Featured Research

from universities, journals, and other organizations

Sexual reproduction only second choice for powdery mildew

Date:
July 14, 2013
Source:
University of Zurich
Summary:
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 demonstrate. Nonetheless, the fungus still allows itself a sexual reproduction cycle.

This shows powdery mildew on young wheat plants.
Credit: UZH

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 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.


Story Source:

The above story is based on materials provided by University of Zurich. Note: Materials may be edited for content and length.


Journal References:

  1. Thomas Wicker, Simone Oberhaensli, Francis Parlange, Jan P Buchmann, Margarita Shatalina, Stefan Roffler, Roi Ben-David, Jaroslav Doležel, Hana Šimková, Paul Schulze-Lefert, Pietro D Spanu, Rémy Bruggmann, Joelle Amselem, Hadi Quesneville, Emiel Ver Loren van Themaat, Timothy Paape, Kentaro K Shimizu, Beat Keller. The wheat powdery mildew genome shows the unique evolution of an obligate biotroph. Nature Genetics, 2013; DOI: 10.1038/ng.2704
  2. S. Hacquard, B. Kracher, T. Maekawa, S. Vernaldi, P. Schulze-Lefert, E. Ver Loren van Themaat. Mosaic genome structure of the barley powdery mildew pathogen and conservation of transcriptional programs in divergent hosts. Proceedings of the National Academy of Sciences, 2013; 110 (24): E2219 DOI: 10.1073/pnas.1306807110

Cite This Page:

University of Zurich. "Sexual reproduction only second choice for powdery mildew." ScienceDaily. ScienceDaily, 14 July 2013. <www.sciencedaily.com/releases/2013/07/130714160607.htm>.
University of Zurich. (2013, July 14). Sexual reproduction only second choice for powdery mildew. ScienceDaily. Retrieved July 29, 2014 from www.sciencedaily.com/releases/2013/07/130714160607.htm
University of Zurich. "Sexual reproduction only second choice for powdery mildew." ScienceDaily. www.sciencedaily.com/releases/2013/07/130714160607.htm (accessed July 29, 2014).

Share This




More Plants & Animals News

Tuesday, July 29, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Deadly Ebola Virus Threatens West Africa

Deadly Ebola Virus Threatens West Africa

AP (July 28, 2014) — West African nations and international health organizations are working to contain the largest Ebola outbreak in history. It's one of the deadliest diseases known to man, but the CDC says it's unlikely to spread in the U.S. (July 28) Video provided by AP
Powered by NewsLook.com
Traditional African Dishes Teach Healthy Eating

Traditional African Dishes Teach Healthy Eating

AP (July 28, 2014) — Classes are being offered nationwide to encourage African Americans to learn about cooking fresh foods based on traditional African cuisine. The program is trying to combat obesity, heart disease and other ailments often linked to diet. (July 28) Video provided by AP
Powered by NewsLook.com
Asteroid's Timing Was 'Colossal Bad Luck' For The Dinosaurs

Asteroid's Timing Was 'Colossal Bad Luck' For The Dinosaurs

Newsy (July 28, 2014) — The asteroid that killed the dinosaurs struck at the worst time for them. A new study says that if it hit earlier or later, they might've survived. Video provided by Newsy
Powered by NewsLook.com
Raw: Sea Turtle Hatchlings Emerge from Nest

Raw: Sea Turtle Hatchlings Emerge from Nest

AP (July 27, 2014) — A live-streaming webcam catches loggerhead sea turtle hatchlings emerging from a nest in the Florida Keys. (July 27) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins