) writes that ''P. porri'' has caused significant losses for garlic farmers in

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

, Israel, South Africa, and Brazil.

References

{{Taxonbar, from=Q1422236

porri Porri () is a Communes of France, commune in the Haute-Corse Departments of France, department of France on the island of Corsica. Population See also *Communes of the Haute-Corse department References

Communes of Haute-Corse ...

Fungi described in 1809 Fungal plant pathogens and diseases Fungi of Africa Fungi of North America Fungi of South America Taxa named by James Sowerby Fungus species