Dead or alive? A new test to determine viability of soybean rust spores

Dec 11, 2012

Spores from Asian soybean rust (Phakopsora pachyrhizi) pose a serious threat to soybean production in the United States because they can be blown great distances by the wind. University of Illinois researchers have developed a method to determine whether these spores are viable.

"Finding is different from finding spores that are living and able to infect plants," said USDA Agricultural Research Service (ARS) scientist and professor Glen Hartman.

Soybean rust, which first appeared in Japan at the beginning of the 20th century, is a foliar infector that reduces plant photosynthetic activity and causes defoliation, , and high yield loss. An obligate pathogen, it grows only on plants and dies when the plant dies or is harvested.

The fungus first appeared In the U.S. in 2004. It is concentrated in the southern states where it is able to overwinter on kudzu. Spraying with is the only way to control it because resistant soybean cultivars are not yet available to U.S. farmers.

To monitor the spread of the disease, researchers established a network of sentinel plots in 2005 (see http://sbr.ipmpipe.org/cgi-bin/sbr/public.cgi). Traps in these plots capture airborne spores and can serve as an for farmers. However, spores that travel are often not viable. There have been many instances where spores have been found in the traps, but rust has not appeared in the fields.

Up to now, because farmers have had no way to determine if the captured spores are dead or alive, they have been faced with a dilemma. They know that spraying too little or too late can lead to yield loss, so they may decide to spray immediately. This raises their costs, damages , and poses risks to human health and the environment. Spraying can also accelerate the development of fungicide-.

"In 2005, there were some farms in the Midwest and the north-central area that were sprayed with fungicide because the word was out that somebody found some spores," Hartman said.

Hartman, Ramya Vittal, a postdoctoral researcher in the Laboratory for Soybean Disease Research, and James Haudenshield, a USDA-ARS research plant pathologist, have just developed a method that uses two different staining techniques to determine spore viability.

The first technique uses two dyes: carboxyfluorescein diacetate (CFDA) and propidium iodide (PI). Viable spores stain green with CFDA; non-viable spores counterstain red with PI.

The second technique uses a two-color fluorescent viability probe that causes cylindrical vacuolar structures to form within living spores, which then fluoresce red. Non-viable spores show only faint fluorescence.

Hartman said that these tests are rapid and reliable. Early detection coupled with timely fungicide application can help slow the pathogen's spread and minimize yield losses.

The next step is to integrate this method with passive spore sampling to develop a tool to detect and monitor the movement of viable P. pachyrhizi spores during the soybean growing season.

Explore further: Call for alternative identification methods for endangered species

More information: The article, "A Multiplexed Immunofluorescence Method Identifies Phakopsora pachyrhizi Urediniospores and Determines Their Viability" by R. Vittal, J. S. Haudenshield, and G. L. Hartman has been published in Phytopathology and is available at: apsjournals.apsnet.org/doi/pdfplus/10.1094/PHYTO-02-12-0040-R

add to favorites email to friend print save as pdf

Related Stories

No Signs of Soybean Rust Found in Virginia

Jul 17, 2006

Asian soybean rust has not been detected in Virginia this year, according to Erik Stromberg, professor and Extension plant pathologist in the College of Agriculture and Life Sciences at Virginia Tech. However, soybean rust ...

Uncovering the mystery of a major threat to wheat

Jun 01, 2010

Agricultural Research Service (ARS) scientists have solved a longstanding mystery as to why a pathogen that threatens the world's wheat supply can be so adaptable, diverse and virulent. It is because the fungus that causes ...

New and old threats to soybean production

Jun 23, 2011

University of Illinois researchers identified the top pathogens, pests and weeds affecting soybean production in a recent article in Food Security. Soybean aphid, soybean rust, soybean cyst nematode, Sclerotina stem rot an ...

Soybean rust PIPE: Past, present and future

Sep 08, 2011

A new, open-access article in the Journal of Integrated Pest Management describes the origin, function, successes, limitations, and future of the Soybean Rust Pest Information Platform for Extension and Education (PIPE).

Recommended for you

India's ancient mammals survived multiple pressures

17 hours ago

Most of the mammals that lived in India 200,000 years ago still roam the subcontinent today, in spite of two ice ages, a volcanic super-eruption and the arrival of people, a study reveals.

User comments : 0

More news stories

Deadly human pathogen Cryptococcus fully sequenced

Within each strand of DNA lies the blueprint for building an organism, along with the keys to its evolution and survival. These genetic instructions can give valuable insight into why pathogens like Cryptococcus ne ...

Biologists help solve fungi mysteries

(Phys.org) —A new genetic analysis revealing the previously unknown biodiversity and distribution of thousands of fungi in North America might also reveal a previously underappreciated contributor to climate ...

Better thermal-imaging lens from waste sulfur

Sulfur left over from refining fossil fuels can be transformed into cheap, lightweight, plastic lenses for infrared devices, including night-vision goggles, a University of Arizona-led international team ...

Hackathon team's GoogolPlex gives Siri extra powers

(Phys.org) —Four freshmen at the University of Pennsylvania have taken Apple's personal assistant Siri to behave as a graduate-level executive assistant which, when asked, is capable of adjusting the temperature ...

Chronic inflammation linked to 'high-grade' prostate cancer

Men who show signs of chronic inflammation in non-cancerous prostate tissue may have nearly twice the risk of actually having prostate cancer than those with no inflammation, according to results of a new study led by researchers ...