Black grain rust

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Black grain rust
Black rust (Puccinia graminis) on wheat

Black rust ( Puccinia graminis ) on wheat

Systematics
Subdivision : Pucciniomycotina
Class : Pucciniomycetes
Order : Rust mushrooms (Pucciniales)
Family : Pucciniaceae
Genre : Puccinia
Type : Black grain rust
Scientific name
Puccinia graminis
Persoon

The stem rust ( Puccinia graminis ), black rust or cereal rust is a fungus from the family of the rust fungi (Pucciniales). It is known for infecting wheat , barley , oats and rye , and other sweet grasses also belong to its range of hosts. Grain black rust is heterozygous, which means that it changes host between the grain and the barberry family as a secondary host .

Grain black rust occurs in numerous varieties and forms. In the first half of the 20th century, grain black rust was nearly eliminated in the United States by extensive barberry eradication. In East Africa, the Ug99 breed, which was discovered in 1998 and has also been resistant to cultivars, led to major crop failures in wheat. This form has been detected in Sicily since 2015 , the FAO warns of spreading in the Mediterranean region.

features

Aecidia of the fungus on the underside of a barberry leaf

Macroscopic properties

The grain black rust initially appears as a rust-red coating ( uredia ) on grasses. It stretches as a strip along the longitudinal axis, mainly on stems, less strongly on leaves. Over time, the affected areas grow and turn black ( Telien ).

On barberries ( Berberis ) and Mahonia ( Mahonia ), the infestation is shown by round, yellow spots ( pycnidia ) on the upper side of the leaves. Five to seven days later, larger, light yellow spots, the so-called aecidia, appear on the underside of the leaves .

Grain black rust teleutospores

Microscopic properties

The urediospores of the barley black rust are oval and measure 25–30 × 17–20 µm. They each contain four germ spores. The teleutospores are dark brown, consist of two cells with two nuclei each and are rounded at the top. They measure 40–60 × 15–20 µm and have a relatively thick and smooth outer wall, as well as germ pores at the apex and slightly below the septum.

ecology

Life cycle of black rust, here using the example of wheat and barberry

The grain black rust goes through five vegetative stations during its development cycle, three of which take place on the primary host, i.e. soft wheat ( Triticum aestivum ), and the remaining two on the secondary host , for example barberry ( Berberis vulgaris ).

First, in spring, the haploid basidiospores of the fungus germinate on the leaves of the barberry and form a single-seeded haploid mycelium there. The fungus now feeds parasitically on the barberry and forms different structures on the leaf sides. Under the epidermis of the upper side of the leaf, pycnidia (or spermogonia) develop , which form the sex nuclei. Aecidia forms on the underside of the leaf that form basal cells. These take up the genital nuclei formed by the pycnidia.

Pycnidia ( sp ) and aecidia ( ae ) using the example of the barberry leaf

They receive a further nucleus from pycnospores, which get to the receptive hyphae by flying spores or being transported by insects. From there the spore migrates to the nuclear cell, completing the formation of a heterokaryon . The aecidium is formed from this basal cell and produces a large number of acidiospores.

Aecidia on the barberry

These haploid - dikaryotic acidiospores can only germinate on sweet grasses. They form a germ tube on the wheat, which penetrates the plant tissue and grows there intercellularly. The mycelium remains localized and does not have buckles , but it is seeded in pairs.

These structures, called uridia, now form asexual uredospores . Although the fungus cannot reproduce sexually with these, they do enable it to spread on a large scale, so that not only other parts of the host plant but also numerous other plants can be attacked.

Finally, in autumn, teleutospores form from the uridia. With their thick cell wall, these are designed for wintering. They have two pairs of kernels that eventually fuse in spring and then form basidia . These in turn form basidiospores, which means that the cycle is completed once.

Systematics

Since agriculture has reacted to the black rust of grain over the course of time with more and more new breeds, but the fungus developed resistance through mutation and specialized in individual types of grass, numerous forms and varieties of black rust have emerged:

  • Puccinia graminis f. agropyri P.R. Mehta & R. Prasad (1948)
  • Puccinia graminis f. avenae Erikss. & Henning
  • Puccinia graminis f. graminis pers. (1794)
  • Puccinia graminis f. maroccana Unamuno (1940)
  • Puccinia graminis f. tritici Erikss. & Henning
  • Puccinia graminis f. tritici-compacti Stakman & Piem.
  • Puccinia graminis f.sp. oryzae Gonz. Ask
  • Puccinia graminis f.sp. poae Erikss. & Henning
  • Puccinia graminis subsp. graminicola Z. Urb. (1967)
  • Puccinia graminis subsp. lolii W.L. Waterh. (1951)
  • Puccinia graminis subsp. media A.L. Guyot, Massenot & Saccas (1946)
  • Puccinia graminis subsp. minor A.L. Guyot, Massenot & Saccas (1946)
  • Puccinia graminis var. Agropyri-repentis A.L. Guyot
  • Puccinia graminis var. Avenae Erikss. & Henning
  • Puccinia graminis var. Brevicarpa Peck (1873)
  • Puccinia graminis var. Calamagrostidis A.L. Guyot, Massenot & Saccas (1946)
  • Puccinia graminis var. Caulium Alb. & Pig. (1805)
  • Puccinia graminis var. Elymi A.L. Guyot, Massenot & Saccas (1946)
  • Puccinia graminis var. Erikssoni A.L. Guyot, Massenot & Saccas (1946)
  • Puccinia graminis var. Hordei Erikss. & Henning
  • Puccinia graminis var. Junci Alb. & Pig. (1805)
  • Puccinia graminis var. Lolii A.L. Guyot, Massenot & Saccas (1946)
  • Puccinia graminis var. Secalis Erikss. & Henning
  • Puccinia graminis var. Simplex grains.
  • Puccinia graminis var. Stakmanii A.L. Guyot, Massenot & Saccas (1946)
  • Puccinia graminis var. Vulpiae A.L. Guyot, Massenot & Saccas (1946)

Agricultural damage

When Puccina graminis fungal spores land on wheat plants, they form pustules and extract nutrients that are intended for grain development.

In the course of history, black rust from grain has repeatedly caused major damage to wheat, rye and barley stocks, as depending on the variety, it led to the loss of a large part of the harvest. Already Pliny the Elder saw the largest Getreidepest in stem rust. It was not until the 18th century that the connection between the proximity of barberries and grain fields and the occurrence of the disease was recognized, whereupon the French grain farmers, for example, demanded the extermination of the barberry. Since the mushroom itself was not yet known at the time, the farmers were accused of superstition by the jam cookers who processed the fruits of the barberry. In 1755, the crown colony of Massachusetts passed a law that gave farmers an ultimatum: on whose land barberries grew, they had to uproot or destroy them by June 13, 1760. It was not until 1794 that the fungus was described by Christian Hendrik Persoon ; In 1866, Anton de Bary provided scientific evidence for the role of the barberry as an intermediate host.

Johann Wolfgang von Goethe notes in his diary on June 29, 1816, which he describes as the “first beautiful day”, in addition to flooding of the Saale in the Jena area, also: “Rust of grain”. Its spread in Thuringia was apparently favored by the rainfalls in the " year without a summer ", which had lasted since mid-May 1816 at the latest.

After two major epidemics emerged in the United States in the early 20th century, the Department of Agriculture coordinated a program to eradicate barberry in key wheat-growing areas (particularly Ohio to North Dakota ). In 1933, 18 million bushes were eliminated. Other states joined the program over time. Around 1930 the epidemics began to decline. A new variant of the fungus caused the last devastating epidemics to date in 1953 and 1954. A quarantine program still exists today, according to which the transport of barberries to or between quarantined countries is prohibited. The widespread elimination of barberry has severely restricted the possibilities for genetic recombination and thus the risk of the formation of new, more virulent variants, which is why black rust has been a much smaller problem in the United States since then.

In the 1960s, Norman Borlaug and colleagues at CIMMYT bred wheat lines that contained resistance genes such as Sr31 . Another threat was the Ug99 breed, discovered in Uganda in 1998 , to which Sr31 does not confer resistance. Ug99 now exists in seven variants and around 2007 caused major damage to Kenyan farmers (in some cases yield drops of up to 80%). From East Africa, the tribe has also spread to Yemen and Iran . In March 2008, the FAO warned of massive crop failures after Ug99 was detected there. The main problem is the high susceptibility of many types of wheat that are not resistant to Ug99 . The food supply of hundreds of millions of people is at risk if the fungus migrates further east.

When Borlaug heard about the reappearance of black rust in 2005, he called scientists together in the project "Durable Rust Resistance in Wheat", which is led by Cornell University and CIMMYT. There are now 20 resistant varieties available, which are now being integrated into breeding programs in eight African and Asian nations.

The FAO reports that the fungus has spread again. FAO expert David Hodson warned: "The appearance of the Ug99 breed in East Africa turned wheat rust from a disease that was largely under control into a major global threat." Microbiologist Ralf T. Vögele, professor of phytopathology and dean of the faculty Agricultural science from the University of Hohenheim in Stuttgart said Ug99 had overcome all resistance genes that are built into wheat worldwide.

The new breed has been detected in Sicily since 2015, and in 2016 it already attacked tens of thousands of hectares of wheat fields. In early 2017, the FAO issued a warning for the entire Mediterranean region.

Military use

At the end of the 1940s there were efforts in the USA to use black rust for military purposes. In 1953 the bomb M-115 was developed, which contained a 250-kg load of spores of the fungus together with turkey feathers as carriers and was intended to cause crop failures by military opponents. The United States military produced black rust spores for this purpose in Fort Detrick until 1957 , and from 1962 to 1969. These supplies were not completely destroyed until 1974 as part of a demilitarization program.

Sources and References

literature

  • Peter H. Raven, Ray F. Evert, Susan E. Eichhorn, Rosemarie Langenfeld-Heyser: Biology of Plants. Walter de Gruyter, 2000. ISBN 3-11-015462-5 , pp. 352-353.
  • SM Reddy: University Botany: Algae, Fungi, Bryophyta and Pteridophyta. New Age International, 1996. ISBN 81-224-0840-0 , pp. 176-184.
  • OP Sharma: Textbook of Fungi. Tata McGraw-Hill, 1989. ISBN 0-07-460329-9 , pp. 222-234.
  • Ravi P. Singh et al. a .: Current status, likely migration and strategies to mitigate the threat to wheat production from race Ug99 (TTKS) of stem rust pathogen. ( PDF )

Web links

Commons : Grain Black Rust ( Puccinia graminis )  - Collection of images, videos and audio files

Individual evidence

  1. ↑ a b c O. P. Sharma: Textbook of Fungi. Tata McGraw-Hill, 1989. ISBN 0-07-460329-9 , pp. 222-234.
  2. ^ Index Fungorum. Retrieved March 2, 2010.
  3. ↑ a b c Gayathri Vaidyanathan (2011): Science in Africa: The wheat stalker. Nature 474, pp. 563-565. (PDF; 2.0 MB)
  4. ↑ Peter H. Raven, Ray F. Evert, Susan E. Eichhorn, Rosemarie Langenfeld-Heyser: Biology of Plants. Walter de Gruyter, 2000. ISBN 3-11-015462-5 , pp. 352-353.
  5. ↑ Zeno: Goethe, Johann Wolfgang, Diaries, 1816, June. Retrieved May 2, 2017 .
  6. ^ Kurt J. Leonard: Black stem rust biology and threat to wheat growers . Agricultural Research Service, USDA, 2001, accessed August 5, 2013
  7. ↑ Dangerous wheat-killing fungus detected in Iran - UN. UN News Center, March 5, 2008. Retrieved March 2, 2010.
  8. ↑ Markus Brauer: Grain rust on the advance , on stuttgarter-zeitung.de from April 13, 2016
  9. ↑ Nature: Deadly new wheat disease threatens Europe's crops , February 2, 2017
  10. ↑ FAO: Spread of damaging wheat rust continues: new races found in Europe, Africa, Central Asia , February 3, 2017
  11. ↑ Mark Wheelis, Lajos Rózsa, Malcolm Dando: Deadly Cultures: Biological Weapons since 1945. Harvard University Press, 2006. ISBN 0-674-01699-8 , S. 218th
  12. ↑ Anthony Rimmington: The Soviet Union's offensive Program: The Implications for Contemporary Arms Control. In: Susan Wright (Ed.): Biological Warfare and Disarmament: New Problems / New Perspectives. Rowman & Littlefield, 2002. ISBN 0-7425-2469-8 , p. 138.
  13. ^ Jefferey K. Smart: History of Chemical and Biological Warfare: An American Perspective. In: Medical Aspects of Chemical and Biological Warfare. , P. 51 ( PDF ).