Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Sexual reproduction only second choice for powdery mildew

15.07.2013
Genetically, powdery mildew is perfectly adapted to its host plants. Evidently, sexual reproduction and new combinations of genetic material usually prove disadvantageous for the fungus.

Asexual reproduction, however, is considerably more successful for mildew, as plant biologists from the University of Zurich and the Max Planck Institute for Plant Breeding Research in Cologne demonstrate. Nonetheless, the fungus still allows itself a sexual reproduction cycle.


Powdery mildew on young wheat plants.
Picture: UZH

Powdery mildew is one of the most dreaded plant diseases: The parasitic fungus afflicts crops such as wheat and barley and is responsible for large harvest shortfalls every year. Beat Keller and Thomas Wicker, both plant biologists from the University of Zurich, and their team have been analyzing the genetic material of wheat mildew varieties from Switzerland, England and Israel while the team headed by Paul Schulze-Lefert at the Max Planck Institute for Plant Breeding Research in Cologne studies the genetic material of barley mildew.

The results recently published in Nature Genetics and PNAS respectively unveil a long shared history of co-evolution between the host and the pest and the unexpected success of asexually produced mildew offspring. Moreover, the data provides fresh insights into the crop history of wheat and barley and their interaction with the mildew pathogen.

Asexually produced offspring more successful
Like other fungi, mildew reproduces in two ways: Sexually, where the genetic material is recombined, and asexually, where the offspring and the mother fungus are genetically identical. The researchers now demonstrate that the success of the two reproduction methods could not be more different: “Mildew fungi detected on afflicted host plants have only successfully reproduced sexually every few centuries, primarily reproducing asexually instead,” explains Wicker.

This baffling fact has more deep-rooted causes: In order to infect the host plant, the mildew fungus needs to be able to successfully disable the plant’s defense mechanisms – the parasite has to be perfectly adapted to its host. “In a parasite-host situation, new combinations of genetic material are a disadvantage for the parasite as the adaptation to the host and its defense mechanisms deteriorates as a result.” Genetically identical offspring of successful mildew fungi that have already been able to infect the host plant, however, have the ideal genetic prerequisites to be able to attack a host themselves. According to Schulze-Lefert, wheat and barley mildew offspring from asexual reproduction are normally more successful than their sexually reproduced counterparts. Asexual reproduction as a success model seems to be characteristic of many parasitic fungi, including those that afflict humans, such as athlete’s foot.

Sex still worthwhile
Based on the gene analyses, the scientists were also able to prove that mildew already lived parasitically on the ancestral form of wheat 10,000 years ago, before wheat were actually domesticated as crops. None of the subsequent genetic changes in the crops due to breeding or spontaneous mutations was ever able to keep the mildew fungus away from wheat in the longer term. And this is precisely where the advantage of sexual reproduction lies and why the usually unsuccessful sexual reproduction cycle is still worthwhile for the mildew fungus: Wheat and mildew are embroiled in a permanent evolutionary arms race. “If wheat improves its defense mechanisms against the parasites, the fungus has to be able to follow suit or it has lost,” explains Wicker. “That’s only possible by recombining the genetic material; in other words, sexual reproduction.”

Evidently, a sexual exchange and mixtures of the genetic material of different mildew varieties have occurred several times in the course of the millennia, giving rise to new mildew varieties that were able to attack new sorts of wheat. The scientists suspect that the grain trade in the ancient world was partly responsible for the emergence of new mildew varieties.

Literature:
Thomas Wicker et al. The wheat powdery mildew genome shows the unique evolution of an obligate biotroph. Nature Genetics. July 14, 2013. doi:10.1038/ng.2704

Stéphane Hacquard et al. Mosaic genome structure of the barley powdery mildew pathogen and conservation of transcriptional programs in divergent hosts. PNAS. May 21, 2013. doi/10.1073/pnas130607110

Contact:
Wheat mildew:
Prof. Dr. Beat Keller
Institute of Plant Biology
University of Zurich
Tel. +41 44 634 82 30
E-Mail: bkeller@botinst.uzh.ch
Nathalie Huber
Media Relations
University of Zurich
Tel. +41 44 634 44 64
E-Mail: nathalie.huber@kommunikation.uzh.ch
Barley mildew:
Prof. Dr. Paul Schulze-Lefert
Max Planck Institute for Plant Breeding Research
50829 Cologne
Germany
Tel. +49 221 5062 350
E-Mail: schlef@mpiz-koeln.mpg.de

Nathalie Huber | Universität Zürich
Further information:
http://www.uzh.ch

More articles from Life Sciences:

nachricht One step closer to reality
20.04.2018 | Max-Planck-Institut für Entwicklungsbiologie

nachricht The dark side of cichlid fish: from cannibal to caregiver
20.04.2018 | Veterinärmedizinische Universität Wien

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Spider silk key to new bone-fixing composite

University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.

Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...

Im Focus: Basel researchers succeed in cultivating cartilage from stem cells

Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.

Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...

Im Focus: Like a wedge in a hinge

Researchers lay groundwork to tailor drugs for new targets in cancer therapy

In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

Magnetic nano-imaging on a table top

20.04.2018 | Physics and Astronomy

Start of work for the world's largest electric truck

20.04.2018 | Interdisciplinary Research

Atoms may hum a tune from grand cosmic symphony

20.04.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>